FlightGear wiki - User contributions [en]

Edgley Optica

2014-07-01T05:00:49Z

Buckaroo:

{{infobox Aircraft
|image =Edgley_Optica_01.jpg
|alt =Edgley Optica
|name =Edgley Optica
|type = Civilian aircraft
|livery = yes
|authors = Gary Neely
|status =
|fdm = YASim
|fgname = Optica
|download = http://www.buckarooshangar.com/flightgear/Optica.zip
}}
The Optica is a light civilian observation aircraft meant to be a relatively low-cost alternative to helicopters. 25 examples of this unique and innovative aircraft were built in the late 70's through mid 80's: 2 prototypes + 23 production aircraft. This model is a hybrid of Opticas rather than a particular series because information about this rare aircraft is equally rare. To build up a reasonable picture of the Optica, I've had to use as many sources as possible. I label it as an OA7 due to the type certificate I used for some of the raw data.

== Aircraft Features ==

=== Model ===
:The model was built using a variety of references, though factory drawings were not available. I have cross-checked model details as much as possible given the limited materials and believe the model to have rather good fidelity. All flight surfaces and moveable objects animate as expected. The engine sound is based on a real Velocity IO-540. The model was not intended for "Rembrandt".

=== Cabin Modeling ===
:Fully detailed cabin featuring complete instrumentation and avionics with a fully implemented electrical system. The cabin is configured with variable lighting for night flights. There are a few other Optica simulations out there, but this one has by far the most accurate interior.

=== Livery System ===
:The model features several livery schemes at 1024x1024 resolution.

=== Engine Simulation ===
:The Optica features meaningful numbers for all engine-related instruments.

== Aircraft Controls ==
[[File:Edgley Optica cabin 01.jpg|thumb|270px|Optica cabin]]
=== Keyboard Shortcuts ===

The Optica uses standard Flightgear key mappings.

=== Clickable Levers and Sliders ===
Most levers and sliders in the cockpit are clickable. You can use LMB to increase value/position and MMB to decrease the value/position.

== Limitations ==

{| class="wikitable" width="40%"
|-
! scope="col"|
! scope="col"| Speed in kts
|-
| align="center"| Vs
| 42
|-
| align="center"| Vs0
| 38
|-
| align="center"| Vr
| 50
|-
| align="center"| V2
| 55
|-
| align="center"| VA
| 113
|-
| align="center"| Vno
| 115
|-
| align="center"| Vne
| 140 kias
|-
| align="center"| Vfe
| 1-10 deg, 110 kts<br />11-50 deg, 85 kts
|}

== Quick Startup ==
# Turn on the battery
# Set fuel to the left or right tank
# Turn on the fuel pump
# When fuel pressure comes up, use the starter switch to start the engine
# Turn on alternator switch
# Turn on avionics
# Set your altimeter to the proper pressure
# Check your heading gyros and set as necessary
# Use the trim wheel to set elevator trim to TO position
# Engage flaps to the first position marker or 10%
# Release parking break when ready

:An automagic startup function can be found in the "Optica" section of the menu bar.

== Weight and Balance ==

Since the occupants sit well forward of the wing and this is a fairly light plane, the Optica is rather sensitive to weight and balance. In the real aircraft, there is a rack for weights ahead of the instrument pylon and the tail booms conceals adjustable sliding weights. The original Optica models featured a kind of jack-stand under the rear of the engine duct that could be lowered to the ground from a control inside the cockpit, preventing the plane from tipping backwards. This does not appear in later models, so the issue must have been resolved. You can adjust weight and balance using the Equipment menu.

== Flaps ==

The inboard wing sections feature flaps fixed at 10 degrees. These cannot be adjusted in flight. Outboard flaps can be moved to as much as 50 degrees using a control on the throttle quadrant (between the seats). Optica flap movement has no detents; there are no fixed settings. Note that some Opticas could deploy flaps to no more than 40 degrees-- my guess is that these were likely the early models with the less powerful 150 or 180 HP engines.

Flaps primarily serve to allow a steeper descent for landing. They will tend to bring the nose down, especially at full flaps. Due to limitations of YASim the model does not exhibit as much of this behavior as it should. See the file 'Optica-yasim.xml' for much more information. Note that full flaps cause a lot of drag. The flaps are very robust, and 10% flaps can be left deployed for nearly the entire range of the Optica's flight envelope. 10-20% flaps are useful for low-speed loitering.

Flap position is displayed on the throttle quadrant. A flap position instrument has also been provided on the instrument console. This was not a factory standard feature, but I've added it because it's handy and I've read at least one pilot comment on the lack of a more immediately visible flap gauge. I find it very handy, especially since flaps are undetented.

== Brakes ==

The Optica did not originally have differential braking. Ground handling was adequate for most situations, though I've read at least one pilot hint that it could be better. In the model, I've retained differential braking. I do this for two reasons-- the model is much easier to handle on the ground in tight situations, and it's not unreasonable that some owners may have modded their Opticas to have differential braking. If you don't want to use differential braking, simply use the master brake key and ignore the differential braking keys.

== Fuel ==

The Optica has two 33 gallon tanks located in the leading edge of the wings forward of the flaps. There is no sump tank, at least none listed on certification sheets. Tanks are selected using a switch located on the aft section of the throttle quadrant between the seats. Switch positions are "Left", "Right", and "Off". There is no setting for "Both". Standard procedure is to feed from one tank for half an hour, then switch over to the other tank for half an hour, etc.

The original Optica configuration had a single fuel display that showed the contents of the currently selected tank. It's probable that some Opticas were modded with dual-display gauges. I've opted for a dual-display gauge, as they're cheap and it seems safer than fiddling with a switch to see how much fuel you have.

== Trim ==

The Optica features elevator trim only. Rudder and aileron trim could be adjusted only on the ground. The elevator trim control is the large wheel located on the throttle quadrant between the seats. A gauge next to the wheel indicates the current trim setting. The forward position is good for the upper end of the Optica's flight profile, the middle position indicates centered trim, and the aft position is good for takeoff and landing.

== Flying ==
[[File:Edgley Optica 02.jpg|thumb|270px]]
The Optica is very easy and forgiving to fly. It is slow, having a maximum speed of around 140 knots, but it was meant for local civilian observation roles. It's hard to find a fixed-wing aircraft with better visibility.

For takeoff, set 10 degree flaps, set trim to the aft-most indicated position, and at 50 knots apply back pressure on the stick and rotate at 55. For landing, set 30-50 degree flaps, trim near the aft-most position, approach at 50-55 knots, land at 45-50. In level flight, stall with no flaps is 43 knots, with full flaps 38 knots. Stalls are gentle and very mushy, and somewhat difficult to get into, as the elevator throw is generally insufficient to get you into very high AoA regions. The aircraft can almost float to the ground with no power and the stick held back. This is the reported behavior of the real aircraft. Note that most online sources list the Optica's stall speed at 58 knots. This is an error that has been propagated from source to source. A lesson in never trusting uncited Internet sources.

The Optica's optimal cruise is 70-80 knots with 40% throttle and mixture leaned to optimal. Best climb can be found maintaining 60-70 knots. The aircraft can reasonably maintain level flight down to around 45 knots with flaps at 20 degrees. The Optica is a high-lift configuration and will cruise with a significant nose-down attitude. The forward indicated trim position is best for the Optica's upper speed range. It likes a fair amount of back-pressure on the stick until you reach cruise speeds, so be sure and set trim for takeoff and landing.

Maintaining level flight without consulting the instruments takes a little practice. Sitting in a giant fish bowl leaves few visual cues. Some Optica pilots placed a small line of tape at the approximate horizon line. In the model I've found I can generally maintain level flight by noting the position of the magnetic compass with respect to the horizon. It becomes easy with a little practice.

== The Instrument Pylon and Console ==

The console was designed to minimize intrusion on the view. The prototype Opticas had an even smaller console, probably with enough room only for the sacred six flight instruments. Radios were set into the strip between the seats and the pylon in those models. This must have been less than optimal as production models used the version I have modeled, with enough room for nine instruments and radios to the right.

The lower pylon console instrument and controls placement is speculative. I have only a few pictures of this region and the layout seems to vary quite a bit, so while this layout is loosely based on a few real aircraft, it's largely my own. Note that I have likely modeled the lower pylon slightly too wide. I lacked exact measurements and was forced to interpolate from photos. More recent photo acquisitions suggest it was not wide enough for two standard 3.25" instruments, so the Manifold Pressure and RPM gauges might not fit as I have built it. As I'm not certain about this and it's convenient to have room for two side by side, I've left it as-is.

I'm not certain where the instrument panel lighting control would normally go. With so few Optica's built, and the survivors having been through many owners, it likely varied. Console space is at a premium, so I placed it on the upper panel with other light switches. Note that this too is speculative. The upper panel (when it's present) seems to vary quite a bit.

== The Throttle Quadrant ==

The large right-side lever is a hand brake. I do not know if the Optica had a separate emergency parking brake system. In the model the hand brake is used to signal that the parking brake is set (brakes are in a locked position). If the handle is not level with the throttle quadrant, your parking break is set.

The trim wheel indicator does not display the full range of possible trim motion, but you won't need that much trim. The Optica is fairly sensitive to trim positions.

I have vague indications suggesting that early Opticas may have had the ignition switch positioned at the aft end of the throttle quadrant, further behind the fuel selector. Since I have no pictures showing any ignition switch position, I've positioned in a logical position on the instrument pylon.

The small lever to the right of the mixture lever is a friction control for adjusting the ease of moving mixture and throttle levers. Since this is not an issue for the simulation, I use this control to adjust how much the mixture hot key adjusts mixture. With the lever back (default), mixture moves in 5% increments. With the lever advanced, mixture moves in finer 1% increments.

Note that this is a fixed-pitch aircraft-- there is no propeller/RPM lever. Propeller pitch could be adjusted on the ground.

== Avionics ==

Comm, Nav and ADF function as you would expect. Nav 1 (the top radio) is linked the the RMI in the bottom left corner. Nav 2 (the 2nd radio down) is linked to the CDI, bottom center. The ADF receiver (3rd panel down) operates on the RMI and the ADF. The ADF is superfluous, but is present for practice with such older instruments.

The audio board currently doesn't do much except provide marker beacon lights and the ability to disable the marker beacon receiver.

The transponder has no functionality, but it's there if you want to emulate procedures. It does have all the animations and control mappings necessary for operation, and could easily be adapted to work with any Flightgear transponder implementation.

For more on the avionics, see the file "README_avionics.txt".

== Other Stuff ==

Some details are left unfinished. For example, if you look close you'll see there is no mechanism for moving the flaps-- they magically move into place. This is because I have no clear image or details of flap mechanics other than what is currently shown. I hope to add this sort of thing later.

For more notes about the model, see the YASim configuration file and the nasal script files.

Information from the model came from very many sources, and often had to be pieced together from a combination of sources. I have a significant collection of photographs and a few articles, including the full report of the fatal crash of an Optica. Contact me if interested. I've not been able to locate a true flight manual and would be very grateful if anyone can point me to one.

== External Links ==

For more information, updates, paint kits, etc., visit:

* [http://www.buckarooshangar.com/flightgear/ Buckaroo's Flightgear Projects]

[[Category:Civilian aircraft]]
[[Category:Civil utility aircraft]]
[[Category:Propeller aircraft]]
[[Category:Single-engine aircraft]]
[[Category:Special-purpose aircraft]]
[[Category:Ducted fan-powered aircraft]]

File:Edgley Optica cabin 01.jpg

2014-07-01T04:46:28Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Edgley Optica cabin}}
|date=2011-09-22 21:04:05
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of cabins]]

File:Edgley Optica 02.jpg

2014-07-01T04:45:13Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Edgley Optica}}
|date=2011-09-22 22:30:15
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of civil utility aircraft]]

Velocity XL RG

2014-07-01T01:24:40Z

Buckaroo:

{{infobox Aircraft
|image =Velocity-XL-RG.jpg
|alt =Velocity XL RG
|name =Velocity XL RG
|type = Civilian aircraft
|livery = yes
|authors = Gary Neely
|status =
|fdm = YASim
|fgname = Velocity-XL-RG
|download = http://www.buckarooshangar.com/flightgear/Velocity_XL_RG.zip
}}
The Velocity XL is an American amateur-built aircraft produced by Velocity, Inc. Introduced in 1997, the Velocity XL (Extra Large) is an enlarged version of the Velocity SE, featuring a roomier cabin and accommodations for a larger engine. The Velocity XL is available to builders in kit form and features several kit variations, including options for retractable gear (the RG designator) and a belly-mounted airbrake. Using an IO 540 engine, the aircraft is capable of cruising up to 200 kt, and can achieve a range of over 1300 nm at 65% power.

== Aircraft Features ==
[[File:Velocity-XL-RG exterior 01.jpg|thumb|270px]]
=== Model ===
:The model was built using the factory builder's guide and several builder's blogs as references. All flight surfaces and moveable objects animate as expected, including the gull-wing doors. Engine/prop sound is based on a real Velocity IO-540. The model was made with optimization in mind and should perform well on relatively modest computers. It was not intended for "Rembrandt".

:A simplified "AI" version is available for those wishing to see the model in multi-player, but not fly it. Visit the model's home page found in the [[#External Links|External Links]] section below to get the "AI" version.

=== Cabin Modeling ===
:Fully detailed cabin featuring complete instrumentation and avionics with a fully implemented electrical system. The cabin is configured with variable lighting for night flights based on a real Velocity lighting installation.

=== Livery System ===
:The model features several livery schemes with both a 1024x1024 and a 2048x2048 version. The default livery is a light-weight 1024x1024 scheme that should play nicely in a multi-player environment.

=== Engine Simulation ===
:A unique engine simulation allows the pilot to monitor temperatures and fuel flow and meaningfully set mixture and propeller settings for economy or power.

== Aircraft Controls ==
[[File:Velocity-XL-RG cabin 01.jpg|thumb|270px]]

=== Keyboard Shortcuts ===
{| class="wikitable" width="50%"
|-
! scope="col"| Key
! scope="col"| Binding
|-
| align="center"| {{key press|Ctrl|b}}
| Toggles both rudders to maximum deflection as airbrake
|}

:All other functions use Flightgear standard key mappings.

=== Clickable Levers and Sliders ===
Most levers and sliders in the cockpit are clickable. You can use LMB to increase value/position and MMB to decrease the value/position, or you can use the scroll wheel to make finer adjustments.

== Limitations ==
[[File:Velocity-XL-RG cabin 02.png|thumb|270px|Screenshot of Velocity XL RG main panel at night]]

{| class="wikitable" width="40%"
|-
! scope="col"|
! scope="col"| Speed in kts
|-
| align="center"| Vs
| 65
|-
| align="center"| Vr
| 75
|-
| align="center"| Vle
| 110
|-
| align="center"| Vlo
| 120
|-
| align="center"| Vno
| 140
|-
| align="center"| Vne
| 200 kias
|}

== Quick Startup ==
# Set fuel to 'Both'
# Turn on the master battery
# Turn on the fuel boost pump
# Turn on the left and right magneto switches
# After fuel pressure comes up, use the starter switch to start the engine
# Turn off fuel boost pump (optional)
# Turn on alternator switch
# Turn on avionics switch
# Set your altimeter to the proper pressure
# Check your heading gyros and set as necessary
# Set elevator trim as desired (the Velocity menu features a suggested setting)
# Release parking break when ready

:An automagic startup function can be found in the "Velocity" section of the menu bar.

== Steering and Brakes ==

The Velocity nose wheel casters and is not steerable. Steering is accomplished by differential braking. This makes the Velocity handle very tightly on the ground, but requires attention on takeoff until the rudders are effective.

The standard Velocity kit couples braking with rudder deflection, but like many builders, this model uses a toe-brake option to de-couple rudder and braking.

== Weight and Balance ==

The plane's default load is rather light, having a single pilot, some nose ballast and a modest fuel load. This makes the default experience exceptionally nimble and responsive. Use the Equipment menu to experience the more typical real-world load options.

The real Velocity is fairly sensitive to weight and balance. It's critically important not to have the CG too far back, which can result in flat stalls or other not so good behaviors. Changes to the Velocity's wings have largely eliminated the flat stalls, but careful attention to weight and balance is still essential for safe flying. The model's CG and weight have been configured using real-world Velocity weight and balance worksheets. See the file "velocity-xl-rg-yasim.xml" for more notes and information.

== Fuel ==

A Velocity XL with retractable gear has two 33 gallon tanks located in the leading half of the inboard wing segments known as the "strakes". Each tank is essentially a hollowed-out portion of the strake, provided with baffles and coated with fuel-proof epoxy. A corresponding sight gauge to either side of the rear seats indicates the load of each tank. A 4 gallon sump tank sits low against the firewall behind the rear seats, though only 2.5 gallons are usable. Note that the main panel fuel instrument shows the capacity of the two main tanks-- there is no readout for the sump. If your two main tanks are showing empty, you'd better have an airfield in sight.

The base Velocity build has a very simple fuel feed. Both tanks feed the sump which feeds the engine with no valves or selectors. Like some Velocity builders do, this model adds a fuel control switch to allow left-right-both-off settings.

You need the boost pump only for cold engine starting. After fuel pressure has come up and the engine is started, you should turn it off, otherwise it will cost you additional fuel. You might wish to leave it on during the early stages of your climb and turn it on for approach. The boost pump can be used to further richen the mixture if cylinder temps get too hot, but at the expense of extra fuel. Mixture is auto-enriched at high power settings, so you don't really need this on for take-off.

== Airbrakes ==

The Velocity's twin vertical stabs have independent one-way rudders; travel is outboard for each. Because of this both rudders can be deployed simultaneously, deflecting each rudder outboard as a form of speed braking. The effect is relatively weak but helpful. Expect a slight pitch-up effect when using the rudders in this way.

Since rudders can be deployed independently, the rudder pedals are not coupled in the standard Velocity build. This may not work with many rudder pedal sets, where the pedals pivot about a center point. In this case, you can use the ctrl-b function to toggle both rudders to maximum deflection. Note that rudder control is effectively disabled while set this way. An indicator light on the main panel displays this condition. This light isn't a real Velocity indicator, only a sim aid.

Some Velocity builds incorporate a bellyflap speedbrake for more effective airbraking. The model does not have this feature and won't until details become available on how the aircraft reacts to its deployment.

== Flying ==
[[File:Velocity-XL-RG exterior 02.jpg|thumb|270px]]
Normal flight is responsive and free of any quirks. The author is not a pilot, has never been in a Velocity, and makes no claim that the model flies true to the real thing. That said, the model conforms fairly closely to the pilot's handbook. If you stay within normal flight profiles it should not do anything peculiar.

'''Takeoff''' - Lift the nose at 60-70 kts, then rotate at 75, 80-85 if operating at heavy gross weights. Trimming for takeoff helps. Try not to touch the brakes too much to steer on the takeoff roll. The rudders will become effective above 25 kts. Don't rotate too far especially with a light load (aft CG), as you could place the CG aft of the main gear and tip the Velocity on its tail. (In the real Velocity you risk prop damage.) Never rotate the canard above the horizon.

The Velocity is a pusher-configuration, so expect propeller effects to be reversed from what you might be accustomed to.

'''Climb''' - Optimum climb is 100 knots. Best climb is 80, and for optimum visibility and cooling, 110. Climb with WOT (wide open throttle), reducing RPM as desired and leaning as desired.

'''Cruise''' - Consider running your Velocity at WOT and adjusting power using mixture and propeller controls. Remember to turn the fuel pump off. You should get your best economy this way. See the engine section for tips on power settings.

The model features the Lycoming IO-540-K 300 HP engine. With the default light load, this gives you a lot of power to play with, and is necessary to achieve the top end speeds. Note that while the design is capable of very high speeds in mild air, many Velocities don't achieve those speeds. Top speed depends on flight conditions, engine, the quality of the build, the propeller and pitch settings, and other factors.

'''Descent''' - Plan your descent well in advance of your destination. The Velocity is very slick and will take a while to shed speed. Although the simulation won't care, it's recommended that you reduce power gradually in increments of 1" every minute or so in order to minimize possible negative effects on your engine.

'''Approach''' - Enter the pattern at 85-90 kts, approach at 80. Flare slightly and land at 70-75. Add 5 knots for heavy loads. This is a very clean airplane-- don't approach too fast or you could easily double your runway needs. Again, plan your approach well in advance or you may need to go-around due to excessive speed. (This advice is straight out of the pilot's handbook for those who may be thinking this is an FDM flaw-- it's not. The Velocity is very slippery.) Use the rudder-brake to help control your descent, but remember to unlock it before crossing the threshold. Fly the aircraft down to the runway-- don't try to stall the aircraft to a landing or use excessive flare.

'''Stalls''' - Stall is listed at 65 kts, but varies considerably with the build and the load. The handbook reports the aircraft is manageable and responsive down to 60 kts with lighter loads.

Due to the canard configuration, a "stall" in the Velocity is more like a nose bobbing motion, where you can no longer keep the nose up. With the stick fully back in low-speed flight, you will reach a point where the elevator begins to stall before the wing, dropping the nose and picking up lift again such that the nose begins to come up. You may notice a slight oscillation in pitch when this begins to happen, called "pitch bucking". This video demonstrates the effect: http://www.youtube.com/watch?v=zeTjPPpVtuU Watch carefully for the pitching oscillations. For another demonstration: http://www.youtube.com/watch?v=M-dGCUsZvDY, at about 5:11 into the video.

Because the aircraft has small tires and an aft-mounted propeller, the Velocity is not recommended for rough or grass fields. The Velocity is also not recommended for short fields due to its relatively long runway needs.

== Avionics ==

Comm, Nav and ADF function as you would expect. Nav 1 (the top radio) is linked the the RMI in the bottom left corner. Nav 2 (the 2nd radio down) is linked to the CDI, bottom center. The ADF receiver (3rd panel down) operates on the RMI and the ADF. The ADF is superfluous, but is present for practice with such older instruments.

The audio board currently doesn't do much except provide marker beacon lights and the ability to disable the marker beacon receiver.

The transponder has no functionality, but it's there if you want to emulate procedures. It does have all the animations and control mappings necessary for operation, and could easily be adapted to work with any Flightgear transponder implementation.

For more on the avionics, see the file "README_avionics.txt".

== Engine Modeling ==

This Velocity model features a new and experimental engine simulation created by the author. The system replaces most YASim values with custom calculations. The system is based on maintaining reasonably correct air-fuel ratios combined with tabular data for engine temperatures and other information. The result allows you to find best power or best economy settings while keeping your cylinder temps reasonable.

The EDM (Engine Data Management) instrument is very loosely like a JP Instruments EDM. Its main function is to report engine cylinder EGT and CHT values. (The device does not yet model other EDM capabilities.) The EGT and CHT numbers report a kind of average value, though the individual bars do report true to their cylinders. I've taken some liberties with the size and positioning of the readouts for legibility.

Note that oil temperature reads in degrees Centigrade, while other temps are degrees Fahrenheit.

Play with the the power and mixture controls while watching EGT, the HP estimate, and fuel flow to find your best power or economy settings at your altitude. Best economy is approximately 50 degrees lean of peak EGT, while best power is about 80 degrees rich of peak EGT. The CHT values will tell you when you're getting into troubling regions. The default cylinder temperature ranges are set very conservatively so you shouldn't have any problems; just keep CHT's out of the red. Remember that EGT responds nearly instantaneously, while cylinder temps take a while to build up or cool down. The engine has an auto-rich feature, so as you push the throttle in beyond 65% you will also begin richening the mixture.

A real pilot will likely find the numbers a bit off-- the model's numbers are based on some real data, some data for similar engines, and some guesses. The author has no experience with these engines and what their temps do at various power settings. If you have experience with the Lycoming IO-540-K or similar and have better numbers, feel free to adjust the temperature tables found in "Systems/Velocity-XL-RG-engine.XML"; if you send me your recommended changes, I'll use them. See that file and the related nasal script for more information.

For notes on the development of this engine simulation, see:

*[http://www.buckarooshangar.com/flightgear/yasim_pistonengines.html Simulation of Piston Engine Fuel Consumption and Engine Temperature using YASim]

== Ground Shadow ==

The model features a simple object-based shadow to provide a reference when taking off and landing in chase view. It's enabled at elevations of less than 100m, when gear is down, and the sun is reasonably up. It works tolerably well for its purpose, especially when the sun is well up since it doesn't move with the sun (not worth the effort right now). If you don't like or need this fake shadow, simply disable it using the Velocity menu option. Your preference will be saved if you use the Flightgear exit option.

== Other Stuff ==

The three NACA scoops on the upper aft cabin are two engine cooling intake ducts, and a smaller cabin air intake. The engine cooling outlets are located to either side of the propeller. On the left side of the nose is another NACA scoop, this one is the intake for the secondary engine oil cooler (which also provides cabin heat). Below this and aft of the nose gear doors is the exhaust for the oil cooler. Some Velocity builds have an intake on the right side of the nose for a cabin air intake, and some have additional intakes in the engine cowl, probably for oil coolers and/or revised air intakes.

Those familiar with the aircraft may notice the lack of cowl retaining screws. I learned some builders create a retaining flange on the forward cowl that slips under the fuselage skin just aft of the firewall. That holds down the forward section. On the aft cowl, standard hardware hinges are fixed inside the cowl, half the hinge on the upper cowl, the other half on the lower cowl. They mate together perfectly, and the removable hinge pins holds the two hinge halves and therefore the cowl halves together. It's simple, hidden from view, has no screws to come loose and hit the prop, and looks clean. I thought it amazingly clever, and decided to assume my model uses that technique. And it saves me from exactly placing those damned screws.

A few external details are missing: the "sparrow strainer" which assists trimming the elevator at higher speeds and elevator counterweights, which the author simply forgot to model (sorry). The latter are hard to see anyway, so it's not a big deal. Inside, the rudder cables that run to the pedals are missing, but unless you know what to look for, you'd never notice this.

For more notes about the model, see the YASim configuration file and the nasal script files.

== External Links ==

For more information, updates, paint kits, etc., visit:

* [http://www.buckarooshangar.com/flightgear/ Buckaroo's Flightgear Projects]

[[Category:Civilian aircraft]]
[[Category:Civil utility aircraft]]
[[Category:Propeller aircraft]]
[[Category:Single-engine aircraft]]

Velocity XL RG

2014-07-01T01:20:35Z

Buckaroo:

{{infobox Aircraft
|image =Velocity-XL-RG.jpg
|alt =Velocity XL RG
|name =Velocity XL RG
|type = Civilian aircraft
|livery = yes
|authors = Gary Neely
|status =
|fdm = YASim
|fgname = Velocity-XL-RG
|download = http://www.buckarooshangar.com/flightgear/Velocity_XL_RG.zip
}}
The Velocity XL is an American amateur-built aircraft produced by Velocity, Inc. Introduced in 1997, the Velocity XL (Extra Large) is an enlarged version of the Velocity SE, featuring a roomier cabin and accommodations for a larger engine. The Velocity XL is available to builders in kit form and features several kit variations, including options for retractable gear (the RG designator) and a belly-mounted airbrake. Using an IO 540 engine, the aircraft is capable of cruising up to 200 kt, and can achieve a range of over 1300 nm at 65% power.

== Aircraft Features ==
[[File:Velocity-XL-RG exterior 01.jpg|thumb|270px]]
=== Model ===
:The model was built using the factory builder's guide and several builder's blogs as references. All flight surfaces and moveable objects animate as expected, including the gull-wing doors. Engine/prop sound is based on a real Velocity IO-540. The model was made with optimization in mind and should perform well on relatively modest computers. It was not intended for "Rembrandt".

:A simplified "AI" version is available for those wishing to see the model in multi-player, but not fly it. Visit the model's home page found in the [[#External Links|External Links]] section below to get the "AI" version.

=== Cabin Modeling ===
:Fully detailed cabin featuring complete instrumentation and avionics with a fully implemented electrical system. The cabin is configured with variable lighting for night flights based on a real Velocity lighting installation.

=== Livery System ===
:The model features several livery schemes with both a 1024x1024 and a 2048x2048 version. The default livery is a light-weight 1024x1024 scheme that should play nicely in a multi-player environment.

=== Engine Simulation ===
:A unique engine simulation allows the pilot to monitor temperatures and fuel flow and set mixture settings for economy or power.

== Aircraft Controls ==
[[File:Velocity-XL-RG cabin 01.jpg|thumb|270px]]

=== Keyboard Shortcuts ===
{| class="wikitable" width="50%"
|-
! scope="col"| Key
! scope="col"| Binding
|-
| align="center"| {{key press|Ctrl|b}}
| Toggles both rudders to maximum deflection as airbrake
|}

:All other functions use Flightgear standard key mappings.

=== Clickable Levers and Sliders ===
Most levers and sliders in the cockpit are clickable. You can use LMB to increase value/position and MMB to decrease the value/position, or you can use the scroll wheel to make finer adjustments.

== Limitations ==
[[File:Velocity-XL-RG cabin 02.png|thumb|270px|Screenshot of Velocity XL RG main panel at night]]

{| class="wikitable" width="40%"
|-
! scope="col"|
! scope="col"| Speed in kts
|-
| align="center"| Vs
| 65
|-
| align="center"| Vr
| 75
|-
| align="center"| Vle
| 110
|-
| align="center"| Vlo
| 120
|-
| align="center"| Vno
| 140
|-
| align="center"| Vne
| 200 kias
|}

== Quick Startup ==
# Set fuel to 'Both'
# Turn on the master battery
# Turn on the fuel boost pump
# Turn on the left and right magneto switches
# After fuel pressure comes up, use the starter switch to start the engine
# Turn off fuel boost pump (optional)
# Turn on alternator switch
# Turn on avionics switch
# Set your altimeter to the proper pressure
# Check your heading gyros and set as necessary
# Set elevator trim as desired (the Velocity menu features a suggested setting)
# Release parking break when ready

:An automagic startup function can be found in the "Velocity" section of the menu bar.

