Left Magneto Self Destruct

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Want to post anonymously until I get this figured out.

I have an IO-360 in a PA28. Has 1100 hours. Magnetos are due for a recommended inspection in 50 hours.

This weekend I was doing my preflight. Pulled the prop through by hand a couple of rotations just to get some oil spread around. Felt a tightness at one point followed by a pop. Did not require very much pressure to rotate it past this pop. I spun it 2 more times and did not feel the pop. Figured maybe it was my starter or something.

Taxi'd to the pumps, heard a very slight little ticking in the engine, made a mental note to check out the starter and belt up front for anbormalities. Did that, all looked fine. My starter has stuck before, and the plane has a brand new starter, so that was my logoical place to look for trouble.

Restarted after fueling and it ran and sounded perfect. Annonced my interntions to backtaxi down the runway, gave it some throttle and heard a noticable bang followed by the engine sounding slightly different. Almost like the alternator belt was stuck or jumped a pully and making noise as it rubbed.

Taxi'd back to my tied down, shut down, and called the machanic over to "listen" to it and check it out. So we did that, he pulled the prop through, this time the starter was engaged so it was hard for him to "listen" like he wanted to. He told me to start it. tried, and it would not light off Tried, and tried again and it would not fire. Just cranked over.

So he said, I bet it is your impulse coupling. He pulled the left magneto off. Sure enough, that was the site of the trouble. But the impulse coupling was the tip of the iceberg. There were teeth missing off of the drive gear (not the plastic gear inside the magneto, but the big metal gear on the outside). The magneto shaft was bent. And worst of all, there were teeth missing off the drive gear (the gear on the crankshaft was not missing any teeth thankfully).

The machanic continued to pull the magneto apart to find the entire thing in shambles.

(Side note - I was taking off from a grass strip surrounded by forest. If this problem would have happened at the end of my takeoff run I would likely have died. Why you ask? Because once the magneto drive gear starts skipping that magneto would then start firing at the wrong time either making the engine shut off, doing more catostrophic damage, or at the least diminishing any power I would need to climb away from those trees. The mechanic said he had never seen this happen before in his 30 years of working on GA planes, and that this was the kind of stuff that kills people. So I was digesting this info, and not exactly soaking in all the observations he was giving me about the internals of the magneto.)

He showed me the wearable things inside, like brushes and whatever else (again, not thinking straight). It had oil in it, dirt, black dust, a loose main shaft. And it was a super old model that was common well before my engine had been redone in '99. I am going to fedex him my engine log book so they can piece together the history. He said that there is no way this magneto is 50 hours away from the recommended inspection, and that it should have been replaced long ago. Apparently this model magneto was a throw-away version and not a rebuildable version like some newer ones.

So now they need to pull the back of the engine off to try to find these 2 missing teeth. And inspect the backside of the engine to see if any damage was caused to the gear on the main shaft and whatever else is in there. The load on those gears was equal to the load that bent the Magneto shaft.

Have any of you heard of this happening before?

I am going to have a sizable bill coming. And a new found fear of flying. I am getting myself over the fear quickly thanks to a 10 hour drive home in Thanksgiving traffic. But as far as the bill goes, is this something that I could submit to insurance?

If the log book shows anything funny with the magneto inspection or whatever is anybody prior to me accountable? I am going to get my log book later today and am fedexing it up to the mechanic for him to pick through it.

Or is this whole thing just a rare event that I need to suck up with plane ownership?
 
Sorry for the typos, apparently when you do it as unregistered you can't go back in to edit once you proof read it.
 
Yes, I've heard of it. Bad things happen when something fails inside the gearbox. Only thing I can say is this is a good example of why you should comply with the Slick mags service bulletin for inspection every 500 hours. It's also strange if, as you suggest, that the mags weren't done when the engine was overhauled in 1999. When buying a plane, detailed examination of all the paperwork on an overhaul can be a very important of the prepurchase inspection.
 
