Kevin Horton

Kevin Horton

Well Known Member
I've got one each Slick mag and Lightspeed electronic ignition on our RV-8 with IO-360-A1B6 engine. Yesterday the mag had a major mechanical failure, and I plan to replace it with a P-Mag as soon as I can get one delivered. I'm seeking input on the need for a switch in the power wire to the P-Mag.

I have no room on the panel to install a P-Mag power switch close to the two existing ignition switches. If I add a new switch, it will be in some random location, which greatly offends my sense of order. Or, I could replace my current lever-lock mag switch with a three position switch, but now it would differ from my EI switch, in appearance, feel, and toggle angle when the engine is running. This also offends my sense of order.

Reading the P-Mag installation and operation manual, I see no compelling reason to have a power line switch at all. I could easily check the P-Mag's internal alternator immediately after engine start by momentarily turning off the battery master and the Lightspeed EI. The power switching to set the ignition timing would also be done using the battery master.

Am I missing something here? Is there a good reason to install a P-Mag power line switch?

Thanks,
 
Kevin,

Are you going to power the P-mag through a pullable breaker? Or possibly a toggle switch/breaker?

I want to control power to the P-mags.

Bevan
 
The switch is to enable you to test the system.

If you have the supply protected via a cb and are happy to test the system in another method then I can't see a problem.

Not conventional but not unsafe - the P-Mag is grounded safe through the P lead.
 
Bevan said:
Kevin,

Are you going to power the P-mag through a pullable breaker? Or possibly a toggle switch/breaker?
Click to expand...

If I don't have a power switch, there would be no means to kill power from the cockpit, unless I shutdown the whole electrical system.
QUOTE=Bevan;892895]Kevin,
I want to control power to the P-mags.
[/QUOTE]
What are the scenarios where controlling the P-Mag power could be useful?

As I understand it, if the P-Mag timing goes wonky, grounding the P-Lead input (wire #4 on their wiring diagram) should kill the ignition. If grounding the P-Lead does not kill the ignition, removing the DC power input won't help, as the ignition will still be powered by its internal alternator.
 
mike newall said:
The switch is to enable you to test the system.

If you have the supply protected via a cb and are happy to test the system in another method then I can't see a problem.

Not conventional but not unsafe - the P-Mag is grounded safe through the P lead.
Click to expand...
I propose to test the system immediately after engine start by opening the battery master, which will remove aircraft power from the P-Mag. The P-Mag power line will have a fuse for protection.
 
Yet another approach ...

Kevin Horton said:
I propose to test the system immediately after engine start by opening the battery master, which will remove aircraft power from the P-Mag. The P-Mag power line will have a fuse for protection.
Click to expand...

Kevin,

I have been using the *same* (fused) power switch for my P-Mag *and* my ElectroAir electronic ignitions.

I use a keyswitch to check the "mags" as I initially had a magneto.

If I want to test the P-Mag on the ground, I switch to to it alone (keyswitch), power off the EI power and throttle below about 750 (P-Mag stays alive without power being applied if RPM is somewhere around 800 or above.)

This system has worked for hundred of hours.

So I assume that you have a power switch for the Lightspeed EI. If that is independent from your "mag check switch(es)" then your current setup probably could be made to work.
 
jclark said:
Kevin,

I have been using the *same* (fused) power switch for my P-Mag *and* my ElectroAir electronic ignitions.
Click to expand...

Hmm. Interesting idea.

I do have a fused power switch for the Lightspeed ignition. This is a lever-locked switch right beside the lever-locked switch for the mag P-Lead.

I'm not crazy about routing power for both ignitions through one switch though. My plan if the Lightspeed ever goes crazy is to kill its power via that switch. If the P-Mag power was controlled by the same switch, I'd then be relying on the P-Mag internal alternator only if I ever had to kill the Lightspeed. I'd like to keep the two ignition systems a bit more independent.
 
I'm guessing you are going to run the new 114 series which runs on internal power most of the time. In this case you really only have a test switch, so using the ships master is an acceptable way of doing the self test.

This was my original plan for our -8 as well, but I have 113's, and I found it useful to be able to "force" the ignition onto internal power with an accessible switch (or CB, in my case). The 114's are a whole different animal, so no reason for the switch, IMHO.
 
Toobuilder said:
I'm guessing you are going to run the new 114 series which runs on internal power most of the time. In this case you really only have a test switch, so using the ships master is an acceptable way of doing the self test.
Click to expand...
Yes, this will be a brand new 114 series P-Mag.
 
Define "goes crazy" ...

Kevin Horton said:
Hmm. Interesting idea.

I do have a fused power switch for the Lightspeed ignition. This is a lever-locked switch right beside the lever-locked switch for the mag P-Lead.

I'm not crazy about routing power for both ignitions through one switch though. My plan if the Lightspeed ever goes crazy is to kill its power via that switch. If the P-Mag power was controlled by the same switch, I'd then be relying on the P-Mag internal alternator only if I ever had to kill the Lightspeed. I'd like to keep the two ignition systems a bit more independent.
Click to expand...

