What is autothrust and how does it interact with the autopilot during takeoff and initial climb?

• A. Autothrust stops when the autopilot engages.
• B. Autothrust controls thrust to reach target speeds while the autopilot manages the flight path; they work together to meet speed and path constraints.
• C. Autothrust and autopilot are independent and do not interact.
• D. Autothrust sets throttle manually.

Answer: (B)

Autothrust is the system that automatically commands engine thrust to achieve and hold a commanded airspeed. During takeoff and the initial climb, it works in concert with the autopilot: the autopilot handles the flight path by commanding pitch and attitude to follow the departure profile, while autothrust manages the thrust to reach and maintain the target speeds.

As you rotate and accelerate, autothrust adjusts engine power to reach the chosen speed (such as the takeoff target speed and any subsequent climb speed). At the same time, the autopilot follows the flight path commands to climb at the desired rate or angle. Because they are coordinated, you get a smooth climb that respects both the speed constraints and the flight-path constraints. Autothrust doesn't automatically stop when the autopilot engages; they remain active together unless you manually disengage one or the other.

So the best answer reflects that autothrust controls thrust to reach target speeds while the autopilot manages the flight path, and they work together to meet both speed and path constraints.