FlightGear wiki - User contributions [en]

Zeppelin LZ 121 Nordstern

2025-11-06T17:56:43Z

AndersG: /* Visible crew */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* {{Key press|Shift|1}} - Select the port side engine (engine 0).
* {{Key press|Shift|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valves of the fore gas cells.
* {{Key press|G}}/{{Key press|g}} - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|e}}/{{Key press|d}} - Shift trim ballast fore/aft.
* {{Key press|E}}/{{Key press|D}} - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* {{Key press|Ctrl|W}} - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

=== Visible crew ===

If you have visible crew members you can change the properties ''crew/elevatorman/visible'', ''crew/helmsman/visible'', ''crew/watch-officer-view/visible'' ''crew/steward-view/visible'' and ''crew/rigger-view/visible'' to ''false'' or ''0'' to hide their 3d model. To show them again you set the ''visible'' property to ''true'' or ''1''.

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin LZ 121 Nordstern

2025-11-06T17:55:46Z

AndersG: /* Visible crew */ Added this section.

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* {{Key press|Shift|1}} - Select the port side engine (engine 0).
* {{Key press|Shift|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valves of the fore gas cells.
* {{Key press|G}}/{{Key press|g}} - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|e}}/{{Key press|d}} - Shift trim ballast fore/aft.
* {{Key press|E}}/{{Key press|D}} - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* {{Key press|Ctrl|W}} - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

=== Visible crew ===

If you have visible crew members you can change the properties ''crew/elevatorman/visible'', ''crew/helmsman/visible'', ''crew/watch-officer-view/visible'' ''crew/steward-view/visible'' and ''crew/rigger-view/visible'' to ''false'' or ''0'' to hide their 3d model. To show it again you set the ''visible'' property to ''true'' or ''1''.

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin NT

2025-11-03T15:52:56Z

AndersG: /* Engine start */

{{:{{PAGENAME}}/info}}

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder since the real NT has a side stick.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engines and thrust vectoring ===

The Zeppelin NT has a non-standard set of engine controls. The engines' throttles are controlled by govenors - the throttle levers select the desired RPM.

'''Engine controls'''
* RPM select levers ({{Key press|PgUp}}/{{Key press|PgDown}}) - Increase/decrease selected engine RPM.
* Mixture levers ({{Key press|M}}/{{Key press|m}}) - Leaner/richer mixture.

'''Thrust vectoring'''
* Side engine swivel ({{Key press|[}}/{{Key press|]}}) - Swivel side engines up/down. 0 - 120 degrees.
* Aft engine swivel ({{Key press|G}}/{{Key press|g}}) - Swivel aft engine down/up. -90/0 degrees.
* Thrust levers ({{Key press|N}}/{{Key press|n}}) - Decrease/increase thrust (i.e. propeller blade angle).

The levers in the cockpit can also be controlled via the mouse pointer, either by clicking on a lever (left mouse button increases / middle mouse button decreases) or pointing at it and rotating the scroll wheel.

[[File:Zeppelin_NT_center_console.jpg|thumb|600px|center|The engine and propeller controls on the center console.]]

=== Gas and Envelope ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|Q}}/{{Key press|q}} - Inflate/deflate fore ballonet.
* {{Key press|A}}/{{Key press|a}} - Inflate/deflate aft ballonet.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge!

==== Pitch trim ====
On the Zeppelin NT pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
Take off and Landing
Maximum Forward 1344.5 in
Maximum Aft 1374.0 in
In Flight
Maximum Forward 1315.0 in
Maximum Aft 1374.0 in

=== Ballast ===

The Zeppelin NT has no ballast approved for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 700lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|D}}/{{Key press|d}} - Drop ballast in 1%/0.1% decrements.

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land slightly short of the mast and taxi up to it under precision control. Use the rear thruster to keep the tail wheel in the air while taxing. The Zeppelin NT is very maneuverable and can land with great precision. The Road & Track Magazine wrote this about the real one "can ... almost land on a dime (Jim Dexter actually tried this, and missed by the length of a dollar bill)". Achieving that (or any) kind of precision is by no means easy, though.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using Zeppelin NT to dock with your mast.

[[File:Zeppelin_NT_landing.jpg|thumb|600px|center|Approaching the mooring mast for landing.]]

'''Note:''' The mooring force calculations are sensitive to long frame times (i.e. very low fps). In particular this can cause instability during FlightGear startup. One workaround is to pause the simulation immediately on startup and continue when scenery objects and multiplayers have been loaded. A better option is to reduce /sim/max-simtime-per-frame to a sane number, e.g. 0.1 meaning that each frame is at most 0.1 simulated seconds (so if your fps drops below 10 the simulation will run slower than real-time).
This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== Cockpit and instruments ==

[[File:Zeppelin_NT_cockpit.jpg|thumb|800px|center|The cockpit of the Zeppelin NT.]]

=== Visible crew ===

If you have visible crew members you can change the properties ''crew/pilot-view/visible'', ''crew/copilot-view/visible'' and ''crew/passenger-view/visible'' to ''false'' or ''0'' to hide them.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the certificate of airworthiness and have no connection whatsoever to any instructions for the real Zeppelin NT.

=== At all times ===
* Maintain envelope pressure above 1.2 inH2O (300 Pa; 6.3 psf)

=== Engine start ===
* Mixture rich
* Low RPM ({{Key press|PgDn}})
* Thrust levers set for propeller blade angle close to 0
* Magnetos set to both ({{Key press|} }} {{Key press|} }})
* Run starter as required ({{Key press|s}})

=== Pre-take off ===
* Weigh off ({{Key press|W}})
* Make sure the center of gravity is within the take off range (See "Pitch trim" above and the aircraft help.)
* Swivel engines as needed (usually side engines to 80 - 90 degrees up and aft engine 90 degrees down)
* Thrust levers set for propeller blade angle close to 0
* Max RPM selected

=== Take off ===
* Raise the tail using the thrust lever for the aft engine
* Rotate around the mast using rudder until the nose points straight into the wind
* Increase thrust on the side engines
* Release from the mooring mast ({{Key press|Y}})
* Control the aircraft's attitude and climb with the side and aft engine thrust levers
* Transit to forward flight by gradually swivel the side engines down
* Don't return the aft engine to 0 degrees too soon.

=== Cruise ===

* Mixture rich of peak EGT
* Thrust levers set to max thrust/blade angle
* Use engine RPM select for thrust control
* Pitch trim for level flight as needed by moving the center of gravity (within the legal limits) (See "Pitch trim" above and the aircraft help.) (It usually needs to move forward quite a bit)

=== Approach ===
* Make sure the center of gravity is within the landing range (See "Pitch trim" above and the aircraft help.)
* Mixture rich
* Max RPM selected
* Engine swivel as needed (usually side 90 degrees up, aft 90 degrees down)
* Use thrust levers for thrust control
* Approach the mast straight into the wind

=== Landing ===
* Land and hold just short of the mast
* Connect the mooring wire ({{Key press|U}} + {{Key press|u}})
* Slowly taxi towards the mast assisted by the winch until contact is made.

== Multiplayer dual control ==

This aircraft is equipped for [[Dual control]] over the FlightGear multiplayer network.

To use this feature the pilot and copilot select each other in their Co/Pilot selection dialogs available from the "Zeppelin NT"->"MP-(Co)Pilot" menu.

Alternatively the pilot sets the property /sim/remote/pilot-callsign to the callsign of the prospective copilot. This property can be set in the property browser, on the [[command line]] or in fgrun. Command line example:
fgfs --aircraft=ZLT-NT --prop:/sim/remote/pilot-callsign="someone"

The copilot uses the copilot "aircraft" ZLT-NT-copilot and sets the property /sim/remote/pilot-callsign to the callsign of the pilot. Command line example:
fgfs --aircraft=ZLT-NT-copilot --prop:/sim/remote/pilot-callsign="anybody"

'''Note:'''

1. The Co/Pilot dialog is only available in FlightGear 2.0.0 or later and might still have some flaws. Switching between different copilots might sometimes cause problems.
It is usually enough if the copilot restarts her/his FlightGear instance or moves far away and then back using the location menu in these cases.

2. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should preferably join MP ''after'' the pilot set /sim/remote/pilot-callsign or things might not work correctly. This doesn't seem to be an issue in FlightGear 2.0.0 or later.

3. Using the ZLT-NT-copilot it is possible to hitch a ride with any ZLT-NT on MP. However, unless you are the pilot "approved" copilot you will only be an observer (and will not, if there is no approved copilot, receive the full aircraft state from the pilot).

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

* The mooring force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* The engines sometimes behave oddly, in particular in landing configuration (high RPM and varying blade angles). The engine sound is also too loud and a bit strange as well. Work in progress.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin NT is available [http://github.com/andgi/FlightGear-ZLT-NT here] for FlightGear/git.'''

* A user drivable Scania mast truck add-on is included in the GitHub repository but not in FGAddon.

* [http://www.gidenstam.org/FlightGear/DualControl/ More on multiplayer dual control].

{{Aerostat}}

Zeppelin NT

2025-11-03T15:51:42Z

AndersG: /* Handling instructions */ Improved the key presses.

{{:{{PAGENAME}}/info}}

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder since the real NT has a side stick.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engines and thrust vectoring ===

The Zeppelin NT has a non-standard set of engine controls. The engines' throttles are controlled by govenors - the throttle levers select the desired RPM.

'''Engine controls'''
* RPM select levers ({{Key press|PgUp}}/{{Key press|PgDown}}) - Increase/decrease selected engine RPM.
* Mixture levers ({{Key press|M}}/{{Key press|m}}) - Leaner/richer mixture.

'''Thrust vectoring'''
* Side engine swivel ({{Key press|[}}/{{Key press|]}}) - Swivel side engines up/down. 0 - 120 degrees.
* Aft engine swivel ({{Key press|G}}/{{Key press|g}}) - Swivel aft engine down/up. -90/0 degrees.
* Thrust levers ({{Key press|N}}/{{Key press|n}}) - Decrease/increase thrust (i.e. propeller blade angle).

The levers in the cockpit can also be controlled via the mouse pointer, either by clicking on a lever (left mouse button increases / middle mouse button decreases) or pointing at it and rotating the scroll wheel.

[[File:Zeppelin_NT_center_console.jpg|thumb|600px|center|The engine and propeller controls on the center console.]]

=== Gas and Envelope ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|Q}}/{{Key press|q}} - Inflate/deflate fore ballonet.
* {{Key press|A}}/{{Key press|a}} - Inflate/deflate aft ballonet.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge!

==== Pitch trim ====
On the Zeppelin NT pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
Take off and Landing
Maximum Forward 1344.5 in
Maximum Aft 1374.0 in
In Flight
Maximum Forward 1315.0 in
Maximum Aft 1374.0 in

=== Ballast ===

The Zeppelin NT has no ballast approved for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 700lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|D}}/{{Key press|d}} - Drop ballast in 1%/0.1% decrements.

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land slightly short of the mast and taxi up to it under precision control. Use the rear thruster to keep the tail wheel in the air while taxing. The Zeppelin NT is very maneuverable and can land with great precision. The Road & Track Magazine wrote this about the real one "can ... almost land on a dime (Jim Dexter actually tried this, and missed by the length of a dollar bill)". Achieving that (or any) kind of precision is by no means easy, though.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using Zeppelin NT to dock with your mast.

[[File:Zeppelin_NT_landing.jpg|thumb|600px|center|Approaching the mooring mast for landing.]]

'''Note:''' The mooring force calculations are sensitive to long frame times (i.e. very low fps). In particular this can cause instability during FlightGear startup. One workaround is to pause the simulation immediately on startup and continue when scenery objects and multiplayers have been loaded. A better option is to reduce /sim/max-simtime-per-frame to a sane number, e.g. 0.1 meaning that each frame is at most 0.1 simulated seconds (so if your fps drops below 10 the simulation will run slower than real-time).
This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== Cockpit and instruments ==

[[File:Zeppelin_NT_cockpit.jpg|thumb|800px|center|The cockpit of the Zeppelin NT.]]

=== Visible crew ===

If you have visible crew members you can change the properties ''crew/pilot-view/visible'', ''crew/copilot-view/visible'' and ''crew/passenger-view/visible'' to ''false'' or ''0'' to hide them.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the certificate of airworthiness and have no connection whatsoever to any instructions for the real Zeppelin NT.

=== At all times ===
* Maintain envelope pressure above 1.2 inH2O (300 Pa; 6.3 psf)

=== Engine start ===
* Mixture rich
* Low RPM ({{Key press|PgDn}})
* Thrust levers set for propeller blade angle close to 0
* Magnetos set to both ({{Key press|}}} {{Key press|R}}}})
* Run starter as required ({{Key press|s}})

=== Pre-take off ===
* Weigh off ({{Key press|W}})
* Make sure the center of gravity is within the take off range (See "Pitch trim" above and the aircraft help.)
* Swivel engines as needed (usually side engines to 80 - 90 degrees up and aft engine 90 degrees down)
* Thrust levers set for propeller blade angle close to 0
* Max RPM selected

=== Take off ===
* Raise the tail using the thrust lever for the aft engine
* Rotate around the mast using rudder until the nose points straight into the wind
* Increase thrust on the side engines
* Release from the mooring mast ({{Key press|Y}})
* Control the aircraft's attitude and climb with the side and aft engine thrust levers
* Transit to forward flight by gradually swivel the side engines down
* Don't return the aft engine to 0 degrees too soon.

=== Cruise ===

* Mixture rich of peak EGT
* Thrust levers set to max thrust/blade angle
* Use engine RPM select for thrust control
* Pitch trim for level flight as needed by moving the center of gravity (within the legal limits) (See "Pitch trim" above and the aircraft help.) (It usually needs to move forward quite a bit)

=== Approach ===
* Make sure the center of gravity is within the landing range (See "Pitch trim" above and the aircraft help.)
* Mixture rich
* Max RPM selected
* Engine swivel as needed (usually side 90 degrees up, aft 90 degrees down)
* Use thrust levers for thrust control
* Approach the mast straight into the wind

=== Landing ===
* Land and hold just short of the mast
* Connect the mooring wire ({{Key press|U}} + {{Key press|u}})
* Slowly taxi towards the mast assisted by the winch until contact is made.

== Multiplayer dual control ==

This aircraft is equipped for [[Dual control]] over the FlightGear multiplayer network.

To use this feature the pilot and copilot select each other in their Co/Pilot selection dialogs available from the "Zeppelin NT"->"MP-(Co)Pilot" menu.

Alternatively the pilot sets the property /sim/remote/pilot-callsign to the callsign of the prospective copilot. This property can be set in the property browser, on the [[command line]] or in fgrun. Command line example:
fgfs --aircraft=ZLT-NT --prop:/sim/remote/pilot-callsign="someone"

The copilot uses the copilot "aircraft" ZLT-NT-copilot and sets the property /sim/remote/pilot-callsign to the callsign of the pilot. Command line example:
fgfs --aircraft=ZLT-NT-copilot --prop:/sim/remote/pilot-callsign="anybody"

'''Note:'''

1. The Co/Pilot dialog is only available in FlightGear 2.0.0 or later and might still have some flaws. Switching between different copilots might sometimes cause problems.
It is usually enough if the copilot restarts her/his FlightGear instance or moves far away and then back using the location menu in these cases.

2. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should preferably join MP ''after'' the pilot set /sim/remote/pilot-callsign or things might not work correctly. This doesn't seem to be an issue in FlightGear 2.0.0 or later.

3. Using the ZLT-NT-copilot it is possible to hitch a ride with any ZLT-NT on MP. However, unless you are the pilot "approved" copilot you will only be an observer (and will not, if there is no approved copilot, receive the full aircraft state from the pilot).

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

* The mooring force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* The engines sometimes behave oddly, in particular in landing configuration (high RPM and varying blade angles). The engine sound is also too loud and a bit strange as well. Work in progress.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin NT is available [http://github.com/andgi/FlightGear-ZLT-NT here] for FlightGear/git.'''

* A user drivable Scania mast truck add-on is included in the GitHub repository but not in FGAddon.

* [http://www.gidenstam.org/FlightGear/DualControl/ More on multiplayer dual control].

{{Aerostat}}

Zeppelin NT

2025-11-03T15:07:01Z

AndersG: /* Cockpit and instruments */ Visible crew members in the current version.

{{:{{PAGENAME}}/info}}

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder since the real NT has a side stick.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engines and thrust vectoring ===

The Zeppelin NT has a non-standard set of engine controls. The engines' throttles are controlled by govenors - the throttle levers select the desired RPM.

'''Engine controls'''
* RPM select levers ({{Key press|PgUp}}/{{Key press|PgDown}}) - Increase/decrease selected engine RPM.
* Mixture levers ({{Key press|M}}/{{Key press|m}}) - Leaner/richer mixture.

'''Thrust vectoring'''
* Side engine swivel ({{Key press|[}}/{{Key press|]}}) - Swivel side engines up/down. 0 - 120 degrees.
* Aft engine swivel ({{Key press|G}}/{{Key press|g}}) - Swivel aft engine down/up. -90/0 degrees.
* Thrust levers ({{Key press|N}}/{{Key press|n}}) - Decrease/increase thrust (i.e. propeller blade angle).

The levers in the cockpit can also be controlled via the mouse pointer, either by clicking on a lever (left mouse button increases / middle mouse button decreases) or pointing at it and rotating the scroll wheel.

[[File:Zeppelin_NT_center_console.jpg|thumb|600px|center|The engine and propeller controls on the center console.]]

=== Gas and Envelope ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|Q}}/{{Key press|q}} - Inflate/deflate fore ballonet.
* {{Key press|A}}/{{Key press|a}} - Inflate/deflate aft ballonet.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge!

==== Pitch trim ====
On the Zeppelin NT pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
Take off and Landing
Maximum Forward 1344.5 in
Maximum Aft 1374.0 in
In Flight
Maximum Forward 1315.0 in
Maximum Aft 1374.0 in

=== Ballast ===

The Zeppelin NT has no ballast approved for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 700lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|D}}/{{Key press|d}} - Drop ballast in 1%/0.1% decrements.

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land slightly short of the mast and taxi up to it under precision control. Use the rear thruster to keep the tail wheel in the air while taxing. The Zeppelin NT is very maneuverable and can land with great precision. The Road & Track Magazine wrote this about the real one "can ... almost land on a dime (Jim Dexter actually tried this, and missed by the length of a dollar bill)". Achieving that (or any) kind of precision is by no means easy, though.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using Zeppelin NT to dock with your mast.

[[File:Zeppelin_NT_landing.jpg|thumb|600px|center|Approaching the mooring mast for landing.]]

'''Note:''' The mooring force calculations are sensitive to long frame times (i.e. very low fps). In particular this can cause instability during FlightGear startup. One workaround is to pause the simulation immediately on startup and continue when scenery objects and multiplayers have been loaded. A better option is to reduce /sim/max-simtime-per-frame to a sane number, e.g. 0.1 meaning that each frame is at most 0.1 simulated seconds (so if your fps drops below 10 the simulation will run slower than real-time).
This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== Cockpit and instruments ==

[[File:Zeppelin_NT_cockpit.jpg|thumb|800px|center|The cockpit of the Zeppelin NT.]]

=== Visible crew ===

If you have visible crew members you can change the properties ''crew/pilot-view/visible'', ''crew/copilot-view/visible'' and ''crew/passenger-view/visible'' to ''false'' or ''0'' to hide them.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the certificate of airworthiness and have no connection whatsoever to any instructions for the real Zeppelin NT.

=== At all times ===
* Maintain envelope pressure above 1.2 inH2O (300 Pa; 6.3 psf)

=== Engine start ===
* Mixture rich
* Low RPM (PgDn)
* Thrust levers set for propeller blade angle close to 0
* Magnetos set to both (} } })
* Run starter as required (s)

=== Pre-take off ===
* Weigh off (W)
* Make sure the center of gravity is within the take off range (See "Pitch trim" above and the aircraft help.)
* Swivel engines as needed (usually side engines to 80 - 90 degrees up and aft engine 90 degrees down)
* Thrust levers set for propeller blade angle close to 0
* Max RPM selected

=== Take off ===
* Raise the tail using the thrust lever for the aft engine
* Rotate around the mast using rudder until the nose points straight into the wind
* Increase thrust on the side engines
* Release from the mooring mast (Y)
* Control the aircraft's attitude and climb with the side and aft engine thrust levers
* Transit to forward flight by gradually swivel the side engines down
* Don't return the aft engine to 0 degrees too soon.

=== Cruise ===

* Mixture rich of peak EGT
* Thrust levers set to max thrust/blade angle
* Use engine RPM select for thrust control
* Pitch trim for level flight as needed by moving the center of gravity (within the legal limits) (See "Pitch trim" above and the aircraft help.) (It usually needs to move forward quite a bit)

=== Approach ===
* Make sure the center of gravity is within the landing range (See "Pitch trim" above and the aircraft help.)
* Mixture rich
* Max RPM selected
* Engine swivel as needed (usually side 90 degrees up, aft 90 degrees down)
* Use thrust levers for thrust control
* Approach the mast straight into the wind

=== Landing ===
* Land and hold just short of the mast
* Connect the mooring wire (U + u)
* Slowly taxi towards the mast assisted by the winch until contact is made.

== Multiplayer dual control ==

This aircraft is equipped for [[Dual control]] over the FlightGear multiplayer network.

To use this feature the pilot and copilot select each other in their Co/Pilot selection dialogs available from the "Zeppelin NT"->"MP-(Co)Pilot" menu.

Alternatively the pilot sets the property /sim/remote/pilot-callsign to the callsign of the prospective copilot. This property can be set in the property browser, on the [[command line]] or in fgrun. Command line example:
fgfs --aircraft=ZLT-NT --prop:/sim/remote/pilot-callsign="someone"

The copilot uses the copilot "aircraft" ZLT-NT-copilot and sets the property /sim/remote/pilot-callsign to the callsign of the pilot. Command line example:
fgfs --aircraft=ZLT-NT-copilot --prop:/sim/remote/pilot-callsign="anybody"

'''Note:'''

1. The Co/Pilot dialog is only available in FlightGear 2.0.0 or later and might still have some flaws. Switching between different copilots might sometimes cause problems.
It is usually enough if the copilot restarts her/his FlightGear instance or moves far away and then back using the location menu in these cases.

2. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should preferably join MP ''after'' the pilot set /sim/remote/pilot-callsign or things might not work correctly. This doesn't seem to be an issue in FlightGear 2.0.0 or later.

3. Using the ZLT-NT-copilot it is possible to hitch a ride with any ZLT-NT on MP. However, unless you are the pilot "approved" copilot you will only be an observer (and will not, if there is no approved copilot, receive the full aircraft state from the pilot).

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

* The mooring force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* The engines sometimes behave oddly, in particular in landing configuration (high RPM and varying blade angles). The engine sound is also too loud and a bit strange as well. Work in progress.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin NT is available [http://github.com/andgi/FlightGear-ZLT-NT here] for FlightGear/git.'''

* A user drivable Scania mast truck add-on is included in the GitHub repository but not in FGAddon.

* [http://www.gidenstam.org/FlightGear/DualControl/ More on multiplayer dual control].

{{Aerostat}}

Zeppelin NT

2025-11-03T14:57:36Z

AndersG: /* Ground crew / Mooring mast */

{{:{{PAGENAME}}/info}}

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder since the real NT has a side stick.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engines and thrust vectoring ===

The Zeppelin NT has a non-standard set of engine controls. The engines' throttles are controlled by govenors - the throttle levers select the desired RPM.

'''Engine controls'''
* RPM select levers ({{Key press|PgUp}}/{{Key press|PgDown}}) - Increase/decrease selected engine RPM.
* Mixture levers ({{Key press|M}}/{{Key press|m}}) - Leaner/richer mixture.

'''Thrust vectoring'''
* Side engine swivel ({{Key press|[}}/{{Key press|]}}) - Swivel side engines up/down. 0 - 120 degrees.
* Aft engine swivel ({{Key press|G}}/{{Key press|g}}) - Swivel aft engine down/up. -90/0 degrees.
* Thrust levers ({{Key press|N}}/{{Key press|n}}) - Decrease/increase thrust (i.e. propeller blade angle).

The levers in the cockpit can also be controlled via the mouse pointer, either by clicking on a lever (left mouse button increases / middle mouse button decreases) or pointing at it and rotating the scroll wheel.

[[File:Zeppelin_NT_center_console.jpg|thumb|600px|center|The engine and propeller controls on the center console.]]

=== Gas and Envelope ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|Q}}/{{Key press|q}} - Inflate/deflate fore ballonet.
* {{Key press|A}}/{{Key press|a}} - Inflate/deflate aft ballonet.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge!

==== Pitch trim ====
On the Zeppelin NT pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
Take off and Landing
Maximum Forward 1344.5 in
Maximum Aft 1374.0 in
In Flight
Maximum Forward 1315.0 in
Maximum Aft 1374.0 in

=== Ballast ===

The Zeppelin NT has no ballast approved for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 700lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|D}}/{{Key press|d}} - Drop ballast in 1%/0.1% decrements.

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land slightly short of the mast and taxi up to it under precision control. Use the rear thruster to keep the tail wheel in the air while taxing. The Zeppelin NT is very maneuverable and can land with great precision. The Road & Track Magazine wrote this about the real one "can ... almost land on a dime (Jim Dexter actually tried this, and missed by the length of a dollar bill)". Achieving that (or any) kind of precision is by no means easy, though.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using Zeppelin NT to dock with your mast.

[[File:Zeppelin_NT_landing.jpg|thumb|600px|center|Approaching the mooring mast for landing.]]

