Definition
A flexible drive belt with evenly spaced teeth (cogs) molded into its inner surface that mesh with matching grooves on toothed pulleys, transmitting power without slipping. Cog belts maintain a fixed timing relationship between the driving and driven pulleys.
Plain English
A rubber belt with teeth on the inside that lock into matching teeth on the pulleys, so the two pulleys always turn together in perfect step without slipping.
Context Anchor
Seen in aircraft engine, accessory-drive, and maintenance discussions, especially when checking how a rotating part is driven.
Derivation
‘Cog’ is an old English word for a tooth on a wheel or gear. A cog belt is literally a belt with cogs (teeth) on it — combining the grip of a gear with the flexibility of a belt.
Why Pilots Care
Maintains exact timing between engine accessories; failure can simultaneously disable ignition, electrical power, and vacuum systems.
Analogy
Think of a bicycle chain: the links lock into the sprocket teeth so the pedals and wheel turn in a fixed relationship. A cog belt does the same job, but with rubber teeth instead of metal links.
Intuition Check
Do not think of a cog belt as just any ordinary belt. The key idea is the teeth: they lock into matching teeth so the belt does not simply rely on friction.
Example Sentence 1
The mechanic inspected the cog belt for cracks and missing teeth during the 100-hour inspection.
Example Sentence 2
A cracked cog belt caused the alternator to stop charging in flight.