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Dual electronic ignition vs. Single + Magneto

kaweeka

Well Known Member
What are your thoughts on an engine with dual electronic ignition vs. one that has both the electronic and magneto? How about if the aircraft has a battery backup? Safety vs. efficiency?
 
I and a buddy went through the same decision on our two aircraft, both still under build so I can't give you operational anecdotes.

I decided to go all EIs. Better fuel efficiency and operation, two guys in our flying club SacRVators had the same dual Lightspeed setup with no problems, I don't care much for the reliability of electromechanical devices. I have a standby alternator and a VP-200 gizmo from Vertical Power which can detect a failure of the main alternator and switch to standby alternator in a moment. The EIs are not wired through the VP-200, they are fused and switched directly to the aircraft battery. I may yet install a purpose-backup-battery just for the EIs.

My buddy went with 1 Lightspeed and 1 mag. His approach is a little less leading edge risk, a little more known devices. For instance I went with fuel injection, he's using a carburetor.

I don't criticize his decision, and I think we're both safe and comfortable with the way we each went. I probably wouldn't have gone dual EIs 10-15 years ago, but in 2014 when I made the decision I thought they had plenty of safe operational experience to go that way.

One thing that comes up with all the gizmotronic stuff is, what if it fails and you need to repair it in Podunk, Nowhere? A mechanic could repair mags, round gages, etc. True, but I can have a replacement part FedEx'ed overnight and replace the failed gizmo myself.

Another thing I hope to do to mitigate risk of critical failure is run an iPad with XAvion, which is always calculating the best/nearest airport to fly to in case of engine failure...it also lets you know of no available airport. Our RVs can fly high enough, I'm guessing, to almost always have an airport within gliding distance, with perhaps the exception of the inter-mountain west.
 
I'm a little bit of a traditionalist on these things, especially for my age. I really like the pmag concept because it can power itself. I also hear that most of the benefit from electronic comes with the first one. There is something really comforting about flying behind something that is known to be very dependable.

Service in the field is also very nice.
 
I had originally planned on a single EFII and a single mag because I didn't want to make a reduntant electrical system just to power my Electronic Ignition. As I started thinking about the backup power options for my EFIS, the SD8 aux alternator made the most sense for flying, maintenance and cost. Since I now had 8 amps of backup power for as long as my engine is running I decided to use the Dual EFII system.

After selling my existing mag cost difference was minimal and so far the installation/maintence has been easier than a mag. My dual mag engine required a "nonstandard" single mag that helped sway my opinion as well.

If the airplane is already flying with mags and doesn't have a redundant electrical system, I think the single EI makes the most sense. If you're building the electrical and the airplane and want EI I think the redundant electrical system and dual EI makes the most sense.
 
Electrical diagram

I had originally planned on a single EFII and a single mag because I didn't want to make a reduntant electrical system just to power my Electronic Ignition. As I started thinking about the backup power options for my EFIS, the SD8 aux alternator made the most sense for flying, maintenance and cost. Since I now had 8 amps of backup power for as long as my engine is running I decided to use the Dual EFII system.

After selling my existing mag cost difference was minimal and so far the installation/maintence has been easier than a mag. My dual mag engine required a "nonstandard" single mag that helped sway my opinion as well.

If the airplane is already flying with mags and doesn't have a redundant electrical system, I think the single EI makes the most sense. If you're building the electrical and the airplane and want EI I think the redundant electrical system and dual EI makes the most sense.

I'm planned for the full EFII system, ignition and fuel. If you used one of the Nuckell's diagrams would you share the one you chose. I plan to use the SD8 or SD20 depending on the requirements.
 
If you research amateur built accidents, you will find that there are a lot of them related to ignition system failures because of dependence on aircraft electrical power (a lot of them in RV's even). Many appeared to have an electrical system design that should have prevented it but it happened anyway.
I know that a lot of people design systems with back-up power sources, etc., and that helps, but it also induces a much higher level of system complexity and many more failure points that IMO quickly dissolve the simplicity benefits of an electronic ignition.
Another consideration is being stranded somewhere with dead batterys.

Other than using 2 Pmags, I would personally never design a system that didn't have at least one traditional magneto. It requires zero intervention from the pilot to keep the engine running in case of electrical system or electronic ignition failure, and you wouldn't be stranded in the boonies if all battery power was dead.
 
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G3i system?

What about the G3i system. IIRC the "failure" mode is to revert to normal magneto operation.

Any user reports out there?
 
Dual batteries

Z13/8 Aeroelectric
Thanks for the reply! Z13/8 and Z14 have advantages. Z14 seems like a bit of overkill for my mission. I may even use the Buss Manager by Robert, I need to see which diagram it most closely represents. I have time to ponder the subject.

I agree with the sentiments of some about reliability. 10 to 15 years ago I would not have considered EI. Progress has been and continues to be made. In the Aeroelectric Connection the author gives many examples of how certified and accepted systems could be, should be, and yet are not improved. I have been involved in two failures on certified equipment that each manufacturer said were impossible! Well.... I disagree;).

I say get as informed as you can, build as best you can, maintain as best you can, and finally leave yourself as many outs as you can while flying.

