regulating generators

[torquey401]

AC 21-99 Aircraft Wiring and Bonding Sect 2 Chap 1

AluminiumWire
10. The use of aluminium wire for aircraft use is
quite limited and whenever replacement of an installed
wire is necessary, it may be advantageous to consider
copper wire with similar electrical/physical
characteristics. Currently there are no appropriate
specifications detailing aluminium wire suitable for
use in general aviation aircraft. Annex E to this
chapter provides details of MIL-W-7072 that was
cancelled in 1997. This information may be useful
when determining a suitable replacement wire.
NOTE
Aluminium wire may be used on new aircraft
designs and manufacturers information should
be used to maintain this type of wire.
Airframe Wire
11. Airframe wire is wire that is specifically
designed for use as component interconnection wire in
the airframe of aerospace vehicles. Airframe wire is
usually classed as normal or medium weight and has
two insulation coverings for protection against
abrasions. This type of wire should be used where a
secondary covering of insulation material is not
required. The M22759/34 (tin plated, 150

[Colonel Sanders]

The use of aluminium wire for aircraft use is
quite limited and whenever replacement of an installed
wire is necessary, it may be advantageous to consider
copper wire with similar electrical/physical
characteristics

This seems abundantly clear and obvious to almost
all of us here.

High risk, low return. A fire in an aircraft is no trivial
matter, for those of us that actually operate them.

http://en.wikipedia.org/wiki/Swissair_Flight_111
http://en.wikipedia.org/wiki/Air_Canada_Flight_797

Canada's objectively greatest fighter pilot of the
last 95 years was killed by ... a fire in an airplane.
He was, by all accounts, not exactly bashful. It
would be nice if he could discuss the importance
of fire in an airplane with the clerk types here.

The clerk types will viciously attack me for this,
but if Don Cameron's experience could teach you
something, it would be this:

Don't reset circuit breakers

A lot of time, when circuit breakers trip, it's because
they've gotten old, and they won't carry their rated
current any more.

However, if the breaker is NOT defective, it is doing
it's job. And when you reset it, you are putting
current into something that's doing something
very, very bad (short, arcing) and could very well
cause a fire.

http://www.aopa.org/asf/asfarticles/2009/sp0905.html

[photofly]

Currently there are no appropriate
specifications detailing aluminium wire suitable for
use in general aviation aircraft. Annex E to this
chapter provides details of MIL-W-7072 that was
cancelled in 1997.

Do you mean to say that when I contact Airbus to ask them to supply the aluminium wire to replace the old stuff in my Cessna there isn't a specification they can work to?

I guess it's back to Spruce, after all.

[NeverBlue]

Neverblue, check Wikipedia.

ahhhh...now I understand why you explain things the way you do

[photofly]

CID, I have to ask you. Do you write from the perspective of one who maintains heavy jets (either from a hangar or from a desk)? Or are you actually responsible for maintenance of any light aircraft?

[CID]

A few years back, the Australian airworthiness authorities felt that they should slowly wean themselves from the FAA and come up with their own standards, guidance and policy. This was in part due to the increase of domestic aircraft production especially the GippsAero line which have good potential as international products.

The thinking there is that it's tough to design, certify and market an aircraft to foreign standards since they don't have control of those standards.

Anyway, a huge flurry of guidance material came out and a lot of it was "different". In this case, different often meant substandard. That's why the Australian authority has almost as many cancelled Advisory Circulars as they do active. A feat that's not so enviable considering the short time they've been produced.

So guidance material like the Australian AC 21-99 is not recognized by the FAA or EASA or Transport Canada as "specified" or "acceptable" data. The reasons? Much of the information isn't "stand-alone" enough. instead of directing things like which wires conforming to "MIL-W-22759" are suitable for protected or unprotected installation or which are not suitable at all for various reasons.

It also incorrectly implies that "cancelled" MIL specs are no longer usable. If that were the case, I think you'd be surprised by the number of common aircraft hardware, relays, wire, etc would be no longer usable. Just because the US military cancels a standard it doesn't mean it's no longer procurable or usable. It merely means that THEY are no longer maintaining the standard (changing it) or procuring it for their new designs. Also, just because it doesn't have a MIL spec, doesn't mean it can't be used. Many of the wiring products in Aircraft Spruce's catalog are not MIL spec'd. Of course a lot of it isn't legal for installation on aircraft but that's another story.

With respect to aluminum wire and MIL-W-7072, use should be limited to areas where possible PVC toxic fumes can't accumulate. AC 21-99 shouldn't even imply it "may" be used for new installations. But for replacing a power cable in a 150? Sure.

That of course doesn't mean you should actively remove all of the PVC wiring in a 1967 Cessna 150. If it did you'd be replacing ALL of the wiring. Just don't use PVC wiring for replacement.

