Definition
A shaft or spindle on which a wheel rotates. In aircraft landing gear, the axle is the structural member fixed to the strut or gear leg that supports the wheel and bearings, allowing the wheel to spin freely while carrying the weight of the aircraft.
Plain English
The rod the wheel turns on. It holds the wheel in place and lets it spin.
Context Anchor
Seen during aircraft preflight inspections, landing gear maintenance, and discussions of wheels, tires, and brakes.
Derivation
From Old Norse 'oxull' meaning a shaft or pivot. The original idea was simply 'the thing a wheel turns around,' which is exactly how it is used in aviation today.
Why Pilots Care
A damaged or improperly maintained axle can cause wheel failure, loss of directional control, or a runway excursion during takeoff or landing.
Intuition Check
Do not think of the axle as the entire wheel or the whole landing gear. The axle is the center support that the wheel turns on or around.
Example Sentence 1
The mechanic torqued the axle nut to specification before installing the cotter pin.
Example Sentence 2
Grease the bearings on the axle so the wheels turn smoothly during taxi.