Magneto failure at 9000ft

[wings_level]

I posted this on facebook, thought I would share it here as well. 

In flight the engine starts running a little rough.  Landed and took off the cowling, the screws came out of the left magneto casing and it was in half. Picture shows exactly how it looked when I removed the cowling.  This was on a C model with Bendix mags.  The 500 hour inspection occured 400 hours ago.  I think its time to go ahead and inspect the other mag too.

After further investigation, the gear that attaches to the mag that goes in to the back of the engine and gears up to the idler gear in the engine has a small chip missing due to the mag bouncing around in flight after it split in half (the idler gear appears to be good shape though).  Gonna pull the oil screen and hope we find it. Don't want it making its way through the engine. 

[Piloto]

Check for worn thread before installing mag back. You may want to use Loctite 271 on the screws next time.

José

[carusoam]

Great pic, 

Tough first post, WL.

 

Question for the mechanically inclined...

Is that similar to what happens when star washers get re-used?

Best regards,

-a-

 

[kmyfm20s]

I recently had a magneto failure. After my last one I watched the Mike Busch webinar on magneto's. In his webinar talked about 25 people that he consulted that had magneto failures. They where a mix of pilot experience levels from I believe military, Airline, CFI,ect.  He asked them all if they did a magneto check to select and run on the good magneto only. All of them did not and continued to run on both magnetos when it was only one causing the problems. I have to admit that I was guilty of this in all 3 of my failures and in my last one in particular I wish I did. I must of had some internal arching because 1 of my CHT's climbing sky high and could have been a serious emergency if I hadn't been close to the airport to land. After hearing this I went and checked my POH and sure enough in the emergency procedures for rough running engines it was there. 

[Guest]

I’m only guessing but there must have been a few annuals since the 500 hour inspection, magneto timing checked or adjusted?  I find I surprising that it wasn’t notice earlier.

Clarence

[jaylw314]

31 minutes ago, kmyfm20s said:

I recently had a magneto failure. After my last one I watched the Mike Busch webinar on magneto's. In his webinar talked about 25 people that he consulted that had magneto failures. They where a mix of pilot experience levels from I believe military, Airline, CFI,ect.  He asked them all if they did a magneto check to select and run on the good magneto only. All of them did not and continued to run on both magnetos when it was only one causing the problems. I have to admit that I was guilty of this in all 3 of my failures and in my last one in particular I wish I did. I must of had some internal arching because 1 of my CHT's climbing sky high and could have been a serious emergency if I hadn't been close to the airport to land. After hearing this I went and checked my POH and sure enough in the emergency procedures for rough running engines it was there. 

You've had 3 mag failures in flight?? 

[Hank]

My left magneto also died at 9000msl this time last year. There's a thread about it somewhere, I noticed my EGT was higher than peak . . .

This was when I learned to talk to my wife in the right seat about what's happening,  because I didn't say anything, just turned the key one click to Left and the engine quit, pitching down noticeably. 

Continued the flight on the Right mag only. Visual inspection found nothing. Plug inspection and cleaning found nothing, wouldn't start until I released the key. Opened the magneto and found cut condenser wire and signs of arcing. Shipped out magneto, drove 9 hours home. 

Good luck with your repair!

[kmyfm20s]

51 minutes ago, jaylw314 said:

You've had 3 mag failures in flight?? 

Yes. The first one was when I was a student pilot in a 172. I was doing pattern work on a hot summer day and I was turning Cross wind still climbing and it went out. It started running really rough and wouldn't climb anymore. I finished the pattern at about 300" AGL and landed.

The 2nd was in my 201 when I was flying it from San Diego to All American Aircraft in San Antonio to sell my plane. I stopped in Glendale AZ to visit a friend for the night. When I did my run up in the morning it was running rough so a taxied over to the MSC on the field. The Mechanic convinced me it was a bad ignition key and that was OK to fly so I took off and finished my flight. It actually ran smooth in flight under power so I didn't think anything about it with exception of slightly higher EGT's. The amazing thing was I was getting great airspeed. When i pulled back the power to descend was when it caught my attention, backfiring and sputtered all the way in. It was really embarrassing when I taxied into Landmark being directed by the lineman and all people where boarding their private jets as I was sputtering and backfiring into my spot. 

The last one was when I took off from Mammoth which is at 7300' MSL and was climbing out.  The engine started to run really rough, enough that my girlfriend who fly's a lot with me looked over and you could tell she was nervous. This is the flight I really wish I had turned off the bad magneto. Not only to make her more comfortable but because I had 1 CHT climbing fast at it got hot. It could have been a serious issue if left the way it was.  I immediately pulled back the MP and enriched the mixture, which helped, then turned back to the field and landed safely but it spooked me. 

All 3 of these the plane would have ran smoother and have protected the engine better if the bad magneto was turned off. Regardless thank god for redundancy!

[Yetti]

Seems like your oil line is missing some firesleeve also

 

[MB65E]

Welcome WL!! 

Looks like things will work out. At least you have bendix mags back there.

Firesleeve is nice but not required. However, Id highly recommend it.

Hope your mags come back soon!!

-Matt

[Nomad Pilot]

Believe what you want , but IMOP everything Mike Bush says should be taken with a grain of salt!


Sent from my iPhone using Tapatalk

[kmyfm20s]

1 hour ago, Nomad Pilot said:

Believe what you want , but IMOP everything Mike Bush says should be taken with a grain of salt!


