.\" Copyright (C) 2002 Cameron Moore
.\" Copyright (C) 2017 Alessandro Menti
.\"
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.\" modify it under the terms of the GNU General Public License
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.\"
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.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
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.TH FGFS 1 2017-06-25 FlightGear "FlightGear man pages"
.SH NAME
fgfs \- the FlightGear flight simulator
.SH SYNOPSIS
\fBfgfs\fR [\fIoptions...\fR]
.SH DESCRIPTION
.B fgfs
is the main executable for FlightGear, a free, open-source, multi-platform and
sophisticated flight simulator framework for the development and pursuit of
interesting flight simulator ideas.
.SH OPTIONS
Options are first read from the command-line arguments passed to \fBfgfs\fR.
The program then checks for the existence of \fI~/.fgfsrc.\fIhostname\fR (where
.I hostname
is the hostname of the machine) and of \fI~/.fgfsrc\fR; if at least one of
those files exists, it is read and parsed (see the
.BR fgfsrc (5)
man page for the full specifications of the file format).

If conflicting options are given, the ones read last will prevail.

.SS "General options"
.TP
\fB\-\-help\fR, \fB\-h\fR
Display usage information about the most relevant command-line options and
exit.
.TP
\fB\-\-verbose\fR, \fB\-v\fR
When combined with \fB\-\-help\fR/\fB\-h\fR, display usage information about
all command-line options, not just the most relevant ones.
.TP
\fB\-\-version\fR
Display version information about
.B fgfs
and some of the libraries used by the program (SimGear, OpenSceneGraph, PLIB),
then exit.
.TP
\fB\-\-fg\-root=\fIpath\fR
Set the FlightGear data root directory (\fB$FG_ROOT\fR) to \fIpath\fR. If this
option is not set,
.B fgfs
uses the path specified in the
.B FG_ROOT
environment variable or, absent that, the FlightGear data directory chosen at
the time the program was compiled.
.TP
\fB\-\-fg\-scenery=\fIpath\fR
Set the FlightGear scenery directories (\fB$FG_SCENERY\fR) to \fIpath\fR.

You can specify multiple directories by separating them with colons (\fB:\fR),
as in \fI/first/path\fB:\fI/second/path\fR (on Microsoft Windows operating
systems, multiple paths should be separated by semicolons instead): in that
case,
.B fgfs
will follow the order the paths are written in to search for scenery files,
stopping as soon as a match is found.

If this option is not set,
.B fgfs
uses the path specified in the
.B FG_SCENERY
environment variable or, absent that, the
.B Scenery
subdirectory inside \fB$FG_ROOT\fR.
.TP
\fB\-\-fg\-aircraft=\fIpath\fR
Load additional aircraft from \fIpath\fR besides the
.B Aircraft
subdirectory inside \fB$FG_ROOT\fR. Alternatively, you can use
.B \-\-aircraft\-dir
to target a specific aircraft in a given directory.
.TP
\fB\-\-download\-dir=\fIpath\fR
Store aircraft and scenery downloaded via the simulator in \fIpath\fR.

The TerraSync directory may be specifically set with the
.B \-\-terrasync\-dir
option.
.TP
\fB\-\-allow\-nasal\-read=\fIdirs\fR
Allow Nasal aircraft scripts to read files from the directories listed in
\fIdirs\fR (separate multiple paths with colons, or semicolons on Microsoft
Windows operating systems).

By default, Nasal scripts are allowed to read data only from \fB$FG_ROOT\fR
and \fB$FG_HOME\fR, as a security measure.
.TP
\fB\-\-read\-only\fR
Make \fB$FG_HOME\fR (the location where user-specific FlightGear data is
stored) read-only.
.TP
\fB\-\-language=\fIcode\fR
Set the language used by the simulator to \fIcode\fR, where \fIcode\fR is an
ISO 639-1 two-letter locale code (for example, \fBen\fR or \fBit\fR).
.TP
\fB\-\-restore\-defaults\fR
Reset all user settings to their defaults.
.TP
\fB\-\-enable\-save\-on\-exit\fR, \fB\-\-disable\-save\-on\-exit\fR
Save/do not save user settings when the program exits.
.TP
\fB\-\-ignore\-autosave\fR
Ignore the user settings saved the previous time FlightGear was run. This
option implies \fB\-\-disable\-save\-on\-exit\fR.
.TP
\fB\-\-browser\-app=\fIpath\fR
Use the Web browser specified in \fIpath\fR to open aircraft documentation.
.TP
\fB\-\-prop:\fR[\fItype\fB:\fR]\fIname\fB=\fIvalue\fR
Set the property \fIname\fR to \fIvalue\fR. You can optionally specify the
property type by setting \fItype\fR to \fBstring\fR, \fBdouble\fR, \fBfloat\fR,
\fBlong\fR, \fBint\fR or \fBbool\fR.
.TP
\fB\-\-config=\fIpath\fR
Load additional configuration directives from \fIpath\fR. The file should
follow the format described in
.BR fgfsrc (5).
.TP
\fB\-\-no\-default\-config\fR
Do not load any configuration files unless they were explicitly specified with
\fB\-\-config\fR.
