Definition
In a gear train, the gear that receives power from the input shaft and transmits it to one or more other gears. The drive gear is the source of motion in the system; the gear it turns is called the driven gear.
Plain English
The gear that does the pushing. It turns first and makes the next gear move.
Context Anchor
Seen in aircraft engine, accessory, starter, and maintenance discussions where one rotating part turns another.
Derivation
“Drive” comes from an old word meaning to push or make something move. “Gear” came to mean a mechanical part used to transmit motion. Together, “drive gear” points to the gear that makes the next part move.
Why Pilots Care
Knowing which gear is the drive gear and which is the driven gear matters when reading engine diagrams, troubleshooting accessory failures, or understanding how engine RPM is converted to propeller RPM through a reduction gear system.
Intuition Check
Do not read “gear” here as landing gear. In this term, a gear is a toothed wheel inside a mechanical system, and the drive gear is the one supplying the motion.
Example Sentence 1
The crankshaft turns the drive gear, which in turn rotates the magneto drive shaft.
Example Sentence 2
During overhaul the mechanic inspects the drive gear teeth for wear that could stop the oil pump.