Magneto questions

bnt83 said:
So wouldn't that be normal wear? Spark plugs wear too...

I've never seen distributor wear limits in either manufacturer's manuals, must be a "use good judgment" thing.
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If the inspection criteria spells out "wear" but doesn't supply any "wear limits", wouldn't any noticeable wear be cause for rejection?
 
coloradobluesky said:
Only work on or replace one magneto at a time. This is in case someone makes a mistake, like putting way too much grease or not connecting a wire correctly and if he made the mistake on both mags, well, you get the picture....Its not just a good idea, it's science!
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Does Science specify what's a good time frame to wait, one flight, a week, month, year, years?
 
Get them off by 1/2 of the expected life. Like one is 0 hours and the other is 1000 hours old on an expected life of 2000 hours. That would be ideal, not always doable. Get them different, that is the point. That way they are less likely to do the same thing, fail, at the same time

Thats what the probabilities say, assuming some things are even.
 
coloradobluesky said:
Get them off by 1/2 of the expected life. Like one is 0 hours and the other is 1000 hours old on an expected life of 2000 hours. That would be ideal, not always doable. Get them different, that is the point. That way they are less likely to do the same thing, fail, at the same time

Thats what the probabilities say, assuming some things are even.
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So, based on probability, an aircraft is least safe when it's new, and everything has the same time?
 
You ask a lotta questions.

Some things you don't know. But if you have a situation where two identical things have to fail for the system to fail, you want them out of synch. You can't do that when they are brand new though.
 
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Everything has flaws. With magnetos you dont want them flawed at the same time.

Think of it this way, the pilot might still owe you money.
 
coloradobluesky said:
Everything has flaws. With magnetos you dont want them flawed at the same time.
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There is no data to support that personal opinion.

Many times I've changed both mags, or had both rebuilt, and never had a failure related to infant mortality.
Magnetos have a very rigorous testing procedures off the test bench.
When they are installed correctly, and run on the engine prior to flight giving proper mag drops, there is very little chance they will fail.
 
GlennAB1 said:
So, based on probability, an aircraft is least safe when it's new, and everything has the same time?
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There is no data to support this either. Infant mortality is a remote possibility, that we prevent by testing in the manufacturing process, testing when installing.
 
GlennAB1 said:
So, based on probability, an aircraft is least safe when it's new, and everything has the same time?
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Most parts replacement failure graphs do look like a U shaped curve.

GlennAB1 said:
Very little chance of a single failure, let alone double failure.
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What about a double rainbow?! :)

Tom-D said:
There is no data to support this either. Infant mortality is a remote possibility, that we prevent by testing in the manufacturing process, testing when installing.
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Testing lowers that left side slope of the U on most things but doesn't remove it completely. In the case of this particular part, since it's easy to disassemble and look to see if it was built wrong, the left side of the U often happens in the shop instead of in the air, but it still happens.

I know you've seen bad parts straight out of the "new" box. That's still infant mortality, you just caught it sooner than later.
 
Question....what is the P lead nut (connects the P lead to the magneto) called? Is it:

A: shielded nut
B: unshielded collar
C: none of the above and your beat to crap (insert correct term here) is all you're gonna get.

Side note: my Bendix mags were made in the 80s and my mechanic's current testing gear is too "deep" to insert properly into the magneto.
 
Timbeck2 said:
Question....what is the P lead nut (connects the P lead to the magneto) called? Is it:

A: shielded nut
B: unshielded collar
C: none of the above and your beat to crap (insert correct term here) is all you're gonna get.

Side note: my Bendix mags were made in the 80s and my mechanic's current testing gear is too "deep" to insert properly into the magneto.
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None of the above! And I don't understand about your mechanic's gear being too deep??
 
denverpilot said:
Testing lowers that left side slope of the U on most things but doesn't remove it completely. In the case of this particular part, since it's easy to disassemble and look to see if it was built wrong,
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Are you saying Mags are easy to disassemble? That may be true, but putting them back together again requires special tools & pubs.
 
Timbeck2 said:
All his testing leads bottom out before you can tighten them up on the P lead...socket.
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I would guess you should have a better understanding of the problem, before we continue this discussion.

