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Kapton Wiring  
User currently offlinePropilot83 From United States of America, joined Jan 2001, 598 posts, RR: 0
Posted (5 years 3 months 1 day 15 hours ago) and read 5963 times:

After watching a documentary on Swiss Air Flight 111 that crashed over the coast of Nova Scotia back in 1998 if I am not mistaken, investigators found that electrical wiring of that aircraft was corroded and presented a hazard to the entire airframe. Kapton wiring was the problem not just for Swiss Air Flight 111, but for many different types of aircraft. The problem was that when there would be an electrical outage, and the pilots would reset the circuit breakers for that particular electrical equipment (i.e. flight management computer, etc.), the corroded Kapton wire would cause a huge spark big enough to cause a fire throughout the wiring and throughout the airframe. The NTSB performed several different tests on aircraft wiring, beginning with the Kapton wiring that was just the worse of all types. This Kapton wiring could have been a factor in the TWA-800 disaster as well as other in flight emergencies that caused smoke in the cabin. Kapton wiring was a major problem for almost every aircraft that was insulated with this type of wiring, so the FAA mandated changes to the electrical wiring of the aircraft that posed a deadly and hazardous threat.

12 replies: All unread, jump to last
 
User currently offlineAviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 42
Reply 1, posted (5 years 3 months 1 day 12 hours ago) and read 5926 times:

The conductor isn't kapton but the insulation is.
The advantage of kapton wiring is weight but it is very delicated and is very easy to damage.
We had to use special dedicated tooling like stippers etc.

If the conductor started to corrode it means that the insulation was damaged otherwise there would not have been a problem.



The truth lives in one’s mind, it doesn’t really exist
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 2, posted (5 years 3 months 1 day 11 hours ago) and read 5915 times:



Quoting Propilot83 (Thread starter):
Kapton wiring was a major problem for almost every aircraft that was insulated with this type of wiring, so the FAA mandated changes to the electrical wiring of the aircraft that posed a deadly and hazardous threat.

The FAA never mandated replacing Kapton insulated wire and it is still in use today. The US military did remove and replace it from some airframes.

The following is a short but informative article with a link to a much more detailed report:

http://www.newschannel5.com/Global/story.asp?S=8221414


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 3, posted (5 years 3 months 1 day 10 hours ago) and read 5905 times:

After the TWA 800 event I had been out in Tucson, AZ and climbed around inside the center fuel tank of EI-BED, an Aer Ligus 747. This was a 100 series. This aircraft was even older than N93119. Line # 44 (EI-BED), Line # 153 (N93119), I grabbed some of the Kapton wiring and bent it back, pretty much doubling it over on itself and the casing was as new as the day it was installed. Actually the entire inside of the tank virtually showed no evidence of its age. The oil in Kerosene serves well at keeping surfaces protected from age and corrosion.
Then I tried it on a 707 300 center tank...same thing...even the wire codes that were stamped into the casings were clearly evident...the 707 had to be 40 plus years old. All wiring on these planes were Kapton...As long as wire runs, wire clamps, gromits and other associated installation hardware were properly installed and in good shape, the wiring casings seemed just fine. Even wiring that had apparently been well exposed to the Arizona sun for a while seemed in relatively fine shape. My guess is that down the road during c, d checks when major maintenance had occurred, possibly new installations were not according to the book and new issues were created as a result.


User currently offlineDL_Mech From United States of America, joined Feb 2000, 1937 posts, RR: 9
Reply 4, posted (5 years 3 months 1 day 7 hours ago) and read 5876 times:

Quoting Soon7x7 (Reply 3):
I grabbed some of the Kapton wiring and bent it back, pretty much doubling it over on itself and the casing was as new as the day it was installed. Actually the entire inside of the tank virtually showed no evidence of its age.

Was the wiring white in color? If so, it might have been Poly-X. IIRC, the wiring in TW800 was Poly-X.

http://www.chicagotribune.com/topic/...6-crash1122,0,6433777.story?page=1


http://www.geocities.com/Eureka/Concourse/7349/wire.html

[Edited 2009-06-02 18:19:43]


This plane is built to withstand anything... except a bad pilot.
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 5, posted (5 years 3 months 20 hours ago) and read 5795 times:



Quoting DL_Mech (Reply 4):

It was identical to wiring I saw in the TWA800 wreckage...yes, it was white/biege...Was also the same wiring I saw in the brteak up of TWA N93107 and N93108 as these airframes were all procuced about the same time, 1970/71. Why would one ship be different than the other, other than the fact that Boeings vendor may have changed the wire stock...No?