Sent from my iPhone using Tapatalk

I do but his statement about people not thinking to shut down their bad mag resonated with me and I thought it was worth sharing. I hope it helps someone else.

[L. Trotter]

On the topic of "Mag checks" during run-up......perhaps common knowledge to some.

For those who have EGT monitoring on each cylinder, make sure to watch for an EGT rise on each cylinder when running on only 1 mag. This rise is normal and should decrease back to normal (baseline) when back on both mags. This finding is in addition to the normal expected RPM drop.  So, If you don't have the expected EGT rise, something isn't right. Yes, you will have to slow down your Mag check to let RPM and temps stabilize, usually only 5 seconds or so.

[ragedracer1977]

Looks just like my mag that came apart.  Less than 100hrs since new

[ArtVandelay]

Yes. The first one was when I was a student pilot in a 172. I was doing pattern work on a hot summer day and I was turning Cross wind still climbing and it went out. It started running really rough and wouldn't climb anymore. I finished the pattern at about 300" AGL and landed.
The 2nd was in my 201 when I was flying it from San Diego to All American Aircraft in San Antonio to sell my plane. I stopped in Glendale AZ to visit a friend for the night. When I did my run up in the morning it was running rough so a taxied over to the MSC on the field. The Mechanic convinced me it was a bad ignition key and that was OK to fly so I took off and finished my flight. It actually ran smooth in flight under power so I didn't think anything about it with exception of slightly higher EGT's. The amazing thing was I was getting great airspeed. When i pulled back the power to descend was when it caught my attention, backfiring and sputtered all the way in. It was really embarrassing when I taxied into Landmark being directed by the lineman and all people where boarding their private jets as I was sputtering and backfiring into my spot. 
The last one was when I took off from Mammoth which is at 7300' MSL and was climbing out.  The engine started to run really rough, enough that my girlfriend who fly's a lot with me looked over and you could tell she was nervous. This is the flight I really wish I had turned off the bad magneto. Not only to make her more comfortable but because I had 1 CHT climbing fast at it got hot. It could have been a serious issue if left the way it was.  I immediately pulled back the MP and enriched the mixture, which helped, then turned back to the field and landed safely but it spooked me. 
All 3 of these the plane would have ran smoother and have protected the engine better if the bad magneto was turned off. Regardless thank god for redundancy!

What kind of Magnetos were these?

[kmyfm20s]

1 hour ago, teejayevans said:

What kind of Magnetos were these?

I’m not sure what type magneto was in the first 172 I trained in. The second one was in my old M20J which have the Bendix D series. The third one was in my current M20S which is the Bendix 1200 series. 

[MooneyMark]

Welcome WL, I'm not much help for you, had one mag failure but found out during run-up. I hope it all works out for you! For the other posters: how come the EGT goes up with one faulty mag? I'd imagine less mixture being burnt and thus a lower EGT...?

[Yetti]

9 hours ago, MB65E said:

Firesleeve is nice but not required. However, Id highly recommend it.

 

Firesleeve is not required till you have a fire in the engine compartment and then you would really really like to have it.  There is also a ty Wrap on the engine mount tubing.  Might want to replace with tied cord. 

Some A&Ps would suggest the 4 screws that hold the mag cap on be replaced with allen head screws.  Much easier to get an allen wrench/ratchet with allen head adapter in that tight place than a short flat bladed screw driver.  Which might be what caused the mag cap to fall off in the first place.

[Guest]

New screws, with new lock washers and a torquing screw driver should be all that are required to keep it from falling apart.

Clarence

[Marcopolo]

@MooneyMark,

 

  Running on a single plug slows the burn event down allowing the still burning mixture to make it further into the exhaust, thus causing the higher EGTs.

 

Ron

[ArtVandelay]

I’m not sure what type magneto was in the first 172 I trained in. The second one was in my old M20J which have the Bendix D series. The third one was in my current M20S which is the Bendix 1200 series. 

Interesting, since many recommend getting rid of the Slicks and going to Bendix because of their quality.
Makes me even more interested in EI.

[kmyfm20s]

28 minutes ago, teejayevans said:

Interesting, since many recommend getting rid of the Slicks and going to Bendix because of their quality.
Makes me even more interested in EI.

All magnetos fail. The slick magneto from my understanding are not worth overhauling because the cost is close enough to buying a new that it’s not worth it. The new ones are more reliable than the rebuilt, so I hear. The Slicks are also generally smaller and not as good for higher altitude operation and tend to arch internally, unless pressurized. With the Bendix you are able to get a higher quality overhaul and the cost for new is much higher. I think that’s why the term “throw away mag” came about for Slick magnetos. To sumerize my understanding, comparing new Slick’s vs either overhauled or new Bendix you will have comparable reliability but Bendix will generally perform better. 

[wings_level]

I agree.  And also, from my understanding, the Bendix uses something other than an impulse coupler (not sure what it's called) on the starting mag.  From what I have been told that generally performs better in starting than the impulse coupler in the Slick mags.

[jetdriven]

Bendix mags can use an impulse coupler or a shower of sparks. 

[cliffy]

carusoam- no not the same look but the mode of failure is the same- lack of changing the lock washers when removing the mag hold down nuts or body screws. 

The star washers are on the mag mounting studs so the entire mag falls off the back of the engine, not just the body coming apart. 

Picky, picky but we are never to reuse locking devices like lock washers and safety wire BUT virtually everyone never replaces the lock washers on the mag body screws when they come apart in the field.