Kapton Wiring

[carlstone]

Hi All,

I was watching a video the other day when I had recorded something off the TV and I caught the end of a program on the tape which must have been recorded sometime before.

What it concerned was “Kapton Wiring” (I think that’s how its spelt!).

The program was highlighting some of the concerns about aircraft using this type of wiring insulation.

According to the report several aircraft, both military and civilian have been lost due to wires chaffing and then exploding causing the aircraft to lose control of its systems and crash.

The program then went on to describe how the RAF and US Marine Corps use Kapton wiring in the Harrier GR7 and AV-8B.

After an investigation by the RAF they didn't seem concerned about this problem and still use it to this day!

Is this true? Do the RAF use aircraft with wires that could explode at any time, or was the program over exaggerating the problem.

[Sven Sixtoo]

Facts:

Kapton wiring has been used extensively. Kapton has extremely good insulating properties for its weight.

The RAF has a vey low incidence of aircraft exploding at random.

Media organisations are frequently accused of reporting the sensational bits and leaving the boring bits out.

Since the deriving of the conclusion is usually left to the student, please submit a short statistical analysis comparing the reliability of press reports with the incidence of unexplained military aircraft losses, and express a conclusion in your own words. <img src="wink.gif" border="0">

[Sven Sixtoo]

PS . .Chaffing is what the last post was attempting.

Wires chafe.

[ 23 January 2002: Message edited by: Sven Sixtoo ]</p>

[kbf1]

There was some speculation that TWA Flt 800 that went in over New York was brough down by faulty Kapton Wiring overheating in the air con units that sit just above the center fuel tanks. The programme suggested that TWA 800 was flying a medium-haul route that did not require all of the tanks being fuelled, and that the wing tanks had been selected by the Flt Eng for ballast purposes. The resulting empty centre tank contained a high volume of volatile kerosene vapour which was heated to ca 400 degrees C by the air con units and sparked by faulty Kapton wiring.

I am not sure of the findings of the NTSB, and am not sure if a final report has been published on TWA 800, so it may be mere speculations. What is for certain is a degree of concern over the degradation of Kapton wiring that was installed in early Boeing 747s and aircraft manufactured in the late 60s and early 70s.

[HalesAndPace]

Try a search for "Kapton" in the Tech Log forum in particular, it has several useful threads.

Kapton wiring has very good qualities as far as an aircraft designer is concerned, especially as it could/can be used in higher temperature zones than other similar wiring. Also, the weight of wire insulation was/is a lot lighter than other types. So, lots more to the problem than a mere media story can tell!

[the funky munky]

Ageing wiring in aircraft one of my favourite soapbox subjects. . .Kapton carbon arc tracking in looms is no laughing matter, for those who don't know this is where a wire catches light in a loom bundle and burns the loom completely without any other source of ignition, even if you do pull the breakers. . .This fault is usually caused by chafeing and is made worse in damp areas but also a fault of bad installation. My belief is that some airframes will need a rewire just to maintain their airworthiness (look at Hawk re-airframing).. .Know for a fact that lots of cabs built in Zummerzet have got it, but it won't be fitted any more during modification action.. .There rant over. I do so enjoy this therapy, who wants the soapbox next?

[Blacksheep]

I've posted elsewhere on Kapton wiring, briefly, just like other things in aircraft engineering, electrical wiring needs proper maintainance. Providing the published procedures are adhered to, the advantages of Kapton wiring far outweigh the disadvantages. So, you can either use other types of wire that emit poisonous vapours when exposed to heat, or you can continue to use Kapton and make sure that it doesn't deteriorate in service.

Meanwhile, reliable data from the First World War indicates that eating large quantities of military issue Haggis causes the knee caps to explode. Fortunately this is easily prevented by keeping the knees cool, preventing them reaching combustible temperature. Hence the interesting attire worn by all ranks serving in the Highland regiments. And what has this to do with exploding wires you may well ask? Just try getting those Highlanders to give up eating Haggis...

**********************************. .Through difficulties to the cinema