I had a mag two years ago that was the verge of that - the gears had worn and the impulse coupling and the magnets had come loose inside the housing - and there was incredible wear everywhere - necessitating a complete mag rebuild . .. it was ugly and would have been very ugly if it failed in flight . . . mine were Bendix and finding parts without buying a new mag was quite a challenge because the part that was bad was not in a rebuild kit .. .
 
I'm going to go out on a limb and say that if an A&P found something that would indicate a pending failure in the magneto (or any other critical part of the plane) during the last annual or whenever the magnetos were inspected, it wouldn't have been signed off as airworthy and returned to service. I think you're clean. More importantly, you found the problem on the ground in not in the air and you're in one piece.
 
I'm guessing these were Slick mags, and this is why I won't put a Slick on a plane I am in charge of. Too many cases of Slick mags failing. If it was a Bendix mag, those do fail as well, just not as often.

Large bills are a cost of ownership, and unfortunately they do occur. In the turbine world, there are programs one can be on to try to make your engine costs known in advance where you pay a fixed hourly cost for engine maintenance. I've wondered if such a program in the piston world would work, and I'm guessing probably not. The planes that would benefit the most aren't flown often enough for there to be much money in it.

I'm not sure it would have killed you. Depending on how it ended up failing, it may have had the occasional bad spark. You just don't know.

Good thing you caught it on the ground, though, or you would have found out.
 
Got the logs. The engine has 451 hours Since it was overhauled in '99. The Slick Magnetos were removed, cleaned, and inspected at this time. The magnetos were replaced with new ones in 1983. The engine was originally overhauled in 1984 with 1700 hours on it at that time. When it was overhauled in '99 it just had a little under 500 hours SMOH on it.

So these magnetos have almost 1000 hours on them.
 
Unregistered said:
Got the logs. The engine has 451 hours Since it was overhauled in '99.
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OK -- seems like you said it had 1100 on it in your first post. In any event, 451 hours in 13 years isn't much utiliztion -- I'd be looking carefully at that engine.

The Slick Magnetos were removed, cleaned, and inspected at this time.
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13 years is a long time between inspections of the mags. Here's the SB on that courtesy of Lycoming:
http://www.lycoming.com/support/publications/service-letters/pdfs/SL173C.pdf

In particular, note the varying requirements depending on exactly which series mags you have.
 
Ron, from what I can tell it says these need to be replaced at 800 hours. Is this something an AI would turn up at the annual inspection or is this something I should have known as the airplane owner?
 
Unregistered said:
Ron, from what I can tell it says these need to be replaced at 800 hours. Is this something an AI would turn up at the annual inspection or is this something I should have known as the airplane owner?
Click to expand...

Not Ron, but I believe the answer is both. However, you are ultimately responsible for maintaining the aircraft.
 
I wonder about the total time on the mags, rebuilt at over haul or ?

I agree with Ted, Slicks are a POS mag.
 
Unregistered said:
Want to post anonymously until I get this figured out.

I have an IO-360 in a PA28. Has 1100 hours. Magnetos are due for a recommended inspection in 50 hours.

This weekend I was doing my preflight. Pulled the prop through by hand a couple of rotations just to get some oil spread around. Felt a tightness at one point followed by a pop. Did not require very much pressure to rotate it past this pop. I spun it 2 more times and did not feel the pop. Figured maybe it was my starter or something.

Taxi'd to the pumps, heard a very slight little ticking in the engine, made a mental note to check out the starter and belt up front for anbormalities. Did that, all looked fine. My starter has stuck before, and the plane has a brand new starter, so that was my logoical place to look for trouble.

Restarted after fueling and it ran and sounded perfect. Annonced my interntions to backtaxi down the runway, gave it some throttle and heard a noticable bang followed by the engine sounding slightly different. Almost like the alternator belt was stuck or jumped a pully and making noise as it rubbed.

Taxi'd back to my tied down, shut down, and called the machanic over to "listen" to it and check it out. So we did that, he pulled the prop through, this time the starter was engaged so it was hard for him to "listen" like he wanted to. He told me to start it. tried, and it would not light off Tried, and tried again and it would not fire. Just cranked over.

