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Dual electronic ignition vs. Single + Magneto

N941WR said:
I keep hearing this, yet no one has opened up their P-mag to check the heat range spec's on the components within the units.
I don't know of one documented heat related failure.
Click to expand...

So what is the deal with the temperature tell-tale stickers? 200F, yes?

LifeofReiley said:
BTW, the temp sensor on the EI box never exceeds 106F degrees behind the engine plenum flying.
Click to expand...

Which merely indicates that your installation has rather poor heat transfer from engine to air, or a lot of cooling air leakage. It's entirely possible to exceed 200F air temperature in the lower/rear cowl volume.

Operating with the cowl exit wide open (maximum mass flow) last June, I was measuring 165F air temperature in the upper firewall area at cruise speed, and 185F in slow flight. I have recorded exit temperatures as high as 228F with high power, low speed, and exit closed for minimum mass flow.
 
Heck my under cowl temps can exceed 106F in the Texas summer without the engine even running!
 
Yes Walt, on the ground the temps do get warm with the engine off, even more so after shut down. My stated temp was in flying mode... Cruise. CHT's @ 290F, Oil Temp @ 165F, and we do not have any cooling leaks to speak of with our plenum. You never can get them all. YMMV. The box is cooled with a tube.
 
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Been following this thread with great interest. I run an Electroair plus a Slick on my Lycon 10:1 IO-540. Brains are on the cold side of the FW, and MAP sensor is on the hot side (high on the right side of the FW). I've been very pleased with the engine performance, both in terms of everyday operations, including LOP cruise, as well as racing. I do like the mag backup, as I live in Reno, and cross big rocks often. However, I do know many racing friends that run dual EIs of various types, and don't have a fundamental or parochial issue with those set-ups either. Obviously there are precautions and back-ups required, and as long as a user goes into the build informed, educated and eyes wide open, it appears to me to be a workable solution.

Dual EIs in the racing environment appear to be fairly dependable, though as racers tweak things to get max performance, it takes effort to control temps. Failures or temp issues often seem to be installation or management issues, though there have been occasional box failures. I don't have numbers, but I had a brain-box failure of a very early and aging LSE PI. LSE and EA appear to put our reliable equipment, and my EA has been flawless. We did have a mayday and successful dead stick on-aiport landing in the Reno Sport Class last year (Lancair Legacy), but it was due to both EI rev limiters cutting ignition, and shutting off the motor. Relight was unsuccessful because ADI was still on, and the fire could not be lit. Lesson learned there, and it was not an EI issue, but a procedural one?and it should not impact normal (non-race) operators,

So all that being said to set an unbiased tone here?as a guy who wants to extract maximum performance from his motor, yet maintain adequate safety margins in the mountains, is there solid data to show the added performance gain (HP on one end and efficiency on the other) of adding a second EI? I've heard many claims of X percentage gain for 1 EI, and X+ percentage gain for adding a second. Does anyone have actual test data that shows real-world racing or cruise figures? Not MFGR claims, but good, solid field testing. Not saying its not out there, I'd just love to see what folks are really getting from a dual EI set up as I evaluate all performance enhancing options.

Cheers,
Bob
 
DanH said:
So what is the deal with the temperature tell-tale stickers? 200F, yes?

....
Click to expand...
I guess it is like people setting their CHT limits at 400 even though Lycoming states 435* F.

I'll check with Emag this week, when I call them and report back.
 
N941WR said:
I'll check with Emag this week, when I call them and report back.
Click to expand...

Excellent.

This was the temperature specification at Toyota, circa 1999


[5] M. Hattori (Toyota Motor Corporation, IC Design and Evaluation Department):
"Needs and Applications of High-Temperature LSIs for Automotive Electronic Systems"
HITEN High-Temperature Electronics Conf, 1999, pp. 37-4

Circa 2004, the DaimlerChrysler spec for on-engine electronics was -40C to 165C. Table V (below) was their future requirement at that time:

[6] R. W. Johnson, J. L. Evans, P. Jacobsen, and R. Thompson:
"High-Temperature Automotive Electronics”
Int. Conf. Advanced Packaging and Systems, 2002, pp. 77–87.

Considering that the engine electronics in a 10 year old minivan design were required to withstand 325F, and those reliable 1999 Toyotas were good to 350F....

BTW, old car guys will remember the early days of solid state ignitions. For example, I bought lots of in-distributor ignition modules for mid-80's Nissan Sentra (Hitachi IIRC). They usually died at a stoplight in the scorching southern summertime, when they got nice and hot. The customers all thought I was a good guy, because if they had purchased the car recently, I would pay their tow bill and install a new module at no charge. Sound familiar?
 
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rvmills said:
Does anyone have actual test data that shows real-world racing or cruise figures?
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Bob,

I replaced my Slick with a second Lightspeed recently. Can't say I've noticed a change in performance, but I haven't done a careful test or raced with this setup yet. My expectation is that any change is going to fall within the range of measurement error (which in my experience is ?1-2 its).
 
LifeofReiley said:
BTW, the temp sensor on the EI box never exceeds 106F degrees behind the engine plenum flying.
Click to expand...

Wow, simply impressive ?. My temp strip on PMAG is at 185 or maybe even 190 and I consider my engine to run cool and will keep the oil door open any time landing and shutting down.
 
Some of the above comments imply that magneto failure is less likely to cause an accident than failure of an electronic ignition. This may be statistically true (or not), but mag failures have certainly been known to bring down airplanes. Below are excerpts from a a few such occurrences reported in the NTSB database, that involve both single and dual magneto failures.

One possible conclusion based on these reports is that poor installation, maintenance, or operation can cause problems with either type of ignition.

From NTSB (underlining added):

(ERA14CA191) ?Examination of the airplane's engine by an FAA airworthiness inspector revealed that both magnetos were improperly grounded at installation. The installation as found resulted in a degraded performance, and over time, resulted in a complete ignition failure and total loss of engine power.?

(CEN11FA115) ?A postaccident examination of the engine revealed a piece of engine isolator gasket had become wrapped around the carburetor main fuel jet and both magnetos distribution gear had cracked and were missing teeth. The damaged distribution gear teeth were consistent with damage found after an engine experiences a backfire. It could not be determined which magneto failed first or if they both failed simultaneously. The cause of the backfire could not be determined. Further examination of the engine, airframe, and remaining systems revealed no anomalies that would have precluded normal operation.?

