Mag overhaul 1978 J model

[nels]

Not sure what to do here? I'm having no trouble at all but hear stories about these mags that worry me. Anybody know what the cost is to overhaul them or should I just fly it and not worry about it? I'm considering pulling mine and sending out for rehab just to feel more comfortable in the air. I see in my logs that they were changed out about 700 hrs ago from the 2000 to the 3000 series. Without pulling the logs I think that was the model number. Plane and engine have about 1200 hrs total time. Is it a bear to change out? My mechanic seems to be willing to watch over my shoulder,, in fact he seems to prefer it when it's in a difficult location.

[DonMuncy]

It is really not a great idea to overhaul/IRAN both at the same time. Have one done, and wait as long as you dare (preferably 250 hours) and have the other one done. From then on, have each one IRANed every 500 hours.

[DonMuncy]

4 minutes ago, bluehighwayflyer said:

He only has one mag, Don. The D4LN-3000 "dual" mag. Agreed, otherwise, though. 

Jim

I couldn't tell from his post. I am not near knowledgeable enough to recognize it from the model number. (Even if I had seen it before; I can barely remember my middle name.)

[Mjknick@gmail.com]

500 hours is the deal. Don’t gamble $1400 to overhaul or so. I changed the distributor block which will go bad I had one and dead sticked it back to my home airport. Change the block at 1000 hours and due normal overhaul at 500 points and such. Your mechanic can’t guarantee anything and that’s total BS. 19000 hours with no major problems ATP CFIIMEI Please overhaul these mags at reputable facility.


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[Mjknick@gmail.com]

Do not due


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[jetdriven]

Select aircraft is perhaps one of only two ot maybe 3 places that will do this mag and it will come back and run another 500 hours trouble free.  Seeing as how it’s everything in one unit and if it quits you crash, there is no room for good enough, it has to be perfect. 

[Guest]

The D3000 series magneto is as reliable as the current offerings from Champion/Slick as long as you maintain it and have someone competent install it.

When you send it out be sure to send the two condensers which are in the wire cap.

When you reinstall it you need a new gasket LW12681 and two new 66M19385 clamps and two new MS38335-41 lock washers.  

Although not required I also install a PAL Nut on each stud MS27151-16.

The nuts are torqued to 204inch pounds.

Clarence

[skykrawler]

After I purchased my M20J with 1500hr engine I replaced the original wires and sent the dual magneto to http://www.eaglemagneto.com/ for an inspection.  Shaun replaces anything that needs replacement and will let you know beforehand.   I've used him for a C172N dual mag and now my IO360 dual mag - last was ~$900 including distributor block replacement.  He supplied several new gaskets.  Excellent turnaround time.

It's nice to have options.

[N201MKTurbo]

For some reason my mag seemed to wear points quicker than it should. I pull the cap and look at the gap every annual and if it looks suspect I will pull the mag and inspect the points and reset the internal timing. I end up replacing the points about every 200 hours. They are cheap by aviation standards. 

I have had this mag overhauled twice sense I've owned it. In both cases the internal timing was not close enough for my liking when I got it back so I reset it befor I installed it. I like to get it so both points open at exactly the same time. This is tedious and if one of the gaps is out of spec you have to re-clock the cam. It is worth it it will make your mag drops perfect and your engine will idle better.

[jetdriven]

Just be sire to replace that special 3$ breaker point cam screw every time you back it off to adjust the cam.  If it backs out, the cam comes loose, the mag quits. The E-gap was off quite a few degrees and I went through 3 or 4 of them when I did the 500-hr mag inspection last annual.

Edited December 23, 2017 by jetdriven

[Bartman]

I'm just an interested owner and have never worked one one the dual mags so excuse my ignorance. Are they really that complicated or require special tools to service ?  Does everyone send the out to a specialty shop ?  I know we're have a lot of A+P guys here and just wondering does anybody work on them or does everyone send them out ?

[Marauder]

I'm just an interested owner and have never worked one one the dual mags so excuse my ignorance. Are they really that complicated or require special tools to service ?  Does everyone send the out to a specialty shop ?  I know we're have a lot of A+P guys here and just wondering does anybody work on them or does everyone send them out ?

 

Yeah, it does make you wonder. They sure look like the magnetos I had on my Ford 8N tractor. And this hick from the sticks didn’t have a tough time rebuilding them.

 

So what about electronic replacement equivalents. What’s out there?

 

 

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[Bartman]

6 minutes ago, Marauder said:

 

Yeah, it does make you wonder. They sure look like the magnetos I had on my Ford 8N tractor. And this hick from the sticks didn’t have a tough time rebuilding them.

 

So what about electronic replacement equivalents. What’s out there?

 

 

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Sounds like a good poll. Should Provide some entertainment and be very informative for a couple of days. Hold on...

[Marauder]

Sounds like a good poll. Should Provide some entertainment and be very informative for a couple of days. Hold on...

Just make sure you add in ROP/LOP and flaps/no flaps to really spice it up.


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[nels]

So, what is the failure when they fail?? What is the catastrophic event that terminates flight? Is it a gear train failure?, a wire that breaks., a cam lobe that wears out?, a bushing that fails?? If I do end up pulling the mag I would like to know what to look for. Are all failure points visible when removed or does the mag need to be disassembled to properly inspect? I did take a closer look at my logs this morning and see that the mag has been removed several times since replacement. A recent log book entry mentioned changing the points and felt and lubing the block. I assume the block is the cam lobe that actuates the points?

[N201MKTurbo]

I've never had one fail in flight. Twice I have found a dead mag at run up. In both cases it was just a point adjustment.