So he said, I bet it is your impulse coupling. He pulled the left magneto off. Sure enough, that was the site of the trouble. But the impulse coupling was the tip of the iceberg. There were teeth missing off of the drive gear (not the plastic gear inside the magneto, but the big metal gear on the outside). The magneto shaft was bent. And worst of all, there were teeth missing off the drive gear (the gear on the crankshaft was not missing any teeth thankfully).

The machanic continued to pull the magneto apart to find the entire thing in shambles.

(Side note - I was taking off from a grass strip surrounded by forest. If this problem would have happened at the end of my takeoff run I would likely have died. Why you ask? Because once the magneto drive gear starts skipping that magneto would then start firing at the wrong time either making the engine shut off, doing more catostrophic damage, or at the least diminishing any power I would need to climb away from those trees. The mechanic said he had never seen this happen before in his 30 years of working on GA planes, and that this was the kind of stuff that kills people. So I was digesting this info, and not exactly soaking in all the observations he was giving me about the internals of the magneto.)

He showed me the wearable things inside, like brushes and whatever else (again, not thinking straight). It had oil in it, dirt, black dust, a loose main shaft. And it was a super old model that was common well before my engine had been redone in '99. I am going to fedex him my engine log book so they can piece together the history. He said that there is no way this magneto is 50 hours away from the recommended inspection, and that it should have been replaced long ago. Apparently this model magneto was a throw-away version and not a rebuildable version like some newer ones.

So now they need to pull the back of the engine off to try to find these 2 missing teeth. And inspect the backside of the engine to see if any damage was caused to the gear on the main shaft and whatever else is in there. The load on those gears was equal to the load that bent the Magneto shaft.

Have any of you heard of this happening before?

I am going to have a sizable bill coming. And a new found fear of flying. I am getting myself over the fear quickly thanks to a 10 hour drive home in Thanksgiving traffic. But as far as the bill goes, is this something that I could submit to insurance?

If the log book shows anything funny with the magneto inspection or whatever is anybody prior to me accountable? I am going to get my log book later today and am fedexing it up to the mechanic for him to pick through it.

Or is this whole thing just a rare event that I need to suck up with plane ownership?
Click to expand...

I wouldn't fly that engine until it was disassembled cleaned and inspected for metal debris, and the main and rod bearings replaced. IOWs overhauled.
 
Unregistered said:
Got the logs. The engine has 451 hours Since it was overhauled in '99. The Slick Magnetos were removed, cleaned, and inspected at this time. The magnetos were replaced with new ones in 1983. The engine was originally overhauled in 1984 with 1700 hours on it at that time. When it was overhauled in '99 it just had a little under 500 hours SMOH on it.

So these magnetos have almost 1000 hours on them.
Click to expand...

IOWs they were pulled inspected, and returned to service, dumber that a box o rocks, mags are designed to run to TBO and then replaced.

Pay heed folks,, I pays to replace the appliances at overhaul.

If you can't afford to do it right the first time, how can you afford to do it over again?
 
As far as finding this on an annual? this mag would have never passed the run up after the inspection.

you can't convince me that this was giving you a good mag check prior to this.
 
Unregistered said:
Ron, from what I can tell it says these need to be replaced at 800 hours. Is this something an AI would turn up at the annual inspection or is this something I should have known as the airplane owner?
Click to expand...
As Anthony said, both. A good IA should be checking SB's as part of an annual, but as the owner/operator, you are ultimately responsible for knowing what inspections should be performed and when. Note that unless they are incorporated in an AD by the FAA, you as a private operator are not required to comply with SB's -- that's a decision you have to make for yourself. Also, an IA doing an annual in your private plane is not required to comply with SB's not incorporated in an AD. However, I would consider negligent any IA who doesn't bring to the owner's attention any relevant non-AD SB's so the owner can decide whether to comply with them or not.
 
