Aircraft Autopilot Systems and Functions | Flight Study

Autopilot systems help pilots control aircraft attitude, heading, altitude, and navigation during flight. Understanding how autopilot systems operate improves workload management, situational awareness, and flight safety.

An autopilot is an automatic flight control system that maintains an aircraft in level flight or on a selected course. It may be controlled directly by the pilot or coupled to a radio or GPS navigation signal. Autopilot reduces the physical and mental demands on a pilot and enhances flight safety. Common autopilot functions include heading hold and altitude hold.

The simplest systems use gyroscopic attitude indicators and magnetic compasses to control servos connected to the flight control system. [Figure 1]

Figure 1. Basic autopilot system integrated into the flight control system

The number and location of these servos depend on the complexity of the system. For example, a single-axis autopilot controls the aircraft about the longitudinal axis and a servo actuates the ailerons. A three-axis autopilot controls roll, pitch, and yaw about the aircraft’s three axes.

Three separate servos operate the ailerons, elevator, and rudder. Advanced autopilot systems may be integrated with navigational aids through a flight director system The autopilot system also incorporates a disconnect safety feature. Advanced autopilot systems are coupled to navigational aids through a flight director.

Autopilot systems include disconnect features that allow automatic or manual disengagement. Modern autopilot systems may interface with inertial navigation systems, GPS, and flight computers. In fly-by-wire systems, the autopilot is an integrated component.

Pilots can manually override autopilot inputs whenever necessary. Because autopilot systems vary widely, pilots should always refer to the Aircraft Flight Manual (AFM) or Pilot’s Operating Handbook (POH) for operating procedures.

Frequently Asked Questions

What is the difference between a flight director and an autopilot?

A flight director provides visual cues (command bars) on the flight display to show the pilot where to fly to maintain a selected path, but it does not move the controls. The autopilot physically moves the control surfaces via servos to follow those same commands. An autopilot can be "coupled" to a flight director to fly the cues automatically.

How can a pilot regain manual control from the autopilot?

Pilots can disengage the autopilot using a disconnect switch (usually located on the control yoke), by toggling the autopilot master switch on the console, or by manually overriding the control forces. Most systems also include automatic disconnect features triggered by sensor failures or extreme unusual attitudes.

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