.TP
\fB\-\-units\-feet\fR
Use feet as the internal measure unit for distances.
.TP
\fB\-\-units\-meters\fR
Use meters as the internal measure unit for distances.
.TP
\fB\-\-console\fR
Display a console window for simulator/aircraft debugging purposes.

This option is recognized only on Microsoft Windows operating systems; on
other systems, debug messages are always printed to standard output/standard
error.
.TP
\fB\-\-launcher\fR
Start the FlightGear Launcher, a graphical Qt-based interface to the simulator.

This option is available only if FlightGear was compiled with Qt support
enabled.
.TP
\fB\-\-json\-report\fR
Print a report in JSON format on the standard output. The report will give
useful information for debugging purposes, such as the FlightGear version,
the scenery/aircraft paths in use, the TerraSync and the data download
directories and the paths to navigation data files.
.SS Features
.TP
\fB\-\-enable\-panel\fR, \fB\-\-disable\-panel\fR
Enable/disable the pop-up aircraft instrument panel if the chosen airplane has
it.
.TP
\fB\-\-enable\-hud\fR, \fB\-\-disable\-hud\fR
Enable/disable the heads-up display (HUD) if the chosen airplane has it.
.TP
\fB\-\-enable\-anti\-alias\-hud\fR, \fB\-\-disable\-anti\-alias\-hud\fR
Enable/disable heads-up display antialiasing.
.TP
\fB\-\-enable\-hud\-3d\fR, \fB\-\-disable\-hud\-3d\fR
Enable/disable the 3D version of the heads-up display.
.TP
\fB\-\-hud\-tris\fR
Display the number of triangles rendered when painting the heads-up display.
.TP
\fB\-\-hud\-culled\fR
Display the number of triangles culled when painting the heads-up display.
.TP
\fB\-\-enable\-random\-objects\fR, \fB\-\-disable\-random\-objects\fR
Show/hide random scenery objects, such as buildings. Scenery objects increase
realism, but require more resources (memory and graphic card power).
.TP
\fB\-\-enable\-random\-vegetation\fR, \fB\-\-disable\-random\-vegetation\fR
Show/hide random vegetation.
.TP
\fB\-\-enable\-random\-buildings\fR, \fB\-\-disable\-random\-buildings\fR
Show/hide random buildings.
.TP
\fB\-\-enable\-ai\-models\fR, \fB\-\-disable\-ai\-models\fR
Enable/disable the internal AI subsystem, which is required for multiplayer
gaming, AI traffic and many other animations. \fBDisabling the internal AI
subsystem is deprecated.\fR
.TP
\fB\-\-enable\-ai\-traffic\fR, \fB\-\-disable\-ai\-traffic\fR
Enable/disable artificial plane traffic.
.TP
\fB\-\-ai\-scenario=\fIscenario\fR
Add and enable the AI scenario \fIscenario\fR. This option may be repeated
multiple times to enable multiple scenarios.
.TP
\fB\-\-enable\-freeze\fR
Start the simulator in a frozen (paused) state.
.TP
\fB\-\-disable\-freeze\fR
Start the simulator in a running (unpaused) state.
.TP
\fB\-\-enable\-fuel\-freeze\fR
Do not consume any fuel (keep its quantity in the tanks constant).
.TP
\fB\-\-disable\-fuel\-freeze\fR
Consume fuel normally.
.TP
\fB\-\-enable\-clock\-freeze\fR
Do not let the clock advance while running the simulation.
.TP
\fB\-\-disable\-clock\-freeze\fR
Let the clock advance normally.
.TP
\fB\-\-failure=pitot\fR|\fBstatic\fR|\fBvacuum\fR|\fBelectrical\fR
Fail the aircraft pitot, static, vacuum or electrical systems. This option may
be repeated multiple times to fail more than one system.
.TP
\fB\-\-load\-tape=\fItape\fR
Load and replay the flight recorder tape \fItape\fR.
.SS "Audio options"
.TP
\fB\-\-show\-sound\-devices\fR
Show a list of available audio devices and exit.
.TP
\fB\-\-sound\-device=\fIname\fR
Set the sound device to use to \fIname\fR, where
.I name
is the device name shown by the
.B \-\-show\-sound\-devices
option.
.TP
\fB\-\-enable\-sound\fR, \fB\-\-disable\-sound\fR
Enable/disable sound in the simulator.
.SS "Rendering options"
.TP
\fB\-\-terrain\-engine=tilecache\fR|\fBpagedLOD\fR
Choose the terrain engine to use. \fBtilecache\fR is the "traditional" terrain
engine (recommended); \fBpagedLOD\fR is a new, experimental terrain engine
designed to minimize memory usage by loading more detailed versions of scenery
objects on demand.

The \fBpagedLOD\fR engine is available only if FlightGear was compiled with
GDAL support.
.TP
\fB\-\-lod\-levels=\fIlevels\fR
Set the level of detail levels to \fIlevels\fR, where \fIlevels\fR is a
space\-separated list of numeric levels. This option is available only if the
terrain engine in use is \fBpagedLOD\fR.
