Definition
In aircraft sheet metal work, a small metal strip or tab used to align two mating parts in the correct relative position before they are permanently fastened, ensuring repeatable orientation and preventing rotational or lateral slippage between the parts.
Plain English
A small piece of metal that locks two parts together in the right position so they can't shift or twist when joined.
Context Anchor
Seen in aircraft maintenance when installing or inspecting rotating parts mounted on shafts, such as pulleys, gears, or similar parts.
Derivation
From the everyday sense of a 'key' as something that fits into a matching slot to lock things in place. In mechanical work, a key serves the same purpose between two parts: it fits into a corresponding cut or slot to hold alignment.
Why Pilots Care
If a key is missing, damaged, or not seated correctly, a part that should turn with a shaft may slip, which can cause a mechanical failure.
Intuition Check
Do not read key here as a door key or keyboard key. In this maintenance context, a key is a small locking piece used between two mechanical parts.
Example Sentence 1
The technician installed a key between the shaft and the hub to keep them from rotating independently.
Example Sentence 2
Inspect the key and keyway for wear whenever the magneto drive gear is removed.