Slick Mags, a tutorial

Tom-D

Tom-D

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Feb 23, 2005
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Tom-D
I pulled a couple Slicks off a C-172 /0-320-E2D today and broke one apart, and took a few pictures of what is inside.

1 impulse coupling left mag only (4371)
2 worn cam follower (see the wear)
3 brass debris in the distributor housing
4 top/back half of a 43XX series mag
5 electrolysis etching of the distributor contacts
6 timing marks for timing of the rotor to distributor gear
7 slick pin special tool to set mag to # 1 firing position
8 distributor assembly
9 distributor assembly set at #1 firing position with pin installed
10 front half of a 42XX series mag shows the coil, and points
11 more electrolysis of distributor contacts ( mag has 2400 hours)

it had a 500 RPM mag drop, it's time for new.
 

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1 slick 4371 = $780, 1 slick 4370 = $709, wire harness = $350, 8 Iredium plugs $800, should fix it, plus labor, 6 hours at 50 per, That includes making up a new set of "P" leads and cleaning the Ignition switch.

ever pull a new set of "P" leads thru the fire wall? it's a real PITA.
 
Fourth picture, Tom: the magneto shaft gear has been rubbing on the condenser wire. Seen that before. Slick hasn't been too careful.

Dan
 
Dan Thomas said:
Fourth picture, Tom: the magneto shaft gear has been rubbing on the condenser wire. Seen that before. Slick hasn't been too careful.

Dan
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It ran fine for 2400 hours.
 
Tom-D said:
ever pull a new set of "P" leads thru the fire wall? it's a real PITA.
Click to expand...

Yes. "PITA" is a kind characterization. Owner-assisted stuff. The A&P was smart enough to have me do it. It was the one part of an extensive firewall-forward everything overhaul job that I didn't like so much.
 
The local mechanics around here hate Slick's with a passion... Dunno why...
 
Tom-D said:
no, no parts were replaced that I know of it looked stock to me, and the white seal on the screw head was intact.
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Holey mackerel; that might be some kind of record. Wouldnt we all love to get 2400 hrs out of mags?
 
Let'sgoflying! said:
Holey mackerel; that might be some kind of record. Wouldnt we all love to get 2400 hrs out of mags?
Click to expand...

I got just a tick over 1500 and 27 years out of the set Cessna installed on my plane. Replaced them due to the timming starting to drift.
 
Dr. O said:
The local mechanics around here hate Slick's with a passion... Dunno why...
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For starters, the parts ot repair a slick are more than a new mag.
 
$800 for plugs? just curious, are there any less expensive options
 
Let'sgoflying! said:
These were untouched for 2400hrs. I just can't imagine ignoring them for that long.
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Wow. 500 hours is the recommended service interval for mags. Just saw this video yesterday about mags and mag servicing.

http://www.eaavideo.org/video.aspx?v=107205803001

Tom, on picture #4, between the gear and the condensor is a wedge of metal with little tiny teeth facing the condensor. What's up with the teeth? Doesn't appear from this view to be anything it engages with. Can't imagine it's for weight savings; that's a minuscule amount of metal.

Maybe it's just to create clearance from the condensor; but then I'd expect it to be cut flush, not with jagged teeth. :dunno:

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TangoWhiskey said:
Tom, on picture #4, between the gear and the condensor is a wedge of metal with little tiny teeth facing the condensor. What's up with the teeth? Doesn't appear from this view to be anything it engages with. Can't imagine it's for weight savings; that's a minuscule amount of metal.

Maybe it's just to create clearance from the condensor; but then I'd expect it to be cut flush, not with jagged teeth. :dunno:
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It's just a rough casting. no real purpose.

edit.

It looks like the machine that produced the threads for the cap/condenser went into the housing too far, and milled some threads on the housing internal partition.
 
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TangoWhiskey said:
Wow. 500 hours is the recommended service interval for mags. Just saw this video yesterday about mags and mag servicing.

http://www.eaavideo.org/video.aspx?v=107205803001
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I watched that video about half way thru and saw so many mistakes in terminology, and theory that my mind was about to blow.

In my years as a A&P I have discovered that 90% of mag problems are induced by the mechanic.

My PMI at FSDO once told me that if he want any A&P's ticket he would ask the A&P if he worked on mags, if they say yes he'd ask to see the manual, if they could not show him an up to date manual he'd bust them on 43.13a

You don't simply break these open with out the tools and pubs and it requires a whole set of tools just for a bendix mag, this guy didn't show a single one of either.
 
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Tom-D said:
I watched that video about half way thru and saw so many mistakes in terminology, and theory that my mind was about to blow.
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Examples, since this is an educational thread?

Tom-D said:
In my years as a A&P I have discovered that 90% of mag problems are induced by the mechanic.

My PMI at FSDO once told me that if he want any A&P's ticket he would ask the A&P if he worked on mags, if they say yes he'd ask to see the manual, if they could not show him an up to date manual he'd bust them on 43.13a
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:thumbsup: As he should.
 
Tom-D said:
In my years as a A&P I have discovered that 90% of mag problems are induced by the mechanic.
Click to expand...


Well almost every A&P I've talked to is scared to death of mags because they didn't get good instruction on them in school. If some one actually takes the time to REALLY teach them to you they are very simple things:wink2:
 
TangoWhiskey said:
Examples, since this is an educational thread?
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He didn't use the term "E" gap corectly or explane what it is. He did not use the term " magnetic induction" properly.

