Magnetos

[plongson]

How often are you guys actually servicing magnetos? I'm talking about early stuff...ours is 1962 Cherokee. The logs are a bit sketchy (IMHO) for the last 20 years and I'm not sure if they have (if ever) had any service. We recently had a mag drop go from acceptable to not, in a few short weeks.
it's going in the shop tomorrow to have it looked at, and they think it might be simply timing. My research shows points and condenser a coil and magnet are also inside these units.
Back in the day, it was SOP to change points/condenser and plugs VERY often to keep the old school cars running well.
What's the opinion here??

 

[Huckster79]

I plan on 500 hrs. Coming up this next annual I beleive.

I know of a bird that had a mag issue in flight they hadn’t been cracked since overhaul, 1200 hrs before. That hairy moment was easily preventable.

I bought a 150 to have for a short while, and beat the seller up over no mag inspection in 1500 hrs- sure enough they were toast… not overhaul-able and had to get new reconditioned ones. Luckily I had planned on that going in and had taken note of it in price negotiations.

My IA says, “keeping up on them is far cheaper than bent metal or even just running em for broke and needing new instead of a little love along the way”

And folks- Don’t view your bird as a magic flying carpet and an IA makes it factory new at every annual as many seem too. Track these on your own. I make a list of maintenance items I’m aware of before annual. It’s my hide on the line. I’m not talking down IAs, however “trust but verify” is a good policy for important maintenance items.

 

[Bell206]

What's the opinion here??

Following the OEM recommendations in some circumstances keeps you money ahead especially on mags, alternators, and other similar accessories. There have been a few posts here that go into more detail on the reasons.

 

[Let'sgoflying!]

Back in the day, it was SOP to change points/condenser and plugs VERY often to keep the old school cars running well.
What's the opinion here??

hey plongson,
If
-it’s been 20 years or
-no one can tell what was done and when
I would plan on having a full iran or rebuild (or replacement). They could be toast inside.
I plan on a 500 hr inspection with new points and any other parts… plus any AD work (which might fall at 500hrs or might be earlier). i can usually get 500hrs out of points. The condenser, my mag shop only changes them if they fail testing, they have gotten pricey and often don’t need changing.
Plugs; on condition. Inspect & test at least every 100hrs, I usually do it at 50hrs. They can usually last 500hrs.

 

[GeorgeC]

The logs are a bit sketchy (IMHO) for the last 20 years and I'm not sure if they have (if ever) had any service.

This works for things other than magnetos as well. If you don't see brake master cylinders / spark plugs / contactors / etc in the last 20 years of logs, it's probably time.

 

[Dan Thomas]

Bendix specifies a 400-hour inspection interval. Slick specifies 500. But most mags get nothing until one fails, and sometimes it fails at some inconvenient place, costing you much time and money and frustration. Same thing goes for vacuum pumps and alternators. All these things are addressed in OEM service manuals.

We had the mags off a 1700-hour, 40-year-old engine. There was no record they'd ever been opened up. They were beyond economical repair and had to be replaced. Everything in them was toast. These things have sealed ball-bearings in them that age and corrode as the seals shrink and crack and the grease dries out, and if an inboard bearing fails it sends balls and bits of cage into the engine accessory drive gearing. The mag gear starts damaging the gears, too, and it it breaks off, the whole engine goes. The OEMs are not fooling around when they make inspection interval recommendations.

I usually got 1000 hours out of points, as long as the condenser was OK. By 1000 hours (second 500 inspection) they were getting eroded to the point that I no longer trusted them, and they got replaced. Even at the 500 there is some erosion and roughness, and if you aren't careful and accidentally shift the moving point's arm a bit (Slick), the points' roughnesses don't mesh properly and the gap increases quickly as the new position arcs off the old roughness. That advances the timing and throws the e-gap off. More trouble.

 

[Magman]

IIRC both current mfg recommend a 4 year tbo in addition to the hourly interval.
Rust is the enemy and encountered more in non flying engines. The weak point here seems to be the Impulse Spring as rust is fatal for all springs.

 

[RyanB]

The logs are a bit sketchy (IMHO) for the last 20 years and I'm not sure if they have (if ever) had any service.

