By Stephen Thorne / The Canadian Press

Tacoma, Wa. - Military authorities and commercial aviation regulators warned of faulty aircraft wiring in the early 1990s, but one did it secretly and the other was ignored, government documents and a navy video suggest.

Kapton-insulated wiring like that aboard a Swissair plane that crashed off Nova Scotia last September was the subject of a 1992 navy training tape.

The internal video cautioned service personnel of dangers inherent in aromatic polyimide tape insulation, or Kapton, many of which have cropped up in the Swissair investigation and subsequent inspections of MD-11 aircraft.

"Experience has shown that there are serious problems with polyimide film-insulated wire," said the video, made seven years after the navy banned Kapton's use in new aircraft and replacement wiring.

"The problems of chafing, chemical and thermal breakdown, and stress affect all wire insulations. With polyimide film-insulated wire, however, the probability is greater that these problems will lead to more serious arc-tracking and flashover failures."

Arcs are lightning-like jumps from wire to wire that can track along charred insulation and eventually erupt in an explosive electrical fire known as a flashover.

Arced and badly burned Kapton and other wires were found aboard the Swissair jet that crashed Sept. 2 near Peggy's Cove, killing all 229 aboard.

Boeing's chief safety officer has said some of the MD-11's wire was burned from the inside out, indicating it was a source of the problem. Evidence indicates multiple electrical systems failed before the plane went down.

Chafed and damaged wires have been found aboard other MD-11s since the crash, leading to more government-ordered inspections, the most recent last week.

The industry and its chief regulator have maintained the Kapton problem is unique to military aircraft, with their tightly packed wires, high-stress performance demands and often damp environments.

But The Canadian Press has obtained documents showing the U.S. Federal Aviation Administration had concerns similar to the military's the same year the Swissair jet was built.

A 10-page advisory issued by the FAA on April 5, 1991, warned against careless servicing and cited other problems similar to those found aboard MD-11s in recent months.

The document, obtained from FAA member Ed Block, specifically cited Kapton for special attention, cautioning operators against quick-and-dirty electrical work.

"Service experience shows that non-conforming reinstallations, especially if done hurriedly, can significantly increase the potential for electrical faults, smoke, or fires," said the circular, signed by Leroy Keith, manager of the FAA's transport airplane directorate.

"In installations where wires of wire bundles are expected to flex ... aromatic polyimide-insulated wires should be avoided."

The FAA recently ordered inspections of wiring around Swissair's inflight entertainment system, installed early last year, and above a cabin door where wires are likely to flex. Damaged wire insulation has been found.

Last week, the FAA issued five more airworthiness directives affecting wiring aboard MD-11s. They bring to about 25 the number of electrically related orders affecting MD-11s issued since 1992.

Former military officials have said they warned manufacturers about the Kapton problem in the 1980s. The industry didn't want to hear about it, they said, because fixing it meant spending money.

There is evidence the airlines pressured Boeing to drop Kapton well before it took over McDonnell Douglas two years ago.

United Airlines demanded the Seattle-based manufacturer install a different wiring before buying jets in 1989. And TWA "strongly objected" to its use as far back as 1977.

McDonnell Douglas dropped Kapton from the MD-11 program in 1995, replacing it with a cheaper and lighter Kapton-Teflon combination that has received positive reviews.

Boeing no longer installs Kapton in any of its planes. But it remains aboard a large proportion of the aging airline fleet.