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Dual Plasma questions and poll

Do you have a dual Plasma ignition system?


  • Total voters
    17

Janekom

Well Known Member
Patron
To the brain force out there. I am trying to educate myself a bit.

I have this perception that the Plasma ignitions systems are very reliable. I know of at least two RVs with dual Plasma systems and no backup battery.

I am sure there are many arguments for a backup battery and there are also those who will say it is not needed on a day VFR ship.

Your opinions will be much appreciated.
 
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It's not about the reliability of the ignition per se, it more about the reliability of the aircraft electrical system.
 
We Went Simple

Installed a Plasma III on our RV-6 and kept the left magneto. There. Nearly all the advantages of a dual Plasma with the simple, lightweight backup of the magneto that does not notice or care if the airplane electrical system fails.
 
I am running dual plasma II's with dual batteries and dual alternators and a bus tie. I totally agree with Walt. Somewhere along the way I read here where someone broke a alternator belt which ripped the wires out from the trigger mechanism up front and when that happens you have nothing.
 
My first RV-8A started out life 20 years ago with dual Plasma II+ ignitions, and a power system designed to make sure at least one always had power.

I removed this ignition at ~300 hours after multiple failures, two in flight. That airplane has been flying now for ~1000 hours on dual pMags that have been flawless. I installed dual pMags on my current RV-8 (~270 hrs) and there is a single six cylinder pMag and standard mag flying on my old RV-10.

Perhaps my experience with Lightspeed is not typical, but I can report other Lightspeed users I know have either gone to pMags or back to standard mags.

Also I wonder if the product has been revised over the last 20 years.

I do not have any data to demonstrate if the Plasma III is more reliable than the II+. Perhaps others can comment.

Carl
 
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Dual Plasma II with 2.3Ah back-up battery.
Been running flawlessly since 2005, 1’100 hours.
 
Thread Drift....Sorry

Our Plasma III has about 200 hours over about, um, three years I think. Absolutely, perfectly flawless. Klaus saw my installation, in fact made up the spark plug wires for me and insisted on being present for the first start. Complimented me on the installation and commented "Looks like you read the manual."
 
One other comment, if you run dual ship power dependent ignitions I strongly recommend a robust electrical power design. Perhaps they exist but I have not seen a “per instructions” backup battery install that satisfies my risk tolerance. Specifically these backup battery schemes do not provide adequate electrical reserves (should be more that 90 min for me), many do not provide indication of backup battery health during normal operations, and I’ve found some of these backup batteries to be dead in flying airplanes (as in installed a decade ago and forgotten).

It can be done, but hard with just a single ship battery as your base. I suggest there are many advantages to a two identical ship battery design that uses no backup batteries (either for the engine or the panel).

Whatever you do test it! You don’t want to find out if it works or not when you really need it. Make sure whatever switch manipulation are needed (if any) to keep the fan running are clearly documented in your POH Emergency Procedures - and routinely tested.

Carl
 
One other comment, if you run dual ship power dependent ignitions I strongly recommend a robust electrical power design. Perhaps they exist but I have not seen a “per instructions” backup battery install that satisfies my risk tolerance. Specifically these backup battery schemes do not provide adequate electrical reserves (should be more that 90 min for me), many do not provide indication of backup battery health during normal operations, and I’ve found some of these backup batteries to be dead in flying airplanes (as in installed a decade ago and forgotten).

It can be done, but hard with just a single ship battery as your base. I suggest there are many advantages to a two identical ship battery design that uses no backup batteries (either for the engine or the panel).

Whatever you do test it! You don’t want to find out if it works or not when you really need it. Make sure whatever switch manipulation are needed (if any) to keep the fan running are clearly documented in your POH Emergency Procedures - and routinely tested.

Carl

This is gospel.

If one or more of a critical ship function requires electrons, make certain you have a solid robust method of delivering them for Plan A, B and C.

As for the poll - it doesn't matter how reliable the electronic ignition system is, if you have a cheap alternator. The chain is only as strong as the weakest link.
 
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I do not have any data to demonstrate if the Plasma III is more reliable than the II+. Perhaps others can comment.

Carl

I think that they are both quite reliable units but it is most likely that the Plasma 11+ is slightly more reliable than the later Plasma 111. It is my understanding that the longer spark duration of the Plasma 111 puts greater stress on the coils. But the Plasma 111 proved more popular because it had a higher number so everyone just assumed it must be better technology.

It was a bit like the Spinal Tap amplifiers that had a volume control that went to eleven :D
 
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Returning to topic....

Originally Posted by Janekom:

I am sure there are many arguments for an emergency backup battery and there are also those who will say it is not needed on a day VFR ship. Your opinions will be appreciated.

It's funny how terminology can change perception. Here the second battery is called an "emergency backup". It's a reasonable perception based on the wiring diagram in the Lightspeed manual, reproduced below. Note the "power select switch" in the power path for IGN2. Although it can be operated either way, the natural perception is that the power select will connect IGN2 with the main battery during normal operation, and be switched to the "backup battery" in the event of alternator, main battery, or main battery supply wiring failure.

The obvious fault with this scheme is the requirement for pilot intervention. For sake of this discussion, eliminate the power select switch. Wire IGN2 directly to the second battery.

Ok, new perception. The second battery is no longer a "backup". Each battery, battery connection, power supply wiring, switch, CDI unit, and ground path are essential elements of an individual ignition system. "Dual" truly become two complete systems.

