Time for a new Mag

[gsxrpilot]

I jumped in the 252 yesterday to go get the O2 bottle filled for a long cross country planned for tomorrow. The run up was smooth and the take off roll uneventful. During the climb out, I noticed one hiccup and thought it might just be my imagination. But then the roughness started. I immediately was looking at distance to the runway and also at possible off field landing areas. Some quick troubleshooting while returning to the field seemed to indicate it wasn't a fuel issue.

I landed and noticed the engine smoothed out at low power. I did some high speed taxi and couldn't reproduce it. But and even a mag check again seemed normal. I took off again just for one lap around the pattern and immediately got the roughness again. On landing I went for another Mag check, but this time held 1600 rpm while I leaned to raise the engine temp. I normalized the EDM900 display and did the mag check again. This time on the left mag numbers 2,4,6 EGT temps dropped out while 1,3,5 climbed as usual. On the right mag all EGT's climbed as expected. I would have expected all 6 cylinders to fall or the engine to actually quit with a completely failed Left mag, but three cylinders were certainly not firing. We pulled the plugs and swapped positions and did another runup. Same result. We checked the wires to those plugs and everything checked out. So finally we pulled the mag. Here are the pictures.

[mooneyflyfast]

How many hours on it?

. I had a Seneca with the TSIO 360 engines and Bendix mags.  I believed the Bendix manual which said mag overhaul interval was the same as the engine.. I wound up AOG in Gunnison, CO once with a failed oil seal in one (mag filled up with oil) and in Kechikan, AK with one internally self destructing.. Since then I have them gone through every 500 hours.

[jaylw314]

Yikes.  What was the source of the copper?  Is there any brass in a magneto, or was it just the coil?  I'm guessing if the copper oxide is green, that it has been there for a fair amount of time now, since it takes time to produce the green copper sulfate from sulfur in the air...

[EricJ]

I think I'd pop the other one open, too. 

[jackn]

Yep, I’ve seen that before. Last spring I did my 500 hr mag. The right mag was fine, the left mag was very rusty. The difference was that the left mag’s rpm pickup didn’t have a vent hole in it. I guess it originally went to the ship’s rpm gauge. The gauge was removed do to the installation of the jpi 930, but the pickup was left. Make sure to change the in-line filter to the mags. 

[bonal]

Glad you made a safe return looking at the pics that mag looks like it came off the first Mooney ever made not one as nice as yours. Think it possible to OH or is it so bad that will need replacement. Best luck to you

[gsxrpilot]

The Mags on the 252 are pressurized. And we suspect the connection between the upper deck pressure source and the Mags is set up wrong allowing moist air to be fed into the Mags causing the corrosion. We'll also be checking the filter between the upper deck and the Mags. We were just about to come up on the 500 hour inspection. I believe we'll inspect at each annual going forward.

A new Mag will be arriving today and we'll be back in the air. This one was far to far gone to overhaul.

[DXB]

Glad that worked out safely! Seems the engine monitor clearly pointed to the diagnosis the second time with the leaned out mag check on the ground.  It's a nice illustration for me of how a standard rich runup mag check on the ground has severe limitations and makes me want to go back to doing in flight mag checks leaned out every once in a while as Savvy recommends, though doing so has always made me nervous.  

I'm curious   why you got roughness after takeoff with only one bad mag -  shouldn't you get just higher EGTs and a very subtle decrement in power?  I suspect your other mag may look the same inside?   Also I imagine pulling the JPI data after the first hair-raising takeoff would have told the story without having to experience that miserable feeling again?

I'm weary of these magneto dinosaurs, though I will keep doing  500 hr IRANS until the Emag STC is done. Wish they would hurry up...

[DonMuncy]

Good job. Good diagnostic technique. Time to ship the mag to Aaron at Select Aircraft at LNC to see if it is fixable. I too, would look at the other mag.

[gsxrpilot]

The plane is with JD at SWTA right now. One of his guys spent some time at a shop where all he did was rebuild mags. He was super confident that he'd be able to rebuild it... until we opened it up. I'm sure it can be rebuilt, but it would take some time to completely clean everything and even then pretty much all the components have to be replaced. So we're just installing a new one.

We'll take a look at the other mag as well. But after talking to Slick on the phone, the left mag is often the problem on the M20K with the pressurized mags. Which is what @jackn said as well. We're optimistic the right is fine and we'll just be replacing the left.

