Part number (P/N)
The part number is the manufacturer's identifier for a specific design of part. It tells you what the part is, not which individual unit you are holding. The same part number can be made by different approved manufacturers, so the number alone is never the whole story.
Serial numbers and batch (lot) numbers
A serial number identifies one individual unit and follows it through its life. Rotable and life-limited parts are normally serialised, so their history can be tracked. Consumables and hardware are usually identified by batch or lot number instead, which links a group of items to the production run they came from.
Alternates, interchangeables and supersessions
- Alternate or interchangeable part numbers: different numbers that are approved for the same use. Your maintenance data says which are acceptable on your aircraft.
- Superseded part numbers: the manufacturer has replaced an older number with a newer one. A supplier that only searches the old number can miss stock listed under the new one.
- Modification status: some parts are only acceptable at a certain modification or service-bulletin standard.
CAGE codes
A CAGE code is a short code that identifies the company that made or controls the design of an item. It appears in many procurement and technical records, and it helps tell two similar-looking part numbers from different manufacturers apart.
Why traceability matters
Traceability is the documented chain linking a part back to its manufacturer or to the approved organisation that last worked on it. Without it, an operator cannot demonstrate that a part is airworthy and can be refused at inspection, or worse, a suspect unapproved part can reach an aircraft. Keep the paperwork with the part, and check that the identifiers on the paperwork match the identifiers on the part.
Searching well
- Search with and without dashes, spaces and leading zeros, because suppliers format the same number differently.
- Give the supplier your alternates and the aircraft or engine the part is for.
- If a search finds nothing, send a request anyway. Stock that is not listed can often still be sourced.