A team from Boeing, the US Federal Aviation Administration and the National Transportation Safety Board has been inspecting the wiring on 737-400s. The checks were ordered after an Alaska Airlines aircraft was forced to return to Portland, Oregon, when chafed wires triggered false low fuel pressure readings.
As Flight International closed for press, the FAA confirmed that 14 of Alaska's 36 -400s had been checked, two of which had revealed damaged wiring. The discovery showed melted insulation as well as chafing, exposed wiring and evidence of sooting in wire bundles.
According to on-line sister publication, Air Transport Intelligence, the initial incident was traced to damaged wires in the cargo hold between fuselage stations 400 and 410. The problems caused warning lights to illuminate, indicating low fuel pressure in the number two and centre fuel tanks.
Although previous FAA airworthiness directives have been issued on 737 wiring, they have been concerned mainly with checks for exposed wiring inside the fuel tanks themselves, rather than other areas of the aircraft.
"So far we don't know if this is a new issue, or a continuing issue," says the FAA. "We are continuing the inspections of the aircraft."
Boeing says that it "understands the situation", adding: "The monitoring systems worked the way they were supposed to."
Source: Flight International
