Definition
A grooved wheel used to guide and change the direction of a cable, rope, or belt. The groove holds the cable in place as the wheel turns, allowing the cable to move smoothly along a controlled path.
Plain English
A pulley wheel with a groove around its edge. The cable sits in the groove so it stays on the wheel as it moves.
Context Anchor
Seen during inspection or maintenance of cable-operated flight controls, landing gear systems, and other aircraft systems that use moving cables.
Derivation
From Middle English 'shive,' meaning a slice or disc. The grooved wheel looks like a disc with a channel cut around its rim, which is how the name stuck.
Why Pilots Care
Cable-operated flight controls run over sheaves at every change of direction. A worn, seized, or misaligned sheave causes stiff or uneven control feel and can fray the cable. Pilots and mechanics inspect them during routine checks.
Analogy
A sheave is like the small grooved wheel in a window blind or garage door mechanism that lets a cord move around a corner without scraping across a sharp edge.
Intuition Check
Do not confuse sheave with sheaf, which means a bundle of things. In aircraft maintenance, a sheave is a grooved wheel for a cable.
Example Sentence 1
The mechanic inspected each sheave in the aileron control run for wear and proper cable seating.
Example Sentence 2
Binding in a sheave can make the ailerons feel heavy during flight.