'''Note:''' The mooring force calculations are sensitive to long frame times (i.e. very low fps). In particular this can cause instability during FlightGear startup. One workaround is to pause the simulation immediately on startup and continue when scenery objects and multiplayers have been loaded. A better option is to reduce /sim/max-simtime-per-frame to a sane number, e.g. 0.1 meaning that each frame is at most 0.1 simulated seconds (so if your fps drops below 10 the simulation will run slower than real-time).
This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== Cockpit and instruments ==

[[File:Zeppelin_NT_cockpit.jpg|thumb|800px|center|The cockpit of the Zeppelin NT.]]

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the certificate of airworthiness and have no connection whatsoever to any instructions for the real Zeppelin NT.

=== At all times ===
* Maintain envelope pressure above 1.2 inH2O (300 Pa; 6.3 psf)

=== Engine start ===
* Mixture rich
* Low RPM (PgDn)
* Thrust levers set for propeller blade angle close to 0
* Magnetos set to both (} } })
* Run starter as required (s)

=== Pre-take off ===
* Weigh off (W)
* Make sure the center of gravity is within the take off range (See "Pitch trim" above and the aircraft help.)
* Swivel engines as needed (usually side engines to 80 - 90 degrees up and aft engine 90 degrees down)
* Thrust levers set for propeller blade angle close to 0
* Max RPM selected

=== Take off ===
* Raise the tail using the thrust lever for the aft engine
* Rotate around the mast using rudder until the nose points straight into the wind
* Increase thrust on the side engines
* Release from the mooring mast (Y)
* Control the aircraft's attitude and climb with the side and aft engine thrust levers
* Transit to forward flight by gradually swivel the side engines down
* Don't return the aft engine to 0 degrees too soon.

=== Cruise ===

* Mixture rich of peak EGT
* Thrust levers set to max thrust/blade angle
* Use engine RPM select for thrust control
* Pitch trim for level flight as needed by moving the center of gravity (within the legal limits) (See "Pitch trim" above and the aircraft help.) (It usually needs to move forward quite a bit)

=== Approach ===
* Make sure the center of gravity is within the landing range (See "Pitch trim" above and the aircraft help.)
* Mixture rich
* Max RPM selected
* Engine swivel as needed (usually side 90 degrees up, aft 90 degrees down)
* Use thrust levers for thrust control
* Approach the mast straight into the wind

=== Landing ===
* Land and hold just short of the mast
* Connect the mooring wire (U + u)
* Slowly taxi towards the mast assisted by the winch until contact is made.

== Multiplayer dual control ==

This aircraft is equipped for [[Dual control]] over the FlightGear multiplayer network.

To use this feature the pilot and copilot select each other in their Co/Pilot selection dialogs available from the "Zeppelin NT"->"MP-(Co)Pilot" menu.

Alternatively the pilot sets the property /sim/remote/pilot-callsign to the callsign of the prospective copilot. This property can be set in the property browser, on the [[command line]] or in fgrun. Command line example:
fgfs --aircraft=ZLT-NT --prop:/sim/remote/pilot-callsign="someone"

The copilot uses the copilot "aircraft" ZLT-NT-copilot and sets the property /sim/remote/pilot-callsign to the callsign of the pilot. Command line example:
fgfs --aircraft=ZLT-NT-copilot --prop:/sim/remote/pilot-callsign="anybody"

'''Note:'''

1. The Co/Pilot dialog is only available in FlightGear 2.0.0 or later and might still have some flaws. Switching between different copilots might sometimes cause problems.
It is usually enough if the copilot restarts her/his FlightGear instance or moves far away and then back using the location menu in these cases.

2. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should preferably join MP ''after'' the pilot set /sim/remote/pilot-callsign or things might not work correctly. This doesn't seem to be an issue in FlightGear 2.0.0 or later.

3. Using the ZLT-NT-copilot it is possible to hitch a ride with any ZLT-NT on MP. However, unless you are the pilot "approved" copilot you will only be an observer (and will not, if there is no approved copilot, receive the full aircraft state from the pilot).

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

* The mooring force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* The engines sometimes behave oddly, in particular in landing configuration (high RPM and varying blade angles). The engine sound is also too loud and a bit strange as well. Work in progress.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin NT is available [http://github.com/andgi/FlightGear-ZLT-NT here] for FlightGear/git.'''

* A user drivable Scania mast truck add-on is included in the GitHub repository but not in FGAddon.

* [http://www.gidenstam.org/FlightGear/DualControl/ More on multiplayer dual control].

{{Aerostat}}

Zeppelin NT

2025-11-03T14:56:54Z

AndersG: /* Important controls / keys */ Improved the key presses.

{{:{{PAGENAME}}/info}}

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder since the real NT has a side stick.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engines and thrust vectoring ===

The Zeppelin NT has a non-standard set of engine controls. The engines' throttles are controlled by govenors - the throttle levers select the desired RPM.

'''Engine controls'''
* RPM select levers ({{Key press|PgUp}}/{{Key press|PgDown}}) - Increase/decrease selected engine RPM.
* Mixture levers ({{Key press|M}}/{{Key press|m}}) - Leaner/richer mixture.

'''Thrust vectoring'''
* Side engine swivel ({{Key press|[}}/{{Key press|]}}) - Swivel side engines up/down. 0 - 120 degrees.
* Aft engine swivel ({{Key press|G}}/{{Key press|g}}) - Swivel aft engine down/up. -90/0 degrees.
* Thrust levers ({{Key press|N}}/{{Key press|n}}) - Decrease/increase thrust (i.e. propeller blade angle).

The levers in the cockpit can also be controlled via the mouse pointer, either by clicking on a lever (left mouse button increases / middle mouse button decreases) or pointing at it and rotating the scroll wheel.

[[File:Zeppelin_NT_center_console.jpg|thumb|600px|center|The engine and propeller controls on the center console.]]

=== Gas and Envelope ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|Q}}/{{Key press|q}} - Inflate/deflate fore ballonet.
* {{Key press|A}}/{{Key press|a}} - Inflate/deflate aft ballonet.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge!

==== Pitch trim ====
On the Zeppelin NT pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
Take off and Landing
Maximum Forward 1344.5 in
Maximum Aft 1374.0 in
In Flight
Maximum Forward 1315.0 in
Maximum Aft 1374.0 in

=== Ballast ===

The Zeppelin NT has no ballast approved for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 700lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|D}}/{{Key press|d}} - Drop ballast in 1%/0.1% decrements.

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt} + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land slightly short of the mast and taxi up to it under precision control. Use the rear thruster to keep the tail wheel in the air while taxing. The Zeppelin NT is very maneuverable and can land with great precision. The Road & Track Magazine wrote this about the real one "can ... almost land on a dime (Jim Dexter actually tried this, and missed by the length of a dollar bill)". Achieving that (or any) kind of precision is by no means easy, though.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using Zeppelin NT to dock with your mast.

[[File:Zeppelin_NT_landing.jpg|thumb|600px|center|Approaching the mooring mast for landing.]]

'''Note:''' The mooring force calculations are sensitive to long frame times (i.e. very low fps). In particular this can cause instability during FlightGear startup. One workaround is to pause the simulation immediately on startup and continue when scenery objects and multiplayers have been loaded. A better option is to reduce /sim/max-simtime-per-frame to a sane number, e.g. 0.1 meaning that each frame is at most 0.1 simulated seconds (so if your fps drops below 10 the simulation will run slower than real-time).
This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== Cockpit and instruments ==

[[File:Zeppelin_NT_cockpit.jpg|thumb|800px|center|The cockpit of the Zeppelin NT.]]

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the certificate of airworthiness and have no connection whatsoever to any instructions for the real Zeppelin NT.

=== At all times ===
* Maintain envelope pressure above 1.2 inH2O (300 Pa; 6.3 psf)

=== Engine start ===
* Mixture rich
* Low RPM (PgDn)
* Thrust levers set for propeller blade angle close to 0
* Magnetos set to both (} } })
* Run starter as required (s)

=== Pre-take off ===
* Weigh off (W)
* Make sure the center of gravity is within the take off range (See "Pitch trim" above and the aircraft help.)
* Swivel engines as needed (usually side engines to 80 - 90 degrees up and aft engine 90 degrees down)
* Thrust levers set for propeller blade angle close to 0
* Max RPM selected

=== Take off ===
* Raise the tail using the thrust lever for the aft engine
* Rotate around the mast using rudder until the nose points straight into the wind
* Increase thrust on the side engines
* Release from the mooring mast (Y)
* Control the aircraft's attitude and climb with the side and aft engine thrust levers
* Transit to forward flight by gradually swivel the side engines down
* Don't return the aft engine to 0 degrees too soon.

=== Cruise ===

* Mixture rich of peak EGT
* Thrust levers set to max thrust/blade angle
* Use engine RPM select for thrust control
* Pitch trim for level flight as needed by moving the center of gravity (within the legal limits) (See "Pitch trim" above and the aircraft help.) (It usually needs to move forward quite a bit)

=== Approach ===
* Make sure the center of gravity is within the landing range (See "Pitch trim" above and the aircraft help.)
* Mixture rich
* Max RPM selected
* Engine swivel as needed (usually side 90 degrees up, aft 90 degrees down)
* Use thrust levers for thrust control
* Approach the mast straight into the wind

=== Landing ===
* Land and hold just short of the mast
* Connect the mooring wire (U + u)
* Slowly taxi towards the mast assisted by the winch until contact is made.

== Multiplayer dual control ==

This aircraft is equipped for [[Dual control]] over the FlightGear multiplayer network.

To use this feature the pilot and copilot select each other in their Co/Pilot selection dialogs available from the "Zeppelin NT"->"MP-(Co)Pilot" menu.

Alternatively the pilot sets the property /sim/remote/pilot-callsign to the callsign of the prospective copilot. This property can be set in the property browser, on the [[command line]] or in fgrun. Command line example:
fgfs --aircraft=ZLT-NT --prop:/sim/remote/pilot-callsign="someone"

The copilot uses the copilot "aircraft" ZLT-NT-copilot and sets the property /sim/remote/pilot-callsign to the callsign of the pilot. Command line example:
fgfs --aircraft=ZLT-NT-copilot --prop:/sim/remote/pilot-callsign="anybody"

'''Note:'''

1. The Co/Pilot dialog is only available in FlightGear 2.0.0 or later and might still have some flaws. Switching between different copilots might sometimes cause problems.
It is usually enough if the copilot restarts her/his FlightGear instance or moves far away and then back using the location menu in these cases.

2. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should preferably join MP ''after'' the pilot set /sim/remote/pilot-callsign or things might not work correctly. This doesn't seem to be an issue in FlightGear 2.0.0 or later.

3. Using the ZLT-NT-copilot it is possible to hitch a ride with any ZLT-NT on MP. However, unless you are the pilot "approved" copilot you will only be an observer (and will not, if there is no approved copilot, receive the full aircraft state from the pilot).

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

* The mooring force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* The engines sometimes behave oddly, in particular in landing configuration (high RPM and varying blade angles). The engine sound is also too loud and a bit strange as well. Work in progress.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin NT is available [http://github.com/andgi/FlightGear-ZLT-NT here] for FlightGear/git.'''

* A user drivable Scania mast truck add-on is included in the GitHub repository but not in FGAddon.

* [http://www.gidenstam.org/FlightGear/DualControl/ More on multiplayer dual control].

{{Aerostat}}

Zeppelin NT

2025-11-03T14:49:50Z

AndersG: /* Known problems */

{{:{{PAGENAME}}/info}}

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder since the real NT has a side stick.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engines and thrust vectoring ===

The Zeppelin NT has a non-standard set of engine controls. The engines' throttles are controlled by govenors - the throttle levers select the desired RPM.

'''Engine controls'''
* RPM select levers (PgUp/PgDown) - Increase/decrease selected engine RPM.
* Mixture levers (M/m) - Leaner/richer mixture.

'''Thrust vectoring'''
* Side engine swivel ([/]) - Swivel side engines up/down. 0 - 120 degrees.
* Aft engine swivel (G/g) - Swivel aft engine down/up. -90/0 degrees.
* Thrust levers (N/n) - Decrease/increase thrust (i.e. propeller blade angle).

The levers in the cockpit can also be controlled via the mouse pointer, either by clicking on a lever (left mouse button increases / middle mouse button decreases) or pointing at it and rotating the scroll wheel.

[[File:Zeppelin_NT_center_console.jpg|thumb|600px|center|The engine and propeller controls on the center console.]]

=== Gas and Envelope ===

* F/f - Open/close the gas valve.
* Q/q - Inflate/deflate fore ballonet.
* A/a - Inflate/deflate aft ballonet.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. If the envelope pressure drops too low an alarm will sound. Monitor the gas pressure gauge!

==== Pitch trim ====
On the Zeppelin NT pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
Take off and Landing
Maximum Forward 1344.5 in
Maximum Aft 1374.0 in
In Flight
Maximum Forward 1315.0 in
Maximum Aft 1374.0 in

=== Ballast ===

The Zeppelin NT has no ballast approved for inflight adjustment. Use on ground only.

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to 700lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* D/d - Drop ballast in 1%/0.1% decrements.

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land slightly short of the mast and taxi up to it under precision control. Use the rear thruster to keep the tail wheel in the air while taxing. The Zeppelin NT is very maneuverable and can land with great precision. The Road & Track Magazine wrote this about the real one "can ... almost land on a dime (Jim Dexter actually tried this, and missed by the length of a dollar bill)". Achieving that (or any) kind of precision is by no means easy, though.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using Zeppelin NT to dock with your mast.

[[File:Zeppelin_NT_landing.jpg|thumb|600px|center|Approaching the mooring mast for landing.]]

'''Note:''' The mooring force calculations are sensitive to long frame times (i.e. very low fps). In particular this can cause instability during FlightGear startup. One workaround is to pause the simulation immediately on startup and continue when scenery objects and multiplayers have been loaded. A better option is to reduce /sim/max-simtime-per-frame to a sane number, e.g. 0.1 meaning that each frame is at most 0.1 simulated seconds (so if your fps drops below 10 the simulation will run slower than real-time).
This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== Cockpit and instruments ==

[[File:Zeppelin_NT_cockpit.jpg|thumb|800px|center|The cockpit of the Zeppelin NT.]]

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the certificate of airworthiness and have no connection whatsoever to any instructions for the real Zeppelin NT.

=== At all times ===
* Maintain envelope pressure above 1.2 inH2O (300 Pa; 6.3 psf)

=== Engine start ===
* Mixture rich
* Low RPM (PgDn)
* Thrust levers set for propeller blade angle close to 0
* Magnetos set to both (} } })
* Run starter as required (s)

=== Pre-take off ===
* Weigh off (W)
* Make sure the center of gravity is within the take off range (See "Pitch trim" above and the aircraft help.)
* Swivel engines as needed (usually side engines to 80 - 90 degrees up and aft engine 90 degrees down)
* Thrust levers set for propeller blade angle close to 0
* Max RPM selected

=== Take off ===
* Raise the tail using the thrust lever for the aft engine
* Rotate around the mast using rudder until the nose points straight into the wind
* Increase thrust on the side engines
* Release from the mooring mast (Y)
* Control the aircraft's attitude and climb with the side and aft engine thrust levers
* Transit to forward flight by gradually swivel the side engines down
* Don't return the aft engine to 0 degrees too soon.

=== Cruise ===

* Mixture rich of peak EGT
* Thrust levers set to max thrust/blade angle
* Use engine RPM select for thrust control
* Pitch trim for level flight as needed by moving the center of gravity (within the legal limits) (See "Pitch trim" above and the aircraft help.) (It usually needs to move forward quite a bit)

=== Approach ===
* Make sure the center of gravity is within the landing range (See "Pitch trim" above and the aircraft help.)
* Mixture rich
* Max RPM selected
* Engine swivel as needed (usually side 90 degrees up, aft 90 degrees down)
* Use thrust levers for thrust control
* Approach the mast straight into the wind

=== Landing ===
* Land and hold just short of the mast
* Connect the mooring wire (U + u)
* Slowly taxi towards the mast assisted by the winch until contact is made.

== Multiplayer dual control ==

This aircraft is equipped for [[Dual control]] over the FlightGear multiplayer network.

To use this feature the pilot and copilot select each other in their Co/Pilot selection dialogs available from the "Zeppelin NT"->"MP-(Co)Pilot" menu.

Alternatively the pilot sets the property /sim/remote/pilot-callsign to the callsign of the prospective copilot. This property can be set in the property browser, on the [[command line]] or in fgrun. Command line example:
fgfs --aircraft=ZLT-NT --prop:/sim/remote/pilot-callsign="someone"

The copilot uses the copilot "aircraft" ZLT-NT-copilot and sets the property /sim/remote/pilot-callsign to the callsign of the pilot. Command line example:
fgfs --aircraft=ZLT-NT-copilot --prop:/sim/remote/pilot-callsign="anybody"

'''Note:'''

1. The Co/Pilot dialog is only available in FlightGear 2.0.0 or later and might still have some flaws. Switching between different copilots might sometimes cause problems.
It is usually enough if the copilot restarts her/his FlightGear instance or moves far away and then back using the location menu in these cases.

2. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should preferably join MP ''after'' the pilot set /sim/remote/pilot-callsign or things might not work correctly. This doesn't seem to be an issue in FlightGear 2.0.0 or later.

3. Using the ZLT-NT-copilot it is possible to hitch a ride with any ZLT-NT on MP. However, unless you are the pilot "approved" copilot you will only be an observer (and will not, if there is no approved copilot, receive the full aircraft state from the pilot).

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

* The mooring force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* The engines sometimes behave oddly, in particular in landing configuration (high RPM and varying blade angles). The engine sound is also too loud and a bit strange as well. Work in progress.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin NT is available [http://github.com/andgi/FlightGear-ZLT-NT here] for FlightGear/git.'''

* A user drivable Scania mast truck add-on is included in the GitHub repository but not in FGAddon.

* [http://www.gidenstam.org/FlightGear/DualControl/ More on multiplayer dual control].

{{Aerostat}}

Zeppelin LZ 121 Nordstern

2025-10-20T10:55:28Z

AndersG: /* Ground crew / Mooring mast */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* {{Key press|Shift|1}} - Select the port side engine (engine 0).
* {{Key press|Shift|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valves of the fore gas cells.
* {{Key press|G}}/{{Key press|g}} - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|e}}/{{Key press|d}} - Shift trim ballast fore/aft.
* {{Key press|E}}/{{Key press|D}} - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* {{Key press|Ctrl|W}} - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* {{Key press|Alt}} + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Goodyear K-Type Airship

2025-10-20T10:49:19Z

AndersG: /* Engine controls */

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

==== Crew support ====

You can get some support from the crew for the rudder and elevator control which are controlled in the property directories ''/crew/rudder-pilot/'' and ''/crew/elevator-pilot/''.
In each there is an ''enabled'' property (0.0 is off and 1.0 is on) and a control property:
* in the elevator-pilot the property is ''altitude-cmd-ft''; and
* in the rudder-pilot the property is ''heading-magnetic-cmd-deg''.

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle ({{Key press|PgUp}}/{{Key press|PgDn}}) - Increase/decrease engine RPM and power.
* Mixture levers ({{Key press|M}}/{{Key press|m}}) - Leaner/richer mixture.

==== Crew support ====

You can get some support from the crew for the engines which are controlled in the property directory ''/crew/mechanic/''.
There is an ''enabled'' property (0.0 is off and 1.0 is on) and with it 1.0 (ON) the normal throttles give the desired RPM (in 550 - 2250) of the engines.

=== Gas and Envelope ===

* {{Key press|Q}}/{{Key press|q}} - Open/close the damper (air intake) for the fore ballonet.
* {{Key press|Ctrl|Q}} - Open forward ballonet air valve (air outlet). Closes on key release.
* {{Key press|A}}/{{Key press|a}} - Open/close the damper (air intake) for the aft ballonet.
* {{Key press|Ctrl|A}} - Open aft ballonet air valve (air outlet). Closes on key release.
* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|R}} - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

Zeppelin LZ 121 Nordstern

2025-10-10T13:57:40Z

AndersG: /* Ground crew / Mooring mast */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+{{Key press|1}} - Select the port side engine (engine 0).
* Shift+{{Key press|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valves of the fore gas cells.
* {{Key press|G}}/{{Key press|g}} - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|e}}/{{Key press|d}} - Shift trim ballast fore/aft.
* {{Key press|E}}/{{Key press|D}} - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+{{Key press|W}} - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin LZ 121 Nordstern

2025-10-10T13:56:52Z

AndersG: /* Ballast controls */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+{{Key press|1}} - Select the port side engine (engine 0).
* Shift+{{Key press|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valves of the fore gas cells.
* {{Key press|G}}/{{Key press|g}} - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* {{Key press|e}}/{{Key press|d}} - Shift trim ballast fore/aft.
* {{Key press|E}}/{{Key press|D}} - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+{{Key press|W}} - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin LZ 121 Nordstern

2025-10-10T13:55:29Z

AndersG: /* Gas valve controls */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+{{Key press|1}} - Select the port side engine (engine 0).
* Shift+{{Key press|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* {{Key press|F}}/{{Key press|f}} - Open/close the gas valves of the fore gas cells.
* {{Key press|G}}/{{Key press|g}} - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* e/d - Shift trim ballast fore/aft.
* E/D - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+W - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin LZ 121 Nordstern

2025-10-10T13:54:44Z

AndersG: /* Engine controls */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* {{Key press|R}} - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+{{Key press|1}} - Select the port side engine (engine 0).
* Shift+{{Key press|2}} - Select the starboard side engine (engine 1).
* {{Key press|~}} - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* F/f - Open/close the gas valves of the fore gas cells.
* G/g - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* e/d - Shift trim ballast fore/aft.
* E/D - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+W - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Goodyear K-Type Airship

2025-10-10T13:52:53Z

AndersG: /* Gas and Envelope */

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

==== Crew support ====

You can get some support from the crew for the rudder and elevator control which are controlled in the property directories ''/crew/rudder-pilot/'' and ''/crew/elevator-pilot/''.
In each there is an ''enabled'' property (0.0 is off and 1.0 is on) and a control property:
* in the elevator-pilot the property is ''altitude-cmd-ft''; and
* in the rudder-pilot the property is ''heading-magnetic-cmd-deg''.

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle (PgUp/PgDn) - Increase/decrease engine RPM and power.
* Mixture levers (M/m) - Leaner/richer mixture.

==== Crew support ====

You can get some support from the crew for the engines which are controlled in the property directory ''/crew/mechanic/''.
There is an ''enabled'' property (0.0 is off and 1.0 is on) and with it 1.0 (ON) the normal throttles give the desired RPM (in 550 - 2250) of the engines.

=== Gas and Envelope ===

* {{Key press|Q}}/{{Key press|q}} - Open/close the damper (air intake) for the fore ballonet.
* Ctrl+{{Key press|Q}} - Open forward ballonet air valve (air outlet). Closes on key release.
* {{Key press|A}}/{{Key press|a}} - Open/close the damper (air intake) for the aft ballonet.
* Ctrl+{{Key press|A}} - Open aft ballonet air valve (air outlet). Closes on key release.
* {{Key press|F}}/{{Key press|f}} - Open/close the gas valve.
* {{Key press|R}} - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

Goodyear K-Type Airship

2025-10-10T13:51:01Z

AndersG: /* Ballast */

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

==== Crew support ====

You can get some support from the crew for the rudder and elevator control which are controlled in the property directories ''/crew/rudder-pilot/'' and ''/crew/elevator-pilot/''.
In each there is an ''enabled'' property (0.0 is off and 1.0 is on) and a control property:
* in the elevator-pilot the property is ''altitude-cmd-ft''; and
* in the rudder-pilot the property is ''heading-magnetic-cmd-deg''.

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle (PgUp/PgDn) - Increase/decrease engine RPM and power.
* Mixture levers (M/m) - Leaner/richer mixture.

==== Crew support ====

You can get some support from the crew for the engines which are controlled in the property directory ''/crew/mechanic/''.
There is an ''enabled'' property (0.0 is off and 1.0 is on) and with it 1.0 (ON) the normal throttles give the desired RPM (in 550 - 2250) of the engines.

=== Gas and Envelope ===

* Q/q - Open/close the damper (air intake) for the fore ballonet.
* Ctrl+Q - Open forward ballonet air valve (air outlet). Closes on key release.
* A/a - Open/close the damper (air intake) for the aft ballonet.
* Ctrl+A - Open aft ballonet air valve (air outlet). Closes on key release.
* F/f - Open/close the gas valve.
* R - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* {{Key press|w}} - Show current on-ground weight. Only works when on the ground.
* {{Key press|W}} - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

Goodyear K-Type Airship

2025-10-10T13:50:24Z

AndersG: /* Ground crew / Mooring mast */

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

==== Crew support ====

You can get some support from the crew for the rudder and elevator control which are controlled in the property directories ''/crew/rudder-pilot/'' and ''/crew/elevator-pilot/''.
In each there is an ''enabled'' property (0.0 is off and 1.0 is on) and a control property:
* in the elevator-pilot the property is ''altitude-cmd-ft''; and
* in the rudder-pilot the property is ''heading-magnetic-cmd-deg''.

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle (PgUp/PgDn) - Increase/decrease engine RPM and power.
* Mixture levers (M/m) - Leaner/richer mixture.

==== Crew support ====

You can get some support from the crew for the engines which are controlled in the property directory ''/crew/mechanic/''.
There is an ''enabled'' property (0.0 is off and 1.0 is on) and with it 1.0 (ON) the normal throttles give the desired RPM (in 550 - 2250) of the engines.