.TP
\fB\-\-lod\-res=\fIresolution\fR
Set the terrain mesh resolution to \fIresolution\fR. This option is available
only if the terrain engine in use is \fBpagedLOD\fR.
.TP
\fB\-\-lod\-texturing=bluemarble\fR|\fBraster\fR|\fBdebug\fR
Set the terrain texture method. This option is available only if the terrain
engine in use is \fBpagedLOD\fR.
.TP
\fB\-\-lod\-range\-mult=\fImultiplier\fR
Set the range multiplier (the breakpoint from a low to a high level of detail)
to \fImultiplier\fR. This option is available only if the terrain engine in
use is \fBpagedLOD\fR.
.TP
\fB\-\-enable\-rembrandt\fR, \fB\-\-disable\-rembrandt\fR
Enable/disable the
.UR http://\:wiki.flightgear.org/\:Project_Rembrandt
Rembrandt engine
.UE ,
which adds deferred shading (rendering all properties of an object, such as
shading, lighting, fog) in more than one pass.
.TP
\fB\-\-renderer=\fIname\fR
If the Rembrandt engine is enabled, use the rendering pipeline described in
\fI$FG_ROOT/Effects/\fRname\fI.xml\fR.
.TP
\fB\-\-enable\-splash\-screen\fR, \fB\-\-disable\-splash\-screen\fR
Show/hide the simulator splash screen while loading the aircraft/scenery.
.TP
\fB\-\-enable\-mouse\-pointer\fR, \fB\-\-disable\-mouse\-pointer\fR
Force enable display/do not force display the mouse pointer at startup.
.TP
\fB\-\-max\-fps=\fIfrequency\fR
Limit the maximum frame rate of the simulator to \fIfrequency\fR Hz (frames per
second).
.TP
\fB\-\-bpp=\fIdepth\fR
Use a color depth of \fIdepth\fR bits per pixel to display the aircraft and
scenery.
.TP
\fB\-\-fog\-disable\fR, \fB\-\-fog\-fastest\fR, \fB\-\-fog\-nicest\fR
Choose the fog/haze rendering technique.
.B \-\-fog\-disable
will disable fog/haze entirely;
.B \-\-fog\-fastest
will explicitly ask the graphics card driver to choose the most efficient, but
possibly less accurate, fog/haze rendering algorithm;
.B \-\-fog\-nicest
will leave the algorithm choice to the driver, leading to higher quality
results.
.TP
\fB\-\-enable\-enhanced\-lighting\fR, \fB\-\-disable\-enhanced\-lighting\fR
Enable/disable enhanced runway lighting. \fBThis option is deprecated.\fR
.TP
\fB\-\-enable\-distance\-attenuation\fR, \fB\-\-disable\-distance\-attenuation\fR
Enable/disable runway light distance attenuation (the runway lights become
less intense as distance increases).
.TP
\fB\-\-enable\-horizon\-effect\fR, \fB\-\-disable\-horizon\-effect\fR
Enable/disable the celestial body growth illusion near the horizon.
.TP
\fB\-\-enable\-specular\-highlight\fR, \fB\-\-disable\-specular\-highlight\fR
Enable/disable specular reflections on textured objects.
.TP
\fB\-\-fov=\fIdegrees\fR
Set the field of view angle (FOV) to \fIdegrees\fR. High field of view angles
allow you to see a wider part of the world; low angles allow you to "zoom in"
on details.
.TP
\fB\-\-aspect\-ratio\-multiplier=\fIfactor\fR
Set the horizontal and vertical aspect ratio multiplier to \fIfactor\fR.
.TP
\fB\-\-enable\-fullscreen\fR, \fB\-\-disable\-fullscreen\fR
Enable/disable fullscreen mode.
.TP
\fB\-\-shading\-flat\fR, \fB\-\-shading\-smooth\fR
Use flat/smooth shading. If flat shading is active, the simulator uses the same
color to paint the face of an object: this is faster, but makes edges more
pronounced. Smooth shading smooths color changes between vertices, leading to
higher-quality results, at an expense in performance.
.TP
\fB\-\-materials\-file=\fIfile\fR
Load the definitions of the materials used to render the scenery from
\fIfile\fR. By default, materials are loaded from
\fI$FG_ROOT/regions/materials.xml\fR.
.TP
\fB\-\-texture\-filtering=\fIvalue\fR
Set the anisotropic texture filtering to \fIvalue\fR. The acceptable values are
\fB1\fR (default), \fB2\fR, \fB4\fR, \fB8\fR or \fB16\fR.
.TP
\fB\-\-enable\-wireframe\fR, \fB\-\-disable\-wireframe\fR
Enable/disable the wireframe drawing mode (in which only object edges are
painted).
.TP
\fB\-\-geometry=\fIwidth\fBx\fIheight\fR
Set the window geometry (size) to \fIwidth\fBx\fIheight\fR (both \fIwidth\fR
and \fIheight\fR are in pixels).
.TP
\fB\-\-view\-offset=LEFT\fR|\fBRIGHT\fR|\fBCENTER\fR|\fIvalue\fR
Specify the default forward view direction as an offset from straight ahead.
