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Pmag life

RV6-KPTW

Well Known Member
I pulled my pmag and note some play. Reading the service material led me to call Brad at EMAGAIR to see if he could quantitate “excessive” play. Makes it sound like some play is acceptable.

Now that our fleet is growing and making maintenance observations, I wonder what your experience is with the pmag? Brad notes that there are better and worse engine, prop, and ignition combos but no one does the upfront testing in experimental. We’ll have discover and report them.

For my case, I received a Thunderbolt IO390 with one Slick mag on left and one pmag ( EMAG P114L4 ), I hung the standard 72” Vans Hartzell prop (HC-C2YR-1BFP/F7497-2) and found play in the pmag at 168 hours. I am sending it off for an eval. Is the play excessive? I will report back.

Brad indicates that there are two failure modes as play increases. The generator will stop generating, and / or the unit will stop sensing where to fire. Brad said that there was nothing catastrophic that might occur. I probably should have probed further on this.

Once I receive the pmag back, I will check for play to understand the “new” condition. I am thinking I will build a fixture and use a dial indicator to check and track change over time until failure.

Brilliant or stupid?

What are your combinations and experience?

Thanks
 
... I am thinking I will build a fixture and use a dial indicator to check and track change over time until failure.

Brilliant or stupid?

What are your combinations and experience?

Thanks

Sounds like a great idea. I think capturing this information could be helpful. I think the kind of place to do this would be by someone like Savvy, where they also have other info about engine data.

Another option is a google sheet like this one:

https://docs.google.com/spreadsheets/d/13NMLUHtJwSkvVIk51klT54zFbXCL7kVzA9Bxn1kPdjE/edit?usp=sharing

Feel free to add your info, additional columns, whatever.
 
Brad said that there was nothing catastrophic that might occur.

A matter of perspective, I would say....

I am thinking I will build a fixture and use a dial indicator to check and track change over time until failure.

How would one go about doing such a thing? (Please keep in mind we have close to NO mechanical skills.)

Brilliant or stupid?

HA! Seems to me the lines are too close to differentiate!

Mike
 
Sounds like a great idea. I think capturing this information could be helpful. I think the kind of place to do this would be by someone like Savvy, where they also have other info about engine data.

Another option is a google sheet like this one:

https://docs.google.com/spreadsheets/d/13NMLUHtJwSkvVIk51klT54zFbXCL7kVzA9Bxn1kPdjE/edit?usp=sharing

Feel free to add your info, additional columns, whatever.

Should your column name change from flight hours to tach hours? That way you get consistent numbers.
 
I just pulled my P-mags at 981 hours and sent them in for new bearings. Both of them had play in the bearings. Right side was much more than the left side.

Short video of it here:
https://www.overthehills.com/RV-9A-Project/Phase-2/i-PpKMJkB

I wasn't having any ignition issues, just checking them every 100 hours at my annual inspection time.

Thanks for posting Bruce, I always wondered what the play they are talking about in the manual would look like.
 
I’m having a hard time believing that there is some noticeable amount of play in the bearing that would ever be acceptable for continued use. If it can be rattled back and forth it’s time to send it in for repair.
 
I just pulled my P-mags at 981 hours and sent them in for new bearings. Both of them had play in the bearings. Right side was much more than the left side.

Short video of it here:
https://www.overthehills.com/RV-9A-Project/Phase-2/i-PpKMJkB

I wasn't having any ignition issues, just checking them every 100 hours at my annual inspection time.

Hi Bruce, thanks for posting. I have dual pMags and 100 hrs on the engine so far, and will definitely check for play. I'd be interested in talking with you about what you include in your 100 hr condition inspection. My email is [email protected].
 
RV-7A, not an RV-14

My pMags had a bearing issue on one and an alternator phase failure on the other at virtually the same time around 85 hours.

Recently, one of them failed the "range check" on power up (this after just being IRAN'd at eMag) only when heat soaked. Worked fine when cold. This occurred at 300 hours.

Right now I'm fighting timing divergence issues, but to be fair - it is just as likely to be instrumentation/wiring issues with the EI Commander and not the pMags.

PV IO-360, Hartzell wide chord composite prop. I do believe there are installations (engine/prop combos) where the pMags are quite reliable and others where they are less so.
 
Right now I'm fighting timing divergence issues, but to be fair - it is just as likely to be instrumentation/wiring issues with the EI Commander and not the pMags.

