Raiders of the lost arc; how to shoot down an F-16 with a BB gun.
It was a sure bet that the enemy wouldn't be using BBs in a dogfight. But BBswere all it took in Norfolk. The tiny pellets, fired ftom a Daisy air rifle, produced the electrical equivalent of a nervous breakdown. The wires seemed to explode.
The implications of that 1984 experiment began to crystallize a year later, when the tests moved from the back lot to the laboratory and BBs were replaced by .30 caliber bullets. At the Naval Research Laboratory in Washington D.C. and the Naval Air Test Center in Patuxent River, Maryland, technicians found that although one wire type would erupt in a fireworks display of sparks and flame when fired upon, two other types would not. But that was little consolation for the Navy. Kapton, the type of wire used most often in the Navy's hottest frontline fighters-and those of the other service branches as well-was the one given to pyrotechnics.
The Navy's tests are no small matter. Although key components of military aircraft, such as engines, fuel cells, and sophisticated onboard computers, have long been built with an eye toward surviving combat, the electrical wiring that links them has not. Under fire, Kapton wiring is an Achilles' heel in the military's most sop]isticated flying fortresses. A single bullet holds the potential to cripple, or even doom, the nation's most formidable fighting aircraft,
And it might not even take a bullet. For reasons still not fully understood, Kapton wires sometimes explode under the routine stress of peacetime flight. Though no deaths have been traced to the wiring, military documents obtained under the Freedom of Information Act show that it has become a suspect in a rash of inflight fires aboard both military and commercial planes as well as aboard the space shuttle Columbia. Exploding wires are listed as a possible factor in the crash of a navy jet in 1986 and in at least a dozen other cases in which military aircraft have faced a power loss or fire but managed to land safely. More than 100 other aircraft wire fires, both on and off the ground, have occurred under circumstances that bear striking similarities, military records suggest, but hard evidence to link them to Kapton is lacking.
The Navy has banned Kapton in new planes and in repairs to existing ones. The Army is moving toward a similar ban, and the Air Force has restricted its use. But what about the safety of the aircraft now in service? There are 400,000 miles of Kapton wire stuffed inside navy F-14s and F-18s, air force F-16s and B-IB bombers, army helicopters, and marine corps jump-jets. It is also the most popular wiring in commercial jetliners, and it can be found in intercontinental ballistic missites and nuclear power plants.
As early as 1982 the Navy's own safety experts claimed that Kapton fires were endangering its aircraft, but pilots were not warned. When the Naval Air Command moved to ban Kapton beginning in 1984, the pilots were informed but the public was kept in the dark. In 1987, when the Kapton controversy finally surfaced in news reports, army and air force spokesmen initially denied that the wiring was even a matter of concern. Military officials continue to drag their heels in finding a fix, even as wire fires account for an increasing number of damaged aircraft.
Limping into Lisbon
Wire types, distinguished by the insulations that cover them, underwent a transformation 20 years ago when Kapton came along. This insulation was thinner, lighter, and in many ways stronger than anything previously made. For its creator, E.I. DuPont de Nemours and Company, it became an overnight success story. It fit into the tightest of spaces in fighters, and its low weight saved precious fuel in the highly competitive commercial market. Moreover, DuPont touted Kapton as abrasion- and fire-resistant. And when it did burn, it emitted less smoke than other types-an important consideration for airline passenger compartments. Aircraft manufacturers, both military and civilian, hailed Kapton as a nearperfect insulator, and it became the mainstay of aircraft electrical systems.
But more recently, in tests and in the field, Kapton has been found susceptible to a phenomenon known as "flashover." Worn or otherwise damaged wires can produce an arc-a ribbon of current between exposed wires. Other widely used insulations also produce arcs, but only Kapton carbonizes from the arc's heat, instantly degrading into a charry, graphite-like material that is highly conductive. The char provides a path for the arc to spread to adjacent wires, creating a feeding frenzy of high-voltage arcing and fire that was described, even in the detached vernacular of the Navy's official reports, as "catastrophic." Eugene L. Kelsey, head of the aeronautical engineering branch at NASA's Langley Research Center in Hampton, Virginia, likened Kapton to a bomb ticking inside the bellies of countless U.S. aircraft. "Once an arc is applied to it. . . ," he said, "it is a potential small bomb."
DuPont, with annual Kapton sales estimated at more than $100 million, maintains that Kapton outperforms all competito!-s if properly installed and maintained. The company contends its product has become a scapegoat for fires resulting from sloppy repair work or poor aircraft design. Aircraft manufacturers tend to agree, saying evidence is insufficient to indicate that Kapton is inferior to any other insulation type.
