Why Jets Fall From The Sky

This transcript is being reproduced because of its great contribution to aviation safety. Sadly the websites containing transcripts are being lost. It is not easy to find the work of these fearless journalists and their interviewees.

By Tom Mangold and Tim Clark


11 July 1999

Original Website:

NOTE: Tom Mangold & Tim Clark were involved with the producuction of the 1999 BBC Panorama TV documentary about the dangers of Kapton called 'DEATH BY WIRE'.


John Sampson, a self-professed fatalist, has few worries about the unknown - except flying. He selects his airline not just on its safety records, but on the status of the life-blood of the aircraft: hundreds of kilometres of delicate, bundled electric wiring that critics say has cost hundreds of lives in aviation disasters.

The critics say that as planes age the wiring threatens greater catastrophes.

The problem for Mr Sampson, the Perth-based Australasian representative of the International Aviation Safety Association (IASA) is that his choice is limited. A significant percentage of commercial passenger aircraft carry Kapton wiring, which ideally, says Mr Sampson, should be ripped out, as it has been from military inventories because of a series of crashes.

Kapton - the aromatic polyimide wiring insulation around the wire strands - has no place, he says, in passenger-carrying aircraft. He says that the main reason is that, in an electrical short, the wiring insulation chars to a conductive carbon residue and ignites like a dynamite fuse, affecting the whole wiring bundle (and therefore many disassociated systems).

The phenomenon is known as arc tracking. Because the outer carbon char (and not the internal wire-core conductor) is then carrying the current, the circuit breakers most probably will not trip. There is therefore nothing to halt this "flashover" because the power stays on the wire. The older the Kapton wiring gets, the more brittle and vulnerable the insulation becomes.

"The wiring clearly is not safe," he says. "There is always a risk in aviation, but this stuff makes it tangibly worse."

So, when he travels, Mr Sampson does the best he can by opting for carriers with good service records, maintenance and crew training procedures, such as the Australian carriers, rather than add to the risk by flying with a carrier that might do maintenance on the cheap and is less likely to detect frayed Kapton wiring that could well bring down a plane. "It's the rubber band analogy. One weak point in the hundreds of kilometres of inaccessible wire. That is all it takes."

Mr Sampson liaises with aviation industry insiders and experts around the world who provide crucial information to IASA on incidents that could be attributed to the wiring and on research into its safety.

The Civil Aviation Safety Authority and Qantas and Ansett - most of the airlines' fleets have Kapton - say there is no evidence the wiring is dangerous or has caused aviation accidents.

But Mr Sampson says aviation authorities will have trouble denying the dangers of Kapton after an expose of the material and its dangerous history is screened tomorrow by the BBC's Panorama program. It will show that, under certain conditions, the aircraft wire can explode, causing fires inside the plane.

The insulation on the wiring is the main focus of the investigation into last year's Swissair disaster over Canada when 229 crew and passengers plunged to their deaths.

Panorama has also established that Kapton wiring was at the heart of the world's sixth-worst air disaster (still officially unsolved) when 301 passengers were burnt to death. Kapton insulated wire is also suspected of involvement in several other aircraft disasters and near mishaps.

Although the United States Navy has banned Kapton and the insulation is no longer used by Boeing since 1992, the world's largest planemaker Airbus Industrie continue to use a version of it in their new planes. Even though the British CAA (Civil Aviation Authority) has forbidden the use of Kapton insulation in new aircraft designs, a loophole allows it to be used in current designs.

Despite ample warning about its dangers, the Royal Air Force took delivery of Kapton-wired Harrier GR5s. Two crashed because of the wire before the RAF embarked on a program to modify the use of Kapton in all the vulnerable parts of their planes.

British Airways admit they use Kapton widely in their aircraft, but that its use meets the requirements of regulatory authorities. Panorama understands, however, that British Airways was warned of the dangers of Kapton insulation and did make its concerns known to Boeing, its principal supplier. BA has declined to confirm or deny this.