Dude, you need to get them done NOW! You’re on borrowed time…

 

[Huckster79]

Dude, you need to get them done NOW! You’re on borrowed time…

possibly past borrowed time and just don’t know it yet…

 

[Dan Thomas]

possibly past borrowed time and just don’t know it yet…

Oh, it will let him know in an unmistakable manner before too much longer.

I could never understand why mechanics aren't educating their clients about this stuff. We do owners no favors by letting them think that the basic FAR 43 Appendix D annual covers everything (CAR 625 Appendix B in Canada). It doesn't, not by a mile, and we frequently see posts of owners experiencing failures of mags, alternators and vacuum pumps, as most common examples. That doesn't need to happen, and I consider insane to run this stuff to failure.

 

[Bell206]

I could never understand why mechanics aren't educating their clients about this stuff.

In general, I found the education takes place initially but after a time of falling on deaf ears it stops unless an owner brings it up. That same education continuely takes place on PoA, yet every month the same issues pop up and not only by new posters. So long as the owner is the gate keeper to the aircraft there's not much we can do except not sign off things. And we know how well that works.

 

[Huckster79]

Oh, it will let him know in an unmistakable manner before too much longer.

I could never understand why mechanics aren't educating their clients about this stuff. We do owners no favors by letting them think that the basic FAR 43 Appendix D annual covers everything (CAR 625 Appendix B in Canada). It doesn't, not by a mile, and we frequently see posts of owners experiencing failures of mags, alternators and vacuum pumps, as most common examples. That doesn't need to happen, and I consider insane to run this stuff to failure.

right! I want it IRANed or replaced while it still has life left in it… whatever “it” is if it’s vital to safe operation.

Ive worked hard to become a knowledgeable owner and also know I have volumes yet to learn. but I’m shocked at the level of lack of basic mechanical knowledge of our birds… And no attack on the OP by that statement-at all. I have lots I don’t know and have asked every question in the book- more of a broad brush statement.

I once knew a fancy bird driver who was arrogant as could be. He said to me once “I’m worried I did serous mechanical damage to the plane… I flew it the other day accidentally on just one mag- for an hour!!!! I’m not sure what this is going to cost me”. Anyone else I would have explained- “nothing really” but him I said “man idk, better get it checked out” figured some mechanic could use the few bucks labor more than he could- maybe change out the flux capacitor and flush the aileron fluid to be safe

you can own a modern car w no understanding of anything, but even just a few decades ago one needed some basic understanding of the mechanics to operate it well and those cars and our birds share a lot in common.

it would be really great if there were some solid resources such as even a course to take on such things. Not making one an a&p but some understanding that may not just be natural for all. I’ve often said learning to be a good owner was as much work as learning to fly the thing in the first place!

 

[Skymac]

Lycoming O320’s, I pull the slicks at 700 hours and just exchange for new ones.

 

[Bell206]

it would be really great if there were some solid resources such as even a course to take on such things.

FYI: There are a number of resources out there for an owner to learn from with a majority of them free and easily available. No formal course needed. I've posted them in past threads and PM'd links as well so if you'd like them just let me know.

 

[Dan Thomas]

Lycoming O320’s, I pull the slicks at 700 hours and just exchange for new ones.

That just drives the hourly costs way up. Besides, there have been way too many SBs on new Slick mags, and I'd bet on the work done by a good mag shop before I'd assume that new Slicks are good.

 

[Skymac]

I’m not sure it really does increase costs the way you think. I run a school and it’s $8xx a mag from spruce, getting them rebuilt isn’t much cheaper from what I’ve found and I’ve had two only last 300 hours after a 500 service. Downtime costs way more than a few extra bucks up front.

 

[MSUDavid]

Bought my plane with 700 hrs on slicks. I quickly had some issues and IRANing them fixed the issue. I wouldn’t wait longer than 500 hrs in the future.

 

[Dan Thomas]

I’m not sure it really does increase costs the way you think. I run a school and it’s $8xx a mag from spruce, getting them rebuilt isn’t much cheaper from what I’ve found and I’ve had two only last 300 hours after a 500 service. Downtime costs way more than a few extra bucks up front.

I was the maintenance manager for a school, and we did our own mag inspections. Get the Slick manual, a couple of small tools, and they're not a big deal at all. Sure didn't cost us $700 per mag.

