...V ...V Computer Amplifier Reference Servo 5V 28V Computer Amplifier Reference Figure 1. A single-axis autopilot in level flight and in a bank. Servo For ease of understanding, all examples in this series will use DC references. Furthermore, the voltages used in the examples are arbitrary and don't reflect the actual DC voltages used by various systems. Computers/amplifiers The earliest autopilots consisted mostly of amplification. If the airplane deviated from level flight, the reference would produce a voltage, and the amplifier would increase the voltage to a level that would cause a servo to move the control surface. As autopilots became more integrated with navigation systems, engineers added more computing power. Modern autopilots have incredible computing power, but still amplify small error signals into higher voltages. Servos The servo takes electric or electronic signals and converts them to the physical power necessary to move the flight controls. Servos can be pneumatic, hydraulic or electric. Some servos are simple, and some have amplifiers or microprocessors included. Many will generate a feedback signal the computer can use to help make the flight smooth and to confirm the servo is moving the way it should. Pneumatic servos are relatively rare. Hydraulic servos are common on airplanes with hydraulicly boosted controls. Electric servos are the most common and will be used here for examples. Continued on following page avionics news * may 2022 55