Canadian accident investigators are again sifting the wreckage of the Swissair Boeing MD-11 Flight No SR111 to check whether cockpit map reading lights could have been the ignition source for the fire which brought down the aircraft, flying from New York to Geneva off Nova Scotia in September 1998.
Heat damage caused by the recessed halogen lamps has been found in operational MD-11s. Although the Transportation Safety Board of Canada (TSBC) investigators have not been able to link this heat damage directly with the accident aircraft, they are combing the recovered wreckage again. The TSBC says: "When you initially go through wreckage you don't know what you are looking for." Now they are looking for parts of the map lights.
Boeing has issued an alert service bulletin for all MD-11 operators to check the lights frequently until they can be replaced, meanwhile protecting adjacent insulating material from heat damage by using heat-resistant tape.
During a replacement by Swissair of the MD-11 cockpit area MPET (metallised polyethylene teraphthalate)-covered insulation material, heat damage caused by the recessed lights to the MPET was discovered. The TSBC was monitoring the strip-down to see if it could discover clues as to how the Swissair fire was ignited.
Since then heat damage to the light fittings themselves and to the immediately adjacent MPET-covered insulation blanket were discovered in "about a dozen MD-11s from two operators", according to a letter from the TSBC to the US National Transportation Safety Board.
The US Federal Aviation Administration is preparing an airworthiness directive based on the Boeing bulletin.
Source: Flight International
