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  #1  
Old 06-26-2013, 07:32 PM
Noah's Avatar
Noah Noah is offline
 
Join Date: Jun 2007
Location: Rhode Island
Posts: 955
Default My P-Mag Failure

My P-Mag, purchased in Oct 2011 with about 200 hrs on it, failed earlier this month when I was a few hundred miles from home.

After giving a couple of rides and loading all of my gear to head for home, I restarted the engine and had no RPM indication, ummm, Uh-oh! (RPM signal originates from the P-mag in my installation). An ignition check showed the P-Mag to be No-Op. After several engine restarts and reattempted ignition checks and wiring checks, I attempted to call Emagair Ignitions, but it being a Saturday afternoon, I couldn't get anybody and so left an urgent AOG message. I verified power and ground at the P-Mag which were fine, and because I didn't have a lot of time, removed the P-Mag, tied the plane down (couldn't find any hangar space and didn't have my travel cover with me) and borrowed a friend's truck and started out on the 5+ hour drive home.

Everything looked fine externally, note the 2 temp-tab labels I installed when new, which have much better resolution than the single factory "200F exceeded" button.









On the drive home, I got a call from Brad just as I was getting pulled over for speeding (bummer, there are no Staties pulling you over at 7500 MSL). I called Brad back and gave him the scoop. He offered to send me a loaner but that didn't make sense because I was not going to be able to get back up to install it until the following Friday. So I overnighted the unit back to Emagair who thankfully turned it around to me within 4 hours. They only charged me for shipping despite the unit being out of warranty for 7 months or so, so that was nice.

Unfortunately, they were not able to replicate the no-op condition, and could not tell me definitively why my unit failed. He didn't think it was heat related, and was pretty sure it was due to "excessive axial free play". He thought that the shaft felt loose, so he replaced the mechanical components. He said there is a sensor that senses shaft axial (magnet) position, and if the sensor indicated that shaft was not in the correct axial position, the unit would not start up, in fact it would not even boot, so no RPM signal would be generated. In this condition, the LED will flash yellow, indicating a shaft range violation. A steady yellow LED is indicative of a shaft axial range violation during the previous flight cycle. This is an “attempt to signal the violation” to the operator. (Unfortunately this is not documented in any version of the installation and operating guide, so I was not aware of it when my unit failed, and was not able to check for this). Brad said that this failure was “far earlier than I would expect” at only ~200 tach hours. Subsequent to this, I learned about a P-Mag troubleshooting guide on their website which does explain a bit about the mystery yellow LED.

After another 5+ hour drive up to Maine, I reinstalled the unit which was uneventful, and everything worked fine on the flight home. But now I had little confidence that, not knowing why this failed, it would not happen again. This failure cost me over $500 in gas, shipping fees, and of course that speeding ticket.

So
I had another long conversation with Brad, and he informed me that for some time, they have had this safety feature where the P-Mag magnet position sensor will look for a shaft axial out of range/tolerance condition. If it occurs during flight, the unit will continue to operate, and will attempt to signal the operator with a yellow LED after the flight. You have to know to look for this. If this shaft is out of position (axial position) at startup, the unit will simply not work at all, it will not even load its own software and will not boot. I asked Brad why these LED codes are not in the manual and he agreed that they should be. The following post in this thread is a DRAFT version of what is going to be added to the manual explaining these LED codes that I got from Brad today.

Here's the thing. They shipped a bunch of these units without knowing where in the "window" these magnets were. If you got a unit with the magnet in the middle of the window, you're probably fine. If you got a unit with the magnet at the edge of the window, probably like me, it would not take much wear for the magnet to get "outside the window" of acceptable axial position and then the unit will fail to operate at startup. Again, if this out of tolerance condition is sensed during operation, it will continue to operate as it should. It will only go no-op at startup, never in flight, which is a very good thing, it is designed as it should be.

