What happens if the autopilot is engaged below 600 feet AGL?

When the autopilot is engaged below 600 feet AGL, it is prohibited except for specific approaches. This limitation is crucial for ensuring safety during critical phases of flight, particularly when the aircraft is close to the ground. Autopilot systems can provide significant benefits during stable and controlled phases of flight, but in the final stages of landing, pilots need to maintain full control of the aircraft to respond effectively to any potential issues.

Specific approaches, such as precision approaches with stable conditions, may allow for autopilot use below 600 feet AGL as they are designed to support the safe operation of the aircraft in that environment. However, in general operations, overriding the autopilot's engagement to maintain manual control promotes alertness and responsiveness when altitude and terrain become critical factors.

The other choices suggest either allowing autopilot engagement at all times, which undermines the importance of pilot-in-command authority during critical flight phases, or prohibiting it entirely without exception, which does not account for the situations where its use is safely governed. Conditions for using autopilot must consider the nature of the approach and the regulatory guidelines, thereby validating the selected answer.