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jindoguy(at)gmail.com
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 Posted: Sun Sep 23, 2007 4:02 am Post subject: Dual Ignition |
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Peter, Upon what data does your statement, "the average mag is horribly unreliable", come from? Properly setup and serviced, quite the opposite is true, in my experience. Also your statement that the dual ignition is required by jug size is questionable, too.
Last year while in class to get my LSA repairman maintenance ticket I set the up two Slick mags to go into an A75. I set the internal timing of the mags so that it was dead on for both, and the engine timing the same. The instructor was on the verge of accusing me of having OCD as I checked and rechecked until I was satisfied it was as close as I could get it. When I was finally satisfied, we pulled the plane out to the ramp and started it up. After it was up to operating temp I did a mag check. It scared the wits out of me when I got NO mag drop. Now the EIS installed on the plane only read in 10 RPM increments, so there may have been some drop, but the instrument didn't read it and I could neither hear it, nor feel it in the seat of my pants. I thought sure I had installed the P leads improperly and was ready to use the fuel valve to shut the engine down when the instructor stepped in, checked all the connections and pronounced them good. I did a second mag check, and still got no detectable drop. I pulled the throttle back to idle, closed both mag switches and the engine died just as it should. What gives, I always gotten some drop on every plane I've ever been in. We pulled out the continuity checker and went over the P leads again. Everything was as it should be. Restarted the engine, established 1700 RPM and checked again. NO drop. Shut down the left mag, let the engine run for a bit and shut down the right mag. The engine died. Restarted, shut down the right mag and let the engine run. Again, NO mag drop. Killed the left mag, engine died. I'm sure the WTFO expression on my face begged an explanation. The instructor, whose list of certs look like alphabet soup gone mad, said it's simple really. It's a very low time engine (his personal E-AB aircraft, by the way) and the students in the class had set everything up as near perfect as was humanly possible, hence no discernible mag drop. He recounted how many a long faced pilot, discouraged by the $2000 quote for parts and labor from another shop has become his loyal customer when a new set of points and careful setting of internal mag timing and engine timing has restored the mags to proper working order for less than a 1/4 of the original estimate.
Now lets take the other end of the spectrum. I have and HKS700E engine on my trike. It's got 40 hours on it. My OCD tendencies when it comes to engine variables is as active as ever. It has dual CDI's for each of its two diminutive 350cc cylinders. My first "mag" check was a real upholstery clincher. I did the check at 3000 RPM and each system showed a 500 RPM drop. Needless to say I was in a near panic getting to the manuals before I called the importer. Under ignition check it said, "engine shouldn't die"! It's taken a bit to get used to, but that's the way the little engine is designed. It runs like the proverbial sewing machine, otherwise.
My point is, engine design, system integration, and proper setup has much more to do with ignition system performance than reliance on OWT's about "horribly unreliable" claims.
Rick
--
Rick Girard
"Ya'll drop on in"
takes on a whole new meaning
when you live at the airport. [quote][b]
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peter(at)sportingaero.com
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| Posted: Sun Sep 23, 2007 10:38 am Post subject: Dual Ignition |
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Rick,
In my experience the unreliability of mags is no OWT - they are. In 1300 hrs of flight time I have had 2 mags fail outright (both coil failures), a couple of spark plug failures and a harness break down giving a misfire. To be more accurate I could have written ‘the average ignition system’, but the sentiment is the same. In all cases the mags has been serviced as required (eg within 500 hrs for slick mags). The reason we have 2 ignitions is because on their own there are insufficiently reliable to prevent aircraft dropping out of the sky at an unacceptable rate. That we have to service the ignition system so often is another indicator. Yes typical aero engines run better with 2 sparks, but I don’t think that is the primary reason.
