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E Mags and Ignition Switch

rockitdoc

Well Known Member
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Planning my panel. I have dual EMags. Would prefer to have both EMags wired to ignition switch but have seen other panels where there were separate switches for each EMag.

Do EMags have to have separate switches or can they be wired to the ignition switch like conventional mags?

I would prefer to have fewer switches and am more familiar with the mags being on the ignition switch.

Also, what ignition switch is favored for our airplanes?

Thanks, in advance, as usual.

S
 
I had Stein Air plan and layout my panel using dual e-mags. They gave me 2 switches as well.

I believe each switch needs to have its own switch in order to test them. Think about the traditional mags with a keyed switch, both mags essentially have their own switch as well. You have the Off, R, L Both position. This allows you you test each mag separately. In order to do the same with a switch instead of a key you would need quite a complex switch.

Thats my limited knowledge, maybe someone else has more in-depth or better information.
 
You can use a standard, old school ignition switch with pMags if you want. Wire it so the engine starts on both ignitions. I prefer separate ignitions switches and a start button, regardless of the ignition choice.

You do your mag check using the ignition switch just as before. You do the periodic test of the pMag internal generator by pulling the associated pMag breaker with the engine running.

Carl
 
The extra switches are for testing the PMag generators during your run-up so you don't have to wear out the breakers, as I understand breakers aren't designed to be used as a switch constantly.

Basically you want to know if those PMag generators are working so when you temporarily disconnect ship power using the switch or breaker from the PMag they should continue running normally, no stumbling, etc.

On my run-up after I test the regular P-Lead ground with the key switch, I then test the PMag generator with the separate switches (about 3 seconds each).

Whether you have a key switch or regular switches doesn't matter too much.

Edit: The PMag test switches are simply inline between the breaker and the key switch, again there just to save the breaker and make it convenient. For example, in my 14, due to my height, I can't reach the breakers without taking off at least my right shoulder strap.
 
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Question to Carl and bkervaski

When testing the Pmag at runup using the regular keyed ignition switch do you get the same RPM drop as in the regular magnetos, as though one magnetos completely dropped out?

Also, when testing the Pmag generator using a panel mounted switch (or disconnect the circuit breaker), do you also get the same RPM drop as using the keyed ignition swith?

I just finished installed the Pmag wiring yesterday but have no way to test the wiring until many months from now.

Thanks
 
When testing the Pmag at runup using the regular keyed ignition switch do you get the same RPM drop as in the regular magnetos, as though one magnetos completely dropped out?

Also, when testing the Pmag generator using a panel mounted switch (or disconnect the circuit breaker), do you also get the same RPM drop as using the keyed ignition swith?

I just finished installed the Pmag wiring yesterday but have no way to test the wiring until many months from now.

Thanks

PMag RPM drop doing a regular mag check will typically be less than you see with a standard mag.
Note - for those running a pMag has a standard mag, RPM drop will be different dependent on how you set timing.

When testing the pMag internal generator (pulling the power breaker) the pMag will continue to run as before (the reason for the test is to verify this), as such there is no RPM drop. Recommend at least once a year or so reduce RPM during this check to find out how low you can go and still have the pMag produce enough power to run. This is covered in the installation manual.

Carl
 
Also, when testing the Pmag generator using a panel mounted switch (or disconnect the circuit breaker), do you also get the same RPM drop as using the keyed ignition swith?

There should be no change when testing the PMag generators by removing ships power. If there is a change, you have a problem.
 
Just to re-iterate, the PMag generators are only guaranteed to work at 900 rpm or above so if you're at idle and disconnect ships power (switch or breaker) then the engine will shutdown as the PMags stop firing.

"... the internal alternator will be unable to support the ignition somewhere below 900 rpm ..." (page 22 of the manual)
 
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Just to re-iterate, the PMag generators are only guaranteed to work at 900 rpm or above so if you're at idle and disconnect ships power (switch or breaker) then the engine will shutdown as the PMags stop firing.

