Given their inability to design it correctly the first time, I have little confidence they designed it correctly the second time. Time will tell but my $ is on this not going away. Requiring a 500 hr check seems to presume the same lack of confidence from the designers. I suspect this wasn't a big deal when Brad would see a failed bearing at 200 hrs and provide a quick and affordable fix. Now at $900 or $1400 a pop, this is going to be painfull for some.
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P-Mag Service Life
- Thread starter N925JL
- Start date
Just poor engineering. The bearings in mags are a very low failure item. Can go 1000's of hours. bearing design principles are pretty basic and haven't chaged much in decades. My guess is they tried too hard to keep the package size small and under sized them or didn't bother to run their design past an engineer, which is odd, as a company like NTN offers up many design guides and has engineers on staff to help. I got a couple ideas from them when I designed my mag hole crank position sensor assembly. At the time, I didn't know that I needed a wave washer to keep some light axial load on the bearing outer shell to be sure that the bearing was not spinning in the housing, as there was very little radial load on the shaft; a lesson PP likely never learned on their alternators that wallow out the housing bores. Also many guidelines on which bearing is interference and which is slip fit.
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Toobuilder
Well Known Member
I would like to give them the benefit of the doubt, but the lack of chatter on the boards concerning the root cause compelled me to ask directly. This product has been out there for decades. There should be tons of data and CERTAINLY enough time to perform a formal engineering RCCA. People are apparently happy there is a redesign of the bearing stack and that’s good that it’s an acknowledgement that there is a problem, but is the cause known? To your point, if this fix is just “…a few more nails and that’l hold her…” solution, there’s a good chance we are just kicking the can down the road. Or worse, it drives the failure into something more catastrophic.
And even though they extended the bearing inspection time to 500 hrs, I suspect there is very little actual data to support that time extension.
FORANE
Well Known Member
I've read multiple reports of bearing failure with E-mags. Unfortunately there seems to be little breakdown of those reported failures by new vs old bearing. Is it safe to presume most of the bearing issues are on E-mags with the old bearing?
Clearly the E-mag has some compelling advantages. The price increases while disappointing aren't unexpected. Will it drive people away from the product? Will an alternate service provider emerge for E-mags in the field?
SDS ignition has been mentioned in this thread. Clearly it has some advantages compared to E-mags. It has some disadvantages also. While I don't know anyone who has suffered an E-mag failure, I personally know someone who ended up landing on a road after electrical failure running a SDS ignition.
Clearly the E-mag has some compelling advantages. The price increases while disappointing aren't unexpected. Will it drive people away from the product? Will an alternate service provider emerge for E-mags in the field?
SDS ignition has been mentioned in this thread. Clearly it has some advantages compared to E-mags. It has some disadvantages also. While I don't know anyone who has suffered an E-mag failure, I personally know someone who ended up landing on a road after electrical failure running a SDS ignition.
That was due to an electrical system issue if I recall, not a failure of the SDS.
An electrically dependent aircraft is a whole new game which is why I prefer a std mag alongside an EI.
Here is a rare occasion that I agree with Walt. An electrically dependent engine requires a “whole system” approach to design.
My experience with such setups is the builder tends to copy someone else’s power distribution design - and not much more. I’ve seen an RV with two alternators and five or so various backup batteries land with a dark panel. Luckily he was using standard mags so the fan did not stop.
The point, backup power is great for avioinics and such SDS installs IF the backup power is reliable (tested) with more than one back mode, and the power gets to where it needs to go. The second part of this is the Achilles Heel. How many setups depend on a single switch not failing, or for that matter something as simple as a ground wire not falling off?
I designed a power distribution system for a ship power dependent EI setup, but ripped that out ~22 years ago after repeated problems. I replaced this EI with dual pMags and continue to use them on all the builds. I retained the power distribution design as it meets my design criteria for IFR flight.
The point, mitigate the risks. Walt’s approach is a viable solution for most people.
Carl
Not a lot of words, but a lot of wisdom here. Very little functional benefit to a second EI. The more reliable systems may have a cost advantage (lesser ones not so much), but these need to be weighed against the SIGNIFICANT benefit of a 2nd ign source that is dependant upon basically nothing, not even a grd wire; And they rarely out right fail. They usually show synptoms before total failure. Not universal, but typical.
I have only one EI on my 6 and very happy. On the 10, I chose two only because the mags were run out and I did not like what I heard about all of the issues with the bearing setup on the 540; Decided it was a lesser risk.
