Swissair is to carry out an extensive programme of cockpit-area rewiring on its 19 Boeing MD-11s, starting in August. The airline's decision is based on analysis, since the September 1998 crash of one of its MD-11s near Halifax, Canada, of wiring routing in the forward fuselage, according to Swissair engineering company SR Technics.
SR Technics says that wiring routing and hardness is far from optimal. It has put forward a wiring design proposal to Boeing, the US Federal Aviation Administration (as the lead certification authority) the Transportation Safety Board of Canada (TSBC) (the Swissair MD-11 crash investigator) and the Swiss aviation authorities.
Included in the proposal is replacement of the relatively soft Tefzel-coated wiring by more durable wiring, to increase chafing resistance. The TSBC had a "routine" meeting with SR Technics on 14 and 15 February as a part of the continuing accident investigation.
Evidence so far suggests that, before the crash, the pilots lost the use of all flight instruments because fire spread through wiring in the cabin ceiling near the overhead circuit breaker (CB) panel.
Changes involve the radical rerouting of 17 wires between the avionics bay and the overhead CB panel, including wires for the standby artificial horizon, the battery buses and direct battery output. Overhead CBs for the No 3 transformer rectifier unit and the left emergency direct current bus feed from the air-driven generator are to be relocated to the main CB panel on the bulkhead aft of the co-pilot's seat. The refit is expected to cost about $20,000 per aircraft.
TSBC says it has not made additional recommendations for MD-11 wiring checks since December 1998, when it issued an advisory suggesting that operators adopt a wiring inspection routine defined by SR Technics and Boeing following the discovery of specific faults in fleet examinations.
• More than two weeks after the 30 January Kenya Airways Airbus A310-300 accident (Flight International 8-14 February), and a week after flight data recorder (FDR) recovery, the FDR had not been dispatched to an authority competent to download it. At Kenya's request it is to be sent to the Transportation Safety Board of Canada. Airbus Industrie comments that, for safety reasons, it wants the data made available as soon as possible.
Source: Flight International