== Steering and Brakes ==

The Velocity nose wheel casters and is not steerable. Steering is accomplished by differential braking. This makes the Velocity handle very tightly on the ground, but requires attention on takeoff until the rudders are effective.

The standard Velocity kit couples braking with rudder deflection, but like many builders, this model uses a toe-brake option to de-couple rudder and braking.

== Weight and Balance ==

The plane's default load is rather light, having a single pilot, some nose ballast and a modest fuel load. This makes the default experience exceptionally nimble and responsive. Use the Equipment menu to experience the more typical real-world load options.

The real Velocity is fairly sensitive to weight and balance. It's critically important not to have the CG too far back, which can result in flat stalls or other not so good behaviors. Changes to the Velocity's wings have largely eliminated the flat stalls, but careful attention to weight and balance is still essential for safe flying. The model's CG and weight have been configured using real-world Velocity weight and balance worksheets. See the file "velocity-xl-rg-yasim.xml" for more notes and information.

== Fuel ==

A Velocity XL with retractable gear has two 33 gallon tanks located in the leading half of the inboard wing segments known as the "strakes". Each tank is essentially a hollowed-out portion of the strake, provided with baffles and coated with fuel-proof epoxy. A corresponding sight gauge to either side of the rear seats indicates the load of each tank. A 4 gallon sump tank sits low against the firewall behind the rear seats, though only 2.5 gallons are usable. Note that the main panel fuel instrument shows the capacity of the two main tanks-- there is no readout for the sump. If your two main tanks are showing empty, you'd better have an airfield in sight.

The base Velocity build has a very simple fuel feed. Both tanks feed the sump which feeds the engine with no valves or selectors. Like some Velocity builders do, this model adds a fuel control switch to allow left-right-both-off settings.

You need the boost pump only for cold engine starting. After fuel pressure has come up and the engine is started, you should turn it off, otherwise it will cost you additional fuel. You might wish to leave it on during the early stages of your climb and turn it on for approach. The boost pump can be used to further richen the mixture if cylinder temps get too hot, but at the expense of extra fuel. Mixture is auto-enriched at high power settings, so you don't really need this on for take-off.

== Airbrakes ==

The Velocity's twin vertical stabs have independent one-way rudders; travel is outboard for each. Because of this both rudders can be deployed simultaneously, deflecting each rudder outboard as a form of speed braking. The effect is relatively weak but helpful. Expect a slight pitch-up effect when using the rudders in this way.

Since rudders can be deployed independently, the rudder pedals are not coupled in the standard Velocity build. This may not work with many rudder pedal sets, where the pedals pivot about a center point. In this case, you can use the ctrl-b function to toggle both rudders to maximum deflection. Note that rudder control is effectively disabled while set this way. An indicator light on the main panel displays this condition. This light isn't a real Velocity indicator, only a sim aid.

Some Velocity builds incorporate a bellyflap speedbrake for more effective airbraking. The model does not have this feature and won't until details become available on how the aircraft reacts to its deployment.

== Flying ==
[[File:Velocity-XL-RG exterior 02.jpg|thumb|270px]]
Normal flight is responsive and free of any quirks. The author is not a pilot, has never been in a Velocity, and makes no claim that the model flies true to the real thing. That said, the model conforms fairly closely to the pilot's handbook. If you stay within normal flight profiles it should not do anything peculiar.

'''Takeoff''' - Lift the nose at 60-70 kts, then rotate at 75, 80-85 if operating at heavy gross weights. Trimming for takeoff helps. Try not to touch the brakes too much to steer on the takeoff roll. The rudders will become effective above 25 kts. Don't rotate too far especially with a light load (aft CG), as you could place the CG aft of the main gear and tip the Velocity on its tail. (In the real Velocity you risk prop damage.) Never rotate the canard above the horizon.

The Velocity is a pusher-configuration, so expect propeller effects to be reversed from what you might be accustomed to.

'''Climb''' - Optimum climb is 100 knots. Best climb is 80, and for optimum visibility and cooling, 110. Climb with WOT (wide open throttle), reducing RPM as desired and leaning as desired.

'''Cruise''' - Consider running your Velocity at WOT and adjusting power using mixture and propeller controls. Remember to turn the fuel pump off. You should get your best economy this way. See the engine section for tips on power settings.

The model features the Lycoming IO-540-K 300 HP engine. With the default light load, this gives you a lot of power to play with, and is necessary to achieve the top end speeds. Note that while the design is capable of very high speeds in mild air, many Velocities don't achieve those speeds. Top speed depends on flight conditions, engine, the quality of the build, the propeller and pitch settings, and other factors.

'''Descent''' - Plan your descent well in advance of your destination. The Velocity is very slick and will take a while to shed speed. Although the simulation won't care, it's recommended that you reduce power gradually in increments of 1" every minute or so in order to minimize possible negative effects on your engine.

'''Approach''' - Enter the pattern at 85-90 kts, approach at 80. Flare slightly and land at 70-75. Add 5 knots for heavy loads. This is a very clean airplane-- don't approach too fast or you could easily double your runway needs. Again, plan your approach well in advance or you may need to go-around due to excessive speed. (This advice is straight out of the pilot's handbook for those who may be thinking this is an FDM flaw-- it's not. The Velocity is very slippery.) Use the rudder-brake to help control your descent, but remember to unlock it before crossing the threshold. Fly the aircraft down to the runway-- don't try to stall the aircraft to a landing or use excessive flare.

'''Stalls''' - Stall is listed at 65 kts, but varies considerably with the build and the load. The handbook reports the aircraft is manageable and responsive down to 60 kts with lighter loads.

Due to the canard configuration, a "stall" in the Velocity is more like a nose bobbing motion, where you can no longer keep the nose up. With the stick fully back in low-speed flight, you will reach a point where the elevator begins to stall before the wing, dropping the nose and picking up lift again such that the nose begins to come up. You may notice a slight oscillation in pitch when this begins to happen, called "pitch bucking". This video demonstrates the effect: http://www.youtube.com/watch?v=zeTjPPpVtuU Watch carefully for the pitching oscillations. For another demonstration: http://www.youtube.com/watch?v=M-dGCUsZvDY, at about 5:11 into the video.

Because the aircraft has small tires and an aft-mounted propeller, the Velocity is not recommended for rough or grass fields. The Velocity is also not recommended for short fields due to its relatively long runway needs.

== Avionics ==

Comm, Nav and ADF function as you would expect. Nav 1 (the top radio) is linked the the RMI in the bottom left corner. Nav 2 (the 2nd radio down) is linked to the CDI, bottom center. The ADF receiver (3rd panel down) operates on the RMI and the ADF. The ADF is superfluous, but is present for practice with such older instruments.

The audio board currently doesn't do much except provide marker beacon lights and the ability to disable the marker beacon receiver.

The transponder has no functionality, but it's there if you want to emulate procedures. It does have all the animations and control mappings necessary for operation, and could easily be adapted to work with any Flightgear transponder implementation.

For more on the avionics, see the file "README_avionics.txt".

== Engine Modeling ==

This Velocity model features a new and experimental engine simulation created by the author. The system replaces most YASim values with custom calculations. The system is based on maintaining reasonably correct air-fuel ratios combined with tabular data for engine temperatures and other information. The result allows you to find best power or best economy settings while keeping your cylinder temps reasonable.

The EDM (Engine Data Management) instrument is very loosely like a JP Instruments EDM. Its main function is to report engine cylinder EGT and CHT values. (The device does not yet model other EDM capabilities.) The EGT and CHT numbers report a kind of average value, though the individual bars do report true to their cylinders. I've taken some liberties with the size and positioning of the readouts for legibility.

Note that oil temperature reads in degrees Centigrade, while other temps are degrees Fahrenheit.

Play with the the power and mixture controls while watching EGT, the HP estimate, and fuel flow to find your best power or economy settings at your altitude. Best economy is approximately 50 degrees lean of peak EGT, while best power is about 80 degrees rich of peak EGT. The CHT values will tell you when you're getting into troubling regions. The default cylinder temperature ranges are set very conservatively so you shouldn't have any problems; just keep CHT's out of the red. Remember that EGT responds nearly instantaneously, while cylinder temps take a while to build up or cool down. The engine has an auto-rich feature, so as you push the throttle in beyond 65% you will also begin richening the mixture.

A real pilot will likely find the numbers a bit off-- the model's numbers are based on some real data, some data for similar engines, and some guesses. The author has no experience with these engines and what their temps do at various power settings. If you have experience with the Lycoming IO-540-K or similar and have better numbers, feel free to adjust the temperature tables found in "Systems/Velocity-XL-RG-engine.XML"; if you send me your recommended changes, I'll use them. See that file and the related nasal script for more information.

For notes on the development of this engine simulation, see:

*[http://www.buckarooshangar.com/flightgear/yasim_pistonengines.html Simulation of Piston Engine Fuel Consumption and Engine Temperature using YASim]

== Ground Shadow ==

The model features a simple object-based shadow to provide a reference when taking off and landing in chase view. It's enabled at elevations of less than 100m, when gear is down, and the sun is reasonably up. It works tolerably well for its purpose, especially when the sun is well up since it doesn't move with the sun (not worth the effort right now). If you don't like or need this fake shadow, simply disable it using the Velocity menu option. Your preference will be saved if you use the Flightgear exit option.

== Other Stuff ==

The three NACA scoops on the upper aft cabin are two engine cooling intake ducts, and a smaller cabin air intake. The engine cooling outlets are located to either side of the propeller. On the left side of the nose is another NACA scoop, this one is the intake for the secondary engine oil cooler (which also provides cabin heat). Below this and aft of the nose gear doors is the exhaust for the oil cooler. Some Velocity builds have an intake on the right side of the nose for a cabin air intake, and some have additional intakes in the engine cowl, probably for oil coolers and/or revised air intakes.

Those familiar with the aircraft may notice the lack of cowl retaining screws. I learned some builders create a retaining flange on the forward cowl that slips under the fuselage skin just aft of the firewall. That holds down the forward section. On the aft cowl, standard hardware hinges are fixed inside the cowl, half the hinge on the upper cowl, the other half on the lower cowl. They mate together perfectly, and the removable hinge pins holds the two hinge halves and therefore the cowl halves together. It's simple, hidden from view, has no screws to come loose and hit the prop, and looks clean. I thought it amazingly clever, and decided to assume my model uses that technique. And it saves me from exactly placing those damned screws.

A few external details are missing: the "sparrow strainer" which assists trimming the elevator at higher speeds and elevator counterweights, which the author simply forgot to model (sorry). The latter are hard to see anyway, so it's not a big deal. Inside, the rudder cables that run to the pedals are missing, but unless you know what to look for, you'd never notice this.

For more notes about the model, see the YASim configuration file and the nasal script files.

== External Links ==

For more information, updates, paint kits, etc., visit:

* [http://www.buckarooshangar.com/flightgear/ Buckaroo's Flightgear Projects]

[[Category:Civilian aircraft]]
[[Category:Civil utility aircraft]]
[[Category:Propeller aircraft]]
[[Category:Single-engine aircraft]]

Velocity XL RG

2014-06-30T22:53:38Z

Buckaroo:

{{infobox Aircraft
|image =Velocity-XL-RG.jpg
|alt =Velocity XL RG
|name =Velocity XL RG
|type = Civilian aircraft
|livery = yes
|authors = Gary Neely
|status =
|fdm = YASim
|fgname = Velocity-XL-RG
|download = http://www.buckarooshangar.com/flightgear/Velocity_XL_RG.zip
}}
The Velocity XL is an American amateur-built aircraft produced by Velocity, Inc. Introduced in 1997, the Velocity XL (Extra Large) is an enlarged version of the Velocity SE, featuring a roomier cabin and accommodations for a larger engine. The Velocity XL is available to builders in kit form and features several kit variations, including options for retractable gear (the RG designator) and a belly-mounted airbrake. Using an IO 540 engine, the aircraft is capable of cruising up to 200 kt, and can achieve a range of over 1300 nm at 65% power.

== Aircraft Features ==
[[File:Velocity-XL-RG exterior 01.jpg|thumb|270px]]
=== Model ===
:The model was built using the factory builder's guide and several builder's blogs as references. All flight surfaces and moveable objects animate as expected, including the gull-wing doors. Engine/prop sound is based on a real Velocity IO-540.

=== Cabin Modeling ===
:Fully detailed cabin featuring complete instrumentation and avionics with a fully implemented electrical system. The cabin is configured with variable lighting for night flights based on a real Velocity lighting installation.

=== Livery System ===
:The model features several livery schemes with both a 1024x1024 and a 2048x2048 version. The default livery is a light-weight 1024x1024 scheme that should play nicely in a multi-player environment.

=== Engine Simulation ===
:A unique engine simulation allows the pilot to monitor temperatures and fuel flow and set mixture settings for economy or power.

== Aircraft Controls ==
[[File:Velocity-XL-RG cabin 01.jpg|thumb|270px]]

=== Keyboard Shortcuts ===
{| class="wikitable" width="50%"
|-
! scope="col"| Key
! scope="col"| Binding
|-
| align="center"| {{key press|Ctrl|b}}
| Toggles both rudders to maximum deflection as airbrake
|}

:All other functions use Flightgear standard key mappings.

=== Clickable Levers and Sliders ===
Most levers and sliders in the cockpit are clickable. You can use LMB to increase value/position and MMB to decrease the value/position, or you can use the scroll wheel to make finer adjustments.

== Limitations ==
[[File:Velocity-XL-RG cabin 02.png|thumb|270px|Screenshot of Velocity XL RG main panel at night]]

{| class="wikitable" width="40%"
|-
! scope="col"|
! scope="col"| Speed in kts
|-
| align="center"| Vs
| 65
|-
| align="center"| Vr
| 75
|-
| align="center"| Vle
| 110
|-
| align="center"| Vlo
| 120
|-
| align="center"| Vno
| 140
|-
| align="center"| Vne
| 200 kias
|}

== Quick Startup ==
# Set fuel to 'Both'
# Turn on the master battery
# Turn on the fuel boost pump
# Turn on the left and right magneto switches
# After fuel pressure comes up, use the starter switch to start the engine
# Turn off fuel boost pump (optional)
# Turn on alternator switch
# Turn on avionics switch
# Set your altimeter to the proper pressure
# Check your heading gyros and set as necessary
# Set elevator trim as desired (the Velocity menu features a suggested setting)
# Release parking break when ready

:An automagic startup function can be found in the "Velocity" section of the menu bar.

== Steering and Brakes ==

The Velocity nose wheel casters and is not steerable. Steering is accomplished by differential braking. This makes the Velocity handle very tightly on the ground, but requires attention on takeoff until the rudders are effective.

The standard Velocity kit couples braking with rudder deflection, but like many builders, this model uses a toe-brake option to de-couple rudder and braking.

== Weight and Balance ==

The plane's default load is rather light, having a single pilot, some nose ballast and a modest fuel load. This makes the default experience exceptionally nimble and responsive. Use the Equipment menu to experience the more typical real-world load options.

The real Velocity is fairly sensitive to weight and balance. It's critically important not to have the CG too far back, which can result in flat stalls or other not so good behaviors. Changes to the Velocity's wings have largely eliminated the flat stalls, but careful attention to weight and balance is still essential for safe flying. The model's CG and weight have been configured using real-world Velocity weight and balance worksheets. See the file "velocity-xl-rg-yasim.xml" for more notes and information.

== Fuel ==

A Velocity XL with retractable gear has two 33 gallon tanks located in the leading half of the inboard wing segments known as the "strakes". Each tank is essentially a hollowed-out portion of the strake, provided with baffles and coated with fuel-proof epoxy. A corresponding sight gauge to either side of the rear seats indicates the load of each tank. A 4 gallon sump tank sits low against the firewall behind the rear seats, though only 2.5 gallons are usable. Note that the main panel fuel instrument shows the capacity of the two main tanks-- there is no readout for the sump. If your two main tanks are showing empty, you'd better have an airfield in sight.

The base Velocity build has a very simple fuel feed. Both tanks feed the sump which feeds the engine with no valves or selectors. Like some Velocity builders do, this model adds a fuel control switch to allow left-right-both-off settings.

You need the boost pump only for cold engine starting. After fuel pressure has come up and the engine is started, you should turn it off, otherwise it will cost you additional fuel. You might wish to leave it on during the early stages of your climb and turn it on for approach. The boost pump can be used to further richen the mixture if cylinder temps get too hot, but at the expense of extra fuel. Mixture is auto-enriched at high power settings, so you don't really need this on for take-off.

== Airbrakes ==

The Velocity's twin vertical stabs have independent one-way rudders; travel is outboard for each. Because of this both rudders can be deployed simultaneously, deflecting each rudder outboard as a form of speed braking. The effect is relatively weak but helpful. Expect a slight pitch-up effect when using the rudders in this way.

Since rudders can be deployed independently, the rudder pedals are not coupled in the standard Velocity build. This may not work with many rudder pedal sets, where the pedals pivot about a center point. In this case, you can use the ctrl-b function to toggle both rudders to maximum deflection. Note that rudder control is effectively disabled while set this way. An indicator light on the main panel displays this condition. This light isn't a real Velocity indicator, only a sim aid.

Some Velocity builds incorporate a bellyflap speedbrake for more effective airbraking. The model does not have this feature and won't until details become available on how the aircraft reacts to its deployment.

== Flying ==
[[File:Velocity-XL-RG exterior 02.jpg|thumb|270px]]
Normal flight is responsive and free of any quirks. The author is not a pilot, has never been in a Velocity, and makes no claim that the model flies true to the real thing. That said, the model conforms fairly closely to the pilot's handbook. If you stay within normal flight profiles it should not do anything peculiar.

'''Takeoff''' - Lift the nose at 60-70 kts, then rotate at 75, 80-85 if operating at heavy gross weights. Trimming for takeoff helps. Try not to touch the brakes too much to steer on the takeoff roll. The rudders will become effective above 25 kts. Don't rotate too far especially with a light load (aft CG), as you could place the CG aft of the main gear and tip the Velocity on its tail. (In the real Velocity you risk prop damage.) Never rotate the canard above the horizon.

The Velocity is a pusher-configuration, so expect propeller effects to be reversed from what you might be accustomed to.

'''Climb''' - Optimum climb is 100 knots. Best climb is 80, and for optimum visibility and cooling, 110. Climb with WOT (wide open throttle), reducing RPM as desired and leaning as desired.

'''Cruise''' - Consider running your Velocity at WOT and adjusting power using mixture and propeller controls. Remember to turn the fuel pump off. You should get your best economy this way. See the engine section for tips on power settings.

The model features the Lycoming IO-540-K 300 HP engine. With the default light load, this gives you a lot of power to play with, and is necessary to achieve the top end speeds. Note that while the design is capable of very high speeds in mild air, many Velocities don't achieve those speeds. Top speed depends on flight conditions, engine, the quality of the build, the propeller and pitch settings, and other factors.

'''Descent''' - Plan your descent well in advance of your destination. The Velocity is very slick and will take a while to shed speed. Although the simulation won't care, it's recommended that you reduce power gradually in increments of 1" every minute or so in order to minimize possible negative effects on your engine.

'''Approach''' - Enter the pattern at 85-90 kts, approach at 80. Flare slightly and land at 70-75. Add 5 knots for heavy loads. This is a very clean airplane-- don't approach too fast or you could easily double your runway needs. Again, plan your approach well in advance or you may need to go-around due to excessive speed. (This advice is straight out of the pilot's handbook for those who may be thinking this is an FDM flaw-- it's not. The Velocity is very slippery.) Use the rudder-brake to help control your descent, but remember to unlock it before crossing the threshold. Fly the aircraft down to the runway-- don't try to stall the aircraft to a landing or use excessive flare.

'''Stalls''' - Stall is listed at 65 kts, but varies considerably with the build and the load. The handbook reports the aircraft is manageable and responsive down to 60 kts with lighter loads.

Due to the canard configuration, a "stall" in the Velocity is more like a nose bobbing motion, where you can no longer keep the nose up. With the stick fully back in low-speed flight, you will reach a point where the elevator begins to stall before the wing, dropping the nose and picking up lift again such that the nose begins to come up. You may notice a slight oscillation in pitch when this begins to happen, called "pitch bucking". This video demonstrates the effect: http://www.youtube.com/watch?v=zeTjPPpVtuU Watch carefully for the pitching oscillations. For another demonstration: http://www.youtube.com/watch?v=M-dGCUsZvDY, at about 5:11 into the video.

Because the aircraft has small tires and an aft-mounted propeller, the Velocity is not recommended for rough or grass fields. The Velocity is also not recommended for short fields due to its relatively long runway needs.

== Avionics ==

Comm, Nav and ADF function as you would expect. Nav 1 (the top radio) is linked the the RMI in the bottom left corner. Nav 2 (the 2nd radio down) is linked to the CDI, bottom center. The ADF receiver (3rd panel down) operates on the RMI and the ADF. The ADF is superfluous, but is present for practice with such older instruments.

The audio board currently doesn't do much except provide marker beacon lights and the ability to disable the marker beacon receiver.

The transponder has no functionality, but it's there if you want to emulate procedures. It does have all the animations and control mappings necessary for operation, and could easily be adapted to work with any Flightgear transponder implementation.

For more on the avionics, see the file "README_avionics.txt".

== Engine Modeling ==

This Velocity model features a new and experimental engine simulation created by the author. The system replaces most YASim values with custom calculations. The system is based on maintaining reasonably correct air-fuel ratios combined with tabular data for engine temperatures and other information. The result allows you to find best power or best economy settings while keeping your cylinder temps reasonable.

The EDM (Engine Data Management) instrument is very loosely like a JP Instruments EDM. Its main function is to report engine cylinder EGT and CHT values. (The device does not yet model other EDM capabilities.) The EGT and CHT numbers report a kind of average value, though the individual bars do report true to their cylinders. I've taken some liberties with the size and positioning of the readouts for legibility.

Note that oil temperature reads in degrees Centigrade, while other temps are degrees Fahrenheit.

Play with the the power and mixture controls while watching EGT, the HP estimate, and fuel flow to find your best power or economy settings at your altitude. Best economy is approximately 50 degrees lean of peak EGT, while best power is about 80 degrees rich of peak EGT. The CHT values will tell you when you're getting into troubling regions. The default cylinder temperature ranges are set very conservatively so you shouldn't have any problems; just keep CHT's out of the red. Remember that EGT responds nearly instantaneously, while cylinder temps take a while to build up or cool down. The engine has an auto-rich feature, so as you push the throttle in beyond 65% you will also begin richening the mixture.

A real pilot will likely find the numbers a bit off-- the model's numbers are based on some real data, some data for similar engines, and some guesses. The author has no experience with these engines and what their temps do at various power settings. If you have experience with the Lycoming IO-540-K or similar and have better numbers, feel free to adjust the temperature tables found in "Systems/Velocity-XL-RG-engine.XML"; if you send me your recommended changes, I'll use them. See that file and the related nasal script for more information.

For notes on the development of this engine simulation, see:

*[http://www.buckarooshangar.com/flightgear/yasim_pistonengines.html Simulation of Piston Engine Fuel Consumption and Engine Temperature using YASim]

== Ground Shadow ==

The model features a simple object-based shadow to provide a reference when taking off and landing in chase view. It's enabled at elevations of less than 100m, when gear is down, and the sun is reasonably up. It works tolerably well for its purpose, especially when the sun is well up since it doesn't move with the sun (not worth the effort right now). If you don't like or need this fake shadow, simply disable it using the Velocity menu option. Your preference will be saved if you use the Flightgear exit option.

== Other Stuff ==

The three NACA scoops on the upper aft cabin are two engine cooling intake ducts, and a smaller cabin air intake. The engine cooling outlets are located to either side of the propeller. On the left side of the nose is another NACA scoop, this one is the intake for the secondary engine oil cooler (which also provides cabin heat). Below this and aft of the nose gear doors is the exhaust for the oil cooler. Some Velocity builds have an intake on the right side of the nose for a cabin air intake, and some have additional intakes in the engine cowl, probably for oil coolers and/or revised air intakes.

Those familiar with the aircraft may notice the lack of cowl retaining screws. I learned some builders create a retaining flange on the forward cowl that slips under the fuselage skin just aft of the firewall. That holds down the forward section. On the aft cowl, standard hardware hinges are fixed inside the cowl, half the hinge on the upper cowl, the other half on the lower cowl. They mate together perfectly, and the removable hinge pins holds the two hinge halves and therefore the cowl halves together. It's simple, hidden from view, has no screws to come loose and hit the prop, and looks clean. I thought it amazingly clever, and decided to assume my model uses that technique. And it saves me from exactly placing those damned screws.

A few external details are missing: the "sparrow strainer" which assists trimming the elevator at higher speeds and elevator counterweights, which the author simply forgot to model (sorry). The latter are hard to see anyway, so it's not a big deal. Inside, the rudder cables that run to the pedals are missing, but unless you know what to look for, you'd never notice this.

For more notes about the model, see the YASim configuration file and the nasal script files.

== External Links ==

For more information, updates, paint kits, etc., visit:

* [http://www.buckarooshangar.com/flightgear/ Buckaroo's Flightgear Projects]

[[Category:Civilian aircraft]]
[[Category:Civil utility aircraft]]
[[Category:Propeller aircraft]]
[[Category:Single-engine aircraft]]

Template:Model Gallery

2014-06-30T22:47:35Z

Buckaroo:

{{ #switch: {{{section|}}}
| carrier_borne_aircraft =
{{Gallery
| Buccaneer.jpg | [[Blackburn Buccaneer]]
| Douglas_A4.jpg | [[Douglas A-4 Skyhawk]]
| A-6E.jpg | [[Grumman A-6E|Grumman A-6E Intruder]]
| F-8E.jpg | [[F-8 Crusader]]
| F-14.jpg | [[Grumman F-14 Tomcat]]
| Hawker_Seahawk.jpg | [[Hawker Seahawk|Hawker Seahawk FGA6]]
}}
| experimental =
{{Gallery
| BAC_TSR-2_Prototype.jpg | [[BAC TSR-2 Prototype]]
| V22Osprey.jpg |[[Bell Boeing V22 Osprey | Bell V-22 Osprey]]
| X15.jpg | [[North American X-15]]
| YF-23.jpg | [[Northrop/McDonnell Douglas YF-23]]
}}
| helicopters =
{{Gallery
| Ah-1_vietnam_firebase.png | [[AH-1 Cobra]]
| H21c.jpg | [[Boeing-Vertol H21C]]
| CH-47 Chinook.jpg | [[CH-47 Chinook Helicopter]]
| Bo105.jpg | [[Eurocopter Bo105]]
| Ec135.jpg | [[Eurocopter EC135]]
| EC130.jpg | [[Eurocopter EC130 B4]]
| OH-6.png | [[Hughes OH-6 Cayuse]]
| WG13.jpg | [[Lynx WG13]]
| S51.jpg | [[Sikorsky S51]]
| S58.jpg | [[Sikorsky S58]]
| s76c_landed.jpg | [[Sikorsky S76C]]
| Uh60.jpg| [[Sikorsky UH60]]
| Aluette2.jpg | [[Aérospatiale Alouette II|Alouette II]]
| Hup-3.jpg | [[Piasecki HUP-3]]
| R22.jpg | [[Robinson R22]]
}}
| historical_aircraft =
{{Gallery
| Couzinet70.jpg |[[Couzinet 70]]
| dh91.jpg | [[De Havilland D.H. 91 Albatross]]
| Douglas_DC3.jpg | [[Douglas DC-3]]
| ComperSwift.jpg | [[ComperSwift Comper]]
| Lockheed_1049.jpg | [[Lockheed 1049|Lockheed Constellation]]
| 314.jpg | [[Boeing 314]]
| DHC-3.jpg | [[de Havilland Canada DHC-3 Otter]]
| 1903_Wright_Flyer.jpg | [[Wright Flyer (UIUC)]]
| Short_Empire.jpg | [[Short Empire]]
| Dc-3-splash.png | [[Douglas DC-3-C47]]
}}
| light_civilian_aircraft =
{{Gallery
| A24-liverie-default.png | [[Aeroprakt A24 Viking]]
| Aerostar_700.jpg | [[Aerostar 700]]
| FK9MK2.jpg | [[B&F FK9 Mark 2]]
| Beech99.jpg | [[Beechcraft Model 99]]
| Cessna_172P.jpg | [[Cessna C172|Cessna 172P]] (1982)
| Edgley_Optica_01.jpg | [[Edgley Optica]]
| Piper Cherokee Warrior II.png | [[Piper Cherokee Warrior II|Piper Cherokee Warrior II (PA28-161)]]
| Pa-24.jpg | [[Piper PA-24 Comanche|Piper Comanche (PA24-250)]]
| Piper j3cub.jpg | [[Piper J3 Cub]] (1946)
| Piper SenecaII.jpg | [[Piper PA34-200T Seneca II|Piper Seneca II (PA34-200T)]]
| dr400.jpg | [[Robin DR400]]
| DR400-dauphin.jpg | [[Robin DR400 Dauphin]]
| Rallye-MS893.jpg | [[Rallye-MS893E]]
| Piper_Dakota.png | [[Piper Dakota]]
| Velocity-XL-RG.jpg | [[Velocity XL RG]]
}}
| lighter_than_air =
{{Gallery
| Zeppelin_NT.jpg | [[Zeppelin NT]]
| ZF_Navy_free_balloon.jpg | [[ZF Navy free balloon]]
| Submarine_Scout.jpg | [[Submarine Scout]]
| Zeppelin_LZ_121_Nordstern.jpg | [[Zeppelin LZ 121 Nordstern]]
}}
| modern_airliners_narrowbody_midsize =
{{Gallery
| A320-family.jpg | [[Airbus A320 Family]]
| Beechcraft B1900D.png | [[Beechcraft B1900D]]
| 707.jpg | [[Boeing 707]]
| 717-200.jpg | [[Boeing 717]]
| 727-230.2.jpeg | [[Boeing 727-230]]
| 737-100.png | [[Boeing 737-100]]
| 737-300.jpg | [[Boeing 737-300]]
| Boeing 737-400 British Airways.jpg | [[Boeing 737-400]]
| 757-2002.jpg | [[Boeing 757]]
| Picture 11.png | [[Bombardier CRJ-200LR]]
| CRJ700.jpg | [[Bombardier CRJ700 series]]
| CessnaCitationX.jpg | [[Cessna Citation X]]
| Concorde.png | [[Concorde]]
| Fokker50.jpg | [[Fokker 50]]
| Tu154.jpg | [[Tupolev 154]]
}}
| modern_airliners_widebody_jumbo =
{{Gallery
| Airbus.png | [[Airbus A340-600]]
| A350.png | [[Airbus A350]]
| A380.jpg | [[Airbus A380]]
| 747-400.jpg | [[Boeing 747-400]]
| Boeing 767-300.png | [[Boeing 767-300]]
| 777-200.jpg | [[Boeing 777-200]]
| 787.png | [[Boeing 787]]
| IL-96-400 Jet Airways.bmp | [[IL-96-400 Long Ranger(T)]]
}}
| modern_military_aircraft =
{{Gallery
| A-10.jpg | [[Fairchild A-10]]
| B-52F.jpg | [[Boeing B-52]]
| E-3B.jpg | [[Boeing E-3 Sentry]]
| F-15C.jpg | [[F-15C Eagle]]
| F-80C.jpg | [[F-80C Shooting Star]]
| Harrier.jpg | [[British Aerospace Harrier]]
| General_Dynamics_F16.jpg | [[General Dynamics F-16]]
| Cessna T-37.jpg | [[Cessna T-37]]
| Dassault Mirage F.1 at altitude.png | [[Dassault Mirage F.1]]
| M20005prespic.png | [[Dassault Mirage 2000-5]]
| Northrop_T-38.jpg | [[Northrop T-38]]
| OV-10A2.jpg | [[North American OV-10A Bronco]]
| Saab_J35.jpg | [[Saab J 35Ã– Draken|Saab J35Ö Draken]]
| LCA.jpeg | [[HAL Tejas]]
| F-22.png | [[Lockheed Martin F-22 Raptor]]
| MiG-29_splash.png | [[Mikoyan-Gurevich_MiG-29]]
| PC-9M.jpg | [[Pilatus PC-9M]]
| PC-21.jpg | [[Pilatus PC-21]]
}}
| science_fiction =
{{Gallery
| bluebird_hovercraft.jpg | [[Bluebird]]
| UFO.jpg | [[UFO from the 'White Project' of the UNESCO]]
}}
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| Shuttle.jpg | [[Space Shuttle]]
| Vostok-1-Exterior.png | [[Vostok-1]]
}}
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| AirwaveXtreme150.jpg | [[Airwave Xtreme 150]]
| Hornet.jpg | [[GDT Hornet (autogyro)]]
| DG-101G_001.jpg | [[Glaser-Dirks DG-101G]]
| DG-300.jpg | [[Glaser-Dirks DG-300]]
| Dragonfly-towing.jpg | [[Dragonfly|Moyes Dragonfly]]
| Paraglider.jpg | [[Paraglider]]
| Asw20.jpg | [[ASW-20 sailplane|Schleicher ASW-20]]
| Sgs233.jpg | [[Schweizer 2-33]]
}}
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{{Gallery
| AerocarI_1.png | {{int|Taylor Aerocar}}
| Follow_me.jpg | {{int|Follow me}}
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| Lamborghini Murcielago LP640 March10.jpg | {{int|Lamborghini Murcielago}}
| M113AS3.jpg | {{int|M113AS3}}
| Mobile_Stairs.jpg | {{int|Mobile Stairs}}
| Pushback.jpg | {{int|Pushback}}
| Snowplow.jpg | {{int|Snowplow}}
}}
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| Beaufighter.png | [[Bristol Beaufighter]]
| Fokker_DrI.jpg | [[Fokker Dr.I]]
| P51d-mustang.png | [[P-51D Mustang]]
| A6M2_fgfs-screen-166.jpg | [[A6M2 Zero?]]
| ki-84.jpg | [[Nakajima Ki-84?]]
| Fw190.jpg | [[Focke-Wulf Fw 190]]
| Sopwith_Camel.png | [[Sopwith Camel]]
| Spitfire.jpg | [[Supermarine Spitfire]]
| MiG-15bis-Exterior.jpg | [[MiG-15]]
| F4u-park.jpg | [[F4U Corsair]]
| 109-1.png | [[Messerschmitt Bf 109]]
}}
}}<noinclude>