It's interesting that the AC doesn't mention that MIL-W-5086 (copper wire in PVC) was also cancelled. It's wire specifically called up in CAR 3. That standard in place back when the 1967 Cessna was built. It's replacement, SAE-AS50861 can't be used in aircraft. MIL-W-7072 was not directly replaced. The type used today has improved thermal expansion properties. Don't take that information to imply that all copper wire is thermally stable. It's not. If you want thermally stable copper wire consider M22759/28 (SAE AS22759/28).

Speaking of thermal expansion, know what's worse that using the wrong connection stack up with aluminium wire ore copper wire? using copper wire with terminals made of tinned or plated brass alloys. Unless of course you like re-tightening connections every few months.

I'm well aware that my technical views on aluminum wire aren't popular here and that the trend among GA is towards seek and destroy waluminum wire but I still feel it's prudent to present facts, not fantasy. I've stated the advantages and disadvantages of using copper and aluminum and nothing has changed in that regard.

I hope that at least people take away from this discussion that there are standards that exist that define what wire types are approved and provide proper procedures for installation and maintenance. I wonder how many people have replaced alumium cables using the wrong hardware? If the wrong stack up is used or improper terminals or improper installation, wiring can cause corrosion, overheating and fire regardless of the type.

And although I'm impressed that someone is doing a little research on the material presented but I hope they take away from this discussion that just because it's a document about aircraft from an airworthiness authority, it doesn't mean it's relevant or usable in Canada to maintain Canadian registered aircraft.

A good little exercise to compare FAA AC 43.13 (an accepted standard) to Australian AC 21-99 (an unaccepted standard) and then think about the differences and why they are different.

[CID]

Colonel Sanders, you've taken this thread into yet another tangent. Neither of the aircraft accidents you reference had anything to do with aluminium wire. Or general aviation for that matter although I'm being scolded for refereing to Airbus and Boeing.

The wiring in question was copper in both cases. The Swissair disaster was caused by a combination of bad design, and poor material selection. (polymide and mylar). it's funny actually that the M22759 standard that the Aussies reference includes a few types with polymide insulation....

The bad design was in part connecting non-essential equipment (cabin IFE etc) to an essential bus which the AFM (correctly) instructs the flight crew to try a CB reset. The flightrew unfortunately were not aware that these non-essential loads were on that bus and could be causing the failure. The polymide insulated wire is prone to radial cracking and "hydrolization" which is a term that essentially means that water is allowed to touch the (copper) conductor and cause minor shorting which eventually produces carbon accumulations. Once the fire started in the clump of carbon, it spread quickly behind the interior panels along the mylar clad insulation blankets.

Again, nothing to do with aluminium wire.

The Air Canada disaster was due to seized lavatory motor that overheated and eventually caused a fire. The operating and design standards have since been improved immensely to prevent such a thing. In this case, I don't know what the AFM said at the time in regards to circuit breakers blowing for non-essential systems but these days there is a strict "don't attempt reset" policy.

Regardless....again, not related to aluminium wire. So it's odd that this entry is made at this juncture in the discussion.

As far as your advise regarding the resetting of circuit breakers, I think you need to temper that a little. First and foremost do what the AFM says. Second, if there is no AFM or placard instruction and you don't need the related system (it's not critical to the completion of the flight) then by all means do not attempt a reset. It would be silly (for example) not to try resetting the 5 Amp gear control CB on your electric gear King Air. The big one for the motor (of course) is in the belly and can't be resent in flight. (For a reason)

[xsbank]

Bombardier policy:
No resets
Unless, you are on the ground
You did it yourself
The QRH tells you to reset

[CID]

xsbank, do you mean Bombardier "Flight Test" protocol? It makes perfect sense to have that policy in a flight test program.

Colonel Sanders, I chose to remain anonymous on this forum. I don't speak on behalf of anyone or anything but myself. I chose not to disclose my employer or any personal information about myself.

[Colonel Sanders]

Plenty of aircraft have had perfect paper, and
it didn't work out so well for them:

http://en.wikipedia.org/wiki/Swissair_Flight_111
http://en.wikipedia.org/wiki/Alaska_Airlines_Flight_261

The list goes on, and on.

[GyvAir]

CID, I can't help but admire your composure in the face of the above behaviours.
I saw a post recently from a moderator suggesting that it might be time for some serious house cleaning on this forum. I'm tending to agree. I've seen posts on other aviation forums stating that AvCanada is hardly worth reading, due to the immaturity and low level of professionalism exhibited by many of its frequent posters setting the tone for the discussions.

[pelmet]

The Air Canada disaster was due to seized lavatory motor that overheated and eventually caused a fire. The operating and design standards have since been improved immensely to prevent such a thing. In this case, I don't know what the AFM said at the time in regards to circuit breakers blowing for non-essential systems but these days there is a strict "don't attempt reset" policy.