(LAX05LA057) ?Soon after the course reversal, the pilot noted an engine sound decrease and loss of engine rpm. As he reached the edge of the high desert, the engine shutdown abruptly. He turned toward a nearby airport, and observed a popped circuit breaker for the electronic ignition system. He reset the breaker and the engine went to full power for about 5 or 10 seconds, and then the breaker popped again. He turned off the electronic ignition system to check the redundancy of the left magneto, which was also inoperative. The pilot reported that during the course reversal while in the rain showers, he observed rainwater entering the cockpit and instrument panel area around the magneto switches and electronic ignition circuit breaker. He felt that the source of the ignition failure was due to the shorting of the magneto switch from the rainwater.?

(LAX96LA167) ?The airplane was subsequently examined, and the following discrepancies were found: (1) Sediment was observed in the fuel filter and carburetor; (2) The number 3 cylinder intake valve was found open and stretched in excess of 0.200 inches; (3) No compression was obtained from the number 3 cylinder; (4) The engine oil was black in color; (5) The magneto's drive end seal bearing was found leaking oil; (6) The left set of points were oil fouled, and the right set of points had oil on the contacts and were coked up; and (7) The left distributor gear was missing a gear tooth.?

(ATL97LA009) ?During the climb after takeoff, the engine began to run rough, then lost power. According to the pilot, he turned on the boost pump, and the engine quit. The pump was turned off, the engine surged, then quit again. During a forced landing, the airplane struck trees, then came to rest on a street. Postaccident examination of the engine revealed corrosion in the left magneto, which was indicative of moisture contamination of the magneto that may have resulted in a loss of power. Additionally, the engine driven fuel pump pressure was set high, which would have resulted in a rich mixture, when the boost pump was activated.?

(SEA89LA093) ?AFTER LIFTOFF, THE ENGINE BEGAN MISFIRING AND THE PLT WAS UNABLE TO CLEAR OBSTACLES AHEAD. A TURN WAS MADE TO EFFECT A FORCED LANDING ON A PARALLEL ROADWAY. DURING ROLLOUT, THE LEFT WING STRUCK A POWER POLE. INVESTIGATION REVEALED THE LEFT MAGNETO ROTOR GEAR HAD STRIPPED.?
 
tclaire said:
To have the best of both the 3GI seems to work pretty well
http://www.g3ignition.com/benefits.html
Tim
Click to expand...

It's interesting that the manufacturer recommends that it is preferable to instal the control module aft of the firewall. Seems to be a common theme. Max temp for the module is 185 degrees F.

From the G3 Installation Manual:

2.3 MOUNTING AND LOCATION OF MODULES:
The Series ?1 G3i module and the MSD amplifier can be mounted together on an aluminum plate in a clean dry place away from engine heat. Preferably located on the backside of the engine firewall.
 
Alan Carroll said:
Bob,

I replaced my Slick with a second Lightspeed recently. Can't say I've noticed a change in performance, but I haven't done a careful test or raced with this setup yet. My expectation is that any change is going to fall within the range of measurement error (which in my experience is ?1-2 its).
Click to expand...


A close friend of mine replaced a virtually brand new Slick with a second PMAG recently. He has a very sophisticated engine monitoring system set up but he says he cannot detect any improvement in performance at all. I know people who have done the same with a second LightSpeed EI and reported a similar result.

I don't know of anybody who has reported any measurable performance improvements (more power, better fuel economy, smoother etc) by adding a second EI. It appears that the improvements all come with the first EI.
 
Captain Avgas said:
I don't know of anybody who has reported any measurable performance improvements (more power, better fuel economy, smoother etc) by adding a second EI. It appears that the improvements all come with the first EI.
Click to expand...

Most of us don't have the ability to actually measure/quantify the improvement from a second EI, but to me it "feels" like it runs smoother than when I had a mag and EI.
Others I know have reported the same "feeling".
 
Walt said:
Most of us don't have the ability to actually measure/quantify the improvement from a second EI, but to me it "feels" like it runs smoother than when I had a mag and EI.
Others I know have reported the same "feeling".
Click to expand...

I am convinced that my engine runs noticeably smoother when I clean the windscreen. :D

But jokes aside, what you seem to be saying is that there may be a subjective and extremely subtle improvement in engine smoothness with the second EI but that any improvement in power or fuel efficiency, if it exists, is so small as to be undetectable by you.
 
Captain Avgas said:
I am convinced that my engine runs noticeably smoother when I clean the windscreen. :D

But jokes aside, what you seem to be saying is that there may be a subjective and extremely subtle improvement in engine smoothness with the second EI but that any improvement in power or fuel efficiency, if it exists, is so small as to be undetectable by you.
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Exactly, except I feel as though I could definately detect the change but I never made any attemp to quantify the before and after numbers to prove it.

Its unlikely I would ever go back to a mag and single EI.
 
Bavafa said:
Wow, simply impressive ?. My temp strip on PMAG is at 185 or maybe even 190 and I consider my engine to run cool and will keep the oil door open any time landing and shutting down.
Click to expand...

Yes. the box is mounted per the designer at the very top of the firewall copilot side, one tube cooling. It is no where near the power plant. We also have the advantage of the longer cowling with my setup keeping the overall engine temps further away from the firewall and the EI box. Keep in mind this is in flight cruise temp.
 
Alan,

Good luck with the new set-up. It'll be interesting to see how the results shape up. Even if the speed improvement is "in the noise", cruise performance and temps over various flights will be interesting to note as well. Matching environmental conditions is always a big testing challenge, but over time, it will be fun to see if you clock faster race speeds or better cruise numbers. Thanks for the note!

Thanks Walt for the feedback. Gut feel is worth something in all of this, though numbers would be my motivation?but smoother is nice!