"... the internal alternator will be unable to support the ignition somewhere below 900 rpm ..." (page 22 of the manual)

Thanks for the explanation. This makes sense now. I was wondering when looking at pictures of RV panels why there are separate Pmag switches in addition on to the ignition keys. Now I know why they are there and why they are needed.
 
As others have mentioned, you need both regular mag grounding ability and electrical cut off testing ability.
 

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I have duel e-mags on a standars ignition switch. To do this you need to remove the jumper that normally grounds the non-impulse magneto during strting. My p-mags are powered off of the master. I do a standard run-up check. Then I do the internal generator check on shut down. I set the idle to 900 and shut off the master. then I uses the ignition switch to do a left/right mag check before I pull the mixture to shut down.
I could do this check on start-up, but I dont like shutting down the electrical system right after power-up. In my mind things are still warming up and booting up, and if I wait to do it at the run-up then I will have to re-power my GPS, radio, ect when I am sitting in the run-up area ready to go. This problem would be easely solved with a seperate e-mag power switch but I chose not to do that. It is one more switch that could be put into the wrong position by accident. You would not know about it until the generator fails.
 
For my PMAG test switches I have 2 normally closed / momentary toggle switches so if I do nothing the PMAGs are provided power and everything works normally. Then, when I do my PMAG check I'll momentarily open the circuit and expect nothing to happen. If it does then I'll have a problem. I changed to this type of switch so I don't have to worry about switching on the PMAG power.
 
I just had to research this recently as I just installed a Pmag. I opted for testing the power via pulling the circuit breaker. Is it as good as having a switch; probably not. Does it work; according to the many many people doing the same thing it appears to. A good Klixon breaker is rated for thousands of cycles as well.
 
Here's how I'm planning to wire up mine. I'll use separate 3-position switches but they include power as well as the P-lead. The sequence is

Off,
Switch on, but power off
Switch on plus power on.

Schematic - P-Mags.jpg

Dave
 
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I just had to research this recently as I just installed a Pmag. I opted for testing the power via pulling the circuit breaker. Is it as good as having a switch; probably not. Does it work; according to the many many people doing the same thing it appears to. A good Klixon breaker is rated for thousands of cycles as well.

My fear with this is that you'll be on a trip and that breaker decides to .. well .. break .. after years of being used as a switch .. and you're stuck :(
 
My fear with this is that you'll be on a trip and that breaker decides to .. well .. break .. after years of being used as a switch .. and you're stuck :(

Quite possible but I bet any shop in the country would either have a spare or you could go to Walmart, Napa, etc. and buy a simple inline fuse to get you by until you make it home. (or better yet just carry an inline fuse in your emergency kit since they could get you out of a pickle)

P.S. I'm of the camp that says you don't need to test it every single flight. Just my 0.02.
 
I just had to research this recently as I just installed a Pmag. I opted for testing the power via pulling the circuit breaker. Is it as good as having a switch; probably not. Does it work; according to the many many people doing the same thing it appears to. A good Klixon breaker is rated for thousands of cycles as well.

After the thread, I just installed a switch for the PMAG that should be ON when the MASTER is turned ON. To test the PMAG alternator, I just need to turn off the power via the switch.
 
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Having a separate switch to test each pMag is not only a good idea, it is recommended by the Mfg. FWIW, this is my setup.

eMag Switches.jpg

:cool:
 
EMAG Test Switch

I just installed one of the new 6 Cylinder EMAGS in my RV-10. I decided to use a round normally closed push button with green LED. The LED is wired in with the PMAG power so I can see if the PMAG has lost power. The EMAG on/off "plead" wire is wired to my standard key switch. When I do my normal mag test with the key switch I press the button while the key is in the left EMAG position. If the engine dies the internal EMAG generator has failed and you should hold the button in until the engine stops or you could get a backfire.

