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1. 07:40 AM - Re: Aviation wire (Robert L. Nuckolls, III)
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| Subject: | Re: Aviation wire |
At 10:59 AM 5/23/2020, you wrote:
>
>Hello forum,
>
>Been rather quiet lately so I thought I would
>stir the pot with a relevant question on my project.
>
>I have always planned on restricting the wire on
>my plane to tefzel, mil spec from Steinair or
>BandC. I=99ve read and reread Bob=99s book and
>see his recommendation (in the text) is not
>restricted to this level but he has a clear
>process for using wire (or, more accurately,
>identifying if the wire is usable) of unknown pedigree.
Correct. There have been (and still are) tens of thousands
of airplanes flying for decades with a wide range of
wire insulations. Given that all fault-vulnerable wires
are protected with an artfully selected fuse or breaker,
insulations of any pedigree are not at risk for initiating
a fire due to feeder faults.
The remaining concerns for type of insulation are (1)
longevity when subject to the operating environment
which includes temperature, hydrocarbons, hydraulic
fluids . . . and just plain old age.
While 22759 Tefzel (FEP) is the modern material of choice
(I say 'modern' but it's been in widespread used on
the Wichita fleets for 40 or so years), those same
aircraft were manufactured back to the 40's with
a variety of insulations including, cotton covered
rubber, some of which are still carrying perfectly
serviceable wiring.
>I have a collection of single conductor and shielded wire that
>is all mil-w-16878D. Some is labeled as 200C and some with 105C
>temperature rating. None of the wire is below a strand configuration
>of 7/30.
You can see a table of characteristics for
the various forms of 16878 wire at
https://tinyurl.com/ydgex35d
Your 200C wire is Teflon (ETFE) insulated.
Not a 'bad' insulation but the stuff does
creep under constant pressure unlike the
preferred Tefzel (FEP). Just snug up
wire-ties and clamps . . . don't strangle
'em.
The infamous Greg Richter and I had some
discussion about Teflon wire about 16 years
ago . . . https://tinyurl.com/y8lf49dq
The 105C wire will be PVC insulated. A
generation of single engine Cessnas were
manufactured with type BN wire (Nylon over
PVC).
Yeah, didn't last well under the cowl (nylon
jacket got brittle and flaked off).
>The question is, =9Cshould I use this wire? Also, if used,
>should I restrict its use to the pilot side of the firewall?
The 200C wire is fine everywhere but yeah,
the 105C wire is best kept aft of the
firewall.
The Teflon wire is a bit fussy to strip.
See: https://tinyurl.com/bol9x2n
Bob . . .
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