Peter
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echristley(at)nc.rr.com
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| Posted: Mon Sep 24, 2007 5:22 am Post subject: Dual Ignition |
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Richard, the fact that the mags require "regular maintenance" and
"proper setup" by someone stricken with OCD to work as you describe is
the classical definition of unreliable. You can't 'rely' on the average
hack with wet ink on his A&P license to set it correctly, and the fact
that it needs to be done so often means the hack will be doing it or you
will be. The electronic ignitions are not nearly as reliant on special
training or fine attention to installation and maintenance details. You
plug it in, and if it works, it works as designed.
The fact that the HKS700E was designed to have a significant drop on one
ignition is a red herring. That could have easily been designed in on
purpose so that you would have a definite reassurance that both are
working after the mag check.
The mag is a complicated electromechanical device that is a masterpiece
of engineering. But they are not reliable. Else, why do you carry two
of them around, and why do you check both of them just before takeoff on
every flight?
Richard Girard wrote:
| Quote: | Peter, Upon what data does your statement, "the average mag is
horribly unreliable", come from? Properly setup and serviced, quite
the opposite is true, in my experience. Also your statement that the
dual ignition is required by jug size is questionable, too.
Last year while in class to get my LSA repairman maintenance ticket I
set the up two Slick mags to go into an A75. I set the internal timing
of the mags so that it was dead on for both, and the engine timing the
same. The instructor was on the verge of accusing me of having OCD as
I checked and rechecked until I was satisfied it was as close as I
could get it. When I was finally satisfied, we pulled the plane out to
the ramp and started it up. After it was up to operating temp I did a
mag check. It scared the wits out of me when I got NO mag drop. Now
the EIS installed on the plane only read in 10 RPM increments, so
there may have been some drop, but the instrument didn't read it and I
could neither hear it, nor feel it in the seat of my pants. I thought
sure I had installed the P leads improperly and was ready to use the
fuel valve to shut the engine down when the instructor stepped in,
checked all the connections and pronounced them good. I did a second
mag check, and still got no detectable drop. I pulled the throttle
back to idle, closed both mag switches and the engine died just as it
should. What gives, I always gotten some drop on every plane I've ever
been in. We pulled out the continuity checker and went over the P
leads again. Everything was as it should be. Restarted the engine,
established 1700 RPM and checked again. NO drop. Shut down the left
mag, let the engine run for a bit and shut down the right mag. The
engine died. Restarted, shut down the right mag and let the engine
run. Again, NO mag drop. Killed the left mag, engine died. I'm sure
the WTFO expression on my face begged an explanation. The instructor,
whose list of certs look like alphabet soup gone mad, said it's simple
really. It's a very low time engine (his personal E-AB aircraft, by
the way) and the students in the class had set everything up as near
perfect as was humanly possible, hence no discernible mag drop. He
recounted how many a long faced pilot, discouraged by the $2000 quote
for parts and labor from another shop has become his loyal customer
when a new set of points and careful setting of internal mag timing
and engine timing has restored the mags to proper working order for
less than a 1/4 of the original estimate.
Now lets take the other end of the spectrum. I have and HKS700E engine
on my trike. It's got 40 hours on it. My OCD tendencies when it comes
to engine variables is as active as ever. It has dual CDI's for each
of its two diminutive 350cc cylinders. My first "mag" check was a real
upholstery clincher. I did the check at 3000 RPM and each system
showed a 500 RPM drop. Needless to say I was in a near panic getting
to the manuals before I called the importer. Under ignition check it
said, "engine shouldn't die"! It's taken a bit to get used to, but
that's the way the little engine is designed. It runs like the
proverbial sewing machine, otherwise.
My point is, engine design, system integration, and proper setup has
much more to do with ignition system performance than reliance on
OWT's about "horribly unreliable" claims.
