Definition
An identifying number assigned by a manufacturer to a specific component, assembly, or piece of equipment. The part number uniquely identifies that item's design, configuration, and intended application, distinguishing it from similar-looking parts that may not be interchangeable.
Plain English
A unique number a manufacturer puts on a part so it can be identified exactly. Two parts that look the same may have different part numbers, which means they are not the same and cannot be swapped.
Context Anchor
Seen in aircraft parts catalogs, maintenance records, inspection paperwork, and when ordering or replacing aircraft parts.
Why Pilots Care
Using the correct part number is how mechanics ensure a replacement component is the right one for the aircraft. A wrong part number — even for something that physically fits — can mean an unapproved or incompatible part, which affects airworthiness.
Intuition Check
Do not treat a part number as just any number printed on a part. A part number identifies what the item is; a serial number identifies one individual item among others of the same kind.
Example Sentence 1
The mechanic checked the part number on the new oil filter against the maintenance manual before installing it.
Example Sentence 2
Ordering by the correct part number ensured the replacement voltage regulator was the approved model for the aircraft.