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Thursday, September 10, 1998

Airlines ignored wiring problem -- experts

By STEPHEN THORNE -- The Canadian Press

HALIFAX (CP) -- The U.S. military warned aircraft manufacturers about

the dangers of a highly volatile insulating film years ago, but a former navy

official says the companies didn't want to hear about it.

Aromatic polyimide tape insulation, widely known by DuPont's trade name

Kapton, has been cited as a potential factor in last week's crash of Swissair

Flight 111 off Nova Scotia, where all 229 aboard were killed.

The insulation was first found to deteriorate prematurely and promote

electrical arcing aboard U.S. navy aircraft in 1981. The U.S. military

effectively banned its use in new planes and in replacement wiring in 1985.

"It really is dangerous stuff," said Robert Dunham, a retired aerospace

engineer who was responsible for aircraft wiring and related naval systems

for 15 years.

"The thing is, the aircraft companies have been well aware of this problem.

It really was just a major cover-up."

Dunham said he and his colleagues made videos showing what Kapton can

do once the polymer breaks down: the wire chars undetectably over time

until it becomes volatile, then electrical arcs can track along the aromatic

polyimide tape like lightning bolts.

The arcing occurs at 5,000 degrees Kelvin (4,727 C) vaporizing everything

in its path. The phenomenon is known as arc-tracking, or a flash-over.

Dunham said navy officials went to every major manufacturer, including

Boeing and McDonnell Douglas, builders of the MD-11. He said some

companies suggested they were doctoring their research.

"The airlines just didn't want to know the problem because if you don't

know the problem, you don't have to deal with it," Dunham said from

Fairfax, Va.

"If they were to replace all of that wire, this would mean a major

disassembly of the aircraft. You're talking big bucks, out-of-service time,

etc., and they're just not going to do it. They wouldn't do it."

Most major airlines have aromatic polyimide tape insulation in at least some

of their aircraft, including many MD-11s, MD-80s, 727s, 737s, 767s and

DC-10s. Some is manufactured by Japanese firms.

"Some of them admitted they had problems with it, even back in 1988,"

said Dunham. "TWA was very forthcoming, and said yeah, they had a lot of

fires in the L-1011s."

Several helicopter companies, including Sikorski and Bell, did stop using

the insulation. McDonnell Douglas, since taken over by Boeing, started

substituting a Teflon-Kapton (TKT) insulation in new MD-11s in 1995.

"We are aware of the arc-tracking, of course," said Cathy Andriadis, a

spokeswoman for DuPont in Wilmington, Del. "That was one of the reasons

that the TKT product was developed, to deal with that.

"We have been aware of the arc-tracking in isolated incidences. We have

not seen that as a common occurrence. Nor have we seen as a common

occurrence anything having to do with bursting into flames, copious smoke

production or anything else."

Sources told The Canadian Press the Canadian military worked closely with

the Americans on the problem in the 1980s. The insulation has been

removed from CF-18 fighter aircraft, or steps have been taken to avoid

problems with it. It has also been ordered out of Aurora long-range patrol

aircraft.

Harrier fighter aircraft in Britain were rewired in 1991 due to total electrical

failures and fires in Kapton-coated wiring.

Armand Bruning, a U.S.-based electrical engineer contracted several years

ago to test the insulation in Canadian CF-18s, said Kapton-type insulation is

an excellent product under the right conditions.

"It is probably one of the most wonderful insulation materials I've ever

seen," said Bruning, who has a PhD in insulation systems design.

"It has characteristics which have not been recognized by the applications

people. This is a pervasive problem. It's a little bit like asbestos because it's

on most of the planes in the world."

Bruning, who did the U.S. navy's thermo-dynamics research on the issue,

found Kapton-encased wiring was 75 per cent aged in three-year-old

CF-18s. He wanted to test commercial jets, but his repeated requests were

rejected.

"Kapton has the characteristic that it .. . deteriorates if it has high

temperature and moisture and strain," he said.

"The navy did those three things faster than the air force did, and the air

force probably did it faster than the commercial airlines. So the navy had

trouble first, the air force had trouble next ... and so on."

Swissair said its seven-year-old aircraft involved in the Sept. 2 crash passed

a day-long inspection in August.

But Bruning, head of Lectrical Mechanical Design Co. of Washington,

D.C., (Lectromec) said the general-aviation industry does not have the expertise to

properly test insulation aboard its planes. The insulating film is the thickness

of five to seven human hairs. It comprises 40 per cent of the wire's weight.

"The problem is the present aircraft industry only knows how to measure

the quality by looking at it with the naked eye. They can't tell how good or

bad it is until they see a break in the wire."

He said he has been seeking permission to test aromatic polyimide tape

insulation in commercial airliners for at least a decade.

"We've so far never been able to get any commercial airline to let us test

their wire," said Bruning.

"Once they find out they've got a problem they have to report it to the

government; the government will go ballistic and paint them as a terrible

airline and make them spend millions of dollars.

"So as long as they don't have any real epidemic problem, they don't want

to hear about it. It's a cancer-denial syndrome."

Halifax-based IMP Group and Bombardier of Montreal have been

conducting changeovers for the Canadian military. Bruning said IMP has

been doing them at a third of the estimated cost.

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