The allowed values are \fBLEFT\fR (-90°), \fBRIGHT\fR (90°), \fBCENTER\fR (0°)
or a specific number in degrees.
.SS "Aircraft options"
.TP
\fB\-\-aircraft=\fIname\fR, \fB\-\-vehicle=\fIname\fR
Load an aircraft/vehicle from a set file named \fRname\fI\-set.xml\fR. The file
is searched for in \fI$FG_ROOT/Aircraft\fR, in the directory pointed to by the
environment variable \fBFG_AIRCRAFT\fR and in the directories passed to
.BR fgfs (1)
using the \fB\-\-fg\-aircraft\fR option.
.TP
\fB\-\-aircraft\-dir=\fIpath\fR
Explicitly specify the directory in which the \fB\-set.xml\fR file should be
searched for. If this argument is used, the path cache stored in
\fI~/.fgfs/autosave_X_Y.xml\fR, the directories passed with the
\fB\-\-fg\-aircraft\fR option and the directory specified in the
\fBFG_AIRCRAFT\fR environment variable are not taken into account.
.TP
\fB\-\-show\-aircraft\fR
Print a list of available aircraft and exit.
.TP
\fB\-\-min\-status=alpha\fR|\fBbeta\fR|\fBearly-production\fR|\fBproduction\fR
Do not list aircraft having a status level (development status) lower than the
one specified. See
.UR http://\:wiki.flightgear.org/\:Aircraft_rating_system
the FlightGear wiki "Aircraft rating system" page
.UE
for an extended description of aircraft ratings.
.TP
\fB\-\-fdm=jsb\fR|\fBlarcsim\fR|\fByasim\fR|\fBmagic\fR|\fBballoon\fR|\fBada\fR|\fBexternal\fR|\fBnull\fR
Select the core flight dynamics model to use among the following ones:
.RS 7
.IP \(bu 3
\fBjsb\fR: the
.UR http://\:www.jsbsim.org/
JSBSim flight dynamics model
.UE ,
which takes a data\-driven approach to modeling: given the performance data for
an aircraft (mass and balance, ground reactions, propulsions, aerodynamics...),
it assembles it together to produce the global aircraft dynamics;
.IP \(bu 3
\fBlarcsim\fR: the
.UR http://\:www.jsbsim.org/
LaRCsim flight dynamics model
.UE ,
the original model used in FlightGear up to 2000, developed at NASA, now
inactive;
.IP \(bu 3
\fByasim\fR: the
.UR http://\:wiki.flightgear.org/\:YASim
YASim flight dynamics model
.UE ,
which, given the physical and flying characteristics of an aircraft, attempts
to solve for them;
.IP \(bu 3
\fBmagic\fR: the "Magic Carpet" flight model;
.IP \(bu 3
\fBballoon\fR: a hot air balloon simulation;
.IP \(bu 3
\fBada\fR: an externally-driven flight dynamics model designed by the
Aeronautical Development Agency of Bangalore, India;
.IP \(bu 3
\fBexternal\fR/\fBnull\fR: use an external flight dynamics model (the
\fBexternal\fR option has the same meaning as \fBnull\fR and is maintained for
backward compatibility purposes).
.RE
.TP
\fB\-\-aero=\fIname\fR
Load the aircraft aerodynamics model from the file \fRname\fI.xml\fR in the
aircraft directory.
.TP
\fB\-\-model\-hz=\fIn\fR
Run the flight dynamics model at a frequency of \fIn\fR Hz (\fIn\fR times per
second).
.TP
\fB\-\-speed=\fIn\fR
Run the flight dynamics model \fIn\fR times faster than real time.
.TP
\fB\-\-trim\fR, \fB\-\-notrim\fR
Trim/do not attempt to trim the model. This option is only valid if the flight
dynamics module in use is JSBSim.
.TP
\fB\-\-on\-ground\fR
Start the aircraft on the ground. This is the default option.
.TP
\fB\-\-in\-air\fR
Start the aircraft in the air. This option is implied if \fB\-\-altitude\fR
is specified.
.TP
\fB\-\-enable\-auto\-coordination\fR, \fB\-\-disable\-auto\-coordination\fR
Enable/disable auto coordination (joint control of rudder and ailerons).
.TP
\fB\-\-livery=\fIname\fR
Load the aircraft livery from a file named \fIname\fR.
.TP
\fB\-\-state=\fIvalue\fR
Set the initial aircraft state to \fIvalue\fR. The states that can be used are
aircraft\-dependent.
.SS "Time options"
.TP
\fB\-\-timeofday=real\fR|\fBdawn\fR|\fBmorning\fR|\fBnoon\fR|\fBafternoon\fR|\fBdusk\fR|\fBevening\fR|\fBmidnight\fR
Start the simulator at the specified time of day:
.RS 7
.IP \(bu 3
\fBreal\fR: real clock time;
.IP \(bu 3
\fBdawn\fR: the time when the Sun is 90° E on the horizon;
.IP \(bu 3
\fBmorning\fR: the time when the Sun is 75° E on the horizon;
.IP \(bu 3
\fBnoon\fR: the time when the Sun is 0° on the horizon;
.IP \(bu 3
\fBafternoon\fR: the time when the Sun is 75° W on the horizon;
.IP \(bu 3
\fBdusk\fR: the time when the Sun is 90° W on the horizon;
.IP \(bu 3
\fBevening\fR: the time when the Sun is 100° W on the horizon;
.IP \(bu 3
\fBmidnight\fR: the time when the Sun is 180° on the horizon.