And Bob, mine isn't smoother after a windshield clean-up?but it is faster! :p

Ross or anyone else have performance testing data on dual EI vs. single EI? I'll bet there is some good data out there somewhere! :)

Cheers,
Bob

Alan Carroll said:
Bob,

I replaced my Slick with a second Lightspeed recently. Can't say I've noticed a change in performance, but I haven't done a careful test or raced with this setup yet. My expectation is that any change is going to fall within the range of measurement error (which in my experience is ?1-2 its).
Click to expand...
 
rvmills said:
Alan,

Good luck with the new set-up. It'll be interesting to see how the results shape up. Even if the speed improvement is "in the noise", cruise performance and temps over various flights will be interesting to note as well. Matching environmental conditions is always a big testing challenge, but over time, it will be fun to see if you clock faster race speeds or better cruise numbers. Thanks for the note!

Thanks Walt for the feedback. Gut feel is worth something in all of this, though numbers would be my motivation…but smoother is nice!

And Bob, mine isn't smoother after a windshield clean-up…but it is faster! :p

Ross or anyone else have performance testing data on dual EI vs. single EI? I'll bet there is some good data out there somewhere! :)

Cheers,
Bob
Click to expand...

Peak hp and efficiency at various rpms, MAP and AFR is simply about getting peak cylinder pressure occurring at the optimum time in the cycle. If the EI timing is advanced over the mag timing (assuming the mag timing is conservative), then the single EI can ultimately control where PCP is achieved. As such I don't see how a second EI would do much.

The EI might light off lean mixtures the mag would fail to do on a regular basis but I can't see much gain near best power AFRs which are easy to light off. There is something called ignition probability which is the systems ability to light off every single combustion cycle, even with fairly non-homogeneous or stratified fuel/ air mixtures. EI should be superior in this respect over a wider range of mixtures. How much this and other factors affects a typical Lycoming as far as power output would be hard to say without back to back dyno tests at identical timing values. I have seen minor changes in power on auto engines on the dyno with different ignition systems but never ran anything with mags to compare with. EIs likely sap less hp than mags in parasitic losses but that's probably pretty tiny on a Lycoming. I am just guessing that a mag takes more than 40-50 watts to turn at 2500 rpm. Timing scatter is much more of HP concern with gear driven distributors and mags however compared to crank triggered ignitions. This could account for noticeable hp changes between the two devices and I've seen this on auto engines. Again, back to back dyno tests on the same engine would confirm or deny this factor.

Fixed timing is simply not optimal over a wide range of rpms, MAP and AFR, of that there is little doubt. Nobody ever increased fuel flow or lost power with a properly set up and working EI as far as I know.

The EI does allow you to easily experiment in flight with timing changes if you have time and plenty of smooth airspace. On my installation (single plug) I was able to see changes in IAS with 2 degree changes in timing. You could develop your own timing curves this way.

I believe many people are going twin EIs because they simply don't want the maintenance and overhaul hassles/ costs of mags down the road. Yes the mag works but you don't see any production cars with mags and haven't for way over 50 years and the first distributorless auto EIs have been out for 30 years now- hardly new technology. Yes, you can argue you can't push your plane home if the ignition fails but statistically in our experience at least, this is a very remote possibility. Twin EIs (in our case again) have a much higher MTBF than the engines than are bolted to, assuming they are installed as per the book.

I'd have to use the parallel again between steam and glass panels. Who is installing steam gauges in a new build these days? 5%? There was the same sort of reluctance 10 years ago to glass. Now it's been proven to be more reliable than spinning gyros and offers other advantages. Mags don't need electrical power to work, that is their only real advantage. It seems that issue is easily mitigated with a backup battery or alternator for 5-10 pounds.

One more data point. The 2010 Reno Sport Class Gold winner Conti Questair Venture used one SDS EI/EMS and one mag. Worked just fine at the 750hp level and this combination exceeded 425 mph in testing on telemetry. The owner still wanted that mag on there to cross the Sierras as all this wizardry was new to him plus we didn't have room to fit another EI under the cowling... This comes down a lot to personal preference and mission perhaps. If a customer wants to retain one mag, I'm fine with it and many of our customers do. If he wants to ditch both mags, I'm ok with that too. We never steer anyone either way, just state the facts and let him decide.

Nobody needs a glass panel to fly day VFR but lots of people want glass anyway for all the other advantages it offers.
 
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kamikaze said:
Seems to me anything solid-state is likely to be more reliable than anything mechanical ...
Click to expand...

I've heard this argument many times but there is a flaw in the logic when it comes to ignition systems.

The argument may be true if you are completely replacing a mechanical system with a solid state system that does exactly the same thing. An example of that might be steam guages being replaced by an EFIS. Then the argument may be valid.

But this is not the case with an ignition system. An ignition system requires electrons and at the moment the electrons can only be ultimately generated by a mechanical system.

The PMAG is a mechanical device that generates its own electrons. It is an alternator.

LightSpeed and ElectroAir do not have an inbuilt alternator but when you instal this type of system your aircraft alternators immediately becomes an integral component of the ignition system and as such become a component in the reliability factor.

In other words there is always a mechanical component of any ignition system. You're not getting rid of a mechanical system and replacing it with a solid state system when you throw out your magneto. In essence what you're doing is just getting another mechanical system with a whole lot of complex electronics thrown in. :)
 
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Capflyer said:
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.
Click to expand...

In reality ElectroAir certificated ignitions systems are only approved for installation on certified aircraft that have a back-up magneto. ;)
 
Captain Avgas said:
LightSpeed and ElectroAir do not have an inbuilt alternator but when you instal this type of system your aircraft alternators immediately becomes an integral component of the ignition system and as such become a component in the reliability factor.
Click to expand...

Not really, both the alternator and battery would have to take a dump at the same time plus the vast majority of people installing twin EIs also install a second backup battery or permanent magnet alternator. In this case, 3 power supplies would have to fail at the same time. What are the odds of that with proper design? Me thinks a lot lower than odds of a mechanical failure of that one Lycoming engine up front.

Let's say your comm, transponder and EI draw a total of 10 amps (minimum flight current draw after load shedding non-critical loads). A couple of PC 680s will give you 2 hours of flight with an inoperative alternator. If you fly 4 hour legs and it took a dump right at the halfway mark, you'll still be able to complete the mission. If you night fly, you'd want more reserve power or seriously think of that backup alternator.
 
rv6ejguy said:
Not really, both the alternator and battery would have to take a dump at the same time plus the vast majority of people installing twin EIs also install a second backup battery or permanent magnet alternator. In this case, 3 power supplies would have to fail at the same time. What are the odds of that with proper design? Me thinks a lot lower than odds of a mechanical failure of that one Lycoming engine up front.