=== Gas and Envelope ===

* Q/q - Open/close the damper (air intake) for the fore ballonet.
* Ctrl+Q - Open forward ballonet air valve (air outlet). Closes on key release.
* A/a - Open/close the damper (air intake) for the aft ballonet.
* Ctrl+A - Open aft ballonet air valve (air outlet). Closes on key release.
* F/f - Open/close the gas valve.
* R - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* {{Key press|Y}} - Release mooring mast connection or wire.
* {{Key press|U}} - Attach mooring wire. Only possible when close to a mooring mast.
* {{Key press|y}}/{{Key press|u}} - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

Swedish Navy T21 class MTB/info

2025-08-07T12:38:27Z

AndersG:

<includeonly>{{infobox aircraft
| name = Swedish Navy T21 class MTB
| devel-website = {{github url|andgi|FlightGear-MTB_20m}}
| devel-repo = {{github url|andgi|FlightGear-MTB_20m}}
| aircraft = MTB_20m
| image = Swedish_Navy_T21_class_MTB.jpg
| type = Motor torpedo boat
| manufacturer = Baglietto / CRDA / Kockums
| authors = Anders Gidenstam
| fdm = JSBSim
| fgname1 = MTB_20m
| status-fdm = 2
| status-systems = 1
| status-cockpit = 1
| status-model = 1
| download = {{github zip file|andgi|FlightGear-MTB_20m|full=1}}
| licence = GPLv2+
| craft = seacraft
| navbar = 1
}}</includeonly><noinclude>
This is the aircraft infobox subpage of the [[Swedish Navy T21 class MTB]].
[[Category:Aircraft infobox documentation]]
</noinclude>

Zeppelin LZ 121 Nordstern

2025-07-28T10:28:54Z

AndersG: /* Important controls / keys */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* R - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+1 - Select the port side engine (engine 0).
* Shift+2 - Select the starboard side engine (engine 1).
* ~ - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* F/f - Open/close the gas valves of the fore gas cells.
* G/g - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* e/d - Shift trim ballast fore/aft.
* E/D - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+W - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin LZ 121 Nordstern

2025-07-28T10:10:41Z

AndersG: /* Aerodynamic flight controls */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2025.1.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/crew/helmsman/enabled
/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* R - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+1 - Select the port side engine (engine 0).
* Shift+2 - Select the starboard side engine (engine 1).
* ~ - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* F/f - Open/close the gas valves of the fore gas cells.
* G/g - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* e/d - Shift trim ballast fore/aft.
* E/D - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+W - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Zeppelin LZ 121 Nordstern

2025-07-28T10:09:41Z

AndersG: /* Engine controls */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2016.3.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/fdm/jsbsim/crew/helmsman/enabled
/fdm/jsbsim/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/fdm/jsbsim/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* R - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+1 - Select the port side engine (engine 0).
* Shift+2 - Select the starboard side engine (engine 1).
* ~ - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

In the most recent versions (FlightGear release 2024.1.1 and higher) there is a hidden crew "autopilot" system providing virtual engine
men. It can be activated by setting the property

/crew/machinists/enabled

to 1.0. The throttle controls then set the desired RPMs instead of the normal low-level throttle controls.

=== Gas valve controls ===

* F/f - Open/close the gas valves of the fore gas cells.
* G/g - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* e/d - Shift trim ballast fore/aft.
* E/D - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+W - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

User:AndersG

2025-07-02T15:14:38Z

AndersG: Updated the Goodyear K-Type airship with a link to the FGFS wiki page.

{{User
|name = Anders Gidenstam
|location = Sweden
|callsign = SE-AG
|website = http://www.gidenstam.org}}
Spare-time FlightGear developer since early 2006. Currently inactive due to old computer (bought 2008) and, to some extent, children and brain cancer (the last one is bad for a long life but doesn't impact my current time for FlightGear).

Somewhat current projects:

* Adding support for airships and balloons to FlightGear and JSBSim. [http://www.gidenstam.org/FlightGear/Airships/ http://www.gidenstam.org/FlightGear/Airships/] Done and available in JSBSim/git and FlightGear 1.9.0 and later.

* Varios airships, balloons, aeroplanes and helicopters for FlightGear. Work in (various levels of) progress. See also my GitHub repositorys [https://github.com/andgi?tab=repositories https://github.com/andgi?tab=repositories] and my not very often updated web site [http://www.gidenstam.org/FlightGear/Hangar http://www.gidenstam.org/FlightGear/Hangar].
** Colting SA-60 AeroSphere airship. (Not released)
** [http://github.com/andgi/FlightGear-UB_I German type UB I submarine].
** [[Malmö_Flygindustri_MFI-9|MFI-9B light utility aircraft]]. (In FlightGear 2016.1.1 and later)
** Piasecki (Y)H-21 series / Vertol model 42-44 tandem helicopter JSBSim FDM. (Not released)
** RNAS North Sea class airship. (Not released)
** [[Submarine_Scout|RNAS Submarine Scout Zero class airship]]. (In FlightGear 1.9.0 and later)
** SAAB 29 jet fighter. (Not released)
** SCA N1 airship. (Not released)
** [[Short_Empire|Short S.23 Empire flying boat]]. (In FlightGear 2.4.0 and later)
** [[Swedish_Navy_T21_class_MTB|Swedish Navy T21 class motor torpedo boat]].
** The [[Gokstad ship]].
** [http://github.com/andgi/FlightGear-Monitor U.S.S. Monitor].
** [[Zeppelin_LZ_121_Nordstern|Zeppelin LZ 121 Nordstern airship]]. (In FlightGear 2.4.0 and later)
** [http://www.gidenstam.org/FlightGear/Airships#Hindenburg Zeppelin LZ 129 Hindenburg airship]. (Not up to date)
** [[Zeppelin_NT|Zeppelin NT airship]]. (In FlightGear 1.9.0 and later)
** [[ZF_Navy_free_balloon|ZF U.S. Navy free gas balloon]]. (In FlightGear 1.9.0 and later)
** [[Goodyear_K-Type_Airship|U.S. Navy patrol airship]]. ([http://github.com/andgi/FlightGear-ZNP-K My GitHub ZNP-K repository].)

* [[Dual control|Dual control of aircraft over the multiplayer network]]. http://www.gidenstam.org/FlightGear/DualControl/ Available in FlightGear 1.9.0 and later.

* [[Carrier over MP|Multiplayer shared aircraft carrier]]. http://www.gidenstam.org/FlightGear/misc/Carrier_over_MP/ Available in FlightGear 2.0.0 and later.

* [[Wildfire simulation|Multiplayer shared wild fire simulation]]. http://www.gidenstam.org/FlightGear/misc/WildFire/ Available in FlightGear 2.0.0 and later.

* Tools for multiplayer shared state for scenery objects. Available in FlightGear 2.6.0 and later. See Nasal/scenery.nas .

* Experiments with tools for celestial navigation. [http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/ http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/] The RAF mk.9 bubble sextant is available in FlightGear 2.6.0 and later in the Aircraft/Instruments-3d/RAF_Mk9_bubble_sextant/ directory.

Progress on these projects is currently slow but I am working on them.

Completely inactive projects:

* Experiments with dynamic random scenery objects. http://www.gidenstam.org/FlightGear/OceanImprovement (Has been inactive for a long time.)

* Improving the network bandwidth usage efficiency of the FlightGear multiplayer server. http://www.gidenstam.org/FlightGear/fgms/ (Stop-gap solution for year 2009 fgms. Further development inactive.)

* Experiments with head position tracking using a webcam. http://www.gidenstam.org/FlightGear/HeadTracking/ (Has been inactive for a long time.)

[[Category:FlightGear Core developers]]

Goodyear K-Type Airship

2025-07-01T19:48:21Z

AndersG: /* Important controls / keys */

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

==== Crew support ====

You can get some support from the crew for the rudder and elevator control which are controlled in the property directories ''/crew/rudder-pilot/'' and ''/crew/elevator-pilot/''.
In each there is an ''enabled'' property (0.0 is off and 1.0 is on) and a control property:
* in the elevator-pilot the property is ''altitude-cmd-ft''; and
* in the rudder-pilot the property is ''heading-magnetic-cmd-deg''.

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle (PgUp/PgDn) - Increase/decrease engine RPM and power.
* Mixture levers (M/m) - Leaner/richer mixture.

==== Crew support ====

You can get some support from the crew for the engines which are controlled in the property directory ''/crew/mechanic/''.
There is an ''enabled'' property (0.0 is off and 1.0 is on) and with it 1.0 (ON) the normal throttles give the desired RPM (in 550 - 2250) of the engines.

=== Gas and Envelope ===

* Q/q - Open/close the damper (air intake) for the fore ballonet.
* Ctrl+Q - Open forward ballonet air valve (air outlet). Closes on key release.
* A/a - Open/close the damper (air intake) for the aft ballonet.
* Ctrl+A - Open aft ballonet air valve (air outlet). Closes on key release.
* F/f - Open/close the gas valve.
* R - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

Goodyear K-Type Airship

2025-07-01T12:40:24Z

AndersG: /* Important controls / keys */ Added the "auto" crew members.

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

==== Crew support ====

You can get some support from the crew for the rudder and elevator control which are controlled in the property directories ''/crew/rudder-pilot/'' and ''/crew/elevator-pilot/''.
In each there is an ''enabled'' property (0.0 is off and 1.0 is on) and a control property:
* in the elevator-pilot the property is ''altitude-cmd-ft''; and
* in the rudder-pilot the property is ''heading-magnetic-cmd-deg''.

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle (PgUp/PgDn) - Increase/decrease engine RPM and power.
* Mixture levers (M/m) - Leaner/richer mixture.

==== Crew support ====

You can get some support from the crew for the engines which are controlled in the property directory ''/crew/mechanic/''.
There is an ''enabled'' property (0.0 is off and 1.0 is on) and with it 1.0 (ON) the throttles give the desired RPM (in 550 - 2250) of the engines.

=== Gas and Envelope ===

* Q/q - Open/close the damper (air intake) for the fore ballonet.
* Ctrl+Q - Open forward ballonet air valve (air outlet). Closes on key release.
* A/a - Open/close the damper (air intake) for the aft ballonet.
* Ctrl+A - Open aft ballonet air valve (air outlet). Closes on key release.
* F/f - Open/close the gas valve.
* R - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

Goodyear K-Type Airship

2025-06-30T18:45:31Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}

The Goodyear K-Type airship, designated ZNP-K in the US Navy, was the main maritime patrol airship for the US Navy during World War 2. The non-rigid airships (a.k.a. blimps) were 75 to 79 meters long, had a volume of about 404000 to 425000 ft^3 (11500 to 12000 m^3) and were powered by two Pratt & Whitney R-1340 or Curtis-Wright R-975 engines fitted on outriggers on the control car. The prototype was the K-2 which first flew in December 1938. A total of 133 K-Type airships were built during the war, the last, K-135, was delivered in April 1944.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder (Aileron input is also transferred to the rudder for convenience.)
* Elevator (The elevator trim is seldom used see below for pitch trim.)

=== Engine controls ===

The US Navy ZNP-K airship (from K-9 and later) has two Pratt and Whitney R-1340-AN2 radial engines with fixed pitch propellers.

* Throttle (PgUp/PgDn) - Increase/decrease engine RPM and power.
* Mixture levers (M/m) - Leaner/richer mixture.

=== Gas and Envelope ===

* Q/q - Open/close the damper (air intake) for the fore ballonet.
* Ctrl+Q - Open forward ballonet air valve (air outlet). Closes on key release.
* A/a - Open/close the damper (air intake) for the aft ballonet.
* Ctrl+A - Open aft ballonet air valve (air outlet). Closes on key release.
* F/f - Open/close the gas valve.
* R - Pull the rip cord to quickly deflate the envelope. Do NOT use in midair.

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume; and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

==== Envelop pressure management ====
When the airship rises the gas in the envelope expands and consequently the total volume of the ballonets has to decrease or the envelope pressure will increase. There are pressure relief valves that automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty) but the prudent airship pilot would rather use the manual ballonet valves than rely on the relief valves.

When the airship descends the increasing ambient pressure causes the gas in the envelope to contract and to maintain the envelope pressure above the ambient pressure the total volume of the ballonets has to increase. The pilot has to set the ballonet controls for inflation. Monitor the gas pressure gauge!

==== Pitch trim ====
On the US Navy ZNP-K airship pitch trimming is done via the relative inflation of the fore/aft ballonets rather than with the elevator trim. Shifting air between the ballonets moves the center of gravity.

* To trim towards nose heavy - set the fore ballonet valve for inflation and/or the aft for deflation.
* To trim towards tail heavy - set the aft ballonet valve for inflation and/or the fore for deflation.

If the airship is above ''pressure height'', i.e. the altitude where the lifting gas occupies the entire volume of the envelope, the ballonets are empty and cannot be used for pitch trimming (and the simulated airship is likely to go badly out of trim). Ascending above pressure height also result in loss of lifting gas, beware of losing too much or you will be unable to maintain the envelope pressure when descending to the ground again.

'''Center of gravity range'''
FIXME.

=== Ballast ===

The US Navy ZNP-K airship normally carries no ballast for inflight adjustment. Use on ground only.

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to 1000lbs heavy by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.

=== Ground crew / Mooring mast ===

The US Navy ZNP-K airship currently uses the non-period mast truck from the [[Zeppelin NT]]. In actual service either mobile tripod masts towed by tractors or fixed stick masts where used.

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

When landing to a stationary mast (which is the usual case in FlightGear), approach straight into the wind and land short of the mast and taxi up to it under as precise control as possible. The US Navy ZNP-K is not very manoeuvrable at low speed so special care is required. In real life it would land into the hands of a ground handling party and once stationary a mobile mast would be moved up to the nose of the ship and connected to the mooring attachment there.

The mooring mast is visible over the multiplayer network. It is also possible for other pilots using ZNP-K, Zeppelin NT or Nordstern airships to dock with your mast.

== Cockpit and instruments ==

FIXME.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain available documentation and have no connection whatsoever to any instructions for the real ZNP-K airships.

FIXME.

== Installation and Dependencies ==

* US Navy ZNP-K (Development version for [http://github.com/andgi/FlightGear-ZNP-K FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[ZLT-NT]]
* [[Short Empire]]

== Known problems ==

* If the airship is in a sufficiently heavy state when FlightGear starts it might crash at the mast. In particular this may happen at high altitude airports. Initializing with a significantly reduced amount of fuel and payload may help.

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the US Navy ZNP-K airship is available [http://github.com/andgi/FlightGear-ZNP-K here] for FlightGear/git.'''

{{Aerostat}}

User:AndersG

2025-06-07T09:30:43Z

AndersG:

{{User
|name = Anders Gidenstam
|location = Sweden
|callsign = SE-AG
|website = http://www.gidenstam.org}}
Spare-time FlightGear developer since early 2006. Currently inactive due to old computer (bought 2008) and, to some extent, children and brain cancer (the last one is bad for a long life but doesn't impact my current time for FlightGear).

Somewhat current projects:

* Adding support for airships and balloons to FlightGear and JSBSim. [http://www.gidenstam.org/FlightGear/Airships/ http://www.gidenstam.org/FlightGear/Airships/] Done and available in JSBSim/git and FlightGear 1.9.0 and later.

* Varios airships, balloons, aeroplanes and helicopters for FlightGear. Work in (various levels of) progress. See also my GitHub repositorys [https://github.com/andgi?tab=repositories https://github.com/andgi?tab=repositories] and my not very often updated web site [http://www.gidenstam.org/FlightGear/Hangar http://www.gidenstam.org/FlightGear/Hangar].
** Colting SA-60 AeroSphere airship. (Not released)
** [http://github.com/andgi/FlightGear-UB_I German type UB I submarine].
** [[Malmö_Flygindustri_MFI-9|MFI-9B light utility aircraft]]. (In FlightGear 2016.1.1 and later)
** Piasecki (Y)H-21 series / Vertol model 42-44 tandem helicopter JSBSim FDM. (Not released)
** RNAS North Sea class airship. (Not released)
** [[Submarine_Scout|RNAS Submarine Scout Zero class airship]]. (In FlightGear 1.9.0 and later)
** SAAB 29 jet fighter. (Not released)
** SCA N1 airship. (Not released)
** [[Short_Empire|Short S.23 Empire flying boat]]. (In FlightGear 2.4.0 and later)
** [[Swedish_Navy_T21_class_MTB|Swedish Navy T21 class motor torpedo boat]].
** The [[Gokstad ship]].
** [http://github.com/andgi/FlightGear-Monitor U.S.S. Monitor].
** [[Zeppelin_LZ_121_Nordstern|Zeppelin LZ 121 Nordstern airship]]. (In FlightGear 2.4.0 and later)
** [http://www.gidenstam.org/FlightGear/Airships#Hindenburg Zeppelin LZ 129 Hindenburg airship]. (Not up to date)
** [[Zeppelin_NT|Zeppelin NT airship]]. (In FlightGear 1.9.0 and later)
** [[ZF_Navy_free_balloon|ZF U.S. Navy free gas balloon]]. (In FlightGear 1.9.0 and later)
** [http://github.com/andgi/FlightGear-ZNP-K ZNP-K U.S. Navy patrol airship].

* [[Dual control|Dual control of aircraft over the multiplayer network]]. http://www.gidenstam.org/FlightGear/DualControl/ Available in FlightGear 1.9.0 and later.

* [[Carrier over MP|Multiplayer shared aircraft carrier]]. http://www.gidenstam.org/FlightGear/misc/Carrier_over_MP/ Available in FlightGear 2.0.0 and later.

* [[Wildfire simulation|Multiplayer shared wild fire simulation]]. http://www.gidenstam.org/FlightGear/misc/WildFire/ Available in FlightGear 2.0.0 and later.

* Tools for multiplayer shared state for scenery objects. Available in FlightGear 2.6.0 and later. See Nasal/scenery.nas .

* Experiments with tools for celestial navigation. [http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/ http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/] The RAF mk.9 bubble sextant is available in FlightGear 2.6.0 and later in the Aircraft/Instruments-3d/RAF_Mk9_bubble_sextant/ directory.

Progress on these projects is currently slow but I am working on them.

Completely inactive projects:

* Experiments with dynamic random scenery objects. http://www.gidenstam.org/FlightGear/OceanImprovement (Has been inactive for a long time.)

* Improving the network bandwidth usage efficiency of the FlightGear multiplayer server. http://www.gidenstam.org/FlightGear/fgms/ (Stop-gap solution for year 2009 fgms. Further development inactive.)

* Experiments with head position tracking using a webcam. http://www.gidenstam.org/FlightGear/HeadTracking/ (Has been inactive for a long time.)

[[Category:FlightGear Core developers]]

User:AndersG

2025-06-07T09:29:07Z

AndersG:

{{User
|name = Anders Gidenstam
|location = Sweden
|callsign = SE-AG
|website = http://www.gidenstam.org}}
Spare-time FlightGear developer since early 2006. Currently inactive due to old computer (bought 2008) and, to some extent, children and brain cancer (the last one is bad for a long life but doesn't impact my current time for FlightGear).

Somewhat current projects:

* Adding support for airships and balloons to FlightGear and JSBSim. [http://www.gidenstam.org/FlightGear/Airships/ http://www.gidenstam.org/FlightGear/Airships/] Done and available in JSBSim/git and FlightGear 1.9.0 and later.

* Varios airships, balloons, aeroplanes and helicopters for FlightGear. Work in (various levels of) progress. See also my GitHub repositorys [https://github.com/andgi?tab=repositories https://github.com/andgi?tab=repositories] and my not very often web site [http://www.gidenstam.org/FlightGear/Hangar http://www.gidenstam.org/FlightGear/Hangar].
** Colting SA-60 AeroSphere airship. (Not released)
** [http://github.com/andgi/FlightGear-UB_I German type UB I submarine].
** [[Malmö_Flygindustri_MFI-9|MFI-9B light utility aircraft]]. (In FlightGear 2016.1.1 and later)
** Piasecki (Y)H-21 series / Vertol model 42-44 tandem helicopter JSBSim FDM. (Not released)
** RNAS North Sea class airship. (Not released)
** [[Submarine_Scout|RNAS Submarine Scout Zero class airship]]. (In FlightGear 1.9.0 and later)
** SAAB 29 jet fighter. (Not released)
** SCA N1 airship. (Not released)
** [[Short_Empire|Short S.23 Empire flying boat]]. (In FlightGear 2.4.0 and later)
** [[Swedish_Navy_T21_class_MTB|Swedish Navy T21 class motor torpedo boat]].
** The [[Gokstad ship]].
** [http://github.com/andgi/FlightGear-Monitor U.S.S. Monitor].
** [[Zeppelin_LZ_121_Nordstern|Zeppelin LZ 121 Nordstern airship]]. (In FlightGear 2.4.0 and later)
** [http://www.gidenstam.org/FlightGear/Airships#Hindenburg Zeppelin LZ 129 Hindenburg airship]. (Not up to date)
** [[Zeppelin_NT|Zeppelin NT airship]]. (In FlightGear 1.9.0 and later)
** [[ZF_Navy_free_balloon|ZF U.S. Navy free gas balloon]]. (In FlightGear 1.9.0 and later)
** [http://github.com/andgi/FlightGear-ZNP-K ZNP-K U.S. Navy patrol airship].

* [[Dual control|Dual control of aircraft over the multiplayer network]]. http://www.gidenstam.org/FlightGear/DualControl/ Available in FlightGear 1.9.0 and later.

* [[Carrier over MP|Multiplayer shared aircraft carrier]]. http://www.gidenstam.org/FlightGear/misc/Carrier_over_MP/ Available in FlightGear 2.0.0 and later.

* [[Wildfire simulation|Multiplayer shared wild fire simulation]]. http://www.gidenstam.org/FlightGear/misc/WildFire/ Available in FlightGear 2.0.0 and later.

* Tools for multiplayer shared state for scenery objects. Available in FlightGear 2.6.0 and later. See Nasal/scenery.nas .

* Experiments with tools for celestial navigation. [http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/ http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/] The RAF mk.9 bubble sextant is available in FlightGear 2.6.0 and later in the Aircraft/Instruments-3d/RAF_Mk9_bubble_sextant/ directory.

Progress on these projects is currently slow but I am working on them.

Completely inactive projects:

* Experiments with dynamic random scenery objects. http://www.gidenstam.org/FlightGear/OceanImprovement (Has been inactive for a long time.)

* Improving the network bandwidth usage efficiency of the FlightGear multiplayer server. http://www.gidenstam.org/FlightGear/fgms/ (Stop-gap solution for year 2009 fgms. Further development inactive.)

* Experiments with head position tracking using a webcam. http://www.gidenstam.org/FlightGear/HeadTracking/ (Has been inactive for a long time.)

[[Category:FlightGear Core developers]]

User:AndersG

2025-06-07T09:27:35Z

AndersG: Updated some of the information.

{{User
|name = Anders Gidenstam
|location = Sweden
|callsign = SE-AG
|website = http://www.gidenstam.org}}
Spare-time FlightGear developer since early 2006. Currently inactive due to old computer (bought 2008) and, to some extent, children and brain cancer (the last one is bad for a long life but doesn't impact my current time for FlightGear).

Somewhat current projects:

* Adding support for airships and balloons to FlightGear and JSBSim. [http://www.gidenstam.org/FlightGear/Airships/ http://www.gidenstam.org/FlightGear/Airships/] Done and available in JSBSim/git and FlightGear 1.9.0 and later.

* Varios airships, balloons, aeroplanes and helicopters for FlightGear. Work in (various levels of) progress. See also my GitHub repositorys [https://github.com/andgi?tab=repositories https://github.com/andgi?tab=repositories] and my not very often web site [http://www.gidenstam.org/FlightGear/Hangar http://www.gidenstam.org/FlightGear/Hangar].
** Colting SA-60 AeroSphere airship. (Not released)
** [http://github.com/andgi/FlightGear-UB_I German type UB I submarine].
** [[Malmö_Flygindustri_MFI-9|MFI-9B light utility aircraft]]. (In FlightGear 2016.1.1 and later)
** Piasecki (Y)H-21 series / Vertol model 42-44 tandem helicopter JSBSim FDM. (Not released)
** RNAS North Sea class airship. (Not released)
** [[Submarine_Scout|RNAS Submarine Scout Zero class airship]]. (In FlightGear 1.9.0 and later)
** SAAB 29 jet fighter. (Not released)
** SCA N1 airship. (Not released)
** [[Short_Empire|Short S.23 Empire flying boat]]. (In FlightGear 2.4.0 and later)
** [[Swedish_Navy_T21_class_MTB|Swedish Navy T21 class motor torpedo boat]].
** The [[Gokstad ship]].
** [http://github.com/andgi/FlightGear-Monitor U.S.S. Monitor].
** [[Zeppelin_LZ_121_Nordstern|Zeppelin LZ 121 Nordstern airship]]. (In FlightGear 2.4.0 and later)
** [http://www.gidenstam.org/FlightGear/Airships#Hindenburg Zeppelin LZ 129 Hindenburg airship]. (Not up to date)
** [[Zeppelin_NT|Zeppelin NT airship]]. (In FlightGear 1.9.0 and later)
** [[ZF_Navy_free_balloon|ZF U.S. Navy free gas balloon]]. (In FlightGear 1.9.0 and later)
** [http://github.com/andgi/FlightGear-ZNP-K ZNP-K U.S. Navy patrol airship].

* [[Dual control|Dual control of aircraft over the multiplayer network]]. http://www.gidenstam.org/FlightGear/DualControl/ Available in FlightGear 1.9.0 and later.

* [[Carrier over MP|Multiplayer shared aircraft carrier]]. http://www.gidenstam.org/FlightGear/misc/Carrier_over_MP/ Available in FlightGear 2.0.0 and later.

* [[Wildfire simulation|Multiplayer shared wild fire simulation]]. http://www.gidenstam.org/FlightGear/misc/WildFire/ Available in FlightGear 2.0.0 and later.

* Tools for multiplayer shared state for scenery objects. Available in FlightGear 2.6.0 and later. See Nasal/scenery.nas .

* Experiments with tools for celestial navigation. [http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/ http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/] The RAF mk.9 bubble sextant is available in FlightGear 2.6.0 and later in the Aircraft/Instruments-3d/RAF_Mk9_bubble_sextant/ directory.

Progress on these projects is currently slow but I am working on them.