{{Informative template | 1=
__NOTOC__
== Goal ==
This template is used in aircraft/helicopter/vehicle gallery pages and their translations. By using and maintaining this template the translations of the gallery pages can be up to date and synchronised with the least required work possible.

This is the right place to add aircrafts to the lists in [[Aircraft]], [[:de:Flugzeuge]], [[:es:Aeronaves]], etc.

== Usage ==
<nowiki>{{</nowiki>'''Model Gallery''' <nowiki>|</nowiki>section=<nowiki>}}</nowiki>
; section: Section of aircraft to show. Must be one of the following or no gallery will be shown:
:* '''carrier_borne_aircraft'''
:* '''experimental'''
:* '''helicopters'''
:* '''historical_aircraft'''
:* '''light_civilian_aircraft'''
:* '''lighter_than_air'''
:* '''modern_airliners_narrowbody_midsize'''
:* '''modern_airliners_widebody_jumbo'''
:* '''modern_military_aircraft'''
:* '''science_fiction'''
:* '''spacecraft'''
:* '''ultra_light'''
:* '''vehicles'''
:* '''warbirds'''

== Example ==
<nowiki>{{Model Gallery |section=lighter_than_air}}</nowiki>
{{Model Gallery |section=lighter_than_air}}

}}

[[Category:Templates]]</noinclude>

Velocity XL RG

2014-06-30T22:39:27Z

Buckaroo: Created page with "{{infobox Aircraft |image =Velocity-XL-RG.jpg |alt =Velocity XL RG |name =Velocity XL RG |type = Civilian aircraft |livery = yes |authors = Gary Neely |status = |fdm = YASim..."

{{infobox Aircraft
|image =Velocity-XL-RG.jpg
|alt =Velocity XL RG
|name =Velocity XL RG
|type = Civilian aircraft
|livery = yes
|authors = Gary Neely
|status =
|fdm = YASim
|fgname = Velocity-XL-RG
|download = http://www.buckarooshangar.com/flightgear/Velocity_XL_RG.zip
}}
The Velocity XL is an American amateur-built aircraft produced by Velocity, Inc. Introduced in 1997, the Velocity XL (Extra Large) is an enlarged version of the Velocity SE, featuring a roomier cabin and accommodations for a larger engine. The Velocity XL is available to builders in kit form and features several kit variations, including options for retractable gear (the RG designator) and a belly-mounted airbrake. Using an IO 540 engine, the aircraft is capable of cruising up to 200 kt, and can achieve a range of over 1300 nm at 65% power.

== Aircraft Features ==
[[File:Velocity-XL-RG exterior 01.jpg|thumb|270px]]
=== Model ===
:The model was built using the factory builder's guide and several builder's blogs as references. All flight surfaces and moveable objects animate as expected, including the gull-wing doors. Engine/prop sound is based on a real Velocity IO-540.

=== Cabin Modeling ===
:Fully detailed cabin featuring complete instrumentation and avionics. The cabin is configured with variable lighting for night flights based on a real Velocity lighting installation.

=== Livery System ===
:The model features several livery schemes with both a 1024x1024 and a 2048x2048 version. The default livery is a light-weight 1024x1024 scheme that should play nicely in a multi-player environment.

=== Engine Simulation ===
:A unique engine simulation allows the pilot to monitor temperatures and fuel flow and set mixture settings for economy or power.

== Aircraft Controls ==
[[File:Velocity-XL-RG cabin 01.jpg|thumb|270px]]

=== Keyboard Shortcuts ===
{| class="wikitable" width="50%"
|-
! scope="col"| Key
! scope="col"| Binding
|-
| align="center"| {{key press|Ctrl|b}}
| Toggles both rudders to maximum deflection as airbrake
|}

:All other functions use Flightgear standard key mappings.

=== Clickable Levers and Sliders ===
Most levers and sliders in the cockpit are clickable. You can use LMB to increase value/position and MMB to decrease the value/position, or you can use the scroll wheel to make finer adjustments.

== Limitations ==
[[File:Velocity-XL-RG cabin 02.png|thumb|270px|Screenshot of Velocity XL RG main panel at night]]

{| class="wikitable" width="40%"
|-
! scope="col"|
! scope="col"| Speed in kts
|-
| align="center"| Vs
| 65
|-
| align="center"| Vr
| 75
|-
| align="center"| Vle
| 110
|-
| align="center"| Vlo
| 120
|-
| align="center"| Vno
| 140
|-
| align="center"| Vne
| 200 kias
|}

== Quick Startup ==
# Set fuel to 'Both'
# Turn on the master battery
# Turn on the fuel boost pump
# Turn on the left and right magneto switches
# After fuel pressure comes up, use the starter switch to start the engine
# Turn off fuel boost pump (optional)
# Turn on alternator switch
# Turn on avionics switch
# Set your altimeter to the proper pressure
# Check your heading gyros and set as necessary
# Set elevator trim as desired (the Velocity menu features a suggested setting)
# Release parking break when ready

:An automagic startup function can be found in the "Velocity" section of the menu bar.

== Steering and Brakes ==

The Velocity nose wheel casters and is not steerable. Steering is accomplished by differential braking. This makes the Velocity handle very tightly on the ground, but requires attention on takeoff until the rudders are effective.

The standard Velocity kit couples braking with rudder deflection, but like many builders, this model uses a toe-brake option to de-couple rudder and braking.

== Weight and Balance ==

The plane's default load is rather light, having a single pilot, some nose ballast and a modest fuel load. This makes the default experience exceptionally nimble and responsive. Use the Equipment menu to experience the more typical real-world load options.

The real Velocity is fairly sensitive to weight and balance. It's critically important not to have the CG too far back, which can result in flat stalls or other not so good behaviors. Changes to the Velocity's wings have largely eliminated the flat stalls, but careful attention to weight and balance is still essential for safe flying. The model's CG and weight have been configured using real-world Velocity weight and balance worksheets. See the file "velocity-xl-rg-yasim.xml" for more notes and information.

== Fuel ==

A Velocity XL with retractable gear has two 33 gallon tanks located in the leading half of the inboard wing segments known as the "strakes". Each tank is essentially a hollowed-out portion of the strake, provided with baffles and coated with fuel-proof epoxy. A corresponding sight gauge to either side of the rear seats indicates the load of each tank. A 4 gallon sump tank sits low against the firewall behind the rear seats, though only 2.5 gallons are usable. Note that the main panel fuel instrument shows the capacity of the two main tanks-- there is no readout for the sump. If your two main tanks are showing empty, you'd better have an airfield in sight.

The base Velocity build has a very simple fuel feed. Both tanks feed the sump which feeds the engine with no valves or selectors. Like some Velocity builders do, this model adds a fuel control switch to allow left-right-both-off settings.

You need the boost pump only for cold engine starting. After fuel pressure has come up and the engine is started, you should turn it off, otherwise it will cost you additional fuel. You might wish to leave it on during the early stages of your climb and turn it on for approach. The boost pump can be used to further richen the mixture if cylinder temps get too hot, but at the expense of extra fuel. Mixture is auto-enriched at high power settings, so you don't really need this on for take-off.

== Airbrakes ==

The Velocity's twin vertical stabs have independent one-way rudders; travel is outboard for each. Because of this both rudders can be deployed simultaneously, deflecting each rudder outboard as a form of speed braking. The effect is relatively weak but helpful. Expect a slight pitch-up effect when using the rudders in this way.

Since rudders can be deployed independently, the rudder pedals are not coupled in the standard Velocity build. This may not work with many rudder pedal sets, where the pedals pivot about a center point. In this case, you can use the ctrl-b function to toggle both rudders to maximum deflection. Note that rudder control is effectively disabled while set this way. An indicator light on the main panel displays this condition. This light isn't a real Velocity indicator, only a sim aid.

Some Velocity builds incorporate a bellyflap speedbrake for more effective airbraking. The model does not have this feature and won't until details become available on how the aircraft reacts to its deployment.

== Flying ==
[[File:Velocity-XL-RG exterior 02.jpg|thumb|270px]]
Normal flight is responsive and free of any quirks. The author is not a pilot, has never been in a Velocity, and makes no claim that the model flies true to the real thing. That said, the model conforms fairly closely to the pilot's handbook. If you stay within normal flight profiles it should not do anything peculiar.

'''Takeoff''' - Lift the nose at 60-70 kts, then rotate at 75, 80-85 if operating at heavy gross weights. Trimming for takeoff helps. Try not to touch the brakes too much to steer on the takeoff roll. The rudders will become effective above 25 kts. Don't rotate too far especially with a light load (aft CG), as you could place the CG aft of the main gear and tip the Velocity on its tail. (In the real Velocity you risk prop damage.) Never rotate the canard above the horizon.

The Velocity is a pusher-configuration, so expect propeller effects to be reversed from what you might be accustomed to.

'''Climb''' - Optimum climb is 100 knots. Best climb is 80, and for optimum visibility and cooling, 110. Climb with WOT (wide open throttle), reducing RPM as desired and leaning as desired.

'''Cruise''' - Consider running your Velocity at WOT and adjusting power using mixture and propeller controls. Remember to turn the fuel pump off. You should get your best economy this way. See the engine section for tips on power settings.

The model features the Lycoming IO-540-K 300 HP engine. With the default light load, this gives you a lot of power to play with, and is necessary to achieve the top end speeds. Note that while the design is capable of very high speeds in mild air, many Velocities don't achieve those speeds. Top speed depends on flight conditions, engine, the quality of the build, the propeller and pitch settings, and other factors.

'''Descent''' - Plan your descent well in advance of your destination. The Velocity is very slick and will take a while to shed speed. Although the simulation won't care, it's recommended that you reduce power gradually in increments of 1" every minute or so in order to minimize possible negative effects on your engine.

'''Approach''' - Enter the pattern at 85-90 kts, approach at 80. Flare slightly and land at 70-75. Add 5 knots for heavy loads. This is a very clean airplane-- don't approach too fast or you could easily double your runway needs. Again, plan your approach well in advance or you may need to go-around due to excessive speed. (This advice is straight out of the pilot's handbook for those who may be thinking this is an FDM flaw-- it's not. The Velocity is very slippery.) Use the rudder-brake to help control your descent, but remember to unlock it before crossing the threshold. Fly the aircraft down to the runway-- don't try to stall the aircraft to a landing or use excessive flare.

'''Stalls''' - Stall is listed at 65 kts, but varies considerably with the build and the load. The handbook reports the aircraft is manageable and responsive down to 60 kts with lighter loads.

Due to the canard configuration, a "stall" in the Velocity is more like a nose bobbing motion, where you can no longer keep the nose up. With the stick fully back in low-speed flight, you will reach a point where the elevator begins to stall before the wing, dropping the nose and picking up lift again such that the nose begins to come up. You may notice a slight oscillation in pitch when this begins to happen, called "pitch bucking". This video demonstrates the effect: http://www.youtube.com/watch?v=zeTjPPpVtuU Watch carefully for the pitching oscillations. For another demonstration: http://www.youtube.com/watch?v=M-dGCUsZvDY, at about 5:11 into the video.

Because the aircraft has small tires and an aft-mounted propeller, the Velocity is not recommended for rough or grass fields. The Velocity is also not recommended for short fields due to its relatively long runway needs.

== Avionics ==

Comm, Nav and ADF function as you would expect. Nav 1 (the top radio) is linked the the RMI in the bottom left corner. Nav 2 (the 2nd radio down) is linked to the CDI, bottom center. The ADF receiver (3rd panel down) operates on the RMI and the ADF. The ADF is superfluous, but is present for practice with such older instruments.

The audio board currently doesn't do much except provide marker beacon lights and the ability to disable the marker beacon receiver.

The transponder has no functionality, but it's there if you want to emulate procedures. It does have all the animations and control mappings necessary for operation, and could easily be adapted to work with any Flightgear transponder implementation.

For more on the avionics, see the file "README_avionics.txt".

== Engine Modeling ==

This Velocity model features a new and experimental engine simulation created by the author. The system replaces most YASim values with custom calculations. The system is based on maintaining reasonably correct air-fuel ratios combined with tabular data for engine temperatures and other information. The result allows you to find best power or best economy settings while keeping your cylinder temps reasonable.

The EDM (Engine Data Management) instrument is very loosely like a JP Instruments EDM. Its main function is to report engine cylinder EGT and CHT values. (The device does not yet model other EDM capabilities.) The EGT and CHT numbers report a kind of average value, though the individual bars do report true to their cylinders. I've taken some liberties with the size and positioning of the readouts for legibility.

Note that oil temperature reads in degrees Centigrade, while other temps are degrees Fahrenheit.

Play with the the power and mixture controls while watching EGT, the HP estimate, and fuel flow to find your best power or economy settings at your altitude. Best economy is approximately 50 degrees lean of peak EGT, while best power is about 80 degrees rich of peak EGT. The CHT values will tell you when you're getting into troubling regions. The default cylinder temperature ranges are set very conservatively so you shouldn't have any problems; just keep CHT's out of the red. Remember that EGT responds nearly instantaneously, while cylinder temps take a while to build up or cool down. The engine has an auto-rich feature, so as you push the throttle in beyond 65% you will also begin richening the mixture.

A real pilot will likely find the numbers a bit off-- the model's numbers are based on some real data, some data for similar engines, and some guesses. The author has no experience with these engines and what their temps do at various power settings. If you have experience with the Lycoming IO-540-K or similar and have better numbers, feel free to adjust the temperature tables found in "Systems/Velocity-XL-RG-engine.XML"; if you send me your recommended changes, I'll use them. See that file and the related nasal script for more information.

For notes on the development of this engine simulation, see:

*[http://www.buckarooshangar.com/flightgear/yasim_pistonengines.html Simulation of Piston Engine Fuel Consumption and Engine Temperature using YASim]

== Ground Shadow ==

The model features a simple object-based shadow to provide a reference when taking off and landing in chase view. It's enabled at elevations of less than 100m, when gear is down, and the sun is reasonably up. It works tolerably well for its purpose, especially when the sun is well up since it doesn't move with the sun (not worth the effort right now). If you don't like or need this fake shadow, simply disable it using the Velocity menu option. Your preference will be saved if you use the Flightgear exit option.

== Other Stuff ==

The three NACA scoops on the upper aft cabin are two engine cooling intake ducts, and a smaller cabin air intake. The engine cooling outlets are located to either side of the propeller. On the left side of the nose is another NACA scoop, this one is the intake for the secondary engine oil cooler (which also provides cabin heat). Below this and aft of the nose gear doors is the exhaust for the oil cooler. Some Velocity builds have an intake on the right side of the nose for a cabin air intake, and some have additional intakes in the engine cowl, probably for oil coolers and/or revised air intakes.

Those familiar with the aircraft may notice the lack of cowl retaining screws. I learned some builders create a retaining flange on the forward cowl that slips under the fuselage skin just aft of the firewall. That holds down the forward section. On the aft cowl, standard hardware hinges are fixed inside the cowl, half the hinge on the upper cowl, the other half on the lower cowl. They mate together perfectly, and the removable hinge pins holds the two hinge halves and therefore the cowl halves together. It's simple, hidden from view, has no screws to come loose and hit the prop, and looks clean. I thought it amazingly clever, and decided to assume my model uses that technique. And it saves me from exactly placing those damned screws.

A few external details are missing: the "sparrow strainer" which assists trimming the elevator at higher speeds and elevator counterweights, which the author simply forgot to model (sorry). The latter are hard to see anyway, so it's not a big deal. Inside, the rudder cables that run to the pedals are missing, but unless you know what to look for, you'd never notice this.

For more notes about the model, see the YASim configuration file and the nasal script files.

== External Links ==

For more information, updates, paint kits, etc., visit:

* [http://www.buckarooshangar.com/flightgear/ Buckaroo's Flightgear Projects]

[[Category:Civilian aircraft]]
[[Category:Civil utility aircraft]]
[[Category:Propeller aircraft]]
[[Category:Single-engine aircraft]]

File:Velocity-XL-RG cabin 02.png

2014-06-30T22:28:04Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Velocity XL RG main panel at night}}
|date=2014-06-30 18:27:27
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of cabins]]

File:Velocity-XL-RG cabin 01.jpg

2014-06-30T22:26:47Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Velocity XL RG cabin interior showing main panel}}
|date=2011-12-18 04:53:13
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of cabins]]

File:Velocity-XL-RG exterior 02.jpg

2014-06-30T22:24:59Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Velocity XL RG exterior}}
|date=2011-12-29 18:26:23
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of civil utility aircraft]]

File:Velocity-XL-RG exterior 01.jpg

2014-06-30T22:23:06Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Velocity XL RG exterior}}
|date=2011-10-10 01:39:16
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of civil utility aircraft]]

File:Velocity-XL-RG.jpg

2014-06-30T19:33:27Z

Buckaroo: User created page with UploadWizard

=={{int:filedesc}}==
{{Information
|description={{en|1=Screenshot of Velocity XL RG}}
|date=2011-12-18 22:32:51
|source={{own}}
|author=[[User:Buckaroo|Buckaroo]]
|permission=
|other_versions=
}}

=={{int:license-header}}==
{{self|cc-by-sa-3.0}}

[[Category:Screenshots of civil utility aircraft]]

Aircraft

2014-06-16T02:23:41Z

Buckaroo: Changed the second paragraph to reflect the fact that many models shown are contributed from non-official hangars.

This list is not updated to include all the official [[GNU General Public License|GPL licensed]] '''aircraft''' for [[FlightGear]], but gives a visual sampling of the different types of aircraft and genres of aircraft officially available. See [[Table of models]] for a more comprehensive list.

Most models shown here are available from the official FlightGear project and can be downloaded at [http://www.flightgear.org/download/aircraft-v2-6/ FlightGear.org], with installation typically requiring an unzipping program and manual [[Howto: Install aircraft|installation]] in the FlightGear aircraft directory. Some models shown here are available from [[FlightGear hangars|non-official hangars]].

FlightGear aircraft features, quality, and compatibility vary significantly. Their development is dependent on the [[volunteer]]s who worked on them, with exception of some University and Government funded projects. Aircraft are listed by completeness status in [[:Category:Aircraft by status]].

=== Light civilian aircraft ===
The Cessna 172 is the default aircraft in FGFS 2.0. These aircraft typically have 1-2 piston engines, props, and avionics geared towards those with civilian pilot licenses.
{{Model Gallery | section=light_civilian_aircraft}}

=== Modern Airliners ===
These typically have 2-4 turbofan engines and some of the more complicated takeoff and landing procedures (such as multiple [[flaps]]). In addition, avionics in real life is geared towards those with professional pilots licenses and special certifications. However, the simplifications of FG make it much easier to fly in the simulation.

==== Narrowbody & Midsize ====
{{Model Gallery| section=modern_airliners_narrowbody_midsize}}

==== Widebody & Jumbo Airliners ====
{{Model Gallery| section=modern_airliners_widebody_jumbo}}

=== Helicopters ===
{{Main article|Helicopter}}

Helicopters have fundamentally different controls than fixed wing aircraft (see ''[[Flying the Helicopter]]''). Modern helicopter typically feature 1-2 turbine engines, which power a main rotor with 2-6 blades.
{{Model Gallery| section=helicopters}}

=== Gliders, Sailplanes, & Ultralights ===
These typically have the simplest controls, with minimal avionics. Flying [[:Category:Gliders|gliders]] or sailplanes using [[Soaring|thermals]] can provide more complicated experience. Ultralights on the other hand are among the simplest aircraft in FG.
{{Model Gallery| section=ultra_light}}

=== Warbirds ===
FlightGear includes a wide variety of vintage military aircraft. Complexity and realism is typically tied to the level of development work with a specific aircraft.
{{Model Gallery| section=warbirds}}

=== Carrier-borne aircraft ===
FlightGear supports landing on and taking off from [[carriers]].
{{Model Gallery| section=carrier_borne_aircraft}}

=== Modern military aircraft ===
FlightGear has a wide variety of modern and retired military jets available, highlighted by features such as air-to-air refueling from the venerable KC-135 and the ability to simulate A-10 ordnance release.
{{Model Gallery| section=modern_military_aircraft}}

=== Historical ===
Many obscure to famous older aircraft of varying quality are available.
{{Model Gallery| section=historical_aircraft}}

=== Experimental & Unique ===
Experimental and special purpose aircraft.
{{Model Gallery| section=experimental}}

=== Lighter than air aircraft (Available from version 1.9.0) ===
These aircraft take advantage of lighter than air gas to become buoyant. In addition to typical aircraft control methods such as elevator, rudder and engine throttle, ballast and control of gas volume and pressure become options.
{{Model Gallery| section=lighter_than_air}}

=== Science Fiction ===
Alternative models provide a diversion of realistic simulation, but can also be useful for exploring scenery.
{{Model Gallery| section=science_fiction}}

=== Spacecrafts ===
Things that show how small our planet Earth really is.
{{Model Gallery| section=spacecraft}}

== See Also ==
[[How to install aircraft]]
<br />
[[Aircraft deployment]]
<br />
[[Airliner Development Status]]



[[it:Aerei]]

[[Category:Lists]]
[[Category:Aircraft| ]]

[[de:Flugzeuge]]
[[es:Avión]]
[[fi:Lentokoneet]]
[[fr:Avions]]
[[nl:Luchtvaartuigen]]
[[pt:Avião]]
[[ru:Самолет]]

YASim

2013-06-17T17:32:57Z

Buckaroo: M$ -> Windows. Removed unnecessary OS bias.

'''YASim''' is one of two [[flight dynamics model]]s commonly used in [[FlightGear]]. The flight dynamics model (FDM) determines how the [[aircraft]] moves and flies.

Gary Neely wrote in his [http://www.buckarooshangar.com/flightgear/ introduction to YASim]:

:''The FDM is the mathematical model that controls the physics of flight within the simulator. The physical 3D aircraft model has nothing to do with flight dynamics-- in essence it's just a picture to look at. It's the FDM that dictates how the model flies.''

:''Why YASim? YASim uses the geometry of the aircraft to generate the base flight characteristics. While this suggests a 'realistic' or out-of-the-box approach, it is a only rough approximation that will require much tweaking before you get a result that approaches realism. If you have solid flight data for your aircraft such as wind-tunnel data or you are looking to eventually generate a hyper-realistic simulation, JSBSim is probably a better approach. If you lack such data but know the geometry of the aircraft and have access to the same flight characteristics and limits as a real pilot would, then YASim can provide a solution that is more than sufficient for most simulation needs.''

===Coordinate system notes===
All positions specified are in metres (which is weird, since all other units in the file are English). The X axis points forward, Y is left, and Z is up. Take your right hand, and hold it like a gun. Your first and second fingers are the X and Y axes, and your upwards-pointing thumb is the Z. This is slightly different from the coordinate system used by [[JSBSim]]. Sorry. The origin can be placed anywhere, so long as you are consistent. I use the nose of the aircraft.

=== [[XML]] Elements ===
==== airplane ====
The top-level element for the file. It contains only one attribute:
* '''mass:''' The empty (no fuel) weight, in pounds. It does include the weight of the engine(s), so when you add the engine weight in its tag, it acts just like a ballast.

==== approach ====
The approach parameters for the aircraft. The solver will generate an aircraft that matches these settings. The element can (and should) contain <control> elements indicating pilot input settings, such as flaps and throttle, for the approach.
* '''speed:''' The approach airspeed, in knots TAS.
* '''aoa:''' The approach angle of attack, in degrees
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cruise ====
The cruise speed and altitude for the solver to match. As above, this should contain <control> elements indicating aircraft configuration. Especially, make sure the engines are generating enough thrust at cruise!
* '''speed:''' The cruise speed, in knots TAS.
* '''alt:''' The cruise altitude, in feet MSL.
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cockpit ====
The location of the cockpit (pilot eyepoint).
* '''x,y,z:''' eyepoint location (see coordinates note)

==== fuselage ====
This defines a tubelike structure. It will be given an even mass and aerodynamic force distribution by the solver. You can have as many as you like, in any orientation you please.
* '''ax,ay,az:''' One end of the tube (typically the front)
* '''bx,by,bz:''' The other ("back") end.
* '''width:''' The width of the tube, in metres.
* '''taper:''' The approximate radius at the "tips" of the fuselage expressed as a fraction (0-1) of the width value.
* '''midpoint:''' The location of the widest part of the fuselage, expressed as a fraction of the distance between A and B.
* '''idrag:''' Multiplier for the "induced drag" generated by this object. Default is one. With idrag=0 the fuselage generates only drag.
* '''cx,cy,cz:''' Factors for the generated drag in the fuselages "local coordinate system" with x pointing from end to front, z perpendicular to x with y=0 in the aircraft coordinate system. E.g. for a fuselage of a height of 2 times them width you can define cy=2 and (due to the doubled front surface) cx=2.