Records show that when Kapton was introduced 20 years ago, it escaped the rigorous governmentsupervised testing required for other important aircraft materials. Unlike engines, radar, or flight control systems, electrical wiring was not considered a major component. Therefore, although revolutionary in design and untested in the field, Kapton was subjected only to the less-strenuous performance tests set in conjunction with industry representatives. These tests omitted such simple considerations as ease of maintenance, reaction to salt-water exposure, bending, and stress. The military's use of Kapton began in 1970, when the Navy installed it in its C-2 transport aircraft. In the commercial sector, Lockheed began using Kapton in 1972, in its L-1011 jetliners.
Almost as soon as the insulation was put into service, maintenance crews complained that Kapton was brittle and fragile, breaking easily when bent. Trans World Airlines reported 22 instances of wire fires or arcing on its fleet of 30 L-1011 jetliners between 1972 and 1981. The experience with Kapton left such a bad taste that a company official wrote Boeing in 1981 and asked that the insulation not be used on the Boeing 767 jets that TWA was planning to buy. Boeing refused, as have other U.S. aircraft manufacturers, defending Kapton's field performance. TWA bought the planes anyway.
Executives at Petroleum Helicopter Inc., a major Gulf Coast helicopter-leasing company headquartered in Louisiana, became so fed up with Kapton's breakage and corrosion that they lobbied Bell Helicopter Textron Inc. of Fort Worth to eliminate the insulation on business helicopters sold to the company"If handied with kid gloves in a laboratory environment, fine, but in the real world, where you're jerking engines in and out, . . .you don't have time to be playing games with something tender," said Harold Summers, the leasing company's maintenance vice president. He added that "the problems just almost went away" after Bell switched to an alternative wire made by a DuPont competitor, Raychem Corp. The insulation, known as Spec 55, is slightly heavier than Kapton. Bell officials defend Kapton, and the company continues to use it unless a buyer specifies a different wiring.
The most serious incident involving Kapton and commercial aircraft occurred in January 1985, when a wire fire temporarily knocked out the main power in a Boeing 757 packed with passengers 30,000 feet over the Atlantic. The aircraft, owned by Monarch Airlines of England and enroute from the Canary Islands to Luton, England, made an emergency landing in Lisbon, Portugal, and no injuries were reported. The fire erupted when alkaline toilet fluid leaked onto damaged Kapton wires, causing a flashover fire that destroyed power cables to both aircraft generators. The aircraft landed using backup power.
The potential for more serious Kapton problems captured the attention of Pete Kochis, a safety official at the Federal Aviation Administration assigned to monitor Kapton complaints. In an August 1986 memo to his superiors, obtained through the FOIA, Kochis wrote "it is conceivable that under the right conditions, this phenomena could impact the FAA in a fashion similar to the 'booster seal' experiences of NASA.'" It was a faulty O-ring booster seal, of course, that caused the explosion of NASA's space shuttle Challenger A higher FAA official, Leroy Keith, director of aircraft certification, described Kochis's comment as "over dramatic," and said the agency, though actively studying the problem, believes Kapton is safe in commercial aircraft.
The chafe-free video
The military has had far worse problems with Kapton. Military aircraft take more abuse, and the wiring is crammed into smaller spaces, which increases the chances of chafing. The problems first cropped up at sea, in the harsh aircraft-carrier operations of the Navy. For planes, the stress of carrierdeck takeoffs and landings has a bump-and-grind effect, causing the Kapton to rub against clamps and sometimes crack or break. And the salt air tends to degrade Kapton, leading to arcing and flashovers.
Within six to eight years of its introduction, according to navy reports, Kapton had become an ongoing maintenance headache and a potential safety threat. In June 1981, Rear Admiral Virgil Moore, then commander of the Navy's Pacific flight operations, wrote, "The incidence of wire chafing, recurring inspections, and fire hazards grows directly with the number of aircraft with Kapton wiring." The Navy Safety Center in Norfolk, which monitors accident reports, announced in 1982 that 25 fires had broken out on F-4 and RF-4 aircraft since 1979, four of them in the cockpits during flight. In messages to navy brass, the safety center concluded that repeated mishaps"not a problem until Kapton wire was introduced in 1979."
Nevertheless, navy aeronautical engineers tended to discount these early warnings, contending that sloppy maintenance and poor aircraft design were responsible for the problems, rather than the type of insulation used. A Pentagon group assembled at the Navy's request in 1982 to review Kapton problems reached a similar conclusion. The experts found it difficult to believe that any insulation could be reponsible for so many problems, several of them said recently. At the time, they said, they never would have believed that Kapton could explode. Quick fixes, such as rerouting wires, adding extra layers of insulation, and tutoring sailors on handling Kapton with more care, became the prescription of choice.
