Wiring the E-Mag On-Off-Test switch?

[claycookiemonster]

I have the wiring diagram from Stein's page selling the locking toggle switch. Numbered terminals begin at number 1 at bottom right, number 3 is top right, number 4 is bottom left and number 6 is top right. Number 2 is middle right and is the P-Lead. Number 3 is top right and is the ground. So far, so good. Terminals 5 and 6 both seem to be power leads. Number 5 shows it going to "VPX or Circuit Breaker" which sure sounds like power. Number 6 shows a connection to "P-Mag Power."

I asked Tim at Stein's and he tried, but I need a lift up to his level of understanding. He mentioned that number 5 was an "always on" power source, while number 6 was a switching input? That didn't help me, but maybe one of you geniuses can understand.

 

[D-Dubya]

I'm no genius, but let me see if I can make the light come on (pun intended)...

1 - Not connected to anything
2 - P-lead to the E-mag; this essentially serves the same purpose as a P-lead on a magneto and renders it inoperable
3 - Aircraft Ground
4 - Not connected to anything
5 - Aircraft Power "TO" the switch from VPX, circuit breaker or fuse
6 - Power "FROM" the switch to the E-mag (connected only in the middle switch position)

The normal running position is the middle position, which provides power to the ignition. The test position is fully up, which drops the plane's power to the E-mag, thereby testing its self-generating circuitry. You're supposed to test that on each E-mag as part of the engine run-up.

 

[2theskyy]

A few choices from vpx manual. I’ve been looking at the options as well. Thinking of going with #1 choice and power test via G3x and have each mag on a locking toggle switch. Power looks like on 5 and p leads on 4.

 

[2theskyy]

I’m a visual type of learner if any of these help you

 

[N804RV]

This is what I went with; and off-the-shelf solution from Steinair (note the wiring diagram included: https://www.steinair.com/product/locking-toggle-switch-p-mag-test-on-on-mom/

 

[FlyingSquirrel]

This is what I went with; and off-the-shelf solution from Steinair (note the wiring diagram included: https://www.steinair.com/product/locking-toggle-switch-p-mag-test-on-on-mom/

Thanks for posting the diagram.

This switch is doing two separate things.

First it is enabling and disabling the P-Mag with contacts 2 and 3. The yellow wire is the "kill switch" wire connected to the P-Mag. when the switch is in the down position contacts 2 and 3 are connected, and the "kill switch" wire is grounded, disabling the P-Mag. when the switch is in the middle "run" position and the momentary up "test" position the switch is connecting contacts 1 and 2 leaving the kill switch open and the P-Mag capable of firing.

The other half of the switch is running the P-Mags internal alternator. The P-Mag has an internal alternator that needs ships power to energize, but once the engine is running it should keep itself running without an external power source. To test this you momentarily remove power from the P-Mag alternator and watch to make sure there is no RPM drop, indicating the internal alternator is working. In the "off" position and "run" position contacts 5 and 6 are connected providing 12v to the P-Mag. In the test position contacts 4 and 5 are making contact, removing power from the P-mag.

The switch is depicted upside down as it will need to be positioned this way for the spring loaded test position to be at the top.

A typical P-Mag check using this switch would look something like this:

with the engine running
1. Move the left ignition switch to the off position, observe the RPM drop.
2. Move the left ignition switch to the run position, the RPM should recover.
3. Move the right ignition switch to the off position, observe the RPM drop.
4. Move the right ignition switch to the run position, the RPM should recover.
5. Move the left ignition to the test position, RPM should remain stable. Release the switch and it should return to the run position.
6. Move the right ignition to the test position, RPM should remain stable. Release the switch and it should return to the run position

I hope this helps!

 

[Girraf]

Thanks for posting the diagram.

This switch is doing two separate things.

First it is enabling and disabling the P-Mag with contacts 2 and 3. The yellow wire is the "kill switch" wire connected to the P-Mag. when the switch is in the down position contacts 2 and 3 are connected, and the "kill switch" wire is grounded, disabling the P-Mag. when the switch is in the middle "run" position and the momentary up "test" position the switch is connecting contacts 1 and 2 leaving the kill switch open and the P-Mag capable of firing.

The other half of the switch is running the P-Mags internal alternator. The P-Mag has an internal alternator that needs ships power to energize, but once the engine is running it should keep itself running without an external power source. To test this you momentarily remove power from the P-Mag alternator and watch to make sure there is no RPM drop, indicating the internal alternator is working. In the "off" position and "run" position contacts 5 and 6 are connected providing 12v to the P-Mag. In the test position contacts 4 and 5 are making contact, removing power from the P-mag.

The switch is depicted upside down as it will need to be positioned this way for the spring loaded test position to be at the top.

A typical P-Mag check using this switch would look something like this:

with the engine running
1. Move the left ignition switch to the off position, observe the RPM drop.
2. Move the left ignition switch to the run position, the RPM should recover.
3. Move the right ignition switch to the off position, observe the RPM drop.
4. Move the right ignition switch to the run position, the RPM should recover.
5. Move the left ignition to the test position, RPM should remain stable. Release the switch and it should return to the run position.
6. Move the right ignition to the test position, RPM should remain stable. Release the switch and it should return to the run position

I hope this helps!

From eMAG:
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.


My interpretation of the guidance from eMag suggests the sequence would be:
From both mags in the run position
Turn Right mag off, push left mag to test position and release
Turn right mag back on
Turn left mag off, push Right mag to test position.
Turn left mag back on
Go fly

 

[claycookiemonster]

Ahhhhh! Power IN, and then switched power OUT! So simple after all you geniuses explained it. Thanks!

 

[Freemasm]

This is what I went with; and off-the-shelf solution from Steinair (note the wiring diagram included: https://www.steinair.com/product/locking-toggle-switch-p-mag-test-on-on-mom/

I don't have P-Mags but my ECUs are the same for run and test modes. I'm panel space limited so eliminating separate switches for power and test would be beneficial. I researched and found these switches independent from Stein's offering.

FWIW, I have tested the reference Honeywell switch(es) and they will perform a legitimate test. I was worried that a momentary loss of continuity on the hot side between center/extreme positions could give a false indication of proper operation. This power continuity is maintained on the while closing the ground "test" when positioning from center to extreme if wired like the above. They are expensive but it cleaned some things up for me. Again, FWIW.

 

[Bavafa]

With this type of switch, how do you guys put the PMAG in the config mode to time it?
The config mode is when the PLEAD is grounded and power is applied, short of adding a temp ground wire right at the PMAG itself.

 

[FlyingSquirrel]

With this type of switch, how do you guys put the PMAG in the config mode to time it?
The config mode is when the PLEAD is grounded and power is applied, short of adding a temp ground wire right at the PMAG itself.

This condition is met with the switch in the "off" position and your master switch on. The only time this switch removes 12v power from the P-Mag is when the switch is in the "test" position.