Date: 201202
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B747-400
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Parked
Aircraft component: Traffic Collision Avoidance System (TCAS)
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Avionics; Maintenance Powerplant
Human factors: Time Pressure; Communication Breakdown; Other / Unknown
Second reporter function: Technician
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural FAR; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Other Person
When detected: Other After Aircraft Released
Result: General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Chart Or Publication; Procedure; Manuals; MEL; Human Factors; Company Policy; Aircraft
Primary problem: Human Factors

Narrative: We had Aircraft X; a B747-400 with a TCAS lower antenna [write-up]. We found the coax [cable] was bad at the bench plug; so we robbed [cannibalized] the harness from Aircraft Y; another B747-400; which was going to ZZZ1 on a ferry flight for a corrosion repair. I was told to install the bad harness from Aircraft X onto Aircraft Y. I do believe we are not supposed to install a known bad part on an aircraft. I felt that I was under extreme pressure by management to install this bad part.


Second narrative: A local Line Maintenance Specialist approached me with a TCAS antenna harness and informed me that I was to install said harness in Aircraft X; a B747-400 aircraft [at the] TCAS bench plug. He is in a new position [carried over] from the merger of Air Carrier Y into our Air Carrier X. This position is Management and the closest parallel I have to it would be our Engineering group which is also Management. As a Union Shop our rules forbid Management from doing hourly rated work. This Specialist was involved with the TCAS harness so a Union Steward intervened and reminded him that he was doing hourly rated work. The solution for this situation; he was told; would be to have hourly rated employees perform this function that he was doing on his own. The Specialist agreed so I was assigned to help with this project on his orders which I did. His objective was to rob; [cannibalize]; from Aircraft Y; a B747-400; a good [TCAS} harness; which our Air Carrier X does not stock locally; and install it on Aircraft X. Aircraft Y was being prepared for a ferry flight for a permanent sheet metal repair under an Engineering Directive; Engineering Change Repair Authorization (ECRA). The TCAS job was to be a new deferred item. I understood that this deferred item would be to install a harness (Serviceable or Non-Serviceable) in position; and I was following verbal orders from the Maintenance Specialist. No one was certain that this harness would fix the problem.


Synopsis: Three Avionics Technicians; a Maintenance Specialist; a Maintenance Analyst; and a Maintenance Controller report about their involvement with four COAX cables robbed (cannibalized) from one B747-400 and installed on another B747-400 aircraft for a TCAS unit with a faulted lower antenna. The TCAS cable configurations were not Effective; not interchangeable; between aircraft.