After Emagair started seeing failures like this, they started controlling the axial location of the magnet on the shaft much more closely with a fixture, to ensure that the magnet is in the middle of the tolerance window at assembly, and minimizing the possibility that the unit will no-op due to an axial shaft out of position error at startup. My unit was repaired with this new assembly technique, so I have confidence that we have a likely understanding of my failure mode, and good reason to believe that it will not reoccur, at least for a long time, hopefully. The bottom line is that P-Mag owners should be checking their LEDs postflight, looking for a solid yellow LED, PRIOR TO POWER OFF to see if their shaft is out of tolerance.
Maybe this will save you a bunch of headache and some cash too.

I would like to thank Brad at Emagair for his stellar customer service. What I experienced, while being a pain and an unexpected expense, in no way jeopardized flight safety. This unit shut down and PREVENTED me from flying with a unit that was marginal due to its own Built-In-Test (BIT) functionality. BIT tests are a hallmark of robust product design and indicative of professional hardware and software development. The development of any new product will always yield a surprise or two and I have every confidence that these guys are continuing their development and doing the right things to make these units more and more reliable. I will continue to fly behind this unit with confidence.
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous men, for they may act their dream with open eyes, to make it possible. -T.E. Lawrence

Last edited by Noah : 06-26-2013 at 07:38 PM. Reason: Spacing
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  #2  
Old 06-26-2013, 07:32 PM
Noah's Avatar
Noah Noah is offline
 
Join Date: Jun 2007
Location: Rhode Island
Posts: 955
Default From Emagair, Draft LED Codes for Operator's Manual

Additional LED Signaling: (applies to all 114 series and most 113 series programs)

Beyond the RED and GREEN LED signals described in the manual for setting timing, other LED signals are as follows:

1. Sensor Magnet Range Check - Every time the ignition powers up, the ignition first performs a self-test to verify the sensor magnet is within an acceptable range. If the Range Check passes, the ignition proceeds with program load (no LED signal). If the Range Check fails, it will proceed no further and will signal the condition with a pulsing (approx 1 every half sec) YELLOW LED. From the operators perspective it will appear as a non-operative ignition. The flashing YELLOW will continue until the condition clears or the unit is powered OFF. No record of the violation remains after power OFF.

2. Successful Program Load – Next, the ignition will signal a successful program load with an LED color burst. The color burst will occur immediately after power up and will appear as a quick pulse of RED and a quick pulse of GREEN – any overlap of the two may appear as YELLOW. At this point the ignition is active and ready for service.

3. If the p-lead was grounded PRIOR to power up and REMAINS grounded, the ignition will light the LED steady RED or steady GREEN (after the step 2 color burst). The color will depend on engine position relative to the ignition index. If the p-lead was not grounded, the LED will go dark after the color burst. Setting timing and the rules for setup mode are discussed in more detail in the manual.

4. Should the ignition later detect a Range Check violation after a successful program load, it will NOT interrupt ignition operation. It will continue to fire plugs and perform all operational tasks. But it will signal the violation by lighting the LED steady YELLOW (no pulsing). The yellow signal will remain until the condition clears or the ignition is powered off. No record of the violation remains after power OFF. The next time the ignition is powered up the process starts over again with step 1.
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous men, for they may act their dream with open eyes, to make it possible. -T.E. Lawrence

Last edited by Noah : 06-26-2013 at 07:36 PM.
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  #3  
Old 06-26-2013, 07:45 PM
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tkatc tkatc is offline
 
Join Date: Nov 2007
Location: NJ
Posts: 1,747
Default

I agree the service is great at EmagAir...though I wished I'd never had to use it. Where did you get those thermal stickers? Perhaps EmagAir should be using those instead. Much more accurate.
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  #4  
Old 06-26-2013, 07:51 PM
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Noah Noah is offline
 
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Location: Rhode Island
Posts: 955
Default McMaster has a nice selection!

http://www.mcmaster.com/#temperature...labels/=nd89c0
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous men, for they may act their dream with open eyes, to make it possible. -T.E. Lawrence
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  #5  
Old 06-26-2013, 08:20 PM
Kyle Boatright Kyle Boatright is offline
 
Join Date: Aug 2005
Location: Atlanta, GA
Posts: 5,146
Default

This is exactly the kind of problem I fear most with our relatively low volume experimental electronic ignitions. With a magneto, there are very few points of failure, and mag troubleshooting and repair help is available at a lot of airports - not so much with an experimental ignition.