I've had timing divergence warnings with the EIC. The engine runs just fine and without the EIC you would never know there was any divergence.
Most often when doing touch and goes where you go from idle to full throttle quickly. The red light will blink (which is disconcerting) but by the time you are up a couple hundred feet it calms down and goes away.
On most flights I've had the EIC be perfectly fine around 2 degrees, and on other flights it will be stuck around 3-4 degrees of divergence, then be right back to normal on subsequent flights. Nothing with the P-mags has changed, but for some reason the EIC will detect an issue. Sometimes having all of this information just causes needless worry. I did swap the P-mags from side to side and that didn't seem to make any difference.
 
I've had timing divergence warnings with the EIC. The engine runs just fine and without the EIC you would never know there was any divergence.
Most often when doing touch and goes where you go from idle to full throttle quickly. The red light will blink (which is disconcerting) but by the time you are up a couple hundred feet it calms down and goes away.
On most flights I've had the EIC be perfectly fine around 2 degrees, and on other flights it will be stuck around 3-4 degrees of divergence, then be right back to normal on subsequent flights. Nothing with the P-mags has changed, but for some reason the EIC will detect an issue. Sometimes having all of this information just causes needless worry. I did swap the P-mags from side to side and that didn't seem to make any difference.

Again, I have zero peroneal experience but I've been reading about the EngineBridge wifi controller/monitor and will probably install that along with the dual 6 cylinder Pmags.
 
SNIP
Nothing with the P-mags has changed, but for some reason the EIC will detect an issue. Sometimes having all of this information just causes needless worry. SNIP

I suggest for 90% of RV builders aftermarket pMag add on gizmos offer little practical value.

Set the pMag with jumper in (four cylinder) or max of 9 degrees advance (six cylinder) and fly on. Do the simple maintenance at each Condition Inspection, clean/replace plugs and fly on for another year.

Carl
 
I've had timing divergence warnings with the EIC. The engine runs just fine and without the EIC you would never know there was any divergence.

Sometimes having all of this information just causes needless worry. I did swap the P-mags from side to side and that didn't seem to make any difference.

No doubt. However, the divergence alerts can be an indicator of issues with one or both pMags. I normally see 2 degrees as well, but seeing 7 and the flashing warning screen gets your attention. Especially when the engine runs roughly at the same time.

I suggest for 90% of RV builders aftermarket pMag add on gizmos offer little practical value.

Set the pMag with jumper in (four cylinder) or max of 9 degrees advance (six cylinder) and fly on. Do the simple maintenance at each Condition Inspection, clean/replace plugs and fly on for another year.

Carl

I respectfully disagree. I think most folks with dual pMags can benefit from a monitor like the EIC. The ability to quickly change pMag settings saves a lot of time versus having to pull the cowling and hookup your laptop via a homemade serial cable. I also disagree that the stock “curve” is suitable for some installations.

Timing divergence is one indication of bearing wear, which is not terribly uncommon. Obviously, you have had better results with your pMags than I have.
 
6 Cylinder PMag Failure

I recently had some 200 series EMag failures. The mags always checked out fine on the ground before takeoff. However Leaving Big Bear California for Henderson Nevada the Lycoming 540 in my RV10 started cutting out for very brief periods of time, like .25-.5 seconds at a time. I had a very nervous passenger in the back so I decided to refrain from checking mags in flight. I called LAS approach and told them I had a rough running engine and needed to remain high through the Class B airspace to assure I could make an airport landing instead of possibly landing off airport. After thoroughly checking everything, I took it for a test flight by myself. I kept turning off one mag, then the other and could not tell any difference from running on both mags, which is actually normal for dual EMags. Finally I got one of those short interruptions again and quickly checked both mags. I was surprised that they were both still working normally. However as I kept checking mags, I discovered the right one had failed a few minutes later. It checked failed over a couple of minutes as I kept checking it looking for an intermittent problem.
The only way I could have had an ignition stoppage was to have one mag fail, and the other fail momentarily. When I got back to Henderson I removed both EMags and replaced the right with my spare EMag. On the left I installed a Bendix mag and I am running a new P-Lead. I have single throw, double pole switches for my Magnetos, (No Key) so I am using the other pole for the new P-Lead so I can leave the existing wiring as it is.
By the way I downloaded all the engine data from my Dynon EMS. I had it set for recording 4 times per second so the resolution was quite high. There was obviously no problem in my fuel system. However ignition is not monitored.
I will post again when I know more. I am quite sure of my wiring as I have checked it quite a few times and can find nothing wrong. The Mag switches always work perfectly when I checked them, so I am fairly sure something is going wrong in the EMags themselves.
 
Who is the vendor and what did they say about the problem you experienced? You say that you see no difference when running on one or both pMAGs, which seems odd to me. I always check my pMAGs during the run-up and routinely get a drop in rpm when one pMAG is turned off.
 
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