Chapter 4
Takeoff: How to start the program

4.1 Launching the simulator under Unix/Linux

Under Linux (or any other flavor of Unix), FlightGear will be invoked by

runfgfs --option1 --option2...,

where the options will be described in Section 4.4 below.

If something strange happens while using this shell script, if you want to do some debugging (i.e. using ”strace”) or if you just feel nice to be ”keen”, then you can start FlightGear directly by executing the ”fgfs” binary. In this case you should at least add one variable to your environment, which is needed to locate the (mostly) shared library built from the sources of the SimGear package. Please add the respective directory to your LD_LIBRARY_PATH. You can do so with the following on Bourne shell (compatibles):

 LD_LIBRARY_PATH=/usr/local/FlightGear/lib:$LD_LIBRARY_PATH
 export LD_LIBRARY_PATH/

or on C shell (compatibles):

 setenv LD_LIBRARY_PATH
 /usr/local/FlightGear/lib:$LD_LIBRARY_PATH

Besides this (used by the dynamic linker) ”fgfs” knows about the following environment variable

FG_ROOT: root directory for the FlightGear base package; this corresponds to the --fg-root=path option as described in Sec. 4.4.1

4.2 Launching the simulator under Windows

Before starting the simulator, you may want to adapt the file webrun.bat situated in the main FlightGear directory. Open the file with an editor

In Windows explorer, change to the directory /FlightGear and double-click runfgfs.bat.

Fig. 3: Ready for takeoff. Waiting at the default startup position at San Francisco Itl., KSFO.

Alternatively, if for one or the other reason the batch file does not work or is missing, you can open an MS-DOS shell, change to the directory where your binary resides (typically something like c:/FlightGear/bin where you might have to substitute c: in favor of your FlightGear directory), set the environment variable via (note the backslashes!)

SET FG_ROOT=c:\FlightGear\bin

and invoke FlightGear (within the same MS-DOS shell, as environment settings are only valid locally within the same shell) via

fgfs --option1 --option2....

Of course, you can create your own runfgfs.bat with Windows Editor using the two lines above.

For getting maximum performance it is recommended to minimize (iconize) the text output window while running FlightGear.

4.3 Launching the simulator under Mac OS X

Say you downloaded the base package and binary to yout home directory. Then you can open Terminal.app and execute the following sequence:

setenv FG_ROOT  /fgfs-base-X.X.X ./fgfs-X.X.X.-date
--option1 -- option 2 (one line)

or

./fgfs-X.X.X-version-date --fg-root=fgfs-base-X.X.X
--option1 --option2. (one line)

4.4 Command line parameters

Following is a list and short description of the numerous command line options available for FlightGear. If you are running FlightGear under Windows you can include these into runfgfs.bat.

However, in case of options you want to re-use continually (like joystick settings) it is recommended to include them into a file called .fgfsrc under Unix systems and system.fgfsrc, resp. under Windows. This file has to be in the top FlightGear directory (for instance /usr/local/Flightgear). As it depends on your preferences, it is not delivered with FlightGear, but can be created with any text editor (notepad, emacs, vi, if you like). Examples for such a file (including a detailed description on the configuration of joysticks) can be found at

http://rockfish.net/shell/aboutjoy.txt.

