How "secure" must wire bundles be?

[AAflyer]

So, I'm trying to get my wiring in shape by, first, determining where I need to clamp and/or zip-tie. one of my questions is; why is it "OK" for a bunch of wires to bounce around in a conduit, but its NOT OK for that same wire bundle to rattle in a snap-bushing in a bulkhead. It seems, that as long as I've got that bundle secured in such a way that it can't be pulled back and forth across the snap bushing, then it should be OK to dispense with the often adopted "bracket and adel clamp" procedure…especially if the bundle has another layer of protection, like spiral wrap or short rubber sleeve.
Specifically, the bundles going through my main spar box…multiple holes, each with snap bushings…do I REALLY need to install a clamp on both sides of my spar at all these holes?? I really HATE drilling into my spar.
Can some of you DAR's tell me what would pass YOUR inspections…?

[Veetail88]

I'm NOT and A&P or anything like that so consider that in my response.

My understanding and the general guidelines I used for my build are as follows.

1. Wires should be secured in position so that they don't shift or flop around which could chafe them and cause shorts or contact with something they shouldn't.

2. Bundle the wires as much as possible. A single wire tends to vibrate which could break strands.

3. Keep them as neat as possible and out of the way so nothing can get caught on or damage them.

4. Don't install any wires in tension.

5. Protect wires and bundles where they penetrate holes. Use bushings etc.

I kind of saw this as a common sense and judgement sort of thing. Making wire runs and bundles extremely neat is not an easy thing to do. Just do your best.

Also, as long as the hole edges are protected, I can't imagine you would need to clamp on each side of the spar.

[Bill.Peyton]

If you have not already, check with this document AC 43.13-1B. I think if you google it you may find a downloadable copy. PM me if you can't.

[AAflyer]

Originally Posted by Bill.Peyton

If you have not already, check with this document AC 43.13-1B. I think if you google it you may find a downloadable copy. PM me if you can't.

Thanks, Bill,
I realize 43.13 is the Bible of "How do I..", but was hoping for a "practical, real life answer to quell my doubts…
The following pretty much sums up my gut feelings for, what, essentially, our parents used to say: "Don't ask me…Look IT UP!"

PROPOSED FEDERAL AVIATION REGULATION ACT

1000.A No pilot or pilots, or person or persons acting on the direction or suggestion or supervision of the pilot or pilots may try, or attempt to try or make or make attempt to try to comprehend or understand any or all, in whole or in part of the herein mentioned Federal Aviation Regulations, except as authorized by the Administrator or an agent appointed by, or inspected by the Administrator.

1000.B If the pilot, or group of associated pilots becomes aware of, or realizes, or detects, or discovers or finds that he, or she, or they, are or have been beginning to understand the Federal Aviation Regulations, they must immediately, within three (3) days notify, in writing, the Administrator.

1000.C Upon receipt of the above mentioned notice of impending comprehension, the Administrator will immediately rewrite the Federal Aviation Regulations in such a manner as to eliminate any further comprehension hazards.

1000.D The Administrator may, at his or her option, require the offending pilot, or pilots, to attend remedial instruction in Federal Aviation Regulations until such time that the pilot is too confused to be capable of understanding anything.

[Bill.Peyton]

Too funny

In reality, you should not allow wires to chafe on against themselves or any part of the structure. A cable tie every 6 inches on long runs is advisable. Where the wires pass through a small hole, use a snap bushing or caterpillar bushing around the edge of larger holes. Sometimes just bundling the wires together creates some rigidity and reduces the susceptibility for the wires to vibrate and chafe. You should not need to install clamps on either side of the snap bushings if the wires are bundled neatly and either laced of cable tied together. Just use common sense.

[AAflyer]

Thanks again, Bill.
I'm pretty sure that I've got enough 'common sense'…it's the inspector I'm worried about.

[PIN 37]

1000.A No pilot or pilots, or person or persons acting on the direction or suggestion or supervision of the pilot or pilots may try, or attempt to try or make or make attempt to try to comprehend or understand any or all, in whole or in part of the herein mentioned Federal Aviation Regulations, except as authorized by the Administrator or an agent appointed by, or inspected by the Administrator.

1000.B If the pilot, or group of associated pilots becomes aware of, or realizes, or detects, or discovers or finds that he, or she, or they, are or have been beginning to understand the Federal Aviation Regulations, they must immediately, within three (3) days notify, in writing, the Administrator.

1000.C Upon receipt of the above mentioned notice of impending comprehension, the Administrator will immediately rewrite the Federal Aviation Regulations in such a manner as to eliminate any further comprehension hazards.

1000.D The Administrator may, at his or her option, require the offending pilot, or pilots, to attend remedial instruction in Federal Aviation Regulations until such time that the pilot is too confused to be capable of understanding anything.

Ha Ha, that is nothing compared with regulations written by the Australian CASA( civil aviation safety authority) There are other interpretations of those letters, but would not be appropriate to put on here.

[RVDan]

The main goal in securing wiring is reliability over the life of the aircraft. To that end, most failures occur at connectors and from wear (riding conditions). Bundling wiring adjacent to connectors and supporting relieves loading at the termination, and prevents vibration from fatiguing the wire at the connection. Securing wires in bundles reduces the exposure of single wires to loads from people and such when the wire is disturbed during maintenance. The wire bundle is also stiffer and less likely to vibrate. Vibration leads to wire fatigue and chafing.

If you want more details try mil-w-5088 available on the web. It was the original document AC43-13-1B text came from.

[PIN 37]

It is interesting to note, that Bill has beautifully prepared wiring, but has not prepared the airframe against corrosion, that is, there is no priming or alodining of parts, curious, thats all

[Bill.Peyton]

Now Now.... Let's not start a primer discussion in this thread Actually everything was wash primed followed by light grey primer.