Rick
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Kellym
Joined: 10 Jan 2006
Posts: 1705
Location: Sun Lakes AZ
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| Posted: Mon Sep 24, 2007 3:34 pm Post subject: Dual Ignition |
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You are simply wrong about magnetos. They are one of the simplest
devices going. Yes, they need to be set up correctly, but that is
something than any fresh A&P should be able to do. They may not have the
training and jigs to do the internal overhaul work, but that isn't
needed more than once every 500 hours on all but the meanest
turbocharged beasts. In fact, most good mags will run 1000 hours with no
more than one or two tweaks of the timing, even though they should be
checked at 500. For something with points arcing multiple times a
revolution, that is pretty good. A new or freshly overhauled mag needs
no more than minor care to get installed at the right angle, quick
setting with a buzz box, and they are good for hundreds of hours. I'm
100% certain I can install both mags on an engine and have them ready to
go before you get your electronic gizmos hooked up. And the mags will
keep right on firing whether you have electrics or not, unlike a lot of
electronic systems. Yes, I know about the P-mag. How many 6 cylinder
copies are shipped at this point?
KM
A&P/IA
Ernest Christley wrote:
| Quote: |
<echristley(at)nc.rr.com>
Richard, the fact that the mags require "regular maintenance" and
"proper setup" by someone stricken with OCD to work as you describe is
the classical definition of unreliable. You can't 'rely' on the
average hack with wet ink on his A&P license to set it correctly, and
the fact that it needs to be done so often means the hack will be
doing it or you will be. The electronic ignitions are not nearly as
reliant on special training or fine attention to installation and
maintenance details. You plug it in, and if it works, it works as
designed.
The fact that the HKS700E was designed to have a significant drop on
one ignition is a red herring. That could have easily been designed
in on purpose so that you would have a definite reassurance that both
are working after the mag check.
The mag is a complicated electromechanical device that is a
masterpiece of engineering. But they are not reliable. Else, why do
you carry two of them around, and why do you check both of them just
before takeoff on every flight?
Richard Girard wrote:
> Peter, Upon what data does your statement, "the average mag is
> horribly unreliable", come from? Properly setup and serviced, quite
> the opposite is true, in my experience. Also your statement that the
> dual ignition is required by jug size is questionable, too.
> Last year while in class to get my LSA repairman maintenance ticket I
> set the up two Slick mags to go into an A75. I set the internal
> timing of the mags so that it was dead on for both, and the engine
> timing the same. The instructor was on the verge of accusing me of
> having OCD as I checked and rechecked until I was satisfied it was as
> close as I could get it. When I was finally satisfied, we pulled the
> plane out to the ramp and started it up. After it was up to operating
> temp I did a mag check. It scared the wits out of me when I got NO
> mag drop. Now the EIS installed on the plane only read in 10 RPM
> increments, so there may have been some drop, but the instrument
> didn't read it and I could neither hear it, nor feel it in the seat
> of my pants. I thought sure I had installed the P leads improperly
> and was ready to use the fuel valve to shut the engine down when the
> instructor stepped in, checked all the connections and pronounced
> them good. I did a second mag check, and still got no detectable
> drop. I pulled the throttle back to idle, closed both mag switches
> and the engine died just as it should. What gives, I always gotten
> some drop on every plane I've ever been in. We pulled out the
> continuity checker and went over the P leads again. Everything was as
> it should be. Restarted the engine, established 1700 RPM and checked
> again. NO drop. Shut down the left mag, let the engine run for a bit
> and shut down the right mag. The engine died. Restarted, shut down
> the right mag and let the engine run. Again, NO mag drop. Killed the
> left mag, engine died. I'm sure the WTFO expression on my face begged
> an explanation. The instructor, whose list of certs look like
> alphabet soup gone mad, said it's simple really. It's a very low time
> engine (his personal E-AB aircraft, by the way) and the students in
> the class had set everything up as near perfect as was humanly
> possible, hence no discernible mag drop. He recounted how many a long
> faced pilot, discouraged by the $2000 quote for parts and labor from
> another shop has become his loyal customer when a new set of points
> and careful setting of internal mag timing and engine timing has
> restored the mags to proper working order for less than a 1/4 of the
> original estimate.
