SkyView and Pmags

[KRviator]

You'd be forgiven for thinking that there couldn't possibly be any correlation between the two, but you'd be wrong. For those who don't know, the PMag ignitions require ships power below approximately 800RPM, above that, an internal alternator supplies power to the ignition module, making them self-sufficient above your typical flight-idle speeds.

Toying with a couple of spare inputs to my EMS-220, I hooked them up to the terminal screw of both Pmags to monitor and datalog the supply of power, or lack thereof, to the ignitions, and it has become apparent that you can actually monitor whether or not the internal alternator is working.

The benefits of this are several; you can prove at any stage it is working, you have datalogged proof in the event of an accident that the ignitions were both powered and selected 'on', but also using the functionality built into SkyView you can deselect ships power and have an immediate audible and visual warning of the failure of the internal alternator should it occur.

Here is an older screenshot showing the 4 dots in the bottom right. The "x IGN" is simply switched through one side of a DPDT switch, whose other side grounds the P-lead. The "x IGN P" is wired to the ships power input on the Pmag itself. It doesn't know or care where the voltage comes from, so if you deselect ships power after takeoff and have a failure, it'll alarm.

 

[rvator51]

That is a pretty cool use of the Skyview EMS functions!

 

[rlallen1]

Very cool. Wish I knew before removing my Pmags last week.

They for sale if anyone is interested in this feature via the Skyview.

 

[rvator51]

Are they 114s or 113s and what are your asking?

 

[rfazio1951]

KRviator,

Can you give us the setup in the EMS file? What contacts are you using, and how does it show on or off? I would like to use the two for power to the mags mostly. Thanks in advance.

Richard

 

[rlallen1]

I have 2. 114s. They were removed in working condition. In fact, they have about 15 hrs since I had them inspected and software updated by Emag Air, and about 300 total hours.

Asking 1250.00 ea, includes the drive gear

rlallen1@gmail.com

 

[KRviator]

KRviator,

    Can you give us the setup in the EMS file? What contacts are you using, and how does it show on or off? I would like to use the two for power to the mags mostly. Thanks in advance.

Richard

I'm away from the plane for the next few weeks, but I used pins 4 & 23, simply because the wire stripe colour matches the fuel level sender colour for each side.

For the "x IGN", which simply tells SkyView whether the ignition is selected on or not, I grounded it through one side of a DPDT Switch, whose other side grounds the PMag. IIRC, I used 0-2.5V = "OFF" and 2.5-5.0V = "ON". IT is set up as a contact input.

The same applies to the "x IGN P", which tells SkyView whether or not the ignition module is actually supplied with power (either through ships power, or its' internal alternator), 0-2.5V = "OFF" and 2.5-5.0V = "ON".

IF you aren't using Pins 1 & 2, you could use these instead and actually measure the voltage perhaps providing trend monitoring of the ignitions, as pins 4 & 23 are 5VDC limited. They can accept more than 5.0V, but anything above 5 volts shows as 5 volts.

Finally, set them up as self-clearing alarms, rather than latching.

There was a suggestion on the VAF that there was a diode installed inside the Pmag to prevent the internal alternator back-powering the bus, but my experience is you can still measure the voltage. I would suggest a quick check with a voltmeter before you go tearing into your EMS harness, just in case my two Pmags are 'special'!

 

[Carl_Froehlich]

I sent a note to the good folks at e-Mag on this. Here is the response from the guy that designed the p-Mag:

"I am not sure from your link what you are monitoring at the P-Mag connector but I assume it is voltage at the pin#5 (power). This will indicate available aircraft power only. Because the internal power buss on the P-Mag is diode isolated from external power you would not be able to monitor internal buss voltage (generator output) on that pin. In other words, turning off the aircraft power will always result in 0 volts at the power input pin weather the internal generator is working or not."

Carl
600 hours flawless hours on a dual p-Mag install RV-8A. Now waiting too long for the six cylinder p-Mag for the RV-10.

 

[GalinHdz]

"I am not sure from your link what you are monitoring at the P-Mag connector but I assume it is voltage at the pin#5 (power). This will indicate available aircraft power only. Because the internal power buss on the P-Mag is diode isolated from external power you would not be able to monitor internal buss voltage (generator output) on that pin. In other words, turning off the aircraft power will always result in 0 volts at the power input pin weather the internal generator is working or not."

That is what I thought but wasn't sure. I have a wire from each actual P-Mag pin 5 to an unused SkyView EMS input. This way I know for sure the P-Mag is or isn't receiving power on the terminal. If the dot is GREEN then there is ship power at the P-Mag terminal. If the dot is RED then there is no ship power at the P-Mag terminal. You can see the green dots in the screenshot under LMAGST and RMAGST. This also works GREAT for testing the P-Mag during run up. When you cut the power, the dot turns RED but the engine keeps humming along as if nothing happened. This way you are 100% certain you cut the ship's power to the P-Mags and it is running on internal power during the test.

I also did the same with the fuel pump. I ran a wire from the fuel pump connector to an unused SKYVIEW EMS input. When the fuel pump receives power the dot turns BLUE. This is a GREAT way to make sure you don't accidentally leave the fuel pump ON after changing tanks in flight which I have done on more than one occasion.

 

[KRviator]

I sent a note to the good folks at e-Mag on this.  Here is the response from the guy that designed the p-Mag:

"I am not sure from your link what you are monitoring at the P-Mag connector but I assume it is voltage at the pin#5 (power).   This will indicate available aircraft power only.  Because the internal power buss on the P-Mag is diode isolated from external power you would not be able to monitor internal buss voltage (generator output) on that pin.   In other words, turning off the aircraft power will always result in 0 volts at the power input pin weather the internal generator is working or not."

Carl

I must have something special with my two P-mags...Or they're broken! I flew my first flight last weekend, and as part of the run-up check, tested ignition function, and also the operation of the internal alternator. The datalog shows the expected voltage drop of the ignition test, but not a voltage drop during the 'power-source' test, I now have both video evidence and SkyView-logged data that demonstrate that my P-mags will show voltage on Pin 5 when operating with ships power off.

I've got an email into Brad at Emag to see just what this means, but in the interim, I'm quite happy with it!

 

[GalinHdz]

I am monitoring my E-Mag voltage on SkyView and pulled the EMS data from my last flight. It shows a voltage drop during both Mag ignition tests but not down to zero. SkyView only reads up to 5v on the pins I have it connected to so it shows 4.999 with ship power and 4.998 without it.

For this reason I have set up an E-Mag check procedure within my checklist.

With master power ON but the engine OFF I cut the ship power to each E-Mag. The voltage drops to 2.653 and the indicators turns from GREEN to RED. This tells me the test button is working and I am actually cutting power to the E-Mag.

During the engine run up, I cut the ship power to each E-Mag, verify there is no drop in RPM's and the indication stay GREEN the entire time. This verifies the E-Mag is generating the required power when I press the test button. The next time I fly I will pull the circuit breaker and see what SkyView records.