Designing the electrical/ignition system is no more stressful for me than thinking that my young son and I pounded all those rivets and we will be at 10,000 ft. :)
 
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I went with a Slick mag on the left and Lightspeed EI on the right, the primary driver being reliability. After almost 200 hrs, I wouldn't have it any other way. The bigger spark of the Lightspeed makes for more efficient burning, and the mag is always there regardless of Lightspeed status. I like the peace of mind AND the combustion efficiency. :)
 
Mags fail. I've experienced this.

Mags need recurring expensive maintenance. I've experienced this.

They require expensive harnesses and plugs unless you're willing to experiment with auto wires and plugs.

Unless you have an impulse coupled (these break, too) mag, it does no good for starting.

Mags are just weight you're hauling around if one ignition is EI.

You have an airplane with two different ignition systems, more spares required, more tools required, etc. Not good maintenance practice.

If EI is so worrisomely fallible, why are you installing even one?

I use P-mags because they're easy to install with few connections (failure points), are self-powered, you can hand-prop long after ship's battery can't crank, more efficient advance-able spark, zero maintenance, cheap harness and plugs, and I believe E-mag has evolved way past their teething issues.

Ya pays ya money and takes ya choice.

John Siebold
 
No reason not to go with dual EI's. Mags are designed to fail at some point, EI's are not. What good is having one mag and one EI when you are stranded somewhere because your mag died. At that point you'll wish you had dual EI's. I rarely hear about EI failures other than some teething pains EMag went through in their earlier units. In the long run EI's are less expensive because they use auto plugs which are better and cheaper than aviation plugs and racing quality harnesses that are a fraction of the price of a magneto harnesses then to top it off they don't need to be replaced every 500 hours. With Lightspeed which is connected directly to the battery you only need 5 volts to run the ingition so when everything else is dead in the plane your engine will still be running. PMags only need I believe 250rpm's, basically a windmilling prop, to keep the internal alternator running. I can't speak to the others out there but I'm sure they are similar. If you are building a modern airplane with modern avionics why would you want anceint technology inefficiently running your engine?
 
... PMags only need I believe 250rpm's, basically a windmilling prop, to keep the internal alternator running...
It is more like 800 RPM, maybe a little less. Still, this is a wind milling prop.

With two different ignitions, you have really one set of plugs that are lighting the fuel-air charge and the other is sparking on smoke. That is because there will always be a timing difference between dissimilar ignitions.

To my knowledge, no one has provided a good explanation if this is good or bad for an engine. I don't really know and don't pretend to have an answer.

I've been running dual P-mags since 2007 and am a co-developer of the EICommander which is designed to monitor and manage P-mags. Think of it as an engine monitor for your ignition. The combination is unprecedented in the light plane industry and adds a level of safety that is unavailable with any other ignition.
 
With two different ignitions, you have really one set of plugs that are lighting the fuel-air charge and the other is sparking on smoke. That is because there will always be a timing difference between dissimilar ignitions.

I'd have to disagree with that statement. Even if the 2nd system fires the spark 2 degrees later than the other, the combustion event is still just underway and you have a flame front starting at each plug. PCP ideally occurs around 18 to 22 degrees ATDC in most Lycomings, having spark initiated at around 25 BTDC.
 
I'd have to disagree with that statement. Even if the 2nd system fires the spark 2 degrees later than the other, the combustion event is still just underway and you have a flame front starting at each plug. PCP ideally occurs around 18 to 22 degrees ATDC in most Lycomings, having spark initiated at around 25 BTDC.

Yes and no, a parallel valve Lycoming typically has their timing set to 25* BTDC, as you mention; however, electronic ignitions typically fire a 30* BTDC or more while in cruise mode. High power settings, such as takeoffs, typically see that margin narrow as the EI brings their timing close to that 25* mark.

So yes, during take off, they are very close and there is enough of a charge that the flame front is probably ignited in two places.

But no, during high altitude cruise, even though the flame front burns slower, the timing spread between dissimilar ignitions grows and while there might be some fuel-air to ignite and burn on the ignition that fires second, it is inconsequential.

That's why we hear of people gaining about 1 GPH when they install one EI and another 1/2 GPH when they install the second EI. What we don't typically hear is how much of their flying is long distance cruising vs. short flights where they spend more time down low and under higher power/MAP.

I would suspect, but don't know and don't have any proof, is that if someone with dissimilar ignitions flew only maximum duration flights, the single EI GPH savings would probably be greater than 1 GPH and if that same person stayed in the pattern doing touch-and-goes, they probably wouldn't see much difference in fuel burn, when compared to dual traditional mags.
 
