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P-Mag out annunciation

Webb

Webb

Well Known Member
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If a P-Mag were to quit in flight, can an annunciation light come of for the mag that quit working?
 
E-Mag doesn't have a discrete alarm output, but you can monitor the system with the EI Commander and that should tell you when things go awry.

Or you can do a mag check if you suspect something is wrong.
 
Mag fail annunciation

Yes, the E-mag has rpm output which can be connected to GEA24 connector J243 pin 6 and 8. The GEA can read rpm from both E-mags simultaneously.
You can set an alarm level for low rpm in G3Xt.

Good luck
 
Desert Rat said:
Maybe I'm just not understanding this correctly, but how does a low rpm equate with a failed mag?
Click to expand...

In the case of a mag, the RPM indication would go to 0 if it stopped sparking for most, but not all, reasons (the instrument senses the voltage collapse in the coils primary winding, twice per revolution). A Pmag is not that simple. If the CPU failed, RPM would go to 0, but there are many other types of failures that will prevent a spark and not result in a 0 RPM reading, such as a failed coil.

If you pay attention to your engine instruments, it should be pretty obvious when going from 2 ignition sources to 1. Power will drop 5-10% for any given fuel flow and EGTs will rise around 150 degrees from where they were with both ignitions. Had it happen once. I noticed speed was down a bit from what I expected at the given fuel flow. Looked at EGTs and immediately knew I was on one ignition.

Larry
 
Last edited:
lr172 said:
In the case of a mag, the RPM indication would go to 0 if it stopped sparking for most, but not all, reasons (the instrument senses the voltage collapse in the coils primary winding, twice per revolution). A Pmag is not that simple. If the CPU failed, RPM would go to 0, but there are many other types of failures that will prevent a spark and not result in a 0 RPM reading, such as a failed coil.

If you pay attention to your engine instruments, it should be pretty obvious when going from 2 ignition sources to 1. Power will drop 5-10% for any given fuel flow and EGTs will rise around 150 degrees from where they were with both ignitions. Had it happen once. I noticed speed was down a bit from what I expected at the given fuel flow. Looked at EGTs and immediately knew I was on one ignition.

Larry
Click to expand...
There is a P-Mag failure where the mag will shift into a "fail-safe" (my phraseology) and will keep running/operating until the next power-down. After that, it will not operate until the failure is corrected.

I had that happen to me a few years ago. The PMAG sensed an issue with the shaft play, and operated fine. Dropped in for a planned fuel stop and the MAG would not come back on-line.

(More kudos to Brad, this was a Sunday afternoon at a strange airport. Over the phone, Brad worked with me and a mechanic I recruited on the field to get me back in the air)

All this to say:
RPM to zero, will only cover the most egregious failure
 
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