Let's say your comm, transponder and EI draw a total of 10 amps (minimum flight current draw after load shedding non-critical loads). A couple of PC 680s will give you 2 hours of flight with an inoperative alternator. If you fly 4 hour legs and it took a dump right at the halfway mark, you'll still be able to complete the mission. If you night fly, you'd want more reserve power or seriously think of that backup alternator.
Click to expand...

Ross, I think most people understand that when they instal a non self-powering dual EI set-up the aircraft alternator becomes a very important part of that system. That's the reason they invariably opt for a second alternator. They appreciate that the battery might be supplying electrons to the EI but the alternator is ultimately supplying the electrons to the battery. :)

I'll return to my original premise. It doesn't matter what sort of ignition system one opts for.....ultimately the initial source of the electrons is going to be a mechanical device.
 
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Great post Ross...thanks!! :)

Cheers,
Bob

rv6ejguy said:
Peak hp and efficiency at various rpms, MAP and AFR is simply about getting peak cylinder pressure occurring at the optimum time in the cycle. If the EI timing is advanced over the mag timing (assuming the mag timing is conservative), then the single EI can ultimately control where PCP is achieved. As such I don't see how a second EI would do much.

The EI might light off lean mixtures the mag would fail to do on a regular basis but I can't see much gain near best power AFRs which are easy to light off. There is something called ignition probability which is the systems ability to light off every single combustion cycle, even with fairly non-homogeneous or stratified fuel/ air mixtures. EI should be superior in this respect over a wider range of mixtures. How much this and other factors affects a typical Lycoming as far as power output would be hard to say without back to back dyno tests at identical timing values. I have seen minor changes in power on auto engines on the dyno with different ignition systems but never ran anything with mags to compare with. EIs likely sap less hp than mags in parasitic losses but that's probably pretty tiny on a Lycoming. I am just guessing that a mag takes more than 40-50 watts to turn at 2500 rpm. Timing scatter is much more of HP concern with gear driven distributors and mags however compared to crank triggered ignitions. This could account for noticeable hp changes between the two devices and I've seen this on auto engines. Again, back to back dyno tests on the same engine would confirm or deny this factor.

Fixed timing is simply not optimal over a wide range of rpms, MAP and AFR, of that there is little doubt. Nobody ever increased fuel flow or lost power with a properly set up and working EI as far as I know.

The EI does allow you to easily experiment in flight with timing changes if you have time and plenty of smooth airspace. On my installation (single plug) I was able to see changes in IAS with 2 degree changes in timing. You could develop your own timing curves this way.

I believe many people are going twin EIs because they simply don't want the maintenance and overhaul hassles/ costs of mags down the road. Yes the mag works but you don't see any production cars with mags and haven't for way over 50 years and the first distributorless auto EIs have been out for 30 years now- hardly new technology. Yes, you can argue you can't push your plane home if the ignition fails but statistically in our experience at least, this is a very remote possibility. Twin EIs (in our case again) have a much higher MTBF than the engines than are bolted to, assuming they are installed as per the book.

I'd have to use the parallel again between steam and glass panels. Who is installing steam gauges in a new build these days? 5%? There was the same sort of reluctance 10 years ago to glass. Now it's been proven to be more reliable than spinning gyros and offers other advantages. Mags don't need electrical power to work, that is their only real advantage. It seems that issue is easily mitigated with a backup battery or alternator for 5-10 pounds.

One more data point. The 2010 Reno Sport Class Gold winner Conti Questair Venture used one SDS EI/EMS and one mag. Worked just fine at the 750hp level and this combination exceeded 425 mph in testing on telemetry. The owner still wanted that mag on there to cross the Sierras as all this wizardry was new to him plus we didn't have room to fit another EI under the cowling... This comes down a lot to personal preference and mission perhaps. If a customer wants to retain one mag, I'm fine with it and many of our customers do. If he wants to ditch both mags, I'm ok with that too. We never steer anyone either way, just state the facts and let him decide.

Nobody needs a glass panel to fly day VFR but lots of people want glass anyway for all the other advantages it offers.
Click to expand...
 
Captain Avgas said:
Ross, I think most people understand that when they instal a non self-powering dual EI set-up the aircraft alternator becomes a very important part of that system. That's the reason they invariably opt for a second alternator. They appreciate that the battery might be supplying electrons to the EI but the alternator is ultimately supplying the electrons to the battery. :)

I'll return to my original premise. It doesn't matter what sort of ignition system one opts for.....ultimately the initial source of the electrons is going to be a mechanical device.
Click to expand...

You state the obvious. EI is different, you need backup power. You fit the extra battery or alternator. Done. Most people with dual EIs have triple power redundancy- a proven way to mitigate the risk if the primary alternator fails.

Remember the current draw for a single EI in cruise is around 2-3 amps so in an emergency with all other electrics off, you can fly for many hours on a typical PC680- more time than most RVs carry fuel for.
 
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Captain Avgas said:
The argument may be true if you are completely replacing a mechanical system with a solid state system that does exactly the same thing. An example of that might be steam guages being replaced by an EFIS. Then the argument may be valid.

But this is not the case with an ignition system. An ignition system requires electrons and at the moment the electrons can only be ultimately generated by a mechanical system.
Click to expand...

There are a couple of flaws in this reasoning.

Firstly, the EFIS example is very much like the EI example, since they BOTH require electrons to run.

Secondly, the EI and EFIS can obtain electrons from both a mechanical system (alternator) and from a chemical system (battery). Both of these are viable sources for electrons, whether both are running, or each is running independently (ie, alt and batt, alt alone, or batt alone). There is no safety requirement for electrons to be *generated* within the duration of a flight, merely that there is an adequate *supply* available to complete the flight, much the same as with the fuel supply. You can "fill up" your electron source at the end of the flight similar to putting more fuel in the tanks. An excellent example of this is aircraft that have electric engines and run off batteries only (no solar panels or other means of generating electrons).