I have been flying with one mag and one electronic ignition for over 16 years, on a few different aircraft. Currently I have 850 hours on my rocket with one bendix mag and a light speed EI. The mag has been rebuilt once and the EI has been trouble free after some initial hiccups.
Mag checks rarely show any indication the the mag is doing anything and as such I have tended to treat the mag as just a backup. I have not been good about regular cleaning of the mag driven spark plugs nor have I changed them when one would if they were the primary ignition source.
Over the last year or two I have experienced a bit of roughness, nothing that one could define, but it was there, a mild rumble, almost not there.
After a long flight this past year I was on final when my engine started to run very rough, added power was required to get to the runway in what was quite a strong quartering crosswind. It was an unnerving experience.
I suspected fouled plugs and that is exactly what it was. One of my mag plugs had a grounded. The mechanic, in a gentle way, chided me about using plugs that were almost worn out. I replaced the plugs and the engine ran better then it had for many hours. Thus, I was wrong, the magneto, even though it fires after the electronic ignition, still adds something. Based on how the engine ran after installing the new spark plugs I can say with confidence that the mag has a significant effect on how well a mag/electronic combination works. Or, at the very least, a mag system that is not functioning properly can have a detrimental effect on how the engine operates.
 
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The bigger spark of the Lightspeed makes for more efficient burning...

No, it doesn't. Wider gaps, more energy, and multiple strikes will light mixtures that are further from optimum, or (close cousin) mixtures that are less homogenous...but subsequently, combustion is combustion. Reduced cycle-to-cycle variation may result in more power for a given set of difficult conditions.

Put another way, EI can light mixtures more reliably, but once lit, the flame doesn't care how it got lit.

That's why we hear of people gaining about 1 GPH when they install one EI and another 1/2 GPH when they install the second EI.

I think you mean to say compared to a magneto, EI is allowing a mixture setting one GPH leaner without running rough? That would be a gain of 1GPH if it resulted in the same airspeed as the richer mixture.
 
...
That's why we hear of people gaining about 1 GPH when they install one EI and another 1/2 GPH when they install the second EI.
I think you mean to say compared to a magneto, EI is allowing a mixture setting one GPH leaner without running rough? That would be a gain of 1GPH if it resulted in the same airspeed as the richer mixture.

You are correct!
 
The spark of life...

What are your thoughts on an engine with dual electronic ignition vs. one that has both the electronic and magneto? How about if the aircraft has a battery backup? Safety vs. efficiency?

Kaweeka,
I bought an early Jeff Rose (Electroair) ignition for my RV4 before the internet, VAF or pre-punched RV's existed. Paired with a Mag it made the mag look like what it is, a dinosaur. My RV4's performance increased, fuel burn reduced roughly 1 GPH and efficiency was noted immediately. (smoother) The Slick Mag failed inflight many years ago but I didn't even notice until after I landed and did a quick ignition check on the ground. That same RV4 just clicked over 2000 hours with the original Electroair system. Never missed a beat, automotive plugs and wires used throughout it's life.... 25 years later I still run an Electroair paired with a P-Mag. Very efficient, reliable and better than Mags by design.

There's a reason modern autos have used EI for 30 years...:)

V/R
Smokey
 
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Yes and no, a parallel valve Lycoming typically has their timing set to 25* BTDC, as you mention; however, electronic ignitions typically fire a 30* BTDC or more while in cruise mode. High power settings, such as takeoffs, typically see that margin narrow as the EI brings their timing close to that 25* mark.

So yes, during take off, they are very close and there is enough of a charge that the flame front is probably ignited in two places.

But no, during high altitude cruise, even though the flame front burns slower, the timing spread between dissimilar ignitions grows and while there might be some fuel-air to ignite and burn on the ignition that fires second, it is inconsequential.

That's why we hear of people gaining about 1 GPH when they install one EI and another 1/2 GPH when they install the second EI. What we don't typically hear is how much of their flying is long distance cruising vs. short flights where they spend more time down low and under higher power/MAP.

I would suspect, but don't know and don't have any proof, is that if someone with dissimilar ignitions flew only maximum duration flights, the single EI GPH savings would probably be greater than 1 GPH and if that same person stayed in the pattern doing touch-and-goes, they probably wouldn't see much difference in fuel burn, when compared to dual traditional mags.

My point was about the clipped portion of your statement. Even split timing of 5 degrees means the 2nd ignition is not sparking "on smoke" since combustion isn't even close to complete at TDC, let alone 20 or 25 degrees BTDC. This was well known back in the 1940s where combustion studies using pressure transducers and high speed photography through quartz windows showed what was happening inside the chamber.
 
Another EI + Mag Vote

Here's another plug for single EI with single Mag. I have an original Electroair EI and a standard impulse Slick 4371. I get all the benefits of the EI, LOP, reduced fuel flow, more power, more smoothness ... Plus redundancy of the mag and easy starting with the impulse coupling. I can also start with the EI if needed but typically start on the mag then turn on the EI.

My whole plane is built for safety and redundancy because I fly a lot of IFR/IMC/night cross country. If I lose everything electrical, in the soup, a long ways from a suitable landing spot, I have an engine that will run fine on the mag, battery backed up EFIS that will run a minimum of 4 hours, iPad EFB with every US chart and approach, and a 6+ hour battery backed GPS coupled to the EFIS to get me down through weather in a pinch.

This setup has worked well for me 10+ years and 650+ hours in this plane.

I believe the ignition question is best answered by your typical mission profile ... day/VFR local only drives different considerations than night/IFR cross county, and all the variations in between.

Reggie
 
Lightspeed EI and 1 Slick mag with impulse coupling

One more plug for single EI and single magneto with impulse coupling.

