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.
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.Z13/8 Aeroelectric
It is more like 800 RPM, maybe a little less. Still, this is a wind milling prop.... PMags only need I believe 250rpm's, basically a windmilling prop, to keep the internal alternator running...
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.
The bigger spark of the Lightspeed makes for more efficient burning...
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.
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?
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 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
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.
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.
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
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.
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
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.
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 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.
(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.
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. ...
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!!