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From: Gary Casey <glcasey@adelphia.net>
Subject: Re: Lightspeed Plasma III in Performance Engine

As I understand it, the Lightspeed system has a good reputation for  
reliability.  However, I had a failure on my Plasma III system.  The  
first symptom was a sudden knock from the engine that sounded like  
one cylinder and lasted probably 1/2 second.  At that time 2 EGT's  
climbed about 100 degrees and stayed there.  I immediately turned  
back to the airport and then engine continued to run perfectly smooth  
in spite of the two high EGT's.  The mystery was (and still is) that  
the high EGT's were NOT the pairing that one would expect (1&2, 3&4,  
or 5&6), but were some other two.  I expected at the time that I had  
simply wired the EGT's wrong, but that was not the case.  I was about  
15 minutes away and about halfway there all EGT's jumped up about 100  
degrees and were now very even.  The engine continued to run on the  
mag without problem.  Turns out that one of the power devices fried  
and that blew the fuse at the battery.  Why it took 10 minutes to do  
it I don't know, but when I replaced the fuse it popped immediately  
on power-up.

The system, from a reverse-engineering point of view, has some good  
features and some that are not so good.  The circuitry is all analog,  
not so good from a features point of view, but at least free from  
software bugs (no software).  And exotic features aren't particularly  
useful in this application.  The thing I didn't like is that for 6  
cylinder engines both crank triggers are mounted on the same circuit  
board and therefore could suffer from the same failure mode.  The  
most likely, I suppose, is mechanical damage from the crank trigger  
wheel.  The most likely cause of this damage might be an insufficient  
air gap setting that doesn't allow for the crankshaft end play.   
Could the recent failure have occurred when power was brought back to  
idle, moving the crankshaft to the rear?  Another could be damage to  
the wire harness that runs from the trigger.  I built a steel shield  
over the cable and added an abrasion cover besides.

The power source is another potential problem.  I wired my single  
system directly to the (single) battery with an in-line fuse close to  
the battery.  That way everything else could be shut off and the  
ignition system would still be powered.  I retained one magneto and  
that makes the redundancy issue much simpler.  With dual systems I  
would think that at the minimum each system should be run off a  
separate battery and possibly a third standby battery could be added.

Regarding your specific question about the Plasma III on a  
turbocharged engine, the only advantage over mags that I see is  
freedom from distributor arcing and cross-firing at altitude as the  
automatic advance is essentially inoperative at the high cruise  
manifold pressures.  There is also better starting and the ability to  
fire fouled plugs that are in the Plasma III's favor.

Gary Casey
ES - IO-540 Lycoming, one Plasma III and one mag (W/O impulse)


>
> Does anyone have data or anecdotal information on problems with  
> Plasma III
> EI system?  A recent accident in California involving off airport  
> landing of
> a IVP has brought up concerns in my mind.  I have a Performance  
> Engines TSIO
> 550 with the Plasma III ignition (not flying yet) and so did the  
> referenced
> aircraft.  I am told that the cause of the accident was sudden engine
> stoppage and evidence points to failure of one of the redundant EI  
> systems,
> the failure of which may have brought on the failure of the second.
>
> I'd like to know if anyone has data on the Plasma III.  I'm also  
> interested
> in anecdotal accounts positive or negative that might help allay  
> concerns or
> lead to solutions of problems with the system.
>
> Has anyone used a single Plasma III and a magneto backup with a  
> TSIO 550?
>
> Regards,
>
> John Barrett, CEO
> Leading Edge Composites
> PO Box 428
> Port Hadlock, WA 98339
> www.carbinge.com
>