The default autopilot of FlightGear works with the MiG-15bis but only
for heading, pitch and altitude hold. Wing leveler in particular
causes the aircraft to become wild. Enable the following keys:
Ctrl+A: hold current altitude.
Ctrl+H: hold current heading and switch auto-coordination off.
Ctrl+P: hold current pitch.
F11: open the default autopilot dialog; use at your own risk!
