MIL-DTL-22759/86A 1

[davesaudio]

I somehow ended up as a liaison ( for lack of better words) between engineering groups working on approval of a device carried in aircraft.
The folks that I would expected to know do not seem to know/have flammability specs on MIL-DTL-22759/86A conductors, spec'd by someone long gone.
Where would I look? Electrical specs are plentiful as are many anecdotal statements about meeting FAR 25 etc but I have not seen anything concrete?
Suggestions appreciated.
Dave

 

[VEBill]

The manufacturer or vendor of the wire would typically have an engineer available to provide you with any information and technical support required. They're typically very generous with their time, perhaps (in some cases) because they aren't that busy. Typically the amount of detailed knowledge of such product support engineers is amazing.

If you're on your own, then find the spec sheet for the wires in question (which you really must have if it's used in avionics), and then confirm the insulation material(s) is (are) of the required type.

If you find any mention of Kapton, then review the controversy on that material.

From memory, I believe we tend to use FTPE, but that's just a vague memory. Other people are the wiring SMEs.

 

[WKTaylor]

davesaudio

http://quicksearch.dla.mil/

Search for document # MIL-DTL-22759/86

The following is returned...

[COLOR=]MIL-DTL-22759/86A[/color] NOTE 1 C 6145 08-Dec-2004 Wire, Electrical, Polytetrafluoroethylene/Polyimide Insulated, Normal Weight, Silver Coated, Copper Conductor, 200 Deg. C, 600 Volts (S/S by SAE AS22759/86)

Click on the spec highlighted by underscoring and colored font.

The following window brings-up the base document, Rev A and NOTICE 1 cancellation [spec replaced by SAE AS22759/89].

NOTE. EVEN THOUGH THE MIL-DTL-22759/86 SPEC IS CANCELED AND REPLACED BY THE SAE AS22759/86, THERE ARE NO SIGNIFICANT DIFFERENCES IN TECH DETAILS... HENCE THE DATA IN THE MIL-DTL REMAINS VALID. I suspect that the wire can be easily procured under either spec.

NOTE. SAE will sell you the noted datasheet for a small fee... however, why bother, for obvious reasons!!???

Regards, Wil Taylor

o Trust - But Verify!
o We believe to be true what we prefer to be true.
o For those who believe, no proof is required; for those who cannot believe, no proof is possible.
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion"]
o Learn the rules like a pro, so you can break them like an artist. [Picasso]

 

[Sparweb]

I once had a project held up by this, temporarily. I'm sorry I can't remember the details. The airworthiness official at Transport Canada had expressed a concern at the time, about failures of a certain type of 22759/?? wire to pass 45 degree burn tests specified in FAR 25.853/Appendix F. I do not remember which.
All I do remember from that experience (10 years ago) was that you can't take this stuff for granted. We got the project done by specifying a different type of wire. Once you look at the 22759 specs, as Wil has already suggested, you will find a VERY wide variety of wire types, and it's essentially the jacket material that must be shown to pass flammability tests, but there are many jacket types. Since the MIL spec doesn't actually call up the FAR 853 tests, there is no guarantee that any particular wire type passes the test. But, in practice, almost all of them do.


STF

 

[kontiki99]

I'm not sure I understand the question. I work in a service environment, typically people ask me for alternate wire types.

MS22759 is a family of wires the /XX defines the specific characteristics.

Wire has to be suitable for the environment and electrical load and possibly strength characteristics. The metallurgy of the wire, suitability of the insulation, and sometimes assembly methods (solder vs. crimp) need to be considered. Some insulation types are more abrasion resistant but are easily cut and so forth.

There are guidelines in FAA AC 43-13-1B and SAE AS50881 for selection of wire. It's sized to accommodate nominal voltage drop and ensure the head build up (ambient plus restive heating) does not allow the wire to reach design temp.

The easiest substitutions are same wire one size larger AWG or with same insulation but thicker (if they fit). Or you can go to higher temp metal, but some, like nickel coated copper, require special soldering practices, but crimp just fine.

My posts reflect my personal views and are not in any way endorsed or approved by any organization I'm professionally affiliated with.

 

[Sparweb]

Hi Kontiki,
The OP's question about flammability has more to do with the jacket becoming part of an EXISTING fire.
It's not as much about starting a fire, if the wire overheats. There are circuit breakers for that.
Consider the differences in these environments: Engine nacelle, wet wing, avionics bay, cargo bay... Each has its own set of rule where materials must not start nor propagate fires.
The existing fire can, of course, be started by electrical faults, but the insulation of the rest of the wires in the bundle must not be a ready fuel.

STF

 

[kontiki99]

Insulation temp resistance and flammability are characteristics commonly identified in a lot of wire specs. I'd guess wire types typically used on engine fire detection loops are probably what you are looking for. It's out there. I haven't personally looked any of those specs up. Wires are installed on everything and every where.

My posts reflect my personal views and are not in any way endorsed or approved by any organization I'm professionally affiliated with.

 

[dgapilot]

From the base document, does this help?

Flammability: Test in accordance with MIL-STD-2223 method 1006 Procedure A
Requirements:
Duration of after-flame 3 seconds (max)
Flame travel 3.0 inches (max)
No flaming of tissue