In GA autopilot terminology, a 'position based' autopilot maintains a relationship to what reference?

• A. The aircraft's attitude relative to the horizon
• B. The aircraft's heading relative to north
• C. The horizon
• D. The turn coordinator

Answer: (C)

Position-based autopilot modes use the horizon as the reference point for control. In this approach, the system aims to keep the airplane’s relationship to the horizon constant, effectively maintaining level flight and steady pitch and bank relative to that horizon line. The horizon is the stable external cue pilots use to judge attitude, so tying the autopilot’s control to it means it manages the aircraft’s orientation in space by preserving that horizon reference.

This is different from attitude-based control, which focuses on holding a specific attitude relative to the horizon regardless of the aircraft’s position or track. It’s also distinct from heading-based control, which seeks to maintain a particular magnetic heading, or from a turn-coordinator cue, which is an instrument indicator rather than the reference for a control mode. Therefore, the horizon is the reference that a position-based autopilot maintains.