When the mag is hot the gap is bigger by a tiny bit so it makes sense that the failure would be detected first with a cold engine.

[mooneyflyfast]

Yes you need to have it gone through by a shop that does a lot of them. It's not a place to save money.. Yes It'sa bear to remove and replace--just look at it and you can see why. Not a do-it-yourself project. As others have pointed out proper installation is critical. If your mechanic doesn't want to do it or doesn't know to do it properly I would find someone who does. 

[Bob - S50]

We had ours done at 500 hours.  Not too long after that we had one of the magnetos fails.  The pilot flying did not notice.  The next pilot found the magneto dead during his run up.  Turned out that one of the capacitors they sent us was bad which caused the points to arc which heated the riser so badly it melted.  Without the riser the points wouldn't open.

We had the capacitor and points replaced locally and it has worked fine ever since.

We still plan to have ours inspected every 500 hours.  However, Electroir has been working on an electronic replacement for our D3000.  If they have it certified before we need the inspection we will consider replacing it and avoid future inspections.

[nels]

Interesting. I know the capacitors in mine were changed at the same time the points were done so I guess they are fine.

[Guest]

4 hours ago, N201MKTurbo said:

I've never had one fail in flight. Twice I have found a dead mag at run up. In both cases it was just a point adjustment.

When the mag is hot the gap is bigger by a tiny bit so it makes sense that the failure would be detected first with a cold engine.

There you go ruining the myth about pre take off mag checks being useless.  You would feel better having the mag failure in flight.

Clarence

[jetdriven]

5 hours ago, nels said:

So, what is the failure when they fail?? What is the catastrophic event that terminates flight? Is it a gear train failure?, a wire that breaks., a cam lobe that wears out?, a bushing that fails?? If I do end up pulling the mag I would like to know what to look for. Are all failure points visible when removed or does the mag need to be disassembled to properly inspect? I did take a closer look at my logs this morning and see that the mag has been removed several times since replacement. A recent log book entry mentioned changing the points and felt and lubing the block. I assume the block is the cam lobe that actuates the points?

There are a few failure modes that are not limited to the Bendix Dual Magneto, but since it’s a single unit, can cause the whole mag to shut down or degrade. If the breaker point cam screw comes loose, the cam shifts or comes off the shaft it sits on, which causes both sides to fail. If the impulse coupler spring breaks it can cause the timing to roll back to zero, which probably won’t sustain flight. Plastic distributor gears can strip out and the pieces from that can get into the other side and strip it out too. Probably the biggest risk is the hold down clamps coming loose, allowing the timing to shift, or coming off which causes “bendix falls” where the magneto falls out of the case. I’ve seen it on a Slick mag equipped RV racer. I asked the pilot when’s the last time you adjusted the mag timing, the night before he said. He didn’t know you couldn’t reuse the star washers. 

The Continental service manual says do these things to do for the 500hr. And it’s critical they are followed accurately and done correctly.  This involves removing the distributor blocks and lubricating the bronze oilite bushings with a special procedure involving an oven and some special 80$ a can oil. And lube the magneto gears by rolling across a 1/16” thick strip of special 80$ magneto grease that was spread on a sheet of wax paper. And setting the point gap first then measuring the E-gap with a special tool and moving the breaker point cam to adjust the  E-gap.  I elected to replace the crappy PMA pointe with Genuine Continental OEM points. Those were like 55$ each.  Then replace all the felt washers and lube them too.  Anyways it’s not hard work but It requires about 300$ in supplies and about 120-150$ in parts typically. 

[Guest]

In my experience in correct installation is a far more common error than anything else.  Incorrect gaskets on all types of mags causing them to fall off, reuse of locking devices, insufficient torque on mounting nuts, obsolete mounting clamps, to name the more common issues.

Clarence

[Bartman]

Not long after I purchased 1TF we had two problems. First within the first 50-100 hours I had an oil leak due to loose Magneto. That mag had been rebuilt by an outside shop shortly before I bought, and installed by a well known shop. My local IA fixed that with new clamps, washers and gasket etc. About 100 hours later my Dual mag died.  No hint of a problem on previous flights, then I noticed high EGT across the board about half way thru a 45 min flight but I did not know enough to make the diagnosis in flight. It would not restart after landing but would backfire when I released the key from the start to the both position. Since we were away from home I ended up with an exchange an it was not cheap. Best I can remember the guy told me one of the plastic gears had missing teeth, but has been so long ago I don't remember. 

Since then I have been blessed with local guys who know the Dual Mags well and have serviced in house with no problems. We agreed to do it at 400 hours and no problems with 3 local services since my first one died. All of my problems were with the mag that was on it when I bought it which was done by specialty shop and installed by well know shop. 

[gacoon]

13 hours ago, Bob - S50 said:

We had ours done at 500 hours.  Not too long after that we had one of the magnetos fails.  The pilot flying did not notice.  The next pilot found the magneto dead during his run up.  Turned out that one of the capacitors they sent us was bad which caused the points to arc which heated the riser so badly it melted.  Without the riser the points wouldn't open.

We had the capacitor and points replaced locally and it has worked fine ever since.

We still plan to have ours inspected every 500 hours.  However, Electroir has been working on an electronic replacement for our D3000.  If they have it certified before we need the inspection we will consider replacing it and avoid future inspections.

Electroair has been working on this forever.  Have you heard some recent news on this?

[Bob - S50]

1 hour ago, gacoon said:

Electroair has been working on this forever.  Have you heard some recent news on this?

No.  Just what I heard last year at the Northwest Aviation Trade show.  I plan to find them and ask about the status at the next show in February.