OTTAWA — Thirteen years after faulty wiring downed Swissair Flight 111 off Nova Scotia, the risk remains because the federal government still does not require aircraft wiring to be tested under realistic operating conditions, the Transportation Safety Board charges.

The TSB first recommended aircraft wiring undergo more rigorous and realistic flammability and arcing certification testing in 2001 in the midst of its $57-million investigation into the Sept. 2, 1998 crash.

Now, after a decade of pressing unsuccessfully for the change, the independent federal transportation safety agency has issued a statement alleging the “risk remains” because Transport Canada has so far, failed to act.

The government department responded forcefully Friday, saying it, “fully supports the intent,” of the TSB’s call for action, but is hamstrung by the need to harmonize any new domestic regulations with the rest of the commercial aviation world.

Jurisdictional complexities aside, the TSB says the continuing federal inaction means the fuselage wiring in commercial aircraft in Canada has not been tested against the various conditions that aircraft wiring, especially insulation, experiences inflight. The situation is the same in the U.S. and Europe.

Current tests do not even require that the test wires be powered. The board says that omission eliminates understanding the dynamics of how energized wire, especially with aging or damaged insulation, can fail during an arcing event.

The issue was among 23 safety recommendations in the TSB’s 2003 final report on Flight 111. Only seven have been fully implemented by Transport Canada.

While the board considers a repeat of the circumstances that doomed the flight a low probability, “the risk associated with wires is not going away,” says John Britten, a senior TSB accident investigator (engineering) and a safety analysis team member on the Swissair crash.

Large modern aircraft can contain more than 250 kilometres of wire of various sizes and insulating materials and, “there’s more bells and whistles going into the passenger cabin than they’ve ever had before and every one of those relies on wires,” he says.

“Not every arced wire on an aircraft ends up in an inflight fire but we want to reduce the potential for that and make flying even safer.”

About an hour after the Flight 111 McDonnell Douglas MD-11 departed New York for an overnight flight to Geneva, the crew diverted to Halifax because of smoke in the cockpit.

While manoeuvring over the Atlantic Ocean for an emergency landing in Halifax, fire raced through the cockpit’s ceiling, knocking out flight displays, navigation, communication and other systems. The airliner plummeted into the water and disintegrated five nautical miles southwest of Peggy’s Cove, killing all 229 passengers and crew.

In 2003, a TSB investigation determined the likely cause was an electrical arc caused by damaged insulation on a piece of wiring hidden in the cockpit’s ceiling. The spark ignited flammable thermal acoustic insulation blankets lining the ceiling’s interior and flames then fed on other flammable materials in the cabin.

The board’s 23 safety recommendations related to wiring, circuit-breakers, flammable materials, on-board firefighting and flight data and voice recorders. Seven have been fully implemented, including the removal of flammable insulation on all Canadian aircraft. The U.S. and other nations have done the same.

Ottawa Citizen


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