> Now lets take the other end of the spectrum. I have and HKS700E
> engine on my trike. It's got 40 hours on it. My OCD tendencies when
> it comes to engine variables is as active as ever. It has dual CDI's
> for each of its two diminutive 350cc cylinders. My first "mag" check
> was a real upholstery clincher. I did the check at 3000 RPM and each
> system showed a 500 RPM drop. Needless to say I was in a near panic
> getting to the manuals before I called the importer. Under ignition
> check it said, "engine shouldn't die"! It's taken a bit to get used
> to, but that's the way the little engine is designed. It runs like
> the proverbial sewing machine, otherwise.
> My point is, engine design, system integration, and proper setup has
> much more to do with ignition system performance than reliance on
> OWT's about "horribly unreliable" claims.
>
> Rick
|
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_________________
Kelly McMullen
A&P/IA, EAA Tech Counselor # 5286
KCHD |
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khorton01(at)rogers.com
Guest
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| Posted: Mon Sep 24, 2007 4:03 pm Post subject: Dual Ignition |
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I agree that individual magnetos are not that reliable, but when
installed in a pair they do provide a reliable source of ignition.
I'm aware of at least two cases where an aircraft with electronic
ignition systems had a forced landing due to loss of ignition, or
improper functioning of the ignition system. So much for modern,
more reliable ignition systems.
Can anyone point me at an occurence where an aircraft with dual
magnetos had a power loss due to ignition system problems?
Kevin Horton
On 24 Sep 2007, at 09:20, Ernest Christley wrote:
| Quote: |
<echristley(at)nc.rr.com>
Richard, the fact that the mags require "regular maintenance" and
"proper setup" by someone stricken with OCD to work as you describe
is the classical definition of unreliable. You can't 'rely' on the
average hack with wet ink on his A&P license to set it correctly,
and the fact that it needs to be done so often means the hack will
be doing it or you will be. The electronic ignitions are not
nearly as reliant on special training or fine attention to
installation and maintenance details. You plug it in, and if it
works, it works as designed.
The fact that the HKS700E was designed to have a significant drop
on one ignition is a red herring. That could have easily been
designed in on purpose so that you would have a definite
reassurance that both are working after the mag check.
The mag is a complicated electromechanical device that is a
masterpiece of engineering. But they are not reliable. Else, why
do you carry two of them around, and why do you check both of them
just before takeoff on every flight?
Richard Girard wrote:
> Peter, Upon what data does your statement, "the average mag is
> horribly unreliable", come from? Properly setup and serviced,
> quite the opposite is true, in my experience. Also your statement
> that the dual ignition is required by jug size is questionable, too.
> Last year while in class to get my LSA repairman maintenance
> ticket I set the up two Slick mags to go into an A75. I set the
> internal timing of the mags so that it was dead on for both, and
> the engine timing the same. The instructor was on the verge of
> accusing me of having OCD as I checked and rechecked until I was
> satisfied it was as close as I could get it. When I was finally
> satisfied, we pulled the plane out to the ramp and started it up.
> After it was up to operating temp I did a mag check. It scared the
> wits out of me when I got NO mag drop. Now the EIS installed on
> the plane only read in 10 RPM increments, so there may have been
> some drop, but the instrument didn't read it and I could neither
> hear it, nor feel it in the seat of my pants. I thought sure I had
> installed the P leads improperly and was ready to use the fuel
> valve to shut the engine down when the instructor stepped in,
> checked all the connections and pronounced them good. I did a
> second mag check, and still got no detectable drop. I pulled the
> throttle back to idle, closed both mag switches and the engine
> died just as it should. What gives, I always gotten some drop on
> every plane I've ever been in. We pulled out the continuity
> checker and went over the P leads again. Everything was as it
> should be. Restarted the engine, established 1700 RPM and checked
> again. NO drop. Shut down the left mag, let the engine run for a
> bit and shut down the right mag. The engine died. Restarted, shut
> down the right mag and let the engine run. Again, NO mag drop.
