On precision ILS approaches with a single engine, what is the minimum autopilot use height?

The correct minimum autopilot use height for precision ILS approaches with a single engine is 110 feet AGL. This limitation is primarily established to ensure safe and effective aircraft control during critical phases of the approach, especially when dealing with reduced thrust and the potential for asymmetric thrust situations in single-engine operations.

At 110 feet AGL, pilots are required to be sufficiently engaged with the aircraft's flight controls to manage any need for go-around or other urgent control inputs, thereby promoting safety and ensuring the aircraft can safely transition to landing. Using the autopilot below this altitude may not allow for timely reactions to any unexpected issues or conditions that may arise during the final approach.

In contrast, lower altitudes like 80 feet AGL do not provide the necessary margin for manual control and decision-making, while higher altitudes, such as 400 feet and 600 feet AGL, may exceed operational requirements for single-engine ILS approaches and could restrict efficient use of autopilot systems designed for this type of approach.