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-   -   Dual P-MAG Reliability in 2017 (https://vansairforce.net/community/showthread.php?t=154003)

rv6ejguy 10-10-2017 04:09 PM

Quote:

Originally Posted by Malndi (Post 1210064)
I'm on the fence and watching the debate, however the risk of the crank sensor and wires being damaged by alternator belt failure is a key concern for me. Particularly given that I wasn't far from that crash and know the occupant who was very badly burnt. Would like to know more about how the crank sensor and cables can be protected, but didn't find the answer on your website. Can you elaborate here.

I've posted photos in other threads on this topic. Our crank sensors and mounts are far more robust than the early LS ones- you can lift the engine up from ours. The mounts also incorporate several threaded holes to attach cable armor to. A number of people posted their solutions here: http://www.vansairforce.com/communit...d.php?t=152923

The last post here shows a photo of the mount and armor mounting holes: http://www.vansairforce.com/communit...d.php?t=143608 Go to Page 5, post #44 last page.

I should mention that the early LS crank sensor setup has been superseded by a new design which has the cabling mostly inside the baffle sheet metal.

KRviator 10-10-2017 04:38 PM

And another few examples using "Distributor" as the faulty part:
Quote:

13 March 2014: Magneto distributor block cracked. Suspect due to over torquing of attachment. Investigation also found timing out of limits.

13 November 2013: Maneto distributor block bush worn allowing timng gear teeth to slip and put the timing approximately 180 degrees out. See attachments for photographs.

02 November 2013: LH magneto distributor block failed allowing magneto to retard sufficiently for engine to stop.

23 September 2013: Gear bearing in distributor block was found loose following an uncommanded engine stop on takeoff. Installation of a new distributor block and gear corrected the fault.

08 July 2013: LH magneto distributor block bushing loose causing gears to demesh.

19 June 2013: Magneto distributor block bushing loose resulting in timing problems

17 September 2012: LH magneto distributor block loose allowing distributor gear to jump teeth. Suspect bushing incorrectly installed at manufacture. See attachment for photograph.

02 March 2010: Magneto distributor block bearing dislodged causing misalignment of the distributor gear and affecting engine timing. See attachment for photograph.

23 July 2007: LH and RH magneto points defective. Points out of adjustment and timing moved.
Granted, not all of these instances resulted in engine failures or rough running, however, the SDR's indicate the potential for such problems, should the issue not have been found and corrected.

spatsch 10-10-2017 05:50 PM

Quote:

Originally Posted by KRviator (Post 1210050)
....
American pilot would expect to experience such a phenomenon and be expected to react accordingly. Commentary here suggests this may not be the case, and if this is indeed true, I would encourage a mag-check to be incorporated as part of your IA's following engine roughness or failure and be practiced as such, at the earliest opportunity. As I said earlier, it was part of the spam-can checklists I was trained under and that is going back close to 20 years, and it is there for a reason.

This certainly affects US pilots too. Here just one NTSB report with two fatalities:

https://www.aopa.org/asf//ntsb/narra...20050815X01247

This is also thought as part of the emergency checklist at least by my flight instructor and AOPA points it out too:

https://www.aopa.org/news-and-media/...-magneto-check

So not just a problem on the other side of the world.... .

Oliver

N941WR 10-10-2017 07:56 PM

Quote:

Originally Posted by Toobuilder (Post 1210014)
Please define an "automotive ignition" so that we have context. Are you discussing something from the 1960's or today? In the 60's you had a true stand alone system: Distributor, amplifier, coil... Today, with the ECU handling many functions, receiving signals from many sensors, its hard to segregate an "ignition system". You can certainly buy aftermarket coils and fat spark plug wires just like in the old days, but a "system"? Please define.

Current ODBII ignitions is what I'm talking about Mike.

Quote:

Originally Posted by Toobuilder (Post 1210014)
Please cite actual failure rates "caused" by the use of "Multi component systems". Not what "could" happen, but what actual experience shows "does" happen.

You can use the search function as well as I can.