50899917317_f42ec949c0_b.jpg


50899087503_f148b5e1b8_b.jpg


Rob Hickman
N402RH RV-10
 
So, at run up you switch between L and R mags like in a conventional magneto system. But, instead of a drop in rpm, there should be no drop since the internal alt of the P mag takes over. Then, you push the button that grounds the Pmag, and a drop in rpm should occur since the engine is running on only one Pmag.

Do I have this right?
 
So, at run up you switch between L and R mags like in a conventional magneto system. But, instead of a drop in rpm, there should be no drop since the internal alt of the P mag takes over. Then, you push the button that grounds the Pmag, and a drop in rpm should occur since the engine is running on only one Pmag.

Do I have this right?

No,

The ignition key switch works just like mags: Left position the EMAG only is running, Right position the Lightspeed is only running and in BOTH they both are working. The switch grounds the Ignition control wire of the opposite ignition to turn it OFF. The lighted push button interrupts the power to the EMAG causing the EMAG to run on its internal alternator only.

This is how I do my MAG check:

- Engine 1900 RPM
- Key to R - Check RPM drop with only the Lightspeed running
- Key to L - Check RPM drop with only EMAG running on aircraft power
- Key still on L - Hold Button in to verify that the EMAG will continue to run without external power using it's internal generator.


Rob Hickman
N402RH RV-10
 
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Still Confused....as usual

I still do not understand the purpose of both an ignition switch to activate the Pmags, L, R and Both (I will have two Pmags) in addition to two separate switches to turn off each PMag. The L, R, Both ignition switch can turn off ship power to each PMag. During runup, by switching between L and R PMags, no drop in rpm means the internal alternator of the pmag that has been turned off is working (or, that the ship's alternator is faulty and you are only operating on the pmag alternator) . If a drop in rpm occurs (assuming you are above 900rpm), that pmag internal alternator is not working.

Having a separate switch or pulling a breaker to cut power to the pmag seems redundant. You can do that at the ignition switch. If no no drop in rpm occurs you still don't know if the ship's alternator is working.

Is redundancy the only reason to have the separate switches to turn off the pmags?

Or, am I still confused?
 
I still do not understand the purpose of both an ignition switch to activate the Pmags, L, R and Both (I will have two Pmags) in addition to two separate switches to turn off each PMag. The L, R, Both ignition switch can turn off ship power to each PMag. During runup, by switching between L and R PMags, no drop in rpm means the internal alternator of the pmag that has been turned off is working (or, that the ship's alternator is faulty and you are only operating on the pmag alternator) . If a drop in rpm occurs (assuming you are above 900rpm), that pmag internal alternator is not working.

Having a separate switch or pulling a breaker to cut power to the pmag seems redundant. You can do that at the ignition switch. If no no drop in rpm occurs you still don't know if the ship's alternator is working.

Is redundancy the only reason to have the separate switches to turn off the pmags?

Or, am I still confused?

You are confusing 2 different things. The key switch L-R-Both works just like with a traditional magneto, grounding it so it can't spark. The toggles or whatever means you like are for cutting ship power to the P-Mag thus allowing a check to see if the P-Mag is still working without ship's power.
 
You are confusing 2 different things. The key switch L-R-Both works just like with a traditional magneto, grounding it so it can't spark. The toggles or whatever means you like are for cutting ship power to the P-Mag thus allowing a check to see if the P-Mag is still working without ship's power.

Ignition switch (ship power) cuts power to PMags. Check. Separate switches (or breakers) cut ship's power to PMags. Seems like they do the same thing. Why have two sets of switches?
 
You are confusing 2 different things. The key switch L-R-Both works just like with a traditional magneto, grounding it so it can't spark. The toggles or whatever means you like are for cutting ship power to the P-Mag thus allowing a check to see if the P-Mag is still working without ship's power.

This ^^^

It can get confusing because some folks do put switches that ground the spark (P-Lead) as well as switches that remove ship's power. Usually, these are push button start setups but I've seen a couple retrofits that have key switch plus two additional switches. Assuming the key switch in these applications has the P-Lead (L/R) disabled.

Ultimately, you want two switches for each PMag. One can be a key switch.
 
