HELICOPTER ATTITUDE AND AIRSPEED ACQUISITION AND RETENTION SYSTEM

A helicopter pitch axis autopilot system, including airspeed hold at cruise speeds and pitch attitude hold below cruise speeds, includes integrated longitudinal acceleration drift corrected by heavily filtered Pitot static airspeed as a filtered airspeed reference, use of a beeper to nudge the airspeed reference above cruise speeds or the pitch attitude reference below cruise speeds, resynchronizing of airspeed reference, pitch attitude reference, pitch autopilot integrator and stick trim position reference, momentarily in response to airspeed transitions between cruise and sub-cruise speeds or in response to initiation of beeping, and continuously during trim release. Pilot override without disengagement of the autopilot and ultimate return to a previous speed or attitude is achieved by sensing pilot activity and causing the pitch autopilot integrator value to be held during pilot override, and limiting the value of airspeed error that drives the pitch autopilot integrator once the pilot activity has subsided.