Kapton insulation (a DuPont trade name, although their patent has now expired and they are no longer the sole manufacturers) seemed to be the dream wire insulation for commercial and military fleets in the 1970s and '80s. Wiring is like a plane's blood vessels, and the average big jet carries up to 250 kilometres of it. When the giant aircraft manufacturers were looking for something extremely light, tough and flame resistant they settled for Dupont's Kapton. Boeing, McDonnell Douglas, Lockheed and later Airbus Industrie all installed it in good faith in their models during the '70s and '80s. Today, 40 per cent of all planes still carry Kapton-insulated wiring.

But in the early eighties, a US naval captain discovered an obscure Soviet technical publication, 10 years old, which analysed Kapton (technically an aromatic polyimide). The publication noted that the insulation decomposed when in contact with concentrated alkali but, more chillingly, the insulation was hydrolitic - it absorbed water. The report also mentioned Kapton's tendency to arc.

The US Navy, already alarmed at a rash of wire failures and unexplained flash fires in its fighter planes commissioned detailed tests of Kapton. These were conducted by Bob Dunham, its top civilian expert on aircraft wiring. Dunham's tests revealed a terrible truth about the now widely installed insulation. Kapton's positive aspects were heavily outweighed by its uniquely negative qualities. Its strength was negated by the fact that it had "straight line memory". It always wanted to return to its original position when on a wire drum. This meant that unless it was properly and frequently imprisoned in clamps it had a tendency to "roam" and subsequently chafe. Its ultra-light weight (only three and a half human hairs thick) was a huge commercial advantage, saving precious weight on the plane. But when the insulation wore through and the naked wire touched metal, it arced at 6000 degrees, and before short circuiting it flashed like a tiny banger firework.

Dunham's experiments then discovered that when the short circuit tripped the circuit breaker (fuse box) in the plane, once the breaker was re-set and the power restored to the wire, a new flame ran along the Kapton insulation, turning it into a charred flame conductor. In this way, fire spread along the path of the plane's wires.

Dunham, who videoed the tests, was appalled. So was the US Navy. By 1987, it had mothballed many of its Kapton-wired planes and unceremoniously banned Kapton.

By now, Kapton had been widely installed in civilian airliners, and the industry comforted itself by claiming that military planes underwent unusual stresses that were inapplicable to their civilian counterparts.

Dunham led a US Navy team to the British for a demonstration in Farnborough. RAF and CAA officials were stunned when the Kapton wire bundles exploded, and then arc tracked.

Nevertheless, for reasons that remain obscure, the joint British-American Harrier program with Kapton wiring still went ahead. Two Harriers crashed because of the Kapton effect. An RAF Tri-Star on the ground also was damaged when Kapton wiring suddenly exploded.

Kapton wiring is now at the centre of the Swissair 111 crash investigation. Detectives of the Canadian Transportation Safety Board are interested only in what's been recovered from the sea off the front nine metres of the plane. The theory is that Kapton wire, with other cables running above the pilot's head in the cockpit, caught fire, that the wires arc tracked, and burnt, melting plastic and aluminum above the pilot's seat (molten metal was found on the sheepskin covering) and that the fire spread beyond control destroying key aircraft systems.

Now the Swissair crash investigation may finally focus attention on the truth about Kapton, which has remained hidden by an airline industry in denial.

A FAMILIAR face sits quietly on a park bench in New York. Jake La Motta "Raging Bull", former world middle-weight champion is now 77. He once had two sons. The first died of cancer, the second died in Swissair 111. La Motta has little to say about the tragedy. "What would I have told him if I knew I would never see him again?" For a moment, the emotion overwhelms him. "I would have said, `I love you son, I love you so much'."

But there was no formal goodbye. There rarely is. The dead are at peace, the relatives live on in turmoil.

But for the planemakers and the airlines, the Kapton problem remains complex. Kapton cannot be replaced in a large civilian jet (unlike a small military one); it would be cheaper to buy a new plane. No aircraft wire can be fully accessed by maintenance engineers or independent inspectors because, like blood vessels it is hidden deep in the skeleton and fabric of the plane. At most, 10 per cent of the wire can be inspected by human eyeball, and even then, it should be done properly with a 20X magnifying glass to expose the first tiny and potentially deadly nicks and abrasions. But to inspect all the wire with such thoroughness is simply not on from a commercial point of view.