Ignition switch cuts power to PMags. Check. Separate switches (or breakers) cut power to PMags. They do the same thing. Why have two sets of switches?

No, ignition switch grounds the magneto (and P-Mag)exactly the same way, they are still operating but the grounding prevents spark and the P-Mag is still getting power from the airplane + it's internal alternator. Toggle switches stop ship's current from reaching the P-Mag.
 
There are two steps to fully checking a self powered electronic ignition which is slightly different than a regular magneto. You have to check if the magneto works with and without ship power. I test this before every flight.

In my dual pMag install the ship 12v power goes from a circuit breaker through individual, normal closed, push buttons to pin #5 on each pMag.

PModel 114 Wiring.jpg

I have an additional wire from the pMag pin #5 back to my DYNON EMS-220 which monitors pin #5 voltage. This is displayed by a Green/Red indication on my Skyview EMS page.

N819PR1088hrs-EMS.jpg

FWIW, This is how I do my MAG check:

With main POWER ON but engine OFF
Press each Mag button and each Mag power indicator should go from GREEN to RED and back to GREEN. This confirms the push button actually cuts the power to the pMag.

With engine at 1000 RPM
Push each button and the engine should not exhibit any drop in RPM's. This confirms each pMag internal generator is working correctly.

With engine at 1800RPM (regular Magneto check)
Key to L - Check RPM drop with only the left Pmag ignition working
Key to R - Check RPM drop with only the right Pmag ignition working
Key to BOTH - Go fly

:cool:
 
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P.S. I'm of the camp that says you don't need to test it every single flight. Just my 0.02.

Maybe not every flight, but every flight day. It takes literally 6 seconds (3 seconds per side) if you have the switches installed on the panel.

The switches are REALLY easy to install, the hardest part is drilling the holes.

pmag_switch.jpeg
 
I think I finally get it. Tell me, if not.

Ignition switch to L cuts ALL power to R Pmag. A loss of rpm SHOULD occur and this checks to see if engine will run on one Pmag.

Separate toggle switches for each pmag only turn off ship’s alternator power to pmags and If no loss of rpm occurs, checks if internal alternator in each pmag is working.

Right?
 
I think I finally get it. Tell me, if not.

Ignition switch to L cuts ALL power to R Pmag. A loss of rpm SHOULD occur and this checks to see if engine will run on one Pmag.

Separate toggle switches for each pmag only turn off ship’s alternator power to pmags and If no loss of rpm occurs, checks if internal alternator in each pmag is working.

Right?

Nope.

Ignition switch (historically called P-Lead) just turns off the spark for that particular PMag.

The test switch (or pulling the breaker) disconnects ships power at which point the PMag's onboard generator should continue providing spark. If it stumbles, your PMag generator has failed and you have a no-go.

The PMag's onboard generator keeps the spark going similar to a traditional mag. It's wired to ship's power for backup. The only way to test whether the generator is generating is to remove ship's power.

To re-iterate the manual, the generators only work above 900rpm. Below 900rpm the PMags are always on ship's power.
 
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Nope.

Ignition switch (historically called P-Lead) just turns off the spark for that particular PMag.

That's what I thought I said. When this switch is turned to L (left), that pmag is on and running the engine. The R (right) pmag is off, including it's internal alternator. The rpms should drop a bit, indicating that the R Pmag was turned off and the engine will continue on one pmag.

The test switch (or pulling the breaker) disconnects ships power at which point the PMag's onboard generator should continue providing spark. If it stumbles, your PMag generator has failed and you have a no-go.

The separate switch (or breaker, if a separate switch is not fitted) is used to test the internal alternator of each pmag. The ignition switch can't do this since it cuts ALL power to the pmag.

Makes sense, now.

I didn't realize the ignition switch cut all power to the pmag. I thought the internal alternator in the pmag would cut in when the ignition switch was switched to L or R. That's why I thought the extra two switches were redundant. Just trying to eliminate switches on my panel if not needed. Two more switches needed.