When my Electroair ignition failed about a year go, I spent a month chasing the problem, and never did figure out exactly what had failed, despite having the unit bench tested by both Electrair and Jeff Rose. Extremely frustrating. Ultimately, I replaced the unit with a P-mag, simply because I still wanted an electronic ignition, but wanted one that would be easy to install. Next time, I may throw another Slick on there, because the AOG risk I perceive with electronic ignitions really concerns me...
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  #6  
Old 06-26-2013, 09:11 PM
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Noah Noah is offline
 
Join Date: Jun 2007
Location: Rhode Island
Posts: 955
Default

Quote:
Originally Posted by Kyle Boatright View Post
This is exactly the kind of problem I fear most with our relatively low volume experimental electronic ignitions. With a magneto, there are very few points of failure, and mag troubleshooting and repair help is available at a lot of airports - not so much with an experimental ignition.
I hear you Kyle, and believe me I thought a lot about this during my 10+ hours of driving due to this failure!

One solution I thought of was a "P-Mag Spare Club" (needs a better name) where 15 guys would buy a spare P-Mag for $100 each and keep it in a box, ready to go, in somebody's hangar in a central location where it could be flown out to somebody with an AOG condition in short order.
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Highest Regards,

Noah F, RV-7A

All men dream, but not equally. Those who dream by night in the dusty recesses of their minds wake in the day to find that it was vanity: but the dreamers of the day are dangerous men, for they may act their dream with open eyes, to make it possible. -T.E. Lawrence
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  #7  
Old 06-26-2013, 09:40 PM
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tkatc tkatc is offline
 
Join Date: Nov 2007
Location: NJ
Posts: 1,747
Default

I figure I save just over 1 gallon per hour using the P-Mags and also some cash when it comes to plugs. If you set up your engine to realize the savings as mine was by the builder....the break even point is 250 hours if you calculate a gallon at $6. If you can achieve 500 problem free hours then the P-mags were essentially free. Everything beyond that is gravy.

In your case Noah, it seems as though your P-Mag savings acct has just been reset to zero. I'm probably in the same boat since I had to pay $450 for a new board when mine failed.

I don't believe P-Mags are a safety issue but rather a time/expense issue. Despite the trouble reported, I will install dual P-Mags on the -8 when the time comes.
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Track my RV7A!!

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Building an -8! (Fuse)
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  #8  
Old 06-26-2013, 09:44 PM
Kyle Boatright Kyle Boatright is offline
 
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Location: Atlanta, GA
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Quote:
Originally Posted by Noah View Post
I hear you Kyle, and believe me I thought a lot about this during my 10+ hours of driving due to this failure!

One solution I thought of was a "P-Mag Spare Club" (needs a better name) where 15 guys would buy a spare P-Mag for $100 each and keep it in a box, ready to go, in somebody's hangar in a central location where it could be flown out to somebody with an AOG condition in short order.
I've thought of buying a timed out, but serviceable Slick, to lug along on trips. Attach it to the top of the battery box and it would have a negligible impact on w/b or useful load...
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2001 RV-6 N46KB
2019? (actually 2022) RV-10 N46BX
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  #9  
Old 06-26-2013, 09:49 PM
Bob'sRV6A Bob'sRV6A is offline
 
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Location: Arroyo Grande, CA
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Default

I wonder if the EI Commander would give any indication of the sensor magnet out of range fault?
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  #10  
Old 06-26-2013, 09:58 PM
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miyu1975 miyu1975 is offline
 
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Location: Indianapolis, IN
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Default

To bad the LED light can't be put on the panel.

Who is going to actually pull the cowl every flight and check for a yellow light?..I wouldn't expect that to happen I guess unless you were not able to start the engine. Maybe Brad could add a signal wire off the pmag that can attach to an LED on the panel...
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