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P Mag problem after start

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Gingameigs

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Have dual P mags fitted to a io360 and after start when engine cold the left mag is dead for around 6-8 mins. After that mag is alive and cannot fault it at all . Mags have done around 200 hours but have been on aircraft for some time . Seems to be maybe a heat issue anyway just wondering if anyone has experienced this type of problem as we are about to pull it off to have it looked at .
 
Gingameigs said:
Have dual P mags fitted to a io360 and after start when engine cold the left mag is dead for around 6-8 mins. After that mag is alive and cannot fault it at all . Mags have done around 200 hours but have been on aircraft for some time . Seems to be maybe a heat issue anyway just wondering if anyone has experienced this type of problem as we are about to pull it off to have it looked at .
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I'd carefully check the wiring into the green screw-down connector (terminal block). There have been reports of them coming loose. You could also consider installing "ferrules" on the wires before putting them into the screw-down connector.
 
Pmags all have heat indicator dots on them that turn black if they've been subjected to unusually high temperatures. It may be the first question that E-Mag asks you when you call them. My experience has been that they're very helpful on the phone. I was told by them that heat related failures of Pmags are quite unusual.
 
Don't use Pmags, so can't speculate on cause. However, IMHO you are tempting fate if you don't find and address the reason. What you are seeing is not normal and likely to progress into a problem that doesn't go away in 6 minutes.
 
RPM

What RPM is the engine at during this 6-8 minutes, idle? Is the Pmag connected to ship's power? Sounds like there isn't power to the PMag until it reaches sufficient RPM to generate its own power.

A simple test could help determine if this is the problem. Start the engine and slowly increase the RPM. Note if the left PMag "starts running" at a certain RPM or if at a specific time.

The earlier suggest of checking the connectors is a good place to start. But calling Brad is also an excellent idea.
 
Can you start the engine on the left pMag only? Have you checked the status LED on the back of the pMag upon power up? Might be a reasonable troubleshooting step.
 
I'm betting on Scott's assessment.
Please follow up and let us know what you find.
 
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Thanks for the replies. Certainly not an RPM problem, the mags have always been checked at around 1700rpm prior to flight and regularly checked prior shutdown to confirm that the built in alternator is working. It's hard to know how long it's been a problem because the run-up checks have always been done after the engine is warm at which time both mags have always worked flawlessly.
I'll call Brad.
 
Gingameigs said:
Thanks for the replies. Certainly not an RPM problem, the mags have always been checked at around 1700rpm prior to flight and regularly checked prior shutdown to confirm that the built in alternator is working. It's hard to know how long it's been a problem because the run-up checks have always been done after the engine is warm at which time both mags have always worked flawlessly.
I'll call Brad.
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Doing the internal power check at 1700RPM's is not a good idea. This check should be done at no more than 1,000RPM's (more like 800-900RPM's) to insure the generator is working correctly.

FWIW your best course of action is:
Carl Froehlich said:
Call Brad at eMag.

Carl
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GalinHdz said:
Doing the internal power check at 1700RPM's is not a good idea. This check should be done at no more than 1,000RPM's (more like 800-900RPM's) to insure the generator is working correctly.
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I think you might confusing the routine internal alternator check with the less frequent cut-out test.

Directly from the manual:

Ignition Checks

Your ignition checklist will be extended to include two different ignition alternator checks. The first check will blend easily into your regular left/right Ramp Check routine. The other (Cut-Out test) will be done less frequently. See power test switch and wiring diagram later in manual.

1) Ramp Checks (roughly 1700 RPM).

a) Internal Alternator - E-MAG internal alternator operates in parallel with power supplied by the aircraft bus. The ignition automatically transitions between aircraft power and internal alternator power as needed. Aircraft power is required for starting and low idle speeds.

i) Running on one ignition only, turn ignition power test switch OFF for 2-3 seconds and back ON. The engine should run smooth during the momentary bus power outage, verifying the internal alternator is working.

ii) Repeat with the other ignition.

iii) The left/right Ramp Check rpm drops may be quite a bit different with E-MAGs than magnetos. We don’t apply the same rules to gauge ignition health. Any rough or degraded behavior (before, during, or after each side’s Ramp Check) indicates a problem - not suitable for flight.

2) The Cut-Out Test (ground run) should be done after initial installation, power plant maintenance, and at annual inspection. It checks ignition condition, and the entire engine system, in challenging conditions. Internal alternator output will drop at low engine speeds. Forcing the ignition to its low-speed low-power limit demonstrates the system’s capacity to operate below your in-flight idle – typically 1000 to 1100 rpm. Cut-Out Test

a) Operating on one ignition, lower engine speed to 1200 rpm. Then turn bus power OFF to that ignition. A slight rpm dip may be expected due to the lowered spark energy.

b) Very slowly lower the engine rpm until the engine reaches low idle limit or quits. A log-book entry will help you track Cut-Out trends over time.

c) Repeat Cut-Out test on the other ignition, and then with both ignitions.
 
Does anyone know how a Pmag performs when run on internal alternator power for any length of time? Say 30 minutes or more…. It seems they are pretty sensitive to high temps and if generating their own power, they’re going to get hotter, maybe significantly hotter.
 
If memory serves, pMags always run on internal power other than start and low RPM. The pMag generator is diode isolated from back feeding ship power using diodes.

Carl
 
If memory serves, the 113 series used ships power as primary, but the 114 uses internal generator as primary (with the ship providing start and BU power).
 
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