A couple of posters have mentioned the AC Cincinnati accident and how the resetting of CB's caused the accident. While these posters are bang-on about the dangers of doing this, if you take the time to read the report as I did several years ago, you will see that the NTSB concluded(based on the evidence) that there was already a fire in the aircraft prior to the resetting of the CB's and that the fire may have actually caused the CB tripping. As well, it could not be confirmed that the toilet flush motor was the cause and that it may have started in the garbage bin possibly due to a cigarette. There was no 100% confirmation of the source of the fire.

[CID]

pelmet, everything you said is true. I stand corrected. I was going from memory and only hit the high points. Regardless, it had nothing to do with aluminum wire.

Colonel Sanders,

I'm going to mostly ignore your requests because that would fall right into your little trap. I will however say that you are wrong. I have been involved in the aerospace industry in a few different roles and I am experienced in the subject matter I present.

I would also like to address your claim that "paper is not what makes airplanes safe." It does. Paperwork is required by the airworthiness standards and regulations. Besides the obvious, it foremost demonstrates that the person responsible (in whatever capacity) is willing to follow the regulations and that makes the airplane much safer than someone who is committed to NOT follow the rules.

You have not only shown an unwillingness to follow the regulations, you have demonstrated contempt for them not only in this forum but in the public record.

I won't bother mentioning the billions of flight hours safely flown over the years nor will I cherry pick from the majority of aircraft that crashed because they were maintained or operated dangerously or without regard for the regulations. To what end??

[photofly]

I'm going to mostly ignore your requests because that would fall right into your little trap.

It wasn't CS that asked - it was me. I have great respect for people that look after all kinds of airplanes, big and small. And I understand (I think) the value of paperwork in the process.

[CID]

photofly, yes but CS re-iterated and I know his intentions. I have no beef with you but I have made it my policy not to share any information that may personally expose me to blackmail, anonymous character assassination or identity theft. I highly recommend that to anyone else posting here.

Cheers

[CFR]

CID, I can't help but admire your composure in the face of the above behaviours.
I saw a post recently from a moderator suggesting that it might be time for some serious house cleaning on this forum. I'm tending to agree. I've seen posts on other aviation forums stating that AvCanada is hardly worth reading, due to the immaturity and low level of professionalism exhibited by many of its frequent posters setting the tone for the discussions.

+1

[triplese7en]

CID, I can't help but admire your composure in the face of the above behaviours.
I saw a post recently from a moderator suggesting that it might be time for some serious house cleaning on this forum. I'm tending to agree. I've seen posts on other aviation forums stating that AvCanada is hardly worth reading, due to the immaturity and low level of professionalism exhibited by many of its frequent posters setting the tone for the discussions.

I'd like to add a +1 to this as well. I'm getting sick of coming to this site some days. Even though PPRUNE has their own share, it's nothing like what's on here.

[Son_of_dad]

CID, I can't help but admire your composure in the face of the above behaviours.
I saw a post recently from a moderator suggesting that it might be time for some serious house cleaning on this forum. I'm tending to agree. I've seen posts on other aviation forums stating that AvCanada is hardly worth reading, due to the immaturity and low level of professionalism exhibited by many of its frequent posters setting the tone for the discussions.

+3

[xsbank]

For the record, ALL Bombardier jets (don't know about the props).

[Beefitarian]

I've seen posts on other aviation forums stating that AvCanada is hardly worth reading,

Wow, sounds like that forum has a serious self esteem issue and can only feel better by telling you how their popular sibling isn't so cool.

My sister Gisele Bündchen has to shave her hairy back and picks her nose. She's not even worth talking to.

If their sparse Internet complaining is better than AvCanada's active discussions that's terrific. Then "Professionals" will have somewhere to go to read mature content.

[GyvAir]

Beefitarian.. There’s immaturity and then there’s immaturity. The delightfully tacky yet unrefined brand of immaturity you bring to this forum is good fun, and I would say generally welcomed by most here, including myself. The other kind of immaturity which I believe the posters I referred to were talking about, and what I’m talking about – the kind that makes you feel like you just ate some tainted meat when you read it – not so much welcomed. And yes, I stole some of the above verbage from a Hooter’s coaster.

[electair]

GA MX Trainer Dude

Merci beaucoup pour ton explication (gen reset system)

I WORK ON TWIN OTTER.
SYSTEM LOOK LAKE THE SAME

[trey kule]

I read this whole thread....what does that say about my Sunday mornings?

I liked McCrits post. Well written. Well thought out. And if you ignore the nit picking, I think it addressed the OP 's original question.

Thank you Mcrit....non illigitimus non carborendum...

[Pop n Fresh]

I like the beefeater, he seems like the sort of pilot I would lend an airplane to.