Modern aircraft have several levels of redundancy and automation, but they most assuredly do not fly themselves. The level of automation is based on workload requirements, aircraft complexity, and the fact that the high-traffic airspace they generally occupy requires continuous precise flight.
The autopilot is one of the most integrated systems of the aircraft. It’s connected to the pitot-static system, the attitude and heading system, global positioning system, ground proximity warning system, and many other aircraft systems related to aircraft control and position. The autopilot integrates all of the information provided by the various systems to calculate and display required attitudes and trim settings for desired flight modes. Servos connected to the flight controls manipulate the attitude of the aircraft.
The flight director displays this data to the pilot. It assists the pilot while he or she is hand-flying the aircraft by showing what the autopilot has calculated to be necessary for the desired aircraft state. There are a few different kinds of flight directors, but they all do the same thing: provide an attitude reference point to achieve the desired flight attitude. There are two different types of commands the flight director will give: vertical and lateral guidance.
For vertical guidance, select a pitch attitude or speed (indicated, Mach, vertical) and the flight director will indicate a command for pitch that would result in the desired speed or pitch attitude. For lateral guidance, select a heading or a navigation source (VOR, GPS, ILS), and the flight director will show a roll command to bring the aircraft to the heading or course desired.
This automation extends to instrument approaches. In some aircraft, coupled approaches can be flown all the way to the ground. In fact, certain ILS approaches with greatly reduced visibility requirements sometimes require the use of autopilot—or at least the assistance of a flight director.
While it’s easy to bring ego into the equation, the autopilot system is no crutch for pilots. It’s a tool that allows better situational awareness, aircraft monitoring, and safer flying. Properly and effectively managing the autopilot is a necessary skill, just like flying an ILS approach, or properly executing a power-off stall.
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