The mag is definitely not dead weight, turn off the mag in cruise and you'll see a slight drop in power output, do the same for take off and notice a significant power reduction.
It is a great set up if you are the type who wants electronic efficiency and old fashioned redundancy.
The same is true for one mechanical fuel pump and electric fuel pump.
Although I am a little annoyed at the SB and inspection frequency of the old fashioned slick mag, I do like the comfort of a self generating spark.

Starting the engine with this set up is like starting a car. I generally use both mag and EI for starting.
With a dead battery you can still hand prop on the impulse coupled magneto.
FWIW: I have considered installing dual lightspeed EI but have some reservations.
 
Another vote for at least one mag.

I personally know someone who received horrific burns as a result of crashing during a forced landing after his engine suddenly quit. It is over a year since the crash and he is still wearing pressure bandages. His passenger was even luckier....he died 3 times in intensive care from his burns and injuries but was resuscitated and is now also on the long road back.

His engine quit suddenly and without any warning when his alternator belt snapped. He had dual LightSpeed EIs with dual crank sensors. But the broken belt ripped out the wiring running from the crank sensors and the engine just stopped dead at low altitude.

He says he thought he had redundancy at every stage of the dual EIs, but now realises he was mistaken. He had dual crank sensors but the timing signals ran back to the control unit through one bundle of wires. When that bundle was severed the engine stopped. The result was catastrophic.

I think this story highlights a fundamental issue about EIs and the Experimental category. Most builders understand how conventional magnetos work but very few really understand how the EIs function. They often think they have redundancy with dual EIs when in fact under certain circumstances they may not. This could be because of shortcomings in the logistics of the EI or it could be because of shortcomings in the logistics of the builder's electrical architecture. Either way, it comes down to the old saying that "you don't know what you don't know".

Early engine failures in flight of RVs with dual Pmags was a case in point. Builders assumed that if one Pmag failed the other would provide redundancy. They did not anticipate that if the timing on one Pmag failed and shifted to a very advanced state it would cause the engine to stop regardless of the health of the second Pmag. The early firing of one set of plugs caused the engine to reach Peak Pressure before TDC thus causing the engine to quit. This type of failure was unknown with standard magnetos.

This is not a critisism of electronic ignition per se. I have Lightspeed ignition on one side and an impulse coupled mag on the other. There is quite a lot to be gained by having EI on one side...but very little to be gained (and a lot of potential downside) by adding a second unit.
 
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Vote for 1 Mag / 1 Light speed

I have one Impulse Coupled Bendix Mag and 1 Lightspeed. Great performance and the Mag is built like a tank so nothing is going to stop that from firing - very happy with combo.:cool:
 
Captain Avgas
The following is my opinion & observation from experience with doing installation work on 34 RV's plus many other aircraft. I feel your comments may not be truly helpful & unbiased to those making a decision on which way to go with ignition systems. Unless we can categorically prove that something doesn't work then it's up to the individual to make up their mind about what to do.

Alternator Belt breaking - if the EI is installed properly the belt should not impact on the wiring harness but it sounds like both systems were harnessed together, I would never do that for just this scenario. Keeping critical systems separate is important IMO.
A note here for those using a crank sensor on IO-540's - the gap between the flywheel & crankcase is fairly small & if the cable is not secured properly against the case you still can fail the EI because the flywheel can rub on the cable - I have seen this happen despite having warned the owner of this possibility.

I wonder how many owners have had belts break without some obvious signs of deterioration beforehand. Alternator belts are cheap but a pita to replace, especially with CSU props.

I'm a conservative guy (particularly when setting up aircraft for IFR) when it comes to systems, choice & reliability & have seen the difficulties some have had when being the early adopters of technology whether it be EI's or Glass. I'm happy for them to do the R & D ;)

Now it's no good talking about past history, of various manufacturers, unless no lessons have been learnt. The 2 or 3 major EI systems available now work otherwise we'd be hearing about it.

Due to my work I consider I'm lucky as I see what works, what doesn't & the limitations of the various boxes. It's interesting to note my vac pump was still going at 2000+ hrs. Did I keep it ? no way, to me it was time to go glass, again my choice.

After 1945 hrs on my plane I installed dual P-Mags. Why ? because I'd heard of the earlier issues but some years had since elapsed & it was apparent that hurdles were overcome so the decision was made & I've done 100 hrs since, it was my choice & my money, if you think my choice is wrong then you pay for it.

The above is just my opinion as stated earlier - hopefully this discussion does not degenerate as to what is best or not, we should all be objective as possible & use real life experience to be helpful to those who do not have the knowledge to make decisions on their own, especially for those who aren't finished building their first plane. Be careful out there :)

Jake J







I personally know someone who received horrific burns as a result of crashing during a forced landing after his engine suddenly quit. It is over a year since the crash and he is still wearing pressure bandages. His passenger was even luckier....he died 3 times in intensive care from his burns and injuries but was resuscitated and is now also on the long road back.

His engine quit suddenly and without any warning when his alternator belt snapped. He had dual LightSpeed EIs with dual crank sensors. But the broken belt ripped out the wiring running from the crank sensors and the engine just stopped dead at low altitude.