My thinking is that the P-Mag (114 Series), once fired up is "on it's own" so to speak. Whether I have power to it or not. If I want to take it out of firing for the engine then my action is the SAME as if it was a mag that I wanted to remove.

I have not yet envisioned a power problem that would apply to the P-Mag but not to the "other" EI. So if I have smoking EI wire then I need to turn the power off to BOTH and LAND ASAP.

Probably not within your risk profile but that is how I think about it.

James
 
jclark said:
My thinking is that the P-Mag (114 Series), once fired up is "on it's own" so to speak. Whether I have power to it or not. If I want to take it out of firing for the engine then my action is the SAME as if it was a mag that I wanted to remove.

I have not yet envisioned a power problem that would apply to the P-Mag but not to the "other" EI. So if I have smoking EI wire then I need to turn the power off to BOTH and LAND ASAP.

Probably not within your risk profile but that is how I think about it.

James
Click to expand...

By "goes crazy", I mean fire the spark plugs at the wrong timing, so the engine runs rough or quits.

If there is smoke in the cockpit, my thinking is that it will be pretty much impossible to quickly identify the source. My Smoke in the Cockpit procedure is to open the battery master/alternator switch, which will kill the whole electrical system, except the Lightspeed EI and my turn and bank, both of which are fed from an always-hot battery bus.
 
Because the P-Mag loses internal power below about 750 RPM I installed a DPDT switch with 2 slow blow fuses. Reason-----One day I turned off the P-Mag switch to check the internal power during the run up, got distracted and forgot to reenergize the circuit. Got to destination and on roll out with idle power engine quit! So now I have a light to indicate when the switch is OFF! Just another way of doing it. :) Larry
 
No power switches for any of our P-Mags Kevin - they are powered through pull-able breakers in order to test when needed. SInce I added them well after the -8 was flying, I also didn't have a good spot for the breakers on the norma panel - I put them on the inboard face of the left gear tower where I can reach them. It made adding the wires easy as well - buried them in the gear tower.
 
One possibility would be to ditch the lightspeed and get 2 pmags, each with its own three-position switch. Your sense of (dis)order would not be offended.
 
We have 2 P-Mags with a CB for each for Power.

Only use the CBs for the "once every so often" self-generating test. I would say not having this ability might not be ideal in a Dual P-Mag installation? But cannot see an issue in a single installation if you are willing to kill all ship's power.

When you kill all power, do you still have RPM indications? The full test is to remove power from the P-Mag, having removed the other ignition system - then gently slow engine and note RPM at which self-generating stops.
 
The 114's switch to internal power around 800 RPM, which works seamlessly. However, I had one of my 114's internal generators go bad and the only way I found it was to pull the power on them, one at a time, because it was running on ship's power.

So, yes, you want a way to kill the power on them.
 
Andy Hill said:
When you kill all power, do you still have RPM indications? The full test is to remove power from the P-Mag, having removed the other ignition system - then gently slow engine and note RPM at which self-generating stops.
Click to expand...

That's a great point. No, if I killed all power, I would no longer have an RPM indication. That is definitely a point against my draft plan.
 
N941WR said:
The 114's switch to internal power around 800 RPM, which works seamlessly. However, I had one of my 114's internal generators go bad and the only way I found it was to pull the power on them, one at a time, because it was running on ship's power.

So, yes, you want a way to kill the power on them.
Click to expand...

Did the internal alternator fail completely, so the engine would not run at any rpm if there was no ship's power? Or, did it have a partial failure so that it would generate power at some rpm higher than the normal 800 rpm cutout?
 
N941WR said:
The 114's switch to internal power around 800 RPM, which works seamlessly. However, I had one of my 114's internal generators go bad and the only way I found it was to pull the power on them, one at a time, because it was running on ship's power.

So, yes, you want a way to kill the power on them.
Click to expand...

And this is why I installed a switch as per P-mag recommendation. To ensure that the internal power mechanism is operating properly before flight. Not a big deal until it becomes one. :)
 
N941WR said:
The 114's switch to internal power around 800 RPM, which works seamlessly. However, I had one of my 114's internal generators go bad and the only way I found it was to pull the power on them, one at a time, because it was running on ship's power.

So, yes, you want a way to kill the power on them.
Click to expand...

I echo that you really want a way to kill power to the 144 mag for testing. If panel space is tight then a combination CB Switch is the way to go.

:cool:
 
Kevin, Here is my setup for 4 switches. Turn the 2 outboards off and after they check good turn them back on and then turn the 2 inboard switches off...if they check good, Internals are check and ready for flight!

They are at the very bottom on my panel on the left hand side under the radio stack.

 
LARCO said:
Because the P-Mag loses internal power below about 750 RPM I installed a DPDT switch with 2 slow blow fuses. Reason-----One day I turned off the P-Mag switch to check the internal power during the run up, got distracted and forgot to reenergize the circuit. Got to destination and on roll out with idle power engine quit! So now I have a light to indicate when the switch is OFF! Just another way of doing it. :) Larry
Click to expand...

