All 137 people aboard the British Airtours flight leaving Manchester, England, should have escaped.
As the Boeing 737 accelerated down the runway, an explosion in the left engine sliced open a fuel tank. The pilots quickly slowed the jet and pulled to a stop on a taxiway, but by then the wing tank was spouting a trail of blazing jet fuel.
Before the passengers could attempt what should have been a harried but routine evacuation, intense flames surrounded the rear of the jet. In about a minute, fire burned through the plane's thin aluminum skin and a layer of insulation. Poisonous black smoke filled the cabin. Passengers and crew were felled in the aisles. Fifty-five people died, overcome by fumes, that day in March 1985.
Most commercial aircraft today remain just as vulnerable to a ground fire outside the fuselage as the Airtours 737 was in the Manchester accident 14 years ago. But now, after years of testing, the Federal Aviation Administration is racing to write rules that would protect passengers from such rare, but deadly, fires.
Insulation materials - the lightweight layer between a jet's skin and the cabin interior - must be better at holding back a roaring exterior fire, says Elizabeth Erickson, director of the FAA's Aircraft Certification Service. Airlines with jets that don't meet stricter standards will have to replace the insulation.
Protecting passengers
"We want to protect the passengers in a survivable crash," Erickson says.
New rules on the quality of airplane insulation could become one of the largest retrofit orders in aviation history, costing the airlines up to $1 billion.
Last October, the FAA announced it was targeting for replacement the same insulation material, some of which also can catch fire in flight from sparks or other source from inside an airplane.
That effort was prompted in part by fears that burning insulation might have played a role in the crash of Swissair Flight 111, which killed all 229 people aboard Sept. 2.
FAA scientists have been working for years on insulation's ability to resist an exterior fire. Once FAA officials decided to rewrite part of the insulation standards dealing with internal ignition sources, they felt it would be a "perfect time" to deal with exterior fires as well, says Ronald Wojnar, one of Erickson's top deputies. Erickson says officials hope to finish both sets of new standards by June.
The insulation under review isn't related to insulation on aircraft wiring, which also can create a hazard if it cracks and wires are exposed.
A recently released FAA test report shows that several newly available insulation materials, if properly installed, can add dramatically to an airplane's ability to withstand an outside fire.
Gaining time
In tests, the thin aluminum skin and adjacent insulation are no match for a nearly 2,000-degree jet fuel fire, which can burn through in about 90 seconds on a narrow-body jet like the 737. The thicker skin on a wide-body fuselage gives slightly more protection, about three minutes' worth.
Commercial aircraft currently must be certified to evacuate passengers within 90 seconds. But incidents such as the one in Manchester show that insulation needs to hold back an outside fire at least several minutes to allow everyone to escape.
By experimenting in recent years with a variety of insulation materials and different ways of attaching them to the interior of the fuselage, FAA scientists were able to hold back flames by up to eight minutes. Tests in England produced similar results, says Ray Cherry, a consultant to the British Civil Aviation Authority.
One of the best performing materials is a fire-resistant insulation known by the trade name Curlon, which is wrapped in a film called Kapton. The FAA test report said the material did not give off toxic gases and did not spread the fire.
The report praised Curlon because it can easily replace existing fiberglass-based insulation.
Sherman Smith, general manager of Orcon Corp., which makes Curlon, says his product could change insulation's role from solely passive - keeping out sound and cold - to an active "safety component."
A widespread order to retrofit commercial jets would be expensive. About 5,000 U.S.-registered airplanes could be subject to an FAA order, and an additional 7,000 foreign-owned jets likely would follow suit.
Some industry officials privately worry that the FAA is moving too quickly toward a replacement order and that other factors, such as the cost, should be given greater weight.
Although they are not common, fires associated with air travel have long been identified as deadly hazards. From 1981 to 1993, there were 34 U.S. crashes or incidents in which passengers initially survived but encountered fires as they tried to evacuate. Of 2,895 people involved in these incidents, 569 were killed by the fires and resulting fumes, the FAA says.
As a result, officials here and in Europe have instituted a number of protections to limit flammability and toxicity of interior equipment, such as seat covers and panels.
But they have yet to require a better barrier to outside fires. Officials say the effort has taken years because of the complexity of testing fires and budgetary strains that focused research elsewhere.
In all, 106 people have died worldwide over the past 20 years after exterior fires penetrated jets that were all or mostly intact while people attempted to evacuate.
In addition to the Manchester incident, 51 people died in an accident in Malaga, Spain, in 1982 when a DC-10 overran a runway. The jet's right wing was torn off, causing a huge fuel fire.
Fire entered the cabin through tears in the jet's skin and by burning through the fuselage.
The FAA has identified three other similar accidents, but none caused fatalities.
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