.RE
.TP
\fB\-\-season=summer\fR|\fBwinter\fR
Load summer/winter textures.
.TP
\fB\-\-time\-offset=\fR[\fB+\fR|\fB-\fR]\fIhh\fB:\fImm\fB:\fIss\fR
Add a time offset to the startup time specified with the \fB\-\-timeofday\fR
option.
.TP
\fB\-\-time\-match\-real\fR
Synchronize the simulator time with real world GMT time.
.TP
\fB\-\-time\-match\-local\fR
Synchronize the simulator time with real world local time.
.TP
\fB\-\-start\-date\-sys=\fIyyyy\fB:\fImm\fB:\fIdd\fB:\fIhh\fB:\fImm\fB:\fIss\fR
Specify the simulator starting date and time with respect to the local timezone
of the system.
.TP
\fB\-\-start\-date\-gmt=\fIyyyy\fB:\fImm\fB:\fIdd\fB:\fIhh\fB:\fImm\fB:\fIss\fR
Specify the simulator starting date and time with respect to the Greenwich Mean
Time.
.TP
\fB\-\-start\-date\-lat=\fIyyyy\fB:\fImm\fB:\fIdd\fB:\fIhh\fB:\fImm\fB:\fIss\fR
Specify the simulator starting date and time with respect to the timezone of
the starting airport.
.SS "Initial position and orientation"
.TP
\fB\-\-airport=\fIID\fR
Start the simulator at the airport having \fIID\fR as its ICAO code.
.TP
\fB\-\-parking\-id=\fIname\fR
Place the aircraft at the parking position \fIname\fR. This option requires the
\fB\-\-airport\fR option to be present.
.TP
\fB\-\-runway=\fInumber\fR
Place the aircraft on runway \fInumber\fR. This option requires the
\fB\-\-airport\fR option to be present.
.TP
\fB\-\-carrier=\fIname\fR|\fIID\fR
Place the aircraft on the AI carrier named \fIname\fR/having the ID \fIID\fR.
.TP
\fB\-\-parkpos=\fIname\fR
Place the aircraft at the starting position \fIname\fR. This option requires
the \fB\-\-carrier\fR option to be present.
.TP
\fB\-\-vor=\fIID\fR
Place the aircraft over the VOR \fIID\fR.
.TP
\fB\-\-vor\-frequency=\fIfrequency\fR
Set the frequency of the VOR to \fIfrequency\fR. This option requires the
\fB\-\-vor\fR option to be present.
.TP
\fB\-\-ndb=\fIID\fR
Place the aircraft over the NDB \fIID\fR.
.TP
\fB\-\-ndb\-frequency=\fIfrequency\fR
Set the frequency of the NDB to \fIfrequency\fR. This option requires the
\fB\-\-ndb\fR option to be present.
.TP
\fB\-\-fix=\fIID\fR
Place the aircraft over the fix \fIID\fR.
.TP
\fB\-\-offset\-distance=\fInm\fR
Place the aircraft \fInm\fR statute miles away from the reference point
specified by the previous options.
.TP
\fB\-\-offset\-azimuth=\fIdegrees\fR
Place the aircraft at a heading of \fIdegrees\fR degrees with respect to the
reference point specified by the previous options.
.TP
\fB\-\-lon=\fIdegrees\fR, \fB\-\-lat=\fIdegrees\fR
Place the aircraft at the point with the coordinates (\fIlat\fR, \fIlon\fR).
Northern longitudes/eastern latitudes must be positive; southern
longitudes/western latitudes must be negative.
.TP
\fB\-\-altitude=\fIvalue\fR
Place the aircraft at an altitude of \fIvalue\fR feet (meters if the
\fB\-\-units\-meters\fR option was specified).
.TP
\fB\-\-heading=\fIdegrees\fR
Specify the initial heading (yaw) angle (psi) of the aircraft.
.TP
\fB\-\-roll=\fIdegrees\fR
Specify the initial roll angle (phi) of the aircraft.
.TP
\fB\-\-pitch=\fIdegrees\fR
Specify the initial pitch angle (theta) of the aircraft.
.TP
\fB\-\-uBody=\fIunits_per_sec\fR
Specify the initial velocity along the body X axis.
.TP
\fB\-\-vBody=\fIunits_per_sec\fR
Specify the initial velocity along the body Y axis.
.TP
\fB\-\-wBody=\fIunits_per_sec\fR
Specify the initial velocity along the body Z axis.
.TP
\fB\-\-vNorth=\fIunits_per_sec\fR
Specify the initial velocity along the body North-South axis.
.TP
\fB\-\-vEast=\fIunits_per_sec\fR
Specify the initial velocity along the body West-East axis.
