What must be satisfactory prior to each flight on which the autopilot is to be used?

The autopilot preflight check is essential prior to each flight where the autopilot will be employed because it ensures that the autopilot system is functioning correctly and safely before the aircraft takes off. This check is designed to verify the integrity and operational status of all autopilot components, including system readiness, response to input commands, and any other parameters that must be confirmed to ensure the safety and reliability of the autopilot during flight.

Performing this check allows pilots to detect any potential issues that could lead to malfunction during flight, thus ensuring a high level of safety. It is critical for pilots to adhere to this procedure consistently, as autopilot failure in-flight can lead to loss of aircraft control.

While checks related to controls, fuel, and navigation setup are indeed important for flight safety, they are not specifically required to confirm the readiness of the autopilot system, which is why the autopilot preflight check is the focus in this context.