Dual P-MAG Reliability in 2017

[Bill Boyd]

Originally Posted by DanH

Ok, discard Nigel's report, and consider timing loss with a known cause, the arcing alternator B-lead.

http://www.vansairforce.com/communit...d.php?t=144336

At first, it was claimed that V40 would have prevented the issue, but that was obvious nonsense, as noted by this gentleman...

http://www.vansairforce.com/communit...0&postcount=31

...and recognized by the manufacturer:

http://www.vansairforce.com/communit...5&postcount=49

So why is it relevant to this particular exercise? The P-mag is unique, in that it's the only ignition which allows the user to insert the body and mesh the drive gear at random, then write a TDC position reference electronically. It's a wonderful feature as it relates to installation and inspection, as it makes timing a P-mag dirt simple. However, all design is the art of compromise. The same feature is an Achilles heel; the easy-to-set TDC position can also be reset. V-40 (and I suspect other patches too) is a example of an attempt to prevent unintended reset given a specific condition. The case of the arcing B-lead is an example of timing reset caused by a less predictable input, so it's not likely to be fixed with a software patch.

All other ignitions physically reference crankshaft TDC to the ignition. As such, installation requires physical alignment of trigger and crankshaft position. Losing that reference requires outright mechanical failure. It is slightly more difficult to install, but more reliable in service.

I've attempted to run though some basic "what if" analysis, which as Mike pointed out, would be followed by an estimate of probability. It does not appear we're going to be able to complete that examination due to lack of information. Frankly, it makes no personal difference to me. I'm just trying to lead the conversation back toward a logical estimation of reliability.

I will say this, based on reported field experience. The major P-mag risk is random timing reset. The major risk with other systems is simply no spark. Random timing can take out an engine. No spark merely means soldiering on with the other ignition.

The architecture which allows random timing reset due to outside factors has nothing to do with the P-mag's significant benefit, its internal power supply. A system with a hard TDC reference and internal power generation would be a heck of an ignition...but that's not what we have here.



Two things, and I'm outta here. One, it is easy to make sparks. The issue is the timing of those sparks. Two, all waste spark systems use the other plug in the paired coil as the return path for the secondary; that's why there is a wasted spark. It is very unlikely that the high voltage secondary is part of the ground path for control electronics.

(I believe they call that a magneto, Dan )

[RhinoDrvr]

Well, here's the conclusion of this thread from my end.

1.) I ended up installing two P-114 P-Mag's in my airplane. Both have v40 software and cooling fins on the case. They were wired with the existing LASAR wiring and manifold pressure lines, as well as blast tubes.

2.) I timed the P-MAG's 2 degrees after TC, so they should fire at 23 degrees at high power, and limit their advance to 32 degrees. Probably limiting the advantage I gain from them, but I like the increase in detonation margins.

3.) During test flight my performance was identical to the LASAR ignition it replaced WRT fuel flows and airspeeds. EGT's were identical, and CHT's were right around 330 degrees on an 80 degree OAT day.

4.) Cruise at 10,500' density altitude 20" / 2400 RPM (60% power) was 8.0 gph yielding around 165kts true.

5.) Idle is smoother now on the P-MAG's than it was on the LASAR, and engine starts are similar to a car. First blade and the engine fires, hot or cold. It's impressive.

6.) I am not 100% sold on the P-MAG's yet. If I have any issues with the timing, or reliability of the unit they're done and will be replaced with a different system, but for the ease of install I felt they showed the most promise at this time. Hopefully I'm not responding to this thread in a few hundred hours saying that I'm installing CPI and a Magneto...

[Flyyak]

My engine was rebuilt at JB Aircraft in Sebring FL to zero time. I am not a mechanic but I was informed that they have a great history and it has performed great to this point. I have a new constant speed Hartzell blended airfoil prop from Vans.

My engine came with two new Slick mags and harnesses which I removed after reading much about Pmags here. I removed these before installation on the RV.

I have a G3X system so I have been able to monitor the engine functions since first test flight. I had difficulty with oil temps (up to 225-230) a few times in the heat of summer in Bham Al mainly after refueling, touch and goes or during ground times after flights. Also some issues with CHT on climb if not careful. These experiences were not much different than experiences I have followed here by many others.

After I switched from AeroShell mineral break end oil, to 15-50, re-checked and modified engine baffling and changed to Stewart Warner oil cooler, oil temps OK and CHT ok but I am careful on initial climb out.

The Pmags have operated as advertised until the issues previously described. I am a little shaken at the final flight as my passenger was my wife who is a white knuckle flier.

I have certainly enjoyed and learned a ton from this building experience and from this forum. I have the pleasure of flying several different planes and I flew in the Army both RW and FW for 20 years. The RV is one of the most fun and versatile planes I have had the pleasure to fly.

All of the other planes I have flown (except turbines) have magnetos and I have never experienced a failure. The simplicity of the Pmags were a draw for me and I hope my issue was isolated and will not be repeated. I have decided to reinstall a non impulse Slick on the L mag which is the side of the bearing failure.

