What is the difference between autothrottle and autothrust? | Q & A

The terms "autothrottle" and "autothrust" refer to similar but distinct systems in aircraft that automate the management of engine power. Here’s how they differ:

• System Description: Autothrottle is a system that automatically adjusts the throttle levers to control the engine power settings. It physically moves the throttle levers based on the inputs from the flight control system.
• Typical Usage: Autothrottle is commonly found in Boeing aircraft, though it can be present in other aircraft types as well.
• Operation: The autothrottle adjusts engine power to maintain a desired speed, thrust, or other performance parameters such as climb rate. Pilots can set the desired mode (e.g., speed hold, thrust hold), and the system will move the throttle levers accordingly.
• Physical Feedback: The movement of the throttle levers is visible and tactile, allowing pilots to see and feel the adjustments being made by the system.

• System Description: Autothrust, like autothrottle, is a system that controls engine power automatically, but it does so without moving the throttle levers. Instead, it adjusts the engine’s power electronically.
• Typical Usage: Autothrust is a term typically associated with Airbus aircraft, though it is also used in other aircraft types.
• Operation: In an autothrust system, the throttle levers are placed in a specific detent (such as "CLB" or "TOGA") and remain there. The autothrust system then manages engine thrust to maintain the desired speed or performance parameter without moving the physical throttle levers.
• No Physical Feedback: The throttle levers remain in the set position (detent), and changes in engine power are made electronically, so there is no physical movement of the throttle levers.

• Throttle Lever Movement: In autothrottle systems, the throttle levers move in response to system commands, while in autothrust systems, the levers remain stationary in a detent.
• Aircraft Type: Autothrottle is more commonly used in Boeing aircraft, while autothrust is associated with Airbus aircraft.
• Pilot Interface: Autothrottle provides visible and tactile feedback through throttle lever movement, whereas autothrust relies on electronic control with no movement of the levers.

• Both systems are designed to reduce pilot workload by automatically managing engine power based on the flight mode and conditions.
• Both systems help maintain optimal flight performance and fuel efficiency.

In summary, while both autothrottle and autothrust automate engine power management, the key difference lies in how they control the throttle levers—physically moving them in autothrottle systems versus keeping them stationary in autothrust systems.