And I never, ever had a failure on any of the mags I did. Ever. It's not rocket science, but there are ways to screw them up, including putting too much grease on the cam, which then gets into the points and they burn up. The manual is good education.

 

[Bathman]

One surefly and one slick. Overhaul the latter at 500 hours.

 

[Magman]

While it is apparent the mags are overdue servicing my belief is addressing a
Mag Drop by pulling the mags is not the way to go. Many “Drops” are not caused by
Mags but by other components. Once the mags are removed it’s too late to determine other factors.

A time honored method of diagnosing is the “ Cold Cylinder Check”. Quite easy to do on a Cherokee. If the engine is “ rough” during the check that is due to it is running on 3 cylinders. Which one?

Start engine and IMMEDIATELY switch to the bad mag. Run about 30 seconds.
Shut down.
Test which exhaust pipe is cold. Spray water, laser thermometer or a wet finger will tell.

If you can’t determine which jug is not firing then it is likely timing.

 

[Huckster79]

FYI: There are a number of resources out there for an owner to learn from with a majority of them free and easily available. No formal course needed. I've posted them in past threads and PM'd links as well so if you'd like them just let me know.

yes! Absolutely!

POA has been a big part of the ad hoc course I’ve made for myself, but man if there’s more And some consolidated sources I’d eat em up like pumpkin pie in the fall!

 

[Skymac]

The kit is $400 per mag, and you still have to do the labor. For some folks it’s not a big deal but I don’t get extra value out of it. Both times it seemed to be the coil acting up, so that’s more $$. Mileage varies, I’ve taken them to 1000 with no issue, I just personally go at 700. Arrest me for it

 

[Snowmass]

All my planes have had the very early Slick mags and they have been great, I have done all the mechanical work on them since the sixties. They are easy to work on but getting parts can be iffy. I have had to make a few tools to pull couplings etc,I only change points if they look a bit pitted and the condenser if the old one had failed which only happened once in about 6000 hours. I always carry a spare set of points and condenser in my C-210.
,

 

[Dan Thomas]

The kit is $400 per mag, and you still have to do the labor. For some folks it’s not a big deal but I don’t get extra value out of it. Both times it seemed to be the coil acting up, so that’s more $$. Mileage varies, I’ve taken them to 1000 with no issue, I just personally go at 700. Arrest me for it

What's in that kit for $400?

 

[RyanB]

I run a school and it’s $8xx a mag from spruce, getting them rebuilt isn’t much cheaper from what I’ve found

Sounds about right. It was ~$600/mag for the 500hr inspection from QAA about a year ago and $250 credit for a viable core.

 

[Dan Thomas]

Slick's 500-hour inspection is not an overhaul. Paying for an overhaul at 500 hours is wasting money.

From Slick's L-1363D magneto manual:



Yeah, you'd be better off buying a new mag instead of all those parts. But the 500-hour inspection does not require all that. Overhauls are typically done at engine replacement or overhaul, 2000 hours or whatever, and most times new mags are installed.

 

[Skymac]

 

[Dan Thomas]

Unless they've recently rewritten the manual, that stuff is NOT required for the 500-hour inspection. Half the time not even the points need replacing, and if the condenser tests at around 0.34µf, and if its resistance is infinite, it's fine.

I had all the other stuff run all the way to TBO on numerous engines in numerous airplanes. I once had the plastic gears making dust because the tech at the factory hadn't pushed the rotor gear down all the way and its flange was being ground off by the distributor gear. And once I had to replace the distributor block due to another factory error (the misaligned coil tab SB) that wore the carbon brush and spread carbon dust into the distributor and had flashover occurring. Burnt the distributor block.

 

[Skymac]

Unless they've recently rewritten the manual, that stuff is NOT required for the 500-hour inspection. Half the time not even the points need replacing, and if the condenser tests at around 0.34µf, and if its resistance is infinite, it's fine.

I had all the other stuff run all the way to TBO on numerous engines in numerous airplanes. I once had the plastic gears making dust because the tech at the factory hadn't pushed the rotor gear down all the way and its flange was being ground off by the distributor gear. And once I had to replace the distributor block due to another factory error (the misaligned coil tab SB) that wore the carbon brush and spread carbon dust into the distributor and had flashover occurring. Burnt the distributor block.

