The equipment on the A/C is identified by a unique identifier designated Functional Item Number (FIN). The basic element of the FIN is a two letter code indicating to which System/Circuit the equipment belongs. To this code are added prefixes and/or suffixes which provide the unique identification for individual items of equipment.
AIRBUS has defined functions for each system, these functions are called Functional Item Numbers (FINs). The physical item installed on the aircraft is the Part Number (PNR). The FIN is unique in the aircraft even if one PNR can be used for several FINs.
Each part with a precise function within an A/C system is defined with a specific identifier called FIN. A part may have a multiple quantity retaining the same FIN should it be the same function. Typical example would be the PAX layout whereby a seat is located several times in the A/C and has just one designated FIN.
The FIN is generally unique in the Aircraft. The location of the FIN may vary from Aircraft to Aircraft if the associated system is located in a different position.
Airbus uses a specific method to identify the location of components on aircraft – a unique identifier known as a Functional Item Number (FIN). All components not specifically related to a circuit are identified by fictitious circuit letter V. The second letter defines the type of component.
- VC – Electrical connectors
- VU – Panels / Racks
The panels and racks are identified in fictitious (imaginary) circuit VU by a numerical designator.
Example: 123VU –
- 123 : Component prefix
- VU : Fictitious circuit code
- VU – Virtual Unit
The circuit letter M is reserved for mechanical FINs. Example: 2381HM.
A complete list of system/circuit letter codes and an explanation of the FIN breakdown can be found in the Introduction of the Aircraft Schematic Manual (ASM), Aircraft Wiring Manual (AWM) and Aircraft Wiring List (AWL).