P-Mag Test Switches, necessary?

[N941WR]

Originally Posted by apkp777

Bill - Is there any noticeable engine indication when the P-mag switches from self to ships power?

Are you using "test" switches? Your procedure above looks to be a fully functional test of the P-mags with no test switch.

Tony,

I have 113 Pmags which run off ship's power all the time, unless there is a problem, then they switch to internal power. That's why my preflight test is so complex.

To answer your first question, there is no indication from either the 113 or 114 as to where they get their power from.

The EICommander we make only tells you the CPU voltage, not where those volts are coming from. The Pmag doesn't put out that info. However, we can tell you if we can talk to each Pmag or not. That is not perfect but it is close.

Give me a call, if you have any questions.

[Steve Sampson]

Tony, at the risk of confusing I have a different approach to wiring and testing the P-mags. I wanted the operation to be as conventional as possible. Take a look here. You end up with just two mag switches, see here, just above the intercom on the right. I dont like the airliner look or erganomics. If on the ground you need the master on and the p-mags 'off', just pull the fuse.

Bill, you said you test at 800rpm. I am doing this from memory but i seem to remember that mine did not quit until considerably slower than that. I'll check next time I fly,

[N941WR]

Originally Posted by Steve Sampson

...
Bill, you said you test at 800rpm. I am doing this from memory but i seem to remember that mine did not quit until considerably slower than that. I'll check next time I fly,

Steve,

No, I said (or meant) "around 800 rpm". They are all slightly different, each person will have to test their own installation to find when they drop out.

[Bullseye]

Bill, I just wrote you an email offline, but I'm going to ask here, too, to see if I can get anyone else's opinion.

You describe a run-up procedure for the 114 Pmags that checks both ship's power and internal power, but includes some throttle jockeying.

Would the following work?

1) Prior to the run-up (still at IDLE less than your "around" 800 RPM), do a mag check (one side, then the other). You've tested the ship's power.
2) Throttle 1700RPM
3) Do another mag check (one side, then the other). You've now tested the internal power.

I think this accomplishes the same thing, with less power changes.

Does anyone see a problem with this?

[John Collier]

I used a type of DPDT...found the schematics somewhere in the forums. I've got one swith for each PMag...Off / On / Test (Momentary UP position). so my preflight is simply a push up to check the self generation...then if a need to turn a bad PMag off...down to OFF.

Let me know if you are interested in this switch set-up...I'll track down the schematic.

-BC

[Toobuilder]

Originally Posted by N999ZA

Would the following work?

1) Prior to the run-up (still at IDLE less than your "around" 800 RPM), do a mag check (one side, then the other). You've tested the ship's power.
2) Throttle 1700RPM
3) Do another mag check (one side, then the other). You've now tested the internal power.

I think this accomplishes the same thing, with less power changes.

Does anyone see a problem with this?

My understanding of the 114's is that you would not be able to verify "internal" power (even at 1700 RPM) unless you could absolutely remove the ships power (test switch, breaker, master, etc). Since you can't tell which souce is driving the ignition, you can only force the issue by running below the internal cutoff speed or removing external power.

I have dual 113's on mine and I use the standard key for ignition isolation, and the ships master switch as my "test" switch. Though I rarely test the internal power function any more, it takes only seconds to completely isolate and test each unit.

[N941WR]

Originally Posted by Toobuilder

My understanding of the 114's is that you would not be able to verify "internal" power (even at 1700 RPM) unless you could absolutely remove the ships power (test switch, breaker, master, etc). Since you can't tell which souce is driving the ignition, you can only force the issue by running below the internal cutoff speed or removing external power.
...

Very true. Even with the EICommander we can tell you the voltage on the P-mag's board but not where that voltage is coming from. That information is just not availble.

[tadsargent]

Going out on a limb, would it be safe to say the P-mag would not put out 14v
When checking on the internal power with the commander

[N941WR]

Originally Posted by tadsargent

Going out on a limb, would it be safe to say the P-mag would not put out 14v
When checking on the internal power with the commander

No, the P-mags don't need 14 V to run. In fact, you can run them on a 9 volt battery for hand proping.

[Bullseye]

Originally Posted by Toobuilder

My understanding of the 114's is that you would not be able to verify "internal" power (even at 1700 RPM) unless you could absolutely remove the ships power (test switch, breaker, master, etc). Since you can't tell which souce is driving the ignition, you can only force the issue by running below the internal cutoff speed or removing external power.

Originally Posted by N941WR

Very true.

So it sounds like either the 113 or 114 needs either Bill's OFF/INTERNAL/SHIP or John's OFF / ON / TEST type switch setup.

I kind of like the all-the-way-up for normal operation switch position...

It's too bad I don't have more time to think about this...

Oh wait. I've got years to think about this...