Under what condition should the autothrottle be disengaged?

The autothrottle should be disengaged under the condition of Engine Out Mode being active and rudder boost having failed. This scenario involves critical safety considerations in aircraft operation.

In Engine Out Mode, the aircraft is typically operating with one engine inoperative, requiring careful management of thrust and aerodynamic balance to maintain stability and control. The failure of rudder boost during this time complicates the situation further, as the rudder may not provide the necessary assistance to counteract yawing moments caused by the asymmetric thrust of the operating engine. Disengaging the autothrottle allows the pilot to manually control the thrust to maintain better control over the aircraft's flight path, as this enhances the pilot's ability to make immediate adjustments in response to the unpredictable handling characteristics that could arise from such a failure.

The other conditions listed do not necessitate disengaging the autothrottle in the same critical manner. For instance, when the aircraft is on the ground, it is common practice for the autothrottle to be disengaged, but this is not a specific safety requirement tied to operational conditions. Manual activation of variable thrust during a normal flight is also a standard operational procedure. Finally, achieving cruising altitude typically indicates stable flight where autothrottle could remain engaged to optimize