Definition
A pair of gears with cone-shaped teeth used to transmit rotational motion between two shafts whose axes intersect, typically at a right angle. The teeth are cut on the slanted face of each cone so they mesh smoothly as the gears turn.
Plain English
Two gears shaped like cones that mesh together so a turning shaft can drive another shaft pointing in a different direction, usually at 90 degrees.
Context Anchor
Seen in aircraft engine, accessory drive, propeller, and maintenance discussions where rotation must be carried around a corner.
Derivation
From the carpenter's term 'bevel,' meaning a sloped or angled cut. The teeth sit on a slanted surface rather than a flat or cylindrical one, which is what allows the gears to drive each other at an angle.
Why Pilots Care
They carry high torque at right angles in rotor systems; wear or failure can cause loss of rotor drive.
Analogy
Think of two ice cream cones laid tip-to-tip with teeth cut along their sloped sides. Spin one and the other turns, but pointed in a different direction.
Intuition Check
Do not think of bevel gears as just ordinary flat gears. The key idea is that their angled shape lets rotation change direction between shafts.
Example Sentence 1
Bevel gears in the accessory section transfer rotation from the crankshaft to drive the magnetos at a right angle.
Example Sentence 2
During preflight the mechanic checked the oil level in the tail-rotor gearbox that contains the bevel gear set.