Cursed Dual Mag?

[rangermb]

I posted this in the Facebook group as well...

Starting to feel cursed...

I have a dual mag on my 77J. It was rebuilt with the engine about 300 hrs ago. About 50 hrs after rebuild the left points burned out. Replaced the points and 25 hrs later they burned out again. Had the mag rebuilt. About 60 hrs later the drive gear disintegrated. Another rebuild. This week, about 60 hrs later, the mag has failed again (still waiting on diagnosis). 

Trying to decide if the gremlins are worth chasing and just get a replacement mag

Opinions?

[toto]

For what it's worth, Kelly actually makes brand-new D3000 mags today if you want one.

http://kellyaerospace.com/airplane-engine-products/aircraft-magneto/

HT to PT20J for correcting me on this point.  I've misunderstood the difference between an overhaul with new parts and a new unit.  Here's what Kelly's product page says..

 

[EricJ]

Mine will be due for 500-hour inspection in about 30 hours.   Kelly Aerospace will do an overhaul on an exchange and I've been going to call them about their 500-hour service.  qaa.com is an alternative.

 

 

[RLCarter]

The condenser (capacitor) keeps the points from burning up.... there is an AD on your mag on the condenser 

[rangermb]

Wonder what they want for the new units? (Pretty sure mine is a D2000)

[PT20J]

55 minutes ago, rangermb said:

Wonder what they want for the new units? (Pretty sure mine is a D2000)

D3000 is an upgraded version. http://crossfiremagneto.com/Crossfire_Magneto_Service/Welcome_14.html

If done correctly, an overhaul should not have the kind of failures you are seeing, but there are fewer shops that are knowledgeable about these mags than there used to be especially since TCM bought the Bendix line and discontinued support. https://www.aircraftmagnetoservice.net/dual-magnetos

Kelly is a PMA parts supplier and overhauls the dual mags. They have overhauled/exchange units. Lycoming supplies overhauled dual mags with factory rebuilt engines since they can’t get new ones.

Skip

 

[cferr59]

We had an issue with a D3000 on an O-540-J3A5D.  Kept having hot start issues, various troubleshooting, overhauled the magneto, still had hot start issues.  More troubleshooting, could not find a problem.  Bought a new magneto, issues resolved.  With that history, I would want to exchange it or buy a new one.

[GeeBee]

I said it before and I will say it again (and I've taken a lot grief here). I don't fool around with O/H mags for any airplane. I go one 500 hr IRAN then I buy new. So much less trouble, so much better performance.

 

[jetdriven]

I’m not even sure if they sell the D3000 new anymore

[DXB]

1 hour ago, GeeBee said:

I said it before and I will say it again (and I've taken a lot grief here). I don't fool around with O/H mags for any airplane. I go one 500 hr IRAN then I buy new. So much less trouble, so much better performance.

 

Exactly.  I had to learn the hard way as well.

[PT20J]

A properly overhauled mag should be as good as a new mag. However, Slick mags are generally considered disposable since it costs more to overhaul one than to buy a new one. Opposite is true for Bendix mags. 

https://www.aircraftmagnetoservice.net/overhaul-details?keyword=aircraft+magneto+service

Skip

[toto]

2 hours ago, jetdriven said:

I’m not even sure if they sell the D3000 new anymore

Kelly does - link above.

[PT20J]

Kelly only sells overhauled, not new. There are no new mags since TCM stopped making them. In fact, TCM stopped supporting them entirely making parts difficult to obtain which is why some shops quit overhauling them. Kelly makes PMA parts to support overhaul, but if the case was cracked or corroded you were done until recently when Kelly got approval for PMA cases. If I still had a dual mag, I’d only do an overhaul/exchange with Kelly. You really want it done right because it can be a single point of failure.

Skip

[toto]

19 minutes ago, PT20J said:

Kelly only sells overhauled, not new. There are no new mags since TCM stopped making them. In fact, TCM stopped supporting them entirely making parts difficult to obtain which is why some shops quit overhauling them. Kelly makes PMA parts to support overhaul, but if the case was cracked or corroded you were done until recently when Kelly got approval for PMA cases. If I still had a dual mag, I’d only do an overhaul/exchange with Kelly. You really want it done right because it can be a single point of failure.