Quote:

Originally Posted by Toobuilder (Post 1210014)
Compare that to the engineering challenge of cramming all that stuff into one box to satisfy a marketing niche and see where that gets you? Would you like to compare the history of "magnet misalignment " with Ross' product line? How about "lost timing events"?

Show me one failure that has resulted from "Cramming all that stuff into one box" when properly installed.

Quote:

Originally Posted by Toobuilder (Post 1210014)
I'll grant P-mag the benefit of the doubt that their issues are largely resolved (with frequent, repetitive inspections), but we all know that that has been a long, uphill battle - a battle LARGELY the result of the marketing decision to package it all together - But there is no way you can pound the drum that a "distributed" system is inherently less reliable. No way. To do so flies in the face of logic and absolutely overwhelming evidence to the contrary.

More connectors mean more places for vibration to work on.

Yes, the P-mags had some teething problems, most, if not all, of which are behind us. With thousands in use around the world, they are a proven ignition.

Quote:

Originally Posted by Toobuilder (Post 1210014)
It's time to put that bogey man to rest.

I agree!

N941WR 10-10-2017 08:05 PM

Quote:

Originally Posted by KRviator (Post 1210050)
No problems, Google "Magneto losing timing lycoming" and it is the 2nd from the bottom. ...

Last year I spoke with an FAA representative regarding certifying new ignitions.

I asked the gentleman if it would be possible to certify a traditional magneto today. His response was that there is no way to certify a magneto to today's reliability standards.

rv6ejguy 10-10-2017 09:35 PM

Quote:

Originally Posted by N941WR (Post 1210135)

Yes, the P-mags had some teething problems, most, if not all, of which are behind us. With thousands in use around the world, they are a proven ignition.


Yet, are the only ignition systems for aircraft out there with a 100 hour manufacturer recommended inspection interval. Doesn't seem to be a lot of confidence in what they've done. No change in the last 5 years as far as I'm aware. Why haven't they extended the inspection interval if they are so reliable? Not even close to a standard mag.

Captain Avgas 10-10-2017 10:08 PM

Quote:

Originally Posted by KRviator (Post 1210050)
As you can see, PMags are not alone in the lost-timing issue and I dislike the fact that at least two qualified pilots do not understand basic magneto operation enough to understand they too suffer from timing issues - and they can be a relatively common occurrence too - that can affect engine operation, instead trying to point the finger at PMag as being the only possible culprit in this regard.

The specific cases you have raised are typically magneto timing "adjustment problems" of 4-5 degrees. Of course everyone knows that Magneto timing can drift with component wear. That's why we check magneto timing at every annual and recondition them (hopefully) at 500 hours. But the 500-hour major maintenance is frequently neglected, and it's not unusual to see an engine reach TBO without the mags ever having been removed. The fact that mags can continue to function in the face of such neglect is a testament to their inherent reliability.

What we're talking about with PMAGs is something completely different. We're talking about a condition where the timing can advance suddenly and without any warning to such an extreme degree that it causes the engine to quit (or suffer damage).

We need to see this issue in perspective. I'm guessing that there might be at least 400,000 conventional magnetos in service today in GA just in the United States. And yet engine failure caused by a properly maintained magneto suddenly (and without any warning) becoming wildly advanced is virtually unheard of.

Now compare that to the PMAG of which there may be no more than a few thousand in service and yet with a well known history of incidents related directly to extreme timing loss.

Maybe the PMAG is now beyond its loss-of-timing issues. I certainly hope so. I see that many PMAG owners claim that V40 has solved the problem. But I've heard that claim before many times over the last 10 years. It also puzzles me as to why, if V40 is the ultimate solution to the timing problem, it is not a mandatory revision. I'm not sure what that says.

Toobuilder 10-10-2017 10:23 PM

Quote:

Originally Posted by N941WR (Post 1210135)
?..Show me one failure that has resulted from "Cramming all that stuff into one box" when properly installed...

Seriously? Did you just in one fell swoop blame every documented P-mag failure on improper installation? This is the same product thar prides itself on "ease" of installation, right?