VFR or IFR? The only difference is the minimum required run time with a failed charging system. In the past, a VFR install might use a second battery smaller than the main, which was mostly a weight saving measure given the installs were lead/acid. Given the low weight of lithium iron phosphate, it's now possible to install two equal, high capacity batteries with no penalty other than cost.
 

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Looking at the classic Lightspeed diagram for the aux battery demonstrates a key design problem.

Assume the aux battery is dead. Unless the pilot opens the breaker before the diode that feeds that battery, the volt meter will read main battery voltage (minus the drop across the diode). So pilot action is needed to know if the aux battery is even there.

I wonder how many of these are flying and the pilot never did this check. I found an RV with this exact setup. The aux battery no load terminal voltage was around 2vdc.

Know how your system works, and verify it works on a routine basis.
Carl
 
Looking at the classic Lightspeed diagram for the aux battery demonstrates a key design problem.

Assume the aux battery is dead. Unless the pilot opens the breaker before the diode that feeds that battery, the volt meter will read main battery voltage (minus the drop across the diode). So pilot action is needed to know if the aux battery is even there.

True.

Most of us have voltage monitoring on an EFIS or EIS, which covers the main battery and charging system. It's easy to wire a simple test system for the second battery (green below), just a relay, a momentary ON button, and a $5 voltmeter display. Pushing the button with the ignition operating displays battery voltage under load.

Also installed a voltage monitor on IGN2 (yellow). If running voltage drops below normal charging voltage (open diode, relay, or wiring) I get an aural tone and a flashing LED. That means pushing the aforementioned test button also checks the voltage monitor.

Test button gets punched on the runup pad, standard left-to-right checklist, after boost pump on.

About $20 total.
.
 

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Thank you for all the VERY valuable inputs here. This what this forum is about - to learn from others and not to go and make silly mistakes.

DanH my apologies if my terminology is wrong by calling it an emergency backup battery. I will change it to read just backup battery.

I have also downloaded the manual last week sometimes and the diagram that DanH has attached is what has sparked my interest or rather worry about this.

I could not understand that the the backup battery will only run IGN B.

Whatever one do, one should make sure that your backup battery voltage is really good and that it can take the load.

@ Rovili - I have tried but do not know how to change the poll options.
@ Carl - I have sent you a PM.
 
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DanH my apologies if my terminology is wrong by calling it an emergency backup battery. I will change it to read just backup battery.

Jan, that's the point about terminology. Don't think of it as "emergency" or "backup". It's simply the IGN2 supply battery.

Here's another way to look at it. It's common to see one big battery and one small battery, which can lead a person to thinking auxiliary or backup. Reality? The big one is a starting battery. In truth, our inflight battery requirement is limited (the alternator is carrying the load). If it wasn't for the starting load, we could do fine with a pair of identical, relatively small batteries...each independently serving its own ignition system.
 
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I've had dual direct crank LS3's since around 2007, replacing the thrice failed Lasar system. I did not wire it as per LS's installation, as I (like Dan) did not want any action on the pilots part to be necessary in the event of a main bus failure. I simply have a smaller battery whose only function is to power ig 2 all the time. It receives its charge through a diode from the main bus. I have both battery voltages monitored and alarmed on the G3X. I check battery 2's voltage prior to startup. Another problem area with LS's instructions are the always hot wires with no protection. Always hot is a good idea for ignitions, but one needs a fusible link at the battery. Both ignitions get their juice right from the battery terminals.

I did have one LS brain box croak last summer. It took a couple weeks to get it shipped out/fixed/returned, so I'm going to actively look for a spare LS3 box.

One large blind spot is not knowing, during flight, if an ignition stops sparking. Perhaps some EE here can design a monitor circuit with something to wrap around one lead from each ignition that detects a fault.
 
I live in the states and gave up dealing with Klaus after multiple failures, I can't even fathom doing that from half way across the world.

My advice, go with mags.
 
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One large blind spot is not knowing, during flight, if an ignition stops sparking. Perhaps some EE here can design a monitor circuit with something to wrap around one lead from each ignition that detects a fault.

The failure modes of the P3 and indications are a bit of a mystery. However, I did bite the bullet and wired in the Flight Data Systems L2E and the LED outputs from each P3 box to my Garmin G3X Touch/GEA24/GAD27. With this configuration, I can monitor (not control) the timing of each P3 (as reported by the P3) on the Garmin G3X Touch. If power is lost to either of the P3's I also see a message on the CAS and hear an alert.
 
My Plasma II has first flown in 2005, in what was a strictly VFR ship. The install follows Klaus directives and has been working without any problem.
Note, a new wording has been used here, Alternate Ignition ;)

Yes, it requires human interaction in case the main battery circuit, for whatever reason, is or has to be set offline.
Yes, it works on IGN system #1, which means a remote possibility exists in having a failure on system #1 whilst having to switch the Main bus to OFF.
Yes, it is being checked before every flight, during the run-up procedures: At given RPM IGN 1 and 2 are sequentially switched OFF/ON, then the IGN ALT ON, and both IGN 1/2 OFF, this way the separate circuit of the Alternate Ignition is being checked under load.
The alternate ignition battery gets replaced every 2nd year as a part of the maintenance schedule.

Of course, as suggested by DanH, with today's increased reliance on electronic instrumentation, and electrical accessories, a 2 batteries elec configuration makes more sense and gives redundancy for the aircraft as a whole.
 

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