Completely inactive projects
* Experiments with dynamic random scenery objects. http://www.gidenstam.org/FlightGear/OceanImprovement (Has been inactive for a long time.)

* Improving the network bandwidth usage efficiency of the FlightGear multiplayer server. http://www.gidenstam.org/FlightGear/fgms/ (Stop-gap solution for year 2009 fgms. Further development inactive.)

* Experiments with head position tracking using a webcam. http://www.gidenstam.org/FlightGear/HeadTracking/ (Has been inactive for a long time.)

[[Category:FlightGear Core developers]]

User:AndersG

2025-06-07T09:16:43Z

AndersG: Updated the information.

{{User
|name = Anders Gidenstam
|location = Sweden
|callsign = SE-AG
|website = http://www.gidenstam.org}}
Spare-time FlightGear developer since early 2006. Currently inactive due to old computer (bought 2008) and, to some extent, children and brain cancer (the last one is bad for a long life but doesn't impact my current time for FlightGear).

Some what current projects:

* Adding support for airships and balloons to FlightGear and JSBSim. http://www.gidenstam.org/FlightGear/Airships/ Done and available in JSBSim/git and FlightGear 1.9.0 and later.

* Varios airships, balloons, aeroplanes and helicopters for FlightGear. Work in (various levels of) progress. See also http://www.gidenstam.org/FlightGear/Hangar
** Colting SA-60 AeroSphere airship. (Not released)
** [http://github.com/andgi/FlightGear-UB_I German type UB I submarine].
** [[Malmö_Flygindustri_MFI-9|MFI-9B light utility aircraft]]. (In FlightGear 2016.1.1 and later)
** Piasecki (Y)H-21 series / Vertol model 42-44 tandem helicopter JSBSim FDM. (Not released)
** RNAS North Sea class airship. (Not released)
** [[Submarine_Scout|RNAS Submarine Scout Zero class airship]]. (In FlightGear 1.9.0 and later)
** SAAB 29 jet fighter. (Not released)
** SCA N1 airship. (Not released)
** [[Short_Empire|Short S.23 Empire flying boat]]. (In FlightGear 2.4.0 and later)
** [[Swedish_Navy_T21_class_MTB|Swedish Navy T21 class motor torpedo boat]].
** The [[Gokstad ship]].
** [http://github.com/andgi/FlightGear-Monitor U.S.S. Monitor].
** [[Zeppelin_LZ_121_Nordstern|Zeppelin LZ 121 Nordstern airship]]. (In FlightGear 2.4.0 and later)
** [http://www.gidenstam.org/FlightGear/Airships#Hindenburg Zeppelin LZ 129 Hindenburg airship]. (Not up to date)
** [[Zeppelin_NT|Zeppelin NT airship]]. (In FlightGear 1.9.0 and later)
** [[ZF_Navy_free_balloon|ZF U.S. Navy free gas balloon]]. (In FlightGear 1.9.0 and later)
** [http://github.com/andgi/FlightGear-ZNP-K ZNP-K U.S. Navy patrol airship].

* [[Dual control|Dual control of aircraft over the multiplayer network]]. http://www.gidenstam.org/FlightGear/DualControl/ Available in FlightGear 1.9.0 and later.

* [[Carrier over MP|Multiplayer shared aircraft carrier]]. http://www.gidenstam.org/FlightGear/misc/Carrier_over_MP/ Available in FlightGear 2.0.0 and later.

* [[Wildfire simulation|Multiplayer shared wild fire simulation]]. http://www.gidenstam.org/FlightGear/misc/WildFire/ Available in FlightGear 2.0.0 and later.

* Tools for multiplayer shared state for scenery objects. Available in FlightGear 2.6.0 and later. See Nasal/scenery.nas .

* Experiments with tools for celestial navigation. http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/ The RAF mk.9 bubble sextant is available in FlightGear 2.6.0 and later in the Aircraft/Instruments-3d/RAF_Mk9_bubble_sextant/ directory.

* Experiments with dynamic random scenery objects. http://www.gidenstam.org/FlightGear/OceanImprovement (Has been inactive for a long time.)

* Improving the network bandwidth usage efficiency of the FlightGear multiplayer server. http://www.gidenstam.org/FlightGear/fgms/ (Stop-gap solution for year 2009 fgms. Further development inactive.)

* Experiments with head position tracking using a webcam. http://www.gidenstam.org/FlightGear/HeadTracking/ (Has been inactive for a long time.)

Progress on these projects is currently slow but I am working on them.

[[Category:FlightGear Core developers]]

ZF Navy free balloon

2025-06-07T09:09:21Z

AndersG: /* Dependencies */

{{:{{PAGENAME}}/info}}
This is a US Navy free balloon as used for initial lighter-than-air training during the 1920s to 1940s. It is fairly representative for a type of aircraft that first flew in 1783 and soon afterwards found a shape and construction that it retained (almost) to this day.

== Handling instructions ==
[[File:ZF_Navy_free_balloon-2.jpg|thumb|right|300px|The ZF Navy free balloon with the envelope shader enabled.]]
[[File:172P 02.jpg|300px]]
=== Important controls / keys ===

==== Flight controls ====

* Gas valve
* Ballast

==== Ballast ====

* W - Weigh-off to 10% of current weight by dropping ballast. Takes about 10 seconds and only works when on the ground.
* w - Show current on-ground weight. Only works when on the ground.
* D/d - Drop ballast in 1%/0.1% decrements.

==== Gas ====

* F/f - Open/close the gas valve.
* R - Rip the envelope. Use only close to the ground and when you really really want to stay there.

== Dependencies ==

This aircraft depends on instruments from some other aircraft (for FlightGear 2.6.0 and above). Install these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[Short Empire]]
* [[ZLT-NT]]

== Known problems ==

* The balloon envelope shader doesn't show over MP unless the property /sim/rendering/shaders/aircraft/balloon-envelope/quality-level is manually set to 1. The property might no longer be visible in the shader settings dialog also when the ZF Navy free balloon is the user's aircraft.

== External links ==
* [https://web.archive.org/web/20150504200058/http://www.gasballooning.net/resources.htm A very good resource for information about and instructions for gas ballooning]. Has links to couple of (old but good) books available in PDF format.
* [https://web.archive.org/web/20110103124518/http://www.gasballooning.net/BT-2361.pdf Theory of Ballooning, War Department, 25 Apr, 1940]. The basics in 13 pages.

{{Aerostat}}

Zeppelin LZ 121 Nordstern

2025-06-07T09:05:50Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}

''Nordstern'' was the second of two small passenger airships built by Luftschiffbau Zeppelin in 1919 and 1920. ''Nordstern'' was designed to carry about 25 passengers on a Friedrichshafen - Berlin - Stockholm route but this route was never opened. The older sister ship LZ 120 ''Bodensee'' did run a regular passenger service between Friedrichshafen and Berlin during autumn 1919. In compliance with the terms of the peace treaty after WW I both airships were grounded early in 1920. ''Nordstern'' was handed over to France in 1921 where she remained in (sparse) service with the french military until 1926 under the name ''Méditerranée''. ''Bodensee'' was handed over to Italy and remained in service there until 1928 under the name ''Esperia''.

== Important controls / keys ==

=== Aerodynamic flight controls ===

* Rudder
* Elevator

In the most recent versions (FlightGear release 2016.3.1 and higher) there is a hidden crew "autopilot" system providing a virtual helmsman and elevator man. It can be activated by setting the properties
/fdm/jsbsim/crew/helmsman/enabled
/fdm/jsbsim/crew/elevatorman/enabled
to 1 (e.g. using the property browser). The helmsman is directed by the heading bug on the magnetic compass while the target altitude for the elevator man is set by the property
/fdm/jsbsim/crew/elevatorman/altitude-cmd-ft

Currently both channels use true references to guide their control rather than those provided by the aircraft instrumentation.

=== Engine controls ===

The side engines (engine 0 and 1) can be reversed by stopping the engine and starting it in the other direction.

* R - Switch the running direction for the selected engine(s). The engine(s) have to be stopped before switching direction.
* Shift+1 - Select the port side engine (engine 0).
* Shift+2 - Select the starboard side engine (engine 1).
* ~ - Select all engines.

The engines are Maybach MB IVa high altitude engines that can easily be oversped on lower altitudes due to their construction - their rated output of 245 hp @ 1400 RPM is reached well before the throttle is fully open up to an altitude of 1800 m. At emergency power engine speed may go up to 1460 RPM.

=== Gas valve controls ===

* F/f - Open/close the gas valves of the fore gas cells.
* G/g - Open/close the gas valves of the aft gas cells.

Rigid airships like ''Nordstern'' take-off light in a static maneuver and normally land in balance to slightly heavy in a static maneuver. The primary use for the gas valves is to reduce static lightness when needed.

=== Ballast controls ===

* w - Show current on-ground weight. Only works when on the ground.
* W - Weigh off to neutral by adding/removing ballast. Takes about 10 seconds and is only applicable when on the ground.
* e/d - Shift trim ballast fore/aft.
* E/D - Drop one quick-release (a.k.a. emergency) ballast bag fore/aft. There are 6 bags fore and 4 aft.
* Ctrl+W - Refill the quick-release ballast bags from the trim ballast.

Use the "Fuel and payload" dialog to replenish the ballast tanks. Realistically this can only be done while moored.

[[File:Nordstern-elevator-station.jpg|thumb|600px|center|''Nordstern'''s elevator control station. The black toggles release emergency ballast, while the red toggles control the maneuvering gas valves. Below are the pitch inclinometers, the altimeter and, to the right, the variometer.]]

=== Ground crew / Mooring mast ===

* Y - Release mooring mast connection or wire.
* U - Attach mooring wire. Only possible when close to a mooring mast.
* y/u - Play out/winch in mooring wire.
* Alt + click on terrain - Place the mooring mast.

The real ''Nordstern'' never used a mooring mast. All ground handling was done manually with the ground crew manning yaw lines fore and aft and, once within reach, holding on to the handling rails on the control car and the aft engine car.

[[File:Nordstern.jpg|thumb|600px|center|The control car of ''Nordstern''.]]

[[File:Nordstern-interior.jpg|thumb|600px|center|The interior of ''Nordstern'''s control car.]]

== Installation and Dependencies ==

* LZ 121 Nordstern (Development version for [http://github.com/andgi/FlightGear-Nordstern FG/git], click "Download ZIP".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[ZLT-NT]]

== Known problems ==

* The anachronistic mast truck is invisible in 2.10.0. The problem has been fixed in subsequent versions of FlightGear.

* Under some conditions at low or negative airspeed the airship can suffer from undamped yaw oscillations. This seems to be an interaction between the added mass simulation and the dynamic aerodynamic coefficients. (old)

* Real weather fetch sometimes cause NaN problems.

* Before FlightGear 2016.1.1 the mooring force calculations were sensitive to long frame times (i.e. very low fps), which could cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Try setting /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==

* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or later. '''Note: The most up to date version of the Zeppelin LZ 121 Nordstern is available in FlightGear/git.'''

{{Aerostat}}

[[Category:Historical aircraft]]
[[Category:Airships]]

Gokstad ship

2025-06-07T09:04:33Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}

The Gokstad ship is a ''karvi'', a small type of Viking longship. It is a 24 meter long open clinker-built hull constructed from oak and was built some time around 900 AD. Some time after, maybe about 950 - 1000 AD, it was placed as grave furniture in and below a large burial mound near the Gokstad farm in southern Norway. The ship was rediscovered in 1880 when the mound was excavated by archaeologists. The clay soil had preserved most of the hull, but the exact nature of the rigging for the single large mast, generally believed to have carried a single large square sail below a single yard, is somewhat unclear.

== Handling and controls ==

=== Sail ===

The modelling of the rigging is in a very early state.
The following controls are available for the sail:

The throttle axis ({{Key press|PgUp}}, {{Key press|PgDn}}) controls the amount of reefing.
The aileron axis ({{Key press|Left}}, {{Key press|Right}}) controls the bracing of the yard, i.e. turns the sail.

The weather vane is a useful tool to trim the sail.

=== Rudder ===

The rudder is controlled by the standard rudder input, keypad '0' and ',' or any rudder axis connected.

== Installation and Dependencies ==

* The Gokstad ship ({{github source|user=andgi|repo=FlightGear-Gokstad|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Gokstad|text=Download ZIP}}".)

This "aircraft" depends on resources from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.
* [[Swedish Navy T21 class MTB]] (a.k.a. MTB_20m) ({{github source|user=andgi|repo=FlightGear-Gokstad|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-MTB_20m|text=Download ZIP}}".)

== Known problems ==

* The hydrodynamics planing model may react poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. On some systems this appears to have a considerable impact on the frame rate.

Short Empire

2025-06-07T08:55:39Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}
The Short S.23 'C'-class Empire flying boats were designed and built by Short Brothers in 1935 to a specification and order placed by Imperial Airways. A total of 31 Short S.23 flying boats were built, 25 for Imperial Airways and 6 for QANTAS Empire Airways.
The first S.23 to fly was ''Canopus'' on July 3 1936 and the last was ''Caledonia'', scrapped 23 March 1947. Between those years the S.23 Empire flying boats served a route network stretching (at times) from [http://www.flyingboatmuseum.com/ Foynes] (Ireland) in the north-west, Durban (South Africa) in the south to Sydney (Australia) in the south-east. The improved versions Short S.30 (9 built) and Short S.33 (2 built) are also considered as 'C'-class Empire flying boats but are not yet represented in FlightGear.

== Cockpit, instruments and controls ==

[[File:Short_Empire_panel.jpg|700px|The Captain's and the First Officer's dashboard.]]

The Captain's and the First Officer's dashboard together with the Throttle box in the middle, with the throttle (top), mixture (middle, not in picture) and propeller pitch (bottom, not in picture) control levers. At the top of the centre part are the engine starter buttons.

=== Flap control panel ===

The flap control panel is mounted in the roof above the windscreen. To begin extending/retracting the flaps turn the operating switch towards FLAPS OUT/FLAPS IN. Return the operating switch to the center position once the desired position is reached. The red indicator light is lit when the flaps are beyond the 1/3 setting. The blue pilot light indicates that the flap control system is powered.

Flap settings above 1/3 must no be used for take-off. Maximum speed with fully extended flaps is 115 mph (100 knots).

=== Fuel system ===

Close to the roof at the center of the rear bulkhead of the flight deck are the fuel contents gauges and slightly forward in the roof is a control box for the fuel supply control levers. The Short S.23 as delivered came with 3 different fuel system capacities depending on the intended use of the aircraft. The systems were

; '''Mark I''' standard/short-range.
: The standard fuel system used on 27 aircraft. There are two 326 (imperial) gallon fuel tanks, one in each wing. The control levers are (left to right) the ''red'' lever opens and shuts the supply from the port tank, the ''black'' lever opens a balancing line for equalising the tank content (not fully implemented yet) and the ''green'' lever controls the supply from the starboard tank.
; '''Mark II''' medium-range.
: One outboard 179 and one 326 (imperial) gallon tank in each wing. Used on the aircraft ''Cavalier'' and ''Centarus''. The fuel supply control levers and fuel content gauges are in the places as for the Mark I fuel system and in the intuitive order.
; '''Mark III''' long-range.
: One outboard 179, one 326 and one inboard 380 (imperial) gallon tank in each wing and two 280 gallon tanks in the hull aft of the flight deck. Used on the aircraft ''Cambria'' and ''Caledonia'' which undertook a series of trial crossings of the North Atlantic in the summer of 1937. The S.23 could not carry a meaningful payload across the Atlantic. The fuel supply control levers are split between the roof mounted control box and a control box on the port side of the rear bulkhead. On the roof mounted control box the ''green'' levers controls the starboard wing tanks, from the right side outboard, middle and inboard, the ''red'' levers control the supply from the port middle and outboard tanks. On the port control box the single ''green'' lever control the supply from the right hull tank, while the two ''red'' levers control the port hull and inboard wing tanks.

In FlightGear the fuel system type is controlled by the selected livery. Unavailable tanks are forced empty.

[[File:Short_Empire-flight-deck-aft.jpg|300px|A view towards the rear bulkhead of the flight deck of a Mark I S.23.]]
[[File:Televel-fuel-gauge.jpg|300px|A Televel fuel content gauge.]]

The Televel fuel content gauges are used to measure the tank contents. Wind the handle clockwise to free the probe from the float in the tank, then slowly anticlockwise until the probe hits the float and the scale stops moving. The scale index then shows the current tank content.

{| border="1" style="text-align:center"
|+ '''Tank designations'''
! Tank position !! Capacity (Imperial gallons) !! Mark I !! Mark II !! Mark III
|-
| Port wing middle
| 326 || X || X || X
|-
| Starboard wing middle
| 326 || X || X || X
|-
| Port wing outer
| 179 || || X || X
|-
| Starboard wing outer
| 179 || || X || X
|-
| Port wing inner
| 380 || || || X
|-
| Starboard wing inner
| 380 || || || X
|-
| Port side fuselage
| 280 || || || X
|-
| Starboard side fuselage
| 280 || || || X
|}

All tanks on each side are connected to a common supply point which feed the fuel pumps of the engines on that side. From the engine driven fuel pumps, one at each engine, fuel is feed into a feed line connected to all four engines.
There are three fuel pump test cocks inserted into the fuel feed line which can be closed to isolate each fuel pump and engine to verify the operation of the fuel pump. The control for the ''central fuel pump test cock'', which connects the left and right sides of the fuel feed line, is located on the right side of the flight deck just forward of the rear bulkhead. The ''left and right fuel pump test cocks'', which connect the feed line of the inner and outer engine on the respective sides, are controlled by the lower pair of large hand wheels on the rear bulkhead of the flight deck.

=== Sperry A-2 autopilot ===

The Sperry A-2 automatic pilot (or gyropilot as the flight manual calls it) is a 3-axis autopilot that provides heading, pitch and roll hold.

[[File:Sperry_A-2.jpg|700px|The Sperry A-2 autopilot.]]

'''Checklist: Engaging the gyropilot'''
* Check vacuum, 3 - 5 inHg.
* Check oil pressure (not available yet).
* Open speed valves.
* Check the Directional Gyro setting and that both gyros are uncaged.
* Trim the aircraft to fly hands-off.
* Set the follow-up indices to match the current gyro indications.
* Engage the gyropilot. The autopilot engage lever is located above the propeller pitch controls at the rear of the throttle box.

If there is an oscillation on one or more of the controls slowly close the corresponding speed valves until the oscillation stops.
A speed valve should not be closed completely as that will lock the corresponding control. The speed valves are below the window on the port side of the captain's seat. (Note: in FlightGear 2.6.0 or earlier the speed valves are only available via the property browser, in <code>/fdm/jsbsim/sperry-autopilot/ </code>.)

'''Turns'''
* Small heading adjustments can be made as flat turns by turning the heading knob slowly.
* For larger adjustments lock the rudder by closing the heading speed valve and turn by setting an appropriate bank via the roll knob. Alternatively, set an appropriate bank via the roll knob and continuously turn the heading knob to keep an appropriate rudder response. Or disconnect the autopilot and fly the turn manually.

[[File:Short_Empire_cockpit-LHS.jpg|700px|The left-hand side of the cockpit with the Sperry A-2 speed valves and the light switches.]]

=== Electrical system ===

The main electrical switchboard is located on the starboard side to the rear of the flight deck. The switchboard contains the master switches for the instrument lighting and the interior lighting and the switch for the navigation lights. All 6 switches should be on (down) for flight.
Below the main unit are 4 brass switches for the rear flight deck lighting.

[[File:Short_Empire_-_Main_electrical_switchboard.jpg|700px|The main electrical switchboard on the starboard side to the rear of the flight deck.]]

=== Navigational equipment ===

Most of Imperial Airways' route network had short sectors (and the standard Empire flying boats also had a quite limited range) that were navigated using dead-reckoning supplemented by visual observations and radio direction finding, both by using the loop aerial and by radio bearings measured and reported by ground stations. On the more remote parts of the route network the radio navigational aids were unreliable and few and far between.

On long sectors, and in particular over water, such as on the trial crossings of the North Atlantic, celestial sightings were an important additional input to the navigation process.

[[File:Short_Empire-astro-hatch.jpg|700px|The hatch behind the First Officer's seat on flight deck were used for making celestial observations.]]

In FlightGear the First Officer can use the RAF mk9 bubble sextant available to the right of his seat by clicking on its handle (see also the link under [[#External links|References]] below). The astro-hatch is likewise opened by clicking on it. The First Officer can walk around the flight deck using the '{{Key press|W}}','{{Key press|A}}','{{Key press|S}}' and '{{Key press|D}}' keys.

The equipment used for radio direction finding is not yet implemented but a reasonable approximation can be had by using the ADF information presented by the nav-training-osd.xml add-on linked under [[#External links|References]] below.

== Handling instructions ==

'''Disclaimer:''' These instructions are derived only from common sense together with certain data from the available records and have no connection whatsoever to any instructions for the real aircraft.

=== Engine start ===

* Mixture rich
* Airscrew pitch FINE {{key press|Shift|N}}
* Magnetos set to both {{key press|<nowiki>}</nowiki>}} {{key press|<nowiki>}</nowiki>}} {{key press|<nowiki>}</nowiki>}}
* Run starter as required on one engine at the time {{key press|shift|engine#}}; {{key press|s}} ({{key press|~}} to select all engines again)
* The throttle might need to be opened up quite a bit. (Full throttle might currently be needed.)
* The starter performance may be degraded when starting on the aircraft battery (the only supported option so far).

=== Pre-take off ===

* Center of gravity within the legal range (See the aircraft help.)
* Verify that all fuel pumps are operating by closing the fuel pump test cocks to isolate the pumps during engine run up. '''The fuel pump test cocks MUST be opened again before take-off.'''
* Flaps 1/3. '''Warning:''' Flap settings above 1/3 may cause severe porpoising during take-off.

=== Take off ===

* The take-off run should be into the wind
* Full power (max 5 minutes)
* Use rudder, aileron and asymmetric thrust as required to make the take-off run straight
* Keep the control column back, take off pitch is about 9 deg
* Minimum getting off speed 78 mph.
* Recommended climb speed at least 120 mph

=== Cruise ===

* Mixture rich of peak
* Airscrew pitch COARSE ({{Key press|n}})
* Typical cruise speed 165 mph

=== Landing ===

* Flaps 1/3 - full as required
* Airscrew pitch FINE ({{Key press|Shift|N}}).
* Recommended approach speed 115 mph.
* Beware of water-loops - keep the nose up.

== Routes and staging-posts ==

The prewar Empire Air Mail Scheme (EAMS) in three maps (click to view):
* [http://www.gcmap.com/mapui?P=50.8723N+1.38751W+-+44.3832N+1.18423W%0D%0A46.2909N+4.83100E%0D%0A47.2974N+2.13431W%0D%0A44.3832N+1.18423W+-+43.4469N+5.18541E%0D%0A43.4469N+5.18541E+-+42.1138N+12.1872E%0D%0A42.1138N+12.1872E+-+40.651N+17.9616E%0D%0A40.651N+17.9616E+-++37.9395N+23.6662E%0D%0A39.6147N+19.9297E%0D%0A37.9395N+23.6662E+-+35.2004N+25.723E%0D%0A35.3444N+25.1403E%0D%0A35.2004N+25.723E+-+31.2065N+29.894E%0D%0A&MS=wls&DU=mi&SG=155&SU=mph Southampton, UK - Alexandria, Egypt]
* [http://www.gcmap.com/mapui?P=31.2065N+29.894E+-+25.7011N+32.6365E%0D%0A25.7011N+32.6365E+-+21.9708N+31.3051E%0D%0A21.9708N+31.3051E+-+15.6151N+32.5376E%0D%0A15.6151N+32.5376E+-+13.1857N+32.6655E%0D%0A13.1857N+32.6655E+-+9.5281N+31.6483E%0D%0A9.5281N+31.6483E+-+3.54863N+31.8127E%0D%0A6.22541N+31.5398E%0D%0A4.83484N+31.6175E%0D%0A3.54863N+31.8127E+-+0.287703N+32.6523E%0D%0A1.82913N+31.3294E%0D%0A0.287703N+32.6523E+-+0.7806S+36.4002E%0D%0A0.0901S+34.7481E%0D%0A0.7806S+36.4002E+-+4.0524S+39.6799E%0D%0A4.0524S+39.6799E+-+6.8222S+39.2922E%0D%0A6.8222S+39.2922E+-+10.001S+39.7215E%0D%0A10.001S+39.7215E+-+15.0382S+40.7041E%0D%0A15.0382S+40.7041E+-+19.8265S+34.8316E%0D%0A19.8265S+34.8316E+-+29.8727S+31.0325E%0D%0A&MS=wls&DU=mi&SG=155&SU=mph Alexandria, Egypt - Durban, South Africa]
* [http://www.gcmap.com/mapui?P=31.2065N+29.894E+-+32.8042N+35.5453E%0D%0A32.8042N+35.5453E+-+33.3462N+43.5474E%0D%0A33.3462N+43.5474E+-+30.5203N+47.8455E%0D%0A30.5203N+47.8455E+-+26.2017N+50.6958E%0D%0A29.3546N+47.9349E%0D%0A26.2017N+50.6958E+-+25.3764N+55.3884E%0D%0A25.3764N+55.3884E+-+25.0534N+61.7359E%0D%0A25.0534N+61.7359E+-+24.8365N+67.0038E%0D%0A24.8365N+67.0038E+-+25.0626N+73.8963E%0D%0A24.5736N+73.6808E%0D%0A25.0626N+73.8963E+-+26.2138N+77.9926E%0D%0A26.2138N+77.9926E+-+25.4274N+81.865E%0D%0A25.5053N+78.7558E%0D%0A25.4274N+81.865E+-+22.5886N+88.3475E%0D%0A22.5886N+88.3475E+-+20.1382N+92.9028E%0D%0A20.1382N+92.9028E+-+16.7336N+96.2092E%0D%0A16.7336N+96.2092E+-+13.658N+100.55E%0D%0A13.658N+100.55E+-+9.5633N+100.054E%0D%0A9.5633N+100.054E+-+5.41825N+100.348E%0D%0A5.41825N+100.348E+-+1.30228N+103.87E%0D%0A1.30228N+103.87E+-+6.11878S+106.835E%0D%0A6.11878S+106.835E+-+7.18759S+112.734E%0D%0A7.18759S+112.734E+-+8.45037S+118.713E%0D%0A8.45037S+118.713E+-+10.1526S+123.587E%0D%0A10.1526S+123.587E+-+12.4733S+130.847E%0D%0A12.4733S+130.847E+-+13.9536S+136.411E%0D%0A13.9536S+136.411E+-+17.4724S+140.835E%0D%0A17.4724S+140.835E+-+19.2481S+146.827E%0D%0A19.2481S+146.827E+-+23.8289S+151.252E%0D%0A23.8289S+151.252E+-+27.4275S+153.128E%0D%0A27.4275S+153.128E+-+33.8684S+151.263E%0D%0A&MS=wls&DU=mi&SG=155&SU=mph Alexandria, Egypt - Sydney, Australia]

These maps are made with the [http://www.gcmap.com/ Great Circle Mapper].