The man who has single-handedly dragged the wiring problem to the industry's front burner is a quiet, self-effacing Philadelphian, Ed Block. For 10 years, he was the Pentagon's chief wiring expert, saw the dangers, not only of Kapton but other insulations, blew the whistle and was fired for his pains. Block has since become one of America's top private wiring consultants, the scourge of the aircraft industry, but so well-regarded that even the governmental commission now finally looking at aircraft wiring problems has been forced to co-opt him to one of its working committees.

"The problem for manufacturers like Boeing is that they are stuck with Kapton. If they were to admit there was a wiring problem in their planes the implications would be devastating. There would be huge liability and credibility issues, that's one reason why they cannot fundamentally admit the problem because they cannot fix it.

"The whole industry is in a state of denial, admit the problem and we are talking about a crisis of confidence in flying that no one can face. It's as simple as that."

Nor have the governmental safety and regulatory authorities pointed the way out of the dilemma. If anything, they have tended to find common interest with the industry they should regulate. The American FAA (Federal Aviation Administration) refused to talk to Panorama as did its British equivalent the CAA. Both agencies have refused to acknowledge the dangers of Kapton, claiming that "wire is wire", which is rather like saying wine is wine.

Even before the US Navy was confronting the Kapton problem, the first known commercial problems with Kapton were occurring in the early '70s and were spotted by a civilian engineer - the "Mr Wire" of American airline TWA.

Bill Gaspar, now retired, was never comfortable with the new wire that Lockheed was about to install in TWA's fleet of Tri-stars (L1011s).

In the late '60s, Gaspar conducted a low-science experiment in his kitchen. He "cooked" the Kapton in the oven to prematurely age it, then he nicked it, wound it round a nail and inserted it into a mug of water heated to 200 degrees (the operating temperature of the wire). He was appalled at what he saw. "The nick propagated in a very horrible way," he recalls, "it opened up quite dramatically. At the time, I told my wife that 20 years from now this could really become a problem."

In fact, it was only to take six years.

In 1972, one of Gaspar's TWA Tri-stars had a catastrophic wire failure; severe arcing guillotined a wire bundle. Gaspar drew Lockheed's attention to the problem.

Shortly after this, the same failure occurred on the same plane in the same way. Another letter to Lockheed. Gaspar recalls the reply. "They said it's a wire that's accepted by the rest of the industry. It's widely used and perhaps (TWA) is being somewhat sensitive about such a failure."

Gaspar felt there were more Kapton wiring cases than the industry realised. He discovered that serious aircraft incidents involving wiring were usually reported in a way that identified the system that failed because of wiring rather than the wiring itself. This created misleading databases. So if the lights went out, it was a lighting problem and not a wiring problem. Gaspar spoke to his friends in the field - within months he'd struck pay dirt. He unearthed 22 Kapton wiring problems with Tri-stars alone in a nine-year period.

Gaspar drafted a letter for his boss to send to Boeing. He first outlined all the problems TWA had experienced with Kapton then came the crunch: "Because of Kapton's (minus factors) we will strongly object to any proposed use of this wire on future TWA aircraft."

United Airlines, another giant US carrier, wrote a similar letter at the same time.

But Boeing talked both airlines out of their fears.

Gaspar recalls: "When my kitchen experiments with Kapton were mentioned Boeing came back saying, "We don't fly our aeroplanes through boiling water."'

The more likely commercial reality is that neither TWA nor United were then in the position to twist Boeing's arms. The planes were on order, they were being made, this was not the time to pull out of a multi-billion-dollar contract.

Boeing has either built or acquired (through its acquisition of McDonnell Douglas) over 90 per cent of planes flying today. Their corporate view about Kapton is very simple. "There is no Kapton problem."

By 1992, Boeing was out of Kapton and into its new and safe TKT, a Kapton insulation wrapped in a teflon "sandwich" with which there have been no major recorded problems.

However, flying still remains extremely safe. The chances of death or injury in a plane disaster were, in 1998, one in 1.5 million . But as more planes take to the sky, the odds will change dramatically, the more so as wiring ages.

