The US National Transportation Safety Board (NTSB) and Federal Aviation Administration have disagreed on the potential safety threat posed by deteriorated electrical wires running through old commercial transports still in service.

The difference of opinion was aired during a Congressional hearing on advances in aircraft electrical systems. Faulty wiring may have been a factor in the crashes in July 1996 of a Trans World Airlines Boeing 747 and a Swissair Boeing MD-11 last September.

The NTSB's Bernard Loeb says inspection of the TWA Flight 800 wreckage revealed fuel tank wiring repaired using string and adhesive tape, and cracked wiring insulation. NTSB examinations of wiring on more than 20 Boeings and Airbuses found wire bundle clamps that cut into wiring and chafed/cracked wiring insulation, raising its "concern about the safety of electrical systems as aircraft age".

Although the FAA has responded to the NTSB recommendations with a series of airworthiness directives, the FAA's certification chief, Tom McSweeny, says that its survey of ageing aircraft "revealed no situations that presented immediate safety concerns".

Source: Flight International