Beags, heard of this?
In the past Airbus has insisted its use of Kapton is safe, because it coats it in a thin layer of ‘FEP’ – fluorinated ethylene propylene – making it less likely to crack. But other experts disagree, and in 2008 the Federal Aviation Administration, America’s rule-making body, stated that even when coated with FEP, ‘Kapton wire insulation materials should not be used in airborne applications.’ But didn’t ban its use, aware perhaps that to do so would call into question the safety of any aircraft using Kapton – as many as 14,000 planes.
The introduction of fly-by-wire aircraft has furthered the frequency of these situations,’ he says. ‘But as with QF72, the anomalies often can’t be reproduced on the ground by maintenance personnel, because there the vibrations and humidity experienced in flight are no longer an issue.’
For four years from 1999, a special investigation group set up by the FAA stripped down six ageing passenger aircraft, including a Kapton-wired Airbus A300, the predecessor of the A330. It found widespread evidence of wire bundles that had become charred, cracked, brittle and prone to arcing, as well as contaminated by dust, lint and fluid from leaking toilets. Yet when its report was produced, the Bush White House took no action.
Arcing may not only cause fires or systems to fail: it can also lead to ‘uncommanded inputs’, such as the sudden plunges experienced by QF72.
There’s still no effective way to test wires’ integrity while they remain in use. Nasa would not have to be retiring the Space Shuttle fleet if there were a simple test. On the other hand, if there were a test, and it showed the Kapton in individual planes is dangerous, thousands of planes might have to be retired.’