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Toobuilder
Well Known Member
“Old vs. new” is largely irrelevant in this context. Ball bearing technology and the engineering behind proper selection are not new. WHAT is causing ANY bearing to fail in a Pmag is what we need to be asking. Was is poor supplier quality or is it some undiagnosed resonant condition within the product itself? Why do Pmag bearing fail when magneto and alternator bearings don’t?
what is being completely ignored in all of the discussions is that saying “P-Mag” is no longer sufficient becasue there are four-cylinder units with twenty years of development, field experience, and upgrades…and six-cylinder units that are a ground-up design (mechanically) that have only a few years of field experience. Not differentiating between the two is like saying “Ford” without specifying a Mustang or an F350.
Regardless of whether you love, like, hate, or despise P-Mags, any discussion that ignores the basic differences is by its very nature not engineering-oriented and simply becomes anecdotal. That doesn’t help either customers or the developer.
Folks have had failures with P-Mags (both form-factors), there is no doubt about that. People have also flown them for thousands of hours with no failures at all. A forum like this gives you absolutely zero statistical information on reliability because people don’t report their successful flights - they just keep flying.
And let’s not forget that we have also seen many threads and posts over the years on off-airport landings, engine failures, precautionary landaings, and people stranded no matter WHICH ignition choice they have - Slicks, Bendix, Lightspeeds, SDS, EFII, and all the rest. I personally am not comfortable in assuming 100% reliability of the ship’s electrical system either, which is wby I choose self-contained ignition systems. There are simply way too many recorded mishaps of loss of all electrical in experimental aircraft to assume that the power system is going always stay functional.
Paul
Regardless of whether you love, like, hate, or despise P-Mags, any discussion that ignores the basic differences is by its very nature not engineering-oriented and simply becomes anecdotal. That doesn’t help either customers or the developer.
Folks have had failures with P-Mags (both form-factors), there is no doubt about that. People have also flown them for thousands of hours with no failures at all. A forum like this gives you absolutely zero statistical information on reliability because people don’t report their successful flights - they just keep flying.
And let’s not forget that we have also seen many threads and posts over the years on off-airport landings, engine failures, precautionary landaings, and people stranded no matter WHICH ignition choice they have - Slicks, Bendix, Lightspeeds, SDS, EFII, and all the rest. I personally am not comfortable in assuming 100% reliability of the ship’s electrical system either, which is wby I choose self-contained ignition systems. There are simply way too many recorded mishaps of loss of all electrical in experimental aircraft to assume that the power system is going always stay functional.
Paul
Toobuilder
Well Known Member
Don’t “love” or “hate” the product. From an engineering perspective, just wondering what the hell is going on with these things? How hard can it be to have a mechanism spinning on the accessory case without destroying itself in 100 hours? Many of us on this forum have formal flight test backgrounds, and you know that the bearing failure would never survive a formal RCCA.
If the failures are 100% induced by user error, fine. Tell us. If it’s a random poltergeist floating around the Emagair factory, fine. Tell us. But they don’t. That’s troubling to me. Especially when “ignition reliability” has been pushed so far down the list of things to worry about that it’s not even on the radar of any other form of internal combustion engine on the planet. The electrical problem of “ignition” has been solved for decades…. The mechanical side has been solved for even longer. What is going on with Emagair that they can’t figure this out?
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N10KE
Well Known Member
Assuming you haven't had to pull it prior to 500 hours for a board or bearing failure - which then would require a $1400 overhaul.
Exactly. In automotive, the rate of significant ignition malady unrelated to age or abuse is approaching zero. For sure I've never seen a failed bearing in any kind of rotating ignition component, nor does anyone in the auto trade use low temperature electronics or POS wire connectors.
My Chevy (coil-near-plug 5.3) is at 4500 hours and 180K with no ignition maintenance at all. It's the current norm.
Nicely describes the problem. Twenty years of development, in the field, with customers, is a viable business plan only if the vendor does a great job of supporting inexpensive repairs, and then only in a niche market. Brad and his crew were excellent, so the product survived.
In the automotive market, twenty years of development without fixing fundamental issues is a Trabant.
But of course a great many East Europeans got good service from them.
I wouldn’t consider myself a P-Mag fanboy either, but I think those are two separate issues. A failure that requires repair or overhaul at some point isn’t necessarily the same as saying the P-Mag has a mandatory overhaul requirement every 500 hours. Also, unless I’m mistaken, the current replacement price is closer to $899.
