Definition
A mechanical lever, pivoted at a single point, with two arms set at an angle to each other. It is used in aircraft control systems to change the direction of a control input — for example, converting linear motion in one direction into linear motion at a different angle, or transferring force around a corner.
Plain English
A bent lever that pivots in the middle and is used to change the direction of a push or pull. When one arm moves, the other arm moves in a different direction.
Context Anchor
Seen in aircraft flight control systems, landing gear systems, and other places where a cable or rod movement must be redirected.
Derivation
Named after the lever once used inside houses to ring a servant's bell from another room. Pulling a cord moved one arm of the lever, which swung the other arm and rang the bell around a corner. The aviation part works the same way — same shape, same idea.
Why Pilots Care
Bellcranks are common wear and inspection points in control systems. A worn or loose bellcrank pivot can cause sloppy or binding controls, which is why they are checked during routine maintenance and preflight inspections of accessible linkages.
Analogy
A bellcrank works like an elbow in a simple mechanical arm: movement comes in from one direction, turns at the joint, and leaves in another direction.
Intuition Check
A bellcrank is not part of a bell, and it is not the engine crankshaft. In aircraft use, it means a pivoting lever that redirects mechanical movement.
Example Sentence 1
The aileron cable runs from the cockpit to a bellcrank in the wing, which redirects the pull to move the control surface.
Example Sentence 2
During inspection the mechanic checked the bellcrank pivot for free movement and signs of wear.