Ron Levy said:
As Anthony said, both. A good IA should be checking SB's as part of an annual, but as the owner/operator, you are ultimately responsible for knowing what inspections should be performed and when. Note that unless they are incorporated in an AD by the FAA, you as a private operator are not required to comply with SB's -- that's a decision you have to make for yourself. Also, an IA doing an annual in your private plane is not required to comply with SB's not incorporated in an AD. However, I would consider negligent any IA who doesn't bring to the owner's attention any relevant non-AD SB's so the owner can decide whether to comply with them or not.
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Went to pick up Comanche on 9 Nov and checked the write up and there was no sign off of the 2012 Comanche stab horn AD. Now, I had AMOC on the thing with one of guys who worked intimately with FSDO on the AD replaced all the parts with new and did the full AMOC since he wrote it, but it was not signed off. I cannot believe that I needed to point that out to the IA who is heavily computerized - and then looked at the log entry from the AMOC in 2010 and pencil whipped it - he then got the re inspection date wrong.

I pointed that out - we chatted about it and he agreed with me that the date is 10yr/1000hrs from the date the work was done not the date it was signed off . . . .

So yeah, you gotta know your airplane.

Every owner needs to spend some dinero with an IA they trust going over their books and understanding the nature of applicable ADs and other inspections, what the symptoms are leading to reason for hte AD, and the work that is need for compliance and when - and then look back at your airplane to match it all up. Otherwise, you are test pilot and the FAA can prob ground you at any time - the FAA would have tough time finding paperwork reasons to ground me. . .
 
This mag actually worked fine at every runup I have ever done. A slight 50-100 RPM drop like the other the static runup is fine, and it has performed well in flight.

I found some documentation today that said that the Mags should never be used beyond TBO of the engine. In my case this engine had 2 overhauls in the time that these mags were on the plane.

This has really been a learning experience. The shop that has the engine now has questioned how much I want to spend to get the engine going again since the engine is beyond the 12 year recommended TBO.
 
I don't have any experience with aircraft engines, but a worn distributor bearing on a car -- which it seems is the thing that failed here -- is next to impossible to find without a timing light, until it either fails or takes out a distributor-mounted sensor or the breaker points. The engine will run very slightly roughly, due to the timing changing.

It might make some interesting noises, but you can't even hear those in a car with the hood down, let alone in an aircraft engine with a noisy prop up front.

The one place where it would show up early is in a used oil analysis. Was this done? At least, was the oil filter cut open and a magnet run through it? The worn/broken magneto shaft teeth went somewhere. They may be sitting in the bottom of the oil sump, but there are probably a lot of fine ground up bits in the oil, too.
 
Ted DuPuis said:
I'm guessing these were Slick mags, and this is why I won't put a Slick on a plane I am in charge of. Too many cases of Slick mags failing. If it was a Bendix mag, those do fail as well, just not as often.

Large bills are a cost of ownership, and unfortunately they do occur. In the turbine world, there are programs one can be on to try to make your engine costs known in advance where you pay a fixed hourly cost for engine maintenance. I've wondered if such a program in the piston world would work, and I'm guessing probably not. The planes that would benefit the most aren't flown often enough for there to be much money in it.

I'm not sure it would have killed you. Depending on how it ended up failing, it may have had the occasional bad spark. You just don't know.

Good thing you caught it on the ground, though, or you would have found out.
Click to expand...

Turbines you can do it because the engines regulate themselves LOP, recips you give the pilot too much opportunity to cause damage and cost money. Turbines you basically have a hot start.
 
Henning said:
Turbines you can do it because the engines regulate themselves LOP, recips you give the pilot too much opportunity to cause damage and cost money. Turbines you basically have a hot start.
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Turbines also tend to operate more than pistons, so you don't have damage from sitting. It's pretty rare that a turbine only flies 5 hours per year.

For it to work with pistons, you'd need to have some pretty strict rules to make it work. FADECs would be ideal.
 
MAKG1 said:
The one place where it would show up early is in a used oil analysis. Was this done? At least, was the oil filter cut open and a magnet run through it? The worn/broken magneto shaft teeth went somewhere. They may be sitting in the bottom of the oil sump, but there are probably a lot of fine ground up bits in the oil, too.
Click to expand...


