autothrust

Autothrust, or autothrottle, is a flight control system that automatically manages engine thrust to maintain a pilot-selected speed or Mach number. It is common on modern airliners and operates in coordination with the autopilot and flight management system to optimize performance, fuel efficiency, and safety by adjusting engine power without constant manual throttle input.

The system receives a target speed from the speed selector or the flight management system and continuously compares it with actual airspeed. Using data from engine sensors and the FADEC (or engine control unit), it computes the required thrust and commands the engines to change thrust reference (N1, EPR, or thrust lever position) accordingly. Autothrust can engage automatically with the autopilot or be manually activated, depending on aircraft design.

Modes typically include maintaining a set speed, climbing or descending with appropriate thrust, or takeoff and go-around settings such as TOGA or CLB. In cruise, autothrust follows the planned speed profile; during approach it adjusts thrust to meet required margins. Some systems remain active during single-engine operations, while others may automatically disengage under fault conditions or at the pilot’s discretion.

Limitations and safety: Autothrust cannot compensate for all external disturbances and requires pilot supervision. It will disengage automatically in certain fault conditions or when the crew manually disables it. Despite automation, pilots monitor thrust and airspeed to ensure safe margins throughout flight. Autothrust typically works in tandem with autopilot and flight management systems to provide coordinated control across flight phases.