4.4.1 General Options

• --help, -h: Gives a small help text, kind of a short version of this Section.
• --fg-root=path: Tells FlightGear where to look for its data files if you didn’t compile it with the default settings.
• --fg-scenery=path: Allows specification of a path to the scenery directorypath , in case scenery is not at the default position under
  /Flightgear/Scenery; this might be especially useful in case you have scenery on a CD-ROM.
• --disable-game-mode: Disables full screen display.
• --enable-game-mode: Enables full screen display.
• --disable-splash-screen: Turns off the rotating 3DFX logo when the accelerator board gets initialized (3DFX only).
• --enable-splash-screen: If you like advertising, set this!
• --disable-intro-music: No audio sample is being played when FlightGear starts up. Suggested in case of trouble with playing the intro.
• --enable-intro-music: If your machine is powerful enough, enjoy this setting.
• --disable-mouse-pointer: Disables mouse interface.
• --enable-mouse-pointer: Enables mouse interface. Useful in full screen mode for old Voodoo/VoodooII based cards.
• --disable-freeze: This will put you into FlightGear with the engine running, ready for Take-Off.
• --enable-freeze: Starts FlightGear in frozen state.
• --disable-fuel-freeze: Fuel is consumed normally.
• --enable-fuel-freeze: Fuel tank quantity is forced to remain constant.
• --disable-tod-freeze: Time of day advances normally.
• --enable-tod-freeze: Do not advance time of day.
• --control-mode: Specify your control device (joystick, keyboard, mouse) Defaults to joystick (yoke).
• --disable-auto-coordination: Switches auto coordination between aileron/rudder off (default).
• --enable-auto-coordination: Switches auto coordination between aileron/rudder on (recommended without pedals).
• --browser-app=/path/to/app: specify location of your web browser. Example: --browser-app=
  ''C:\Programme\Internet Explorer\iexplore.exe'' (Note the ” ” because of the broken word Internet Explorer!).
• --prop:name=value: set property name to value
  Example: --prop:/engines/engine0/running=true for starting with running engines. Another example:
  --aircraft=c172
  --prop:/consumables/fuels/tank[0]/level-gal=10
  --prop:/consumables/fuels/tank[1]/level-gal=10
  filles the Cessna for a short flight.
• --config=path: Load additional properties from the given path. Example: runfgfs --config=./Aircraft/X15-set.xml
• --units-feed: Use feet for distances.
• --units-meters: Use meters for distances.

4.4.2 Features

• --disable-hud: Switches off the HUD (Head Up Display).
• --enable-hud: Turns the HUD on.
• --enable-anti-aliased-hud: Turns on anti-aliaseded HUD lines for better quality, if hardware supports this.
• --disable-anti-aliased-hud: Turns off anti-aliaseded HUD lines.
• --enable-panel: Turns the instrument panel on (default).
• --disable-panel: Turns the instrument panel off.
• --disable-sound: Self explaining.
• --enable-sound: See above.

4.4.3 Flight model

• --aircraft=name of aircraft definition file Example: --aircraft=c310. For possible choices check the directory /FlightGear/Aircraft. Do not include the extension ''-set.xml'' into the aircraft name but use the remaining beginning of the respective file names for choosing an aircraft. This way flight model, panel etc. are all loaded in a consistent way.
• --fdm=abcd Select the core flight model. Options are jsb, larcsim, yasim, magic, balloon, external, ada, null. Default value is jsb (JSBSim). larcsim is the flight model which FlightGear inherited from the LaRCSim simulator. yasim is Any Ross’ Yet Another Flight Dynamics Simulator. Magic is a slew mode. Balloon is a hot air balloon. External refers to remote control of the simulator. Null selects no flight dynamics model at all. The UIUC flight model is not chosen this way but via the next option! For further information on flight models cf. Section 1.4 and below.
• --aero=abcd Specifies the aircraft model to load. Default is a Cessna c172. Alternatives available depend on the flight model chosen.
• --model-hz=n Run the Flight Dynamics Model with this rate (iterations per second).
• --speed=n Run the Flight Dynamics Model this much faster than real time.
• --notrim Do NOT attempt to trim the model when initializing JSBSim.
• --on-ground: Start up at ground level (default).
• --in-air: Start up in the air. Naturally, you have to specify an initial altitude as below for this to make sense. This is a must for the X15.
• --wind=DIR@SPEED: Specify wind coming from the direction DIR (in degrees) at speed SPEED (knots).

4.4.4 Aircraft model directory (Only for the UIUC Flight Dynamics Model)

• --aircraft-dir=path: Aircraft directory relative to the root-path, defined via $FG_ROOT or --fg-root.

Remark: The difference in the handling of UIUC models has historic reasons. These models use the LaRCsim FDM. As this FDM isn’t the default FDM any more you have to specify it manually. Also the airplane description needs manual interaction as you have to specify the directory by hand where the specific aircraft data resides. So you have to use the following for flying the ’TwinOtter’:

fgfs --fdm=larcsim --aero=uiuc

--aircraft-dir=Aircraft-uiuc/TwinOtter

Fortunately work has been done to simplificate this. At least those airplanes can be flown easily by using an appropriate ’--aircraft’-string. These are the following:

--aircraft=747-uiuc, --aircraft=beech99-uiuc,
--aircraft=c172-uiuc, --aircraft=c310-uiuc

If time permits the remaining aircrafts will be adjusted soon. Please have a look at $FG_ROOT/Aircraft-uiuc for the avaliable aircrafts provided by the UIUC model collection. Also please read the notes in Section 1.4 on UIUC.