==== Surfaces ====
===== wing =====
This defines the main wing of the aircraft. You can have only one (but see below about using vstab objects for extra lifting surfaces). The wing should have a <stall> subelement to indicate stall behavior, control surface subelements (flap0, flap1, spoiler, slat) to indicate what and where the control surfaces are, and <control> subelements to map user input properties to the control surfaces.
* '''x,y,z:''' The "base" of the wing, specified as the location of the mid-chord (not leading edge, trailing edge, or aerodynamic center) point at the root of the LEFT (!) wing.
* '''length:''' The length from the base of the wing to the midchord point at the tip. Note that this is not the same thing as span.
* '''chord:''' The chord of the wing at its base, along the X axis (not normal to the leading edge, as it is sometimes defined).
* '''incidence:''' The incidence angle at the wing root, in degrees. Zero is level with the fuselage (as in an aerobatic plane), positive means that the leading edge is higher than the trailing edge (as in a trainer).
* '''twist:''' The difference between the incidence angle at the wing root and the incidence angle at the wing tip. Typically, this is a negative number so that the wing tips have a lower angle of attack and stall after the wing root (washout).
* '''taper:''' The taper fraction, expressed as the tip chord divided by the root chord. A taper of one is a hershey bar wing, and zero would be a wing ending at a point. Defaults to one.
* '''sweep:''' The sweep angle of the wing, in degrees. Zero is no sweep, positive angles are swept back. Defaults to zero.
* '''dihedral:''' The dihedral angle of the wing. Positive angles are upward dihedral. Defaults to zero.
* '''idrag:''' Multiplier for the "induced drag" generated by this surface. In general, low aspect wings will generate less induced drag per-AoA than high aspect (glider) wings. This value isn't constrained well by the solution process, and may require tuning to get throttle settings correct in high AoA (approach) situations.
* '''effectiveness:''' Multiplier for the "normal" drag generated by the wing. Defaults to 1. Arbitrary, dimensionless factor.
* '''camber:''' The lift produced by the wing at zero angle of attack, expressed as a fraction of the maximum lift produced at the stall AoA.

===== hstab =====
These defines the horizontal stabilizer of the aircraft. Internally, it is just a wing object and therefore works the same in XML. You are allowed only one hstab object; the solver needs to know which wing's incidence to play with to get the aircraft trimmed correctly.

===== vstab =====
A "vertical" stabilizer. Like hstab, this is just another wing, with a few special properties. The surface is not "mirrored" as are wing and hstab objects. If you define a left wing only, you'll only get a left wing. The default dihedral, if unspecified, is 90 degrees instead of zero. But all parameters are equally settable, so there's no requirement that this object be "vertical" at all. You can use it for anything you like, such as extra wings for biplanes. Most importantly, these surfaces are not involved with the solver computation, so you can have none, or as many as you like.

===== mstab =====
A mirrored horizontal stabilizer. Exactly the same as wing, but not involved with the solver computation, so you can have none, or as many as you like.

===== stall =====
A subelement of a wing (or hstab/vstab/mstab) that specifies the stall behavior.
* '''aoa:''' The stall angle (maximum lift) in degrees. Note that this is relative to the wing, not the fuselage (since the wing may have a non-zero incidence angle).
* '''width:''' The "width" of the stall, in degrees. A high value indicates a gentle stall. Low values are viscious for a non-twisted wing, but are acceptable for a twisted one (since the whole wing will not stall at the same time).
* '''peak:''' The height of the lift peak, relative to the post-stall secondary lift peak at 45 degrees. Defaults to 1.5. This one is deep voodoo, and probably doesn't need to change much. Bug me for an explanation if you're curious.

===== flap0, flap1, slat, spoiler =====
These are subelements of wing/hstab/vstab objects, and specify the location and effectiveness of the control surfaces.
* '''start:''' The position along the wing where the control surface begins.Zero is the root, one is the tip.
* '''end:''' The position where the surface ends, as above.
* '''lift:''' The lift multiplier for a flap or slat at full extension. One is a no-op, a typical aileron might be 1.2 or so, a giant jetliner flap 2.0, and a spoiler 0.0. For spoilers, the interpretation is a little different -- they spoil only "prestall" lift. Lift due purely to "flat plate" effects isn't affected. For typical wings that stall at low AoA's essentially all lift is pre-stall and you don't have to care. Jet fighters tend not to have wing spoilers, for exactly this reason. This value is not applicable to slats, which affect stall AoA only.
* '''drag:''' The drag multiplier, as above. Typically should be higher than the lift multiplier for flaps.
* '''aoa:''' Applicable only to slats. This indicates the angle by which the stall AoA is translated by the slat extension.

==== Engine ====
===== Thruster =====
A very simple "thrust only" engine object. Useful for things like thrust vectoring nozzles. All it does is map its THROTTLE input axis to its output thrust rating. Does not consume fuel, etc...
* '''thrust:''' Maximum thrust in pounds
* '''x,y,z:''' The point on the airframe where thrust will be applied.
* '''vx,vy,vy:''' The direction of the thrust in airframe coordinates. The vector will be normalized automatically, so any non-zero vector will work fine.

===== Jet =====
A turbojet/fan engine. It accepts a <control> subelement to map a property to its throttle setting, and an <actionpt> subelement to place the action point of the thrust at a different position than the mass of the engine.
* '''x,y,z:''' The location of the engine, as a point mass. If no actionpt is specified, this will also be the point of application of thrust.
* '''mass:''' The mass of the engine, in pounds.
* '''thrust:''' The maximum sea-level thrust, in pounds.
* '''afterburner:''' Maximum total thrust with afterburner/reheat, in pounds [defaults to "no additional thrust"].
* '''rotate:''' Vector angle of the thrust in degrees about the Y axis [0].
* '''n1-idle:''' Idling low pressure core / fan speed [55].
* '''n1-max:''' Maximum low pressure core / fan speed [102].
* '''n2-idle:''' Idling high pressure core speed [73].
* '''n2-max:''' Maximum high pressure core speed [103].
* '''tsfc:''' Thrust-specific fuel consumption [0.8]. This should be considerably lower for modern turbofans.
* '''egt:''' Exhaust gas temperature at takeoff in K [1050].
* '''epr:''' Engine pressure ratio at takeoff [3.0].
* '''exhaust-speed:''' The maximum exhaust speed in knots [~1555].
* '''spool-time:''' Time, in seconds, for the engine to respond to 90% of a commanded powersetting.

===== Propeller =====
A propeller. This element requires an engine subtag. Currently <piston-engine> and <turbine-engine> are supported.
* '''x,y,z:''' The position of the mass (!) of the engine/propeller combination. If the point of force application is different (and it will be) it should be set with an <actionpt> subelement.
* '''mass:''' The mass of the engine/propeller, in pounds.
* '''moment:''' The moment, in kg-metres^2. This has to be hand calculated and guessed at for now. A more automated system will be forthcoming. Use a negative moment value for counter-rotating ("European" -- CCW as seen from behind the prop) propellers. A good guess for this value is the radius of the prop (in metres) squared times the mass (kg) divided by three; that is the moment of a plain "stick" bolted to the prop shaft.
* '''radius:''' The radius, in metres, or the propeller.
* '''cruise-speed:''' The max efficiency cruise speed of the propeller. Generally not the same as the aircraft's cruise speed.
* '''cruise-rpm:''' The RPM of the propeller at max-eff. cruise.
* '''cruise-power:''' The power sunk by the prop at cruise, in horsepower.
* '''cruise-alt:''' The reference cruise altitude in feet.
* '''takeoff-power:''' The takeoff power required by the propeller...
* '''takeoff-rpm:''' ...at the given takeoff RPM.
* '''min-rpm:''' The minimum operational RPM for a constant speed propeller. This is the speed to which the prop governor will seek when the blue lever is at minimum. The coarse-stop attribute limits how far the governor can go into trying to reach this RPM.
* '''max-rpm:''' The maximum operational RPM for a constant speed propeller. See above. The fine-stop attribute limits how far the governor can go in trying to reach this RPM.
* '''fine-stop:''' The minimum pitch of the propeller (high RPM) as a ratio of ideal cruise pitch. This is set to 0.25 by default -- a higher value will result in a lower RPM at low power settings (e.g. idle, taxi, and approach).
* '''coarse-stop:''' The maximum pitch of the propeller (low RPM) as a ratio of ideal cruise pitch. This is set to 4.0 by default -- a lower value may result in a higher RPM at high power settings.
* '''gear-ratio:''' The factor by which the engine RPM is multiplied to produce the propeller RPM. Optional (defaults to 1.0).
* '''contra:''' When set (contra="1"), this indicates that the propeller is a contra-rotating pair. It will not contribute to the aircraft's net gyroscopic moment, nor will it produce asymmetric torque on the aircraft body. Asymmetric slipstream effects, when implemented, will also be zero when this is set.
* '''piston-engine:''' A piston engine definition. This must be a subelement of an enclosing <propeller> tag.
* '''eng-power:''' Maximum BHP of the engine at sea level.
* '''eng-rpm:''' The engine RPM at which eng-power is developed
* '''displacement:''' The engine displacement in cubic inches.
* '''compression:''' The engine compression ratio.

==== Landing gear ====
===== gear =====
Defines a landing gear. Accepts <control> subelements to map properties to steering and braking. Can also be used to simulate floats. Although the coefficients are still called ..fric, it is calculated in fluids as a drag (proportional to the square of the speed). In fluids gears are not considered to detect crashes (as on ground).
* '''x,y,z:''' The location of the fully-extended gear tip.
* '''compression:''' The distance in metres along the "up" axis that the gear will compress.
* '''initial-load:''' The initial load of the spring in multiples of compression. Defaults to 0. (With this parameter a lower spring-constants will be used for the gear-> can reduce numerical problems (jitter)) '''Note:''' the spring-constant is varied from 0% compression to 20% compression to get continuous behavior around 0 compression. (could be physically explained by wheel deformation)
* '''upx/upy/upz:''' The direction of compression, defaults to vertical (0,0,1) if unspecified. These are used only for a direction -- the vector need not be normalized, as the length is specified by "compression".
* '''sfric:''' Static (non-skidding) coefficient of friction. Defaults to 0.8.
* '''dfric:''' Dynamic friction. Defaults to 0.7.
* '''spring:''' A dimensionless multiplier for the automatically generated spring constant. Increase to make the gear stiffer, decrease to make it squishier.
* '''damp:''' A dimensionless multiplier for the automatically generated damping coefficient. Decrease to make the gear "bouncier", increase to make it "slower". Beware of increasing this too far: very high damping forces can make the numerics unstable. If you can't make the gear stop bouncing with this number, try increasing the compression length instead.
* '''on-water:''' if this is set to "0" the gear will be ignored if on water. Defaults to "0"
* '''on-solid:''' if this set to "0" the gear will be ignored if not on water. Defaults to "1"
* '''speed-planing:'''
* '''spring-factor-not-planing:''' At zero speed the spring factor is multiplied by spring-factor-not-planing. Above speed-planing this factor is equal to 1. The idea is, to use this for floats simulating the transition from swimming to planing. speed-planing defaults to 0, spring-factor-not-planing defaults to 1.
* '''reduce-friction-by-extension:''' at full extension the friction is reduced by this relative value. 0.7 means 30% friction at full extension. If you specify a value greater than one, the friction will be zero before reaching full extension. Defaults to "0"
* '''ignored-by-solver:''' with the on-water/on-solid tags you can have more than one set of gears in one aircraft, If the solver (who automatically generates the spring constants) would take all gears into account, the result would be wrong. E. G. set this tag to "1" for all gears, which are not active on runways. Defaults to "0". You can not exclude all gears in the solving process.

===== Launchbar =====
Defines a catapult launchbar or strop.
* '''x,y,z:''' The location of the mount point of the launch bar or strop on the aircraft.
* '''length:''' The length of the launch bar from mount point to tip
* '''down-angle:''' The max angle below the horizontal the launchbar can achieve.
* '''up-angle:''' The max angle above the horizontal the launchbar can achieve.
* '''holdback-{x,y,z}:''' The location of the holdback mount point on the aircraft.
* '''holdback-length:''' The length of the holdback from mount point to tip. Note: holdback up-angle and down-angle are the same as those defined for the launchbar and are not specified in the configuration.

==== Fuel ====
===== tank =====
A fuel tank. Tanks in the aircraft are identified numerically (starting from zero), in the order they are defined in the file. If the left tank is first, "tank[0]" will be the left tank.
* '''x,y,z:''' The location of the tank.
* '''capacity:''' The maximum contents of the tank, in pounds. Not gallons -- YASim supports fuels of varying densities.
* '''jet:''' A boolean. If present, this causes the fuel density to be treated as Jet-A. Otherwise, gasoline density is used. A more elaborate density setting (in pounds per gallon, for example) would be easy to implement. Bug me.

==== Center of Gravity ====

===== Ballast =====
This is a mechanism for modifying the mass distribution of the aircraft. A ballast setting specifies that a particular amount of the empty weight of the aircraft must be placed at a given location. The remaining non-ballast weight will be distributed "intelligently" across the fuselage and wing objects. Note again: this does NOT change the empty weight of the aircraft.
* '''x,y,z:''' The location of the ballast.
* '''mass:''' How much mass, in pounds, to put there. Note that this value can be negative. I find that I often need to "lighten" the tail of the aircraft.

===== Weight =====
This is an added weight, something not part of the empty weight of the aircraft, like passengers, cargo, or external stores. The actual value of the mass is not specified here, instead, a mapping to a property is used. This allows external code, such as the panel, to control the weight (loading a given cargo configuration from preference files, dropping bombs at runtime, etc...)
* '''x,y,z:''' The location of the weight.
* '''mass-prop:''' The name of the fgfs property containing the mass, in pounds, of this weight.
* '''size:''' The aerodynamic "size", in metres, of the object. This is important for external stores, which will cause drag. For reasonably aerodynamic stuff like bombs, the size should be roughly the width of the object. For other stuff, you're on your own. The default is zero, which results in no aerodynamic force (internal cargo).
* '''solve-weight:''' Subtag of approach and cruise parameters. Used to specify a non-zero setting for a <weight> tag during solution. The default is to assume all weights are zero at the given performance numbers.
* '''idx:''' Index of the weight in the file (starting with zero).
* '''weight:''' Weight setting in pounds.

==== Controls ====
===== control-input =====
This element manages a mapping from fgfs properties (user input) to settable values on the aircraft's objects. Note that the value to be set MUST (!) be valid on the given object type. This is not checked for by the parser, and will cause a runtime crash if you try it. Wing's don't have throttle controls, etc... Note that multiple axes may be set on the same value. They are summed before setting.
* '''axis:''' The name of the double-valued fgfs property "axis" to use as input, such as "/controls/flight/aileron".
* '''control:''' Which control axis to set on the objects. It can have the following values:
** THROTTLE - The throttle on a jet or propeller.
** MIXTURE - The mixture on a propeller.
** REHEAT - The afterburner on a jet
** PROP - The propeller advance
** BRAKE - The brake on a gear.
** STEER - The steering angle on a gear.
** INCIDENCE - The incidence angle of a wing.
** FLAP0 - The flap0 deflection of a wing.
** FLAP1 - The flap1 deflection of a wing.
** SLAT - The slat extension of a wing.
** SPOILER - The spoiler extension for a wing.
** CYCLICAIL - The "aileron" cyclic input of a rotor
** CYCLICELE - The "elevator" cyclic input of a rotor
** COLLECTIVE - The collective input of a rotor
** ROTORENGINEON - If not equal zero the rotor is rotating
** WINCHRELSPEED - The relative winch speed
** {... and many more, see FGFDM.cpp ...}
* '''invert:''' Negate the value of the property before setting on the object.
* '''split:''' Applicable to wing control surfaces. Sets the normal value on the left wing, and a negated value on the right wing.
* '''square:''' Squares the value before setting. Useful for controls like steering that need a wide range, yet lots of sensitivity in the center. Obviously only applicable to values that have a range of [-1:1] or [0:1].
* '''src0/src1/dst0/dst1:''' If present, these defined a linear mapping from the source to the output value. Input values in the range src0-src1 are mapped linearly to dst0-dst1, with clamping for input values that lie outside the range.

===== control-output =====
This can be used to pass the value of a YASim control axis (after all mapping and summing is applied) back to the property tree.
* '''control:''' Name of the control axis. See above.
* '''prop:''' Property node to receive the value.
* '''side:''' Optional, for split controls. Either "right" or "left"
* '''min/max:''' Clamping applied to output value.

===== control-speed =====
Some controls (most notably flaps and hydraulics) have maximum slew rates and cannot respond instantly to pilot input. This can be implemented with a control-speed tag, which defines a "transition time" required to slew through the full input range. Note that this tag is semi-deprecated, complicated control input filtering can be done much more robustly from a Nasal script.
* '''control:''' Name of the control axis. See above.
* '''transition-time:''' Time in seconds to slew through input range.

===== control-setting =====
This tag is used to define a particular setting for a control axis inside the <cruise> or <approach> tags, where obviously property input is not available. It can be used, for example, to inform the solver that the approach performance values assume full flaps, etc...
* '''axis:''' Name of the control input (i.e. a property name)
* '''value:''' Value of the control axis.

==== Winch and Aerotow ====
===== hitch =====
A hitch, can be used for winch-start (in gliders) or aerotow (in gliders and motor aircraft) or for external cargo with helicopter. You can do aerotow over the net via multiplayer (see j3 and bocian as an example).
* '''name:''' the name of the hitch. must be aerotow if you want to do aerotow via multiplayer. You will find many properties at /sim/hitches/name. Most of them are directly tied to the internal variables, you can modify them as you like. You can add a listener to the property "broken", e. g. for playing a sound.
* '''x,y,z:''' The position of the hitch
* '''force-is-calculated-by-other:''' if you want to simulate aerotowing over the internet, set this value to "1" in the motor aircraft. Don't specify or set this to zero in gliders. In a LAN the time lag might be small enough to set it on both aircraft to "0". It's intended, that this is done automatically in the future.
===== tow =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''length:''' upstretched length in metres
* '''weight-per-meter:''' in kg/metre
* '''elastic-constant:''' lower values give higher elasticity
* '''break-force:''' in N
* '''mp-auto-connect-period:''' the every x seconds a towed multiplayer aircraft is searched. If found, this tow is connected automatically, parameters are copied from the other aircraft. Should be set only in the motor aircraft, not in the glider
===== winch =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''max-tow-length:''' in m
* '''min-tow-length''': in m
* '''initial-tow-length:''' in m. The initial tow length also defines the length/search radius used for the mp-autoconnect feature
* '''max-winch-speed:''' in m/s
* '''power:''' in kW
* '''max-force:''' in N

=== Visualization ===
[[File:Yasim_visualisation_dc6.png|thumb|dc6 fdm in Blender]]To make the programmed aircraft visible it is possible to load and compare it with the 3D model within [[Blender]]. The applaud for this ''very'' usefull script goes to M. Franz, thank you very much!

The script is located in FlightGears source code [http://mapserver.flightgear.org/git/?p=flightgear;a=blob_plain;f=utils/Modeller/yasim_import.py;hb=HEAD utils/Modeller/yasim_import.py].

The howto, taken from inside the script:

yasim_import.py loads and visualizes a YASim FDM geometry
=========================================================

It is recommended to load the model superimposed over a greyed out and immutable copy of the aircraft model:

(0) put this script into ~/.blender/scripts/
(1) load or import aircraft model (menu -> "File" -> "Import" -> "AC3D (.ac) ...")
(2) create new *empty* scene (menu -> arrow button left of "SCE:scene1" combobox -> "ADD NEW" -> "empty")
(3) rename scene to yasim (not required)
(4) link to scene1 (F10 -> "Output" tab -> arrow button left of text entry "No Set Scene" -> "scene1")
(5) now load the YASim config file (menu -> "File" -> "Import" -> "YASim (.xml) ...")

This is good enough for simple checks. But if you are working on the YASim configuration, then you need a
quick and convenient way to reload the file. In that case continue after (4):

(5) switch the button area at the bottom of the blender screen to "Scripts Window" mode (green python snake icon)
(6) load the YASim config file (menu -> "Scripts" -> "Import" -> "YASim (.xml) ...")
(7) make the "Scripts Window" area as small as possible by dragging the area separator down
(8) optionally split the "3D View" area and switch the right part to the "Outliner"
(9) press the "Reload YASim" button in the script area to reload the file

If the 3D model is displaced with respect to the FDM model, then the <offsets> values from the
model animation XML file should be added as comment to the YASim config file, as a line all by
itself, with no spaces surrounding the equal signs. Spaces elsewhere are allowed. For example:

<offsets>
<x-m>3.45</x-m>
<z-m>-0.4</z-m>
<pitch-deg>5</pitch-deg>
</offsets>

becomes:



Possible variables are:

x ... <x-m>
y ... <y-m>
z ... <z-m>
h ... <heading-deg>
p ... <pitch-deg>
r ... <roll-deg>

Of course, absolute FDM coordinates can then no longer directly be read from Blender's 3D view.
The cursor coordinates display in the script area, however, shows the coordinates in YASim space.
Note that object names don't contain XML indices but element numbers. YASim_hstab#2 is the third
hstab in the whole file, not necessarily in its parent XML group. A floating point part in the
object name (e.g. YASim_hstab#2.004) only means that the geometry has been reloaded that often.
It's an unavoidable consequence of how Blender deals with meshes.

Elements are displayed as follows:

cockpit -> monkey head
fuselage -> blue "tube" (with only 12 sides for less clutter); center at "a"
vstab -> red with yellow flaps
wing/mstab/hstab -> green with yellow flaps/spoilers/slats (always 20 cm deep);
symmetric surfaces are only displayed on the left side
thrusters (jet/propeller/thruster) -> dashed line from center to actionpt;
arrow from actionpt along thrust vector (always 1 m long);
propeller circle
rotor -> radius and rel_len_blade_start circle, direction arrow,
normal and forward vector, one blade at phi0
gear -> contact point and compression vector (no arrow head)
tank -> cube (10 cm side length)
weight -> inverted cone
ballast -> cylinder
hitch -> circle (10 cm diameter)
hook -> dashed line for up angle, T-line for down angle
launchbar -> dashed line for up angles, T-line for down angles
A note about step (0) for Windows users: the mentioned path is inside the folder where Blender lives, something like <code>C:\Program Files\Blender Foundation\Blender\.blender\scripts</code>.

=== Command Line ===

By use of a standard command line, we can see what the YASim solver is calculating. First, open up a command line prompt, and enter in the location of YASim.exe, and then the location of the YASim xml file. For example, here's what you would type in for a standard Windows 32-bit installation, and viewing the [[Boeing 777-200ER]]'s YASim file.

<code>"C:\Program Files\FlightGear\bin\Win32\yasim.exe" "C:\Program Files\FlightGear\data\Aircraft\777-200\777-200ER.xml"</code>

The quotes around the paths are required because of the spaces in the path names. Some other options can be used, but they are not needed for normal testing.

The results will give many different values.

* '''Drag Coefficient:''' The drag coefficient of the aircraft.
* '''Lift Ratio:''' The lift ratio of the aircraft.
* '''Cruise AoA:''' The cruise AoA, from conditions at <[[YASim#cruise|cruise]]> in the xml file.
* '''Tail Incidence:''' The incidence angle of the tail, "solved" by YASim as a way to stabilize the aircraft.
* '''Approach Elevator:''' The approach elevator, from conditions at <[[YASim#approach|approach]]> in the xml file.
* '''CG:''' Center of gravity of the aircraft in coordinates. Unless it's supposed to be offset, it should always have a Y value of 0.

=== YASim design notes ===

Andy Ross's original design notes for YASim can be found in [ftp://ftp.uni-duisburg.de/FlightGear/Docs/YASim-simnotes.pdf this PDF file]. These provide some useful background for how YASim works.

=== Additional resources ===
[http://www.buckarooshangar.com/flightgear/ Gary Neely's guide to YASim] is very helpful.

{{FDM}}

[[Category:Flight Dynamics Model]]

[[fr:YASim]]

Talk:YASim

2013-03-26T02:29:47Z

Buckaroo:

With all due respect to Gary Neeley, "Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model." is not an accurate statement of JSBSim's functionality. JSBSim can use any formula the designer wants to use to specify flight, there is no constraint to pre-generate any tabular data at all. While the commonly used Aeromatic model doesn't do much in the way of physically modeling the aircraft, the framework is in place to generate models based on data similar to the data commonly used in YASim, at least aerodynamically.
[[User:Jentron|Jentron]] 21:44, 19 October 2012 (EDT)

Point acknowledged. The quote was from my old YASim guide from some years back when my understanding was weaker than I hope it is now. The quote was used without my knowledge, and though I don't object, I might have suggested that it is not the best appraisal of either YASim or JSBsim. I've taken the liberty of removing the relevant portion of the quoted text from the wiki.

The original statement, while not accurate, was actually meant to promote the flexibility and power of JSBsim rather than imply any limitations or reasons not to use JSBsim. I hope this addresses any possible misunderstanding as to the purpose of my original writing.

-Gary Neely

--[[User:Buckaroo|Buckaroo]] 02:24, 26 March 2013 (UTC)

YASim

2013-03-26T02:27:54Z

Buckaroo:

'''YASim''' is one of two [[flight dynamics model]]s commonly used in [[FlightGear]]. The flight dynamics model (FDM) determines how the [[aircraft]] moves and flies.

Gary Neely wrote in his [http://www.buckarooshangar.com/flightgear/ introduction to YASim]:

:''The FDM is the mathematical model that controls the physics of flight within the simulator. The physical 3D aircraft model has nothing to do with flight dynamics-- in essence it's just a picture to look at. It's the FDM that dictates how the model flies.''

:''Why YASim? YASim uses the geometry of the aircraft to generate the base flight characteristics. While this suggests a 'realistic' or out-of-the-box approach, it is a only rough approximation that will require much tweaking before you get a result that approaches realism. If you have solid flight data for your aircraft such as wind-tunnel data or you are looking to eventually generate a hyper-realistic simulation, JSBSim is probably a better approach. If you lack such data but know the geometry of the aircraft and have access to the same flight characteristics and limits as a real pilot would, then YASim can provide a solution that is more than sufficient for most simulation needs.''

===Coordinate system notes===
All positions specified are in metres (which is weird, since all other units in the file are English). The X axis points forward, Y is left, and Z is up. Take your right hand, and hold it like a gun. Your first and second fingers are the X and Y axes, and your upwards-pointing thumb is the Z. This is slightly different from the coordinate system used by [[JSBSim]]. Sorry. The origin can be placed anywhere, so long as you are consistent. I use the nose of the aircraft.

=== [[XML]] Elements ===
==== airplane ====
The top-level element for the file. It contains only one attribute:
* '''mass:''' The empty (no fuel) weight, in pounds. It does include the weight of the engine(s), so when you add the engine weight in its tag, it acts just like a ballast.

==== approach ====
The approach parameters for the aircraft. The solver will generate an aircraft that matches these settings. The element can (and should) contain <control> elements indicating pilot input settings, such as flaps and throttle, for the approach.
* '''speed:''' The approach airspeed, in knots TAS.
* '''aoa:''' The approach angle of attack, in degrees
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cruise ====
The cruise speed and altitude for the solver to match. As above, this should contain <control> elements indicating aircraft configuration. Especially, make sure the engines are generating enough thrust at cruise!
* '''speed:''' The cruise speed, in knots TAS.
* '''alt:''' The cruise altitude, in feet MSL.
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cockpit ====
The location of the cockpit (pilot eyepoint).
* '''x,y,z:''' eyepoint location (see coordinates note)

==== fuselage ====
This defines a tubelike structure. It will be given an even mass and aerodynamic force distribution by the solver. You can have as many as you like, in any orientation you please.
* '''ax,ay,az:''' One end of the tube (typically the front)
* '''bx,by,bz:''' The other ("back") end.
* '''width:''' The width of the tube, in metres.
* '''taper:''' The approximate radius at the "tips" of the fuselage expressed as a fraction (0-1) of the width value.
* '''midpoint:''' The location of the widest part of the fuselage, expressed as a fraction of the distance between A and B.
* '''idrag:''' Multiplier for the "induced drag" generated by this object. Default is one. With idrag=0 the fuselage generates only drag.
* '''cx,cy,cz:''' Factors for the generated drag in the fuselages "local coordinate system" with x pointing from end to front, z perpendicular to x with y=0 in the aircraft coordinate system. E.g. for a fuselage of a height of 2 times them width you can define cy=2 and (due to the doubled front surface) cx=2.

==== Surfaces ====
===== wing =====
This defines the main wing of the aircraft. You can have only one (but see below about using vstab objects for extra lifting surfaces). The wing should have a <stall> subelement to indicate stall behavior, control surface subelements (flap0, flap1, spoiler, slat) to indicate what and where the control surfaces are, and <control> subelements to map user input properties to the control surfaces.
* '''x,y,z:''' The "base" of the wing, specified as the location of the mid-chord (not leading edge, trailing edge, or aerodynamic center) point at the root of the LEFT (!) wing.
* '''length:''' The length from the base of the wing to the midchord point at the tip. Note that this is not the same thing as span.
* '''chord:''' The chord of the wing at its base, along the X axis (not normal to the leading edge, as it is sometimes defined).
* '''incidence:''' The incidence angle at the wing root, in degrees. Zero is level with the fuselage (as in an aerobatic plane), positive means that the leading edge is higher than the trailing edge (as in a trainer).
* '''twist:''' The difference between the incidence angle at the wing root and the incidence angle at the wing tip. Typically, this is a negative number so that the wing tips have a lower angle of attack and stall after the wing root (washout).
* '''taper:''' The taper fraction, expressed as the tip chord divided by the root chord. A taper of one is a hershey bar wing, and zero would be a wing ending at a point. Defaults to one.
* '''sweep:''' The sweep angle of the wing, in degrees. Zero is no sweep, positive angles are swept back. Defaults to zero.
* '''dihedral:''' The dihedral angle of the wing. Positive angles are upward dihedral. Defaults to zero.
* '''idrag:''' Multiplier for the "induced drag" generated by this surface. In general, low aspect wings will generate less induced drag per-AoA than high aspect (glider) wings. This value isn't constrained well by the solution process, and may require tuning to get throttle settings correct in high AoA (approach) situations.
* '''effectiveness:''' Multiplier for the "normal" drag generated by the wing. Defaults to 1. Arbitrary, dimensionless factor.
* '''camber:''' The lift produced by the wing at zero angle of attack, expressed as a fraction of the maximum lift produced at the stall AoA.

===== hstab =====
These defines the horizontal stabilizer of the aircraft. Internally, it is just a wing object and therefore works the same in XML. You are allowed only one hstab object; the solver needs to know which wing's incidence to play with to get the aircraft trimmed correctly.