== Installation and Dependencies ==

* Short Empire (See the infobox above for the latest release) ([[FGAddon]] or [http://github.com/andgi/FlightGear-Short_Empire FG/git])

== Known problems ==

* Real weather fetch sometimes cause NaN problems.

== External links ==
* [http://www.gidenstam.org/FlightGear/.images/Short_Empire/ Experimental FlightGear 2.0.0 back-port.] Read the [[#Installation and Dependencies|install instructions]]. '''Note: The most up to date version of the Short Empire is available in FlightGear/git.'''
* [http://www.gidenstam.org/FlightGear/.images/Short_Empire/ROUTES.txt A work-in-progress document on the various routes where the Short Empire Flying boats were used].
* [http://www.gidenstam.org/FlightGear/Celestial_navigation_in_fgfs/ A very short introduction to celestial navigation in FlightGear]. The Short Empire flying-boat has the required instruments.
* [http://www.gidenstam.org/FlightGear/misc/nav-training-osd.xml Add-on on-screen display of compass and directional gyro heading and basic radio direction finding readings].

* {{wikipedia|Short Empire}}
[[de:Short Empire]]

Submarine Scout

2025-06-07T08:52:48Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}
The '''Submarine Scout''' was a fairly small blimp, i.e. non-rigid airship, which was used for maritime patrol and convoy escort by the Royal Naval Air Service (RNAS) during World War I. The type first flew in 1915 and was in service throughout the rest of the war.
The early versions had cars made from slightly modified aeroplane fuselages; the final version, Submarine Scout Zero represented here, had a purpose built car.

== Handling instructions ==

=== Important controls / keys / instruments ===

==== Flight controls ====

* Rudder (Aileron input is transferred to the rudder for convenience.)
* Elevator

In the real aircraft the pilot had rudder pedals for the rudder and an elevator wheel located in front of him (with its axis across the cockpit) for the elevators.

==== Ballast ====

{| class="keytable"
! Key
! Function
|-
| {{key press|W}}
| Weigh-off to 50 lbs heavy by adjusting ballast. Takes about 10 seconds and only works when on the ground.
|-
| {{key press|w}}
| Show current on-ground weight. Only works when on the ground.
|-
| {{key press|D}}/{{key press|d}}
| Drop ballast in 1%/0.1% decrements. (Rarely used.)
|}

This type of blimp normally operates from about 100 lbs heavy to a few 100 lbs light.

==== Gas and Envelope ====

{| class="keytable"
! Key
! Function
|-
| {{key press|F}}/{{key press|f}}
| Open/close the gas valve.
|-
| {{key press|Q}}/{{key press|q}}
| Open/close fore ballonet relief valve.
|-
| {{key press|A}}/{{key press|a}}
| Open/close aft ballonet relief valve.
|-
| {{key press|Ctrl|Q}}
| Open/close fore ballonet inflow valve.
|-
| {{key press|Ctrl|A}}
| Open/close aft ballonet inflow valve.
|}

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume (mainly due to altitude changes); and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

The ballonets are inflated by air from the propeller slip stream, collected with the scoop and passed via fabric trunks and closeable no-return valves to the ballonets. The ballonet relief valve automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty).
Maintain the envelope pressure at about 15 - 25mm water, shown by the height difference between the outer and inner fluid in the manometers (which have no scale yet!).

The gas valve is basically only used to valve some gas if the airship is found too light during the pre-landing weigh off.

In the version released with FlightGear 1.9.0/1 both ballonets continuously received a constant in-flow of air instead. The degree of inflation (and total pressure) is controlled by "bleeding" more or less air from either ballonet relief valve.

To trim towards:
* nose heavy - open the fore ballonet inflow valve and the aft ballonet relief valve (nose gets heavier / tail lighter).
* tail heavy - open the aft ballonet inflow valve and the fore ballonet valve more (tail gets heavier / nose lighter).

Don't open the ballonet relief valves too wide or the envelope pressure will drop too low. Monitor the pressure gauges! You might need to rev up the engine to restore the envelope pressure at times (in particular when descending).

==== Ground crew ====

{| class ="keytable"
! Key
! Function
|-
| {{key press|U}}
| Request ground crew to prepare for landing.
|-
| {{key press|Y}}
| Tell ground crew to let go. Do this before you take-off.
|-
| {{key press|Alt}} + click on terrain
| Place the ground crew.
|}

On the prepare-for-landing request the ground crew will align to the current wind conditions. When landing you should aim to approach against the wind and arrive exactly in between the left and right ground teams with very low speed and altitude.

The ground crew is visible over the multiplayer network.

==== Cockpit and instruments ====

[[File:Submarine_Scout_cockpit.jpg]]

Upper row left to right: Airspeed indicator, Compass and Altimeter (Note: The altimeter reads in 100s rather than 1000s feet).

Lower row left to right: Tachometer, Left and right magneto switches, Clinometer, Watch, Pressure gauges for fore ballonet, main envelope and aft ballonet.

==== Armament ====

The Submarine Scout airship is armed with two 65lb bombs. The bombs can be dropped one at the time by actuating the default weapon trigger from the pilot view. Bomb impacts are visible over the multiplayer network.

'''Note:''' By default the weapon trigger is not mapped to any control in FlightGear. However, most joystick configurations put it on a button or a button + key combination.

==== ALDIS signalling lamp ====

[[File:Submarine Scout ALDIS lamp.jpg]]

The observer view has an ALDIS lamp for morse code signalling. The ALDIS lamp can be picked up or stowed in the observer view by clicking the lamp handle.
The lamp is actuated by the default weapon trigger in all views except the pilot view. The lamp state is visible over the multiplayer network.

=== Airship piloting ===

==== Static controls ====

* Buoyancy
* Weight
* Envelope pressure
* Trim

===== Checking the static condition =====

There is no instrument on the Submarine Scout that directly show if the airship is light or heavy and what the static trim is. To see you have to reduce throttle to idle and wait for the speed to decrease. As the aerodynamic forces diminish the airship will start to rise or descent depending on its lightness/heaviness and its pitch attitude will show how nose/tail heavy it is.

To some extent the lightness/heaviness is also apparent in how the 'ship handles at speed - a heavy 'ship requires a nose up attitude to maintain altitude - while a light ship requires a nose down attitude.

==== Dynamic controls ====

* Rudder
* Elevator
* Throttle

=== Basic manoeuvres ===

==== Take-off ====

* Set ballonet valves to 0%/2% (fore/aft). This will slowly make the ship more nose heavy which is suitable for cruise.
* Tell ground crew to let go (Y).
* Check weight (w) and weigh off (W) as necessary. 50 lbs or less is a good take off heaviness. Note that each weigh off takes 10 seconds to complete.
* Start engine (magnetos on + s).
* Take off at full power and a nose up attitude.
* When the nose starts to swing up use some down elevator to increase(!) lift and avoid a tail strike.

==== Landing ====

Note: You can position the ground crew by Alt+click on the terrain.

* Check static condition and trim: Neutral trim and slightly heavy is better than light. Check the static condition and trim by stopping the engine and note whether the airship raises or falls as the airspeed drops off and what pitch attitude it tends towards.
* Prepare the ground crew (U). They will (re)position themselves facing the wind.
* Approach is against the wind, low (~150ft) and slow.
* Aim to arrive between the handling parties, below 100ft and with very little ground speed.
* The ground crew uses the handling guys to secure the ship.

[[File:Submarine Scout landing.jpg]]

== Installation and Dependencies ==

* Submarine Scout ([http://github.com/andgi/FlightGear-Submarine_Scout FG/git]) or in the official [[FGAddon]].

== Known problems ==

* The ground handling force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Set /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==
* My GitHub repository for the [https://github.com/andgi/FlightGear-Submarine_Scout Submarine Scout aircraft].
* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] '''Note: The most up to date version of the Submarine Scout is available in my GitHub repository.'''
* [http://www.aht.ndirect.co.uk/airships/ss/index.html Submarine Scout Class information at the Airship Heritage Trust]

{{Aerostat}}

Malmö Flygindustri MFI-9

2025-06-07T08:51:22Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}

Malmö Flygindustri MFI-9 'Junior' was designed by Björn Andreasson based on his earlier home-built aircraft BA-7. The first flight of the
MFI-9 prototype was on May 17 1961. By 1964 23 aircraft had been built and the next model, MFI-9B 'Trainer' with a slightly enlarged
cockpit, was introduced. By the end of production in 1971 47 MFI-9B had been produced and most of the earlier MFI-9 'Junior' had been
upgraded to 9B status. Malmö Flygindustri also tried to sell the MFI-9B as a military trainer and lighweight close air support
(mini-COIN) fighter. This was not successful, apart from 9 civilian MFI-9B that was bought and armed by Carl Gustaf von Rosen for (or
forming) the Biafran Airforce. However, a later larger development, the MFI-15 Safari / MFI-17 Supporter was significantly more successful
in the military market.

In Germany MFI-9 'Junior' was built under license by Bölkow as the Bo 208 'Junior'.

== Installation and Dependencies ==

* MFI-9 ({{fgaddon aircraft source|MFI-9|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-MFI-9|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-MFI-9|text=Download ZIP}}".)

This aircraft depends on instruments from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.

* [[Short_Empire]] ({{fgaddon aircraft source|Short_Empire|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Short_Empire|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Short_Empire|text=Download ZIP}}".)
* [[ZLT-NT]] ({{fgaddon aircraft source|ZLT-NT|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-ZLT-NT|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-ZLT-NT|text=Download ZIP}}".)

== Known problems ==

* The hydrodynamics planing model for the sea plane version requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. On some systems this appears to have a considerable impact on the frame rate. The increased FDM rate is set for all variants.

Swedish Navy T21 class MTB

2025-06-07T08:48:00Z

AndersG: /* Installation and Dependencies */

{{:{{PAGENAME}}/info}}
The Swedish Navy T21 class motor torpedo boat were the second Swedish MTB class developed during the first years of WWII. The design was provided by the Italian companies Baglietto and CRDA but the 11 boats were manufactured at the Kockums shipyard in Sweden during 1942-43. They remained in service until the late 1950s, and some were retained for special purposes much longer. At least one remains today, T26, which has been restored to service condition, and as the hulls of some of others were sold on the civilian market after being decommissioned there might still be some other hulls around.

The 20 m long boats were powered by two 1500 hp Isotta Fraschini IF184 supercharged petrol engines giving a top speed of about 50 knots. The armament consisted of two 53 cm torpedoes and a 20 mm AA cannon.

== Handling and controls ==

=== Engine controls ===

The MTB is equipped with two 1500 hp Isotta Fraschini IF184 main engines and two auxiliary Ford V8 engines for low speed manoeuvring. One main engine and one auxiliary engine is connected to each of the two propellers via gearboxes and clutches.

'''Main Engine Start'''
# Disengage the main engine clutches ({{Key press|Q}}). This action also selects the two main engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH (''three times on'' {{Key press|}}}).
# Start the engines ({{Key press|s}}).
# Engage the main engine clutches ({{Key press|q}}). This action also selects the two main engines.

'''Auxiliary Engine Start'''
# Disengage the auxiliary engine clutches ({{Key press|E}}). This action also selects the two auxiliary engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH (''three times on'' {{Key press|}}}).
# Start the engines ({{Key press|s}}).
# Engage the auxiliary engine clutches ({{Key press|e}}). This action also selects the two auxiliary engines.

Be careful to avoid over-speeding an engine with a disengaged clutch.

== Installation and Dependencies ==

* Swedish Navy T21 class MTB (a.k.a. MTB_20m) ({{github source|user=andgi|repo=FlightGear-MTB_20m|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-MTB_20m|text=Download ZIP}}".)

This "aircraft" depends on instruments and sounds from some other aircraft. Install a matching version of these too. They need to be installed in the same Aircraft/(<each aircraft directory>) directory for FlightGear to find the files.
* [[Zeppelin_LZ_121_Nordstern|Nordstern]] ({{fgaddon aircraft source|Nordstern|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Nordstern|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Nordstern|text=Download ZIP}}".)
* [[Short_Empire]] ({{fgaddon aircraft source|Short_Empire|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Short_Empire|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Short_Empire|text=Download ZIP}}".)

== Known problems ==

* The hydrodynamics planing model often reacts poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain. Quickly reducing speed may help.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. On some systems this appears to have a considerable impact on the frame rate.

Submarine Scout

2025-05-01T09:37:17Z

AndersG: /* Known problems */ Removed very old and solved problems.

{{:{{PAGENAME}}/info}}
The '''Submarine Scout''' was a fairly small blimp, i.e. non-rigid airship, which was used for maritime patrol and convoy escort by the Royal Naval Air Service (RNAS) during World War I. The type first flew in 1915 and was in service throughout the rest of the war.
The early versions had cars made from slightly modified aeroplane fuselages; the final version, Submarine Scout Zero represented here, had a purpose built car.

== Handling instructions ==

=== Important controls / keys / instruments ===

==== Flight controls ====

* Rudder (Aileron input is transferred to the rudder for convenience.)
* Elevator

In the real aircraft the pilot had rudder pedals for the rudder and an elevator wheel located in front of him (with its axis across the cockpit) for the elevators.

==== Ballast ====

{| class="keytable"
! Key
! Function
|-
| {{key press|W}}
| Weigh-off to 50 lbs heavy by adjusting ballast. Takes about 10 seconds and only works when on the ground.
|-
| {{key press|w}}
| Show current on-ground weight. Only works when on the ground.
|-
| {{key press|D}}/{{key press|d}}
| Drop ballast in 1%/0.1% decrements. (Rarely used.)
|}

This type of blimp normally operates from about 100 lbs heavy to a few 100 lbs light.

==== Gas and Envelope ====

{| class="keytable"
! Key
! Function
|-
| {{key press|F}}/{{key press|f}}
| Open/close the gas valve.
|-
| {{key press|Q}}/{{key press|q}}
| Open/close fore ballonet relief valve.
|-
| {{key press|A}}/{{key press|a}}
| Open/close aft ballonet relief valve.
|-
| {{key press|Ctrl|Q}}
| Open/close fore ballonet inflow valve.
|-
| {{key press|Ctrl|A}}
| Open/close aft ballonet inflow valve.
|}

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume (mainly due to altitude changes); and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

The ballonets are inflated by air from the propeller slip stream, collected with the scoop and passed via fabric trunks and closeable no-return valves to the ballonets. The ballonet relief valve automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty).
Maintain the envelope pressure at about 15 - 25mm water, shown by the height difference between the outer and inner fluid in the manometers (which have no scale yet!).

The gas valve is basically only used to valve some gas if the airship is found too light during the pre-landing weigh off.

In the version released with FlightGear 1.9.0/1 both ballonets continuously received a constant in-flow of air instead. The degree of inflation (and total pressure) is controlled by "bleeding" more or less air from either ballonet relief valve.

To trim towards:
* nose heavy - open the fore ballonet inflow valve and the aft ballonet relief valve (nose gets heavier / tail lighter).
* tail heavy - open the aft ballonet inflow valve and the fore ballonet valve more (tail gets heavier / nose lighter).

Don't open the ballonet relief valves too wide or the envelope pressure will drop too low. Monitor the pressure gauges! You might need to rev up the engine to restore the envelope pressure at times (in particular when descending).

==== Ground crew ====

{| class ="keytable"
! Key
! Function
|-
| {{key press|U}}
| Request ground crew to prepare for landing.
|-
| {{key press|Y}}
| Tell ground crew to let go. Do this before you take-off.
|-
| {{key press|Alt}} + click on terrain
| Place the ground crew.
|}

On the prepare-for-landing request the ground crew will align to the current wind conditions. When landing you should aim to approach against the wind and arrive exactly in between the left and right ground teams with very low speed and altitude.

The ground crew is visible over the multiplayer network.

==== Cockpit and instruments ====

[[File:Submarine_Scout_cockpit.jpg]]

Upper row left to right: Airspeed indicator, Compass and Altimeter (Note: The altimeter reads in 100s rather than 1000s feet).

Lower row left to right: Tachometer, Left and right magneto switches, Clinometer, Watch, Pressure gauges for fore ballonet, main envelope and aft ballonet.

==== Armament ====

The Submarine Scout airship is armed with two 65lb bombs. The bombs can be dropped one at the time by actuating the default weapon trigger from the pilot view. Bomb impacts are visible over the multiplayer network.

'''Note:''' By default the weapon trigger is not mapped to any control in FlightGear. However, most joystick configurations put it on a button or a button + key combination.

==== ALDIS signalling lamp ====

[[File:Submarine Scout ALDIS lamp.jpg]]

The observer view has an ALDIS lamp for morse code signalling. The ALDIS lamp can be picked up or stowed in the observer view by clicking the lamp handle.
The lamp is actuated by the default weapon trigger in all views except the pilot view. The lamp state is visible over the multiplayer network.

=== Airship piloting ===

==== Static controls ====

* Buoyancy
* Weight
* Envelope pressure
* Trim

===== Checking the static condition =====

There is no instrument on the Submarine Scout that directly show if the airship is light or heavy and what the static trim is. To see you have to reduce throttle to idle and wait for the speed to decrease. As the aerodynamic forces diminish the airship will start to rise or descent depending on its lightness/heaviness and its pitch attitude will show how nose/tail heavy it is.

To some extent the lightness/heaviness is also apparent in how the 'ship handles at speed - a heavy 'ship requires a nose up attitude to maintain altitude - while a light ship requires a nose down attitude.

==== Dynamic controls ====

* Rudder
* Elevator
* Throttle

=== Basic manoeuvres ===

==== Take-off ====

* Set ballonet valves to 0%/2% (fore/aft). This will slowly make the ship more nose heavy which is suitable for cruise.
* Tell ground crew to let go (Y).
* Check weight (w) and weigh off (W) as necessary. 50 lbs or less is a good take off heaviness. Note that each weigh off takes 10 seconds to complete.
* Start engine (magnetos on + s).
* Take off at full power and a nose up attitude.
* When the nose starts to swing up use some down elevator to increase(!) lift and avoid a tail strike.

==== Landing ====

Note: You can position the ground crew by Alt+click on the terrain.

* Check static condition and trim: Neutral trim and slightly heavy is better than light. Check the static condition and trim by stopping the engine and note whether the airship raises or falls as the airspeed drops off and what pitch attitude it tends towards.
* Prepare the ground crew (U). They will (re)position themselves facing the wind.
* Approach is against the wind, low (~150ft) and slow.
* Aim to arrive between the handling parties, below 100ft and with very little ground speed.
* The ground crew uses the handling guys to secure the ship.

[[File:Submarine Scout landing.jpg]]

== Installation and Dependencies ==

* Submarine Scout ([http://github.com/andgi/FlightGear-Submarine_Scout FG/git]) or in the official [[FGAddon]] (needs [[Sopwith Camel]] installed but fetching instruments from there seems not to work now in 2025).

== Known problems ==

* The ground handling force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Set /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

== External links ==
* My GitHub repository for the [https://github.com/andgi/FlightGear-Submarine_Scout Submarine Scout aircraft].
* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] '''Note: The most up to date version of the Submarine Scout is available in my GitHub repository.'''
* [http://www.aht.ndirect.co.uk/airships/ss/index.html Submarine Scout Class information at the Airship Heritage Trust]

{{Aerostat}}

Submarine Scout

2025-05-01T09:35:22Z

AndersG: /* External links */ Updated the links.

{{:{{PAGENAME}}/info}}
The '''Submarine Scout''' was a fairly small blimp, i.e. non-rigid airship, which was used for maritime patrol and convoy escort by the Royal Naval Air Service (RNAS) during World War I. The type first flew in 1915 and was in service throughout the rest of the war.
The early versions had cars made from slightly modified aeroplane fuselages; the final version, Submarine Scout Zero represented here, had a purpose built car.

== Handling instructions ==

=== Important controls / keys / instruments ===

==== Flight controls ====

* Rudder (Aileron input is transferred to the rudder for convenience.)
* Elevator

In the real aircraft the pilot had rudder pedals for the rudder and an elevator wheel located in front of him (with its axis across the cockpit) for the elevators.

==== Ballast ====

{| class="keytable"
! Key
! Function
|-
| {{key press|W}}
| Weigh-off to 50 lbs heavy by adjusting ballast. Takes about 10 seconds and only works when on the ground.
|-
| {{key press|w}}
| Show current on-ground weight. Only works when on the ground.
|-
| {{key press|D}}/{{key press|d}}
| Drop ballast in 1%/0.1% decrements. (Rarely used.)
|}

This type of blimp normally operates from about 100 lbs heavy to a few 100 lbs light.

==== Gas and Envelope ====

{| class="keytable"
! Key
! Function
|-
| {{key press|F}}/{{key press|f}}
| Open/close the gas valve.
|-
| {{key press|Q}}/{{key press|q}}
| Open/close fore ballonet relief valve.
|-
| {{key press|A}}/{{key press|a}}
| Open/close aft ballonet relief valve.
|-
| {{key press|Ctrl|Q}}
| Open/close fore ballonet inflow valve.
|-
| {{key press|Ctrl|A}}
| Open/close aft ballonet inflow valve.
|}

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume (mainly due to altitude changes); and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

The ballonets are inflated by air from the propeller slip stream, collected with the scoop and passed via fabric trunks and closeable no-return valves to the ballonets. The ballonet relief valve automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty).
Maintain the envelope pressure at about 15 - 25mm water, shown by the height difference between the outer and inner fluid in the manometers (which have no scale yet!).

The gas valve is basically only used to valve some gas if the airship is found too light during the pre-landing weigh off.

In the version released with FlightGear 1.9.0/1 both ballonets continuously received a constant in-flow of air instead. The degree of inflation (and total pressure) is controlled by "bleeding" more or less air from either ballonet relief valve.

To trim towards:
* nose heavy - open the fore ballonet inflow valve and the aft ballonet relief valve (nose gets heavier / tail lighter).
* tail heavy - open the aft ballonet inflow valve and the fore ballonet valve more (tail gets heavier / nose lighter).

Don't open the ballonet relief valves too wide or the envelope pressure will drop too low. Monitor the pressure gauges! You might need to rev up the engine to restore the envelope pressure at times (in particular when descending).

==== Ground crew ====

{| class ="keytable"
! Key
! Function
|-
| {{key press|U}}
| Request ground crew to prepare for landing.
|-
| {{key press|Y}}
| Tell ground crew to let go. Do this before you take-off.
|-
| {{key press|Alt}} + click on terrain
| Place the ground crew.
|}

On the prepare-for-landing request the ground crew will align to the current wind conditions. When landing you should aim to approach against the wind and arrive exactly in between the left and right ground teams with very low speed and altitude.

The ground crew is visible over the multiplayer network.

==== Cockpit and instruments ====

[[File:Submarine_Scout_cockpit.jpg]]

Upper row left to right: Airspeed indicator, Compass and Altimeter (Note: The altimeter reads in 100s rather than 1000s feet).

Lower row left to right: Tachometer, Left and right magneto switches, Clinometer, Watch, Pressure gauges for fore ballonet, main envelope and aft ballonet.

==== Armament ====

The Submarine Scout airship is armed with two 65lb bombs. The bombs can be dropped one at the time by actuating the default weapon trigger from the pilot view. Bomb impacts are visible over the multiplayer network.

'''Note:''' By default the weapon trigger is not mapped to any control in FlightGear. However, most joystick configurations put it on a button or a button + key combination.

==== ALDIS signalling lamp ====

[[File:Submarine Scout ALDIS lamp.jpg]]

The observer view has an ALDIS lamp for morse code signalling. The ALDIS lamp can be picked up or stowed in the observer view by clicking the lamp handle.
The lamp is actuated by the default weapon trigger in all views except the pilot view. The lamp state is visible over the multiplayer network.

=== Airship piloting ===

==== Static controls ====

* Buoyancy
* Weight
* Envelope pressure
* Trim

===== Checking the static condition =====

There is no instrument on the Submarine Scout that directly show if the airship is light or heavy and what the static trim is. To see you have to reduce throttle to idle and wait for the speed to decrease. As the aerodynamic forces diminish the airship will start to rise or descent depending on its lightness/heaviness and its pitch attitude will show how nose/tail heavy it is.

To some extent the lightness/heaviness is also apparent in how the 'ship handles at speed - a heavy 'ship requires a nose up attitude to maintain altitude - while a light ship requires a nose down attitude.

