Advertising

Friday, September 4, 1998 - Page updated at 12:00 AM

E-mail article     Print

MD-11 Had Earlier Faa Warnings -- Pilots Had Reported Smoke Before Crash

Seattle Times Aerospace Reporter

In the recent history of MD-11 jumbo jets, there are a handful of U.S. safety orders calling for inspections and modifications to eliminate electrical fire hazards inside the airplane.

One airworthiness directive from the Federal Aviation Administration dealt with a fire hazard near the cargo compartment. Another cited worn wiring, electrical arcing and a fire in the electronics area below the cockpit.

A third called for inspection of wire bundles in the cockpit after chafed wires caused electrical arcing during a flight, which could cause a fire and fill the flight deck with smoke.

It's far too soon, of course, to draw conclusions about what caused the crash of Swissair Flight 111, a McDonnell Douglas-built MD-11, off Nova Scotia on Wednesday. But when the crew alerted air-traffic controllers there was a problem, they reported smoke in the cockpit, according to Swissair.

Canadian officials today brought in the 200-foot submarine HMCS Okanagan, signaling they were preparing to shift gears from a massive rescue operation into a search and salvage mission. Officials hope to find the plane's flight recorders, which may shed light on the cause of the crash.

Benoit Bouchard, head of the Transportation Safety Board of Canada, said large parts of the plane may still be intact underwater, since only about a fourth of the bodies have been found. However, nothing larger than the size of a car has been found so far, said Lt. Cmdr. Jacques Fauteux, spokesman for the Canadian rescue operation.

Finding the answers could require a massive underwater recovery of the aircraft in parts of the ocean as deep as 160 feet.

A fire aboard Swissair Flight 111 could have been caused by an unsafe condition like those identified by the FAA - or by any of a number of other scenarios, like an oven fire or a passenger smoking.

The investigation into the crash of TWA Flight 800, a Boeing 747, near Long Island, N.Y., two years ago has raised many questions about aging aircraft and worn wires, for example. Wires can be vulnerable to chafing and aging, depending on their layers of insulation and composition.

In the context of the MD-11, a three-engine plane that has been in service only since December 1990, the issue is less likely to be age. The Swissair plane was 7 years old, with 35,000 flying hours and 6,400 flights - perhaps a third of the way through its useful life.

The MD-11's airworthiness directives document thoroughly researched problems and orders requiring fixes. But another, far-less-methodical record called a service difficulty report (SDR) provides a more routine portrayal of the life of an airplane.

SDRs are filed by airlines somewhat inconsistently and therefore are a minimum measure of problems with a given plane. The detail of the reports, filled out mostly by maintenance workers and pilots, varies greatly. That's why they are not used as a measure of comparative safety from one airline to the next, from one aircraft to the next.

But occasionally SDRs, kept by the FAA, reveal trends, such as the rudder problems with Boeing's early-model 737s.

An analysis of SDRs on MD-11s, prepared for The Seattle Times by Kolbenschlag Aviation Services in Falls City, Ore., turned up 40 records mentioning smoke or fire.

Many incidents were routine, albeit potentially hazardous. Coffee-makers malfunctioned. Fluorescent lights smoked. Galley ovens overheated or harbored grease fires. An in-seat video system sparked. Flames shot out of a video player. Air-conditioning systems pumped smoke into cabins.

A passenger, caught smoking in a lavatory, had dropped the cigarette in the trash bin, which smoldered. It was extinguished with water - and coffee.

Many of the electrical problems were solved by turning off the power to the particular system. But if fire starts, it can fester undetected, as it did in the cargo hold of a ValueJet DC-9 that crashed shortly after takeoff from Miami in 1996. It was later found to be carrying an illegal shipment of chemical oxygen generators that ignited in the cargo hold.

The FAA has since cracked down on such hazardous cargo.But once fire-detection and suppression systems are improved, there isn't much that can be done to guarantee that an airplane's own design or part won't create a problem. Engineers agree there are latent flaws in any complex system.

Unlike the ValuJet DC-9, the Swissair MD-11 was equipped with smoke detectors and powerful Halon gas fire extinguishers in each of its three large cargo bays. The only bay not protected by a fire extinguisher was the electrical-equipment bay, beneath the cockpit in an unpressurized part of the plane.

The three MD-11 electrical problems the FAA dealt with stand out from several others related to fire hazards. They certainly weren't anticipated, but they were detected:

-- In 1995, the FAA issued an urgent airworthiness directive citing the discovery of improper grounding of an MD-11 galley system that had caused electrical arcing and apparent burning of nearby insulation. A cargo-hold fire could result, the FAA said. Improper hardware installation was blamed.

As in the other two cases, McDonnell Douglas had already issued a service bulletin. The FAA made inspections and corrections mandatory starting Sept. 5, 1995. Airlines had three months to comply.

-- Also in 1995, an urgent airworthiness directive was issued for the inspection of wiring in the electronics compartment under the MD-11 cockpit, where computers and other avionics reside, to ensure there was no damaged wiring that could cause arcing and a fire.

The FAA said the order was prompted by a report of a fire caused by arcing, which was enabled by wiring chafed when a bundle worked its way loose from a clamp.

The safety order took effect on Nov. 20, 1995. Airlines had a month to comply.

-- In 1997, a directive was proposed calling for inspections to detect wire chafing or damage in certain bundles behind a panel in the cockpit. Concern was prompted by a report that a circuit breaker was tripped in flight due to arcing that was caused by faulty wiring.

The FAA said such a condition could have caused a fire and filled the cockpit with smoke. After public comment, the FAA made the inspections mandatory on June 16, 1997, just a few weeks before Boeing acquired McDonnell Douglas. Airlines had six months to comply.

FAA directives are mandatory for U.S. airlines only, but Swissair spokesman Roland Breitler said today the airline routinely complies with all directives, even those that are not mandatory.

"Swissair always follows each directive," he said. "If we hear of a potential problem then we immediately take action."

Breitler added that Swissair did make repairs called for in the 1997 FAA directive concerning the potential problem with cockpit wiring.

At the time the Swissair plane was made, McDonnell Douglas used a type of wire called Kapton exclusively, said Frank Campbell, a research chemist who studied Kapton for years at the Naval Research Lab.

Campbell said he'd rank Kapton as "about the worst" type of commercial aircraft wire used during the past 20 years. "It burned extremely hot and would burn other flammable materials in the vicinity."

Information from The Dallas Morning News, Newsday, The Associated Press and New York Daily News is included in this report.

Copyright (c) 1998 Seattle Times Company, All Rights Reserved.

advertising


Get home delivery today!

Advertising

Advertising