You're a smart guy. You have developed and brought to market your own product. Though we understand your product owes its very existence to the shortcomings of the P-mag ignition, I'm not about to believe that you actually think the engineering required to accurately and reliably time a spark event is difficult. Hall effect sensors have been around a very long time. They are proven to be stone axe reliable - and hanging them on the crank and block/case has been used reliably for millions and millions of hours in rain, dirt, chemicals, heat and vibration without fail. So why then did P-mag have such issues with their own application when the rest of the motorsports world does not? It's because they took the "hard way" to force a non optimal engineering solution in exchange for favor in the market as an "easy to install" option. To their credit, many have bought in to this concept (including me) and their outstanding (in my experience) customer service has kept them around long enough to gain market share. Good for them, but that's of little consequence to those who have not realized the dream of trouble free ignition performance.


Quote:

More connectors mean more places for vibration to work on.
Ok, but Ice Cream has no bones

Both are meaningless statements.

The real answer is a connector either meets requirements of the operating environment, or it does not. And it is abundantly clear that the weatherproof, locking, strain relieved connectors common in the current automotive world are more than up to the the task. Billions of hours of use illustrate this in spades. You can not invent a problem that has already been solved. Try again.

...Besides, do you really want to bring up connectors in light of the cheeseball stuff P-mag uses?

Canadian_JOY 10-10-2017 10:45 PM

Quote:

Originally Posted by Toobuilder (Post 1210176)
...Besides, do you really want to bring up connectors in light of the cheeseball stuff P-mag uses?

This one point is what kept me on the fence for a long time, wanting a P-Mag for its advances over a Slick, and not wanting a P-Mag because the designers made a terrible choice in electrical connectors. Eventually the desire to save fuel won out.

Had Ross's CPI not had such an ugly green control box I likely would have gone with CPI as my ignition of choice, but there was no way I was going to have a green monster in my cockpit! :p

When it comes time for our impulse-coupled Slick to be replaced, Ross's CPI-2 might well get the nod. I've got a spot where I can mount the controller on a mechanism which would allow it to be stowed most of the time and swung out into view only those times when its needed. And I've got an essential bus with its own battery so who knows when a CPI might make its way into our airplane.

KRviator 10-10-2017 11:40 PM

Quote:

Originally Posted by Captain Avgas (Post 1210174)
The specific cases you have raised are typically magneto timing "adjustment problems" of 4-5 degrees.

Most true, but certainly not all, and certainly not 'only 4-5*'. 1 in July 2013, 1 in September 2013, two in November 2013, with engine failures. Several close by in 2014 losing timing 'within a few hours of flight' - not just over the course of their annual or 500-hourly inspections...

Quote:

What we're talking about with PMAGs is something completely different. We're talking about a condition where the timing can advance suddenly and without any warning to such an extreme degree that it causes the engine to quit (or suffer damage).
See above. EFATO due timing changes can, and has been repeatedly caused by timing drift of magnetos.

Quote:

We need to see this issue in perspective. I'm guessing that there might be at least 400,000 conventional magnetos in service today in GA just in the United States. And yet engine failure caused by a properly maintained magneto suddenly (and without any warning) becoming wildly advanced is virtually unheard of.
So why are they being reported in Australia, but it is 'virtually unheard of' in the US? Much as CAsA and ASA would like to think so, aviation down here is not that different to anywhere else.

Quote:

Now compare that to the PMAG of which there may be no more than a few thousand in service and yet with a well known history of incidents related directly to extreme timing loss.

Maybe the PMAG is now beyond its loss-of-timing issues. I certainly hope so. I see that many PMAG owners claim that V40 has solved the problem. But I've heard that claim before many times over the last 10 years. It also puzzles me as to why, if V40 is the ultimate solution to the timing problem, it is not a mandatory revision. I'm not sure what that says.
How many instances of timing loss occured after V40? That is the question and the answer is sadly lacking data. Emagair may know for sure, but AIUI, there have not been any engine failures relating to timing divergence since V40 was released. As to why it is not mandatory? Who''s to say?


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