===== vstab =====
A "vertical" stabilizer. Like hstab, this is just another wing, with a few special properties. The surface is not "mirrored" as are wing and hstab objects. If you define a left wing only, you'll only get a left wing. The default dihedral, if unspecified, is 90 degrees instead of zero. But all parameters are equally settable, so there's no requirement that this object be "vertical" at all. You can use it for anything you like, such as extra wings for biplanes. Most importantly, these surfaces are not involved with the solver computation, so you can have none, or as many as you like.

===== mstab =====
A mirrored horizontal stabilizer. Exactly the same as wing, but not involved with the solver computation, so you can have none, or as many as you like.

===== stall =====
A subelement of a wing (or hstab/vstab/mstab) that specifies the stall behavior.
* '''aoa:''' The stall angle (maximum lift) in degrees. Note that this is relative to the wing, not the fuselage (since the wing may have a non-zero incidence angle).
* '''width:''' The "width" of the stall, in degrees. A high value indicates a gentle stall. Low values are viscious for a non-twisted wing, but are acceptable for a twisted one (since the whole wing will not stall at the same time).
* '''peak:''' The height of the lift peak, relative to the post-stall secondary lift peak at 45 degrees. Defaults to 1.5. This one is deep voodoo, and probably doesn't need to change much. Bug me for an explanation if you're curious.

===== flap0, flap1, slat, spoiler =====
These are subelements of wing/hstab/vstab objects, and specify the location and effectiveness of the control surfaces.
* '''start:''' The position along the wing where the control surface begins.Zero is the root, one is the tip.
* '''end:''' The position where the surface ends, as above.
* '''lift:''' The lift multiplier for a flap or slat at full extension. One is a no-op, a typical aileron might be 1.2 or so, a giant jetliner flap 2.0, and a spoiler 0.0. For spoilers, the interpretation is a little different -- they spoil only "prestall" lift. Lift due purely to "flat plate" effects isn't affected. For typical wings that stall at low AoA's essentially all lift is pre-stall and you don't have to care. Jet fighters tend not to have wing spoilers, for exactly this reason. This value is not applicable to slats, which affect stall AoA only.
* '''drag:''' The drag multiplier, as above. Typically should be higher than the lift multiplier for flaps.
* '''aoa:''' Applicable only to slats. This indicates the angle by which the stall AoA is translated by the slat extension.

==== Engine ====
===== Thruster =====
A very simple "thrust only" engine object. Useful for things like thrust vectoring nozzles. All it does is map its THROTTLE input axis to its output thrust rating. Does not consume fuel, etc...
* '''thrust:''' Maximum thrust in pounds
* '''x,y,z:''' The point on the airframe where thrust will be applied.
* '''vx,vy,vy:''' The direction of the thrust in airframe coordinates. The vector will be normalized automatically, so any non-zero vector will work fine.

===== Jet =====
A turbojet/fan engine. It accepts a <control> subelement to map a property to its throttle setting, and an <actionpt> subelement to place the action point of the thrust at a different position than the mass of the engine.
* '''x,y,z:''' The location of the engine, as a point mass. If no actionpt is specified, this will also be the point of application of thrust.
* '''mass:''' The mass of the engine, in pounds.
* '''thrust:''' The maximum sea-level thrust, in pounds.
* '''afterburner:''' Maximum total thrust with afterburner/reheat, in pounds [defaults to "no additional thrust"].
* '''rotate:''' Vector angle of the thrust in degrees about the Y axis [0].
* '''n1-idle:''' Idling low pressure core / fan speed [55].
* '''n1-max:''' Maximum low pressure core / fan speed [102].
* '''n2-idle:''' Idling high pressure core speed [73].
* '''n2-max:''' Maximum high pressure core speed [103].
* '''tsfc:''' Thrust-specific fuel consumption [0.8]. This should be considerably lower for modern turbofans.
* '''egt:''' Exhaust gas temperature at takeoff in K [1050].
* '''epr:''' Engine pressure ratio at takeoff [3.0].
* '''exhaust-speed:''' The maximum exhaust speed in knots [~1555].
* '''spool-time:''' Time, in seconds, for the engine to respond to 90% of a commanded powersetting.

===== Propeller =====
A propeller. This element requires an engine subtag. Currently <piston-engine> and <turbine-engine> are supported.
* '''x,y,z:''' The position of the mass (!) of the engine/propeller combination. If the point of force application is different (and it will be) it should be set with an <actionpt> subelement.
* '''mass:''' The mass of the engine/propeller, in pounds.
* '''moment:''' The moment, in kg-metres^2. This has to be hand calculated and guessed at for now. A more automated system will be forthcoming. Use a negative moment value for counter-rotating ("European" -- CCW as seen from behind the prop) propellers. A good guess for this value is the radius of the prop (in metres) squared times the mass (kg) divided by three; that is the moment of a plain "stick" bolted to the prop shaft.
* '''radius:''' The radius, in metres, or the propeller.
* '''cruise-speed:''' The max efficiency cruise speed of the propeller. Generally not the same as the aircraft's cruise speed.
* '''cruise-rpm:''' The RPM of the propeller at max-eff. cruise.
* '''cruise-power:''' The power sunk by the prop at cruise, in horsepower.
* '''cruise-alt:''' The reference cruise altitude in feet.
* '''takeoff-power:''' The takeoff power required by the propeller...
* '''takeoff-rpm:''' ...at the given takeoff RPM.
* '''min-rpm:''' The minimum operational RPM for a constant speed propeller. This is the speed to which the prop governor will seek when the blue lever is at minimum. The coarse-stop attribute limits how far the governor can go into trying to reach this RPM.
* '''max-rpm:''' The maximum operational RPM for a constant speed propeller. See above. The fine-stop attribute limits how far the governor can go in trying to reach this RPM.
* '''fine-stop:''' The minimum pitch of the propeller (high RPM) as a ratio of ideal cruise pitch. This is set to 0.25 by default -- a higher value will result in a lower RPM at low power settings (e.g. idle, taxi, and approach).
* '''coarse-stop:''' The maximum pitch of the propeller (low RPM) as a ratio of ideal cruise pitch. This is set to 4.0 by default -- a lower value may result in a higher RPM at high power settings.
* '''gear-ratio:''' The factor by which the engine RPM is multiplied to produce the propeller RPM. Optional (defaults to 1.0).
* '''contra:''' When set (contra="1"), this indicates that the propeller is a contra-rotating pair. It will not contribute to the aircraft's net gyroscopic moment, nor will it produce asymmetric torque on the aircraft body. Asymmetric slipstream effects, when implemented, will also be zero when this is set.
* '''piston-engine:''' A piston engine definition. This must be a subelement of an enclosing <propeller> tag.
* '''eng-power:''' Maximum BHP of the engine at sea level.
* '''eng-rpm:''' The engine RPM at which eng-power is developed
* '''displacement:''' The engine displacement in cubic inches.
* '''compression:''' The engine compression ratio.

==== Landing gear ====
===== gear =====
Defines a landing gear. Accepts <control> subelements to map properties to steering and braking. Can also be used to simulate floats. Although the coefficients are still called ..fric, it is calculated in fluids as a drag (proportional to the square of the speed). In fluids gears are not considered to detect crashes (as on ground).
* '''x,y,z:''' The location of the fully-extended gear tip.
* '''compression:''' The distance in metres along the "up" axis that the gear will compress.
* '''initial-load:''' The initial load of the spring in multiples of compression. Defaults to 0. (With this parameter a lower spring-constants will be used for the gear-> can reduce numerical problems (jitter)) '''Note:''' the spring-constant is varied from 0% compression to 20% compression to get continuous behavior around 0 compression. (could be physically explained by wheel deformation)
* '''upx/upy/upz:''' The direction of compression, defaults to vertical (0,0,1) if unspecified. These are used only for a direction -- the vector need not be normalized, as the length is specified by "compression".
* '''sfric:''' Static (non-skidding) coefficient of friction. Defaults to 0.8.
* '''dfric:''' Dynamic friction. Defaults to 0.7.
* '''spring:''' A dimensionless multiplier for the automatically generated spring constant. Increase to make the gear stiffer, decrease to make it squishier.
* '''damp:''' A dimensionless multiplier for the automatically generated damping coefficient. Decrease to make the gear "bouncier", increase to make it "slower". Beware of increasing this too far: very high damping forces can make the numerics unstable. If you can't make the gear stop bouncing with this number, try increasing the compression length instead.
* '''on-water:''' if this is set to "0" the gear will be ignored if on water. Defaults to "0"
* '''on-solid:''' if this set to "0" the gear will be ignored if not on water. Defaults to "1"
* '''speed-planing:'''
* '''spring-factor-not-planing:''' At zero speed the spring factor is multiplied by spring-factor-not-planing. Above speed-planing this factor is equal to 1. The idea is, to use this for floats simulating the transition from swimming to planing. speed-planing defaults to 0, spring-factor-not-planing defaults to 1.
* '''reduce-friction-by-extension:''' at full extension the friction is reduced by this relative value. 0.7 means 30% friction at full extension. If you specify a value greater than one, the friction will be zero before reaching full extension. Defaults to "0"
* '''ignored-by-solver:''' with the on-water/on-solid tags you can have more than one set of gears in one aircraft, If the solver (who automatically generates the spring constants) would take all gears into account, the result would be wrong. E. G. set this tag to "1" for all gears, which are not active on runways. Defaults to "0". You can not exclude all gears in the solving process.

===== Launchbar =====
Defines a catapult launchbar or strop.
* '''x,y,z:''' The location of the mount point of the launch bar or strop on the aircraft.
* '''length:''' The length of the launch bar from mount point to tip
* '''down-angle:''' The max angle below the horizontal the launchbar can achieve.
* '''up-angle:''' The max angle above the horizontal the launchbar can achieve.
* '''holdback-{x,y,z}:''' The location of the holdback mount point on the aircraft.
* '''holdback-length:''' The length of the holdback from mount point to tip. Note: holdback up-angle and down-angle are the same as those defined for the launchbar and are not specified in the configuration.

==== Fuel ====
===== tank =====
A fuel tank. Tanks in the aircraft are identified numerically (starting from zero), in the order they are defined in the file. If the left tank is first, "tank[0]" will be the left tank.
* '''x,y,z:''' The location of the tank.
* '''capacity:''' The maximum contents of the tank, in pounds. Not gallons -- YASim supports fuels of varying densities.
* '''jet:''' A boolean. If present, this causes the fuel density to be treated as Jet-A. Otherwise, gasoline density is used. A more elaborate density setting (in pounds per gallon, for example) would be easy to implement. Bug me.

==== Center of Gravity ====

===== Ballast =====
This is a mechanism for modifying the mass distribution of the aircraft. A ballast setting specifies that a particular amount of the empty weight of the aircraft must be placed at a given location. The remaining non-ballast weight will be distributed "intelligently" across the fuselage and wing objects. Note again: this does NOT change the empty weight of the aircraft.
* '''x,y,z:''' The location of the ballast.
* '''mass:''' How much mass, in pounds, to put there. Note that this value can be negative. I find that I often need to "lighten" the tail of the aircraft.

===== Weight =====
This is an added weight, something not part of the empty weight of the aircraft, like passengers, cargo, or external stores. The actual value of the mass is not specified here, instead, a mapping to a property is used. This allows external code, such as the panel, to control the weight (loading a given cargo configuration from preference files, dropping bombs at runtime, etc...)
* '''x,y,z:''' The location of the weight.
* '''mass-prop:''' The name of the fgfs property containing the mass, in pounds, of this weight.
* '''size:''' The aerodynamic "size", in metres, of the object. This is important for external stores, which will cause drag. For reasonably aerodynamic stuff like bombs, the size should be roughly the width of the object. For other stuff, you're on your own. The default is zero, which results in no aerodynamic force (internal cargo).
* '''solve-weight:''' Subtag of approach and cruise parameters. Used to specify a non-zero setting for a <weight> tag during solution. The default is to assume all weights are zero at the given performance numbers.
* '''idx:''' Index of the weight in the file (starting with zero).
* '''weight:''' Weight setting in pounds.

==== Controls ====
===== control-input =====
This element manages a mapping from fgfs properties (user input) to settable values on the aircraft's objects. Note that the value to be set MUST (!) be valid on the given object type. This is not checked for by the parser, and will cause a runtime crash if you try it. Wing's don't have throttle controls, etc... Note that multiple axes may be set on the same value. They are summed before setting.
* '''axis:''' The name of the double-valued fgfs property "axis" to use as input, such as "/controls/flight/aileron".
* '''control:''' Which control axis to set on the objects. It can have the following values:
** THROTTLE - The throttle on a jet or propeller.
** MIXTURE - The mixture on a propeller.
** REHEAT - The afterburner on a jet
** PROP - The propeller advance
** BRAKE - The brake on a gear.
** STEER - The steering angle on a gear.
** INCIDENCE - The incidence angle of a wing.
** FLAP0 - The flap0 deflection of a wing.
** FLAP1 - The flap1 deflection of a wing.
** SLAT - The slat extension of a wing.
** SPOILER - The spoiler extension for a wing.
** CYCLICAIL - The "aileron" cyclic input of a rotor
** CYCLICELE - The "elevator" cyclic input of a rotor
** COLLECTIVE - The collective input of a rotor
** ROTORENGINEON - If not equal zero the rotor is rotating
** WINCHRELSPEED - The relative winch speed
** {... and many more, see FGFDM.cpp ...}
* '''invert:''' Negate the value of the property before setting on the object.
* '''split:''' Applicable to wing control surfaces. Sets the normal value on the left wing, and a negated value on the right wing.
* '''square:''' Squares the value before setting. Useful for controls like steering that need a wide range, yet lots of sensitivity in the center. Obviously only applicable to values that have a range of [-1:1] or [0:1].
* '''src0/src1/dst0/dst1:''' If present, these defined a linear mapping from the source to the output value. Input values in the range src0-src1 are mapped linearly to dst0-dst1, with clamping for input values that lie outside the range.

===== control-output =====
This can be used to pass the value of a YASim control axis (after all mapping and summing is applied) back to the property tree.
* '''control:''' Name of the control axis. See above.
* '''prop:''' Property node to receive the value.
* '''side:''' Optional, for split controls. Either "right" or "left"
* '''min/max:''' Clamping applied to output value.

===== control-speed =====
Some controls (most notably flaps and hydraulics) have maximum slew rates and cannot respond instantly to pilot input. This can be implemented with a control-speed tag, which defines a "transition time" required to slew through the full input range. Note that this tag is semi-deprecated, complicated control input filtering can be done much more robustly from a Nasal script.
* '''control:''' Name of the control axis. See above.
* '''transition-time:''' Time in seconds to slew through input range.

===== control-setting =====
This tag is used to define a particular setting for a control axis inside the <cruise> or <approach> tags, where obviously property input is not available. It can be used, for example, to inform the solver that the approach performance values assume full flaps, etc...
* '''axis:''' Name of the control input (i.e. a property name)
* '''value:''' Value of the control axis.

==== Winch and Aerotow ====
===== hitch =====
A hitch, can be used for winch-start (in gliders) or aerotow (in gliders and motor aircraft) or for external cargo with helicopter. You can do aerotow over the net via multiplayer (see j3 and bocian as an example).
* '''name:''' the name of the hitch. must be aerotow if you want to do aerotow via multiplayer. You will find many properties at /sim/hitches/name. Most of them are directly tied to the internal variables, you can modify them as you like. You can add a listener to the property "broken", e. g. for playing a sound.
* '''x,y,z:''' The position of the hitch
* '''force-is-calculated-by-other:''' if you want to simulate aerotowing over the internet, set this value to "1" in the motor aircraft. Don't specify or set this to zero in gliders. In a LAN the time lag might be small enough to set it on both aircraft to "0". It's intended, that this is done automatically in the future.
===== tow =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''length:''' upstretched length in metres
* '''weight-per-meter:''' in kg/metre
* '''elastic-constant:''' lower values give higher elasticity
* '''break-force:''' in N
* '''mp-auto-connect-period:''' the every x seconds a towed multiplayer aircraft is searched. If found, this tow is connected automatically, parameters are copied from the other aircraft. Should be set only in the motor aircraft, not in the glider
===== winch =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''max-tow-length:''' in m
* '''min-tow-length''': in m
* '''initial-tow-length:''' in m. The initial tow length also defines the length/search radius used for the mp-autoconnect feature
* '''max-winch-speed:''' in m/s
* '''power:''' in kW
* '''max-force:''' in N

=== Visualization ===
[[File:Yasim_visualisation_dc6.png|thumb|dc6 fdm in Blender]]To make the programmed aircraft visible it is possible to load and compare it with the 3D model within [[Blender]]. The applaud for this ''very'' usefull script goes to M. Franz, thank you very much!

The script is located in FlightGears source code [http://mapserver.flightgear.org/git/?p=flightgear;a=blob_plain;f=utils/Modeller/yasim_import.py;hb=HEAD utils/Modeller/yasim_import.py].

The howto, taken from inside the script:

yasim_import.py loads and visualizes a YASim FDM geometry
=========================================================

It is recommended to load the model superimposed over a greyed out and immutable copy of the aircraft model:

(0) put this script into ~/.blender/scripts/
(1) load or import aircraft model (menu -> "File" -> "Import" -> "AC3D (.ac) ...")
(2) create new *empty* scene (menu -> arrow button left of "SCE:scene1" combobox -> "ADD NEW" -> "empty")
(3) rename scene to yasim (not required)
(4) link to scene1 (F10 -> "Output" tab -> arrow button left of text entry "No Set Scene" -> "scene1")
(5) now load the YASim config file (menu -> "File" -> "Import" -> "YASim (.xml) ...")

This is good enough for simple checks. But if you are working on the YASim configuration, then you need a
quick and convenient way to reload the file. In that case continue after (4):

(5) switch the button area at the bottom of the blender screen to "Scripts Window" mode (green python snake icon)
(6) load the YASim config file (menu -> "Scripts" -> "Import" -> "YASim (.xml) ...")
(7) make the "Scripts Window" area as small as possible by dragging the area separator down
(8) optionally split the "3D View" area and switch the right part to the "Outliner"
(9) press the "Reload YASim" button in the script area to reload the file

If the 3D model is displaced with respect to the FDM model, then the <offsets> values from the
model animation XML file should be added as comment to the YASim config file, as a line all by
itself, with no spaces surrounding the equal signs. Spaces elsewhere are allowed. For example:

<offsets>
<x-m>3.45</x-m>
<z-m>-0.4</z-m>
<pitch-deg>5</pitch-deg>
</offsets>

becomes:



Possible variables are:

x ... <x-m>
y ... <y-m>
z ... <z-m>
h ... <heading-deg>
p ... <pitch-deg>
r ... <roll-deg>

Of course, absolute FDM coordinates can then no longer directly be read from Blender's 3D view.
The cursor coordinates display in the script area, however, shows the coordinates in YASim space.
Note that object names don't contain XML indices but element numbers. YASim_hstab#2 is the third
hstab in the whole file, not necessarily in its parent XML group. A floating point part in the
object name (e.g. YASim_hstab#2.004) only means that the geometry has been reloaded that often.
It's an unavoidable consequence of how Blender deals with meshes.

Elements are displayed as follows:

cockpit -> monkey head
fuselage -> blue "tube" (with only 12 sides for less clutter); center at "a"
vstab -> red with yellow flaps
wing/mstab/hstab -> green with yellow flaps/spoilers/slats (always 20 cm deep);
symmetric surfaces are only displayed on the left side
thrusters (jet/propeller/thruster) -> dashed line from center to actionpt;
arrow from actionpt along thrust vector (always 1 m long);
propeller circle
rotor -> radius and rel_len_blade_start circle, direction arrow,
normal and forward vector, one blade at phi0
gear -> contact point and compression vector (no arrow head)
tank -> cube (10 cm side length)
weight -> inverted cone
ballast -> cylinder
hitch -> circle (10 cm diameter)
hook -> dashed line for up angle, T-line for down angle
launchbar -> dashed line for up angles, T-line for down angles
A note about step (0) for M$ users: the mentioned path is inside the folder where Blender lives, something like <code>C:\Program Files\Blender Foundation\Blender\.blender\scripts</code>.

=== Command Line ===

By use of a standard command line, we can see what the YASim solver is calculating. First, open up a command line prompt, and enter in the location of YASim.exe, and then the location of the YASim xml file. For example, here's what you would type in for a standard Windows 32-bit installation, and viewing the [[Boeing 777-200ER]]'s YASim file.

<code>"C:\Program Files\FlightGear\bin\Win32\yasim.exe" "C:\Program Files\FlightGear\data\Aircraft\777-200\777-200ER.xml"</code>

The quotes around the paths are required because of the spaces in the path names. Some other options can be used, but they are not needed for normal testing.

The results will give many different values.

* '''Drag Coefficient:''' The drag coefficient of the aircraft.
* '''Lift Ratio:''' The lift ratio of the aircraft.
* '''Cruise AoA:''' The cruise AoA, from conditions at <[[YASim#cruise|cruise]]> in the xml file.
* '''Tail Incidence:''' The incidence angle of the tail, "solved" by YASim as a way to stabilize the aircraft.
* '''Approach Elevator:''' The approach elevator, from conditions at <[[YASim#approach|approach]]> in the xml file.
* '''CG:''' Center of gravity of the aircraft in coordinates. Unless it's supposed to be offset, it should always have a Y value of 0.

=== YASim design notes ===

Andy Ross's original design notes for YASim can be found in [ftp://ftp.uni-duisburg.de/FlightGear/Docs/YASim-simnotes.pdf this PDF file]. These provide some useful background for how YASim works.

=== Additional resources ===
[http://www.buckarooshangar.com/flightgear/ Gary Neely's guide to YASim] is very helpful.

{{FDM}}

[[Category:Flight Dynamics Model]]

[[fr:YASim]]

Talk:YASim

2013-03-26T02:26:04Z

Buckaroo:

With all due respect to Gary Neeley, "Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model." is not an accurate statement of JSBSim's functionality. JSBSim can use any formula the designer wants to use to specify flight, there is no constraint to pre-generate any tabular data at all. While the commonly used Aeromatic model doesn't do much in the way of physically modeling the aircraft, the framework is in place to generate models based on data similar to the data commonly used in YASim, at least aerodynamically.
[[User:Jentron|Jentron]] 21:44, 19 October 2012 (EDT)

Point acknowledged. The quote was from my old YASim guide from some years back when my understanding was weaker than I hope it is now. The quote was used without my knowledge, and though I don't object, I might have suggested that it is not the best appraisal of either YASim or JSBsim.

The original statement, while not accurate, was actually meant to promote the flexibility and power of JSBsim rather than imply any limitations or reasons not to use JSBsim. I hope this addresses any possible misunderstanding as to the purpose of my original writing.

-Gary Neely

--[[User:Buckaroo|Buckaroo]] 02:24, 26 March 2013 (UTC)

Talk:YASim

2013-03-26T02:25:13Z

Buckaroo: /* YASim */

With all due respect to Gary Neeley, "Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model." is not an accurate statement of JSBSim's functionality. JSBSim can use any formula the designer wants to use to specify flight, there is no constraint to pre-generate any tabular data at all. While the commonly used Aeromatic model doesn't do much in the way of physically modeling the aircraft, the framework is in place to generate models based on data similar to the data commonly used in YASim, at least aerodynamically.
[[User:Jentron|Jentron]] 21:44, 19 October 2012 (EDT)

Point acknowledged. The quote was from my old YASim guide from some years back when my understanding was weaker than I hope it is now. The quote was used without my knowledge, and though I don't object, I might have suggested that it is not the best appraisal of either YASim or JSBsim.

The original statement, while not accurate, was actually meant to promote the flexibility and power of JSBsim rather than imply any limitations or reasons not to use JSBsim. I hope this addresses any possible misunderstanding as to the purpose of my original writing.

-Gary "Buckaroo" Neely

--[[User:Buckaroo|Buckaroo]] 02:24, 26 March 2013 (UTC)

Talk:YASim

2013-03-26T02:24:46Z

Buckaroo: /* YASim */

With all due respect to Gary Neeley, "Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model." is not an accurate statement of JSBSim's functionality. JSBSim can use any formula the designer wants to use to specify flight, there is no constraint to pre-generate any tabular data at all. While the commonly used Aeromatic model doesn't do much in the way of physically modeling the aircraft, the framework is in place to generate models based on data similar to the data commonly used in YASim, at least aerodynamically.
[[User:Jentron|Jentron]] 21:44, 19 October 2012 (EDT)

== YASim ==

Point acknowledged. The quote was from my old YASim guide from some years back when my understanding was weaker than I hope it is now. The quote was used without my knowledge, and though I don't object, I might have suggested that it is not the best appraisal of either YASim or JSBsim.

The original statement, while not accurate, was actually meant to promote the flexibility and power of JSBsim rather than imply any limitations or reasons not to use JSBsim. I hope this addresses any possible misunderstanding as to the purpose of my original writing.

-Gary "Buckaroo" Neely

--[[User:Buckaroo|Buckaroo]] 02:24, 26 March 2013 (UTC)

Talk:YASim

2013-03-26T02:08:12Z

Buckaroo: /* YASim */ new section

YASim

2012-07-19T05:30:59Z

Buckaroo: URL fix

'''YASim''' is one of three [[flight dynamics model]]s commonly used by [[FlightGear]].

The flight dynamics model (FDM) determines how the [[aircraft]] moves and flies.

Gary Neely wrote in his [http://www.buckarooshangar.com/flightgear/ introduction to YASim]:

:''The FDM is the mathematical model that controls the physics of flight within the simulator. The physical 3D aircraft model has nothing to do with flight dynamics-- in essence it's just a picture to look at. It's the FDM that dictates how the model flies.''

:''Why YASim? YASim uses the geometry of the aircraft to generate the base flight characteristics. While this suggests a 'realistic' or out-of-the-box approach, it is a only rough approximation that will require much tweaking before you get a result that approaches realism. Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model. If you have solid flight data for your aircraft such as wind-tunnel data or you are looking to eventually generate a hyper-realistic simulation, JSBSim is probably a better approach. If you lack such data but know the geometry of the aircraft and have access to the same flight characteristics and limits as a real pilot would, then YASim can provide a solution that is more than sufficient for most simulation needs.''

===Coordinate system notes===
All positions specified are in metres (which is weird, since all other units in the file are English). The X axis points forward, Y is left, and Z is up. Take your right hand, and hold it like a gun. Your first and second fingers are the X and Y axes, and your upwards-pointing thumb is the Z. This is slightly different from the coordinate system used by [[JSBSim]]. Sorry. The origin can be placed anywhere, so long as you are consistent. I use the nose of the aircraft.

=== [[XML]] Elements ===
==== airplane ====
The top-level element for the file. It contains only one attribute:
* '''mass:''' The empty (no fuel) weight, in pounds. It does include the weight of the engine(s), so when you add the engine weight in its tag, it acts just like a ballast.

==== approach ====
The approach parameters for the aircraft. The solver will generate an aircraft that matches these settings. The element can (and should) contain <control> elements indicating pilot input settings, such as flaps and throttle, for the approach.
* '''speed:''' The approach airspeed, in knots TAS.
* '''aoa:''' The approach angle of attack, in degrees
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cruise ====
The cruise speed and altitude for the solver to match. As above, this should contain <control> elements indicating aircraft configuration. Especially, make sure the engines are generating enough thrust at cruise!
* '''speed:''' The cruise speed, in knots TAS.
* '''alt:''' The cruise altitude, in feet MSL.
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cockpit ====
The location of the cockpit (pilot eyepoint).
* '''x,y,z:''' eyepoint location (see coordinates note)

==== fuselage ====
This defines a tubelike structure. It will be given an even mass and aerodynamic force distribution by the solver. You can have as many as you like, in any orientation you please.
* '''ax,ay,az:''' One end of the tube (typically the front)
* '''bx,by,bz:''' The other ("back") end.
* '''width:''' The width of the tube, in metres.
* '''taper:''' The approximate radius at the "tips" of the fuselage expressed as a fraction (0-1) of the width value.
* '''midpoint:''' The location of the widest part of the fuselage, expressed as a fraction of the distance between A and B.
* '''idrag:''' Multiplier for the "induced drag" generated by this object. Default is one. With idrag=0 the fuselage generates only drag.
* '''cx,cy,cz:''' Factors for the generated drag in the fuselages "local coordinate system" with x pointing from end to front, z perpendicular to x with y=0 in the aircraft coordinate system. E.g. for a fuselage of a height of 2 times them width you can define cy=2 and (due to the doubled front surface) cx=2.

==== Surfaces ====
===== wing =====
This defines the main wing of the aircraft. You can have only one (but see below about using vstab objects for extra lifting surfaces). The wing should have a <stall> subelement to indicate stall behavior, control surface subelements (flap0, flap1, spoiler, slat) to indicate what and where the control surfaces are, and <control> subelements to map user input properties to the control surfaces.
* '''x,y,z:''' The "base" of the wing, specified as the location of the mid-chord (not leading edge, trailing edge, or aerodynamic center) point at the root of the LEFT (!) wing.
* '''length:''' The length from the base of the wing to the midchord point at the tip. Note that this is not the same thing as span.
* '''chord:''' The chord of the wing at its base, along the X axis (not normal to the leading edge, as it is sometimes defined).
* '''incidence:''' The incidence angle at the wing root, in degrees. Zero is level with the fuselage (as in an aerobatic plane), positive means that the leading edge is higher than the trailing edge (as in a trainer).
* '''twist:''' The difference between the incidence angle at the wing root and the incidence angle at the wing tip. Typically, this is a negative number so that the wing tips have a lower angle of attack and stall after the wing root (washout).
* '''taper:''' The taper fraction, expressed as the tip chord divided by the root chord. A taper of one is a hershey bar wing, and zero would be a wing ending at a point. Defaults to one.
* '''sweep:''' The sweep angle of the wing, in degrees. Zero is no sweep, positive angles are swept back. Defaults to zero.
* '''dihedral:''' The dihedral angle of the wing. Positive angles are upward dihedral. Defaults to zero.
* '''idrag:''' Multiplier for the "induced drag" generated by this surface. In general, low aspect wings will generate less induced drag per-AoA than high aspect (glider) wings. This value isn't constrained well by the solution process, and may require tuning to get throttle settings correct in high AoA (approach) situations.
* '''effectiveness:''' Multiplier for the "normal" drag generated by the wing. Defaults to 1. Arbitrary, dimensionless factor.
* '''camber:''' The lift produced by the wing at zero angle of attack, expressed as a fraction of the maximum lift produced at the stall AoA.