He says he thought he had redundancy at every stage of the dual EIs, but now realises he was mistaken. He had dual crank sensors but the timing signals ran back to the control unit through one bundle of wires. When that bundle was severed the engine stopped. The result was catastrophic.

I think this story highlights a fundamental issue about EIs and the Experimental category. Most builders understand how conventional magnetos work but very few really understand how the EIs function. They often think they have redundancy with dual EIs when in fact under certain circumstances they may not. This could be because of shortcomings in the logistics of the EI or it could be because of shortcomings in the logistics of the builder's electrical architecture. Either way, it comes down to the old saying that "you don't know what you don't know".

Early engine failures in flight of RVs with dual Pmags was a case in point. Builders assumed that if one Pmag failed the other would provide redundancy. They did not anticipate that if the timing on one Pmag failed and shifted to a very advanced state it would cause the engine to stop regardless of the health of the second Pmag. The early firing of one set of plugs caused the engine to reach Peak Pressure before TDC thus causing the engine to quit. This type of failure was unknown with standard magnetos.

This is not a critisism of electronic ignition per se. I have Lightspeed ignition on one side and an impulse coupled mag on the other. There is quite a lot to be gained by having EI on one side...but very little to be gained (and a lot of potential downside) by adding a second unit.
 
Here's another plug for single EI with single Mag. I have an original Electroair EI and a standard impulse Slick 4371. I get all the benefits of the EI, LOP, reduced fuel flow, more power, more smoothness ... Plus redundancy of the mag and easy starting with the impulse coupling. I can also start with the EI if needed but typically start on the mag then turn on the EI.

My whole plane is built for safety and redundancy because I fly a lot of IFR/IMC/night cross country. If I lose everything electrical, in the soup, a long ways from a suitable landing spot, I have an engine that will run fine on the mag, battery backed up EFIS that will run a minimum of 4 hours, iPad EFB with every US chart and approach, and a 6+ hour battery backed GPS coupled to the EFIS to get me down through weather in a pinch.

This setup has worked well for me 10+ years and 650+ hours in this plane.

I believe the ignition question is best answered by your typical mission profile ... day/VFR local only drives different considerations than night/IFR cross county, and all the variations in between.

Reggie

The Electroair system is excellent, I had it on my RV4 and loved it but a few points. First, it is connected directly to the battery and second it only needs 8 volts to run so if you loose your alternator you'll still have plenty of voltage to run your system. Running dual Electroairs requires having a second battery. When my mag gave out I dreaded having to replace it with another one and was considering putting a P-Mag on but in the end I found a good deal on a new mag and harness. It really comes down to a comfort level with modern electronics. I seriously doubt Electroair would have recieved numerous STC's for their units if they were not dependable.
 
Captain Avgas
The following is my opinion & observation from experience with doing installation work on 34 RV's plus many other aircraft. I feel your comments may not be truly helpful & unbiased to those making a decision on which way to go with ignition systems. Unless we can categorically prove that something doesn't work then it's up to the individual to make up their mind about what to do.

Alternator Belt breaking - if the EI is installed properly the belt should not impact on the wiring harness but it sounds like both systems were harnessed together, I would never do that for just this scenario. Keeping critical systems separate is important IMO.
A note here for those using a crank sensor on IO-540's - the gap between the flywheel & crankcase is fairly small & if the cable is not secured properly against the case you still can fail the EI because the flywheel can rub on the cable - I have seen this happen despite having warned the owner of this possibility.

I wonder how many owners have had belts break without some obvious signs of deterioration beforehand. Alternator belts are cheap but a pita to replace, especially with CSU props.

I'm a conservative guy (particularly when setting up aircraft for IFR) when it comes to systems, choice & reliability & have seen the difficulties some have had when being the early adopters of technology whether it be EI's or Glass. I'm happy for them to do the R & D ;)

Now it's no good talking about past history, of various manufacturers, unless no lessons have been learnt. The 2 or 3 major EI systems available now work otherwise we'd be hearing about it.

Due to my work I consider I'm lucky as I see what works, what doesn't & the limitations of the various boxes. It's interesting to note my vac pump was still going at 2000+ hrs. Did I keep it ? no way, to me it was time to go glass, again my choice.

After 1945 hrs on my plane I installed dual P-Mags. Why ? because I'd heard of the earlier issues but some years had since elapsed & it was apparent that hurdles were overcome so the decision was made & I've done 100 hrs since, it was my choice & my money, if you think my choice is wrong then you pay for it.

The above is just my opinion as stated earlier - hopefully this discussion does not degenerate as to what is best or not, we should all be objective as possible & use real life experience to be helpful to those who do not have the knowledge to make decisions on their own, especially for those who aren't finished building their first plane. Be careful out there :)

Jake J

I agree with your assesment. There are many other things that can happen to an engine in flight regardless of which ignition system you have that having an engine failure due to dual EI's is trivial. The performance gains, money savings, maintenance savings, and dependablity far outweigh the remote chance of a total iginition system failure.
 
