Most XPlane data is exported in English units, while Mavlink typically uses metric units. MissionPlanner imports the components of velocity (from XPlane data index 21) without a unit conversion:
sitldata.speedN = -DATA[21][5];
sitldata.speedE = DATA[21][3];
sitldata.speedD = -DATA[21][4];
Then later on, it treats them as if they’re in m/s:
hilstate.vx = (short) (sitldata.speedN100); // m/s * 100 - lat
hilstate.vy = (short) (sitldata.speedE100); // m/s * 100 - long
hilstate.vz = (short) (sitldata.speedD*100); // m/s * 100 - + speed down
Is this correct? I would expect a MPH to m/s conversion to be required.