===== hstab =====
These defines the horizontal stabilizer of the aircraft. Internally, it is just a wing object and therefore works the same in XML. You are allowed only one hstab object; the solver needs to know which wing's incidence to play with to get the aircraft trimmed correctly.

===== vstab =====
A "vertical" stabilizer. Like hstab, this is just another wing, with a few special properties. The surface is not "mirrored" as are wing and hstab objects. If you define a left wing only, you'll only get a left wing. The default dihedral, if unspecified, is 90 degrees instead of zero. But all parameters are equally settable, so there's no requirement that this object be "vertical" at all. You can use it for anything you like, such as extra wings for biplanes. Most importantly, these surfaces are not involved with the solver computation, so you can have none, or as many as you like.

===== mstab =====
A mirrored horizontal stabilizer. Exactly the same as wing, but not involved with the solver computation, so you can have none, or as many as you like.

===== stall =====
A subelement of a wing (or hstab/vstab/mstab) that specifies the stall behavior.
* '''aoa:''' The stall angle (maximum lift) in degrees. Note that this is relative to the wing, not the fuselage (since the wing may have a non-zero incidence angle).
* '''width:''' The "width" of the stall, in degrees. A high value indicates a gentle stall. Low values are viscious for a non-twisted wing, but are acceptable for a twisted one (since the whole wing will not stall at the same time).
* '''peak:''' The height of the lift peak, relative to the post-stall secondary lift peak at 45 degrees. Defaults to 1.5. This one is deep voodoo, and probably doesn't need to change much. Bug me for an explanation if you're curious.

===== flap0, flap1, slat, spoiler =====
These are subelements of wing/hstab/vstab objects, and specify the location and effectiveness of the control surfaces.
* '''start:''' The position along the wing where the control surface begins.Zero is the root, one is the tip.
* '''end:''' The position where the surface ends, as above.
* '''lift:''' The lift multiplier for a flap or slat at full extension. One is a no-op, a typical aileron might be 1.2 or so, a giant jetliner flap 2.0, and a spoiler 0.0. For spoilers, the interpretation is a little different -- they spoil only "prestall" lift. Lift due purely to "flat plate" effects isn't affected. For typical wings that stall at low AoA's essentially all lift is pre-stall and you don't have to care. Jet fighters tend not to have wing spoilers, for exactly this reason. This value is not applicable to slats, which affect stall AoA only.
* '''drag:''' The drag multiplier, as above. Typically should be higher than the lift multiplier for flaps.
* '''aoa:''' Applicable only to slats. This indicates the angle by which the stall AoA is translated by the slat extension.

==== Engine ====
===== Thruster =====
A very simple "thrust only" engine object. Useful for things like thrust vectoring nozzles. All it does is map its THROTTLE input axis to its output thrust rating. Does not consume fuel, etc...
* '''thrust:''' Maximum thrust in pounds
* '''x,y,z:''' The point on the airframe where thrust will be applied.
* '''vx,vy,vy:''' The direction of the thrust in airframe coordinates. The vector will be normalized automatically, so any non-zero vector will work fine.

===== Jet =====
A turbojet/fan engine. It accepts a <control> subelement to map a property to its throttle setting, and an <actionpt> subelement to place the action point of the thrust at a different position than the mass of the engine.
* '''x,y,z:''' The location of the engine, as a point mass. If no actionpt is specified, this will also be the point of application of thrust.
* '''mass:''' The mass of the engine, in pounds.
* '''thrust:''' The maximum sea-level thrust, in pounds.
* '''afterburner:''' Maximum total thrust with afterburner/reheat, in pounds [defaults to "no additional thrust"].
* '''rotate:''' Vector angle of the thrust in degrees about the Y axis [0].
* '''n1-idle:''' Idling low pressure core / fan speed [55].
* '''n1-max:''' Maximum low pressure core / fan speed [102].
* '''n2-idle:''' Idling high pressure core speed [73].
* '''n2-max:''' Maximum high pressure core speed [103].
* '''tsfc:''' Thrust-specific fuel consumption [0.8]. This should be considerably lower for modern turbofans.
* '''egt:''' Exhaust gas temperature at takeoff in K [1050].
* '''epr:''' Engine pressure ratio at takeoff [3.0].
* '''exhaust-speed:''' The maximum exhaust speed in knots [~1555].
* '''spool-time:''' Time, in seconds, for the engine to respond to 90% of a commanded powersetting.

===== Propeller =====
A propeller. This element requires an engine subtag. Currently <piston-engine> and <turbine-engine> are supported.
* '''x,y,z:''' The position of the mass (!) of the engine/propeller combination. If the point of force application is different (and it will be) it should be set with an <actionpt> subelement.
* '''mass:''' The mass of the engine/propeller, in pounds.
* '''moment:''' The moment, in kg-metres^2. This has to be hand calculated and guessed at for now. A more automated system will be forthcoming. Use a negative moment value for counter-rotating ("European" -- CCW as seen from behind the prop) propellers. A good guess for this value is the radius of the prop (in metres) squared times the mass (kg) divided by three; that is the moment of a plain "stick" bolted to the prop shaft.
* '''radius:''' The radius, in metres, or the propeller.
* '''cruise-speed:''' The max efficiency cruise speed of the propeller. Generally not the same as the aircraft's cruise speed.
* '''cruise-rpm:''' The RPM of the propeller at max-eff. cruise.
* '''cruise-power:''' The power sunk by the prop at cruise, in horsepower.
* '''cruise-alt:''' The reference cruise altitude in feet.
* '''takeoff-power:''' The takeoff power required by the propeller...
* '''takeoff-rpm:''' ...at the given takeoff RPM.
* '''min-rpm:''' The minimum operational RPM for a constant speed propeller. This is the speed to which the prop governor will seek when the blue lever is at minimum. The coarse-stop attribute limits how far the governor can go into trying to reach this RPM.
* '''max-rpm:''' The maximum operational RPM for a constant speed propeller. See above. The fine-stop attribute limits how far the governor can go in trying to reach this RPM.
* '''fine-stop:''' The minimum pitch of the propeller (high RPM) as a ratio of ideal cruise pitch. This is set to 0.25 by default -- a higher value will result in a lower RPM at low power settings (e.g. idle, taxi, and approach).
* '''coarse-stop:''' The maximum pitch of the propeller (low RPM) as a ratio of ideal cruise pitch. This is set to 4.0 by default -- a lower value may result in a higher RPM at high power settings.
* '''gear-ratio:''' The factor by which the engine RPM is multiplied to produce the propeller RPM. Optional (defaults to 1.0).
* '''contra:''' When set (contra="1"), this indicates that the propeller is a contra-rotating pair. It will not contribute to the aircraft's net gyroscopic moment, nor will it produce asymmetric torque on the aircraft body. Asymmetric slipstream effects, when implemented, will also be zero when this is set.
* '''piston-engine:''' A piston engine definition. This must be a subelement of an enclosing <propeller> tag.
* '''eng-power:''' Maximum BHP of the engine at sea level.
* '''eng-rpm:''' The engine RPM at which eng-power is developed
* '''displacement:''' The engine displacement in cubic inches.
* '''compression:''' The engine compression ratio.

==== Landing gear ====
===== gear =====
Defines a landing gear. Accepts <control> subelements to map properties to steering and braking. Can also be used to simulate floats. Although the coefficients are still called ..fric, it is calculated in fluids as a drag (proportional to the square of the speed). In fluids gears are not considered to detect crashes (as on ground).
* '''x,y,z:''' The location of the fully-extended gear tip.
* '''compression:''' The distance in metres along the "up" axis that the gear will compress.
* '''initial-load:''' The initial load of the spring in multiples of compression. Defaults to 0. (With this parameter a lower spring-constants will be used for the gear-> can reduce numerical problems (jitter)) '''Note:''' the spring-constant is varied from 0% compression to 20% compression to get continuous behavior around 0 compression. (could be physically explained by wheel deformation)
* '''upx/upy/upz:''' The direction of compression, defaults to vertical (0,0,1) if unspecified. These are used only for a direction -- the vector need not be normalized, as the length is specified by "compression".
* '''sfric:''' Static (non-skidding) coefficient of friction. Defaults to 0.8.
* '''dfric:''' Dynamic friction. Defaults to 0.7.
* '''spring:''' A dimensionless multiplier for the automatically generated spring constant. Increase to make the gear stiffer, decrease to make it squishier.
* '''damp:''' A dimensionless multiplier for the automatically generated damping coefficient. Decrease to make the gear "bouncier", increase to make it "slower". Beware of increasing this too far: very high damping forces can make the numerics unstable. If you can't make the gear stop bouncing with this number, try increasing the compression length instead.
* '''on-water:''' if this is set to "0" the gear will be ignored if on water. Defaults to "0"
* '''on-solid:''' if this set to "0" the gear will be ignored if not on water. Defaults to "1"
* '''speed-planing:'''
* '''spring-factor-not-planing:''' At zero speed the spring factor is multiplied by spring-factor-not-planing. Above speed-planing this factor is equal to 1. The idea is, to use this for floats simulating the transition from swimming to planing. speed-planing defaults to 0, spring-factor-not-planing defaults to 1.
* '''reduce-friction-by-extension:''' at full extension the friction is reduced by this relative value. 0.7 means 30% friction at full extension. If you specify a value greater than one, the friction will be zero before reaching full extension. Defaults to "0"
* '''ignored-by-solver:''' with the on-water/on-solid tags you can have more than one set of gears in one aircraft, If the solver (who automatically generates the spring constants) would take all gears into account, the result would be wrong. E. G. set this tag to "1" for all gears, which are not active on runways. Defaults to "0". You can not exclude all gears in the solving process.

===== Launchbar =====
Defines a catapult launchbar or strop.
* '''x,y,z:''' The location of the mount point of the launch bar or strop on the aircraft.
* '''length:''' The length of the launch bar from mount point to tip
* '''down-angle:''' The max angle below the horizontal the launchbar can achieve.
* '''up-angle:''' The max angle above the horizontal the launchbar can achieve.
* '''holdback-{x,y,z}:''' The location of the holdback mount point on the aircraft.
* '''holdback-length:''' The length of the holdback from mount point to tip. Note: holdback up-angle and down-angle are the same as those defined for the launchbar and are not specified in the configuration.

==== Fuel ====
===== tank =====
A fuel tank. Tanks in the aircraft are identified numerically (starting from zero), in the order they are defined in the file. If the left tank is first, "tank[0]" will be the left tank.
* '''x,y,z:''' The location of the tank.
* '''capacity:''' The maximum contents of the tank, in pounds. Not gallons -- YASim supports fuels of varying densities.
* '''jet:''' A boolean. If present, this causes the fuel density to be treated as Jet-A. Otherwise, gasoline density is used. A more elaborate density setting (in pounds per gallon, for example) would be easy to implement. Bug me.

==== Center of Gravity ====

===== Ballast =====
This is a mechanism for modifying the mass distribution of the aircraft. A ballast setting specifies that a particular amount of the empty weight of the aircraft must be placed at a given location. The remaining non-ballast weight will be distributed "intelligently" across the fuselage and wing objects. Note again: this does NOT change the empty weight of the aircraft.
* '''x,y,z:''' The location of the ballast.
* '''mass:''' How much mass, in pounds, to put there. Note that this value can be negative. I find that I often need to "lighten" the tail of the aircraft.

===== Weight =====
This is an added weight, something not part of the empty weight of the aircraft, like passengers, cargo, or external stores. The actual value of the mass is not specified here, instead, a mapping to a property is used. This allows external code, such as the panel, to control the weight (loading a given cargo configuration from preference files, dropping bombs at runtime, etc...)
* '''x,y,z:''' The location of the weight.
* '''mass-prop:''' The name of the fgfs property containing the mass, in pounds, of this weight.
* '''size:''' The aerodynamic "size", in metres, of the object. This is important for external stores, which will cause drag. For reasonably aerodynamic stuff like bombs, the size should be roughly the width of the object. For other stuff, you're on your own. The default is zero, which results in no aerodynamic force (internal cargo).
* '''solve-weight:''' Subtag of approach and cruise parameters. Used to specify a non-zero setting for a <weight> tag during solution. The default is to assume all weights are zero at the given performance numbers.
* '''idx:''' Index of the weight in the file (starting with zero).
* '''weight:''' Weight setting in pounds.

==== Controls ====
===== control-input =====
This element manages a mapping from fgfs properties (user input) to settable values on the aircraft's objects. Note that the value to be set MUST (!) be valid on the given object type. This is not checked for by the parser, and will cause a runtime crash if you try it. Wing's don't have throttle controls, etc... Note that multiple axes may be set on the same value. They are summed before setting.
* '''axis:''' The name of the double-valued fgfs property "axis" to use as input, such as "/controls/flight/aileron".
* '''control:''' Which control axis to set on the objects. It can have the following values:
** THROTTLE - The throttle on a jet or propeller.
** MIXTURE - The mixture on a propeller.
** REHEAT - The afterburner on a jet
** PROP - The propeller advance
** BRAKE - The brake on a gear.
** STEER - The steering angle on a gear.
** INCIDENCE - The incidence angle of a wing.
** FLAP0 - The flap0 deflection of a wing.
** FLAP1 - The flap1 deflection of a wing.
** SLAT - The slat extension of a wing.
** SPOILER - The spoiler extension for a wing.
** CYCLICAIL - The "aileron" cyclic input of a rotor
** CYCLICELE - The "elevator" cyclic input of a rotor
** COLLECTIVE - The collective input of a rotor
** ROTORENGINEON - If not equal zero the rotor is rotating
** WINCHRELSPEED - The relative winch speed
** {... and many more, see FGFDM.cpp ...}
* '''invert:''' Negate the value of the property before setting on the object.
* '''split:''' Applicable to wing control surfaces. Sets the normal value on the left wing, and a negated value on the right wing.
* '''square:''' Squares the value before setting. Useful for controls like steering that need a wide range, yet lots of sensitivity in the center. Obviously only applicable to values that have a range of [-1:1] or [0:1].
* '''src0/src1/dst0/dst1:''' If present, these defined a linear mapping from the source to the output value. Input values in the range src0-src1 are mapped linearly to dst0-dst1, with clamping for input values that lie outside the range.

===== control-output =====
This can be used to pass the value of a YASim control axis (after all mapping and summing is applied) back to the property tree.
* '''control:''' Name of the control axis. See above.
* '''prop:''' Property node to receive the value.
* '''side:''' Optional, for split controls. Either "right" or "left"
* '''min/max:''' Clamping applied to output value.

===== control-speed =====
Some controls (most notably flaps and hydraulics) have maximum slew rates and cannot respond instantly to pilot input. This can be implemented with a control-speed tag, which defines a "transition time" required to slew through the full input range. Note that this tag is semi-deprecated, complicated control input filtering can be done much more robustly from a Nasal script.
* '''control:''' Name of the control axis. See above.
* '''transition-time:''' Time in seconds to slew through input range.

===== control-setting =====
This tag is used to define a particular setting for a control axis inside the <cruise> or <approach> tags, where obviously property input is not available. It can be used, for example, to inform the solver that the approach performance values assume full flaps, etc...
* '''axis:''' Name of the control input (i.e. a property name)
* '''value:''' Value of the control axis.

==== Winch and Aerotow ====
===== hitch =====
A hitch, can be used for winch-start (in gliders) or aerotow (in gliders and motor aircraft) or for external cargo with helicopter. You can do aerotow over the net via multiplayer (see j3 and bocian as an example).
* '''name:''' the name of the hitch. must be aerotow if you want to do aerotow via multiplayer. You will find many properties at /sim/hitches/name. Most of them are directly tied to the internal variables, you can modify them as you like. You can add a listener to the property "broken", e. g. for playing a sound.
* '''x,y,z:''' The position of the hitch
* '''force-is-calculated-by-other:''' if you want to simulate aerotowing over the internet, set this value to "1" in the motor aircraft. Don't specify or set this to zero in gliders. In a LAN the time lag might be small enough to set it on both aircraft to "0". It's intended, that this is done automatically in the future.
===== tow =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''length:''' upstretched length in metres
* '''weight-per-meter:''' in kg/metre
* '''elastic-constant:''' lower values give higher elasticity
* '''break-force:''' in N
* '''mp-auto-connect-period:''' the every x seconds a towed multiplayer aircraft is searched. If found, this tow is connected automatically, parameters are copied from the other aircraft. Should be set only in the motor aircraft, not in the glider
===== winch =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''max-tow-length:''' in m
* '''min-tow-length''': in m
* '''initial-tow-length:''' in m. The initial tow length also defines the length/search radius used for the mp-autoconnect feature
* '''max-winch-speed:''' in m/s
* '''power:''' in kW
* '''max-force:''' in N

=== Visualization ===
[[File:Yasim_visualisation_dc6.png|thumb|dc6 fdm in Blender]]To make the programmed aircraft visible it is possible to load and compare it with the 3D model within [[Blender]]. The applaud for this ''very'' usefull script goes to M. Franz, thank you very much!

The script is located in FlightGears source code [http://mapserver.flightgear.org/git/?p=flightgear;a=blob_plain;f=utils/Modeller/yasim_import.py;hb=HEAD utils/Modeller/yasim_import.py].

The howto, taken from inside the script:

yasim_import.py loads and visualizes a YASim FDM geometry
=========================================================

It is recommended to load the model superimposed over a greyed out and immutable copy of the aircraft model:

(0) put this script into ~/.blender/scripts/
(1) load or import aircraft model (menu -> "File" -> "Import" -> "AC3D (.ac) ...")
(2) create new *empty* scene (menu -> arrow button left of "SCE:scene1" combobox -> "ADD NEW" -> "empty")
(3) rename scene to yasim (not required)
(4) link to scene1 (F10 -> "Output" tab -> arrow button left of text entry "No Set Scene" -> "scene1")
(5) now load the YASim config file (menu -> "File" -> "Import" -> "YASim (.xml) ...")

This is good enough for simple checks. But if you are working on the YASim configuration, then you need a
quick and convenient way to reload the file. In that case continue after (4):

(5) switch the button area at the bottom of the blender screen to "Scripts Window" mode (green python snake icon)
(6) load the YASim config file (menu -> "Scripts" -> "Import" -> "YASim (.xml) ...")
(7) make the "Scripts Window" area as small as possible by dragging the area separator down
(8) optionally split the "3D View" area and switch the right part to the "Outliner"
(9) press the "Reload YASim" button in the script area to reload the file

If the 3D model is displaced with respect to the FDM model, then the <offsets> values from the
model animation XML file should be added as comment to the YASim config file, as a line all by
itself, with no spaces surrounding the equal signs. Spaces elsewhere are allowed. For example:

<offsets>
<x-m>3.45</x-m>
<z-m>-0.4</z-m>
<pitch-deg>5</pitch-deg>
</offsets>

becomes:



Possible variables are:

x ... <x-m>
y ... <y-m>
z ... <z-m>
h ... <heading-deg>
p ... <pitch-deg>
r ... <roll-deg>

Of course, absolute FDM coordinates can then no longer directly be read from Blender's 3D view.
The cursor coordinates display in the script area, however, shows the coordinates in YASim space.
Note that object names don't contain XML indices but element numbers. YASim_hstab#2 is the third
hstab in the whole file, not necessarily in its parent XML group. A floating point part in the
object name (e.g. YASim_hstab#2.004) only means that the geometry has been reloaded that often.
It's an unavoidable consequence of how Blender deals with meshes.

Elements are displayed as follows:

cockpit -> monkey head
fuselage -> blue "tube" (with only 12 sides for less clutter); center at "a"
vstab -> red with yellow flaps
wing/mstab/hstab -> green with yellow flaps/spoilers/slats (always 20 cm deep);
symmetric surfaces are only displayed on the left side
thrusters (jet/propeller/thruster) -> dashed line from center to actionpt;
arrow from actionpt along thrust vector (always 1 m long);
propeller circle
rotor -> radius and rel_len_blade_start circle, direction arrow,
normal and forward vector, one blade at phi0
gear -> contact point and compression vector (no arrow head)
tank -> cube (10 cm side length)
weight -> inverted cone
ballast -> cylinder
hitch -> circle (10 cm diameter)
hook -> dashed line for up angle, T-line for down angle
launchbar -> dashed line for up angles, T-line for down angles
A note about step (0) for M$ users: the mentioned path is inside the folder where Blender lives, something like <code>C:\Program Files\Blender Foundation\Blender\.blender\scripts</code>.

=== Command Line ===

By use of a standard command line, we can see what the YASim solver is calculating. First, open up a command line prompt, and enter in the location of YASim.exe, and then the location of the YASim xml file. For example, here's what you would type in for a standard Windows 32-bit installation, and viewing the [[Boeing 777-200ER]]'s YASim file.

<code>"C:\Program Files\FlightGear\bin\Win32\yasim.exe" "C:\Program Files\FlightGear\data\Aircraft\777-200\777-200ER.xml"</code>

The quotes around the paths are required because of the spaces in the path names. Some other options can be used, but they are not needed for normal testing.

The results will give many different values.

* '''Drag Coefficient:''' The drag coefficient of the aircraft.
* '''Lift Ratio:''' The lift ratio of the aircraft.
* '''Cruise AoA:''' The cruise AoA, from conditions at <[[YASim#cruise|cruise]]> in the xml file.
* '''Tail Incidence:''' The incidence angle of the tail, "solved" by YASim as a way to stabilize the aircraft.
* '''Approach Elevator:''' The approach elevator, from conditions at <[[YASim#approach|approach]]> in the xml file.
* '''CG:''' Center of gravity of the aircraft in coordinates. Unless it's supposed to be offset, it should always have a Y value of 0.

=== YASim design notes ===

Andy Ross's original design notes for YASim can be found in [ftp://ftp.uni-duisburg.de/FlightGear/Docs/YASim-simnotes.pdf this PDF file]. These provide some useful background for how YASim works.

=== Additional resources ===
[http://www.buckarooshangar.com/flightgear/ Gary Neely's guide to YASim] is very helpful.

{{FDM}}

[[Category:Flight Dynamics Model]]

[[fr:YASim]]

YASim

2012-04-18T17:26:44Z

Buckaroo:

'''YASim''' is one of three [[flight dynamics model]]s commonly used by [[FlightGear]].

The flight dynamics model (FDM) determines how the [[aircraft]] moves and flies.

Gary Neely wrote in his [http://ltts.crlt.indiana.edu/grn/flightgear/yasim_1.html introduction to YASim]:

:''The FDM is the mathematical model that controls the physics of flight within the simulator. The physical 3D aircraft model has nothing to do with flight dynamics-- in essence it's just a picture to look at. It's the FDM that dictates how the model flies.''

:''Why YASim? YASim uses the geometry of the aircraft to generate the base flight characteristics. While this suggests a 'realistic' or out-of-the-box approach, it is a only rough approximation that will require much tweaking before you get a result that approaches realism. Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model. If you have solid flight data for your aircraft such as wind-tunnel data or you are looking to eventually generate a hyper-realistic simulation, JSBSim is probably a better approach. If you lack such data but know the geometry of the aircraft and have access to the same flight characteristics and limits as a real pilot would, then YASim can provide a solution that is more than sufficient for most simulation needs.''

===Coordinate system notes===
All positions specified are in metres (which is weird, since all other units in the file are English). The X axis points forward, Y is left, and Z is up. Take your right hand, and hold it like a gun. Your first and second fingers are the X and Y axes, and your upwards-pointing thumb is the Z. This is slightly different from the coordinate system used by [[JSBSim]]. Sorry. The origin can be placed anywhere, so long as you are consistent. I use the nose of the aircraft.

=== [[XML]] Elements ===
==== airplane ====
The top-level element for the file. It contains only one attribute:
* '''mass:''' The empty (no fuel) weight, in pounds. It does include the weight of the engine(s), so when you add the engine weight in its tag, it acts just like a ballast.

==== approach ====
The approach parameters for the aircraft. The solver will generate an aircraft that matches these settings. The element can (and should) contain <control> elements indicating pilot input settings, such as flaps and throttle, for the approach.
* '''speed:''' The approach airspeed, in knots TAS.
* '''aoa:''' The approach angle of attack, in degrees
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cruise ====
The cruise speed and altitude for the solver to match. As above, this should contain <control> elements indicating aircraft configuration. Especially, make sure the engines are generating enough thrust at cruise!
* '''speed:''' The cruise speed, in knots TAS.
* '''alt:''' The cruise altitude, in feet MSL.
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cockpit ====
The location of the cockpit (pilot eyepoint).
* '''x,y,z:''' eyepoint location (see coordinates note)

==== fuselage ====
This defines a tubelike structure. It will be given an even mass and aerodynamic force distribution by the solver. You can have as many as you like, in any orientation you please.
* '''ax,ay,az:''' One end of the tube (typically the front)
* '''bx,by,bz:''' The other ("back") end.
* '''width:''' The width of the tube, in metres.
* '''taper:''' The approximate radius at the "tips" of the fuselage expressed as a fraction (0-1) of the width value.
* '''midpoint:''' The location of the widest part of the fuselage, expressed as a fraction of the distance between A and B.
* '''idrag:''' Multiplier for the "induced drag" generated by this object. Default is one. With idrag=0 the fuselage generates only drag.
* '''cx,cy,cz:''' Factors for the generated drag in the fuselages "local coordinate system" with x pointing from end to front, z perpendicular to x with y=0 in the aircraft coordinate system. E.g. for a fuselage of a height of 2 times them width you can define cy=2 and (due to the doubled front surface) cx=2.

==== Surfaces ====
===== wing =====
This defines the main wing of the aircraft. You can have only one (but see below about using vstab objects for extra lifting surfaces). The wing should have a <stall> subelement to indicate stall behavior, control surface subelements (flap0, flap1, spoiler, slat) to indicate what and where the control surfaces are, and <control> subelements to map user input properties to the control surfaces.
* '''x,y,z:''' The "base" of the wing, specified as the location of the mid-chord (not leading edge, trailing edge, or aerodynamic center) point at the root of the LEFT (!) wing.
* '''length:''' The length from the base of the wing to the midchord point at the tip. Note that this is not the same thing as span.
* '''chord:''' The chord of the wing at its base, along the X axis (not normal to the leading edge, as it is sometimes defined).
* '''incidence:''' The incidence angle at the wing root, in degrees. Zero is level with the fuselage (as in an aerobatic plane), positive means that the leading edge is higher than the trailing edge (as in a trainer).
* '''twist:''' The difference between the incidence angle at the wing root and the incidence angle at the wing tip. Typically, this is a negative number so that the wing tips have a lower angle of attack and stall after the wing root (washout).
* '''taper:''' The taper fraction, expressed as the tip chord divided by the root chord. A taper of one is a hershey bar wing, and zero would be a wing ending at a point. Defaults to one.
* '''sweep:''' The sweep angle of the wing, in degrees. Zero is no sweep, positive angles are swept back. Defaults to zero.
* '''dihedral:''' The dihedral angle of the wing. Positive angles are upward dihedral. Defaults to zero.
* '''idrag:''' Multiplier for the "induced drag" generated by this surface. In general, low aspect wings will generate less induced drag per-AoA than high aspect (glider) wings. This value isn't constrained well by the solution process, and may require tuning to get throttle settings correct in high AoA (approach) situations.
* '''effectiveness:''' Multiplier for the "normal" drag generated by the wing. Defaults to 1. Arbitrary, dimensionless factor.
* '''camber:''' The lift produced by the wing at zero angle of attack, expressed as a fraction of the maximum lift produced at the stall AoA.

===== hstab =====
These defines the horizontal stabilizer of the aircraft. Internally, it is just a wing object and therefore works the same in XML. You are allowed only one hstab object; the solver needs to know which wing's incidence to play with to get the aircraft trimmed correctly.

===== vstab =====
A "vertical" stabilizer. Like hstab, this is just another wing, with a few special properties. The surface is not "mirrored" as are wing and hstab objects. If you define a left wing only, you'll only get a left wing. The default dihedral, if unspecified, is 90 degrees instead of zero. But all parameters are equally settable, so there's no requirement that this object be "vertical" at all. You can use it for anything you like, such as extra wings for biplanes. Most importantly, these surfaces are not involved with the solver computation, so you can have none, or as many as you like.

===== mstab =====
A mirrored horizontal stabilizer. Exactly the same as wing, but not involved with the solver computation, so you can have none, or as many as you like.

===== stall =====
A subelement of a wing (or hstab/vstab/mstab) that specifies the stall behavior.
* '''aoa:''' The stall angle (maximum lift) in degrees. Note that this is relative to the wing, not the fuselage (since the wing may have a non-zero incidence angle).
* '''width:''' The "width" of the stall, in degrees. A high value indicates a gentle stall. Low values are viscious for a non-twisted wing, but are acceptable for a twisted one (since the whole wing will not stall at the same time).
* '''peak:''' The height of the lift peak, relative to the post-stall secondary lift peak at 45 degrees. Defaults to 1.5. This one is deep voodoo, and probably doesn't need to change much. Bug me for an explanation if you're curious.