Ultimately there is no single point of failure residing in an alternator alone, unless for some reason you crafted an electrical system with no battery. Obviously you don't want to take off without a working alternator, but we are talking about failure rates and being able to safely complete the flight. The alternator is merely one component among many, and by itself is not required for safe completion of the flight.

The chances of both the alternator and battery failing within the time frame of a flight is so low that I personally do not believe it to be of concern. This is similar to having both magnetos fail within the same flight. That's not to say it is impossible, but I think it more likely that something else would fail on the airplane before either of these happened.

-Dj
 
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deej said:
The chances of both the alternator and battery failing within the time frame of a flight is so low that I personally do not believe it to be of concern. This is similar to having both magnetos fail within the same flight. That's not to say it is impossible, but I think it more likely that something else would fail on the airplane before either of these happened.

-Dj
Click to expand...

Just in case some one reads your above statement and takes it as fact which would normally be reasonable since two failures seldom happen at the same time, I would like to make a subtle but important clarification as it may save someone some pain due to misunderstanding.

While I agree that both the alternator and battery are unlikely to fail during the same flight, the fact is that batteries don't suddenly fail, but may "seem" to fail (and for all practical purposes ACTUALLY fail to provide what we need) shortly after the alternator fails on the same flight.

Batteries start to degrade (loose capacity) pretty much from day one. However, we consider them a good (enough) battery as long as they are strong enough to start the plane with the usually vigor. However, the amount of electrical energy required to start the engine is very small compared to what we expect from the battery during an alternator failure.

Now suppose one day the alternator fails to supply electrons. The battery picks up the slack to run all the loads. Since we don't know the condition (capacity) of the battery at the time (other than it's good enough to start the engine), we don't know if there's enough electrons to run all our loads to our destination (planned or alternate).

Here's where the two failures (alternator and battery) may "seem" to occur on the same flight. The battery may have been more than 50% "failed" for some time already and has been that way for many flights. But other than starting the engine, and maybe satisfying short term power demands that exceed the alternators ability, the battery has little to do and few opportunities to tell us it's getting old. We are after all, depending on the alternator for primary power. It's when that source is gone, we find the capacity of the battery is less than needed/expected and we consider the battery "failed" as well. :)

Bevan
 
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Bevan, that is a very important point. If you have an electrically dependent aircraft, whether that be flight instruments and/or engine, your battery should be on the list of things to check at every annual. Bob Nuckolls recommends a relatively cheap battery load tester from Harbor Freight to perform this test.

I think it is this one: http://www.harborfreight.com/500-amp-carbon-pile-load-tester-91129.html

In addition, you may also consider changing out the battery on a regular basis, but the load test is a good idea regardless.

I have a two battery setup, and intend on changing out one of the batteries every year, alternating batteries each year.

-Dj
 
Very good DJ.

If I had an electrically dependant engine, I would have one large battery as opposed to two smaller ones (simpler) and would have complete battery monitoring and maintenance systems.. But that's just me.

As it is, I have four alternators and one battery. :rolleyes:

Bevan
 
To back this point up a bit, I recently completed the annual inspection on a certificated O-320-equipped aircraft. The aircraft battery, a Gill G-25, was less than a year old, but hadn't flown very much since it had been installed, less than 10 hours. In the month prior to annual inspection the battery had failed to crank the engine twice in four starts and had been recharged on each occasion using a regular automotive charger.

As part of the annual inspection I took the battery home and load-tested it with a simple halogen driving light as the load, producing about 4.2 amps of current draw. This load test was a shocker. Voltage dropped 1 volt in just a bit more than 10 minutes. Another half volt of drop occurred while I was pfutzing around to get a second multimeter, just to verify the readings on the first one. At this point I discontinued the discharge cycle.

After reading the Gill maintenance manual I opted to follow the manufacturer's recommendation to restore capacity through a constant voltage charge - the recommended voltage to be applied is 14.2 volts for this particular battery. Using a variable DC power supply I proceeded with this constant voltage charge for 24 hours, and then let the battery sit for several hours before initiating a discharge test. Lo and behold, the battery's capacity had improved.

Thinking that if some is good, more must be better, I initiated another constant voltage charge cycle, this time letting it run nearly 48 hours, then letting the battery sit for about 12 hours before performing the discharge test. The recovery of battery capacity was nothing short of dramatic. With the 4.2Amp load applied to the battery it had dropped only a few tenths of a volt after an hour, and after two hours it still hadn't dropped below 12V. I again did a 48 hour constant voltage charge and returned the battery to service, just in time for it to be exposed to our lovely deep freeze temperatures where it has had no troubles cranking the engine.

So what lessons have I learned?
1) even a relatively new battery can provide drastically reduced capacity - you don't want to discover this fact when you need electrons the most
2) the only way to know how much capacity a battery has is to test it
3) follow the manufacturer's advice on charging and capacity restoration processes
4) the aircraft I'm building will have an electrical system very similar to Dj's, although from the experience with this particular battery I think I'm leaning more toward a self-powered electronic ignition if/when the time comes to retire the magnetos.
 
On an electrically dependent aircraft, I hope everyone here performs a battery load test annually and if not, replaces the main and backup batteries every 3-5 years as insurance against age degradation which I have talked about before. A battery which holds less than 12.2V after a full charge and one hour of wait time would be suspect already as a further external clue. All this is about proper maintenance again, not something to blame on an EI directly.

I've also already talked about designing your electrical system with EIs to be able to support them for at least half the duration of your maximum mission time. In addition, if you have electrically dependent panels, fly at night or fly IFR you need to plan accordingly for the extra current draw of those items to continue safe flight. In these cases, I'd recommend a second alternator.


I learned the hard way about detecting alternator failure early a few years back and recommend both visual and aural low voltage warnings starting at 12.5V.

Be aware that many avionics like radios and transponders will sign off at around 9V. Most good EIs will run down to around 7V.

I've posted this link before: http://www.power-sonic.com/images/powersonic/technical/1277751263_20100627-TechManual-Lo.pdf Look on pages 7 to 11 to see the typical performance to 9V vs. time and current draw and all other factors. Remember that battery performance also falls off at lower temperatures and that when you get down below 9V, remaining battery capacity is less than 10%.