.TP
\fB\-\-vDown=\fIunits_per_sec\fR
Specify the initial velocity along the body vertical axis.
.TP
\fB\-\-vc=\fIknots\fR
Set the initial airspeed of the aircraft to \fIknots\fR knots.
.TP
\fB\-\-mach=\fInumber\fR
Set the initial airspeed of the aircraft to Mach \fInumber\fR.
.TP
\fB\-\-glideslope=\fIdegrees\fR
Set the flight path angle to \fIdegrees\fR degrees. The value can be positive.
.TP
\fB\-\-roc=\fIfpm\fR
Set the initial rate of climb to \fIfpm\fR feet per minute. The value can be
negative.
.SS "Route/waypoint options"
.TP
\fB\-\-wp=\fIID\fR[\fB@\fIalt\fR]
Enter the waypoint (VOR, NDB, fix) \fIID\fR into the autopilot. The optional
part \fB@\fIalt\fR can be used to specify the altitude at which \fIID\fR
should be crossed.
.TP
\fB\-\-flight\-plan=\fIfile\fR
Read a flight plan from \fIfile\fR.
.SS "Avionics options"
.TP
\fB\-\-com1=\fIfrequency\fR
Set the COM1 frequency to \fIfrequency\fR MHz.
.TP
\fB\-\-com2=\fIfrequency\fR
Set the COM2 frequency to \fIfrequency\fR MHz.
.TP
\fB\-\-nav1=\fR[\fIradial\fB:\fR]\fIfrequency\fR
Set the NAV1 frequency to \fIfrequency\fR MHz. You can optionally specify a
radial by prefixing the frequency with the heading and a colon.
.TP
\fB\-\-nav2=\fR[\fIradial\fB:\fR]\fIfrequency\fR
Set the NAV2 frequency to \fIfrequency\fR MHz. You can optionally specify a
radial by prefixing the frequency with the heading and a colon.
.TP
\fB\-\-adf1=\fR[\fIrotation\fB:\fR]\fIfrequency\fR, \fB\-\-adf=\fR[\fIrotation\fB:\fR]\fIfrequency\fR
Set the ADF1 frequency to \fIfrequency\fR kHz. You can optionally specify the
rotation angle of its compass card by prefixing the frequency with the angle and
a colon. \fBThe \-\-adf option is deprecated.\fR
.TP
\fB\-\-adf2=\fR[\fIrotation\fB:\fR]\fIfrequency\fR
Set the ADF2 frequency to \fIfrequency\fR kHz. You can optionally specify the
rotation angle of its compass card by prefixing the frequency with the angle and
a colon.
.TP
\fB\-\-dme=nav1\fR|\fBnav2\fR|\fIfrequency\fR
Slave the automatic direction finder to the NAV1/NAV2 radio or set its internal
frequency to \fIfrequency\fR.
.SS "Environment options"
.TP
\fB\-\-metar=\fIMETAR\fR
Simulate the weather conditions described by the METAR string \fIMETAR\fR. This
option implies \fB\-\-disable\-real\-weather\-fetch\fR.
.TP
\fB\-\-enable\-real\-weather\-fetch\fR, \fB\-\-disable\-real\-weather\-fetch\fR
Enable/disable METAR-based real weather fetching. This feature requires an
active Internet connection.
.TP
\fB\-\-enable\-clouds\fR, \fB\-\-disable\-clouds\fR
Enable/disable 2D (flat) cloud layers.
.TP
\fB\-\-enable\-clouds3d\fR, \fB\-\-disable\-clouds3d\fR
Enable/disable 3D (volumetric) cloud layers.
.TP
\fB\-\-visibility=\fImeters\fR
Set the initial visibility to \fImeters\fR meters.
.TP
\fB\-\-visibility\-miles=\fImiles\fR
Set the initial visibility to \fImiles\fR miles.
.TP
\fB\-\-wind=\fIdir\fR[\fB:\fImaxdir\fR]\fB@\fIspeed\fR[\fB:\fIgust\fR]
Specify the direction the wind blows from (\fIdir\fR) and its speed (\fIspeed\fR
knots). If the wind is not meant to blow from a fixed direction, but rather
from a range of directions, specify the range as \fIdir\fB:\fImaxdir\fR, where
\fIdir\fR and \fImaxdir\fR are the minimum and maximum angles in degrees. If
you want the simulator to model wind gusts as well, set \fIgust\fR to their
maximum intensity in knots.
.TP
\fB\-\-random\-wind\fR
Randomize the direction and speed of the wind.
.TP
\fB\-\-turbulence=\fIintensity\fR
Set the turbulence intensity to \fIintensity\fR. The intensity can range from
\fB0.0\fR (calm) to \fB1.0\fR (severe).
.TP
\fB\-\-ceiling=\fIft_asl\fR[\fB:\fIthickness_ft\fR]
Create an overcast ceiling at a height of \fIft_asl\fR feet above the mean sea
level. You can optionally specify a thickness by appending a colon (\fB:\fR)
and the desired thickness in feet; if you omit it, the simulator will default
to 2000 ft.