===== flap0, flap1, slat, spoiler =====
These are subelements of wing/hstab/vstab objects, and specify the location and effectiveness of the control surfaces.
* '''start:''' The position along the wing where the control surface begins.Zero is the root, one is the tip.
* '''end:''' The position where the surface ends, as above.
* '''lift:''' The lift multiplier for a flap or slat at full extension. One is a no-op, a typical aileron might be 1.2 or so, a giant jetliner flap 2.0, and a spoiler 0.0. For spoilers, the interpretation is a little different -- they spoil only "prestall" lift. Lift due purely to "flat plate" effects isn't affected. For typical wings that stall at low AoA's essentially all lift is pre-stall and you don't have to care. Jet fighters tend not to have wing spoilers, for exactly this reason. This value is not applicable to slats, which affect stall AoA only.
* '''drag:''' The drag multiplier, as above. Typically should be higher than the lift multiplier for flaps.
* '''aoa:''' Applicable only to slats. This indicates the angle by which the stall AoA is translated by the slat extension.

==== Engine ====
===== Thruster =====
A very simple "thrust only" engine object. Useful for things like thrust vectoring nozzles. All it does is map its THROTTLE input axis to its output thrust rating. Does not consume fuel, etc...
* '''thrust:''' Maximum thrust in pounds
* '''x,y,z:''' The point on the airframe where thrust will be applied.
* '''vx,vy,vy:''' The direction of the thrust in airframe coordinates. The vector will be normalized automatically, so any non-zero vector will work fine.

===== Jet =====
A turbojet/fan engine. It accepts a <control> subelement to map a property to its throttle setting, and an <actionpt> subelement to place the action point of the thrust at a different position than the mass of the engine.
* '''x,y,z:''' The location of the engine, as a point mass. If no actionpt is specified, this will also be the point of application of thrust.
* '''mass:''' The mass of the engine, in pounds.
* '''thrust:''' The maximum sea-level thrust, in pounds.
* '''afterburner:''' Maximum total thrust with afterburner/reheat, in pounds [defaults to "no additional thrust"].
* '''rotate:''' Vector angle of the thrust in degrees about the Y axis [0].
* '''n1-idle:''' Idling low pressure core / fan speed [55].
* '''n1-max:''' Maximum low pressure core / fan speed [102].
* '''n2-idle:''' Idling high pressure core speed [73].
* '''n2-max:''' Maximum high pressure core speed [103].
* '''tsfc:''' Thrust-specific fuel consumption [0.8]. This should be considerably lower for modern turbofans.
* '''egt:''' Exhaust gas temperature at takeoff in K [1050].
* '''epr:''' Engine pressure ratio at takeoff [3.0].
* '''exhaust-speed:''' The maximum exhaust speed in knots [~1555].
* '''spool-time:''' Time, in seconds, for the engine to respond to 90% of a commanded powersetting.

===== Propeller =====
A propeller. This element requires an engine subtag. Currently <piston-engine> and <turbine-engine> are supported.
* '''x,y,z:''' The position of the mass (!) of the engine/propeller combination. If the point of force application is different (and it will be) it should be set with an <actionpt> subelement.
* '''mass:''' The mass of the engine/propeller, in pounds.
* '''moment:''' The moment, in kg-metres^2. This has to be hand calculated and guessed at for now. A more automated system will be forthcoming. Use a negative moment value for counter-rotating ("European" -- CCW as seen from behind the prop) propellers. A good guess for this value is the radius of the prop (in metres) squared times the mass (kg) divided by three; that is the moment of a plain "stick" bolted to the prop shaft.
* '''radius:''' The radius, in metres, or the propeller.
* '''cruise-speed:''' The max efficiency cruise speed of the propeller. Generally not the same as the aircraft's cruise speed.
* '''cruise-rpm:''' The RPM of the propeller at max-eff. cruise.
* '''cruise-power:''' The power sunk by the prop at cruise, in horsepower.
* '''cruise-alt:''' The reference cruise altitude in feet.
* '''takeoff-power:''' The takeoff power required by the propeller...
* '''takeoff-rpm:''' ...at the given takeoff RPM.
* '''min-rpm:''' The minimum operational RPM for a constant speed propeller. This is the speed to which the prop governor will seek when the blue lever is at minimum. The coarse-stop attribute limits how far the governor can go into trying to reach this RPM.
* '''max-rpm:''' The maximum operational RPM for a constant speed propeller. See above. The fine-stop attribute limits how far the governor can go in trying to reach this RPM.
* '''fine-stop:''' The minimum pitch of the propeller (high RPM) as a ratio of ideal cruise pitch. This is set to 0.25 by default -- a higher value will result in a lower RPM at low power settings (e.g. idle, taxi, and approach).
* '''coarse-stop:''' The maximum pitch of the propeller (low RPM) as a ratio of ideal cruise pitch. This is set to 4.0 by default -- a lower value may result in a higher RPM at high power settings.
* '''gear-ratio:''' The factor by which the engine RPM is multiplied to produce the propeller RPM. Optional (defaults to 1.0).
* '''contra:''' When set (contra="1"), this indicates that the propeller is a contra-rotating pair. It will not contribute to the aircraft's net gyroscopic moment, nor will it produce asymmetric torque on the aircraft body. Asymmetric slipstream effects, when implemented, will also be zero when this is set.
* '''piston-engine:''' A piston engine definition. This must be a subelement of an enclosing <propeller> tag.
* '''eng-power:''' Maximum BHP of the engine at sea level.
* '''eng-rpm:''' The engine RPM at which eng-power is developed
* '''displacement:''' The engine displacement in cubic inches.
* '''compression:''' The engine compression ratio.

==== Landing gear ====
===== gear =====
Defines a landing gear. Accepts <control> subelements to map properties to steering and braking. Can also be used to simulate floats. Although the coefficients are still called ..fric, it is calculated in fluids as a drag (proportional to the square of the speed). In fluids gears are not considered to detect crashes (as on ground).
* '''x,y,z:''' The location of the fully-extended gear tip.
* '''compression:''' The distance in metres along the "up" axis that the gear will compress.
* '''initial-load:''' The initial load of the spring in multiples of compression. Defaults to 0. (With this parameter a lower spring-constants will be used for the gear-> can reduce numerical problems (jitter)) '''Note:''' the spring-constant is varied from 0% compression to 20% compression to get continuous behavior around 0 compression. (could be physically explained by wheel deformation)
* '''upx/upy/upz:''' The direction of compression, defaults to vertical (0,0,1) if unspecified. These are used only for a direction -- the vector need not be normalized, as the length is specified by "compression".
* '''sfric:''' Static (non-skidding) coefficient of friction. Defaults to 0.8.
* '''dfric:''' Dynamic friction. Defaults to 0.7.
* '''spring:''' A dimensionless multiplier for the automatically generated spring constant. Increase to make the gear stiffer, decrease to make it squishier.
* '''damp:''' A dimensionless multiplier for the automatically generated damping coefficient. Decrease to make the gear "bouncier", increase to make it "slower". Beware of increasing this too far: very high damping forces can make the numerics unstable. If you can't make the gear stop bouncing with this number, try increasing the compression length instead.
* '''on-water:''' if this is set to "0" the gear will be ignored if on water. Defaults to "0"
* '''on-solid:''' if this set to "0" the gear will be ignored if not on water. Defaults to "1"
* '''speed-planing:'''
* '''spring-factor-not-planing:''' At zero speed the spring factor is multiplied by spring-factor-not-planing. Above speed-planing this factor is equal to 1. The idea is, to use this for floats simulating the transition from swimming to planing. speed-planing defaults to 0, spring-factor-not-planing defaults to 1.
* '''reduce-friction-by-extension:''' at full extension the friction is reduced by this relative value. 0.7 means 30% friction at full extension. If you specify a value greater than one, the friction will be zero before reaching full extension. Defaults to "0"
* '''ignored-by-solver:''' with the on-water/on-solid tags you can have more than one set of gears in one aircraft, If the solver (who automatically generates the spring constants) would take all gears into account, the result would be wrong. E. G. set this tag to "1" for all gears, which are not active on runways. Defaults to "0". You can not exclude all gears in the solving process.

===== Launchbar =====
Defines a catapult launchbar or strop.
* '''x,y,z:''' The location of the mount point of the launch bar or strop on the aircraft.
* '''length:''' The length of the launch bar from mount point to tip
* '''down-angle:''' The max angle below the horizontal the launchbar can achieve.
* '''up-angle:''' The max angle above the horizontal the launchbar can achieve.
* '''holdback-{x,y,z}:''' The location of the holdback mount point on the aircraft.
* '''holdback-length:''' The length of the holdback from mount point to tip. Note: holdback up-angle and down-angle are the same as those defined for the launchbar and are not specified in the configuration.

==== Fuel ====
===== tank =====
A fuel tank. Tanks in the aircraft are identified numerically (starting from zero), in the order they are defined in the file. If the left tank is first, "tank[0]" will be the left tank.
* '''x,y,z:''' The location of the tank.
* '''capacity:''' The maximum contents of the tank, in pounds. Not gallons -- YASim supports fuels of varying densities.
* '''jet:''' A boolean. If present, this causes the fuel density to be treated as Jet-A. Otherwise, gasoline density is used. A more elaborate density setting (in pounds per gallon, for example) would be easy to implement. Bug me.

==== Center of Gravity ====

===== Ballast =====
This is a mechanism for modifying the mass distribution of the aircraft. A ballast setting specifies that a particular amount of the empty weight of the aircraft must be placed at a given location. The remaining non-ballast weight will be distributed "intelligently" across the fuselage and wing objects. Note again: this does NOT change the empty weight of the aircraft.
* '''x,y,z:''' The location of the ballast.
* '''mass:''' How much mass, in pounds, to put there. Note that this value can be negative. I find that I often need to "lighten" the tail of the aircraft.

===== Weight =====
This is an added weight, something not part of the empty weight of the aircraft, like passengers, cargo, or external stores. The actual value of the mass is not specified here, instead, a mapping to a property is used. This allows external code, such as the panel, to control the weight (loading a given cargo configuration from preference files, dropping bombs at runtime, etc...)
* '''x,y,z:''' The location of the weight.
* '''mass-prop:''' The name of the fgfs property containing the mass, in pounds, of this weight.
* '''size:''' The aerodynamic "size", in metres, of the object. This is important for external stores, which will cause drag. For reasonably aerodynamic stuff like bombs, the size should be roughly the width of the object. For other stuff, you're on your own. The default is zero, which results in no aerodynamic force (internal cargo).
* '''solve-weight:''' Subtag of approach and cruise parameters. Used to specify a non-zero setting for a <weight> tag during solution. The default is to assume all weights are zero at the given performance numbers.
* '''idx:''' Index of the weight in the file (starting with zero).
* '''weight:''' Weight setting in pounds.

==== Controls ====
===== control-input =====
This element manages a mapping from fgfs properties (user input) to settable values on the aircraft's objects. Note that the value to be set MUST (!) be valid on the given object type. This is not checked for by the parser, and will cause a runtime crash if you try it. Wing's don't have throttle controls, etc... Note that multiple axes may be set on the same value. They are summed before setting.
* '''axis:''' The name of the double-valued fgfs property "axis" to use as input, such as "/controls/flight/aileron".
* '''control:''' Which control axis to set on the objects. It can have the following values:
** THROTTLE - The throttle on a jet or propeller.
** MIXTURE - The mixture on a propeller.
** REHEAT - The afterburner on a jet
** PROP - The propeller advance
** BRAKE - The brake on a gear.
** STEER - The steering angle on a gear.
** INCIDENCE - The incidence angle of a wing.
** FLAP0 - The flap0 deflection of a wing.
** FLAP1 - The flap1 deflection of a wing.
** SLAT - The slat extension of a wing.
** SPOILER - The spoiler extension for a wing.
** CYCLICAIL - The "aileron" cyclic input of a rotor
** CYCLICELE - The "elevator" cyclic input of a rotor
** COLLECTIVE - The collective input of a rotor
** ROTORENGINEON - If not equal zero the rotor is rotating
** WINCHRELSPEED - The relative winch speed
** {... and many more, see FGFDM.cpp ...}
* '''invert:''' Negate the value of the property before setting on the object.
* '''split:''' Applicable to wing control surfaces. Sets the normal value on the left wing, and a negated value on the right wing.
* '''square:''' Squares the value before setting. Useful for controls like steering that need a wide range, yet lots of sensitivity in the center. Obviously only applicable to values that have a range of [-1:1] or [0:1].
* '''src0/src1/dst0/dst1:''' If present, these defined a linear mapping from the source to the output value. Input values in the range src0-src1 are mapped linearly to dst0-dst1, with clamping for input values that lie outside the range.

===== control-output =====
This can be used to pass the value of a YASim control axis (after all mapping and summing is applied) back to the property tree.
* '''control:''' Name of the control axis. See above.
* '''prop:''' Property node to receive the value.
* '''side:''' Optional, for split controls. Either "right" or "left"
* '''min/max:''' Clamping applied to output value.

===== control-speed =====
Some controls (most notably flaps and hydraulics) have maximum slew rates and cannot respond instantly to pilot input. This can be implemented with a control-speed tag, which defines a "transition time" required to slew through the full input range. Note that this tag is semi-deprecated, complicated control input filtering can be done much more robustly from a Nasal script.
* '''control:''' Name of the control axis. See above.
* '''transition-time:''' Time in seconds to slew through input range.

===== control-setting =====
This tag is used to define a particular setting for a control axis inside the <cruise> or <approach> tags, where obviously property input is not available. It can be used, for example, to inform the solver that the approach performance values assume full flaps, etc...
* '''axis:''' Name of the control input (i.e. a property name)
* '''value:''' Value of the control axis.

==== Winch and Aerotow ====
===== hitch =====
A hitch, can be used for winch-start (in gliders) or aerotow (in gliders and motor aircraft) or for external cargo with helicopter. You can do aerotow over the net via multiplayer (see j3 and bocian as an example).
* '''name:''' the name of the hitch. must be aerotow if you want to do aerotow via multiplayer. You will find many properties at /sim/hitches/name. Most of them are directly tied to the internal variables, you can modify them as you like. You can add a listener to the property "broken", e. g. for playing a sound.
* '''x,y,z:''' The position of the hitch
* '''force-is-calculated-by-other:''' if you want to simulate aerotowing over the internet, set this value to "1" in the motor aircraft. Don't specify or set this to zero in gliders. In a LAN the time lag might be small enough to set it on both aircraft to "0". It's intended, that this is done automatically in the future.
===== tow =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''length:''' upstretched length in metres
* '''weight-per-meter:''' in kg/metre
* '''elastic-constant:''' lower values give higher elasticity
* '''break-force:''' in N
* '''mp-auto-connect-period:''' the every x seconds a towed multiplayer aircraft is searched. If found, this tow is connected automatically, parameters are copied from the other aircraft. Should be set only in the motor aircraft, not in the glider
===== winch =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''max-tow-length:''' in m
* '''min-tow-length''': in m
* '''initial-tow-length:''' in m. The initial tow length also defines the length/search radius used for the mp-autoconnect feature
* '''max-winch-speed:''' in m/s
* '''power:''' in kW
* '''max-force:''' in N

=== Visualization ===
[[File:Yasim_visualisation_dc6.png|thumb|dc6 fdm in Blender]]To make the programmed aircraft visible it is possible to load and compare it with the 3D model within [[Blender]]. The applaud for this ''very'' usefull script goes to M. Franz, thank you very much!

The script is located in FlightGears source code [http://mapserver.flightgear.org/git/?p=flightgear;a=blob_plain;f=utils/Modeller/yasim_import.py;hb=HEAD utils/Modeller/yasim_import.py].

The howto, taken from inside the script:

yasim_import.py loads and visualizes a YASim FDM geometry
=========================================================

It is recommended to load the model superimposed over a greyed out and immutable copy of the aircraft model:

(0) put this script into ~/.blender/scripts/
(1) load or import aircraft model (menu -> "File" -> "Import" -> "AC3D (.ac) ...")
(2) create new *empty* scene (menu -> arrow button left of "SCE:scene1" combobox -> "ADD NEW" -> "empty")
(3) rename scene to yasim (not required)
(4) link to scene1 (F10 -> "Output" tab -> arrow button left of text entry "No Set Scene" -> "scene1")
(5) now load the YASim config file (menu -> "File" -> "Import" -> "YASim (.xml) ...")

This is good enough for simple checks. But if you are working on the YASim configuration, then you need a
quick and convenient way to reload the file. In that case continue after (4):

(5) switch the button area at the bottom of the blender screen to "Scripts Window" mode (green python snake icon)
(6) load the YASim config file (menu -> "Scripts" -> "Import" -> "YASim (.xml) ...")
(7) make the "Scripts Window" area as small as possible by dragging the area separator down
(8) optionally split the "3D View" area and switch the right part to the "Outliner"
(9) press the "Reload YASim" button in the script area to reload the file

If the 3D model is displaced with respect to the FDM model, then the <offsets> values from the
model animation XML file should be added as comment to the YASim config file, as a line all by
itself, with no spaces surrounding the equal signs. Spaces elsewhere are allowed. For example:

<offsets>
<x-m>3.45</x-m>
<z-m>-0.4</z-m>
<pitch-deg>5</pitch-deg>
</offsets>

becomes:



Possible variables are:

x ... <x-m>
y ... <y-m>
z ... <z-m>
h ... <heading-deg>
p ... <pitch-deg>
r ... <roll-deg>

Of course, absolute FDM coordinates can then no longer directly be read from Blender's 3D view.
The cursor coordinates display in the script area, however, shows the coordinates in YASim space.
Note that object names don't contain XML indices but element numbers. YASim_hstab#2 is the third
hstab in the whole file, not necessarily in its parent XML group. A floating point part in the
object name (e.g. YASim_hstab#2.004) only means that the geometry has been reloaded that often.
It's an unavoidable consequence of how Blender deals with meshes.

Elements are displayed as follows:

cockpit -> monkey head
fuselage -> blue "tube" (with only 12 sides for less clutter); center at "a"
vstab -> red with yellow flaps
wing/mstab/hstab -> green with yellow flaps/spoilers/slats (always 20 cm deep);
symmetric surfaces are only displayed on the left side
thrusters (jet/propeller/thruster) -> dashed line from center to actionpt;
arrow from actionpt along thrust vector (always 1 m long);
propeller circle
rotor -> radius and rel_len_blade_start circle, direction arrow,
normal and forward vector, one blade at phi0
gear -> contact point and compression vector (no arrow head)
tank -> cube (10 cm side length)
weight -> inverted cone
ballast -> cylinder
hitch -> circle (10 cm diameter)
hook -> dashed line for up angle, T-line for down angle
launchbar -> dashed line for up angles, T-line for down angles
A note about step (0) for M$ users: the mentioned path is inside the folder where Blender lives, something like <code>C:\Program Files\Blender Foundation\Blender\.blender\scripts</code>.

=== Command Line ===

By use of a standard command line, we can see what the YASim solver is calculating. First, open up a command line prompt, and enter in the location of YASim.exe, and then the location of the YASim xml file. For example, here's what you would type in for a standard Windows 32-bit installation, and viewing the [[Boeing 777-200ER]]'s YASim file.

<code>"C:\Program Files\FlightGear\bin\Win32\yasim.exe" "C:\Program Files\FlightGear\data\Aircraft\777-200\777-200ER.xml"</code>

The quotes around the paths are required because of the spaces in the path names. Some other options can be used, but they are not needed for normal testing.

The results will give many different values.

* '''Drag Coefficient:''' The drag coefficient of the aircraft.
* '''Lift Ratio:''' The lift ratio of the aircraft.
* '''Cruise AoA:''' The cruise AoA, from conditions at <[[YASim#cruise|cruise]]> in the xml file.
* '''Tail Incidence:''' The incidence angle of the tail, "solved" by YASim as a way to stabilize the aircraft.
* '''Approach Elevator:''' The approach elevator, from conditions at <[[YASim#approach|approach]]> in the xml file.
* '''CG:''' Center of gravity of the aircraft in coordinates. Unless it's supposed to be offset, it should always have a Y value of 0.

=== YASim design notes ===

Andy Ross's original design notes for YASim can be found in [ftp://ftp.uni-duisburg.de/FlightGear/Docs/YASim-simnotes.pdf this PDF file]. These provide some useful background for how YASim works.

=== Additional resources ===
[http://www.buckarooshangar.com/flightgear/ Gary Neely's guide to YASim] is very helpful.

{{FDM}}

[[Category:Flight Dynamics Model]]

[[fr:YASim]]

YASim

2012-04-18T17:21:45Z

Buckaroo:

'''YASim''' is one of three [[flight dynamics model]]s commonly used by [[FlightGear]].

The flight dynamics model (FDM) determines how the [[aircraft]] moves and flies.

Gary Neely wrote in his [http://ltts.crlt.indiana.edu/grn/flightgear/yasim_1.html introduction to YASim]:

:''The FDM is the mathematical model that controls the physics of flight within the simulator. The physical 3D aircraft model has nothing to do with flight dynamics-- in essence it's just a picture to look at. It's the FDM that dictates how the model flies.''

:''Why YASim? YASim uses the geometry of the aircraft to generate the base flight characteristics. While this suggests a 'realistic' or out-of-the-box approach, it is a only rough approximation that will require much tweaking before you get a result that approaches realism. Contrast this with JSBSim which relies on pre-generated tabular data to build up the flight model. If you have solid flight data for your aircraft such as wind-tunnel data or you are looking to eventually generate a hyper-realistic simulation, JSBSim is probably a better approach. If you lack such data but know the geometry of the aircraft and have access to the same flight characteristics and limits as a real pilot would, then YASim can provide a solution that is more than sufficient for most simulation needs.''

===Coordinate system notes===
All positions specified are in metres (which is weird, since all other units in the file are English). The X axis points forward, Y is left, and Z is up. Take your right hand, and hold it like a gun. Your first and second fingers are the X and Y axes, and your upwards-pointing thumb is the Z. This is slightly different from the coordinate system used by [[JSBSim]]. Sorry. The origin can be placed anywhere, so long as you are consistent. I use the nose of the aircraft.

=== [[XML]] Elements ===
==== airplane ====
The top-level element for the file. It contains only one attribute:
* '''mass:''' The empty (no fuel) weight, in pounds. It does include the weight of the engine(s), so when you add the engine weight in its tag, it acts just like a ballast.

==== approach ====
The approach parameters for the aircraft. The solver will generate an aircraft that matches these settings. The element can (and should) contain <control> elements indicating pilot input settings, such as flaps and throttle, for the approach.
* '''speed:''' The approach airspeed, in knots TAS.
* '''aoa:''' The approach angle of attack, in degrees
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cruise ====
The cruise speed and altitude for the solver to match. As above, this should contain <control> elements indicating aircraft configuration. Especially, make sure the engines are generating enough thrust at cruise!
* '''speed:''' The cruise speed, in knots TAS.
* '''alt:''' The cruise altitude, in feet MSL.
* '''fuel:''' Fraction (0-1) of fuel in the tanks. Default is 0.2.
==== cockpit ====
The location of the cockpit (pilot eyepoint).
* '''x,y,z:''' eyepoint location (see coordinates note)

==== fuselage ====
This defines a tubelike structure. It will be given an even mass and aerodynamic force distribution by the solver. You can have as many as you like, in any orientation you please.
* '''ax,ay,az:''' One end of the tube (typically the front)
* '''bx,by,bz:''' The other ("back") end.
* '''width:''' The width of the tube, in metres.
* '''taper:''' The approximate radius at the "tips" of the fuselage expressed as a fraction (0-1) of the width value.
* '''midpoint:''' The location of the widest part of the fuselage, expressed as a fraction of the distance between A and B.
* '''idrag:''' Multiplier for the "induced drag" generated by this object. Default is one. With idrag=0 the fuselage generates only drag.
* '''cx,cy,cz:''' Factors for the generated drag in the fuselages "local coordinate system" with x pointing from end to front, z perpendicular to x with y=0 in the aircraft coordinate system. E.g. for a fuselage of a height of 2 times them width you can define cy=2 and (due to the doubled front surface) cx=2.

==== Surfaces ====
===== wing =====
This defines the main wing of the aircraft. You can have only one (but see below about using vstab objects for extra lifting surfaces). The wing should have a <stall> subelement to indicate stall behavior, control surface subelements (flap0, flap1, spoiler, slat) to indicate what and where the control surfaces are, and <control> subelements to map user input properties to the control surfaces.
* '''x,y,z:''' The "base" of the wing, specified as the location of the mid-chord (not leading edge, trailing edge, or aerodynamic center) point at the root of the LEFT (!) wing.
* '''length:''' The length from the base of the wing to the midchord point at the tip. Note that this is not the same thing as span.
* '''chord:''' The chord of the wing at its base, along the X axis (not normal to the leading edge, as it is sometimes defined).
* '''incidence:''' The incidence angle at the wing root, in degrees. Zero is level with the fuselage (as in an aerobatic plane), positive means that the leading edge is higher than the trailing edge (as in a trainer).
* '''twist:''' The difference between the incidence angle at the wing root and the incidence angle at the wing tip. Typically, this is a negative number so that the wing tips have a lower angle of attack and stall after the wing root (washout).
* '''taper:''' The taper fraction, expressed as the tip chord divided by the root chord. A taper of one is a hershey bar wing, and zero would be a wing ending at a point. Defaults to one.
* '''sweep:''' The sweep angle of the wing, in degrees. Zero is no sweep, positive angles are swept back. Defaults to zero.
* '''dihedral:''' The dihedral angle of the wing. Positive angles are upward dihedral. Defaults to zero.
* '''idrag:''' Multiplier for the "induced drag" generated by this surface. In general, low aspect wings will generate less induced drag per-AoA than high aspect (glider) wings. This value isn't constrained well by the solution process, and may require tuning to get throttle settings correct in high AoA (approach) situations.
* '''effectiveness:''' Multiplier for the "normal" drag generated by the wing. Defaults to 1. Arbitrary, dimensionless factor.
* '''camber:''' The lift produced by the wing at zero angle of attack, expressed as a fraction of the maximum lift produced at the stall AoA.

===== hstab =====
These defines the horizontal stabilizer of the aircraft. Internally, it is just a wing object and therefore works the same in XML. You are allowed only one hstab object; the solver needs to know which wing's incidence to play with to get the aircraft trimmed correctly.

===== vstab =====
A "vertical" stabilizer. Like hstab, this is just another wing, with a few special properties. The surface is not "mirrored" as are wing and hstab objects. If you define a left wing only, you'll only get a left wing. The default dihedral, if unspecified, is 90 degrees instead of zero. But all parameters are equally settable, so there's no requirement that this object be "vertical" at all. You can use it for anything you like, such as extra wings for biplanes. Most importantly, these surfaces are not involved with the solver computation, so you can have none, or as many as you like.

===== mstab =====
A mirrored horizontal stabilizer. Exactly the same as wing, but not involved with the solver computation, so you can have none, or as many as you like.

===== stall =====
A subelement of a wing (or hstab/vstab/mstab) that specifies the stall behavior.
* '''aoa:''' The stall angle (maximum lift) in degrees. Note that this is relative to the wing, not the fuselage (since the wing may have a non-zero incidence angle).
* '''width:''' The "width" of the stall, in degrees. A high value indicates a gentle stall. Low values are viscious for a non-twisted wing, but are acceptable for a twisted one (since the whole wing will not stall at the same time).
* '''peak:''' The height of the lift peak, relative to the post-stall secondary lift peak at 45 degrees. Defaults to 1.5. This one is deep voodoo, and probably doesn't need to change much. Bug me for an explanation if you're curious.

===== flap0, flap1, slat, spoiler =====
These are subelements of wing/hstab/vstab objects, and specify the location and effectiveness of the control surfaces.
* '''start:''' The position along the wing where the control surface begins.Zero is the root, one is the tip.
* '''end:''' The position where the surface ends, as above.
* '''lift:''' The lift multiplier for a flap or slat at full extension. One is a no-op, a typical aileron might be 1.2 or so, a giant jetliner flap 2.0, and a spoiler 0.0. For spoilers, the interpretation is a little different -- they spoil only "prestall" lift. Lift due purely to "flat plate" effects isn't affected. For typical wings that stall at low AoA's essentially all lift is pre-stall and you don't have to care. Jet fighters tend not to have wing spoilers, for exactly this reason. This value is not applicable to slats, which affect stall AoA only.
* '''drag:''' The drag multiplier, as above. Typically should be higher than the lift multiplier for flaps.
* '''aoa:''' Applicable only to slats. This indicates the angle by which the stall AoA is translated by the slat extension.

==== Engine ====
===== Thruster =====
A very simple "thrust only" engine object. Useful for things like thrust vectoring nozzles. All it does is map its THROTTLE input axis to its output thrust rating. Does not consume fuel, etc...
* '''thrust:''' Maximum thrust in pounds
* '''x,y,z:''' The point on the airframe where thrust will be applied.
* '''vx,vy,vy:''' The direction of the thrust in airframe coordinates. The vector will be normalized automatically, so any non-zero vector will work fine.

===== Jet =====
A turbojet/fan engine. It accepts a <control> subelement to map a property to its throttle setting, and an <actionpt> subelement to place the action point of the thrust at a different position than the mass of the engine.
* '''x,y,z:''' The location of the engine, as a point mass. If no actionpt is specified, this will also be the point of application of thrust.
* '''mass:''' The mass of the engine, in pounds.
* '''thrust:''' The maximum sea-level thrust, in pounds.
* '''afterburner:''' Maximum total thrust with afterburner/reheat, in pounds [defaults to "no additional thrust"].
* '''rotate:''' Vector angle of the thrust in degrees about the Y axis [0].
* '''n1-idle:''' Idling low pressure core / fan speed [55].
* '''n1-max:''' Maximum low pressure core / fan speed [102].
* '''n2-idle:''' Idling high pressure core speed [73].
* '''n2-max:''' Maximum high pressure core speed [103].
* '''tsfc:''' Thrust-specific fuel consumption [0.8]. This should be considerably lower for modern turbofans.
* '''egt:''' Exhaust gas temperature at takeoff in K [1050].
* '''epr:''' Engine pressure ratio at takeoff [3.0].
* '''exhaust-speed:''' The maximum exhaust speed in knots [~1555].
* '''spool-time:''' Time, in seconds, for the engine to respond to 90% of a commanded powersetting.

