FGproperties/velocities/u v wbody-fps

Those are the plane velocity in ECEF (relative to the earth) expressed in the plane body axis:

• /velocities/uBody-fps: velocity projeted along the longitudinal plane axis, positif forward
• /velocities/vBody-fps: along the lateral axis, positif on the right
• /velocities/wBody-fps: along the normal axis, positif is down

Unit: feet per second

Main use

• Sometimes used in wheels animation, uBody-fps is transmitted to mp plane without the need of xml configuration (FG 3.0 +).
• Before FlightGear 3.0, uBody-fps was used in true air speed indicator for YASim plane, this has to be replaced with:

/instrumentation/airspeed-indicator/true-speed-kt

don't forget the unit change!!

• The main reason for the bug fix is that those properties are used in the motionInfo packet, and they should not be relative to the wind, but describe the plane velocity in ECEF.

Conflict - solution

Solved See bug report #202 for the fix.

• YASim was providing the speed relative to the air mass, giving spinning wheels with stopped plane, but accurate TAS.
• JSBSim was ok, giving a false TAS if used.