Definition
Toothed mechanical components inside an engine accessory section that transmit rotational motion from the crankshaft to engine accessories such as magnetos, oil pumps, fuel pumps, and tachometer drives. During preflight, drive gears are inspected indirectly by checking for evidence of metal particles in the oil screen or filter, which can indicate gear wear or failure inside the engine.
Plain English
The toothed wheels inside the engine that turn other engine parts, like the magnetos and pumps, by spinning off the crankshaft. You can't see them during preflight, but signs of wear can show up as metal flakes in the oil filter.
Context Anchor
Seen during preflight when checking mechanical areas such as landing gear mechanisms or other moving aircraft components.
Derivation
Drive' comes from the Old English drīfan, meaning to push or move forward. A 'drive gear' is the gear that moves another gear — it provides the power, while the gear it turns is the 'driven gear.'
Why Pilots Care
Wear, damage, or loss of lubrication in the drive gears can cause propeller RPM loss, failure of engine accessories, or sudden engine stoppage, all of which directly threaten flight safety.
Analogy
Drive gears work like the gears on a bicycle or in a hand-crank tool: one turning part makes another part turn or move.
Intuition Check
Do not read “drive” here as driving a vehicle. In this term, “drive” means to make another mechanical part move.
Example Sentence 1
During preflight, the pilot checked the oil filter for metal shavings that might indicate worn drive gears inside the engine.
Example Sentence 2
The constant-speed propeller depends on intact drive gears to maintain selected RPM throughout the flight.