Describe the function of autopilot in instrument flight.

The function of autopilot in instrument flight is to assist the pilot in controlling the aircraft's flight path based on pre-selected parameters. Essentially, the autopilot system can automatically manage the aircraft's direction, altitude, and speed, allowing the pilot to focus on overall flight management, navigation, and communication. This is especially beneficial in instrument flight, where maintaining an accurate flight path and altitude is crucial, and can reduce workload significantly.

The autopilot system implements commands based on the aircraft’s flight plan and aids in maintaining stability and adherence to the desired course, which include adjustments for wind drift, climbs, and descents. By managing minor corrections and maintaining steady flight, it enhances safety and efficiency.

This function contrasts with the other options, where controlling all flight systems autonomously implies full independence from the pilot, which is not the case for autopilots designed to assist. Using autopilots primarily as a backup system does not capture their main purpose, which is active flight assistance. Lastly, while autopilots can benefit training, their role extends beyond training purposes to operational effectiveness in actual flying scenarios.