===== Propeller =====
A propeller. This element requires an engine subtag. Currently <piston-engine> and <turbine-engine> are supported.
* '''x,y,z:''' The position of the mass (!) of the engine/propeller combination. If the point of force application is different (and it will be) it should be set with an <actionpt> subelement.
* '''mass:''' The mass of the engine/propeller, in pounds.
* '''moment:''' The moment, in kg-metres^2. This has to be hand calculated and guessed at for now. A more automated system will be forthcoming. Use a negative moment value for counter-rotating ("European" -- CCW as seen from behind the prop) propellers. A good guess for this value is the radius of the prop (in metres) squared times the mass (kg) divided by three; that is the moment of a plain "stick" bolted to the prop shaft.
* '''radius:''' The radius, in metres, or the propeller.
* '''cruise-speed:''' The max efficiency cruise speed of the propeller. Generally not the same as the aircraft's cruise speed.
* '''cruise-rpm:''' The RPM of the propeller at max-eff. cruise.
* '''cruise-power:''' The power sunk by the prop at cruise, in horsepower.
* '''cruise-alt:''' The reference cruise altitude in feet.
* '''takeoff-power:''' The takeoff power required by the propeller...
* '''takeoff-rpm:''' ...at the given takeoff RPM.
* '''min-rpm:''' The minimum operational RPM for a constant speed propeller. This is the speed to which the prop governor will seek when the blue lever is at minimum. The coarse-stop attribute limits how far the governor can go into trying to reach this RPM.
* '''max-rpm:''' The maximum operational RPM for a constant speed propeller. See above. The fine-stop attribute limits how far the governor can go in trying to reach this RPM.
* '''fine-stop:''' The minimum pitch of the propeller (high RPM) as a ratio of ideal cruise pitch. This is set to 0.25 by default -- a higher value will result in a lower RPM at low power settings (e.g. idle, taxi, and approach).
* '''coarse-stop:''' The maximum pitch of the propeller (low RPM) as a ratio of ideal cruise pitch. This is set to 4.0 by default -- a lower value may result in a higher RPM at high power settings.
* '''gear-ratio:''' The factor by which the engine RPM is multiplied to produce the propeller RPM. Optional (defaults to 1.0).
* '''contra:''' When set (contra="1"), this indicates that the propeller is a contra-rotating pair. It will not contribute to the aircraft's net gyroscopic moment, nor will it produce asymmetric torque on the aircraft body. Asymmetric slipstream effects, when implemented, will also be zero when this is set.
* '''piston-engine:''' A piston engine definition. This must be a subelement of an enclosing <propeller> tag.
* '''eng-power:''' Maximum BHP of the engine at sea level.
* '''eng-rpm:''' The engine RPM at which eng-power is developed
* '''displacement:''' The engine displacement in cubic inches.
* '''compression:''' The engine compression ratio.

==== Landing gear ====
===== gear =====
Defines a landing gear. Accepts <control> subelements to map properties to steering and braking. Can also be used to simulate floats. Although the coefficients are still called ..fric, it is calculated in fluids as a drag (proportional to the square of the speed). In fluids gears are not considered to detect crashes (as on ground).
* '''x,y,z:''' The location of the fully-extended gear tip.
* '''compression:''' The distance in metres along the "up" axis that the gear will compress.
* '''initial-load:''' The initial load of the spring in multiples of compression. Defaults to 0. (With this parameter a lower spring-constants will be used for the gear-> can reduce numerical problems (jitter)) '''Note:''' the spring-constant is varied from 0% compression to 20% compression to get continuous behavior around 0 compression. (could be physically explained by wheel deformation)
* '''upx/upy/upz:''' The direction of compression, defaults to vertical (0,0,1) if unspecified. These are used only for a direction -- the vector need not be normalized, as the length is specified by "compression".
* '''sfric:''' Static (non-skidding) coefficient of friction. Defaults to 0.8.
* '''dfric:''' Dynamic friction. Defaults to 0.7.
* '''spring:''' A dimensionless multiplier for the automatically generated spring constant. Increase to make the gear stiffer, decrease to make it squishier.
* '''damp:''' A dimensionless multiplier for the automatically generated damping coefficient. Decrease to make the gear "bouncier", increase to make it "slower". Beware of increasing this too far: very high damping forces can make the numerics unstable. If you can't make the gear stop bouncing with this number, try increasing the compression length instead.
* '''on-water:''' if this is set to "0" the gear will be ignored if on water. Defaults to "0"
* '''on-solid:''' if this set to "0" the gear will be ignored if not on water. Defaults to "1"
* '''speed-planing:'''
* '''spring-factor-not-planing:''' At zero speed the spring factor is multiplied by spring-factor-not-planing. Above speed-planing this factor is equal to 1. The idea is, to use this for floats simulating the transition from swimming to planing. speed-planing defaults to 0, spring-factor-not-planing defaults to 1.
* '''reduce-friction-by-extension:''' at full extension the friction is reduced by this relative value. 0.7 means 30% friction at full extension. If you specify a value greater than one, the friction will be zero before reaching full extension. Defaults to "0"
* '''ignored-by-solver:''' with the on-water/on-solid tags you can have more than one set of gears in one aircraft, If the solver (who automatically generates the spring constants) would take all gears into account, the result would be wrong. E. G. set this tag to "1" for all gears, which are not active on runways. Defaults to "0". You can not exclude all gears in the solving process.

===== Launchbar =====
Defines a catapult launchbar or strop.
* '''x,y,z:''' The location of the mount point of the launch bar or strop on the aircraft.
* '''length:''' The length of the launch bar from mount point to tip
* '''down-angle:''' The max angle below the horizontal the launchbar can achieve.
* '''up-angle:''' The max angle above the horizontal the launchbar can achieve.
* '''holdback-{x,y,z}:''' The location of the holdback mount point on the aircraft.
* '''holdback-length:''' The length of the holdback from mount point to tip. Note: holdback up-angle and down-angle are the same as those defined for the launchbar and are not specified in the configuration.

==== Fuel ====
===== tank =====
A fuel tank. Tanks in the aircraft are identified numerically (starting from zero), in the order they are defined in the file. If the left tank is first, "tank[0]" will be the left tank.
* '''x,y,z:''' The location of the tank.
* '''capacity:''' The maximum contents of the tank, in pounds. Not gallons -- YASim supports fuels of varying densities.
* '''jet:''' A boolean. If present, this causes the fuel density to be treated as Jet-A. Otherwise, gasoline density is used. A more elaborate density setting (in pounds per gallon, for example) would be easy to implement. Bug me.

==== Center of Gravity ====

===== Ballast =====
This is a mechanism for modifying the mass distribution of the aircraft. A ballast setting specifies that a particular amount of the empty weight of the aircraft must be placed at a given location. The remaining non-ballast weight will be distributed "intelligently" across the fuselage and wing objects. Note again: this does NOT change the empty weight of the aircraft.
* '''x,y,z:''' The location of the ballast.
* '''mass:''' How much mass, in pounds, to put there. Note that this value can be negative. I find that I often need to "lighten" the tail of the aircraft.

===== Weight =====
This is an added weight, something not part of the empty weight of the aircraft, like passengers, cargo, or external stores. The actual value of the mass is not specified here, instead, a mapping to a property is used. This allows external code, such as the panel, to control the weight (loading a given cargo configuration from preference files, dropping bombs at runtime, etc...)
* '''x,y,z:''' The location of the weight.
* '''mass-prop:''' The name of the fgfs property containing the mass, in pounds, of this weight.
* '''size:''' The aerodynamic "size", in metres, of the object. This is important for external stores, which will cause drag. For reasonably aerodynamic stuff like bombs, the size should be roughly the width of the object. For other stuff, you're on your own. The default is zero, which results in no aerodynamic force (internal cargo).
* '''solve-weight:''' Subtag of approach and cruise parameters. Used to specify a non-zero setting for a <weight> tag during solution. The default is to assume all weights are zero at the given performance numbers.
* '''idx:''' Index of the weight in the file (starting with zero).
* '''weight:''' Weight setting in pounds.

==== Controls ====
===== control-input =====
This element manages a mapping from fgfs properties (user input) to settable values on the aircraft's objects. Note that the value to be set MUST (!) be valid on the given object type. This is not checked for by the parser, and will cause a runtime crash if you try it. Wing's don't have throttle controls, etc... Note that multiple axes may be set on the same value. They are summed before setting.
* '''axis:''' The name of the double-valued fgfs property "axis" to use as input, such as "/controls/flight/aileron".
* '''control:''' Which control axis to set on the objects. It can have the following values:
** THROTTLE - The throttle on a jet or propeller.
** MIXTURE - The mixture on a propeller.
** REHEAT - The afterburner on a jet
** PROP - The propeller advance
** BRAKE - The brake on a gear.
** STEER - The steering angle on a gear.
** INCIDENCE - The incidence angle of a wing.
** FLAP0 - The flap0 deflection of a wing.
** FLAP1 - The flap1 deflection of a wing.
** SLAT - The slat extension of a wing.
** SPOILER - The spoiler extension for a wing.
** CYCLICAIL - The "aileron" cyclic input of a rotor
** CYCLICELE - The "elevator" cyclic input of a rotor
** COLLECTIVE - The collective input of a rotor
** ROTORENGINEON - If not equal zero the rotor is rotating
** WINCHRELSPEED - The relative winch speed
** {... and many more, see FGFDM.cpp ...}
* '''invert:''' Negate the value of the property before setting on the object.
* '''split:''' Applicable to wing control surfaces. Sets the normal value on the left wing, and a negated value on the right wing.
* '''square:''' Squares the value before setting. Useful for controls like steering that need a wide range, yet lots of sensitivity in the center. Obviously only applicable to values that have a range of [-1:1] or [0:1].
* '''src0/src1/dst0/dst1:''' If present, these defined a linear mapping from the source to the output value. Input values in the range src0-src1 are mapped linearly to dst0-dst1, with clamping for input values that lie outside the range.

===== control-output =====
This can be used to pass the value of a YASim control axis (after all mapping and summing is applied) back to the property tree.
* '''control:''' Name of the control axis. See above.
* '''prop:''' Property node to receive the value.
* '''side:''' Optional, for split controls. Either "right" or "left"
* '''min/max:''' Clamping applied to output value.

===== control-speed =====
Some controls (most notably flaps and hydraulics) have maximum slew rates and cannot respond instantly to pilot input. This can be implemented with a control-speed tag, which defines a "transition time" required to slew through the full input range. Note that this tag is semi-deprecated, complicated control input filtering can be done much more robustly from a Nasal script.
* '''control:''' Name of the control axis. See above.
* '''transition-time:''' Time in seconds to slew through input range.

===== control-setting =====
This tag is used to define a particular setting for a control axis inside the <cruise> or <approach> tags, where obviously property input is not available. It can be used, for example, to inform the solver that the approach performance values assume full flaps, etc...
* '''axis:''' Name of the control input (i.e. a property name)
* '''value:''' Value of the control axis.

==== Winch and Aerotow ====
===== hitch =====
A hitch, can be used for winch-start (in gliders) or aerotow (in gliders and motor aircraft) or for external cargo with helicopter. You can do aerotow over the net via multiplayer (see j3 and bocian as an example).
* '''name:''' the name of the hitch. must be aerotow if you want to do aerotow via multiplayer. You will find many properties at /sim/hitches/name. Most of them are directly tied to the internal variables, you can modify them as you like. You can add a listener to the property "broken", e. g. for playing a sound.
* '''x,y,z:''' The position of the hitch
* '''force-is-calculated-by-other:''' if you want to simulate aerotowing over the internet, set this value to "1" in the motor aircraft. Don't specify or set this to zero in gliders. In a LAN the time lag might be small enough to set it on both aircraft to "0". It's intended, that this is done automatically in the future.
===== tow =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''length:''' upstretched length in metres
* '''weight-per-meter:''' in kg/metre
* '''elastic-constant:''' lower values give higher elasticity
* '''break-force:''' in N
* '''mp-auto-connect-period:''' the every x seconds a towed multiplayer aircraft is searched. If found, this tow is connected automatically, parameters are copied from the other aircraft. Should be set only in the motor aircraft, not in the glider
===== winch =====
The tow used for aerotow or winch. This must be a subelement of an enclosing <hitch> tag.
* '''max-tow-length:''' in m
* '''min-tow-length''': in m
* '''initial-tow-length:''' in m. The initial tow length also defines the length/search radius used for the mp-autoconnect feature
* '''max-winch-speed:''' in m/s
* '''power:''' in kW
* '''max-force:''' in N

=== Visualization ===
[[File:Yasim_visualisation_dc6.png|thumb|dc6 fdm in Blender]]To make the programmed aircraft visible it is possible to load and compare it with the 3D model within [[Blender]]. The applaud for this ''very'' usefull script goes to M. Franz, thank you very much!

The script is located in FlightGears source code [http://mapserver.flightgear.org/git/?p=flightgear;a=blob_plain;f=utils/Modeller/yasim_import.py;hb=HEAD utils/Modeller/yasim_import.py].

The howto, taken from inside the script:

yasim_import.py loads and visualizes a YASim FDM geometry
=========================================================

It is recommended to load the model superimposed over a greyed out and immutable copy of the aircraft model:

(0) put this script into ~/.blender/scripts/
(1) load or import aircraft model (menu -> "File" -> "Import" -> "AC3D (.ac) ...")
(2) create new *empty* scene (menu -> arrow button left of "SCE:scene1" combobox -> "ADD NEW" -> "empty")
(3) rename scene to yasim (not required)
(4) link to scene1 (F10 -> "Output" tab -> arrow button left of text entry "No Set Scene" -> "scene1")
(5) now load the YASim config file (menu -> "File" -> "Import" -> "YASim (.xml) ...")

This is good enough for simple checks. But if you are working on the YASim configuration, then you need a
quick and convenient way to reload the file. In that case continue after (4):

(5) switch the button area at the bottom of the blender screen to "Scripts Window" mode (green python snake icon)
(6) load the YASim config file (menu -> "Scripts" -> "Import" -> "YASim (.xml) ...")
(7) make the "Scripts Window" area as small as possible by dragging the area separator down
(8) optionally split the "3D View" area and switch the right part to the "Outliner"
(9) press the "Reload YASim" button in the script area to reload the file

If the 3D model is displaced with respect to the FDM model, then the <offsets> values from the
model animation XML file should be added as comment to the YASim config file, as a line all by
itself, with no spaces surrounding the equal signs. Spaces elsewhere are allowed. For example:

<offsets>
<x-m>3.45</x-m>
<z-m>-0.4</z-m>
<pitch-deg>5</pitch-deg>
</offsets>

becomes:



Possible variables are:

x ... <x-m>
y ... <y-m>
z ... <z-m>
h ... <heading-deg>
p ... <pitch-deg>
r ... <roll-deg>

Of course, absolute FDM coordinates can then no longer directly be read from Blender's 3D view.
The cursor coordinates display in the script area, however, shows the coordinates in YASim space.
Note that object names don't contain XML indices but element numbers. YASim_hstab#2 is the third
hstab in the whole file, not necessarily in its parent XML group. A floating point part in the
object name (e.g. YASim_hstab#2.004) only means that the geometry has been reloaded that often.
It's an unavoidable consequence of how Blender deals with meshes.

Elements are displayed as follows:

cockpit -> monkey head
fuselage -> blue "tube" (with only 12 sides for less clutter); center at "a"
vstab -> red with yellow flaps
wing/mstab/hstab -> green with yellow flaps/spoilers/slats (always 20 cm deep);
symmetric surfaces are only displayed on the left side
thrusters (jet/propeller/thruster) -> dashed line from center to actionpt;
arrow from actionpt along thrust vector (always 1 m long);
propeller circle
rotor -> radius and rel_len_blade_start circle, direction arrow,
normal and forward vector, one blade at phi0
gear -> contact point and compression vector (no arrow head)
tank -> cube (10 cm side length)
weight -> inverted cone
ballast -> cylinder
hitch -> circle (10 cm diameter)
hook -> dashed line for up angle, T-line for down angle
launchbar -> dashed line for up angles, T-line for down angles
A note about step (0) for M$ users: the mentioned path is inside the folder where Blender lives, something like <code>C:\Program Files\Blender Foundation\Blender\.blender\scripts</code>.

=== Command Line ===

By use of a standard command line, we can see what the YASim solver is calculating. First, open up a command line prompt, and enter in the location of YASim.exe, and then the location of the YASim xml file. For example, here's what you would type in for a standard Windows 32-bit installation, and viewing the [[Boeing 777-200ER]]'s YASim file.

<code>"C:\Program Files\FlightGear\bin\Win32\yasim.exe" "C:\Program Files\FlightGear\data\Aircraft\777-200\777-200ER.xml"</code>

The quotes around the paths are required because of the spaces in the path names. Some other options can be used, but they are not needed for normal testing.

The results will give many different values.

* '''Drag Coefficient:''' The drag coefficient of the aircraft.
* '''Lift Ratio:''' The lift ratio of the aircraft.
* '''Cruise AoA:''' The cruise AoA, from conditions at <[[YASim#cruise|cruise]]> in the xml file.
* '''Tail Incidence:''' The incidence angle of the tail, "solved" by YASim as a way to stabilize the aircraft.
* '''Approach Elevator:''' The approach elevator, from conditions at <[[YASim#approach|approach]]> in the xml file.
* '''CG:''' Center of gravity of the aircraft in coordinates. Unless it's supposed to be offset, it should always have a Y value of 0.

=== YASim design notes ===

Andy Ross's original design notes for YASim can be found in [ftp://ftp.uni-duisburg.de/FlightGear/Docs/YASim-simnotes.pdf this PDF file]. These provide some useful background for how YASim works.

=== Additional resources ===
[http://ltts.crlt.indiana.edu/grn/flightgear/yasim_1.html Gary Neely's guide to YASIM] is very helpful.

{{FDM}}

[[Category:Flight Dynamics Model]]

[[fr:YASim]]

FlightGear hangars

2012-01-12T21:37:31Z

Buckaroo: /* Hangars */

''See [[Links]] for an overall listing of FlightGear related external websites''

FlightGear has [[aircraft]] and other content available from 3rd-party hangars, some which are GPL compatible and also included in official distributions while others are independent. Aircraft versions range from requiring a developmental build, to being compatible with the latest primary release, to requiring an older version.

Be careful with external links!

=== Official hangars ===
* [http://www.flightgear.org/download/aircraft-v2-4/ FlightGear Official 2.4 Hangar]
* [http://www.flightgear.org/Downloads/aircraft-2.0.0/ FlightGear Official 2.0 Hangar] (Legacy site)
* [http://gitorious.org/fg/fgdata/trees/master/Aircraft Git Hangar] (for [[Git]] builds)
* [http://liveries.flightgear.org FlightGear Liveries]

=== Hangars ===
* [http://alphashangar.co.nr/ Alpha-J's Hangar] (Aircraft, Liveries, Scenery, AI, etc.)
* [http://www.gidenstam.org/FlightGear/Airships/ Anders Lighter-than-air Hangar]
* <s>[http://bravosflightgear.yolasite.com/ Bravo's FlightGear] (Airbus A318-100) </s>
* [http://www.buckarooshangar.com/flightgear/ Buckaroo's Hangar] (Velocity XL RG, Edgley Optica, Lockheed 1049H Constellation, Grumman Goose, McDonnell Douglas MD-81) (& a YASim intro)
* <s>[http://members.cox.net/davidculp/hangar.html Dave's Hangar]</s> (also [http://daveshangar.blogspot.com/ Dave's Hangar Blog])
* [http://www.sol2500.net/flightgear/aircraft.html DFaber Hangar] (Eurofighter, PC-6, Bf 109, Beufighter, F4U, Ju 52, DH Mosquito, G. Albatross, F-86, and more)
* [http://flier95-flightgear.blogspot.com/ Flier95's Hangar] (Blog format)
* [http://charles.ingels.free.fr/flightgear/ French FlightGear Hangar] (FR) (Aermacchi MB326, Dassault Mirage F1 Mikoyan Gurevitch Mig 31 Foxhound, and more)
* [http://fgnl.freehostia.com/ Gijs Hangar] (Aircraft, Liveries, Scenery, Vehicles)
* [http://pagesperso-orange.fr/GRTux/tux/index-en.html GRTux Hangar] (28+ aircraft and add-ons)
* [http://hcilab.uniud.it/pan/downloads.html HCI Lab - University of Udine] (Aermacchi MB339 Frecce Tricolori)
* [http://helijah.free.fr/flightgear/hangar.htm Helijah FlightGear Hangar] (164+ original aircraft)
* [http://hhfgfs.weebly.com/index.html Hellcat's FlightGear Hangar] (scenarios, skins, film inspired aerospace vehicles)
* [http://www.hoerbird.net/aircrafts.html Hoerbird Hangar] (misc. projects)
* <s>[http://icestar-fghangar.web44.net/ Icecode's & Star's Hangar] (under development)</s>
* [http://mysite.verizon.net/vzeuyecs/ Kent Esbenshade's Boneyard Hangar] (Classic aircraft)
* [http://flightgear.bplaced.de/ longfly's hangar] (not only German!)
** [http://flightgear.bplaced.de/filemanager/aircraft-list/index.html list of all aircrafts] (under development)
* [http://nickfg.blogspot.com/ Nick's FlightGear Hangar] (Blog, CRJ-200)
* [http://members.cox.net/scotsg8r/hangar/ N-SCOT's Hangar] (5+ liveries & mods)
* [http://theomegahangar.yolasite.com/ Omega Hangar] (Embraer E-jet Family, A330-200, A320neo, CRJ-700 Full First Class, ATR-42-family, A321-series, Mobile Stairway)
* [http://pjedvaj.eu5.org/ pjedvaj's Hangar] (Mikoyan-Gurevich MiG-21bis, Pilatus PC-9M, Pilatus PC-21, Lockheed Martin F-35B Lightning II)
* [http://thefancyflightgearhangar.blogspot.com the fancy flight gear hangar] (a few well made aircraft)
* [http://presteshangar.wikidot.com/start Prestes Hangar] (many Brazilian aircraft articles)
* [http://riktov.synthasite.com/ Riktov's FlightGear Hangar] (BN-2 Islander, Giant Marshmallow Man)
* [http://digilander.libero.it/scighera_fg/index.html Scighera's Hangar] (models & liveries)
* <s>[http://skyopshangar.byethost17.com/ Skyop's FlightGear Hangar] (717, 757-200, A300, A320-family, A330-300, A340-300, ATR 72, CRJ900, Paper airplane, & scenery)</s>
* [http://seahorseCorral.org/flightgear_aircraft.html Stewart's SEA-horse Aircraft Hanger]
* [http://sydhangar.daffodil.uk.com/ Syd's Hangar ] (older 1.9 versions) [https://sites.google.com/site/sydshangar/ Syd's Google Hangar ] (newer 2.0 versions)
* [http://macflightgear.sourceforge.net/home/aircraft Tat's Aircraft for FlightGear] (A6M2 "Zero", J7W, Ki-84, T-4, HondaJet, OH-1, K5Y1, RV-6A, YS-11)
* [http://vicmar.weebly.com/ VicMar] (Yanagisawa Gen H-4, Stung Biker, Quad Bikes, SRN4, Water Skier, G2 Thunderpack, Martin Jetpack)
* [http://www.treborlogic.com/fgfs/hangar/ Yourgod's Hangar: Douglas DC-8]
* [https://www.gitorious.org/airbus-aircraft Airbus Aircraft Development Git] (A320, A330, A340-300, A380 - various authors)

==== Livery hangars ====
* [http://berwickskins.yolasite.com/ Berwick-skins]
* [http://dliveryhangar.synthasite.com/ Dodger4's Livery Hangar]
* [http://jchnd.blogspot.com/ JcHnd's Liveries for FlightGear]
* [http://mojos-hangar.webs.com/ MOJO's Flightgear Livery Hangar]
* [http://simbabeathangar.webs.com/ Simbabeat's Livery Hangar]

==== Homepages, blogs, etc. ====

* [http://geoffmclane.com/fg/index.htm FlightGear Build Centre]
* [http://www.flightgearcanada.ca/ FlightGear Canada] (The home of everything Canadian for FlightGear)
* [http://www.fguk.eu/ FlightGear United Kingdom]
* <s>[http://www.flightgear-germany.de/ FlightGear Germany] (DE)</s>
* [http://flightgear2009.blogspot.com/ Flight Gear Brasil 2009] (non-english)
* [http://www.shialeweb.com/caballerosaguila/news.php Caballeros Aguila] (non-english)
* [http://www.emmerich-j.de/FGFS/index.html jomo's FlightGear Homepage]
* [http://tehwarlock.tk/ Tehwarlock Blog]
* [http://flightgearblog.blogspot.com/ FlightGear Blog] (Last post Dec. 2008)
* [http://www.jaunty.bplaced.net/flightgear/index.php a small FlightGear page]
* [http://flightgearcorner.wordpress.com/ The FlightGear Corner] (News, Downloads, Tutorials and more)
* [http://www.vivefg.org/ Vive FlightGear!] Aircrafts, scenery, manuals and forum (non-english)
* [http://flightgear.mxchange.org/ Quix0r's FlightGear Website] Simple tutorials and fgdata.bundle

=== Other FlightGear repositories/mirrors ===
* [http://www.unitedfreeworld.com/ unitedfreeworld] (scenery, plane models, and livery)
* [http://www.flightgearplanes.com Flightgear Planes Website]
* [http://ftp.riken.go.jp/pub/FreeBSD/distfiles/flightgear-aircrafts/ Older versions of FlightGear aircraft]

=== Old Hangars ===
* [http://croo.murgl.org/fgfs/index.html A-10 and A-6 stuff]
* [http://www.ae.uiuc.edu/m-selig/apasim/Aircraft-uiuc.html UIUC Hangar] (for FGFS 0.7.8, last update 2002)

=== Related content ===
* [[Table of models]]
* [[Aircraft]] - [[Helicopter]] - [[Vehicle]]

[[Category:List]]

FlightGear hangars

2010-10-04T17:49:03Z

Buckaroo: /* Developer & User Hangars */

''See [[Links]] for a overall listing of FlightGear related external websites''

FlightGear has many [[aircraft]] available from 3rd-party hangars, some which are GPL compatible and also included in official distributions while others are independent. Aircraft versions range from requiring a [[CVS]] build, to being compatible with [[FlightGear 1.9.0|version 1.9.0]], although some may still need [[FlightGear 1.0]] or [[0.9.10|older]] if an archive has not been updated.

===Official Hangars===
*[http://www.flightgear.org/Downloads/aircraft-2.0.0/ FlightGear Official 2.0 Hangar]
*[http://gitorious.org/fg/fgdata/trees/master/Aircraft Git Hangar] (for [[Git]] builds)
*[http://liveries.flightgear.org FlightGear Liveries]

===Other FlightGear download hosts===
*[http://www.unitedfreeworld.com/ unitedfreeworld] (scenery, plane models, and livery)
*[http://www.AAliveries.yolasite.com/ AA Liveries] (Aircraft Modifications and liveries)

===Developer & User Hangars===
*[http://alphashangar.co.nr/ Alpha-J's Hangar]
*[http://www.flightgearplanes.com Flightgear Planes Website]
*[http://skyopshangar.byethost17.com/ Skyop's FlightGear Hangar]
*[http://simbabeathangar.webs.com/ Simbabeat's Livery Hangar]
*[http://seahorseCorral.org/flightgear_aircraft.html Stewart's SEA-horse Aircraft Hanger]
*[http://helijah.free.fr/flightgear/hangar.htm Helijah FGFS Hangar]
*[http://www.gidenstam.org/FlightGear/Airships/ Anders Lighter-than-air Hangar]
*[http://home.comcast.net/~davidculp2/hangar/hangar.html David Culp Hangar]
*[http://fgnl.freehostia.com/ Gijs Hangar]
*[http://pagesperso-orange.fr/GRTux/tux/index-en.html GRTux Hangar]
*[http://www.sol2500.net/flightgear/aircraft.html DFaber Hangar]
*[http://www.hoerbird.net/aircrafts.html Hoerbird Hangar]
*[http://croo.murgl.org/fgfs/index.html A-10 and A-6 stuff]
*[http://www.flightgearliveries.ning.com Liam's Hangar (for plane Re-paints and add-ons)]
*[http://ffgfs.free.fr/FlightGear/index.php?page=0 Dyn'aero MCR Sportster, Colomban MC-15 Cri-Cri, Piaggio Aero P-180 Avanti II, Dassault Rafale B, and Bombardier CRJ700]
*[http://mdsmith2.oxyhost.com/hangar.html Michael Smith's Hangar]
*[http://ltts.crlt.indiana.edu/grn/flightgear/ Buckaroo's Hangar: Lockheed 1049H Constellation, Grumman Goose, McDonnell Douglas MD-81]
*[http://macflightgear.sourceforge.net/home/aircraft Tat's Aircraft for FlightGear]
*[http://jchnd.blogspot.com/ JcHnd's Liveries for FlightGear]
*[http://www.xs4all.nl/~dtalsma/flightgear.html FlightGear AI Aircraft Download Page]
*[http://presteshangar.wikidot.com/start Prestes Hangar]
*[http://projectvirtualgear.co.cc Project Virtual Gear]
*[http://sydhangar.daffodil.uk.com/ Syd's Hangar]
*[http://www.treborlogic.com/fgfs/hangar/ Yourgod's Hangar: Douglas DC-8]
*[http://sites.google.com/site/pjedvajflightgear/ pjedvaj's Hangar]

===Outdated Hangars===
*[http://www.ae.uiuc.edu/m-selig/apasim/Aircraft-uiuc.html UIUC Hangar]
*[http://ftp.riken.go.jp/pub/FreeBSD/distfiles/flightgear-aircrafts/ Older versions of FlightGear aircraft]

===Related content===
*[[Table of models]]
*[[Aircraft]] - [[Helicopter]] - [[Vehicle]]

[[Category:List]]

FlightGear hangars

2009-05-16T16:17:20Z

Buckaroo: /* Developer & User Hangars */