User currently offlineAviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 42
Reply 6, posted (5 years 3 months 11 hours ago) and read 5715 times:



Quoting Soon7x7 (Reply 3):
I grabbed some of the Kapton wiring and bent it back, pretty much doubling it over on itself and the casing was as new as the day it was installed.

In my view that can't have been kapton.
Kapton insulation is very hard and cracks open if bend to much.
Also kapton is about 40 years on the market now and therefor the chance to find it in 707's or 741's are slim as it wasn't around at the time both a/c's were developed.
Of course it can be modified in at a later stage but that's not a common practice.

Quoting Soon7x7 (Reply 5):
yes, it was white/biege

Never seen kapton to turn beige, think you have seen a teflon(or variant) type of wiring.
This will color to beige and can be bend in any way without damage.
Apart from the toxic fumes when heated up I am still in favor of this type though.



The truth lives in one’s mind, it doesn’t really exist
User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 7, posted (5 years 3 months 10 hours ago) and read 5696 times:



Quoting Aviopic (Reply 6):

The two TWA ships, N93107, N93108 were same generation as N93119 (TWA 800). All three were 100 series.
The yellowing may have been due to sun exposure to the elements in AZ. I still have some down stairs...even have the low voltage fuel sensors...they have same wiring...j


User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 8, posted (5 years 3 months 8 hours ago) and read 5683 times:



Quoting Aviopic (Reply 6):
Never seen kapton to turn beige,



Quoting Soon7x7 (Reply 7):
The yellowing may have been due to sun exposure to the elements in AZ.

All the Kapton wire I have ever seen was this color:

http://www.chaparts.com/images/egun-connector.jpg


User currently offlineSoon7x7 From , joined Dec 1969, posts, RR:
Reply 9, posted (5 years 3 months 7 hours ago) and read 5660 times:



Quoting 474218 (Reply 8):

Thats the same product I got from the AZ 747's from the center tanks...nav light fixtures had white wiring...j


User currently offlineAviopic From Netherlands, joined Mar 2004, 2681 posts, RR: 42
Reply 10, posted (5 years 2 months 4 weeks 1 day 12 hours ago) and read 5602 times:

What you are looking at is the film wrap not the kapton.
I've read that this type was indeed used in the 741 and later version.
The fact remains that kapton is very fragile and not very resistant to mechanical stress which led to numerous incident's, just have a quick google on "kapton wiring".
In fact I had to repair several incidents myself just because someone bended it to much causing the insulation to crack and short with structure.

To counter the problem newer variant exists like teflon coated kapton for example.
Whether this is an improvement I do not know.



The truth lives in one’s mind, it doesn’t really exist
User currently offline474218 From United States of America, joined Oct 2005, 6340 posts, RR: 9
Reply 11, posted (5 years 2 months 4 weeks 1 day 11 hours ago) and read 5595 times:



Quoting Aviopic (Reply 10):
What you are looking at is the film wrap not the kapton.
I've read that this type was indeed used in the 741 and later version.
The fact remains that kapton is very fragile and not very resistant to mechanical stress which led to numerous incident's, just have a quick google on "kapton wiring".
In fact I had to repair several incidents myself just because someone bended it to much causing the insulation to crack and short with structure.

To counter the problem newer variant exists like teflon coated kapton for example.
Whether this is an improvement I do not know.

Kapton is the insulation (the yellow stuff in the picture) the wire inside is plain old copper wire.

Kapton is insulation much thinner and tougher than standard insulation but can be brittle.


User currently offlineOkie From United States of America, joined Jul 2003, 3010 posts, RR: 3
Reply 12, posted (5 years 2 months 4 weeks 1 day 5 hours ago) and read 5560 times:



Quoting Aviopic (Reply 10):
To counter the problem newer variant exists like teflon coated kapton for example.
Whether this is an improvement I do not know.

One of the other issues even with teflon coating on the kapton was the water absorsion of the kapton migrating up the wire.

In the industry I am in we use Tefzel which is a duPont trademark for ETFE by the truck load.
Tin coated stranded copper wire with a very thin extruded insulation carries a 1000v rating. I have never seen any color other than white but I suppose if you bought enough then they would make any color you would prefer. I also carries the green numbers down the length with Mil rating. I suspect this is or at least close to what is used in aircraft today. The insulation is about as tough as it comes and is flexible.

Okie


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