For this reason, I have a simple warning light that illuminates when the power to PMAG has been switched off.
 
Kevin Horton said:
Did the internal alternator fail completely, so the engine would not run at any rpm if there was no ship's power? Or, did it have a partial failure so that it would generate power at some rpm higher than the normal 800 rpm cutout?
Click to expand...

The internal generator was toast. Once I removed it, you could turn the shaft but it was "crunchy".

When running on the faulty ignition, it would operate fine as long as it had ship's power. Once I turned off the power to it but left it ungrounded, it died. (Step 5, below.)

I wired mine slightly differently:
Pmag%20wiring%203.jpg


This allows me to perform a preflight by doing this:
pmag%20preflight.jpg


One other thing, with the jumper in, your timing starts at 26* BTC. Without the jumper, it is around 30* BTC. Depending on your engine, you may want to connect to it with a PC and the EICAD program and adjust the timing to match your engine / needs. If you make any adjustments with their program, you must leave the jumper out as that program only lets you change the "B" curve.
 
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No disrespect to anyone (and I mean that), but simple is almost always better! I have flown airplanes that had so many switch combinations that only the designer/builder could figure out how to operate them. I guess that is an effective anti-theft design at least.

I flew a couple of airplanes recently where the power and engine systems were far from intuitive - I had several minute briefings on each in order to understand them - and these were single-engine, simple airplanes. I don't see much need for that!

I want to be able to "ground" each mag for a mag check, and I want to be able to kill power to them. That requires a mag switch for each, and a circuit breaker if I am a minimalist. I've flown aerospace craft that were extremely complex because they needed to be - ours don't.
 
Ironflight said:
No disrespect to anyone (and I mean that), but simple is almost always better! I have flown airplanes that had so many switch combinations that only the designer/builder could figure out how to operate them. I guess that is an effective anti-theft design at least.
...
I've flown aerospace craft that were extremely complex because they needed to be - ours don't.
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So true!

Someone I know purposely made his -6A overly complex because that was how he remembered his days in the USAF back in the 60's. There were guarded switches, buttons, etc. scattered all over the place.

If he every had an "issue' while flying, I think the stress would keep him from figuring anything out.

Keep it simple!
 
Kevin,
I also like simple. I have two P-Mags. Standard ignition switch that grounds p-leads for testing on run-up. For testing P-Mag internal alt. I kill master power while above 1000 rpm. I run my P-mag power off a fuse under the panel. If need be I can pull the fuse for testing. I never saw a need for a tach. while testing the internal alternator.
 
MarkW said:
Kevin,
I run my P-mag power off a fuse under the panel. If need be I can pull the fuse for testing.
Click to expand...

Keep in mind that Emagair suggests a resettable circuit breaker, NOT a fuse for power.
Bevan
 
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I used a 3 position switch for my master. The bottom position is "off". The middle position is ships power to everything except the Pmag. The full up position is ships power to everything including the Pmag. During the run up, I position the master to the middle position and then check each side of the ignition system. Upon completion of the check I reposition the master to full up to provide the Pmag with the ships power backup. As with all designs it's not perfect. It would be possible to forget and leave the master switch in the middle position thus causing the Pmags to shut off below 650-800 rpm. However that would normally occur post run up.

A friend had an idea of putting a push button type switch on the panel that would remove power to the Pmag during run ups. The procedure would be to turn one ignition off then press and hold the button. Should see no change in operation. Next turn the first ignition back on and then second ignition off and repeat the push button test.

Just a couple of ideas.

David
 
Bevan said:
Keep in mind that Emagair suggests a resettable circuit breaker, NOT a fuse for power. You should contact them for an explanation but I believe it may have had to do with a crow bar over voltage circuit inside the P-mag.

Bevan
Click to expand...

FYI Brad said that a slow blow fuse was just fine and they have worked fine for many hours in our RV. Larry
 
DeltaTango said:
....
A friend had an idea of putting a push button type switch on the panel that would remove power to the Pmag during run ups. The procedure would be to turn one ignition off then press and hold the button. Should see no change in operation. Next turn the first ignition back on and then second ignition off and repeat the push button test.

Just a couple of ideas.

David
Click to expand...
I considered a pushbutton switch then thought about there failure rate and went with the setup described above.

Just keep in mind that this is your ignition you are messing with!
 
problem with ignition switch

hi there,
fired it up my P-Mags today and now I have this question:

I have the ignition switch from Van's Aircraft installed ( OFF - R - L - BOTH - START ), used that for the Slick magnetos. Now when I fired up the P-Mags strangely enough I can switch to right or left P-Mag, but when I turn the key to "both" the engine goes dead. Anything I overlooked in the installation manual ? Obviously I do have to change the wiring of the ignition switch ? Any advise ? Thanks a lot in advance !

best regards,

Josef
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