Investigator Finds Burnt Wires On MD-11

April 9, 2000 - NEW YORK (USA) -- An investigator hired by families of Swissair 111 victims has found evidence of burnt wires and poor workmanship aboard MD-11 jets like the one that crashed off Nova Scotia in 1998, killing 229 people.

Ed Block, a wiring expert and member of a U.S. Federal Aviation Administration committee, was in Switzerland in January and February to inspect wiring on four planes.

Three had potentially lethal problems, including one with so-called arc-tracking in the ceiling just behind the cockpit, Block told The Canadian Press.

The phenomenon, similar to a short circuit, is believed to have contributed to the Sept. 2, 1998, crash off Peggy's Cove. Canadian investigators have found evidence a fire developed in the ceiling near Flight 111's cockpit.

"These aircraft were an accident waiting to happen," said Block. "From what I've observed in these inspections, (installation practices) were very unprofessional, haphazard."

The International Aviation Safety Association, which Block co-chairs, has promised to turn over the findings to Canada's Transportation Safety Board.

It appears Swissair, meanwhile, is addressing some of Block's concerns by proposing major changes to electrical systems aboard its MD-11 fleet.

"Wire separation, routing and protection have been proven to be insufficient, especially in the cockpit area," says a memo from SR Technics, the airline's service arm.

"In the case of sr111, this has contributed to the loss of essential functions, including display functions."

Swissair did not return phone-calls.

Lori Gunter, a Boeing spokeswoman, said the manufacturer has only recently been given the airline's complicated proposal. The company and the FAA, aviation's senior regulator, must approve changes.

"We're now going through and reviewing it," Gunter said from Everett, Wa.

"It is still a draft document and it's still uncertain whether it will end up being just a Swissair modification that we review and approve for them or something that we choose to adopt for the whole fleet, or even if it's a technically sound recommendation."

There are about 160 kilometres of wires aboard an MD-11. Block said only about 60 per cent can be inspected visually.

"It was to me almost a miracle that there haven't been more instances of electrical shorts and anomalies in these aircraft because of the state of the wiring," said Block.

Accompanied by representatives from Boeing and Swissair, he found missing clamps and wires routed through fuselage with no protective covering. Some low-output signal wires were mixed with high-output power wires.

But most disturbing, he said, was the evidence of short circuiting on one aircraft.

"We saw a burn mark in a Kapton wire that had actually arced onto the mylar (wall) insulation," Block said. "That was over the top of the forward galley on the right side."

Block says the Flight 111 aircraft and the MD-11s he investigated were built around 1991, about the time the FAA audited McDonnell-Douglas.

"They found poor workmanship, outdated specifications -- a general laxity of a professional nature of the creation of these aircraft," said Block, who has requested the audit under U.S. freedom-of-information laws.

Boeing, which took over McDonnell-Douglas two years ago, is shipping its last MD-11 this spring. The only normal people are the ones you don't know very well.- Joe Ancis

There are 174 of the jets worldwide, none in Canada. Wiring on the aircraft has been subjected to an unusually high number of regulatory safety directives -- 47 in 10 years, half of them since the crash. The latest was issued last Wednesday.

"It's not unusual following an accident for there to be increased scrutiny and therefore increased changes," said Gunter.

"Even though, with Swissair, no cause has yet been determined, we know enough about that accident to go and look at that area (wiring) really, really hard."

Block said he found wire bundles with mixed insulation types on the older aircraft, including wires covered in controversial aromatic polymide tape, or Kapton, mixed with wires covered with much softer Tefzel.

The U.S. military and numerous wire experts have warned against the practice because vibration can cause the Kapton to wear away Tefzel like sandpaper, exposing bare wire.

"The Tefzel was totally mixed with Kapton bundles," Block said. "These wires ran through the fuselage over sharp edges.

"This is particularly grievous as far as opportunities for chafing are concerned. It only takes one breach in the insulation to create that situation where the arc-tracking phenomena will occur."

In its memo, SR Technics proposes removing Tefzel "where applicable."

Arc-tracking begins as a spark from one damaged wire to another.

With Kapton, found to be particularly flammable and susceptible to damage, sparks can char the insulation, creating carbon buildup. The carbon eventually acts as a conductor and the sparking begins tracking along wires.

The problem can ultimately lead to an explosive fire that burns at 5,000 degrees, incinerating everything in its path.