3 A.T.A. 100This is a universally accepted system for numbering aircraft maintenance documentation.The chapter number assigned to a specific system is the same, regardless of aircraft manufacturer.For example, ATA Chapter 21 is “Air Conditioning” on Boeings, Lockheeds, Airbus, etc.
7 ComponentsA third number completes the ATA chapter reference, and is usually used to define a specific component in a subsystem.For example…27 00 FLIGHT CONTROL SYSTEM27 10 ROLL CONTROLAILERONThe 14 denotes the specific component in the aileron control system…in this case, the aileron itself
18 As a part number is an identifier of a part design (independent of its instantiations), a serial number is a unique identifier of a particular instantiation of that part design. In other words, a part number identifies any particular (physical) part as being made to that one unique design; a serial number, when used, identifies a particular (physical) part (one physical instance)