Good information to know!

 

[Magman]

It may well be that the issues Dan encountered prompted Champion/Slick to change how things are done. Shortly before he was pushed out; the great Tech Rep Joe Logie told me that they video the assembly process. I’m unsure of the extent.

My belief is the most important item of the “500” is assuring E-gap is correct.

Generally Impulse Spring, Carbon Brush and Rotor Gear are replaced. Others on condition.

 

[Dan Thomas]

My belief is the most important item of the “500” is assuring E-gap is correct.

Generally Impulse Spring, Carbon Brush and Rotor Gear are replaced. Others on condition.

Yes, E-gap is critical. But I never replaced an impulse spring, or any gears except for the ones I noted as trashing each other. I even had carbon brushes run all the way to TBO except for the ones affected by the misaligned coil tab SB.

These were in flight school airplanes, busy machines that flew as much as 800 hours a year. The average owner doesn't fly nearly that much, some only 20 or 30 hours a year, and some almost nothing, and the worst guys are those that go out and run the engine for a few minutes without flying it, thinking they're doing it some good, but the blowby on that cold engine is filling the case with water. Now rust starts digging into everything with iron in it. The impulse spring can suffer, and it is really prone to breaking if there's any pitting at all.

 

[Magman]

Dan; well said.

I don’t recall IC Spring failures with high usage aircraft as they seem to seldom wear out. The Queens are another story. Flying the aircraft boils the water out and activates the anti-corrosion ( Oil) system.

Many folks equate the Impulse Coupling with starting only. Few folks seem to realize that a failure will usually result in a dead mag, Or worse.

 

[RyanB]

Slick's 500-hour inspection is not an overhaul. Paying for an overhaul at 500 hours is wasting money.

In my case, they were completely overhauled, as they were beyond serviceable limits.

 

[Dan Thomas]

Can you imagine Ford or GM having a recall record like this on their ignition systems? And this is aside from ADs on Slick mags. These are just SBs. Some should have been ADs.

Year Title Description Category
2020 SB2-19A: Mandatory inspection of impulse coupled Slick by Champion magnetos. Service Bulletin - SB2-19A: Mandatory inspection of impulse coupled Slick by Champion magnetos.
2019 SB1-19: Mandatory inspection of impulse coupled Slick magnetos Service Bulletin - SB1-19: Mandatory inspection of impulse coupled Slick magnetos
2015 S.L.4300/6300-74-20-001 Service Letter - Slick Magneto Supplemental Timing Inspection Information Magnetos
2015 SB1-15A: Potential decreased service life of Slick 4-cylinder magneto distributor gear Service Bulletin - SB1-15A: Potential decreased service life of Slick 4-cylinder magneto distributor gear
2012 SB1-12: Single Point Magneto points replacement Service Bulletin - SB1-12: Single Point Magneto points replacement Magnetos
2010 SL1-10: Slick 400, 600, 4200, and 6200 Series Magneto Replacement Service Letter - SL1-10: Slick 400, 600, 4200, and 6200 Series Magneto Replacement
2008 SB2-08B: Mandatory inspections on all Slick 4300/6300 and LASAR™ 4700/6700 magnetos (Corrected Copy) Service Bulletin - SB2-08B: Mandatory inspections on all Slick 4300/6300 and LASAR™ 4700/6700 magnetos (Corrected Copy)
2008 SB3-08B: Mandatory inspections on all Slick 4200/4300/6200/6300 and LASAR™ 4700/6700 magnetos Service Bulletin - SB3-08B: Mandatory inspections on all Slick 4200/4300/6200/6300 and LASAR™ 4700/6700 magnetos
2008 SB2-08-B: Mandatory inspections on all Slick 4300/6300 and LASAR™ 4700/6700 magnetos (Corrected Copy) Service Bulletin - SB2-08-B: Mandatory inspections on all Slick 4300/6300 and LASAR™ 4700/6700 magnetos (Corrected Copy)
2008 SB3-08-B: Mandatory inspections on all Slick 4200/4300/6200/6300 and LASAR™ 4700/6700 magnetos Service Bulletin - SB3-08-B: Mandatory inspections on all Slick 4200/4300/6200/6300 and LASAR™ 4700/6700 magnetos
2007 SB2-07: Clarification of Torque Requirements for Securing Magneto Driver PN K5265 Service Bulletin - SB2-07: Clarification of Torque Requirements for Securing Magneto Driver PN K5265
2007 SB1-07: Clarification of Torque Requirements for Securing Magneto to Driver PN K5265 Service Bulletin - SB1-07: Clarification of Torque Requirements for Securing Magneto to Driver PN K5265
2007 SB3-07: Replacement of Impulse Coupling Assembly in Certain Slick Magnetos Service Bulletin - SB3-07: Replacement of Impulse Coupling Assembly in Certain Slick Magnetos
2000 SB1-00C: Impulse Coupling Stop Pin, 6314, 6324, and 6327 Magnetos Service Bulletin - SB1-00C: Impulse Coupling Stop Pin, 6314, 6324, and 6327 Magnetos
1995 SB1-95: 4000/4100 Series Magnetos Service Bulletin - SB1-95: 4000/4100 Series Magnetos Magnetos