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I personally know someone who received horrific burns as a result of crashing during a forced landing after his engine suddenly quit. It is over a year since the crash and he is still wearing pressure bandages. His passenger was even luckier....he died 3 times in intensive care from his burns and injuries but was resuscitated and is now also on the long road back.

His engine quit suddenly and without any warning when his alternator belt snapped. He had dual LightSpeed EIs with dual crank sensors. But the broken belt ripped out the wiring running from the crank sensors and the engine just stopped dead at low altitude.

He says he thought he had redundancy at every stage of the dual EIs, but now realises he was mistaken. He had dual crank sensors but the timing signals ran back to the control unit through one bundle of wires. When that bundle was severed the engine stopped. The result was catastrophic.

I think this story highlights a fundamental issue about EIs and the Experimental category. Most builders understand how conventional magnetos work but very few really understand how the EIs function. They often think they have redundancy with dual EIs when in fact under certain circumstances they may not. This could be because of shortcomings in the logistics of the EI or it could be because of shortcomings in the logistics of the builder's electrical architecture. Either way, it comes down to the old saying that "you don't know what you don't know".

Early engine failures in flight of RVs with dual Pmags was a case in point. Builders assumed that if one Pmag failed the other would provide redundancy. They did not anticipate that if the timing on one Pmag failed and shifted to a very advanced state it would cause the engine to stop regardless of the health of the second Pmag. The early firing of one set of plugs caused the engine to reach Peak Pressure before TDC thus causing the engine to quit. This type of failure was unknown with standard magnetos.

This is not a critisism of electronic ignition per se. I have Lightspeed ignition on one side and an impulse coupled mag on the other. There is quite a lot to be gained by having EI on one side...but very little to be gained (and a lot of potential downside) by adding a second unit.

This reminds me of United Air Lines Flt 232, the DC-10 that had a simultaneous failure of all 3 redundant hydraulic systems killing 111 persons in the crash. Something that was never supposed to happen. Even though they were completely independent, at one point they were routed very close together and that is where all three hydraulic lines were severed by a catastrophic engine failure.

UAL Flight 232, Sioux City, Iowa

No matter how a human engineers any system, there will always be a possibility of failure. The idea is to make the probability of these failures as low as logical and practical. As builders we decide what level of failure probability versus performance enhancement we are willing to accept knowing we will never be 100% failure proof. Remember, the only aircraft that have a 100% probability of a perfect safety record are those that never fly.

My 2 cents.

:cool:
 
They often think they have redundancy with dual EIs when in fact under certain circumstances they may not. This could be because of shortcomings in the logistics of the EI or it could be because of shortcomings in the logistics of the builder's electrical architecture.

This is not a criticism of electronic ignition per se.

Thank you Bob...a good reminder, and two good examples. I for one never considered impact shielding of crank trigger leads, but I will in the future. It would be easy to do.

As usual, we have a fair bit of proselytizing from all camps, but very little data. One thing I am sure: both mags and EI's fail. I'm happy to hear of every failure mode, as I'm not smart enough to predict all of them myself.
 
Early engine failures in flight of RVs with dual Pmags was a case in point. Builders assumed that if one Pmag failed the other would provide redundancy. They did not anticipate that if the timing on one Pmag failed and shifted to a very advanced state it would cause the engine to stop regardless of the health of the second Pmag. The early firing of one set of plugs caused the engine to reach Peak Pressure before TDC thus causing the engine to quit. This type of failure was unknown with standard magnetos. [/QUOTE said:
A standby mag isn't any help in this scenario if the EI fails.

This is why pilots must know the systems and how to deal with emergencies. These failures occurred on start-up (personal experience with several). Deal with it by shutting off the offending ignition. Isolating which one takes less than two seconds if your switchology is such you can instantly disable one or the other with dedicated grounding switches. Problem is a surprised, bewildered pilot takes many seconds realizing they have a failure of some sort and what to do.

Lots of good comments about thorough systems segregation for true redundancy. Pay attention when cobbling up the electrical architecture and the installation. Inept installation I say is the prime reason for EI problems.

Again the challenge: if EIs are failure-prone, why is even one installed? No one has established that aircraft are raining from the skies due to EI failures. What's the fear?

BTW, when impulse couplings break (and they do), they have a nasty tendency to sling bits of metal into the engine.

John Siebold
 
Survivors

GalinHdz,

I agree on UA232.

The key to that incident was an experienced pilot ingeniously flying and controlling the crash-landing of the plane: 185 survived. It's a remarkable story, nonetheless.
 
"Again the challenge: if EIs are failure-prone, why is even one installed? No one has established that aircraft are raining from the skies due to EI failures. What's the fear?"

Well, I think the fear is more electrical failure than EI-specific failure.

You add a dependency on a system that can itself fail when you use EI (Except the P-mag).

2 systems each with their own likelihood of failure means increased overall probability of failure than the risk of each system independently measured: EI can fail AND electrical can fail.

You'd just have to see whether that probability is still no worst than a mag failure, or whether that increased risk is worth it to you. I mean even if the risk doubles from 0.00001% to 0.00002% (making up numbers here) then many people might still feel quite comfortable with that doubling of risk.