One of the sources of others with failures is listed in this thread. I spoke with Tim Andres and he experienced 5 different events from bearing failure to general failure of the mag just quitting operations. Both of us have 0360 A1A lycomings. Tim has a fixed pitch prop and I added FI and constant speed prop. After I questioned Brad about the cause of the failure, especially bearing failure with less than 100 hours, he stated that certain engine and prop combos may create an issue with Pmags. I hope that is not the case with my engine but I share my experience with you not as a proponent for any ignition system but as a matter of safety. The failure may be an isolated event which I hope but I will be a great deal more alert with the rebuilt Pmags.

Still running two until the Slick and harnesses arrive. Thanks for this forum. It has been an invaluable help to me during and after construction. Be glad to speak to anyone who wishes more info.

Neil Clay 205-253-9595

[Doug Eves]

I have an RV6/ io-360/hartztell cs and replaced the slicks with 2 Pmags. 57 hrs flawless. Smooth , awesome hot starts, and I think more power but not really sure. Reading this thread scares me a bit as I originally thought I should keep one mag. I was meticulous with blast tube positioning and wire routing/support but this random timing reset/engine shutdown talk is concerning. I installed and promptly flew to the east coast and all the way around Cape Breton Island at about 200' inspecting the coastline and whale watching. (with a passenger) Probably shouldn't admit that on here but I'd hate to see the fan stop. It's what keeps the pilot cool.

[N941WR]

Originally Posted by erich weaver

What is the source of this information?

Thanks,
Erich

We have had two customers who have picked up bearing failures with the EICommander, before they became more than just a maintenance an issue.

One was an early 113 P-mag on an O-320 and the other on a FP O-360.

Statistically, probably a rounding error.

They show up as a timing divergence issue on the EIC and are a challenge to debug. After we go through all the "usual" questions, we ask the clients to remove and inspect the P-mags. Sure enough, they found some wiggle in the shaft.

As a control point, I have 800 hours on my P-mags, 200 hours in a low compressions O-290-D2 and 600 hours on my O-360 180HP (ECi Equivalent) and have not had an issue with the bearings. However, I did have the internal generator grenade right at 500.? hours. These were the P-mags I had in the plane when I had prop strike with the O-290-D2, so it is possible that this failure is related to that. It is also one reason I always perform a mag check by pulling ship's power from them prior to every flight. The ignitions never missed a beat and had I not checked the internal generator, I would never have known there was an issue. The good news is, they operated off of ship's power just fine and I completed my flight home as it was firing and the other P-mag's internal generator was functioning fine.

[Doug Eves]

What i am curious about is what would cause the bearing to wear out or fail? The only thing I can think of is a side loading caused by improper gear clearance or something out of balance on the end of the shaft. As an example, when I had my slicks rebuilt the impulse mag was sloppy and looked in terrible shape but the non impulse one was in good shape. The mechanic said it was due to the big chunk of unbalanced iron spinning around inducing loads on the shaft. It made sense to me but P mags don't have that issue.

[gasman]

Originally Posted by Doug Eves

What i am curious about is what would cause the bearing to wear out or fail? The only thing I can think of is a side loading caused by improper gear clearance or something out of balance on the end of the shaft. As an example, when I had my slicks rebuilt the impulse mag was sloppy and looked in terrible shape but the non impulse one was in good shape. The mechanic said it was due to the big chunk of unbalanced iron spinning around inducing loads on the shaft. It made sense to me but P mags don't have that issue.

Doug, what I am curious about is what happened to XD3 15w40?

Thanks up front for your response....... now back to P mags.

[moosepileit]

Mid 1990s. A big mfgr made a 2 blade composite prototype prop and I believe a friend had the first if not only on a pumped up 4 Cyl Pitts S1T, angle valve, 9:1 or greater compression.

It repeated interacted vibrations to the Slick mags that caused failures of the mags. I believe twice in under 50 hours.

I assume this interaction is still a challenge.

[N941WR]

Originally Posted by moosepileit

Mid 1990s. A big mfgr made a 2 blade composite prototype prop and I believe a friend had the first if not only on a pumped up 4 Cyl Pitts S1T, angle valve, 9:1 or greater compression.

It repeated interacted vibrations to the Slick mags that caused failures of the mags. I believe twice in under 50 hours.

I assume this interaction is still a challenge.

I had a friend with a Continental O-200D and ground adjustable Sensenich composite prop on the front of his Cub Crafter's Cub. His Slicks would be lucky to make 35 hours. He switched to a Catto prop and the problem went away.

It is all about harmonics.

[Doug Eves]

Hello gasman. I made a couple follow up comments on the 15w40 on the the"any P-mag pireps?" thread. See the last comment on page 6 and the 1st comment on page 7 over there. Basically a few of us around my parts use this oil. I worked in R&D at Imperial oil for the first 7 years of my 37 year there. We had a large engine test facility which I spent lots of time frequenting as one of my close friends tore down and prepare engines everyday for testing. Also have seen high time lycomings taken apart that used conventional av oil vs XD3 15w40. Lets just say I am VFR orientated. Seeing is believing.