 

[Magman]

Wow! One unfortunate thing about this is the mags ARE being sold and installed with outstanding SBs !

 

[Dan Thomas]

Many folks equate the Impulse Coupling with starting only. Few folks seem to realize that a failure will usually result in a dead mag, Or worse.

Yup. That impulse spring keeps the mag at the desired spark advance point. It only does its impulse thing during start, by retarding the spark to near TDC and snapping the mag rotor rapidly at that point to generate a hot spark. The rest of the time it has to hold the rotor in the advanced position, and if it breaks, the timing goes to TDC and power goes to nothing.

Worn plastic gears in the magneto can slip and let the distributor start sending sparks to the wrong cylinders at the wrong times, and all sorts of belching and barfing and smoking and RPM loss occurs as the spark in a cylinder on its intake stroke ignites the incoming charge and sends that flame into the induction system. Ugly. Could kill the engine entirely.

Mag inspections are important, but it seems that most owners don't figure that out until one of theirs quits or misbehaves at a bad time in an inconvenient or dangerous place. Sometimes they don't figure it out until the carburetor and fuel pump and maybe injectors and servos all get replaced in an attempt to fix a misbehaving engine, with no success until they finally do the mags. I see the fuel system suggested as the culprit nearly every time here on POA and other forums, yet the ignition is responsible most of the time. Why is that? Because people don't understand electricity and what a mag does and they think any old spark is good enough. It ain't so.

 

[plongson]

I'm the OP...We got the plane in and had the mags checked. BOTH were out of time (one more than the other) and had to be pulled and reinserted because the slots were out of travel (this what they told me). They are old mags...it's an old plane...the owner of the shop said they have packing (Garlock) and not a seal on the input shaft. He also said we're good for now but start thinking about replacement.
There is now essentially no mag drop and nice max RPM and pulls and climbs hard. Timing appears to be the source of the RPM drop.

I've been a master mechanic my adult life with certs and certificates up the wazoo including ISO CAT. 3 Level-3 Vibration Analyst...I have always done my own work and it KILLS me to have someone wrenching on my ****. I know I haft'a play the game and stay inside the lines...for now I'm at the mercy of A&P's and flight shops...GRRRRR

THANKS for the input all!!

 

[Lndwarrior]

"Essentially no mag drop"

If you think this is a good thing you may want to do a little research. Seriously. Do some research.

 

[plongson]

If it makes you feel any better, it's within the POH and about 100 to 120 RPM drop on each mag. Going from the problem RPM drop of 500, 100 seemed like "essentially no mag drop". I was making conversation and following up on my original post for the benefit of the forum.

We all understand conversations via the internet fail to convey emotion, but your reply seems "snarky". Thanks for the feedback

 

[Dan Thomas]

I'm the OP...We got the plane in and had the mags checked. BOTH were out of time (one more than the other) and had to be pulled and reinserted because the slots were out of travel (this what they told me).

Now. That indicates that the mag internal timing has shifted due to points cam wear or points erosion. Simply reclocking the mag is treating symptoms, not the cause. The spark will be weakened and sooner or later it will fail you.