Zeppelin NT

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Revision as of 14:47, 22 May 2009 by AndersG (Talk | contribs) (Ground crew / Mooring mast)

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Zeppelin Luftschifftechnik LZ N07
Zeppelin NT.jpg
Type Airship
Author(s) Anders Gidenstam
FDM JSBSim
--aircraft= ZLT-NT
Status Development

Handling instructions

Important controls / keys

Flight controls

  • Rudder (Aileron input is transferred to the rudder for convenience.) At low speed the rudder is automatically augmented by a tail mounted side thruster controlled by the flight control system.
  • Elevator

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.

Engine start: Mixture rich, low RPM, thrust levers set for propeller blade angle close to 0, magnetos both (} } }). Run starter as required (s).

Take off/Landing: Mixture rich, max RPM, engine swivel as needed (usually side 90 up, aft 90 down), use thrust levers for thrust control.

Cruise: Mixture rich of peak EGT, thrust levers for max thrust/blade angle, use engine RPM select for thrust control.

Zeppelin NT center console.jpg

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 fore/aft ballonet inflation rather than with the elevator trim.

  • 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.

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.

Landing short of the mast and taxing up to it allows precision control. Use the rear thruster to keep the tail wheel in the air while taxing.

The mooring mast is visible over the multiplayer network.

Zeppelin NT landing.jpg

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

Zeppelin NT cockpit.jpg

Multiplayer dual control

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

To use this feature 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. If the pilot sets /sim/remote/pilot-callsign at runtime the copilot should join MP after the pilot set /sim/remote/pilot-callsign or things won't work correctly. This will be improved in a future version.

2. 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

  • Unfortunately the pressure alarm will sound at startup since the envelope isn't initialized in a pressurized state. The ballonet inflation levers are preset to maximum inflation so the operating pressure is usually reached within 60 seconds. (Solved in FlightGear/CVS)
  • 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.
  • 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>
  • Obsolete copies of mp_broadcast.nas (e.g. from the WildFire or Air racing add-ons) could cause problems. The up to date version now resides in $FG_ROOT/Nasal/mp_broadcast.nas. Remove the others - there should be no need for them.

External links