Flight director (aviation)
A flight director, short FD, is a " Help" for the pilot of an aircraft, a graphical marker in the attitude indicator and a data source.
The name comes from the English flight Flight Director ( Flight ) and English director ( setpoint generator in technical English), literally so as fly an encoder. He is depicted as a symbol (depending on the type of aircraft ) in the attitude indicator and should help the pilot to maintain course and direction. The Flight Director can serve as an encoder for the autopilot (AP ); if the autopilot is activated, it is based either on the input values (course information, speed settings, etc.) when such values or settings are not available, the autopilot depends on the Flight Director.
If you fly with the Flight Director activated, the symbol stands for the chosen course, if in addition the AP is turned on, it aligns itself with this and followed him on ( if possible ).