Thanks everyone. This helped a lot.
 
That's what I thought I said. When this switch is turned to L (left), that pmag is on and running the engine. The R (right) pmag is off, including it's internal alternator. The rpms should drop a bit, indicating that the R Pmag was turned off and the engine will continue on one pmag.



The separate switch (or breaker, if a separate switch is not fitted) is used to test the internal alternator of each pmag. The ignition switch can't do this since it cuts ALL power to the pmag.

Makes sense, now.

I didn't realize the ignition switch cut all power to the pmag. I thought the internal alternator in the pmag would cut in when the ignition switch was switched to L or R. That's why I thought the extra two switches were redundant. Just trying to eliminate switches on my panel if not needed. Two more switches needed.

Thanks everyone. This helped a lot.

Almost there- the L switch grounds the right P-Mag preventing spark only, the ship's power and internal alternator on the right mag are still functional. The only way to remove ships power from a P-Mag is via the toggle switch or CB whichever you have. The only way to stop an internal alternator on a P-Mag is to go below 900 RPM. Remember it this way - key switch only stops the spark, toggle or CB prevents power to the P-Mag and below 900RPM is the only way to stop an internal alternator.
 
OK, I just spoke to the Emag folks about the P Model and switches.

Here's what they said (which is probably what everyone here has been saying, but I just wasn't getting it):

Runup at 1800rpm
Turn keyed ignition (kill) switch from the Both position to Right mag position. Engine is now running on just the Right mag. (This proves it can)
While the kill switch is still set on the Right mag, flip the switch, push the button or pull the breaker that turns power off to the Right mag.
If the engine keeps running, it means the internal alternator in Right mag is keeping things going. If the engine dies, internal alternator needs help.

Same process for Left mag.

Now, I get it.:D
 
This is my P-Mag Set up, flying with it for 160 hrs+ love it. Easy to check all in one location. Durning Run up. I (pull and lift up) both P-Mag S/W's to insure NO Drop in RPM. (This cuts the ships power to both P-Mags) The P-Mags generators check complete. Then I do the normal ignition check turn one off (Pull and move down OFF) look for a RPM drop repeat on then the other side. All in one place and ez. Switches from Stein Air and installed by Stein Air. Sept2020
 

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This is my P-Mag Set up, flying with it for 160 hrs+ love it. Easy to check all in one location. Durning Run up. I (pull and lift up) both P-Mag S/W's to insure NO Drop in RPM. (This cuts the ships power to both P-Mags) The P-Mags generators check complete. Then I do the normal ignition check turn one off (Pull and move down OFF) look for a RPM drop repeat on then the other side. All in one place and ez. Switches from Stein Air and installed by Stein Air. Sept2020

I like it! PMag internal alt test on up movement, PMag operation with ship power on down movement. Clever. So, when you get ready to go after runup, you put both switches in the On position.

It also appears you have your taxi and landing lights on one switch. Center for taxi, up for landing?

Does the red switch turn on the avionics?
 
P-Mags FlyLED

P-Mags (every movement of the switch requires you to pull 1st, makes it almost impossible to accidentally switch off) Off is down, Hot or ON/Run is in the Center, Up is ship/aircraft power OFF. So center is P-Mag on normal with aircraft power. Yes light Off Taxi & Taxi/Landing, I used FlyLED in the wing tip, they are great! With the Taxi or Taxi/Landing ON(When the strobe are off they light up at 30% power (steady) to light up the edge of the taxi way. (Side Lighting) They were fun to built too! #PricedRight #FlyLED #Pmag Getting ready to pull the trigger on a QuickBuild RV14A. You will see more of me.... Red Switch turn on the lithium back up battery, powers up the G3x's and more.

I like it! PMag internal alt test on up movement, PMag operation with ship power on down movement. Clever. So, when you get ready to go after runup, you put both switches in the On position.

It also appears you have your taxi and landing lights on one switch. Center for taxi, up for landing?

Does the red switch turn on the avionics?
 

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