> Killed the left mag, engine died. I'm sure the WTFO expression on
> my face begged an explanation. The instructor, whose list of certs
> look like alphabet soup gone mad, said it's simple really. It's a
> very low time engine (his personal E-AB aircraft, by the way) and
> the students in the class had set everything up as near perfect as
> was humanly possible, hence no discernible mag drop. He recounted
> how many a long faced pilot, discouraged by the $2000 quote for
> parts and labor from another shop has become his loyal customer
> when a new set of points and careful setting of internal mag
> timing and engine timing has restored the mags to proper working
> order for less than a 1/4 of the original estimate.
> Now lets take the other end of the spectrum. I have and HKS700E
> engine on my trike. It's got 40 hours on it. My OCD tendencies
> when it comes to engine variables is as active as ever. It has
> dual CDI's for each of its two diminutive 350cc cylinders. My
> first "mag" check was a real upholstery clincher. I did the check
> at 3000 RPM and each system showed a 500 RPM drop. Needless to say
> I was in a near panic getting to the manuals before I called the
> importer. Under ignition check it said, "engine shouldn't die"!
> It's taken a bit to get used to, but that's the way the little
> engine is designed. It runs like the proverbial sewing machine,
> otherwise.
> My point is, engine design, system integration, and proper setup
> has much more to do with ignition system performance than reliance
> on OWT's about "horribly unreliable" claims.
>
> Rick
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list(at)toddheffley.com
Guest
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| Posted: Tue Sep 25, 2007 9:27 am Post subject: Dual Ignition |
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Hope this is not a red harring to the discussion...
My Favorite dual ignition setup is a Cessna 195.
It has a standard Kettering/Distributor as one system and a standard
aircraft mag (no mechanical advance) as the other system.
Both systems have severe limitations.
The distrubutor does not work if ANYTHING fails the aircraft
electrical system..... but it starts the engine great.
The mag WILL NOT start the engine because it has no impulse, But it is
reliable (self supporting) when the engine is running.
The value seems to be wildly different failure modes, thus decreasing
the chance of a single TYPE of failure leading to a quiet engine.
Rather than "My mag switch is better than your mag switch", how about
reliability though diversity?
I have a maintenance background, not a build background, so my two
cents is worth just that.
Do not archive.
todd
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frank.hinde(at)hp.com
Guest
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| Posted: Tue Sep 25, 2007 10:02 am Post subject: Dual Ignition |
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Yes but you need to delve a little deeper to understand the situation
with the dual ignition. An unfortunate failure mode that happened on two
A/C appeared to be ONE of the ignitions losing its timing on a P
mag...I.e going waay too advanced.
When this happens the other ignition although firing normally will have
no effect, the effective timing will be very adavnced and the engine can
detonate as happened with the two RV's running Pmags (I know cus mine
was one of them). This is not a dual failure however and could be argued
the pilots should have shut one of the units down to bring the timing
back under control....Ok I'll remember next time.
Standard mags do not genearlly have this particular failure mode but my
instructor did tell me about one some years back when a mag slipped in
its housing.
It seems that Emagair have now resolved this problem.
As long as the EI's are wired independantly they should be more reliable
and longer lasting than mags. Certainly if you wire both EI's from a
single fuse then you might as well start playing Russian roulette, but I
think with the above two proviso's dual Eis are a pretty bullet proof
setup.
Frank
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rv9jim(at)juno.com
Guest
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| Posted: Tue Sep 25, 2007 11:44 am Post subject: Dual Ignition |
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Hi Todd,
Your right on the ignition systems on the C195. The only
drawback was when water got into the distributor and shorted the system.
I had a 1950A model. One of the mods you needed to do was to drill a
small hole in the bottom of the distributor in the lowest part to drain
any accumulation of water from the distributor. Yes, it started nicely
on the point style ignition as long as there was good battery power. It
is still a great plane but at 15 gph ( 80 gal tanks) and one quart of
oil, it would be a bit expensive to operate today.
Jim
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