This thread was about using a single mag and single EI on a Lycoming. We don't really need to worry about the EI in this case if it fails since the mag should continue to run the engine well enough. If that's what makes you happy, it's a perfectly valid choice as are twin EIs with a tertiary power backup- either alternator or battery.

Unless someone can present some solid data showing twin EIs give a useful boost in power or fuel economy over one, it seems as though the consensus is negative in that regard. A second EI then is mainly to avoid the periodic maintenance/ overhaul and parts costs involved with keeping mags operating reliably.
 
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Good exchange of ideas but my rhetorical question is how many alternators have a mandatory overhaul at 500hrs of operation? I don't know of any and there are hundreds of millions of alternators on cars, trucks, boats, airplanes, and electrical motors of all sizes (reverse connected alternator) installed on refrigerators, washing machines, dryers, air conditioners, ceiling fans, etc...

rv6ejguy said:
This thread was about using a single mag and single EI on a Lycoming. We don't really need to worry about the EI in this case if it fails since the mag should continue to run the engine well enough. If that's what makes you happy, it's a perfectly valid choice as are twin EIs with a tertiary power backup- either alternator or battery.
Click to expand...

My thoughts exactly.

:cool:
 
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So after reading this entire thread, and understanding 43% of it, here is what this layman got from it. Run dual batteries, dual alternators, one ElectroAir (insert ur brand here) set up, and one "magneto".

Here's my question though.....does a PMAG count as a magneto since it has a built in alternator or are they talking about a slick mag??
 
SinCityJets said:
So after reading this entire thread, and understanding 43% of it, here is what this layman got from it. Run dual batteries, dual alternators, one ElectroAir (insert ur brand here) set up, and one "magneto".

Here's my question though.....does a PMAG count as a magneto since it has a built in alternator or are they talking about a slick mag??
Click to expand...

IMHO Current generation of PMAGs are equivalent to a more reliable magneto.

:cool:
 
Bevan said:
Just in case some one reads your above statement and takes it as fact which would normally be reasonable since two failures seldom happen at the same time, I would like to make a subtle but important clarification as it may save someone some pain due to misunderstanding.

While I agree that both the alternator and battery are unlikely to fail during the same flight, the fact is that batteries don't suddenly fail, but may "seem" to fail (and for all practical purposes ACTUALLY fail to provide what we need) shortly after the alternator fails on the same flight.

Batteries start to degrade (loose capacity) pretty much from day one. However, we consider them a good (enough) battery as long as they are strong enough to start the plane with the usually vigor. However, the amount of electrical energy required to start the engine is very small compared to what we expect from the battery during an alternator failure.

Now suppose one day the alternator fails to supply electrons. The battery picks up the slack to run all the loads. Since we don't know the condition (capacity) of the battery at the time (other than it's good enough to start the engine), we don't know if there's enough electrons to run all our loads to our destination (planned or alternate).

Here's where the two failures (alternator and battery) may "seem" to occur on the same flight. The battery may have been more than 50% "failed" for some time already and has been that way for many flights. But other than starting the engine, and maybe satisfying short term power demands that exceed the alternators ability, the battery has little to do and few opportunities to tell us it's getting old. We are after all, depending on the alternator for primary power. It's when that source is gone, we find the capacity of the battery is less than needed/expected and we consider the battery "failed" as well. :)

Bevan
Click to expand...

Bevan, that was a terrific post, and so true. Many years ago I was on a night IFR flight over a mountain range in an Archer when my alternator died. There was not a lot of things I could safely turn off. Well, the battery lasted all of 20 minutes and then, to my horror, everything electrical started flickering and closing down one at a time.

The aircraft was LAME maintained and there was no prior indication that the battery was not holding amphours. The engine had started strongly.

Ultimately I was left in complete blackness flying solo with a torch in my mouth pointed at the AH and DI (both vacuum driven thank God) to keep the aircraft upright and generally heading in the right direction. It was so black inside and outside the aircraft that without the torch I would not have been able to see the AH and I would have perished.

It was really tough going. I lost my IFR GPS and all my navaids for navigation. I lost my transponder in CTA, and of course I lost my radios and could not contact ATC. And I had no pitot heat if required. I was living right on the edge.

But up front that good ol' Lycoming engine kept running strongly on its magnetos and I kept telling myself that as long as I had fuel I'd be OK. In those circumstances you fully understand that an engine and it's associated ignition system is like a heart pacemaker. You understand that it's the only thing that's keeping you alive.

Anyway this will be my last post on this thread. It has been a good thread with a lot of varied and informative opinions and hopefully it will assist builders to form their own conclusions about which way they should go in terms of an ignition system.

And finally I want to take the opportunity to apologise to Jake for my intemperate comments about him. Sorry Jake.
 
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Wait, Bob! You can't just leave the story there! So what happened. How did you make it through? Were you in IMC conditions?

Captain Avgas said:
Bevan, that was a terrific post, and so true. Many years ago I was on a night IFR flight over a mountain range in an Archer when my alternator died. There was not a lot of things I could safely turn off. Well, the battery lasted all of 20 minutes and then everything electrical started flickering and closing down one at a time.

The aircraft was LAME maintained and there was no prior indication that the battery was not holding amphours. The engine had started strongly.

Ultimately I was left in complete blackness flying solo with a torch in my mouth pointed at the AH and DI (both vacuum driven thank God) to keep the aircraft upright and generally heading in the right direction. It was so black that without the torch I would not have been able to see the AH and I would have perished.

It was really tough going. I lost my IFR GPS and all my navaids for navigation. I lost my transponder in CTA, and of course I lost my radios and could not contact ATC. And I had no pitot heat if required. I was living right on the edge.

But up front that good ol' Lycoming engine kept running strongly on its magnetos and I kept telling myself that as long as I had fuel I'd be OK. In those circumstances you fully understand that an engine and it's associated ignition system is like a heart pacemaker. You understand that it's the only thing that's keeping you alive.

Anyway this will be my last post on this thread. It has been a good thread with a lot of varied and informative opinions and hopefully it will assist builders to form their own conclusions about which way they should go in terms of an ignition system.

And finally I want to take the opportunity to apologise to Jake for my intemperate comments about him. Sorry Jake.
Click to expand...
 
Captain Avgas said:
The aircraft was LAME maintained and there was no prior indication that the battery was not holding amp hours. The engine had started strongly.
Click to expand...