But fires continued to plague the fleet. The Navy's Air Logistics Center in Washington noted in 1982 that just as field engineers got a handle on one nagging problem, a new one would su"Evidence supports the Kapton wire as [a] contributing factor," the center argued in a communique to navy headqua"Intensified effort corrects existing failure but chafing fires occur in different areas."
The Air Force also looked for shortcuts to fix its wiring problems. Plagued by electrical fires in its frontline F-16 fighters, which contain ten miles of Kapton each, the service argued that better installation and maintenance was the key. In 1982 it undertook an $89 million revamping of the F-16's electrical system--a project given the rip-roaring name "Falcon Rally"-rerouting and reinforcing dozens of wire bundles. The Air Force formed special "chafing awareness teams," produced a video to alert crews to the dangers of chafing, and enacted 60 chafe-preventing changes in engineering.
Nevertheless, the most recent F-16 wiring study, completed by the Air Force in September 1986, found that while many of the chafing problems plaguing older F-16s had been fixed, they were resurfacing in newer planes. Fires continued to occur even on newly routed and better protected wires. Earlier this year, one air force base temporarily stopped washing its F-16s because the solvents were eating at the Kapton and starting fires as the jets prepared for takeoff. Reports from air force bases on the F-16 alone contain references to almost 50 electrical fires, both on the ground and in flight, between 1978 and 1986.
The $3 billion bill
The Air Force position is indicative of a stubborn resistance throughout the military, the FAA, NASA, and the aviation industry to publicly acknowledge the blotches on Kapton's report card. Even the Navy, which was the first to suspect a correlation between wire fires and Kapton, the first to document flashover in the laboratory, and the first to move toward a ban, won't acknowledge Kapton fires as a safety hazard.
While acknowledging that "we have had damaged airplanes" due to Kapton flashovers, David Pielmeier, the Navy's top wiring engineer, said the service banned it in new planes because of concerns it would explode in combat, not in peacetime use. With design changes, Pielmeier said, the potential for flashover fires during routine flight falls within "an acceptable envelope of risk."
To acknowledge Kapton as unsafe would be an admission by the service that most of its aircraft are unsafe-and therefore should be grounded. A similar admission by aircraft builders would invite hundreds of lawsuits.
It would also be expensive. The Navy has estimated that rewiring its fleet of 3,000 fighter planes alone would cost at least $3 billion. The estimate does not include another 2,000 nontactical navy aircraft, the 7,200 air force planes, or the 8,500 active army helicopters.
Instead, the military services and industry have embarked on a gradual course of change. They are rewriting wiring specifications to include flashover and ballistics tests. The Army has already outlawed Kapton for its next generation helicopter, dubbed LHX, and the Navy has done so for its secret new attack plane. Military sources say the Air Force is also planning a Kapton ban for its classified new Advanced Tactical Fighter.
But this inching forward could easily turn into a backslide. Top air force officials, faced with tremendous space constraints in the small, single-engine F-16s, have argued to defense procurement officials that no other insulation is compact enough to replace Kapton. Military sources say the Air Force will seek a waiver from the Pentagon to allow continued Kapton use in the 180 new F-16s that annually roll off the General Dynamics assembly line in Fort Worth. It's easy to see how such a waiver could spread.
Meanwhile, with enough Kapton in military aircraft alone to circle the world 13 times, critics contend that the potential for accidents is high. Classified navy documents show that a navy EA-6B jet plunged into the sea off the California coast on June 27, 1986. Two navy pilots ejected safely after a fire developed in the rear equipment compartment. The investigation found that a bundle of Kapton wires had arced and burned and that a nearby metal tank of highly flammable liquid oxygen had ruptured. The chief investigator cited "catastrophic failure of aircraft wiring" as a possible cause. The final navy report said the crash was caused by either a wiring failure or a rupture of the tank.
That same year, a frustrated navy squadron chief gave an aviator's perspective on the Kapton issue after an inflight fire forced an emergency landing by an AV-8B Harrier jump-jet. "A potential exists," the officer said in a report to his superiors, "with the subsequent shorting of the [Kapton] wires, for a future airborne, ground-refueling, or maintenancerelated accident to occur at any time if this problem is not rectified."
Military experts studying the problem say the question isn't whether such an accident will occur, but when.
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|Date:||Dec 1, 1988|
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