[Bartman]

Nasty stuff there.  Looks like it was found in the junkyard but still working fine until this last flight.  Do you do the in-flight mag check at the end of each flight.  Wonder if it would have showed up ?

[MIm20c]

Wow, that looks really bad.  I’d send in the other one asap. How many years since the last 500 hr check?

[Htwjr]

Looks like that came off of a saltwater boat rather than a plane.  Glad it failed before you had to rely on it. 

[jackn]

Upon further reflection, I remember that the ship gauge pickup on the left mag did have a vent orifice, but it was covered by a fine wire mesh that over time had gotten clogged. The jpi uses a gasket style pickup that is secured under the plug. With the help of a couple of guys on this board, I was able to sort it out and replaced the original pickup with an slick orificed plug that has a little cap cover to keep out the grime. 

If you need the original pickup, suggest you soak it in solvent, blow it out. 

[Bolter]

5 hours ago, gsxrpilot said:

The Mags on the 252 are pressurized. And we suspect the connection between the upper deck pressure source and the Mags is set up wrong allowing moist air to be fed into the Mags causing the corrosion. We'll also be checking the filter between the upper deck and the Mags. We were just about to come up on the 500 hour inspection. I believe we'll inspect at each annual going forward.

A new Mag will be arriving today and we'll be back in the air. This one was far to far gone to overhaul.

You have been taking this plane to Burning Man a few times, right?  Can this be Playa dust getting forced into the pressurized mags on top of some moisture?  Picture seem to show more than simple corrosion.  That alkaline playa dust can get in there and initiate and support additional corrosion.  And it does get in everywhere.  Moisture that may normally be OK and dry out becomes a different story after mixing it up.  

-dan

[Andy95W]

49 minutes ago, Dan at FUL said:

You have been taking this plane to Burning Man a few times, right?  Can this be Playa dust getting forced into the pressurized mags 

Duuude....

Wait, what kind of dust?

[jetdriven]

6 hours ago, gsxrpilot said:

The Mags on the 252 are pressurized. And we suspect the connection between the upper deck pressure source and the Mags is set up wrong allowing moist air to be fed into the Mags causing the corrosion. We'll also be checking the filter between the upper deck and the Mags. We were just about to come up on the 500 hour inspection. I believe we'll inspect at each annual going forward.

A new Mag will be arriving today and we'll be back in the air. This one was far to far gone to overhaul.

I think the Mooney Annual Checklist  has yoy check the point gap every year

[kortopates]

My experience is the pressurized mag needs to be opened up every year; especially when operating through moisture (e.g., IMC and rain etc). The 500 hr IRAN must also be done every 5 years if not sooner and the magneto filter needs to get changed with every 500 hr inspection - if it doesn't show signs of contamination earlier. RAM's PMA's filter is better and more affordable than Continentals one too. Pressurized mags operate in a much harsher environment unlike the large footprint normally aspirated mags (like the Bendix S1200) that have been known to go to TBO without every being opened up. 

I'd be surprised if the other mag is much better looking inside. 

[flyer7324]

Aircraft Magneto Service.


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[Yetti]

Ya which boat did you pull that off

[gsxrpilot]

New left Mag installed, timed and test flown. During the test flight I took it to 4500 ft. leaned it out to 1550 TIT on 65% power and did a long, 60 sec mag check on each mag. Using the normalized display on the EDM900, the EGT's rose in perfect unison on each mag. The engine also runs very smooth on each. Satisfied that everything is working normally, I did a lean find test to see how lean it would go. Previously, with a GAMI spread of only .2 I couldn't go below 9.5 gph without roughness, today I was able to lean to 8.0 gph without any roughness. 

I'm gonna fly to North Carolina tomorrow and then back on Saturday. Over Christmas while I'm away, they'll pull the right mag and take a look at it. 

This 252 will certainly get annual IRAN on both mags going forward.

[eman1200]

....I'm gonna fly to North Carolina tomorrow and then back on Saturday...

Where in NC?

[gsxrpilot]

2 minutes ago, eman1200 said:

Where in NC?

 

KTDF - Person County, to the north of Durham.

[eman1200]

KTDF - Person County, to the north of Durham.

 

Bunch of us meeting up at GMU on Saturday which would take u a bit west of CLT but the burger is well worth it...

[gsxrpilot]

Just now, eman1200 said:

Bunch of us meeting up at GMU on Saturday which would take u a bit west of CLT but he burger is well worth it...

 

Damn! Would love to meet up with you guys, but I will be in Atlanta on Saturday.