TIM VAN BEVEREN / MIAMI
Carrier will exceed the requirements resulting from the 1998 crash off Nova Scotia
Swissair is redesigning the cockpit electrical distribution systems in its Boeing MD-11 fleet and installing an unprecedented level of fire detection and suppression capability in the front end of the aircraft.
The airline is working with Boeing and the US Federal Aviation Administration, but although its new electrical distribution system will be certificated, there is no indication from Boeing or the FAA that the plan will be mandated by the manufacturer or the agency for retrofit to MD-11s with other airlines. Boeing says it is not offering the wiring modifications to other carriers because it does not see "a quantifiable benefit".
Motivation to rewire arises from the September 1998 Swissair 111 crash off Nova Scotia, Canada. The work is being carried out on the carrier's entire fleet of 19 MD-11s, even though they are all due to be replaced by Airbus A340-600s beginning late next year, then sold to FedEx Express as freighters. Swissair has estimated the cost per aircraft at $675,000. The purpose is to reduce the risk of fire caused by electrical short-circuiting from chafing-damaged wires and, in the event of a fire, to protect flight instrument operation. Evidence suggests a major causal factor in the Swissair crash was the crew being unable to orientate themselves.
Techniques employed in the refit include carefully planned wiring re-routing, separating emergency supplies from the main wiring bundle and the replacement of relatively soft Tefzel wires with more durable materials in areas where chafing is possible. Boeing maintains that Tefzel is not used in all the aircraft and that there are no chafing points.
The engineering of Swissair's additional fuselage fire detection and suppression systems is in line with a Transportation Safety Board of Canada (TSBC) paper issued in December 2000. This recommends that the lessons about aircraft vulnerability to fuselage fires emerging from the investigation should be applied in all aircraft types.
As well as installing smoke detectors and video monitors, Swissair plans to install points in the cockpit ceiling into which halon fire extinguishers can be discharged, and is changing fire barrier and smoke containment materials. This is all far beyond any regulatory requirement, but Swissair remarks: "Safety is the highest priority."
Source: Flight International