The magneto has factory-lubricated ball bearings in it. Engine oil does not reach them. On some mags there's an opening in the bottom of the mag, between its forward bearing and the shaft's oil seal, so that engine oil can't get into the mag.

From the symptoms and observed damage, I would suspect that the ball bearings corroded and finally failed. I have seen this in an older Bendix mag, where the inside of the ball bearing isn't sealed and moisture can get into it and mix with the grease, forming acids that eat the balls and races. Eventually they chew up the ball spacer and jam the whole thing. This sort of thing is more related to calendar time than hours in operation; too many folks don't realize that the airplane rots away whether it's flown or not. Low hours are no guarantee of life expectancy.

The Slick sure can be a troublesome mag but I never had any problems with their bearings, but of course this was in a busy flight school where the mags never got more than five or six years old, often only three years, and the airplanes were hangared every night. Slicks tend to suffer more from poor quality control.

Dan
 
I dunno...

Reading through these posts, and coming to the conclusion that the maintenance and inspection history with regard to the mag may have been less than wonderful, I don't know that I'd be bad-mouthing the mag or its manufacturer too much.

-Rich
 
If that was a 'left over' mag from overhaul in 99, think of the service life you got out of it.
 
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Yes, I know it is an old thread. To the OP, thank you for posting this thread. I am coming up on 500 hours on my slick mags right now. That is 500 hours since NEW in my case. It is overhaul or replace time for me!

Jim
 
Kiddo's Driver said:
Yes, I know it is an old thread. To the OP, thank you for posting this thread. I am coming up on 500 hours on my slick mags right now. That is 500 hours since NEW in my case. It is overhaul or replace time for me!

Jim
Click to expand...

500 hour inspection should do it, unless they have a lot of years on them. There are also several Slick SBs that should be addressed at that time. Slicks do have quality control issues and I have found numerous problems in brand-new mags that weren't running right. Their design is OK; it's the guys in the factory that aren't.


Dan
 
Dan Thomas said:
500 hour inspection should do it, unless they have a lot of years on them. There are also several Slick SBs that should be addressed at that time. Slicks do have quality control issues and I have found numerous problems in brand-new mags that weren't running right. Their design is OK; it's the guys in the factory that aren't.
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Not sure the 500 hr inspection would catch it.

Funny thing about this resurrected thread is that about two weeks after the OP posted this, I had my right mag failure in the 170 bringing it across the country.

In my case ((also Slicks), the internals seized up and the gear tooth broke off in flight. I ended up needing a full tear down inspection of the engine. I had about 75 hrs since the 500 hr inspection.
 
Fearless Tower said:
Not sure the 500 hr inspection would catch it.

Funny thing about this resurrected thread is that about two weeks after the OP posted this, I had my right mag failure in the 170 bringing it across the country.

In my case ((also Slicks), the internals seized up and the gear tooth broke off in flight. I ended up needing a full tear down inspection of the engine. I had about 75 hrs since the 500 hr inspection.
Click to expand...

The 500 won't catch the factory screwups too often. Those are caught when one pays attention to the SBs and the engine's behavior. When I was looking after six or eight flight school airplanes, all but one with Slicks, any roughness of a new engine automatically meant a mag inspection. Any roughness in that first 500 hours meant a mag inspection.

As Tom says, a Bendix would be better. But since the Chinese now own TCM, makers of Bendix ignition systems, what will happen?

By the way: If a mag's external drive gear has broken teeth I sure wouldn't trust the engine's gears anymore. They can look fine, but can have cracks in the roots of the teeth and fail later on. They need to be removed and run through non-destructive inspection.

Dan
 
Ouch, I know the feeling.....

The ball bearings Dan mentions are held in place by a washer like retainer. About 2 months ago we lost a lot of oil on one flight. We looked for where it went and found a leak from the base of the mag. Pulled the mag and the retainer was missing. Hummmm...

