In the early days of aviation, aircraft required the continuous attention of a pilot in order to fly safely. As aircraft range increased allowing flights of many hours, the constant attention led to serious fatigue. An autopilot is designed to perform some of the pilot tasks.
The first aircraft autopilot was developed by Sperry Corporation in 1912. The autopilot connected a gyroscopic heading indicator and attitude indicator to hydraulically operated elevators and rudder. (Ailerons were not connected as wing dihedral was counted upon to produce the necessary roll stability.) It permitted the aircraft to fly straight and level on a compass course without a pilot’s attention, greatly reducing the pilot’s workload.
In 1930, the Royal Aircraft Establishment developed an autopilot called a pilots’ assister that used a pneumatically-spun gyroscope to move the flight controls.
A single-axis autopilot controls an aircraft in the roll axis only; such autopilots are also known colloquially as “wing levellers,” reflecting their limitations. A two-axis autopilot controls an aircraft in the pitch axis as well as roll and a three-axis autopilot adds control in the yaw axis.
Most modern General Aviation manufactures these days install Autopilot as standard equipment but there are two types of Autopilots, Attitude based and Rate based
Attitude vs. Rate-based Autopilots
An attitude-based autopilot receives its information directly from the aircraft’s mechanical attitude gyro and as these instruments are generally vacuum driven, an attitude based autopilot can be considered to be “vacuum driven”.
Vacuum pumps are notoriously unreliable thats why with advent of new technology aircraft owners are replacing vacuum instruments with more reliable electronic instruments
Converting from a vacuum driven panel to an electric one is very straight forward and there are plenty of options available to make an attitude based autopilot work with an electric attitude indicator.
Rate-based autopilots gets their attitude information from the an electric turn coordinator, so if the vacuum pump or gyro fails it has no affect on the autopilot’s continued functionality.
The newest generation autopilots like the Garmin GFC 700, S-TEC Digital Autopilot get all of their reference information from the aircraft’s air data, attitude and heading reference system (ADC & AHARS). Fully digital units that provide the highest possible level of reliability.
Any safety conscious pilot, no matter what Autopilot you have fitted in your aircraft you need to understand how it works , how to use it under normal operations and more importantly how to use it when things go wrong.
Learn to operate the GFC 700 Autopilot and Flight Director in your aircraft to enhance your safe and effective flight operations.
We offer both ground and flight training for this amazing Flight Management System
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