4.4.5 Initial Position and Orientation

• --airport-id=ABCD: If you want to start directly at an airport, enter its international code, i.e. KJFK for JFK airport in New York etc. A long/short list of the IDs of the airports being implemented can be found in /Flight Gear/Airports. You only have to unpack one of the files with gunzip. Keep in mind, you need the terrain data for the relevant region, though!
• --offset-distance=nm: Here you can specify the distance to threshold in nm.
• --offset-azimuth=deg: Here you can specify the heading to threshold in degrees.
• --lon=degrees: This is the startup longitude in degrees (west = -).
• --lat=degrees: This is the startup latitude in degrees (south = -).
• --altitude=feet: This is useful if you want to start in free flight in connection with --in-air. Altitude specified in feet unless you choose --units-meters.
• --heading=degrees: Sets the initial heading (yaw angle) in degrees.
• --roll=degrees: Sets the startup roll angle (roll angle) in degrees.
• --pitch=degrees: Sets the startup pitch angle (pitch angle) in degrees.
• --uBody=feet per second: Speed along the body X axis in feet per second, unless you choose --units-meters.
• --vBody=feet per second: Speed along the body Y axis in feet per second, unless you choose --units-meters.
• --wBody=feet per second: Speed along the body Z axis in feet per second, unless you choose --units-meters.
• --vc=knots: Allows specifying the initial airspeed in knots (only in connection with --fdm=jsb).
• --mach=num: Allows specifying the initial airspeed as Mach number (only in connection with --fdm=jsb).

4.4.6 Rendering Options

• --bpp=depth: Specify the bits per pixel.
• --fog-disable: To cut down the rendering efforts, distant regions are vanishing in fog by default. If you disable fogging, you’ll see farther but your frame rates will drop.
• --fog-fastest: The scenery will not look very nice but frame rate will increase.
• --fog-nicest: This option will give you a fairly realistic view of flying on a hazy day.
• --enable-clouds: Enable cloud layer (default).
• --disable-clouds: Disable cloud layer.
• --clouds-asl=xxx: Specify altitude of cloud layer above sea level.
• --fov=xx.x: Sets the field of view in degrees. Default is 55.0.
• --disable-fullscreen: Disable full screen mode (default).
• --enable-fullscreen: Enable full screen mode.
• --shading-flat: This is the fastest mode but the terrain will look ugly! This option might help if your video processor is really slow.
• --shading-smooth: This is the recommended (and default) setting - things will look really nice.
• --disable-skyblend: No fogging or haze, sky will be displayed using just one color. Fast but ugly!
• --enable-skyblend: Fogging/haze is enabled, sky and terrain look realistic. This is the default and recommended setting.
• --disable-textures: Terrain details will be disabled. Looks ugly, but might help if your video board is slow.
• --enable-textures: Default and recommended.
• --enable-wireframe: If you want to know how the world of FlightGear looks like internally, try this!
• --disable-wireframe: No wireframe. Default.
• --geometry=WWWxHHH: Defines the size of the window used, i.e. WWWxHHH can be 640x480, 800x600, or 1024x768.
• --view-offset=xxx: Allows setting the default forward view direction as an offset from straight ahead. Possible values are LEFT, RIGHT, CENTER, or a specific number of degrees. Useful for multi-window display.
• --visibility=meters: You can specify the initial visibility in meters here.
• --visibility-miles=miles: You can specify the initial visibility in miles here.

4.4.7 HUD Options

• --hud-tris: HUD displays the number of triangles rendered.
• --hud-culled: HUD displays percentage of triangles culled.

4.4.8 Time Options

• --time-offset=[+-]hh:mm:ss: Offset local time by this amount.
• --time-match-real: Synchronize real-world and FlightGear time.
• --time-match-local: Synchronize local real-world and FlightGear time.
• --start-date-gmt=yyyy:mm:dd:hh:mm:ss: Specify a starting time and date. Uses your system time.
• --start-date-gmt=yyyy:mm:dd:hh:mm:ss: Specify a starting time and date. Time is Greenwich Mean Time.
• --start-date-lat=yyyy:mm:dd:hh:mm:ss: Specify a starting time and date. Uses local aircraft time.