As you suggest though, lots of EI's out there, and there's no great indication that they are troublesome. Is this because there's a lot of people with a mechanical backup (and hence you hear less about it), or because they just don't fail (the EÀI, or the electrical) any more often than mags?

Seems to me anything solid-state is likely to be more reliable than anything mechanical ...
 
85% performance gain with one EI

I have gone with one PMAG and one Slick for safety reason.

I know of two friends with two EI who believed had a full electrical redundancy with two batteries and separate busses only as a result of an engine out, to find out that their logic in the setup wasn?t exactly right. One of the engine out was on a takeoff, roughly at 300? AGL and the other higher up. Luckily there was no human injury with either case and since they have re-worked their electrical system.
 
Bob's post about crank sensor cable routing/ protection is a good one.

We had a V6 installation where the builder fitted a non-standard aluminum stack exhaust system which predictably came apart in flight, allowing exhaust gases to melt through the crank sensors wires, shutting down the engine, successful gear up, forced landing with no injuries.

Now the sensor cables are supplied with fire sleeve over the first 3 feet in case anyone else does such a bonehead thing again...
 
I have gone with one PMAG and one Slick for safety reason.

I know of two friends with two EI who believed had a full electrical redundancy with two batteries and separate busses only as a result of an engine out, to find out that their logic in the setup wasn?t exactly right. One of the engine out was on a takeoff, roughly at 300? AGL and the other higher up. Luckily there was no human injury with either case and since they have re-worked their electrical system.

Not a fault of the EI's here. As Klaus at Lightspeed would scream, wire per the plans supplied! The electrical system is science not art.
 
Captain Avgas
I feel your comments may not be truly helpful & unbiased to those making a decision on which way to go with ignition systems.

After 1945 hrs on my plane I installed dual P-Mags. Why ? because I'd heard of the earlier issues but some years had since elapsed & it was apparent that hurdles were overcome so the decision was made & I've done 100 hrs since, it was my choice & my money, if you think my choice is wrong then you pay for it.

Jake J

Jake, I think it is possibly a little bit hypocritical of you to be accusing me of being biased in this matter when it is known that you are making money on a commercial basis out of selling and installing PMAG EI systems. I really do think that it would have been appropriate for you to mention this in your post.

You might also have more credibility if you posted under your full name.

Now let me get this right. You had 1945 hours of flying, presumably with at least one magneto, and you're still alive. Now you have 100 hours with dual PMags and you're advising everybody to follow suit. Hmmmm. :rolleyes:
 
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Not a fault of the EI's here. As Klaus at Lightspeed would scream, wire per the plans supplied! The electrical system is science not art.

Agreed, but I just wanted to point out that our redundant system, if deviated from original plan, need to be test it under all designed scenarios to make sure it does what you designed it for. Dual EI certainly falls within that catagory.
 
Choosing or not EI

Jake, I think it is possibly a little bit hypocritical of you to be accusing me of being biased in this matter when it is known that you are making money on a commercial basis out of selling and installing PMAG EI systems. I really do think that it would have been appropriate for you to mention this in your post.

You might also have more credibility if you posted under your full name.

Now let me get this right. You had 1945 hours of flying, presumably with at least one magneto, and you're still alive. Now you have 100 hours with dual PMags and you're advising everybody to follow suit. Hmmmm.

Cheap shot Bob :p

My main source of income is doing installations & giving customers good (hopefully) advice - you are totally out of line here as I install either what the customer purchases or what I buy for them. Also I'm not a Dealer or distributer etc for PMAG, my point was that I have seen them over the last several years evolve into a EI system that I'm happy to use.
Maybe I'm not as articulate as you & therefore am unable to get my point across as well however I never "advised everybody to follow suit", those are your words.
I thought this Forum was meant to assist others make decisions based on the flying, building & systems experiences - this sort of dissent just puts people off sharing their knowledge IMO.
My reason for not publishing my full name or contact details is because I don't want to be accused of soliciting for work. Maybe the fact that I don't advertise is a clue for you.
I had hoped my unbiased reasoning about my use of EI would be helpful to someone, silly me.
So now, once again Bob you leave me no choice but to leave this Forum the same as I did to another one you are on. Goodbye, you have the floor :)
 
Also I'm not a Dealer or distributer etc for PMAG, my point was that I have seen them over the last several years evolve into a EI system that I'm happy to use.

Jake, If you purchase PMAGs from Emagair (which you do) and then onsell them to other parties at a profit (which you do) and then make additional profit installing the PMAG (which you do) then you're a dealer....maybe a small time dealer, but a dealer non-the-less. As such you have a pecuniary interest in promoting the product that should have been disclosed in your original post.

You may genuinely believe that the PMAG is the best ignition system going around, but that is not the point. The point is that if you are selling the system (if there are dollars involved) then you need to say so in order that VansAirforce readers can give appropriate weighting to your opinions.
 
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Jake, If you purchase PMAGs from Emagair (which you do) and then onsell them to other parties at a profit (which you do) and then make additional profit installing the PMAG (which you do) then you're a dealer....maybe a small time occasional dealer, but a dealer non-the-less. As such you have a pecuniary interest in promoting the product that should have been disclosed in your original post.