In 1988, after the US Navy had banned Kapton and after it was becoming clear that the Kapton infection had spread to civilian airliners the FAA finally conducted its own tests on the wire. Only a decade behind Gaspar in the commercial realm, and five years behind the US Navy, the agency finally discovered that Kapton arc tracking "formed a conductive char upon thermal degredation and severe arc tracking occurred".

Furthermore, "extensive damage to all wires in the bundle occurred due to arc tracking propagation upon circuit breaker re-setting". In comparative tests, every sample of Kapton showed "massive arcing, arc tracking and severe re-arcing when the circuit breakers were re-set".

The FAA established a similar problem with wet arcing when water or solvent dripped on the insulator. The work fully vindicated Gaspar's and Dunham's pioneering studies. Yet this information resulted in only an advisory circular being issued by the FAA in 1991 about the dangers of resetting Kapton wired circuit breakers. Where the FAA did issue warnings, they were usually carefully coded and usually omitted the word Kapton.

Panorama has examined a list of air disasters and near disasters involving Kapton-wired planes.

14 January 1985. A British Monarch Airlines Boeing 757, on a flight from the Canary Islands to Luton has a serious wire bundle explosion. Smoke begins to enter the passenger cabin. The pilot manages to make a forced landing in Portugal. A subsequent investigation shows that "loo-blue" dripped on to Kapton wiring beneath the lavatory. Wet arc tracking occurred and the bundle exploded.

10 January 1998. An American United Airlines Boeing 767 en route from Zurich to Washington makes an emergency landing at Heathrow and the passengers are safely evacuated by chute. The cabin crew reported smoke in the forward galley. Investigators subsequently found 36 wires were damaged by heat or fire.

5 November 1990. Philippine Airlines Boeing 737. As the plane is being pushed back for flight there is an explosion in the fuel tank "probably" from faulty wiring creating a spark that ignited fuel vapor. Eight passengers died.

28 May 1996. A Dutch-registered Boeing 767 was forced to make an unscheduled landing at Boston following numerous electrical anomalies including false illuminated warning lights, false display indicators, uncommanded autopilot disconnects and failure of flight instruments.

17 March 1991. Delta Airlines. A fire breaks out in a Lockheed Tri-star en route from Frankfurt to Atlanta. The plane diverts to Goose Bay for an emergency landing. The "most probable" cause of the fire was electrical arcing in an electrical wire bundle under the cabin.

This is a short list. Panorama has investigated one further catastrophe - the world's sixth-worst air disaster in which 301 people were burnt to death. Our conclusions are that the evidence points beyond reasonable doubt that this was a classic Kapton-induced event.

On 19 August 1980, a Saudia (Saudi Arabian Airlines) Tri-star took off from Riyadh Airport for Jeddah. There was a a fire in the rear cargo compartment. The captain returned to Riyadh. Flames had broken through the cabin floor and the cabin was filling with smoke.

The plane landed at Riyadh and taxied to a halt. Minutes later, when firemen reached the plane they hacked their way in and found that everyone had died of smoke and flames.

During the subsequent investigation, Britain's top air crash investigator Eric Newton was invited by the Saudi authorities to help. Newton discovered Kapton wires, burnt out, the insulation destroyed. Some of the copper wires were fractured and the ends gave the impression of melting and possible electric arcing. He could find no other source for the ignition.

When Newton's report with its provisional conclusions was available in January 1982, the aviation world still didn't know just how lethal Kapton insulation could be. His report was filed and forgotten.

Following the Valujet crash in Florida last year, the Vice-President, Al Gore, has headed a special commission which has now formed a working group to determine the ageing effects on airplane wiring. Britain is to follow suit. However, the inspections of aircraft wiring will be non-intrusive - code for saying that the inspectors will not employ the expensive, time-consuming process of taking all the wiring out and examining it through magnifying glasses. (There is still no guaranteed mechanical way of doing this.)

The industry is starting to understand that the Kapton problem will not go away. Boeing and Airbus may yet find a way out of their dilemma if the Vice-President's commission (albeit packed with industry delegates) suddenly "discovers" what the industry and the military have known for years

Copyright © Fairfax Press 1999.