Default head-up display

From FlightGear wiki
Revision as of 18:43, 8 May 2013 by Flughund (Talk | contribs) (altered download link for HeliHUD)

Jump to: navigation, search

The Head-up display (HUD) is an important instrument in modern, mostly military, cockpits. FlightGear provides a XML-based system to relatively easily create HUDs for aircraft such as the F-14 and F-16.

However, this article's focus is on FlightGear's default head-up displays. Those are available for any craft which does not include its own set. Have a look at Further Information if you're planning to create a HUD.

Activate the HUD with the [h]-key. Pressing it repeatedly moves through the configured colours and turns it off again. To change the brightness, press [shift]+[h]. Press [shift]+[i] to go through the available HUD's. Press [i] to switch back to the first one at any time. Have in mind that some aircraft do assign one or more of those keys differently and therefore one or more function/s is/are missing on them.

Some of the head-up display's options can be altered in the menu: View --> Adjust HUD Properties



Control inputs

Monitors the bearing of the control input on the aileron's axis. Attached along the upper side is the indicator for the trim input on that axis.
Properties: /controls/flight/aileron and /controls/flight/aileron-trim
Monitors the bearing of the control input on the elevator's axis. Attached to the left the trim on this axis.
Properties: /controls/flight/elevator and /controls/flight/elevator-trim
Monitors the bearing of the control input on the rudder's axis. Attached to the bottom the trim input.
Properties: /controls/flight/rudder and /controls/flight/rudder-trim
Monitors the throttle input axis.
Property: /controls/engines/engine/throttle


AMSL (Height above mean sea level)
Current altitude relative to sea level in feet (ft) (1 ft = 30.48 cm).
Property: /position/altitude-ft
The g-force appealing to the pilot - to avoid black-/redout.
Property: /accelerations/pilot/z-accel-fps_sec with factor -0.03108095
This is an ideal version of a gyrocompass without the drawbacks of a real one. It shows heading of the aircraft relative to the geographical North Pole (true north) in degree (360 degree scale).
Property: /orientation/heading-deg
KIAS (Knots Indicated Airspeed)
Current speed relating to the ambient air in knot/knots (kt/kts) (1 kt = 1.151 mph = 1.852 km/h).
Property: /velocities/airspeed-kt
Latitude / Longitude
Current location according to the geographic coordinate system.
To change the format of the displayed coordinates, go to Autopilot --> Set Lat/Lon-format.
Properties: /position/latitude-string and /position/longitude-string
Pitch ladder
Displays the aircraft's pitch and roll relative to the ground's level/horizontal in degree. It's used as an artificial horizon (Attitude indicator).
Properties: /orientation/roll-deg and /orientation/pitch-deg
Radio altimeter
Shows current altitude above ground level (AGL) in feet. Relating to the location of the aircraft's radio altimeter, it's not zero if the aircraft is on the ground.
Property: /position/altitude-agl-ft
Turn Coordinator
Properties: /orientation/roll-deg and /orientation/side-slip-deg

HUD autopilot


If the autopilot is active the HUD displays its settings. For each active function (heading, altitude and speed) a box will appear below the gyrocompass containing information on its mode and, if existent, the associated value.

Heading control
Whether it is active or not and on which mode it operates is determined by the content of the /autopilot/locks/heading property.
The values are taken from /autopilot/settings/heading-bug-deg and /autopilot/settings/true-heading-deg.
Altitude control
Active mode: /autopilot/locks/altitude
Their values: /autopilot/settings/target-altitude-ft, /autopilot/settings/vertical-speed-fpm and /autopilot/settings/target-agl-ft.
Speed control
Active mode: /autopilot/locks/speed
Their values: /autopilot/settings/target-speed-kt and /autopilot/settings/target-speed-mach



The upper left hand corner shows the most important information on the actual state of the GPS. Namely these are (line by line):

the mode the GPS operates in and the active waypoint's identifier.
the distance "D" (in nautical miles, nm) and the calculated time to this waypoint "TTW".
the bearing "BRG" to the active waypoint and the course deviation "XTR" based on the leg from the previous waypoint.
the current speed relative to the ground "GS".

Big fat arrow

Remains of a going to be useful instrument.

To get rid of it, remove or comment "runway.xml" from/in $FG_ROOT/Huds/default.xml.
To make it point to the airport selected by menu item "Tower Position", apply patches as shown here.

Further Information

HUDs may be replaced or added by changing or adding their paths in preferences.xml or by setting the paths as command line options. To change the order of the existing ones the options would be: --prop:/sim/hud/path[1]=Huds/minimal.xml --prop:/sim/hud/path[2]=Huds/default.xml

If you consider to create your own HUD have a look at Canvas HUD first.

The basic settings regarding to any HUD are set in $FG_ROOT/preferences.xml. Search the file for the <hud>-tag and you will find a list of properties.

The setup of the default HUD is defined at $FG_ROOT/Huds/default.xml and documentation can be found at $FG_ROOT/Docs/README.hud.

Additional HUDs

Designed to fly helicopters in Helicopter View it is also handy for any craft with a not yet finished cockpit. It also contains a minimalistic HUD only showing some navigational information such as compass and GPS. The download contains instructions and specs.