Definition
The mechanical assembly on an aircraft engine starter that engages the starter motor with the engine's ring gear during start, then automatically disengages once the engine begins running under its own power. It typically uses a small pinion gear that slides into mesh with the ring gear on the flywheel or crankshaft, and an overrunning clutch or Bendix-type mechanism that disconnects the starter once engine speed exceeds starter speed.
Plain English
The part of the starter that pushes a small gear out to spin the engine, then pulls back so the running engine doesn't drive the starter motor.
Context Anchor
Seen in discussions of aircraft engine starting systems, especially when describing how electrical starter power is transferred to the engine.
Derivation
From 'starter' (the motor that begins engine rotation) and 'drive' (the mechanism that transmits power between two shafts). The 'drive' part is the key idea: it's not the motor itself, it's the linkage that connects the motor to the engine and then breaks that connection.
Why Pilots Care
A worn or failed starter drive prevents the engine from cranking, causing start delays or groundings until repaired.
Analogy
It is like briefly using your hand to spin a toy propeller, then pulling your hand away once the propeller keeps moving by itself.
Intuition Check
Do not read drive as a road, a trip, or a storage device. Here, drive means the mechanism that transfers turning force from the starter to the engine.
Example Sentence 1
After the engine fired, the starter drive disengaged with a soft click and the starter spun down.
Example Sentence 2
Once the engine fired, the starter drive automatically released to protect the starter motor from overspeed.