Lightspeed Plasma III problem

[Captain Avgas]

Originally Posted by Lars

Can you defend that first statement with facts? Not just anecdotes gleaned from the internet. As for the second statement, those are pretty harsh words.

The anecdotal evidence would suggest that both the Plasma 11 and Plasma 111 are very reliable units and either should provide good service. And properly set up both should offer better reliability than a magneto.

However, by the very nature of its longer duration spark, the Plasma 111 will erode spark plugs faster and place higher stresses on both the high tension wires and coils. In simple terms that means the Plasma 111 will exhibit a decreased MTBF (mean time between failure) compared to the Plasma 11.

Anybody in any doubt on this issue can always refer to the manufacturer. Apart from that, it's logical. The spark plugs, high tension wires, and coils are the same devices in both ignition systems but in the Plasma 111 they're working harder.

It's a bit like opting for high compression pistons on a Lycoming. You get a slight boost in performance but you place an additional stress on the engine that can reduce longevity. In other words there is a small trade in terms of opting for performance as against reliability (or longevity as the case may be).

It's obviously the same for the Lightspeed ignitions. It's a personal decision. It just depends where your priority lies.....a small gain in performance vs a small gain in reliability (whether in fact the Plasma 111 with it's longer duration spark actually provides any real world measurable improvement in performance over the Plasma 11 is perhaps debatable....but that's another story).

I stated that some builders opt for a Plasma 111 over a Plasma 11 purely because they assume the larger number is synonymous with "better". I don't think that is being harsh...it's just a statement of fact and I'm sure that many purchasers of the Plasma 111 would concur.

[breister]

I think the question was fair - if only for my own information I for one would like to see info on what real-world measurements might have been done to evaluate "degradation" in coils, wires, plugs. If not directly on the Lightspeed units, then on similar spark systems.

It might cause me to replace some of these items as "preventive maintenence" at some point.

[Captain Avgas]

Originally Posted by breister

I think the question was fair - if only for my own information I for one would like to see info on what real-world measurements might have been done to evaluate "degradation" in coils, wires, plugs. If not directly on the Lightspeed units, then on similar spark systems.

It might cause me to replace some of these items as "preventive maintenence" at some point.

The typical failure scenario between a "mechanical" ignition (ie. a magneto) and a "solid state" ignition (eg. LightSpeed) is different. Magnetos are most reliable when new....but that is when solid state devices are most failure prone (on a mature electronic device up to 90% of failures occur in the first 10% of time in operation).

In other words it might be said that your magneto, if you have one, is becoming LESS reliable with time....but your LS Plasma 111 is becoming MORE reliable with the passing of flight hours (but is still not as reliable as a Plasma 11)

[Lars]

Originally Posted by Captain Avgas

The anecdotal evidence would suggest that both the Plasma 11 and Plasma 111 are very reliable units and either should provide good service. And properly set up both should offer better reliability than a magneto.

However, by the very nature of its longer duration spark, the Plasma 111 will erode spark plugs faster and place higher stresses on both the high tension wires and coils. In simple terms that means the Plasma 111 will exhibit a decreased MTBF (mean time between failure) compared to the Plasma 11.

Anybody in any doubt on this issue can always refer to the manufacturer. Apart from that, it's logical. The spark plugs, high tension wires, and coils are the same devices in both ignition systems but in the Plasma 111 they're working harder.

It's a bit like opting for high compression pistons on a Lycoming. You get a slight boost in performance but you place an additional stress on the engine that can reduce longevity. In other words there is a small trade in terms of opting for performance as against reliability (or longevity as the case may be).

It's obviously the same for the Lightspeed ignitions. It's a personal decision. It just depends where your priority lies.....a small gain in performance vs a small gain in reliability (whether in fact the Plasma 111 with it's longer duration spark actually provides any real world measurable improvement in performance over the Plasma 11 is perhaps debatable....but that's another story).

I stated that some builders opt for a Plasma 111 over a Plasma 11 purely because they assume the larger number is synonymous with "better". I don't think that is being harsh...it's just a statement of fact and I'm sure that many purchasers of the Plasma 111 would concur.

Fair enough... but if the MTBF of a III is, say, less than 10% below than the II, then while it may be statistically significant, it's probably operationally irrelevant. Especially if the MTBF is up past 1000 hours somewhere. If the MTBF of the II is something like double that of the III, then there would be obviously be more of a cost/benefit argument from an economy vs. reliability perspective. On the other hand, if the MTBF of either is much beyond the engine TBO, then it's probably all irrelevant. Pick the system you like and run it.

Funny- when I asked Klaus Savier to contrast the two systems at Oskosh in 2006, he didn't mention durability or MTBF. But it's not like he had hours of time to talk that day. In any case, I haven't flown with either system, and it sounds like you may have, so I'll defer to you as regards field experience.

My experience is mostly with late model automotive and motorcycle ignition systems (in the latter case my BMW motorcycle has an ignition coil that appears outwardly to be practically identical to the coils sold with the Lightspeed setups) where ignition parts, despite being far more stressed than the automotive & motorcycle systems of 40 years ago, last an insanely long time. I've personally dabbled with auto engine control system mods that imposed heat stresses far beyond stock, and the OEM stuff I'm using still keeps ticking. Amazing.