.SS "Network options"
.TP
\fB\-\-callsign=\fIvalue\fR
Set the multiplayer callsign to \fIvalue\fR. The callsign must be at most ten
characters long and must contain only numbers, letters of the English alphabet,
dashes (\fB\-\fR) and underscores (\fB_\fR); longer callsigns are truncated,
and characters not matching those listed above are replaced with dashes.
.TP
\fB\-\-multiplay=\fR{\fBin\fR|\fBout\fR}\fB,\fIhz\fB,\fIaddress\fB,\fIport\fR
Specify the multiplayer communication settings.

The first field specifies whether the settings apply to inbound (\fBin\fR) or
outbound (\fBout\fR) communications. The second field (\fIhz\fR) specifies the
frequency (in Hz, times per second) at which data should be sent. The third
field (\fIaddress\fR) must be set to the IP address of the network interface
that FlightGear should use to send/receive data, or left blank to let the
simulator use all available interfaces. The fourth field (\fIport\fR) should be
set to the port to use (usually \fB5000\fR).
.TP
\fB\-\-proxy=\fR[\fIusername\fB:\fIpassword\fB@\fR]\fIhost\fB:\fIport\fR
Specify the proxy server and port to use. The username and password are
optional; if they are present, they should be given as MD5 hashes.

This option is only useful if \fB\-\-real\-weather\-fetch\fR is enabled.
.TP
\fB\-\-httpd=\fR[\fIaddress\fB:\fR]\fIport\fR
Enable the Phi interface (HTTP server) on the specified address and port. The
address is optional.
.TP
\fB\-\-telnet=\fIport\fR
Enable the Telnet interface on the specified port.
.TP
\fB\-\-jpg\-httpd=\fIport\fR
Enable the screenshot HTTP server interface on the specified port. \fBThis
option is deprecated: use the Phi interface instead.\fR
.TP
\fB\-\-enable\-terrasync\fR, \fB\-\-disable\-terrasync\fR
Enable/disable automatic scenery/object downloads.
.TP
\fB\-\-terrasync\-dir=\fIdirectory\fR
Set the directory where the downloaded scenery will be stored to
\fIdirectory\fR.
.TP
\fB\-\-enable\-fgcom\fR, \fB\-\-disable\-fgcom\fR
Enable/disable the FGCom (voice ATC) integration.
.SS "I/O options"
.TP
\fB\-\-generic=\fIparams\fR, \fB\-\-atlas=\fIparams\fR, \fB\-\-atcsim=\fIparams\fR, \fB\-\-AV400=\fIparams\fR, \fB\-\-AV400Sim=\fIparams\fR, \fB\-\-AV400WSimA=\fIparams\fR, \fB\-\-AV400WSimB=\fIparams\fR, \fB\-\-garmin=\fIparams\fR, \fB\-\-hla=\fIparams\fR, \fB\-\-hla\-local=\fIparams\fR, \fB\-\-igc=\fIparams\fR, \fB\-\-joyclient=\fIparams\fR, \fB\-\-jsclient=\fIparams\fR, \fB\-\-native\-ctrls=\fIparams\fR, \fB\-\-native\-gui=\fIparams\fR, \fB\-\-native\-fdm=\fIparams\fR, \fB\-\-native=\fIparams\fR, \fB\-\-nmea=\fIparams\fR, \fB\-\-opengc=\fIparams\fR, \fB\-\-props=\fIparams\fR, \fB\-\-pve=\fIparams\fR, \fB\-\-ray=\fIparams\fR, \fB\-\-rul=\fIparams\fR
Open a connection to drive external programs or hardware.

Specify the protocol by using the correct command\-line option:
.RS 7
.IP \(bu 3
\fBgeneric\fR: a predefined communication interface and a preselected
communication protocol;
.IP \(bu 3
\fBatlas\fR: the Atlas protocol;
.IP \(bu 3
\fBatcsim\fR: the ATCsim (atc610x) protocol;
.IP \(bu 3
\fBAV400\fR: the Garmin AV400 protocol, required to drive a Garmin 196/296
series GPS;
.IP \(bu 3
\fBAV400Sim\fR: the set of AV400 strings required to drive a Garmin 400-series
GPS;
.IP \(bu 3
\fBAV400WSimA\fR, \fBAV400WSimB\fR: the set of strings required to drive a
Garmin WAAS GPS (where the \fBA\fR channel uses a variant of the AVSim400
protocol and the \fBB\fR channel communicates with the GPS unit);
.IP \(bu 3
\fBgarmin\fR: the Garmin GPS protocol;
.IP \(bu 3
\fBhla\fR, \fBhla\-local\fR: the HLA protocol, either remote or local;
.IP \(bu 3
\fBigc\fR: the International Glider Commission protocol;
.IP \(bu 3
\fBjoyclient\fR: the protocol used by Agwagon joysticks;
.IP \(bu 3
\fBnative\-ctrls\fR: the FlightGear Native Controls protocol;
.IP \(bu 3
\fBnative\-gui\fR: the FlightGear Native GUI protocol;
.IP \(bu 3
\fBnative\-fdm\fR: the FlightGear Native FDM protocol;
.IP \(bu 3
\fBnative\fR: the FlightGear Native protocol;
.IP \(bu 3
\fBnmea\fR: the NMEA protocol (used to drive most GPS units);
.IP \(bu 3
\fBopengc\fR: the protocol used by OpenGC, a software used to render
high\-quality glass cockpit displays for simulated flightdecks;
.IP \(bu 3
\fBprops\fR: the interactive property manager protocol;
.IP \(bu 3
\fBpve\fR: the PVE protocol;
.IP \(bu 3
\fBray\fR: the Ray Woodworth motion chair protocol;
.IP \(bu 3
\fBrul\fR: the RUL protocol.