What you've described is a maintenance issue. Whomever was doing the maintenance likely did not test the battery, so therefore you had no way of knowing the condition.

This is much the same as taking off without verifying the amount of fuel in the tanks.

-Dj
 
Ross and others,

If you design your dual EI fired airplane around a complex electrical system with dual batteries, alternators, etc., I would recommend you design it so no action is required in the event of a failure of any single component.

There are two reasons, and a friend with an auto conversion proved it out.

In the event of an issue, two things happen; first your fine motor skills go away and second, you tend to forget things. In his case, my buddy forgot to turn on the Ebus designed for his rotary. A safe engine out landing was made on an airport and he was able to fix the problem and be on his way.

Second, if you sell your plane, the new owner may not understand the electrical system and not take the correct action required to keep it running until a safe landing can be made, should some component fail.
 
N941WR said:
Ross and others,

If you design your dual EI fired airplane around a complex electrical system with dual batteries, alternators, etc., I would recommend you design it so no action is required in the event of a failure of any single component.

There are two reasons, and a friend with an auto conversion proved it out.

In the event of an issue, two things happen; first your fine motor skills go away and second, you tend to forget things. In his case, my buddy forgot to turn on the Ebus designed for his rotary. A safe engine out landing was made on an airport and he was able to fix the problem and be on his way.

Second, if you sell your plane, the new owner may not understand the electrical system and not take the correct action required to keep it running until a safe landing can be made, should some component fail.
Click to expand...

There are two schools of thought here and I think this comes down to preference mainly. I prefer manual activation and in my case, I understand everything about my system and I routinely practice system failures and emergency procedures so it is conditioned. In my case, nothing critical that I have any control of requires immediate action, the checklist covers the alternator failure scenario if I am in a fog.

Auto changeover between 2 batteries, 2 alternators, 2 busses and perhaps two EIs involves many combinations of actions. Those better be very well thought out in design with every failure mode and eventuality thought of if you have automatic switching. We know from accidents that software/ hardware deficiencies happen outside the design window sometimes and things were not identified in the design process.

I prefer to be on top of my systems and make my own selections if something goes wrong.

I hope all pilots understand their systems- otherwise you shouldn't be flying IMO. This also applies to new owners of an aircraft they didn't build. Knowing your airplane and its systems is important and might save your life in the event of an emergency.
 
Captain Avgas said:
Bevan, that was a terrific post, and so true. Many years ago I was on a night IFR flight over a mountain range in an Archer when my alternator died. There was not a lot of things I could safely turn off. Well, the battery lasted all of 20 minutes and then, to my horror, everything electrical started flickering and closing down one at a time.
Click to expand...

Very scary experience for sure here. I think some Archers only had 20 amp hour batteries so you'd only expect 20-30 minutes to 9V with typical night IFR electrical loads.

I guess you have more faith in engines and systems than I do. I don't fly at night over the rocks single engine. I am glad it all turned out ok!
 
Life support systems

Some of the systems on board our aircraft ARE life support systems. It doesn't matter what you call your classification of aircraft. Therefore it is well worth your time to fully understand, practice and test your critical systems including battery capacity as Ross mentioned.

Bevan
 
Everyone, have a read of this coroners report. Despite the scathing and accurate comments about the RAAus and CASA, think a bit deeper about the following points. And mainly about design choices. Do not focus on the fact the W&B was questionable or that he stalled it. It is the contributing factors, some of which are not relevant to this thread but some are.

1. Complete electronic ignition dependency of electrons.

2. Myriad of emergency power systems??? How easy to diagnose and implement in flight?

3. What happens when you are say?..very senior in age and can't necessarily process the technology and choices.

4. What happens to the next owner or casual pilot?

Just food for thought.

http://vocasupport.com/wp-content/uploads/2015/01/cif-uscinski-20141229.pdf
 
One thing I don't like about an automatic method of switching to back-up power is it could likely limit the ability to test the backup power source before take-off.

Having 2 alternators is great, but if the back-up alternator died 6 months ago and you never noticed, what good is it?

Now, to add more complexity to the conversation. How do you diagnose and isolate an electrical fire in flight? I am trying to design my electrical system so I can completely turn off one system and activate another emergency system that will power EI, fuel pump(s) and EFIS. I'm still at the design stage, so if it become too complex, I may just use 1 mag/1 EI combination and not worry about it. (I'm also contemplating dual electric fuel pumps, so my decision is complex)
 
RV10inOz said:
Everyone, have a read of this coroners report. Despite the scathing and accurate comments about the RAAus and CASA, think a bit deeper about the following points. And mainly about design choices. Do not focus on the fact the W&B was questionable or that he stalled it. It is the contributing factors, some of which are not relevant to this thread but some are.

1. Complete electronic ignition dependency of electrons.

2. Myriad of emergency power systems??? How easy to diagnose and implement in flight?

3. What happens when you are say…..very senior in age and can't necessarily process the technology and choices.

4. What happens to the next owner or casual pilot?

Just food for thought.

http://vocasupport.com/wp-content/uploads/2015/01/cif-uscinski-20141229.pdf
Click to expand...

These are all good points.

Design the backup system so it's easy to understand, robust and easy to activate.

Point 3 and 4, do yourself and everyone else a favor, hang up your headset when you no longer have the faculties to fly safely. We are supposed to self evaluate our mental and physical state prior to every flight at every stage of life. Do you fly with a bad head cold? When you are dead tired? 2 hours after your wife or GF left you? Looking around the cockpit and fumbling for switches? Step into an airplane you don't understand the systems?
 
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David Z said:
One thing I don't like about an automatic method of switching to back-up power is it could likely limit the ability to test the backup power source before take-off.

Having 2 alternators is great, but if the back-up alternator died 6 months ago and you never noticed, what good is it?

Now, to add more complexity to the conversation. How do you diagnose and isolate an electrical fire in flight? I am trying to design my electrical system so I can completely turn off one system and activate another emergency system that will power EI, fuel pump(s) and EFIS. I'm still at the design stage, so if it become too complex, I may just use 1 mag/1 EI combination and not worry about it. (I'm also contemplating dual electric fuel pumps, so my decision is complex)
Click to expand...