==== Dynamic controls ====

* Rudder
* Elevator
* Throttle

=== Basic manoeuvres ===

==== Take-off ====

* Set ballonet valves to 0%/2% (fore/aft). This will slowly make the ship more nose heavy which is suitable for cruise.
* Tell ground crew to let go (Y).
* Check weight (w) and weigh off (W) as necessary. 50 lbs or less is a good take off heaviness. Note that each weigh off takes 10 seconds to complete.
* Start engine (magnetos on + s).
* Take off at full power and a nose up attitude.
* When the nose starts to swing up use some down elevator to increase(!) lift and avoid a tail strike.

==== Landing ====

Note: You can position the ground crew by Alt+click on the terrain.

* Check static condition and trim: Neutral trim and slightly heavy is better than light. Check the static condition and trim by stopping the engine and note whether the airship raises or falls as the airspeed drops off and what pitch attitude it tends towards.
* Prepare the ground crew (U). They will (re)position themselves facing the wind.
* Approach is against the wind, low (~150ft) and slow.
* Aim to arrive between the handling parties, below 100ft and with very little ground speed.
* The ground crew uses the handling guys to secure the ship.

[[File:Submarine Scout landing.jpg]]

== Installation and Dependencies ==

* Submarine Scout ([http://github.com/andgi/FlightGear-Submarine_Scout FG/git]) or in the official [[FGAddon]] (needs [[Sopwith Camel]] installed but fetching instruments from there seems not to work now in 2025).

== Known problems ==

* The ground handling force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Set /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* (FlightGear 1.9.x) Unfortunately the envelope isn't initialized in a pressurized state. The ballonet valves are set for inflation so the operating pressure is usually reached within a short time.

* (FlightGear 1.9.x) Obsolete copies of <tt>mp_broadcast.nas</tt> (e.g. from the WildFire or Air racing add-ons) could cause problems. The up to date version now resides in <tt>[[$FG_ROOT]]/Nasal/mp_broadcast.nas</tt>. Remove the others - there should be no need for them.

== External links ==
* My GitHub repository for the [https://github.com/andgi/FlightGear-Submarine_Scout Submarine Scout aircraft].
* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] '''Note: The most up to date version of the Submarine Scout is available in my GitHub repository.'''
* [http://www.aht.ndirect.co.uk/airships/ss/index.html Submarine Scout Class information at the Airship Heritage Trust]

{{Aerostat}}

Submarine Scout

2025-05-01T09:30:42Z

AndersG: /* Installation and Dependencies */ My GitHub version shows all instruments now.

{{:{{PAGENAME}}/info}}
The '''Submarine Scout''' was a fairly small blimp, i.e. non-rigid airship, which was used for maritime patrol and convoy escort by the Royal Naval Air Service (RNAS) during World War I. The type first flew in 1915 and was in service throughout the rest of the war.
The early versions had cars made from slightly modified aeroplane fuselages; the final version, Submarine Scout Zero represented here, had a purpose built car.

== Handling instructions ==

=== Important controls / keys / instruments ===

==== Flight controls ====

* Rudder (Aileron input is transferred to the rudder for convenience.)
* Elevator

In the real aircraft the pilot had rudder pedals for the rudder and an elevator wheel located in front of him (with its axis across the cockpit) for the elevators.

==== Ballast ====

{| class="keytable"
! Key
! Function
|-
| {{key press|W}}
| Weigh-off to 50 lbs heavy by adjusting ballast. Takes about 10 seconds and only works when on the ground.
|-
| {{key press|w}}
| Show current on-ground weight. Only works when on the ground.
|-
| {{key press|D}}/{{key press|d}}
| Drop ballast in 1%/0.1% decrements. (Rarely used.)
|}

This type of blimp normally operates from about 100 lbs heavy to a few 100 lbs light.

==== Gas and Envelope ====

{| class="keytable"
! Key
! Function
|-
| {{key press|F}}/{{key press|f}}
| Open/close the gas valve.
|-
| {{key press|Q}}/{{key press|q}}
| Open/close fore ballonet relief valve.
|-
| {{key press|A}}/{{key press|a}}
| Open/close aft ballonet relief valve.
|-
| {{key press|Ctrl|Q}}
| Open/close fore ballonet inflow valve.
|-
| {{key press|Ctrl|A}}
| Open/close aft ballonet inflow valve.
|}

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume (mainly due to altitude changes); and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

The ballonets are inflated by air from the propeller slip stream, collected with the scoop and passed via fabric trunks and closeable no-return valves to the ballonets. The ballonet relief valve automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty).
Maintain the envelope pressure at about 15 - 25mm water, shown by the height difference between the outer and inner fluid in the manometers (which have no scale yet!).

The gas valve is basically only used to valve some gas if the airship is found too light during the pre-landing weigh off.

In the version released with FlightGear 1.9.0/1 both ballonets continuously received a constant in-flow of air instead. The degree of inflation (and total pressure) is controlled by "bleeding" more or less air from either ballonet relief valve.

To trim towards:
* nose heavy - open the fore ballonet inflow valve and the aft ballonet relief valve (nose gets heavier / tail lighter).
* tail heavy - open the aft ballonet inflow valve and the fore ballonet valve more (tail gets heavier / nose lighter).

Don't open the ballonet relief valves too wide or the envelope pressure will drop too low. Monitor the pressure gauges! You might need to rev up the engine to restore the envelope pressure at times (in particular when descending).

==== Ground crew ====

{| class ="keytable"
! Key
! Function
|-
| {{key press|U}}
| Request ground crew to prepare for landing.
|-
| {{key press|Y}}
| Tell ground crew to let go. Do this before you take-off.
|-
| {{key press|Alt}} + click on terrain
| Place the ground crew.
|}

On the prepare-for-landing request the ground crew will align to the current wind conditions. When landing you should aim to approach against the wind and arrive exactly in between the left and right ground teams with very low speed and altitude.

The ground crew is visible over the multiplayer network.

==== Cockpit and instruments ====

[[File:Submarine_Scout_cockpit.jpg]]

Upper row left to right: Airspeed indicator, Compass and Altimeter (Note: The altimeter reads in 100s rather than 1000s feet).

Lower row left to right: Tachometer, Left and right magneto switches, Clinometer, Watch, Pressure gauges for fore ballonet, main envelope and aft ballonet.

==== Armament ====

The Submarine Scout airship is armed with two 65lb bombs. The bombs can be dropped one at the time by actuating the default weapon trigger from the pilot view. Bomb impacts are visible over the multiplayer network.

'''Note:''' By default the weapon trigger is not mapped to any control in FlightGear. However, most joystick configurations put it on a button or a button + key combination.

==== ALDIS signalling lamp ====

[[File:Submarine Scout ALDIS lamp.jpg]]

The observer view has an ALDIS lamp for morse code signalling. The ALDIS lamp can be picked up or stowed in the observer view by clicking the lamp handle.
The lamp is actuated by the default weapon trigger in all views except the pilot view. The lamp state is visible over the multiplayer network.

=== Airship piloting ===

==== Static controls ====

* Buoyancy
* Weight
* Envelope pressure
* Trim

===== Checking the static condition =====

There is no instrument on the Submarine Scout that directly show if the airship is light or heavy and what the static trim is. To see you have to reduce throttle to idle and wait for the speed to decrease. As the aerodynamic forces diminish the airship will start to rise or descent depending on its lightness/heaviness and its pitch attitude will show how nose/tail heavy it is.

To some extent the lightness/heaviness is also apparent in how the 'ship handles at speed - a heavy 'ship requires a nose up attitude to maintain altitude - while a light ship requires a nose down attitude.

==== Dynamic controls ====

* Rudder
* Elevator
* Throttle

=== Basic manoeuvres ===

==== Take-off ====

* Set ballonet valves to 0%/2% (fore/aft). This will slowly make the ship more nose heavy which is suitable for cruise.
* Tell ground crew to let go (Y).
* Check weight (w) and weigh off (W) as necessary. 50 lbs or less is a good take off heaviness. Note that each weigh off takes 10 seconds to complete.
* Start engine (magnetos on + s).
* Take off at full power and a nose up attitude.
* When the nose starts to swing up use some down elevator to increase(!) lift and avoid a tail strike.

==== Landing ====

Note: You can position the ground crew by Alt+click on the terrain.

* Check static condition and trim: Neutral trim and slightly heavy is better than light. Check the static condition and trim by stopping the engine and note whether the airship raises or falls as the airspeed drops off and what pitch attitude it tends towards.
* Prepare the ground crew (U). They will (re)position themselves facing the wind.
* Approach is against the wind, low (~150ft) and slow.
* Aim to arrive between the handling parties, below 100ft and with very little ground speed.
* The ground crew uses the handling guys to secure the ship.

[[File:Submarine Scout landing.jpg]]

== Installation and Dependencies ==

* Submarine Scout ([http://github.com/andgi/FlightGear-Submarine_Scout FG/git]) or in the official [[FGAddon]] (needs [[Sopwith Camel]] installed but fetching instruments from there seems not to work now in 2025).

== Known problems ==

* The ground handling force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Set /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* (FlightGear 1.9.x) Unfortunately the envelope isn't initialized in a pressurized state. The ballonet valves are set for inflation so the operating pressure is usually reached within a short time.

* (FlightGear 1.9.x) Obsolete copies of <tt>mp_broadcast.nas</tt> (e.g. from the WildFire or Air racing add-ons) could cause problems. The up to date version now resides in <tt>[[$FG_ROOT]]/Nasal/mp_broadcast.nas</tt>. Remove the others - there should be no need for them.

== External links ==
* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or FlightGear/git. '''Note: The most up to date version of the Submarine Scout is available in FlightGear/git.'''
* [http://www.aht.ndirect.co.uk/airships/ss/index.html Submarine Scout Class information at the Airship Heritage Trust]

{{Aerostat}}

Submarine Scout

2025-04-30T18:48:10Z

AndersG: /* Installation and Dependencies */ Added a PROBLEM statement.

{{:{{PAGENAME}}/info}}
The '''Submarine Scout''' was a fairly small blimp, i.e. non-rigid airship, which was used for maritime patrol and convoy escort by the Royal Naval Air Service (RNAS) during World War I. The type first flew in 1915 and was in service throughout the rest of the war.
The early versions had cars made from slightly modified aeroplane fuselages; the final version, Submarine Scout Zero represented here, had a purpose built car.

== Handling instructions ==

=== Important controls / keys / instruments ===

==== Flight controls ====

* Rudder (Aileron input is transferred to the rudder for convenience.)
* Elevator

In the real aircraft the pilot had rudder pedals for the rudder and an elevator wheel located in front of him (with its axis across the cockpit) for the elevators.

==== Ballast ====

{| class="keytable"
! Key
! Function
|-
| {{key press|W}}
| Weigh-off to 50 lbs heavy by adjusting ballast. Takes about 10 seconds and only works when on the ground.
|-
| {{key press|w}}
| Show current on-ground weight. Only works when on the ground.
|-
| {{key press|D}}/{{key press|d}}
| Drop ballast in 1%/0.1% decrements. (Rarely used.)
|}

This type of blimp normally operates from about 100 lbs heavy to a few 100 lbs light.

==== Gas and Envelope ====

{| class="keytable"
! Key
! Function
|-
| {{key press|F}}/{{key press|f}}
| Open/close the gas valve.
|-
| {{key press|Q}}/{{key press|q}}
| Open/close fore ballonet relief valve.
|-
| {{key press|A}}/{{key press|a}}
| Open/close aft ballonet relief valve.
|-
| {{key press|Ctrl|Q}}
| Open/close fore ballonet inflow valve.
|-
| {{key press|Ctrl|A}}
| Open/close aft ballonet inflow valve.
|}

The fore and aft ballonets (air-filled bags inside the envelope) serve two purposes: (i) by inflating/deflating they maintain the pressure differential and volume of the envelope when the gas changes volume (mainly due to altitude changes); and (ii) the trim of the airship can be changed by the relative inflation of the ballonets. While the required envelope pressure dictate the total volume of the ballonets the airship can be trimmed by having one ballonet more or less inflated than the other.

The ballonets are inflated by air from the propeller slip stream, collected with the scoop and passed via fabric trunks and closeable no-return valves to the ballonets. The ballonet relief valve automatically open when the pressure in the ballonet exceeds a set limit (which is lower than that of the gas relief valve to prevent gas being valved before both ballonets are empty).
Maintain the envelope pressure at about 15 - 25mm water, shown by the height difference between the outer and inner fluid in the manometers (which have no scale yet!).

The gas valve is basically only used to valve some gas if the airship is found too light during the pre-landing weigh off.

In the version released with FlightGear 1.9.0/1 both ballonets continuously received a constant in-flow of air instead. The degree of inflation (and total pressure) is controlled by "bleeding" more or less air from either ballonet relief valve.

To trim towards:
* nose heavy - open the fore ballonet inflow valve and the aft ballonet relief valve (nose gets heavier / tail lighter).
* tail heavy - open the aft ballonet inflow valve and the fore ballonet valve more (tail gets heavier / nose lighter).

Don't open the ballonet relief valves too wide or the envelope pressure will drop too low. Monitor the pressure gauges! You might need to rev up the engine to restore the envelope pressure at times (in particular when descending).

==== Ground crew ====

{| class ="keytable"
! Key
! Function
|-
| {{key press|U}}
| Request ground crew to prepare for landing.
|-
| {{key press|Y}}
| Tell ground crew to let go. Do this before you take-off.
|-
| {{key press|Alt}} + click on terrain
| Place the ground crew.
|}

On the prepare-for-landing request the ground crew will align to the current wind conditions. When landing you should aim to approach against the wind and arrive exactly in between the left and right ground teams with very low speed and altitude.

The ground crew is visible over the multiplayer network.

==== Cockpit and instruments ====

[[File:Submarine_Scout_cockpit.jpg]]

Upper row left to right: Airspeed indicator, Compass and Altimeter (Note: The altimeter reads in 100s rather than 1000s feet).

Lower row left to right: Tachometer, Left and right magneto switches, Clinometer, Watch, Pressure gauges for fore ballonet, main envelope and aft ballonet.

==== Armament ====

The Submarine Scout airship is armed with two 65lb bombs. The bombs can be dropped one at the time by actuating the default weapon trigger from the pilot view. Bomb impacts are visible over the multiplayer network.

'''Note:''' By default the weapon trigger is not mapped to any control in FlightGear. However, most joystick configurations put it on a button or a button + key combination.

==== ALDIS signalling lamp ====

[[File:Submarine Scout ALDIS lamp.jpg]]

The observer view has an ALDIS lamp for morse code signalling. The ALDIS lamp can be picked up or stowed in the observer view by clicking the lamp handle.
The lamp is actuated by the default weapon trigger in all views except the pilot view. The lamp state is visible over the multiplayer network.

=== Airship piloting ===

==== Static controls ====

* Buoyancy
* Weight
* Envelope pressure
* Trim

===== Checking the static condition =====

There is no instrument on the Submarine Scout that directly show if the airship is light or heavy and what the static trim is. To see you have to reduce throttle to idle and wait for the speed to decrease. As the aerodynamic forces diminish the airship will start to rise or descent depending on its lightness/heaviness and its pitch attitude will show how nose/tail heavy it is.

To some extent the lightness/heaviness is also apparent in how the 'ship handles at speed - a heavy 'ship requires a nose up attitude to maintain altitude - while a light ship requires a nose down attitude.

==== Dynamic controls ====

* Rudder
* Elevator
* Throttle

=== Basic manoeuvres ===

==== Take-off ====

* Set ballonet valves to 0%/2% (fore/aft). This will slowly make the ship more nose heavy which is suitable for cruise.
* Tell ground crew to let go (Y).
* Check weight (w) and weigh off (W) as necessary. 50 lbs or less is a good take off heaviness. Note that each weigh off takes 10 seconds to complete.
* Start engine (magnetos on + s).
* Take off at full power and a nose up attitude.
* When the nose starts to swing up use some down elevator to increase(!) lift and avoid a tail strike.

==== Landing ====

Note: You can position the ground crew by Alt+click on the terrain.

* Check static condition and trim: Neutral trim and slightly heavy is better than light. Check the static condition and trim by stopping the engine and note whether the airship raises or falls as the airspeed drops off and what pitch attitude it tends towards.
* Prepare the ground crew (U). They will (re)position themselves facing the wind.
* Approach is against the wind, low (~150ft) and slow.
* Aim to arrive between the handling parties, below 100ft and with very little ground speed.
* The ground crew uses the handling guys to secure the ship.

[[File:Submarine Scout landing.jpg]]

== Installation and Dependencies ==

* Submarine Scout ([http://github.com/andgi/FlightGear-Submarine_Scout FG/git]) or in the official [[FGAddon]].

'''PROBLEM This does not seem to work now in 2025:''' This aircraft depends on instruments from some other aircraft. Install a matching version of these too.

* [[Sopwith Camel]]

== Known problems ==

* The ground handling force calculations are sensitive to long frame times (i.e. very low fps), which can cause FlightGear to crash during startup or make the airship start in a bad state.
'''Workaround''': Set /sim/max-simtime-per-frame to 0.1 seconds or less. This can be done in preferences.xml by modifying the line
<max-simtime-per-frame>1.0</max-simtime-per-frame>
to
<max-simtime-per-frame>0.1</max-simtime-per-frame>

* (FlightGear 1.9.x) Unfortunately the envelope isn't initialized in a pressurized state. The ballonet valves are set for inflation so the operating pressure is usually reached within a short time.

* (FlightGear 1.9.x) Obsolete copies of <tt>mp_broadcast.nas</tt> (e.g. from the WildFire or Air racing add-ons) could cause problems. The up to date version now resides in <tt>[[$FG_ROOT]]/Nasal/mp_broadcast.nas</tt>. Remove the others - there should be no need for them.

== External links ==
* [http://www.gidenstam.org/FlightGear/Airships/ Download page with other lighter-than-air aircraft for FlightGear.] Requires the LTA support available in FlightGear 1.9.0 or FlightGear/git. '''Note: The most up to date version of the Submarine Scout is available in FlightGear/git.'''
* [http://www.aht.ndirect.co.uk/airships/ss/index.html Submarine Scout Class information at the Airship Heritage Trust]

{{Aerostat}}

Swedish Navy T21 class MTB

2022-06-12T11:07:14Z

AndersG: /* Engine controls */

{{:{{PAGENAME}}/info}}
The Swedish Navy T21 class motor torpedo boat were the second Swedish MTB class developed during the first years of WWII. The design was provided by the Italian companies Baglietto and CRDA but the 11 boats were manufactured at the Kockums shipyard in Sweden during 1942-43. They remained in service until the late 1950s, and some were retained for special purposes much longer. At least one remains today, T26, which has been restored to service condition, and as the hulls of some of others were sold on the civilian market after being decommissioned there might still be some other hulls around.

The 20 m long boats were powered by two 1500 hp Isotta Fraschini IF184 supercharged petrol engines giving a top speed of about 50 knots. The armament consisted of two 53 cm torpedoes and a 20 mm AA cannon.

== Handling and controls ==

=== Engine controls ===

The MTB is equipped with two 1500 hp Isotta Fraschini IF184 main engines and two auxiliary Ford V8 engines for low speed manoeuvring. One main engine and one auxiliary engine is connected to each of the two propellers via gearboxes and clutches.

'''Main Engine Start'''
# Disengage the main engine clutches ({{Key press|Q}}). This action also selects the two main engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH (''three times on'' {{Key press|}}}).
# Start the engines ({{Key press|s}}).
# Engage the main engine clutches ({{Key press|q}}). This action also selects the two main engines.

'''Auxiliary Engine Start'''
# Disengage the auxiliary engine clutches ({{Key press|E}}). This action also selects the two auxiliary engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH (''three times on'' {{Key press|}}}).
# Start the engines ({{Key press|s}}).
# Engage the auxiliary engine clutches ({{Key press|e}}). This action also selects the two auxiliary engines.

Be careful to avoid over-speeding an engine with a disengaged clutch.

== Installation and Dependencies ==

* Swedish Navy T21 class MTB (a.k.a. MTB_20m) ({{github source|user=andgi|repo=FlightGear-MTB_20m|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-MTB_20m|text=Download ZIP}}".)

This "aircraft" depends on instruments and sounds from some other aircraft. Install a matching version of these too.
* [[Zeppelin_LZ_121_Nordstern|Nordstern]] ({{fgaddon aircraft source|Nordstern|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Nordstern|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Nordstern|text=Download ZIP}}".)
* [[Short_Empire]] ({{fgaddon aircraft source|Short_Empire|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Short_Empire|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Short_Empire|text=Download ZIP}}".)
* [[North American P-51 Mustang|P-51D Mustang]] ({{fgaddon aircraft source|p51d|text=FGAddon}})
* [[Cessna 172P]] (included with FlightGear)

== Known problems ==

* The hydrodynamics planing model often reacts poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain. Quickly reducing speed may help.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. On some systems this appears to have a considerable impact on the frame rate.

Swedish Navy T21 class MTB

2022-06-12T11:03:55Z

AndersG: /* Engine controls */

{{:{{PAGENAME}}/info}}
The Swedish Navy T21 class motor torpedo boat were the second Swedish MTB class developed during the first years of WWII. The design was provided by the Italian companies Baglietto and CRDA but the 11 boats were manufactured at the Kockums shipyard in Sweden during 1942-43. They remained in service until the late 1950s, and some were retained for special purposes much longer. At least one remains today, T26, which has been restored to service condition, and as the hulls of some of others were sold on the civilian market after being decommissioned there might still be some other hulls around.

The 20 m long boats were powered by two 1500 hp Isotta Fraschini IF184 supercharged petrol engines giving a top speed of about 50 knots. The armament consisted of two 53 cm torpedoes and a 20 mm AA cannon.

== Handling and controls ==

=== Engine controls ===

The MTB is equipped with two 1500 hp Isotta Fraschini IF184 main engines and two auxiliary Ford V8 engines for low speed manoeuvring. One main engine and one auxiliary engine is connected to each of the two propellers via gearboxes and clutches.

'''Main Engine Start'''
# Disengage the main engine clutches ({{Key press|Q}}). This action also selects the two main engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH ({{Key press|}}}).
# Start the engines ({{Key press|s}}).
# Engage the main engine clutches ({{Key press|q}}). This action also selects the two main engines.

'''Auxiliary Engine Start'''
# Disengage the auxiliary engine clutches ({{Key press|E}}). This action also selects the two auxiliary engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH ({{Key press|}}}).
# Start the engines ({{Key press|s}}).
# Engage the auxiliary engine clutches ({{Key press|e}}). This action also selects the two auxiliary engines.

Be careful to avoid over-speeding an engine with a disengaged clutch.

== Installation and Dependencies ==

* Swedish Navy T21 class MTB (a.k.a. MTB_20m) ({{github source|user=andgi|repo=FlightGear-MTB_20m|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-MTB_20m|text=Download ZIP}}".)

This "aircraft" depends on instruments and sounds from some other aircraft. Install a matching version of these too.
* [[Zeppelin_LZ_121_Nordstern|Nordstern]] ({{fgaddon aircraft source|Nordstern|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Nordstern|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Nordstern|text=Download ZIP}}".)
* [[Short_Empire]] ({{fgaddon aircraft source|Short_Empire|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Short_Empire|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Short_Empire|text=Download ZIP}}".)
* [[North American P-51 Mustang|P-51D Mustang]] ({{fgaddon aircraft source|p51d|text=FGAddon}})
* [[Cessna 172P]] (included with FlightGear)

== Known problems ==

* The hydrodynamics planing model often reacts poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain. Quickly reducing speed may help.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. On some systems this appears to have a considerable impact on the frame rate.

Swedish Navy T21 class MTB

2022-06-12T11:03:16Z

AndersG: /* Engine controls */ Added more keys.

{{:{{PAGENAME}}/info}}
The Swedish Navy T21 class motor torpedo boat were the second Swedish MTB class developed during the first years of WWII. The design was provided by the Italian companies Baglietto and CRDA but the 11 boats were manufactured at the Kockums shipyard in Sweden during 1942-43. They remained in service until the late 1950s, and some were retained for special purposes much longer. At least one remains today, T26, which has been restored to service condition, and as the hulls of some of others were sold on the civilian market after being decommissioned there might still be some other hulls around.

The 20 m long boats were powered by two 1500 hp Isotta Fraschini IF184 supercharged petrol engines giving a top speed of about 50 knots. The armament consisted of two 53 cm torpedoes and a 20 mm AA cannon.

== Handling and controls ==

=== Engine controls ===

The MTB is equipped with two 1500 hp Isotta Fraschini IF184 main engines and two auxiliary Ford V8 engines for low speed manoeuvring. One main engine and one auxiliary engine is connected to each of the two propellers via gearboxes and clutches.

'''Main Engine Start'''
# Disengage the main engine clutches ({{Key press|Q}}). This action also selects the two main engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH ({{Key press|\}}}).
# Start the engines ({{Key press|s}}).
# Engage the main engine clutches ({{Key press|q}}). This action also selects the two main engines.

'''Auxiliary Engine Start'''
# Disengage the auxiliary engine clutches ({{Key press|E}}). This action also selects the two auxiliary engines.
# Mixture rich ({{Key press|m}}).
# Magnetos BOTH ({{Key press|\}}}).
# Start the engines ({{Key press|s}}).
# Engage the auxiliary engine clutches ({{Key press|e}}). This action also selects the two auxiliary engines.

Be careful to avoid over-speeding an engine with a disengaged clutch.

== Installation and Dependencies ==

* Swedish Navy T21 class MTB (a.k.a. MTB_20m) ({{github source|user=andgi|repo=FlightGear-MTB_20m|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-MTB_20m|text=Download ZIP}}".)