.RE

.RS 7
The parameters (\fIparams\fR) must be in the form
\fImedium\fB,\fIdirection\fB,\fIhz\fB,\fImedium_options\fR where \fImedium\fR
is the medium used by the protocol (\fBserial\fR, \fBsocket\fR, \fBfile\fR...),
\fIdirection\fR is the communication direction (\fBin\fR, \fBout\fR or
\fBbi\fR), \fIhz\fR is the frequency the channel should be processed at
(floating point values are accepted) and \fImedium_options\fR are:
.RE

.RS 7
.IP \(bu 3
for serial protocols, \fIdevice\fB,\fIbaud\fR, where \fIdevice\fR is the device
name to be opened and \fIbaud\fR is the communication baud rate;
.IP \(bu 3
for socket protocols, \fImachine\fB,\fIport\fB,\fIstyle\fR, where \fImachine\fR
is the machine name or the IP address of the server (if the simulator should
act as a client) or is left empty (if the simulator should act as a server),
\fIport\fR is the port to use (or is left empty to ask the operating system to
choose an available port) and \fIstyle\fR is \fBtcp\fR or \fBudp\fR;
.IP \(bu 3
for file protocols, \fIfilename\fR, where \fIfilename\fR is the name of the
file data should be written to.
.RE
.SS "Debugging options"
.TP
\fB\-\-enable\-fpe\fR
Abort when a floating\-point exception is encountered.
.TP
\fB\-\-fgviewer\fR
View the scenery and the aircraft in a simple model viewer, without loading the
entire simulator.
.TP
\fB\-\-log\-level=bulk\fR|\fBdebug\fR|\fBinfo\fR|\fBwarn\fR|\fBalert\fR
Set the minimum logging level. Log messages having a severity greater than or
equal to the specified value are recorded; the others are discarded.
.TP
\fB\-\-log\-class=all\fR|\fBnone\fR|\fBai\fR|\fBenvironment\fR|\fBflight\fR|\fBgeneral\fR|\fBio\fR|\fBnetwork\fR|\fBsound\fR|\fBterrain\fR|...
Log only events belonging to the specified log classes (\fBall\fR logs all
events, \fBnone\fR logs none). Multiple classes can be specified by separating
them with commas or pipes, for example: \fB\-\-log\-class=ai,flight\fR.
.TP
\fB\-\-log\-dir=\fIdir\fR
Save the logs in the directory \fIdir\fR. If \fIdir\fR is \fBdesktop\fR, the
logs are saved on the Desktop. This option may be given several times, using a
different directory each time. Inside the specified directory, the log file
will be named \fIFlightGear_\fRYYYY\fI-\fRMM\fI-\fRDD\fI_\fRnum\fI.log\fR,
where \fIYYYY-MM-DD\fR is the current date and \fInum\fR is a progressive
number starting at \fB0\fR.
.TP
\fB\-\-trace\-read=\fIproperty\fR, \fB\-\-trace\-write=\fIproperty\fR
Trace the reads/writes for a property (print a log message whenever
\fIproperty\fR is read from/written to).
.TP
\fB\-\-developer\fR
Enable developer mode.
.SH "EXIT STATUS"
.B fgfs
exits with
.B 0
if the execution completes successfully, or with another status (usually
.B 1
or \fB-1\fR) if an error occurred.
.SH ENVIRONMENT
.IP "\fBCOMPUTERNAME\fR" 4
Specifies the hostname of the system in use. This environment variable is only
taken into account on Microsoft Windows operating systems.
.IP "\fBFG_AIRCRAFT\fR" 4
Specifies the path in which aircraft should be searched for.
.IP "\fBFG_LAUNCHER\fR" 4
If this environment variable is set and is not \fB0\fR, the Qt launcher will be
shown. The variable is mainly used on Mac OS X operating systems to avoid the
use of wrapper scripts.
.IP "\fBFG_ROOT\fR" 4
Specifies the root data directory to use.
.IP "\fBFG_SCENERY\fR" 4
Specifies the scenery directory to use.
.IP "\fBHTTP_PROXY\fR" 4
Specifies the HTTP proxy to use. Must be in the form \fBhttp://host:port/\fR.
.IP "\fBLANG\fR" 4
Specifies the language to use.
.SH FILES
.IP "\fI~/.fgfs\fR" 4
The main directory where FlightGear configuration files and data (downloaded
aircraft/scenery) are stored.
.IP "\fI~/.fgfsrc.hostname\fR, \fI~/.fgfsrc\fR" 4
Configuration files containing command-line options for
.BR fgfs (1).