Definition
In a helicopter equipped with an autopilot or stability augmentation system, the cyclic servo is the electromechanical actuator that moves the cyclic control flight controls on behalf of the autopilot. It receives commands from the autopilot computer and applies inputs to the cyclic linkage to control the helicopter's pitch and roll attitude. If a cyclic servo fails or runs away, the pilot must immediately override or disconnect it and revert to manual control of the cyclic.
Plain English
A small motor in the helicopter's control system that moves the cyclic stick for the autopilot. When the autopilot decides the helicopter needs to pitch or bank, the cyclic servo is the device that physically pushes the controls to do it.
Context Anchor
Seen in helicopter systems and emergency procedures, especially when discussing servo or hydraulic assist failures during instrument flight.
Derivation
Cyclic' refers to the helicopter's cyclic control, which tilts the rotor disc to move the aircraft forward, back, or sideways. 'Servo' comes from the Latin 'servus' meaning servant -- a device that does work on command. So a cyclic servo is literally a 'servant' that operates the cyclic control on the autopilot's behalf.
Why Pilots Care
Failure removes automated attitude control, forcing the pilot to fly manually in instrument conditions where precise attitude management is critical.
Analogy
It is similar to power steering in a car: the driver still gives the command, but the assist unit supplies much of the force needed to make the movement.
Intuition Check
Cyclic does not just mean “repeating” here. In this term, it refers to the helicopter control that tilts the rotor disc to steer the aircraft.
Example Sentence 1
When the cyclic servo malfunctioned, the pilot disengaged the autopilot and flew the helicopter manually for the rest of the approach.
Example Sentence 2
After landing, maintenance inspected the cyclic servo because the autopilot had disengaged without warning during cruise.