This "aircraft" depends on instruments and sounds from some other aircraft. Install a matching version of these too.
* [[Zeppelin_LZ_121_Nordstern|Nordstern]] ({{fgaddon aircraft source|Nordstern|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Nordstern|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Nordstern|text=Download ZIP}}".)
* [[Short_Empire]] ({{fgaddon aircraft source|Short_Empire|text=FGAddon}}/{{github source|user=andgi|repo=FlightGear-Short_Empire|text=GitHub}}, click "{{github zip file|user=andgi|repo=FlightGear-Short_Empire|text=Download ZIP}}".)
* [[North American P-51 Mustang|P-51D Mustang]] ({{fgaddon aircraft source|p51d|text=FGAddon}})
* [[Cessna 172P]] (included with FlightGear)

== Known problems ==

* The hydrodynamics planing model often reacts poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain. Quickly reducing speed may help.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. On some systems this appears to have a considerable impact on the frame rate.

Howto:Modelling hydrodynamics in JSBSim

2022-03-31T08:18:55Z

AndersG: /* Examples */ Switched the link to the Gokstad ship to the wiki page.

== Introduction ==

This page intends to describe how to model hydrodynamic forces and moments in JSBSim (i.e. how things interact with water).
It is based around JSBSim external forces and a couple of generic systems for JSBSim that are available in FGData, namely [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamics.xml hydrodynamics.xml], [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing.xml hydrodynamic-planing.xml] and [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing-floats.xml hydrodynamic-planing-floats.xml].

'''''NOTE:''' These methods and systems are under active, but slow development, there are known and unknown bugs and inconsistencies present. Future developments may require changes in the per-aircraft files.''

The [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamics.xml hydrodynamics.xml] system receives forces and moments due to the vessel's interaction with water, both hydrostatic and hydrodynamic, defined with respect to the hydrodynamic reference point (HRP) in a separate per-aircraft file and apply them to the vessel using external forces.

The coordinate frame used to define the forces and moments is similar to the body frame but is always aligned with the water surface which is assumed to be horizontal. Forces can also be defined in a horizontal "wind" frame.

'''''NOTE:''' This is one point where there are known inconsistencies present (read: the coordinate frame definitions need to be sorted out). However, as long as pitch and heel angles are small this should not lead to major issues.''

The forces are split into the channels
* '''Fbx''' - body forward. (In the water plane?)
* '''Fby''' - body right. (In the water plane?)
* '''Fbz''' - local up (the same as -Z in the JSBSim local frame).
* '''Drag''' - opposing the relative water flow. (In the water plane?)
* '''Side''' - 90 degrees right from the relative water flow in the surface plane.

The moments are split into the hydrodynamic body frame channels
(with the same sense as the normal body frame moments):
* '''Pitch''' (angle: positive is nose up)
* '''Yaw'''
* '''Roll''' (angle and moment: positive is left wing up)

The properties determining the location and orientation of the vessel w.r.t the the water surface and stream are:
* <tt>hydro/height-agl-ft</tt> - Height of the hydrodynamic reference point over the water surface.
* <nowiki>hydro/beta-deg</nowiki> - angle between the vessel's velocity vector through the water and its longitudinal axis. Analogous to aerodynamics/beta-deg.
* <nowiki>hydro/pitch-deg</nowiki> - angle between the vessel longitudinal axis and the water surface (ground plane).
* <nowiki>hydro/roll-deg</nowiki> - angle between the vessel transverse axis and the water surface (ground plane).
* <nowiki>hydro/v-fps</nowiki> - The vessel's total speed relative the water.

== Basic usage ==

Include the [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamics.xml hydrodynamics.xml] system in your vessel/aircraft.

Define the following properties in a system of your aircraft:
* Hydrodynamics reference point in the structural frame:
<syntaxhighlight lang="xml">
<property value="...">metrics/hydro-rp-x-in</property>
<property value="...">metrics/hydro-rp-y-in</property>
<property value="...">metrics/hydro-rp-z-in</property>
</syntaxhighlight>
* Reference dimensions (used for the experimental wave interactions, but may also be used as reference dimensions for hydrodynamic coefficients in the aircraft specific system):
<syntaxhighlight lang="xml">
<property value="...">metrics/hydro-beam-ft</property>
<property value="...">metrics/hydro-length-ft</property>
<property value="...">hydro/hull-length-ft</property> 
</syntaxhighlight>
* Functions computing the forces in the hydrodynamic body frame
- hydro/fbx-lbs
- hydro/fby-lbs
- hydro/fbz-lbs
Alternative force inputs in the water frame
- hydro/fdrag-lbs
- hydro/fside-lbs
Unused properties also have to be declared (and set to zero).

* Functions computing the moments in the hydrodynamic body frame. '''''FIXME''': Yaw is applied in the standard body frame.''
- hydro/yaw-moment-lbsft
- hydro/pitch-moment-lbsft
- hydro/roll-moment-lbsft

Define the following external forces in the main FDM file of your aircraft, they will be used to apply the hydrodynamic forces and moments to the vessel:
<syntaxhighlight lang="xml">
<force name="hydro-X" frame="LOCAL">
<location unit="M">
{ HRP }
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="hydro-Y" frame="LOCAL">
<location unit="M">
{ HRP }
</location>
<direction>
<x> 0.0 </x>
<y> 1.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="hydro-Z" frame="LOCAL">
<location unit="M">
{ HRP }
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>

<force name="hydro-pitch[0]" frame="LOCAL">
<location unit="M">
<x> HRP X - 0.3048 </x>
<y> HRP Y </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>
<force name="hydro-pitch[1]" frame="LOCAL">
<location unit="M">
<x> HRP X + 0.3048 </x>
<y> HRP Y </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>

<force name="hydro-yaw[0]" frame="BODY">
<location unit="M">
<x> HRP X </x>
<y> HRP Y - 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="hydro-yaw[1]" frame="BODY">
<location unit="M">
<x> HRP X </x>
<y> HRP Y + 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>

<force name="hydro-roll[0]" frame="LOCAL">
<location unit="M">
<x> HRP X </x>
<y> HRP Y - 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>
<force name="hydro-roll[1]" frame="LOCAL">
<location unit="M">
<x> HRP X </x>
<y> HRP Y + 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>
</syntaxhighlight>

== Generating hydrostatic buoyancy coefficients ==

To make something float with the hydrodynamics system the buoyancy forces and moments need to be computed and then input to the generic part of the system as shown above. One way to compute these forces and moments is to generate buoyancy coefficients as functions of (read: tables indexed by) the position and orientation of the vessel/aircraft relative to the surface of the water it floats on.

Such tables can be generated by using the [http://gfs.sourceforge.net/wiki/index.php/Main_Page Gerris flow solver] (a case of using a sledgehammer on a roofing nail). My [https://github.com/andgi/FlightGear-MFI-9/tree/master/dev/fdm/gerris MFI-9B development repository] contain a short description and a set of scripts to do this. ''''This part will be extended later.''''

[[File:GfsView3d.jpg|thumb|600px|center|One Gerris buoyancy case for a float of the MFI-9B float-plane visualized in the Gerris gfsview3d tool. The water line is at the edge of the dark blue colour. It looks curved due to the various levels of cell refinement over the domain.]]

Out of Gerris and the scripts we get (not quite) dimensionless coefficients that can be used to compute forces and moments in a JSBSim hydrodynamics configuration.

As an example, take the buoyancy function for the left float on the MFI-9B aircraft, shown below. The coefficient table is indexed by the the position and orientation of the float relative to the surface of the water and encodes the size, shape and position of the float (i.e. it is not completely dimensionless so it can't be resized using reference dimensions). It is redimensioned using the density of the fluid and the local gravitational acceleration, so it can e.g. be used in both fresh and sea water by adjusting the density property.

<syntaxhighlight lang="xml">
<fcs_function name="hydro/buoyancy-lbs[0]">
<description>
Lift due to buoyancy.
This data was computed in Gerris using the 3d model.
</description>
<function>
<product>
<value>1.0</value>
<property>hydro/environment/rho-slug_ft3</property>
<property>hydro/environment/gravity-ft_sec2</property>
<table>
<independentVar lookup="row">hydro/floats/height-agl-ft[0]</independentVar>
<independentVar lookup="column">hydro/floats/pitch-deg[0]</independentVar>
<tableData>
-8.0 -4.0 -2.0 0.0 2.0 4.0 8.0 12.0 16.0
0.0 16.317 17.6619 18.8259 19.3889 19.1313 17.4748 15.2858 12.89 11.9824
0.5 13.2014 13.1521 12.8704 11.7539 11.5822 11.5332 10.4907 9.50575 8.9009
1.0 8.0404 5.33223 3.92246 3.12018 2.64237 2.62089 4.33869 5.18165 5.77791
1.1 6.78179 3.91069 2.77708 2.00604 1.53587 1.4586 3.02049 4.37883 5.01463
1.2 5.5826 2.69964 1.70293 1.11212 0.812872 0.738275 2.41573 3.65025 4.44103
1.3 4.21802 1.72272 0.982204 0.597546 0.364947 0.28255 0.870549 2.91068 3.86057
1.4 3.35104 0.98356 0.483655 0.222508 0.133908 0.0969449 0.313928 2.0523 3.39795
1.5 2.2106 0.456154 0.138342 0.0602531 0.0470096 0.0472367 0.0727965 1.47347 3.0011
1.6 1.32999 0.127043 0.0293268 0.0398354 0.0431891 0.0431979 0.0422914 0.920714 2.4331
1.7 0.737418 0.0299295 0.0424416 0.0421912 0.0425591 0.0435274 0.0474329 0.662184 1.94144
1.8 0.318676 0.042442 0.0489618 0.0490367 0.0486102 0.0483223 0.0458598 0.263176 1.55605
1.9 0.0971646 0.0458687 0.0465963 0.0487801 0.0482579 0.0475844 0.0456543 0.104628 1.22239
2.0 0.0333578 0.045529 0.0473602 0.0491747 0.0461851 0.04672 0.0462562 0.0481988 0.895087
2.5 0.0421991 0.0446028 0.0459248 0.0454018 0.0452878 0.0445737 0.0438382 0.0413723 0.0452297
3.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
</tableData>
</table>
</product>
</function>
</fcs_function>
</syntaxhighlight>

''''To be continued... for now, see [https://github.com/andgi/FlightGear-MFI-9/tree/master/ the MFI-9B development repository]. ''''

== Modelling hydrodynamic coefficients ==

The hydrostatic coefficients described above allow the vessel to float, so the next problem is to make it move through the water. Starting with drag there are different modes of movement on the water, namely
* displacement, the vessel pushing through the water;
* planing, the vessel skimming along the surface of the water pushing down on it rather than through it; and
* semi-planing, a mix of the above.

For a non-planing vessel the drag is roughly proportional to the square of the speed through the water while a planing vessel has much more complicated drag function as it goes through displacement, semi-planing and planing phases as speed increases.

As an example consider the plot below of the towing power (drag times velocity) of a [[Swedish Navy T21 class MTB]] as speed increases from 0 to nearly 60 knots. The blue line is from a real tow tank test ("Resultat av släpförsök med svenska patent nr. 109626", A. F. Nordström, Statens Skeppsprovningsanstalt, Göteborg, 1941-10-01) and shows the complex shape of the drag function. One can guess that the curve up to about 10 knots is mostly due to quadratic displacement drag. Above this speed the vessel enters the planing phase and the displacement is reduced as more and more of the weight is supported by the planing forces. This reduces the increase in drag considerably. Finally, from about 38 knots and over another quadratic growth phase takes over. My hypothesis is that this phase is due to the rudders that remain in the water and ought to have (from standard fluid dynamics) a rather small but quadratic drag curve.

The actual physics of planing is very complex and the exact shape of the planing surfaces and the trim of the vessel play a large role in determining the drag (and other forces). The approach taken here to model this in JSBSim is very much simplified, using just a few functions and a handful of tuning parameters to estimate the hydrodynamic forces. For cases where appropriate and comprehensive tow test data exists coefficient tables could instead be extracted from that.

[[File:Swedish Navy T21 class MTB-drag.png|thumb|600px|center|Hydrodynamic drag of a MTB after ad hoc tuning. Total (green) and parts, displacement (red), planing (cyan) and rudder assembly (purple), of the hydrodynamic drag of the [[Swedish Navy T21 class MTB]] from a single acceleration run in JSBSim/standalone. The blue line is a real tow tank result traced from a diagram in "Resultat av släpförsök med svenska patent nr. 109626", A. F. Nordström, Statens Skeppsprovningsanstalt, Göteborg, 1941-10-01 available as an image (ID 2008:25:869:1) from Sjöhistoriska museet under CC BY-SA.]]

Firstly, the displacement drag is modelled through two functions: one for the hull and one for the rudders. The hull displacement drag is defined as follows:
<syntaxhighlight lang="xml">
<fcs_function name="hydro/displacement-drag-lbs">
<function>
<description>Drag due to displacement of hull</description>
<product>
<value>0.0000017</value> 
<property>hydro/qbar-psf</property>
<property>hydro/hull-beam-ft2</property>
<property>hydro/buoyancy-lbs</property>
<sum>
<value>1.0</value>
<product> 
<value>10.0</value>
<abs><sin><property>hydro/beta-rad</property></sin></abs>
</product>
</sum>
</product>
</function>
</fcs_function>
</syntaxhighlight>
There are a couple of things to note:
* The force is scaled by the displacement, so it will decrease as the planing forces increase and lifts the hull towards the water surface.
* The force is crudely increased as the beta angle increases (the drag increases when "side slipping" through the water, but in this case there is no data to base the increment on).
* The Cd per lbs displacement and ft^2 of hull cross section value has been tuned to the graph above, but it was also necessary to modify the static buoyancy/displacement lift function to decrease it faster with speed to get a decent match (among other things this simplified model computes the buoyancy based on the undisturbed water level and, further, at planing speeds the interface between the hull and the water is very different from at slower speeds).

The rudder drag function, on the other hand, is simpler (Cd has been tuned to the graph above while the rudder angle penalty is just guessed):
<syntaxhighlight lang="xml">
<fcs_function name="hydro/rudder-drag-lbs">
<function>
<description>Drag due to rudders (not reduced by planing)</description>
<product>
<value>0.0036</value> 
<property>hydro/qbar-psf</property>
<property>hydro/hull-beam-ft2</property>
<sum>
<value>1.0</value>
<product> 
<value>10.0</value>
<abs><property>fcs/rudder-pos-norm</property></abs>
</product>
</sum>
</product>
</function>
</fcs_function>
</syntaxhighlight>

The third component of the drag is due to planing. The planing force and moments are computed by the generic [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing.xml hydrodynamic-planing.xml] system. The system is based on a (simple) model of planing described in (H. Wagner, "Planing of Watercraft", 1933, translated from German as NACA-TM-1139 in 1948) which models the normal force created by a flat planing surface.

The system is set up by providing geometric information about the location of the planing surfaces (assumed to be 3) in the hydro RP frame and two tuning parameters per surface, a scaling factor for the normal force and an additional skin friction coefficient (per ft^2 of planing surface below the undisturbed water line).
<syntaxhighlight lang="xml">
<system file="hydrodynamic-planing">


<property value="27.20">hydro/planing/forebody-length-ft</property>
<property value="14.76">hydro/planing/forebody-beam-ft</property>
<property value="-7.28">hydro/planing/forebody-keel-z-ft</property>
<property value="-12.17">hydro/planing/forebody-end-x-ft</property>
... 

<property value="0.95">hydro/planing/forebody-normal-force-factor</property>
<property value="0.90">hydro/planing/middlebody-normal-force-factor</property>
<property value="0.85">hydro/planing/afterbody-normal-force-factor</property>

<property value="0.001">hydro/planing/forebody-skin-friction-coefficient</property>
<property value="0.001">hydro/planing/middlebody-skin-friction-coefficient</property>
<property value="0.001">hydro/planing/afterbody-skin-friction-coefficient</property>
</system>
</syntaxhighlight>
The system outputs lift, drag (Fbx) and side (Fby) forces as well as pitch and roll moments (yaw is missing presently) that need to be added into the corresponding channels of the craft specific hydrodynamics configuration. A visualization of the configuration is shown in the image below.

[[File:Swedish Navy T21 class MTB-planing-surfaces.jpg|thumb|600px|center|The [[Swedish Navy T21 class MTB]] with the planing surfaces for the hydrodynamic-planing system marked yellow. The marker is placed at hydro RP, the hydrodynamic reference point. Note that the system only supports flat planing surfaces but at planing speeds only the rearmost part of each surface will be in contact with water, anyway.]]

The integration of the planing drag into the craft specific hydrodynamics configuration is shown below. First the drag from the various surfaces is combined.
<syntaxhighlight lang="xml">
<fcs_function name="hydro/planing-drag-lbs">
<function>
<description>Drag due to planing.</description>
<sum>
<property>hydro/planing/forebody-induced-fbx-force-lbs</property>
<property>hydro/planing/middlebody-induced-fbx-force-lbs</property>
<property>hydro/planing/afterbody-induced-fbx-force-lbs</property>
<property>hydro/planing/forebody-friction-fbx-force-lbs</property>
<property>hydro/planing/middlebody-friction-fbx-force-lbs</property>
<property>hydro/planing/afterbody-friction-fbx-force-lbs</property>
</sum>
</function>
</fcs_function>
</syntaxhighlight>
Then it is included in the Body-X or drag channel total. Due to a potential implementation problem in hydrodynamics.xml (probably the coordinate frames issues as mentioned far above) the drag was included in the drag channel rather than in the Body-X channel. When included there it should always be positive (while in the Body-X channel it would almost always be negative), hence the added <abs>-element here.
<syntaxhighlight lang="xml">
<fcs_function name="hydro/fdrag-lbs">
<function>
<product>
<property>hydro/active-norm</property>
<sum>
<property>hydro/displacement-drag-lbs</property>
<property>hydro/rudder-drag-lbs</property>
<abs>
<property>hydro/planing-drag-lbs</property>
</abs>
</sum>
</product>
</function>
</fcs_function>
</syntaxhighlight>

''''To be continued... ''''

== Examples ==

Examples by the author of the generic systems:
* [[Malmö Flygindustri MFI-9]]
* [[Short Empire]]
* [[Gokstad ship]]
* [[Swedish Navy T21 class MTB]]
* {{github url|andgi|FlightGear-Monitor}}
* {{github url|andgi|FlightGear-UB_I}}

Other aircraft
* [[Boeing 314]]
* [[Cessna 172P]]
* [[Piper J3 Cub]]

== Known problems ==

* The hydrodynamic-planing-floats system in FlightGear 2017.1.x and earlier appear to have some wires crossed - the float with the negative y-axis location appears to be on the right side of the aircraft which is not intended. Fixed before 2017.2.x.
* The hydrodynamics planing model often reacts poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain. Quickly reducing speed may help.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. This increases the CPU use by JSBSim (which usually is in the low single digit percent before). On some systems this change in CPU use appears to have a considerable impact on the frame rate while on other systems it has no frame rate impact (i.e. CPU isn't the bottleneck).

{{JSBSim}}
[[Category:Howto]]

Flight Dynamics Model

2022-03-31T08:13:12Z

AndersG: /* Integrated FDMs */

A '''Flight Dynamics Model''' (FDM) is a set of math equations used to calculate the physical forces acting on a simulated [[aircraft]], such as thrust, lift, and drag. Every aircraft simulated by FlightGear must use one of these models. [[FlightGear]] supports several different types of flight dynamics models.

== Flight Dynamic Models ==
=== Integrated FDMs ===
Currently (March 2020) FlightGear comes with these FDMs:

; [[JSBSim]]
: Was originally developed specifically for FlightGear, and has been the default FlightGear flight dynamics model since 2000.
: In addition to airplanes JSBSim also supports rockets, helicopters and [[Aerostat|lighter than air aircraft]] (and to some extent water-craft and land vehicles).
; [[YASim]]
: Is yet another FDM using different calculation methods. YASim supports airplanes and helicopters. It was introduced in FlightGear version 0.7.9 in 2002.

=== Historical FDMs ===
Historically FlightGear have also been able to use these FDMs, but while the source code is still there they are no longer built by default:

; [[LaRCsim]]
: Was originally developed by NASA, and was the first FlightGear FDM, now replaced by JSBSim and YASim.
; [[UIUC]]
: Was developed by the UIUC Applied Aerodynamics Group at University of Illinois, based on LaRCsim.
: It includes additional features, such as the ability to simulate aircraft icing. UIUC lacks ground interaction.

=== Other FDMs ===
There are also other ways to set up an FDM:

; External FDMs:
: FlightGear can also be set up to render using inputs from an external FDM source, such as from [[MATLAB]].
; Custom FDMs
: Other custom FDM have been written for specific aircraft types, such as for hot air balloons.
; [[SpaceFDM]]
: Suggested by several people

== Related content ==
=== Forum topics ===
* {{forum link|s=49|title=Flight Dynamics Model}}

=== Wiki articles ===
* [[FDM engine feature standardization]]
* [[FGPlot]], for built-in runtime plotting of FlightGear properties (including FDM properties) (available in FlightGear 2.11 and later).

=== Source code ===
* {{flightgear source|path=src/FDM}}

{{FDM}}

[[Category:Flight Dynamics Model]]

[[es:FDM]]

JSBSim

2022-03-31T08:04:57Z

AndersG: /* Related content */ Added Bouyant forces and hydrodynamics.

'''JSBSim''' is an open source [[Flight Dynamics Model]] (FDM) software library that models the flight dynamics of an aerospace vehicle. The library has been incorporated into the flight simulation packages [[FlightGear]] and [http://www.openeaagles.org/ OpenEaagles]. It can also be called from a small standalone program to create a batch simulation tool. JSBSim has been in development and use since 1996, and has been built on all of the most popular platforms in use today including those running Linux, Macintosh, and Microsoft Windows operating systems. JSBSim is written in C++ and uses [[File Formats#|XML]] configuration files.

* JSBSim is also used by [[OpenEaagles]]
* [[JSBSim Commander]] is a software program for developing FDM for aircraft with JSBSim.

== Overview ==
JSBSim provides several different physics models which work together to calculate the overall vehicle dynamics.
* [[JSBSim Mass and balance|Mass Balance]] - This model uses weight (mass) to provide a force due to gravity and moments of inertia to damp changes in rotational velocity. Empty mass and inertia are specified, and point masses (which can have a shape and size) and fuel load are added in.

* [[JSBSim GroundReactions|Ground Reactions]] - JSBSim has a fairly simple system for ground reactions. You can have structural contacts which are uni-directional or bogeys which act only in a given direction. Both are modeled as spring and damper systems. Each bogey or structural contact provides a force on the vehicle when in contact with the ground. If the contact is not at the CG it also provides a rotating moment.

* [[JSBSim Engines|Propulsion]] - JSBSim models a variety of engine types using different methods. All engines provide a force along their X axis, and create moments if this force in not applied at the CG. The propeller and rotor thrusters also create turning moments.

* [[JSBSim Aerodynamics|Aerodynamics]] - JSBSim's aerodyamics are a blank slate. It is entirely up to the vehicle author to use valid formulas. The aerodynamic force is divided into Lift, Drag, and Side. You can also create Roll, Pitch and Yaw moments. In addition, if the aerodynamic force reference point is not coincident to the CoG the forces will create a hidden moment.

* [[JSBSim Buoyant forces|Buoyant forces]] - Lighter than air craft, e.g. gas balloons, pressure airships (e.g. blimps) and rigid airships, can be simulated with this model.

* [[JSBSim External forces|External forces]] - If the aerodynamic section is too limiting, or you want to simulate [[Towing|glider tow]] ropes, catapults or other things, you can add forces at arbitrary points.

* [[JSBSim Atmosphere|Atmosphere]] - JSBSim can be set up to use its own atmosphere model, or it can use an externally supplied model. There are three turbulence models to chose from.

* [[JSBSim Systems|Systems]] - A JSBSim system can implement any sort of model. This is a very useful facility as you can have any number of systems referenced from the aircraft configuration file. JSBSim Systems can be used to model items required in the FDM, and non-flight items, such electrics, hydraulics.

* Gravity

== Aeromatic ==

{| style="margin-top:0.1em; margin-bottom:0.1em; margin-left:2em; padding:2px; font-size:95%; text-align:left; background: transparent;"
|-
| [[File:1rightarrow.png|15px]] ''See [[Aeromatic]] for the main article about this subject.''
|}

[http://jsbsim.sourceforge.net/aeromatic2.html Aeromatic] can be used to create aircraft configuration files for use with the JSBSim Flight Dynamics Model. The configuration file format produced using this utility is version 2.0, and is incompatable with older formats because of an extensive overhaul of JSBSim's XML code that occured in December of 2004. Aeromatic is a online web tool, written in PHP, not a standalone program.

You will need at least three files for a complete configuration, an '''aircraft file''' containing information on the aircraft's mass properties, propulsion, flight control, aerodynamic properties, etc., an [http://wiki.flightgear.org/JSBSim_Engines engine file] describing the engine(s), and a [http://wiki.flightgear.org/JSBSim_Thrusters thruster file]. Thrusters can be rotors, propellers, nozzles or direct. All turbine engines use the default "direct" thruster. Piston, electric and turboprops need rotors or propellers. Rockets need nozzles. Aeromatic will generate plausible configuration files for your aircraft using some simplifying assumptions. Note that Aeromatic allows only one type of engine to be defined per aircraft. If you want to mix engine types you'll have to make the necessary changes by hand.

Be careful when tweaking the resulting configuration file, because it's easy to make changes that will result in an unflyable FDM. Common errors are: moving things around so they are not left/right symmetrical, and moving the CG too far away from the AeroRP.

