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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
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