Noah
Well Known Member
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.
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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