== Related content ==
* [[JSBSim Aerodynamics|JSBSim Aerodynamics notes]]
* [[Aero input and outputs|JSBSim Aerodynamics input and outputs]]
* [[JSBSim GroundReactions]]
* [[JSBSim Engines|JSBSim Engine configuration]]
* [[JSBSim Thrusters|JSBSim Thruster configuration]]
* [[JSBSim Fuel System]]
* [[Howto: Write a fuel system in JSBSim]]
* [[DATCOM|DATCOM, lets you input many more variables than Aeromatic]]
* [[Howto: Setup winch and aerotowing for JSBSim-aircraft]]
* [[Howto: methods to replace the NASAL code with JSBSim code]]
* [[JSBSim Buoyant forces]]
* [[Howto:Modelling hydrodynamics in JSBSim]]

== External links ==
* [http://www.jsbsim.org/ JSBSim web site]
* [https://github.com/JSBSim-Team/jsbsim JSBSim site on github]
* [http://jsbsim.sourceforge.net/JSBSim/annotated.html JSBSim annotated reference] – Though meant for programmers, it also document the JSBSim xml markup language.
* {{cite web
| url = http://jsbsim.sf.net/JSBSimReferenceManual.pdf
| title = JSBSim – An open source, platform-independent, flight dynamics model in C++ (a.k.a. JSBSim Reference Manual v1.0)
| author = Jon S. Berndt and the JSBSim Development Team
| date = 9 July 2011 
| format = pdf
| accessdate = 15 January 2014
}} (WIP)
* {{cite web
| url = http://jsbsim.sourceforge.net/CreatingJSBSimAircraft.pdf
| title = A Journal for the Creation and Refinement of a JSBSim Aircraft Flight Model
| author = Jon S. Berndt
| format = pdf
| accessdate = 15 January 2014
}} Detailed report on an aircraft FDM improvement process.
* [http://jsbsimcommander.sf.net/ JSBSim Commander] (beta)
* [http://jsbsim.sourceforge.net/aeromatic2.html Aeromatic 0.95 (online)]
* [http://build.flightgear.org:8080/job/JSBSim-win/ws/dist/bin/aeromatic.exe AeromatiC++ 3.3.8 (Windows)]
* [http://build.flightgear.org:8080/job/JSBSim/ws/dist/bin/aeromatic AeromatiC++ 3.3.8 (Linux)]
* [http://www.holycows.net/datcom/ DATCOM+]

[[es:JSBSim]]

{{FDM}}

{{JSBSim}}

JSBSim External forces

2022-03-31T08:01:16Z

AndersG: /* Usage examples */ Updated the link to the UB I submarine.

[[JSBSim]] provides a framework for '''external reactions''', or rather "arbitrary forces", because this feature can be used to model a wide variety of forces that act on a vehicle. Some examples include: parachutes, catapult, arresting hook, [[Howto:Implement pushback|pushback]], moorings and hydrodynamic reactions for seaplanes.

=== Frames ===
JSBSim incorporates several frame of reference. For external forces the chosen frame of reference is (only) used to determine the direction of the force. The location of the force, i.e. it's point of application, is always defined in the structural frame.

* '''Body XYZ''' The body frame uses the X axis for forward and aft, with + to the front. The Y axis is side to side with + to the right. The Z axis is up and down, with + being down. The origin of this frame is the Center of Gravity (CG), about which the aircraft forces and moments are summed and the resulting accelerations are integrated to get velocities.
* '''LOCAL XYZ''' The local frame is a world-based frame, with X positive north, Y positive east and Z completing the right handed system positive down towards the center of the Earth.
* '''Wind XYZ''' The wind frame X-axis points directly into the relative wind. The Z-axis is perpendicular to the X-axis, and remains within the aircraft body axis XZ plane (also called the reference plane). The Y-axis completes a right hand coordinate system. The origin of this frame is the AeroRP.

=== Configuration file format: ===
<syntaxhighlight lang="xml">
<external_reactions>

<force name="{string}" frame="{BODY | LOCAL | WIND}">
<location unit="{FT | M | IN}">
<x> {number} </x>
<y> {number} </y>
<z> {number} </z>
</location>
<direction>
<x> {number} </x>
<y> {number} </y>
<z> {number} </z>
</direction>
</force>

</external_reactions>
</syntaxhighlight>

=== Notes ===
* You can adjust the magnitude of the external force by setting the <tt>/fdm/jsbsim/external_reactions/{name}/magnitude</tt> property. This value is in pounds.
* Direction of the force can also be adjusted on the fly, by adjusting the <tt>/fdm/jsbsim/external_reactions/{name}/{x|y|z}</tt> properties.
* Multiple forces can be added.

=== Usage examples ===

External forces can be used to model many phenomena. Some examples:

* Modelling of added mass effects of buoyant airships and balloons. For use see e.g. [[ZLT-NT|Zeppelin NT]].
* Modelling of exhaust thrust for piston engines. For use see e.g. [[P51d|North American P-51 Mustang]].
* Modelling of brake-chutes, spin-chutes etc. For use see e.g. [[Vostok-1|Vostok 1 spacecraft]].
* Modelling of mooring of airships and flying boats. For use see e.g. [[ZLT-NT|Zeppelin NT]].
* Modelling of airport push-back services. For use see e.g. [[747-200|Boeing 747-200]].
* Modelling of hydrodynamics. For use see e.g. [[Short_Empire|Short Empire]].
* Modelling of propulsion for ground vehicles. For use see e.g. [[Followme]].
* Modelling of marine propulsion. For use see e.g. {{github url|andgi|FlightGear-UB_I|text=German type UB I submarine}}.

{{JSBSim}}

Howto:Modelling hydrodynamics in JSBSim

2022-03-31T07:57:17Z

AndersG: /* Examples */ Updated the link to the motor torpedo boat.

== Introduction ==

This page intends to describe how to model hydrodynamic forces and moments in JSBSim (i.e. how things interact with water).
It is based around JSBSim external forces and a couple of generic systems for JSBSim that are available in FGData, namely [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamics.xml hydrodynamics.xml], [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing.xml hydrodynamic-planing.xml] and [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing-floats.xml hydrodynamic-planing-floats.xml].

'''''NOTE:''' These methods and systems are under active, but slow development, there are known and unknown bugs and inconsistencies present. Future developments may require changes in the per-aircraft files.''

The [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamics.xml hydrodynamics.xml] system receives forces and moments due to the vessel's interaction with water, both hydrostatic and hydrodynamic, defined with respect to the hydrodynamic reference point (HRP) in a separate per-aircraft file and apply them to the vessel using external forces.

The coordinate frame used to define the forces and moments is similar to the body frame but is always aligned with the water surface which is assumed to be horizontal. Forces can also be defined in a horizontal "wind" frame.

'''''NOTE:''' This is one point where there are known inconsistencies present (read: the coordinate frame definitions need to be sorted out). However, as long as pitch and heel angles are small this should not lead to major issues.''

The forces are split into the channels
* '''Fbx''' - body forward. (In the water plane?)
* '''Fby''' - body right. (In the water plane?)
* '''Fbz''' - local up (the same as -Z in the JSBSim local frame).
* '''Drag''' - opposing the relative water flow. (In the water plane?)
* '''Side''' - 90 degrees right from the relative water flow in the surface plane.

The moments are split into the hydrodynamic body frame channels
(with the same sense as the normal body frame moments):
* '''Pitch''' (angle: positive is nose up)
* '''Yaw'''
* '''Roll''' (angle and moment: positive is left wing up)

The properties determining the location and orientation of the vessel w.r.t the the water surface and stream are:
* <tt>hydro/height-agl-ft</tt> - Height of the hydrodynamic reference point over the water surface.
* <nowiki>hydro/beta-deg</nowiki> - angle between the vessel's velocity vector through the water and its longitudinal axis. Analogous to aerodynamics/beta-deg.
* <nowiki>hydro/pitch-deg</nowiki> - angle between the vessel longitudinal axis and the water surface (ground plane).
* <nowiki>hydro/roll-deg</nowiki> - angle between the vessel transverse axis and the water surface (ground plane).
* <nowiki>hydro/v-fps</nowiki> - The vessel's total speed relative the water.

== Basic usage ==

Include the [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamics.xml hydrodynamics.xml] system in your vessel/aircraft.

Define the following properties in a system of your aircraft:
* Hydrodynamics reference point in the structural frame:
<syntaxhighlight lang="xml">
<property value="...">metrics/hydro-rp-x-in</property>
<property value="...">metrics/hydro-rp-y-in</property>
<property value="...">metrics/hydro-rp-z-in</property>
</syntaxhighlight>
* Reference dimensions (used for the experimental wave interactions, but may also be used as reference dimensions for hydrodynamic coefficients in the aircraft specific system):
<syntaxhighlight lang="xml">
<property value="...">metrics/hydro-beam-ft</property>
<property value="...">metrics/hydro-length-ft</property>
<property value="...">hydro/hull-length-ft</property> 
</syntaxhighlight>
* Functions computing the forces in the hydrodynamic body frame
- hydro/fbx-lbs
- hydro/fby-lbs
- hydro/fbz-lbs
Alternative force inputs in the water frame
- hydro/fdrag-lbs
- hydro/fside-lbs
Unused properties also have to be declared (and set to zero).

* Functions computing the moments in the hydrodynamic body frame. '''''FIXME''': Yaw is applied in the standard body frame.''
- hydro/yaw-moment-lbsft
- hydro/pitch-moment-lbsft
- hydro/roll-moment-lbsft

Define the following external forces in the main FDM file of your aircraft, they will be used to apply the hydrodynamic forces and moments to the vessel:
<syntaxhighlight lang="xml">
<force name="hydro-X" frame="LOCAL">
<location unit="M">
{ HRP }
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="hydro-Y" frame="LOCAL">
<location unit="M">
{ HRP }
</location>
<direction>
<x> 0.0 </x>
<y> 1.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="hydro-Z" frame="LOCAL">
<location unit="M">
{ HRP }
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>

<force name="hydro-pitch[0]" frame="LOCAL">
<location unit="M">
<x> HRP X - 0.3048 </x>
<y> HRP Y </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>
<force name="hydro-pitch[1]" frame="LOCAL">
<location unit="M">
<x> HRP X + 0.3048 </x>
<y> HRP Y </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>

<force name="hydro-yaw[0]" frame="BODY">
<location unit="M">
<x> HRP X </x>
<y> HRP Y - 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>
<force name="hydro-yaw[1]" frame="BODY">
<location unit="M">
<x> HRP X </x>
<y> HRP Y + 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 1.0 </x>
<y> 0.0 </y>
<z> 0.0 </z>
</direction>
</force>

<force name="hydro-roll[0]" frame="LOCAL">
<location unit="M">
<x> HRP X </x>
<y> HRP Y - 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>
<force name="hydro-roll[1]" frame="LOCAL">
<location unit="M">
<x> HRP X </x>
<y> HRP Y + 0.3048 </y>
<z> HRP Z </z>
</location>
<direction>
<x> 0.0 </x>
<y> 0.0 </y>
<z>-1.0 </z>
</direction>
</force>
</syntaxhighlight>

== Generating hydrostatic buoyancy coefficients ==

To make something float with the hydrodynamics system the buoyancy forces and moments need to be computed and then input to the generic part of the system as shown above. One way to compute these forces and moments is to generate buoyancy coefficients as functions of (read: tables indexed by) the position and orientation of the vessel/aircraft relative to the surface of the water it floats on.

Such tables can be generated by using the [http://gfs.sourceforge.net/wiki/index.php/Main_Page Gerris flow solver] (a case of using a sledgehammer on a roofing nail). My [https://github.com/andgi/FlightGear-MFI-9/tree/master/dev/fdm/gerris MFI-9B development repository] contain a short description and a set of scripts to do this. ''''This part will be extended later.''''

[[File:GfsView3d.jpg|thumb|600px|center|One Gerris buoyancy case for a float of the MFI-9B float-plane visualized in the Gerris gfsview3d tool. The water line is at the edge of the dark blue colour. It looks curved due to the various levels of cell refinement over the domain.]]

Out of Gerris and the scripts we get (not quite) dimensionless coefficients that can be used to compute forces and moments in a JSBSim hydrodynamics configuration.

As an example, take the buoyancy function for the left float on the MFI-9B aircraft, shown below. The coefficient table is indexed by the the position and orientation of the float relative to the surface of the water and encodes the size, shape and position of the float (i.e. it is not completely dimensionless so it can't be resized using reference dimensions). It is redimensioned using the density of the fluid and the local gravitational acceleration, so it can e.g. be used in both fresh and sea water by adjusting the density property.

<syntaxhighlight lang="xml">
<fcs_function name="hydro/buoyancy-lbs[0]">
<description>
Lift due to buoyancy.
This data was computed in Gerris using the 3d model.
</description>
<function>
<product>
<value>1.0</value>
<property>hydro/environment/rho-slug_ft3</property>
<property>hydro/environment/gravity-ft_sec2</property>
<table>
<independentVar lookup="row">hydro/floats/height-agl-ft[0]</independentVar>
<independentVar lookup="column">hydro/floats/pitch-deg[0]</independentVar>
<tableData>
-8.0 -4.0 -2.0 0.0 2.0 4.0 8.0 12.0 16.0
0.0 16.317 17.6619 18.8259 19.3889 19.1313 17.4748 15.2858 12.89 11.9824
0.5 13.2014 13.1521 12.8704 11.7539 11.5822 11.5332 10.4907 9.50575 8.9009
1.0 8.0404 5.33223 3.92246 3.12018 2.64237 2.62089 4.33869 5.18165 5.77791
1.1 6.78179 3.91069 2.77708 2.00604 1.53587 1.4586 3.02049 4.37883 5.01463
1.2 5.5826 2.69964 1.70293 1.11212 0.812872 0.738275 2.41573 3.65025 4.44103
1.3 4.21802 1.72272 0.982204 0.597546 0.364947 0.28255 0.870549 2.91068 3.86057
1.4 3.35104 0.98356 0.483655 0.222508 0.133908 0.0969449 0.313928 2.0523 3.39795
1.5 2.2106 0.456154 0.138342 0.0602531 0.0470096 0.0472367 0.0727965 1.47347 3.0011
1.6 1.32999 0.127043 0.0293268 0.0398354 0.0431891 0.0431979 0.0422914 0.920714 2.4331
1.7 0.737418 0.0299295 0.0424416 0.0421912 0.0425591 0.0435274 0.0474329 0.662184 1.94144
1.8 0.318676 0.042442 0.0489618 0.0490367 0.0486102 0.0483223 0.0458598 0.263176 1.55605
1.9 0.0971646 0.0458687 0.0465963 0.0487801 0.0482579 0.0475844 0.0456543 0.104628 1.22239
2.0 0.0333578 0.045529 0.0473602 0.0491747 0.0461851 0.04672 0.0462562 0.0481988 0.895087
2.5 0.0421991 0.0446028 0.0459248 0.0454018 0.0452878 0.0445737 0.0438382 0.0413723 0.0452297
3.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
</tableData>
</table>
</product>
</function>
</fcs_function>
</syntaxhighlight>

''''To be continued... for now, see [https://github.com/andgi/FlightGear-MFI-9/tree/master/ the MFI-9B development repository]. ''''

== Modelling hydrodynamic coefficients ==

The hydrostatic coefficients described above allow the vessel to float, so the next problem is to make it move through the water. Starting with drag there are different modes of movement on the water, namely
* displacement, the vessel pushing through the water;
* planing, the vessel skimming along the surface of the water pushing down on it rather than through it; and
* semi-planing, a mix of the above.

For a non-planing vessel the drag is roughly proportional to the square of the speed through the water while a planing vessel has much more complicated drag function as it goes through displacement, semi-planing and planing phases as speed increases.

As an example consider the plot below of the towing power (drag times velocity) of a [[Swedish Navy T21 class MTB]] as speed increases from 0 to nearly 60 knots. The blue line is from a real tow tank test ("Resultat av släpförsök med svenska patent nr. 109626", A. F. Nordström, Statens Skeppsprovningsanstalt, Göteborg, 1941-10-01) and shows the complex shape of the drag function. One can guess that the curve up to about 10 knots is mostly due to quadratic displacement drag. Above this speed the vessel enters the planing phase and the displacement is reduced as more and more of the weight is supported by the planing forces. This reduces the increase in drag considerably. Finally, from about 38 knots and over another quadratic growth phase takes over. My hypothesis is that this phase is due to the rudders that remain in the water and ought to have (from standard fluid dynamics) a rather small but quadratic drag curve.

The actual physics of planing is very complex and the exact shape of the planing surfaces and the trim of the vessel play a large role in determining the drag (and other forces). The approach taken here to model this in JSBSim is very much simplified, using just a few functions and a handful of tuning parameters to estimate the hydrodynamic forces. For cases where appropriate and comprehensive tow test data exists coefficient tables could instead be extracted from that.

[[File:Swedish Navy T21 class MTB-drag.png|thumb|600px|center|Hydrodynamic drag of a MTB after ad hoc tuning. Total (green) and parts, displacement (red), planing (cyan) and rudder assembly (purple), of the hydrodynamic drag of the [[Swedish Navy T21 class MTB]] from a single acceleration run in JSBSim/standalone. The blue line is a real tow tank result traced from a diagram in "Resultat av släpförsök med svenska patent nr. 109626", A. F. Nordström, Statens Skeppsprovningsanstalt, Göteborg, 1941-10-01 available as an image (ID 2008:25:869:1) from Sjöhistoriska museet under CC BY-SA.]]

Firstly, the displacement drag is modelled through two functions: one for the hull and one for the rudders. The hull displacement drag is defined as follows:
<syntaxhighlight lang="xml">
<fcs_function name="hydro/displacement-drag-lbs">
<function>
<description>Drag due to displacement of hull</description>
<product>
<value>0.0000017</value> 
<property>hydro/qbar-psf</property>
<property>hydro/hull-beam-ft2</property>
<property>hydro/buoyancy-lbs</property>
<sum>
<value>1.0</value>
<product> 
<value>10.0</value>
<abs><sin><property>hydro/beta-rad</property></sin></abs>
</product>
</sum>
</product>
</function>
</fcs_function>
</syntaxhighlight>
There are a couple of things to note:
* The force is scaled by the displacement, so it will decrease as the planing forces increase and lifts the hull towards the water surface.
* The force is crudely increased as the beta angle increases (the drag increases when "side slipping" through the water, but in this case there is no data to base the increment on).
* The Cd per lbs displacement and ft^2 of hull cross section value has been tuned to the graph above, but it was also necessary to modify the static buoyancy/displacement lift function to decrease it faster with speed to get a decent match (among other things this simplified model computes the buoyancy based on the undisturbed water level and, further, at planing speeds the interface between the hull and the water is very different from at slower speeds).

The rudder drag function, on the other hand, is simpler (Cd has been tuned to the graph above while the rudder angle penalty is just guessed):
<syntaxhighlight lang="xml">
<fcs_function name="hydro/rudder-drag-lbs">
<function>
<description>Drag due to rudders (not reduced by planing)</description>
<product>
<value>0.0036</value> 
<property>hydro/qbar-psf</property>
<property>hydro/hull-beam-ft2</property>
<sum>
<value>1.0</value>
<product> 
<value>10.0</value>
<abs><property>fcs/rudder-pos-norm</property></abs>
</product>
</sum>
</product>
</function>
</fcs_function>
</syntaxhighlight>

The third component of the drag is due to planing. The planing force and moments are computed by the generic [https://sourceforge.net/p/flightgear/fgdata/ci/next/tree/Aircraft/Generic/JSBSim/Systems/hydrodynamic-planing.xml hydrodynamic-planing.xml] system. The system is based on a (simple) model of planing described in (H. Wagner, "Planing of Watercraft", 1933, translated from German as NACA-TM-1139 in 1948) which models the normal force created by a flat planing surface.

The system is set up by providing geometric information about the location of the planing surfaces (assumed to be 3) in the hydro RP frame and two tuning parameters per surface, a scaling factor for the normal force and an additional skin friction coefficient (per ft^2 of planing surface below the undisturbed water line).
<syntaxhighlight lang="xml">
<system file="hydrodynamic-planing">


<property value="27.20">hydro/planing/forebody-length-ft</property>
<property value="14.76">hydro/planing/forebody-beam-ft</property>
<property value="-7.28">hydro/planing/forebody-keel-z-ft</property>
<property value="-12.17">hydro/planing/forebody-end-x-ft</property>
... 

<property value="0.95">hydro/planing/forebody-normal-force-factor</property>
<property value="0.90">hydro/planing/middlebody-normal-force-factor</property>
<property value="0.85">hydro/planing/afterbody-normal-force-factor</property>

<property value="0.001">hydro/planing/forebody-skin-friction-coefficient</property>
<property value="0.001">hydro/planing/middlebody-skin-friction-coefficient</property>
<property value="0.001">hydro/planing/afterbody-skin-friction-coefficient</property>
</system>
</syntaxhighlight>
The system outputs lift, drag (Fbx) and side (Fby) forces as well as pitch and roll moments (yaw is missing presently) that need to be added into the corresponding channels of the craft specific hydrodynamics configuration. A visualization of the configuration is shown in the image below.

[[File:Swedish Navy T21 class MTB-planing-surfaces.jpg|thumb|600px|center|The [[Swedish Navy T21 class MTB]] with the planing surfaces for the hydrodynamic-planing system marked yellow. The marker is placed at hydro RP, the hydrodynamic reference point. Note that the system only supports flat planing surfaces but at planing speeds only the rearmost part of each surface will be in contact with water, anyway.]]

The integration of the planing drag into the craft specific hydrodynamics configuration is shown below. First the drag from the various surfaces is combined.
<syntaxhighlight lang="xml">
<fcs_function name="hydro/planing-drag-lbs">
<function>
<description>Drag due to planing.</description>
<sum>
<property>hydro/planing/forebody-induced-fbx-force-lbs</property>
<property>hydro/planing/middlebody-induced-fbx-force-lbs</property>
<property>hydro/planing/afterbody-induced-fbx-force-lbs</property>
<property>hydro/planing/forebody-friction-fbx-force-lbs</property>
<property>hydro/planing/middlebody-friction-fbx-force-lbs</property>
<property>hydro/planing/afterbody-friction-fbx-force-lbs</property>
</sum>
</function>
</fcs_function>
</syntaxhighlight>
Then it is included in the Body-X or drag channel total. Due to a potential implementation problem in hydrodynamics.xml (probably the coordinate frames issues as mentioned far above) the drag was included in the drag channel rather than in the Body-X channel. When included there it should always be positive (while in the Body-X channel it would almost always be negative), hence the added <abs>-element here.
<syntaxhighlight lang="xml">
<fcs_function name="hydro/fdrag-lbs">
<function>
<product>
<property>hydro/active-norm</property>
<sum>
<property>hydro/displacement-drag-lbs</property>
<property>hydro/rudder-drag-lbs</property>
<abs>
<property>hydro/planing-drag-lbs</property>
</abs>
</sum>
</product>
</function>
</fcs_function>
</syntaxhighlight>

''''To be continued... ''''

== Examples ==

Examples by the author of the generic systems:
* [[Malmö Flygindustri MFI-9]]
* [[Short Empire]]
* {{github url|andgi|FlightGear-Gokstad}}
* [[Swedish Navy T21 class MTB]]
* {{github url|andgi|FlightGear-Monitor}}
* {{github url|andgi|FlightGear-UB_I}}

Other aircraft
* [[Boeing 314]]
* [[Cessna 172P]]
* [[Piper J3 Cub]]

== Known problems ==

* The hydrodynamic-planing-floats system in FlightGear 2017.1.x and earlier appear to have some wires crossed - the float with the negative y-axis location appears to be on the right side of the aircraft which is not intended. Fixed before 2017.2.x.
* The hydrodynamics planing model often reacts poorly to non-smooth water surfaces (in the terrain mesh, not waves) which is not that uncommon in FlightGear's terrain. Quickly reducing speed may help.
* The hydrodynamics planing model requires a significantly increased FDM rate (the /sim/model-hz property) for good simulation results. This increases the CPU use by JSBSim (which usually is in the low single digit percent before). On some systems this change in CPU use appears to have a considerable impact on the frame rate while on other systems it has no frame rate impact (i.e. CPU isn't the bottleneck).

{{JSBSim}}
[[Category:Howto]]

Goodyear K-Type Airship/info

2020-08-20T14:14:50Z

AndersG: Renamed the image again.

<includeonly>{{infobox aircraft
| name = US Navy ZNP-K / Goodyear K-Type Airship
| devel-website = {{github url|andgi|FlightGear-ZNP-K}}
| devel-repo = {{github url|andgi|FlightGear-ZNP-K}}
| aircraft = ZNP-K
| image = ZNP-K_airship.jpg
| type = Airship/Aerostat/Military airship
| manufacturer = Goodyear Aircraft Corporation
| authors = Anders Gidenstam
| fdm = JSBSim
| fgname1 = ZNP-K
| status-fdm = 2
| status-systems = 3
| status-cockpit = 2
| status-model = 2
| download = {{github zip file|andgi|FlightGear-ZNP-K|full=1}}
| licence = GPLv2+
| navbar = 1
}}</includeonly><noinclude>
This is the aircraft infobox subpage of the [[Goodyear K-Type Airship]].
[[Category:Aircraft infobox documentation]]
</noinclude>

Goodyear K-Type Airship/info

2020-08-20T14:12:57Z

AndersG: Changed the image link back. Will rename the image.

<includeonly>{{infobox aircraft
| name = US Navy ZNP-K / Goodyear K-Type Airship
| devel-website = {{github url|andgi|FlightGear-ZNP-K}}
| devel-repo = {{github url|andgi|FlightGear-ZNP-K}}
| aircraft = ZNP-K
| image = ZNP-K.jpg
| type = Airship/Aerostat/Military airship
| manufacturer = Goodyear Aircraft Corporation
| authors = Anders Gidenstam
| fdm = JSBSim
| fgname1 = ZNP-K
| status-fdm = 2
| status-systems = 3
| status-cockpit = 2
| status-model = 2
| download = {{github zip file|andgi|FlightGear-ZNP-K|full=1}}
| licence = GPLv2+
| navbar = 1
}}</includeonly><noinclude>
This is the aircraft infobox subpage of the [[Goodyear K-Type Airship]].
[[Category:Aircraft infobox documentation]]
</noinclude>