Which of the following has the primary function of automating the air vehicle's flight control?

The primary function of automating the air vehicle's flight control is attributed to the flight control computer. This system is essential for ensuring that the unmanned aircraft operates smoothly and efficiently by processing input from various sensors and making the necessary adjustments to the flight controls in real time. It manages the aircraft's attitude, altitude, speed, and direction, allowing for stable flight and adherence to programmed flight paths.

While the navigation system is important for determining the aircraft's position and guiding its route, it does not directly control the flight mechanics. The payload system is related to the equipment or cargo the UAS carries, which could include cameras or sensors, and is not involved in flight control. The communication system is crucial for transmitting data and receiving commands between the ground control station and the aircraft, but its role does not extend to automating flight control. Thus, the flight control computer is specifically designed for managing and automating the aircraft's flight operations, making it the correct choice.