And more
 
Skylane81E said:
Yes and no, depends on what you are really doing. There is some stuff I COULD do with out the manuals, IE setting the E-gap.

that said I do ALWAYS use up to date manuals
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with out an up to date manual, can you tell if the ICA's on the product hasn't changed?

That goes for any appliance, not just mags.
 
Skylane81E said:
Well almost every A&P I've talked to is scared to death of mags because they didn't get good instruction on them in school. If some one actually takes the time to REALLY teach them to you they are very simple things:wink2:
Click to expand...

Yes they are very simple devices, but they do require special tools to work on them properly, plus the fact that the internal parts such as the distributor block is more expensive to replace than buy a new mag, is the biggest reason no one works on them,

The SL-2XXX series TCM mag is very common, and much better mag than slicks, yet because of the impulse coupling AD the owners want to get away from, so they have swapped out to slicks.
 
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Skylane81E said:
Well almost every A&P I've talked to is scared to death of mags because they didn't get good instruction on them in school. If some one actually takes the time to REALLY teach them to you they are very simple things:wink2:
Click to expand...

I've seen a lot of good mags sent in as cores to swap over to the Slicks using a kit that contains the dual harness when all that was needed was a single harness lead for 25 bucks.
 
Tom-D said:
Yes they are very simple devices, but they do require special tools to work on them properly, plus the fact that the internal parts such as the distributor block is more expensive to replace than buy a new mag, is the biggest reason no one works on them,

The SL-2XXX series TCM mag is very common, and much better mag than slicks, yet because of the impulse coupling AD the owners want to get away from, so they have swapped out to slicks.
Click to expand...

Yeppers, I put a nice new pair of Bendix on my bird when I pulled the slicks off.
 
Tom-D said:
I've seen a lot of good mags sent in as cores to swap over to the Slicks using a kit that contains the dual harness when all that was needed was a single harness lead for 25 bucks.
Click to expand...

FACEPALM,

not supprised though
 
Let'sgoflying! said:
Holey mackerel; that might be some kind of record. Wouldnt we all love to get 2400 hrs out of mags?
Click to expand...

Got 1,996 out of mine... a few parts replaced at 1200 hrs. Was going to replace at this annual them due to time in service, excessive drop, and difficulty hot starting. Ended up having to O/H the engine anyway.
 
If it ain't broke...
I'm big on on condition repair/overhaul/replacement (circle one)
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Maybe some think it's overkill but I have had pretty good luck using preventive maintenance. I have a chart with hours/dates that I inspect or replace or overhaul. Maybe it just makes me feel better.....but thinking about it - I have found quite a few things that might have made me aog a long way from home.
Maybe if Tom's guy had used such an aid, (or his other mechanics had not ignored that component for so long) he wouldn't have had to limp in for repairs.
 
Let'sgoflying! said:
Maybe some think it's overkill but I have had pretty good luck using preventive maintenance. I have a chart with hours/dates that I inspect or replace or overhaul. Maybe it just makes me feel better.....but thinking about it - I have found quite a few things that might have made me aog a long way from home.
Maybe if Tom's guy had used such an aid, (or his other mechanics had not ignored that component for so long) he wouldn't have had to limp in for repairs.
Click to expand...

I won't argue, but I don't take things off just because it's "time" like i said earlier i pulled mine off at the first hint that something was amiss. You listen and the machine talks to you.
 
I won't argue
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Nor will I (argue). And I won't try to impose 'my way' on anyone else!


You listen and the machine talks to you.
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Yes, but I prefer it doesn't talk to me when I am in....Mexico, or Podunk, Arizona on a Sunday!

My goal is to stay ahead of things. Maybe I will change out....plugs, alternator belt, mag parts, vac pump, engine compartment hoses etc etc a little before their useful life.....but I hope in doing so I can spend time doing these things in the leisure of my hangar and not on a strange ramp!
(btw I have been present when someone else's airplane was aog, away from home, for each of the things above.)
 
Let'sgoflying! said:
Maybe some think it's overkill but I have had pretty good luck using preventive maintenance. I have a chart with hours/dates that I inspect or replace or overhaul. Maybe it just makes me feel better.....but thinking about it - I have found quite a few things that might have made me aog a long way from home.
Maybe if Tom's guy had used such an aid, (or his other mechanics had not ignored that component for so long) he wouldn't have had to limp in for repairs.
Click to expand...

I believe you are associating two different owners, the mag shown in these pictures came off after a discrepancy, last week. The guy who opened his mouth in front of the FAA was a couple years ago.

At todays prices of internal parts it is not prudent to overhaul at 500 hours as many owners do, it is a simple waste of money, the mags won't give you trouble for a much longer time frame than that.

If you are running a TCM mag of the SL-2XXX series either the 21, 2100, or the 20, 200, or the 2100 the impulse coupling needs the AD complied with at 500 hours, If you have it off anyway, why not break it open and inspect and repair as required.

Parts of a TCM mag are reasonable in price and the mag can be rebuilt cheaper than the slick
TCM price list
http://www.chiefaircraft.com/aircraft/ignition-system-mags-plugs/tcm-bendix-magneto-parts.html

Slick price list.
http://www.chiefaircraft.com/aircraft/ignition-system-mags-plugs/slick-magneto-parts.html
 
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