B747-400
Maintenance Avionics
Situational Awareness; Confusion; Communication Breakdown
Aircraft Equipment Problem Critical
General Maintenance Action
Human Factors; Chart Or Publication; Manuals; Aircraft
Given an assignment with parts ordered and on hold to replace the R48 [Relay]. Deferral was updated with parts needed. It [Relay] looks different than the other three [relays] installed; but match R48. Upon checking the online Illustrated Parts Catalog (IPC) 28-22-51-006a under Item-25 with company Part Numbers (P/N) and Sub-section-25 with Manufacturer's (MFG) Parts Number that do not cross to company Part Numbers; [I] was not aware that replacement relay is a non-stock part. Since Pre and Post-Service Bulletin (S/B) Part Numbers (P/N) are both under the same company Part Number item at the moment; I believed I was installing the correct part.
Reporter stated there are four relays; each identified with an 'R' and a two digit number; such as R-46; R47; R48. The relays are located in the 414 Power Panel in the Main Equipment Center (MEC) on B747-400 aircraft. One relay for each Main wing tank boost pump. The deferral involved a right wing Main fuel tank boost pump and the associated R48 Relay. The R48 Relay had been upgraded to a Ground Fault Interrupter (GFI) design as a result of a Service Bulletin (S/B); but was still listed under their company's Parts Numbering System with the same P/N as the older Non-GFI Relay. Reporter stated the Aircraft Wiring Diagram Manual still refers to the upgraded relays as R46; R47; R48; but their Illustrated Parts Catalog (IPC) and IPC item Sub-section did not have a new company P/N to identify the upgraded R48 GFI-type Relays. They were both listed under one Part Number even though the Manufacturer's part numbers were different. His company has since revised their IPC Manual to reflect the Pre and Post Service Bulletin Relays.
Inadequate information in the Illustrated Parts Catalog (IPC) led to installing a Pre-Service Bulletin R48 Relay in the 414 Power Panel of a B747-400 aircraft. A Ground Fault Interrupter (GFI) type R48 Relay associated with the right wing Main fuel tank boost pump was required.