Good points, be able to test and isolate your backup alternator and battery.

In the end, for many people, it may well be best to simply go for one mag and one EI and skip all this...
 
David Z said:
One thing I don't like about an automatic method of switching to back-up power is it could likely limit the ability to test the backup power source before take-off.
Click to expand...

Agreed - what good is the back up if it's inop?

My suggestion is to steal a page from Cessna's playbook. When I checked out in a 172 that had the G1000 (to decide if I would even want a Garmin EFIS), they have a backup battery to power the critical energy-dependent systems.

here is the POH section for how the battery is checked:

STARTING ENGINE (With Battery)
1. Throttle Control - OPEN 1/4 INCH
2. Mixture Control - IDLE CUTOFF (pull full out)
3. STBY BATT Switch:
a. TEST - (Hold for 20 seconds, verify that green TEST
lamp does not go off)
b. ARM - (Verify that PFD comes on)
4. Engine Indicating System - CHECK PARAMETERS (Verify
no red X's through ENGINE page indicators)
5. BUS E Volts - CHECK (Verify 24 VOLTS minimum shown)
6. M BUS Volts - CHECK (Verify 1.5 VOLTS or less shown)
7. BATT S Amps - CHECK (Verify discharge shown (negative))
8. STBY BATT Annunciator - CHECK (Verify annunciator is
shown)
9. Propeller Area - CLEAR (Verify that all people and
equipment are at a safe distance from the propeller)

I don't know the specifics on the test circuit, but I think it is a large resistor and the discharge test verifies that the battery capacity is enough to carry that large load for 20 seconds - which must relate to 45 mins or whatever of emergency bus loads.
 
RV10inOz said:
Everyone, have a read of this coroners report.
Click to expand...

Thank you David...a very interesting report.

Isuzu-based auto conversion, coil on plug, electronic injection, dual sensors but no dual ECU, and apparently no redundant power supply. This is probably it:

http://markhooper.me/spitfire/Resources_files/1.V6 engine sub.pdf

The design lesson is the cascading effect of multiple high amp demands.

The builder apparently selected an ignition controller that drops out at 10.5 volts. If that 10.5 value is true (Motec...anybody know for sure?), it would significantly cut into the battery-only flight time and is arguably a poor choice for a single alternator/single ignition aircraft. 7~9 volts minimum is typical for systems familiar to RV builders. As noted previously in this thread, all electronic ignitions are not the same.

In addition to ignition power, this designer expected the battery system to support fuel pump(s), electric prop pitch control, flaps, and retractable landing gear. The trap is the amperage demands made by the flap, prop, and landing gear motors. Consider a battery system depleted to perhaps 11V. At that voltage level, adding a significant motor load would probably pull system voltage below 10.5....and fail the ignition.

David is right, in that a pilot at the top of his game may be able to deal with the issue, while another pilot, not so sharp, may stumble into the trap. For example, the sharp guy, recognizing the effect of motor loads, may choose to forgo prop control and flaps, and use the manual gear extension. The fact that there is a way to deal with a problem doesn't make it acceptable to build the problem into the system.

POSTSCRIPT: Found time to review Motec literature (the above engine management computer) and discovered an oddity. The Coroner's Report states (pg25) "..or the Motec Unit line voltage dropped below 10.5 volts and the engine stopped." However, Motec literature states the system operating voltage is "6 to 22 volts". I am inclined to believe the manufacturer, but users should still make minimum operating voltage an important item on their test schedule.
 
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DanH said:
Thank you David...a very interesting report.

Isuzu-based auto conversion, coil on plug, electronic injection, dual sensors but no dual ECU, and apparently no redundant power supply. This is probably it:

http://markhooper.me/spitfire/Resources_files/1.V6 engine sub.pdf

The design lesson is the cascading effect of multiple high amp demands.

The builder apparently selected an ignition controller that drops out at 10.5 volts. If that 10.5 value is true (Motec...anybody know for sure?), it would significantly cut into the battery-only flight time and is arguably a poor choice for a single alternator/single ignition aircraft. 7~9 volts minimum is typical for systems familiar to RV builders. As noted previously in this thread, all electronic ignitions are not the same.

In addition to ignition power, this designer expected the battery system to support fuel pump(s), electric prop pitch control, flaps, and retractable landing gear. The trap is the amperage demands made by the flap, prop, and landing gear motors. Consider a battery system depleted to perhaps 11V. At that voltage level, adding a significant motor load would probably pull system voltage below 10.5....and fail the ignition.

David is right, in that a pilot at the top of his game may be able to deal with the issue, while another pilot, not so sharp, may stumble into the trap. For example, the sharp guy, recognizing the effect of motor loads, may choose to forgo prop control and flaps, and use the manual gear extension. The fact that there is a way to deal with a problem doesn't make it acceptable to build the problem into the system.
Click to expand...

Remember the Diamond Twinstar diesel crash a few years back? Pilots ignored the flight manual warning about battery charging. When they retracted the gear, both FADECs went off, immediate forced landing was the result. Pilot error plus a poor system design as well.
 
Has anybody heard of a generator that would be appropriate as a backup power supply?
The problem with alternators is they need a battery to excite the winding and that adds significant complexity. If one could bolt a 10-20 amp generator to the vacuum pad it, seems like it might work. Not sure if it's realistic to expect a generator to supply adequate power over such a broad range of rpm. Maybe add a rpm restriction on emergency power, 900-2100rpm?

Anyone smarter than me have any thoughts.
 
David Z said:
Has anybody heard of a generator that would be appropriate as a backup power supply?
The problem with alternators is they need a battery to excite the winding and that adds significant complexity. If one could bolt a 10-20 amp generator to the vacuum pad it, seems like it might work. Not sure if it's realistic to expect a generator to supply adequate power over such a broad range of rpm. Maybe add a rpm restriction on emergency power, 900-2100rpm?

Anyone smarter than me have any thoughts.
Click to expand...

Lots of people using these: http://www.aircraftspruce.com/catalog/eppages/sdaltreg.php
 
I have looked at those, the SD-20 as well. But they are an alternator and require something to excite the windings. That's why I am thinking of a generator. So regardless of what's going on with any myriad of electrical system malfunctions, it can always be counted on to start making power.
 
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