Older Bendix Mags require a tool to open the "P" lead circuit when the harness is removed. so that you can spark the mag. these are pretty common for any one that is working with Bendix mags. So if your Mechanic doesn't have the proper tools and equipment, what should you do?
 
Hey Tom....I'm not really interested in what testing tools my mechanic has, I'm interested in what the nut that connects the P lead to the mag is called and where I can find a couple of new ones. Mine are chewed up from years of plier tightening.
 
Timbeck2 said:
Hey Tom....I'm not really interested in what testing tools my mechanic has, I'm interested in what the nut that connects the P lead to the mag is called and where I can find a couple of new ones. Mine are chewed up from years of plier tightening.
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There are several different types, the Illustrated parts breakdown for you mag make and model should show a part number then a google search. If you have old style Bendix the "P" lead harness comes as an assembly. That's the only way I buy those old bell type nuts.
 
Tom-D said:
There are several different types, the Illustrated parts breakdown for you mag make and model should show a part number then a google search. If you have old style Bendix the "P" lead harness comes as an assembly. That's the only way I buy those old bell type nuts.
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I wonder if a nut off an old spark plug lead would thread onto that magneto p-lead boss.
 
Tom-D said:
Are you certain he has a Bendix harness? there are several after market kits in service.
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You mean spark plug harness? What does that have to with a p-lead terminal on the p-lead wire?
 
bnt83 said:
You mean spark plug harness? What does that have to with a p-lead terminal on the p-lead wire?
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there are after market "P" lead harnesses too.
 
Holy crap...$82 for a nut. Well now, gotta rethink this vanity issue...nope. It looks fine with the cowling on.
 
Tom-D said:
there are after market "P" lead harnesses too.
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Bogart? Judging from the condition of the rest of the airplane in the last few threads, the p-lead wires are factory piper...
 
What will interchange depends upon what plate is on the back of the mag.
 
Timbeck2 said:
Factory Bendix...on a Piper. Mags are 80s vintage.
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when the A&P sent the mags away, did they keep the point plate ? or did they send it with the mag? The point plate is the 1.25" X 2.5" plate that was held on the back of the mag by two small screws and allows the "P" lead to connect with the mag.
 
Tom-D said:
when the A&P sent the mags away, did they keep the point plate ? or did they send it with the mag? The point plate is the 1.25" X 2.5" plate that was held on the back of the mag by two small screws and allows the "P" lead to connect with the mag.
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Pretty sure TCM calls that the "breaker cover".
 
But to answer your question Tom, my mechanic has a set of these:

12-03525.jpg


with a cute little box that makes noise used for testing magnetos in various ways. The pointy end bottoms out before one can tighten up the silver part.

I'm only one step up from doo hickies and thingamajigs on this subject.
 
Timbeck2 said:
Holy crap...$82 for a nut. Well now, gotta rethink this vanity issue...nope. It looks fine with the cowling on.
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too bad,,, I just gave away a whole box of Bendix junk, there was probably 5 or 6 of them in it.
 
Timbeck2 said:
But to answer your question Tom, my mechanic has a set of these:

12-03525.jpg


with a cute little box that makes noise used for testing magnetos in various ways. The pointy end bottoms out before one can tighten up the silver part.

I'm only one step up from doo hickies and thingamajigs on this subject.
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yes they should work on all but a couple very old Bendix mags. the little tweeter box is for timing the mag to your engine, points open when the lights go out and the tweeting starts.
these are known as "P" lead connections that will unground the "P" circuit and allow the A&P to attach their timing tools.
 
Timbeck2 said:
But to answer your question Tom, my mechanic has a set of these:

12-03525.jpg


with a cute little box that makes noise used for testing magnetos in various ways. The pointy end bottoms out before one can tighten up the silver part.

I'm only one step up from doo hickies and thingamajigs on this subject.
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yes they should work on all but a couple very old Bendix mags. the little tweeter box is for timing the mag to your engine, points open when the lights go out and the tweeting starts.
Timbeck2 said:
Well then, I have a couple of very old Bendix mags.
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They should work on your S-20's, I was talking very old like in Radial mags for very old radial engines.
 
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