Skip

Interesting.  I completely misread their materials then.  So they are PMA approved for the case and for components, but technically the new Kelly case with the new Kelly components is still an overhauled Bendix mag?  (Are there any components of the original Bendix mag that Kelly can't produce under PMA?)

[EricJ]

Kelly says they make all new parts for the dual mags, and even says the frames they make out of aluminum are superior to the Bendix magnesium frames as well as improved distributor and gears.    So whatever overhaul needs you may have, you can get a dual mag from Kelly.   They'll sell you one without a core return if you don't care about the core charge.

 

[PT20J]

6 minutes ago, toto said:

Interesting.  I completely misread their materials then.  So they are PMA approved for the case and for components, but technically the new Kelly case with the new Kelly components is still an overhauled Bendix mag?  (Are there any components of the original Bendix mag that Kelly can't produce under PMA?)

Clearly, Kelly has invested heavily in the dual mag market. They may well have enough PMA parts to build a new mag — you’d have to ask them. But it would be expensive to get a PMA for an entire magneto, and I can’t imagine there is enough of a market to justify it. 

[Captnmack]

I was looking at bidding on that J that was in TN. I was disappointed in hearing that it had this Magneto. My thought was to pull the Engine and swap out the Accessory Case to support dual mags....

[N201MKTurbo]

I’m thinking about buying the overhaul tools. They cost about $1000.  And building a test stand with the servo motor junk I have.  Maybe I’ll even talk to my friends at the FSDO about becoming a repair station. 

[EricJ]

2 hours ago, Captnmack said:

I was looking at bidding on that J that was in TN. I was disappointed in hearing that it had this Magneto. My thought was to pull the Engine and swap out the Accessory Case to support dual mags....

Personally I don't think there's anything to be afraid about, like touch-n-goes.   There are some advantages to the dual mag, like better starting spark.   

[PT20J]

2 hours ago, Captnmack said:

I was looking at bidding on that J that was in TN. I was disappointed in hearing that it had this Magneto. My thought was to pull the Engine and swap out the Accessory Case to support dual mags....

That won't work. There are a lot more differences between the A3B6 and the A3B6D than just the accessory case. You cannot convert one to the other. At least that's what Lycoming told me when I asked about it.

[PT20J]

Just now, bluehighwayflyer said:

Plus one. And the ability to run with 25 degree timing.  I have more confidence in the Bendix “dual” mag than I do in a Kelly Aerospace overhaul, personally.  

You can run the A3B6 at 25 degrees also if you want. You just change out the left mag for one with the proper lag angle and restamp the data plate. 

[N201MKTurbo]

28 minutes ago, PT20J said:

That won't work. There are a lot more differences between the A3B6 and the A3B6D than just the accessory case. You cannot convert one to the other. At least that's what Lycoming told me when I asked about it.

You are correct the gear bosses in the crankcase are different too. Plus you would need new gears, which are $$$$ very spendy.

[EricJ]

2 hours ago, N201MKTurbo said:

I’m thinking about buying the overhaul tools. They cost about $1000.  And building a test stand with the servo motor junk I have.  Maybe I’ll even talk to my friends at the FSDO about becoming a repair station. 

If you hurry up I might be your first customer. 

[N201MKTurbo]

14 minutes ago, EricJ said:

If you hurry up I might be your first customer. 

Well, I wouldn't hold your breath. I wish i could be there for you. I will get to it as soon as I get the Mooney engine back together, the annual complete and the Cessna fixed up and sold.

Maybe the next 500 Hr....

[Schllc]

9 hours ago, GeeBee said:

I said it before and I will say it again (and I've taken a lot grief here). I don't fool around with O/H mags for any airplane. I go one 500 hr IRAN then I buy new. So much less trouble, so much better performance.

 

Couldn’t agree more. 
left for a trip with my family a few summers ago, and May failed shortly after takeoff. 
landed back at my field and priced out all the options. 
The plane was 12 years old, and the family didn’t enjoy the experience anymore than I did....

turned out if you bought two new mags, harness and plugs as a package is was only about $800 more than rebuilding the two mags  The mechanic actually tried to talk me out of it, said it was all unnecessary.  Perhaps it was, but I would do the same thing over again, every time.

For me, an airplanes ignition source is no place to save a few sheckles.