At what minimum height should autothrottle be engaged during landing?

Engaging the autothrottle at 50 feet during landing is considered best practice for several reasons related to safety and optimal performance. At this altitude, the aircraft is typically stabilized on final approach, allowing the autothrottle system to efficiently manage engine thrust as necessary for a smooth landing.

Engaging autothrottle at this height helps ensure that any adjustments to thrust can be made in response to changing conditions, such as wind variations or any deviations from the desired glide path, while the pilot maintains focus on other critical aspects of landing, such as aircraft stability and alignment with the runway.

Furthermore, engaging the autothrottle too early, such as at a lower altitude, may not allow for proper management of throttle inputs given the dynamic nature of landing. Conversely, engaging it too late, nearing the ground, can inhibit the system's ability to make necessary adjustments in time for a safe landing, increasing workload for the pilot at a crucial moment.

Ultimately, the choice of 50 feet balances responsiveness with pilot workload, facilitating a smoother and safer landing sequence.