I still maintain that the tenor of your original reply was calculated more to inflame than to inform. But that's just me...

[Lars]

Originally Posted by Captain Avgas

The typical failure scenario between a "mechanical" ignition (ie. a magneto) and a "solid state" ignition (eg. LightSpeed) is different. Magnetos are most reliable when new....but that is when solid state devices are most failure prone (on a mature electronic device up to 90% of failures occur in the first 10% of time in operation).

In other words it might be said that your magneto, if you have one, is becoming LESS reliable with time....but your LS Plasma 111 is becoming MORE reliable with the passing of flight hours (but is still not as reliable as a Plasma 11)

The high-time Lightspeed failures I've heard of were all coil-related. No fun to lose an ignition in any case, but much easier to carry/replace an ignition coil. My hangar partner just installed dual III's. By the time I'm ready to make a decision I'll have at least one more experiential data point.

[Captain Avgas]

Originally Posted by Lars

Funny- when I asked Klaus Savier to contrast the two systems at Oskosh in 2006, he didn't mention durability or MTBF.

I have always found Klaus to be very honest and candid on technical issues. Perhaps you didn't ask him the right questions.

[airguy]

Originally Posted by Captain Avgas

I have always found Klaus to be very honest and candid on technical issues. Perhaps you didn't ask him the right questions.

Or perhaps, since he's so honest and candid, there was not an issue to disclose?

[Captain Avgas]

Originally Posted by airguy

Or perhaps, since he's so honest and candid, there was not an issue to disclose?

Well, sometimes buyers are so excited about the advertised size of the the donut that they fail to enquire about the size of the hole.

So there is no confusion and I am not misinterpreted, these are my specific statements:

a) The Plasma 11 and 111 are both reliable products. There is no suggestion that either product has an "issue" or "fault".

b) However the Plasma 111 is a less mature product than the Plasma 11.

c) The Plasma 111 has a longer duration spark that will tend to erode spark plugs faster and place higher stresses on high tension wires and ignition coils.

d) As a result of b) and c) one would be better opting for the Plasma 11 over the Plasma 111 if absolute reliability is the sole criterion for the ignition choice.

And I'm absolutely confident that if you bother to ask the people in the industry who know, the people who are supplying and fitting hundreds of these devices, they will tell you exactly the same thing.

So don't take my word for it....go straight to the source and ask Klaus. Or go and ask Bart at AeroSport Power for a truly independent opinion.

[airguy]

Originally Posted by Captain Avgas

Well, sometimes buyers are so excited about the advertised size of the the donut that they fail to enquire about the size of the hole.

So there is no confusion and I am not misinterpreted, these are my specific statements:

a) The Plasma 11 and 111 are both reliable products. There is no suggestion that either product has an "issue" or "fault".

b) However the Plasma 111 is a less mature product than the Plasma 11.

c) The Plasma 111 has a longer duration spark that will tend to erode spark plugs faster and place higher stresses on high tension wires and ignition coils.

d) As a result of b) and c) one would be better opting for the Plasma 11 over the Plasma 111 if absolute reliability is the sole criterion for the ignition choice.

And I'm absolutely confident that if you bother to ask the people in the industry who know, the people who are supplying and fitting hundreds of these devices, they will tell you exactly the same thing.

So don't take my word for it....go straight to the source and ask Klaus. Or go and ask Bart at AeroSport Power for a truly independent opinion.

In the interest of full disclosure, but full logic, I make the statement that I am neither a buyer (nor operator) of either system, nor do I have any association with the company or product in question.

However (comma)

a) - agreed - there is no evidence that either product is at fault.

b) - This is irrelevant, unless you are strictly looking for a "time in service" grade. In that case, the dinosaurs win, hands down. But have they succeeded?

c) - I can see (and concede) your point on the spark plugs, but this will have no effect whatsoever on the coils or the wires until (and unless) the current flow exceeds the point at which resistance heating overcomes passive heat loss, which has not (to date) been shown to be a factor.

d) - as a result of b) and c) above, is not factually true.

Please note that I am not cheerleading for ANY type of device or manufacturer, merely for physics and facts. Let's keep it real.

[Captain Avgas]

Originally Posted by airguy

c) - I can see (and concede) your point on the spark plugs, but this will have no effect whatsoever on the coils or the wires until (and unless) the current flow exceeds the point at which resistance heating overcomes passive heat loss, which has not (to date) been shown to be a factor.

You are totally incorrect on this. Where are you getting your information from? The failure rate on the Plasma 111 units, including failed ignition coils, is higher than on the Plasma 11 units. LightSpeed themselves acknowledge this fact (if you bother to ask them...which I did).

I also had extensive discussions on this specific subject with one of the most respected (and largest) Experimental engine builders in the market place (a company that has installed literally hundreds of these units) and they confirmed the same information.

So here you have the manufacturer, and major installers, saying the same thing. If reliability is your prime objective then the Plasma 11 is the unit of choice.

For the life of me I cannot understand why people continue to shoot from the lip on this topic without even consulting the manufacturer to get their facts straight.