Definition
Storage compartments built into the engine nacelles of some multi-engine airplanes, used for stowing baggage or equipment. Items placed in nacelle lockers must be included in weight and balance calculations, as their location affects both total weight and the airplane's center of gravity.
Plain English
Small storage areas built into the structures that house the engines on some twin-engine airplanes. Pilots can put luggage or gear in them, but the weight has to be counted when working out how the airplane is loaded.
Context Anchor
Seen in weight and balance data, loading charts, and preflight planning for some multiengine airplanes.
Derivation
Nacelle comes from the French word for a small boat or basket, originally describing the gondola hung beneath an airship. In modern aviation it refers to the streamlined housing around an engine. A locker is simply a lockable storage compartment. Together: a storage compartment located inside the engine housing.
Why Pilots Care
Items placed in nacelle lockers add to total weight and can affect the center of gravity if not accounted for properly.
Intuition Check
Do not think of a nacelle locker as just an extra convenient storage bin. In weight and balance, it is a specific approved loading location with its own effect on the airplane’s balance.
Example Sentence 1
Before the flight, the pilot weighed the bags going into the left and right nacelle lockers and entered each amount on the loading sheet at the correct arm.
Example Sentence 2
The mechanic secured the spare parts inside the nacelle lockers so they would not shift during the ferry flight.