4.4.9 Network Options

• --httpd=port Enable http server on the specified port.
• --enable-network-olk: Enables Oliver Delises’s Multipilot mode.
• --enable-network-olk: Disables Oliver Delises’s Multipilot mode (default).
• --net-hud: HUD displays network info.
• --net-id=name: Specify your own callsign

4.4.10 Route/Waypoint Options

• --wp=ID[@alt]: Allows specifying a waypoint for the GC autopilot; it is possible to specify multiple waypoints (i.e. a route) via multiple instances of this command.
• --flight-plan=[file]: This is more comfortable if you have several waypoints. You can specify a file to read them from.

These options are rather geared to the advanced user who knows what he is doing.

4.4.11 IO Options

• --gamin=params: Open connection using the Garmin GPS protocol.
• --joyclient=params: Open connection to an Agwagon joystick.
• --native-ctrls=params: Open connection using the FG native Controls protocol.
• --native-fdm=params: Open connection using the FG Native FDM protocol.
• --native=params: Open connection using the FG Native protocol.
• --nmea=params: Open connection using the NMEA protocol.
• --opengc=params: Open connection using the OpenGC protocol.
• --props=params: Open connection using the interactive property manager.
• --pve=params: Open connection using the PVE protocol.
• --ray=params: Open connection using the RayWoodworth motion chair protocol.
• --rul=params: Open connection using the RUL protocol.
• --atc610x: Enable atc610x interface.

4.4.12 Debugging options

• --trace-read=params: Trace the reads for a property; multiple instances are allowed.
• --trace-write=params: Trace the writes for a property; multiple instances are allowed.

4.4.13 Joystick properties

All of FlightGear’s joystick (as well as keyboard) properties are written in plain ASCII files, thus anyone can adapt them, if necessary. Fortunately, there is a tool available now, which takes most of the burden form the average user who, maybe, is not that experienced with XML, the language which these files arwe written in.

For configuring your joystick, open a command shell (command prompt(DOS shell under windows, to be found unter Start—All programs—Accessories). Change to the directory /FlightGear/bin via e.g. (modify to your path)

cd c:\FlightGear\bin

and invoke the tool fgjs via

fgjs

on a UNIX/Linux machine, or via

fgjs.exe

on a Windows machine. The program will tell you which joysticks, if any, where detected. Now follow the commands given on screen, i.e. move the axis and press the buttons as required. Be careful, a minor touch already ”counts” as a movement. Check the reports on screen. If you feel something went wrong, just re-start the program

After you are done with all the axis/switches, the directory above will hold a file called fgfsrc.js. If the FlightGear base directory FlighGear does not already contain an options file .fgfsrc (under UNIX)/system.fgfsrc (under Windows) mentioned above, just copy

fgfsrc.js into .fgfsrc (UNIX)/system.fgfsrc (Windows)

and place it into the directory FlightGear base directory FlighGear. In case you already wrote an options file, just open it as well as fgfsrc.js with an editor and copy the entries from fgfsrc.js into .fgfsrc/system.fgfsrc. One hint: The output of fgjs is UNIX formatted. As a result, Windows Editor may not display it the proper way. I suggest getting an editor being able to handle UNIX files as well. My favorite freeware file editor for that purpose, although somewhat dated, is PFE still, to be obtained from

http://www.lancs.ac.uk/people/cpaap/pfe/.

The the axis/button assignment of fgjs should, at least, get the axis assignments right, its output may need some tweaking. There may be axis moving the opposite way the should, the dead zones may be too small etc. For instance, I had to change

--prop:/input/joysticks/js[1]/axis[1]/binding/factor=-1.0

into

--prop:/input/joysticks/js[1]/axis[1]/binding/factor=1.0

(USB CH Flightsim Yoke under Windows XP). Thus, here is a short introduction into the assignments of joystick properties.

Basically, all axes settings are specified via lines having the following structure:

--prop:/input/joysticks/js[n]/axis[m]
/binding/command=property-scale
--prop:/input/joysticks/js[n]/axis[m]
/binding/property=/controls/steering option
--prop:/input/joysticks/js[n]/axis[m]
/binding/dead-band=db --prop:/input/joysticks/js[n]/axis[m]
/binding/offset=os --prop:/input/joysticks/js[n]/axis[m]
/binding/factor=fa

where

You should be able to at least get your joystick working along these lines. Concerning all the finer points, for instance, getting the joystick buttons working, John Check has written a very useful README being included in the base package to be found under FlightGear/Docs/Readme/Joystick.html. In case of any trouble with your input device, it is highly recommended to have a look into this document.