You may genuinely believe that the PMAG is the best ignition system going around, but that is not the point. The point is that if you are selling the system (if there are dollars involved) then you need to say so in order that VansAirforce readers can give appropriate weighting to your opinions.

Bob,
Although I understand your point I'm not sure I agree. I freely offer my "opinion" or "my 2c" on the forums on equipment I install on customers aircraft, which I make a modest living from. In many ways I think this gives me/us an insight that others may find helpful and that opinion shouldn't necessarily be disqualified because we are in the business. My goal, and I assume Jakes, is to simply offer some additional feedback based on our experience that readers may find helpful when making a purchasing decision.

I might add that the miniscule margins that "we dealers" make from the accessories we sell is almost meaningless, the only place I make any money at all is installation, not sales! (we're not in the used car business). My goal is reliable products, that is what makes customers happy and keeps them safe and coming back. How long do you think I would keep selling a product that failed regularly which I had to keep repairing under warranty? (most vendors don't cover labor in their warranties)
 
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I went with the single Slick mag/single Lightspeed setup, which worked great until the Slick failed at around 850 hours (detected on run-up check). This was the second mag failure I've experienced (the first in a club plane), versus 0 in 900+ hours with the Lightspeed. I ended up replacing the mag with a second Lightspeed and a backup battery.

Part of my rational was that the engine runs more smoothly on a single Lightspeed than it does on a single mag. The principal operational drawback to dual electronic ignition is that alternator failure requires landing as soon as possible. However the same is true with a mixed mag/EI system. Ithe alternator fails you need to land, unless you are willing to sacrifice the redundancy of two functioning ignitions.
 
I appreciate the comments made by two posters about a timing failure on EI that could shut down an engine. I slowly evolved from one Lightspeed and a Slick, to the LS and a P Mag.
It has always been in my emergency checklist to try running on one mag if the engine stops or runs rough. This thread has been valuable, notwithstanding the bickering between two members...
Checking the wire runs and other potential danger zones is all good knowledge. Remembering to isolate and verify, when trouble strikes... may just save a life, an airframe or both. Thanks to all who joined in.
 
LS plus Slick

I have been running a LS Plasma III for the top plugs (auto plugs) and a Slick mag for the bottom plugs (Tempest) since 2006. The LS has never faltered but the Slick has failed twice!! I am considering the set up that Nick has---one LS and one P Mag. The complications of installing a second LS on a completed aircraft and the need for a seperate back up battery is the primary reason for not going with two Plasma III's. Far easier to install the control box and the backup battery for the second LS if the aircraft were under construction--and if I were building that is probably the way I would go--given the reliability of the LS!

Nick you will be receiving an email or visit!!

Cheers,

db
 
(we're not in the used car business). My goal is reliable products, that is what makes customers happy and keeps them safe and coming back.

Gosh, sounds remarkably similar to a successful used car business ;)
 
I appreciate the comments made by two posters about a timing failure on EI that could shut down an engine. I slowly evolved from one Lightspeed and a Slick, to the LS and a P Mag.
It has always been in my emergency checklist to try running on one mag if the engine stops or runs ou. ...

if you are running dissimilar ignitions, and one is a P-mag, make sure the P-mag is at revision 40 or higher! There is a chance, however slight, that the P-mag could have its TDC mark changed when starting on just the LS (or other ignition of any type).

Contact Emag for details.

This upgrade also delays firing the plugs until 4 degrees past TDC for easier starting and eliminates the need to "clock" the ignition when using a lightweight prop.
 
Does anyone know why PMags for 6 cyls is not available? It just seems like with all the success with 4 cyl engines, a 6 cyl version would be a given???
 
I have been running a LS Plasma III for the top plugs (auto plugs) and a Slick mag for the bottom plugs (Tempest) since 2006. The LS has never faltered but the Slick has failed twice!!

Which brings up a good point. The general perception is that Slicks are, umm, less than wonderful, and that a Bendix mag is better. Trouble is, most of Bendix units out there are old or overhauled, not new.

For those who did not get the memo, Continental announced competitive pricing at the last OSH...

http://www.continentalmotors.aero/uploadedfiles/content/ximages/magneto13_webimage-web.pdf

....and a new "Bendix" mag may offer the sort of reliability many seek with a mag/EI setup.
 
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Thanks Bill, for the heads up.
Now for a story.... I left the master switch on in San Diego last week.
Ran the Odyssey PC680 down flatter than a pancake.
Got the FBO to jump me with the electro tug... and ran the engine for 15 minutes to see how the alternator and Odyssey were going to get along.
The voltage was jumping from around 13 to 15 back and forth. Not a good sign. After 15 minutes, I turned the mag switch off. Then the Lycoming sputtered and began to run BACKWARDS. That gets your attention.
Pulled the breakers for both EI systems... and it got quiet.
The Odyssey is toast, as the Aussies like to say.
The only battery I could find near Montgomery Field was a Power Sonic 21 AH with the same dimensions. Flew home in the dark with flashlights at the ready. Since Odyssey says any battery run down below 8 VDC is not covered... my 11 month investment with them goes in the recycle bin.
The Power Sonic will stay for a while and do it's duty...
Cheers
 
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