propilot83
Posts: 618
Joined: Sat Jan 27, 2001 2:41 am

Kapton Wiring

Tue Jun 02, 2009 6:01 pm

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.
 
aviopic
Posts: 2423
Joined: Sat Mar 13, 2004 7:52 pm

RE: Kapton Wiring

Tue Jun 02, 2009 8:49 pm

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
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Kapton Wiring

Tue Jun 02, 2009 9:35 pm



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
 
soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: Kapton Wiring

Tue Jun 02, 2009 10:02 pm

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.
 
DL_Mech
Posts: 2061
Joined: Fri Feb 18, 2000 7:48 am

RE: Kapton Wiring

Wed Jun 03, 2009 1:06 am

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.
 
soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: Kapton Wiring

Wed Jun 03, 2009 12:46 pm



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?
 
aviopic
Posts: 2423
Joined: Sat Mar 13, 2004 7:52 pm

RE: Kapton Wiring

Wed Jun 03, 2009 9:54 pm



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
 
soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: Kapton Wiring

Wed Jun 03, 2009 11:01 pm



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
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Kapton Wiring

Thu Jun 04, 2009 12:11 am



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
 
soon7x7
Posts: 2267
Joined: Thu May 04, 2006 10:51 am

RE: Kapton Wiring

Thu Jun 04, 2009 1:04 am



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
 
aviopic
Posts: 2423
Joined: Sat Mar 13, 2004 7:52 pm

RE: Kapton Wiring

Thu Jun 04, 2009 8:04 pm

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
 
474218
Posts: 4510
Joined: Mon Oct 10, 2005 12:27 pm

RE: Kapton Wiring

Thu Jun 04, 2009 9:35 pm



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.
 
Okie
Posts: 3532
Joined: Wed Jul 16, 2003 11:30 am

RE: Kapton Wiring

Fri Jun 05, 2009 3:18 am



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

Who is online

Users browsing this forum: Baidu [Spider] and 8 guests