We had 1950 on the engine, and about 900 on the mags (replaced a few years ago). About 75 hours since it had been in a shop for anything other than an oil change. Worst part was we didn't know where the retainer was! We went looking and found mangled pieces equal to about 75% of it in the oil pan. Since something had mangled it, and pieces were still missing we had to do a teardown. At 1950 we just used the really expensive airplane words "might as well" and did an overhaul.

Problem will be if you can't find the missing teeth they could be inside lurking....
 
Dan Thomas said:
500 hour inspection should do it, unless they have a lot of years on them. There are also several Slick SBs that should be addressed at that time. Slicks do have quality control issues and I have found numerous problems in brand-new mags that weren't running right. Their design is OK; it's the guys in the factory that aren't.
Dan
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New in 1998. Serial numbers start with 9804 & 9805, April of 1998 & May of 1998 respectively.

I thought I had found SBs that cover those previously. I cannot find any right now. :confused:

Jim
 
Kiddo's Driver said:
New in 1998. Serial numbers start with 9804 & 9805, April of 1998 & May of 1998 respectively.

I thought I had found SBs that cover those previously. I cannot find any right now. :confused:

Jim
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Don't even fool with these old mags, order a set of rebuilds from TCM over the counter parts sales, get two harness too.

OBTW the trash can be removed best from the sump by removing it and cleaning the metal out. the trash from the failure will not stay in the accessory case on the 0-360 it all will be in the lower oil sump.
 
RJM62 said:
I dunno...

Reading through these posts, and coming to the conclusion that the maintenance and inspection history with regard to the mag may have been less than wonderful, I don't know that I'd be bad-mouthing the mag or its manufacturer too much.

-Rich
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I agree Rich, no need to bad mouth Slicks.

Slicks should be overhauled at 500 hours, at least mine are, these went twice that? Why? Because the mag check was still good? :mad2:

I have them rebuilt, not by an A&P. I have a certified shop perform the work, or they are replaced. Even though I could do it, I would rather have the shop do it. They have the equipment to bench test it when it is done.
 
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Tom-D said:
Don't even fool with these old mags, order a set of rebuilds from TCM over the counter parts sales, get two harness too.

OBTW the trash can be removed best from the sump by removing it and cleaning the metal out. the trash from the failure will not stay in the accessory case on the 0-360 it all will be in the lower oil sump.
Click to expand...

Trash??? What trash? Mine are 15 year old "new" magnetos with 500 hours on them. They did not self destruct and end up in the accessory case or the engine.

They run great "right now", but are not going to stay on my plane without at least a 500 hour inspection.

Jim
 
Kiddo's Driver said:
Trash??? What trash? Mine are 15 year old "new" magnetos with 500 hours on them. They did not self destruct and end up in the accessory case or the engine.

They run great "right now", but are not going to stay on my plane without at least a 500 hour inspection.

Jim
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You must not be the guy who is looking for two teeth in the accessory section.

TCM is the best choice since Slick starting having problems, TCM can be serviced in the field with all new parts from TCM and several other parts stores.
 
I prefer TCM mags, but have a hard time throwing out good or even repairable parts as pricy as mags. I went to TCM mags a couple years ago from my OE (1983) slick but they were starting to show timing drift and were a little "dated"
 
Tom-D said:
You must not be the guy who is looking for two teeth in the accessory section.

TCM is the best choice since Slick starting having problems, TCM can be serviced in the field with all new parts from TCM and several other parts stores.
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Nope, I'm the guy that was thinking to myself "Geeze, do I really have to spend $400 per magneto to do a 500 hour inspection?" After reading this and other threads I thanked the OP for posting.

I'm at the point that the very LEAST I am going to do is the 500 hour inspections. The most I'm looking at putting an Electroair system on one side and either a rebuilt Slick or a TCM on the other.

Are mine old enough that they are from before there were a bunch of issues? I cannot find any SBs or ADs on mine.

Ever used these guys? http://www.aeroaccessories.com/mags.html
They say they have PMA parts that they use to rebuild magnetos instead of using Slick parts.

Jim
 
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