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Looigi
Joined: 20 Apr 2015
Posts: 81
Location: Christchurch, New Zealand
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 Posted: Sat Feb 17, 2018 8:14 pm Post subject: Engine stumble in flight |
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I thought I would consult the Oracle before I rip into pulling things apart.
One of the boys was flying the Yak today and he had a bit of a scare. He was cruising at about 800’, 70% RPM and 700mm manifold pressure when the engine stopped running for 1-2 seconds. When the engine started again, there was lots of smoke out the exhaust. He continued with his flight, but when it happened again he returned and landed safely.
I had him do a run up and the mag drops were fine, oil level was normal and the engine ran fine. I am suspecting a fuel issue?
He said however that the engine had been harder to start (slow to turn over) on the last couple of flights - I am thinking that this is a seperate problem though.
Any thoughts?
Chris
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jbsoar(at)gmail.com
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| Posted: Sat Feb 17, 2018 8:47 pm Post subject: Engine stumble in flight |
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1-2 seconds is an eternity. An ignition problem would be quite possible. Does this aircraft have the auto plug conversion?
On Sat, Feb 17, 2018 at 10:14 PM, Looigi <cdoburton(at)gmail.com (cdoburton(at)gmail.com)> wrote:
| Quote: | --> Yak-List message posted by: "Looigi" <cdoburton(at)gmail.com (cdoburton(at)gmail.com)>
I thought I would consult the Oracle before I rip into pulling things apart.
One of the boys was flying the Yak today and he had a bit of a scare. He was cruising at about 800’, 70% RPM and 700mm manifold pressure when the engine stopped running for 1-2 seconds. When the engine started again, there was lots of smoke out the exhaust. He continued with his flight, but when it happened again he returned and landed safely.
I had him do a run up and the mag drops were fine, oil level was normal and the engine ran fine. I am suspecting a fuel issue?
He said however that the engine had been harder to start (slow to turn over) on the last couple of flights - I am thinking that this is a seperate problem though.
Any thoughts?
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478062#478062
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sat Feb 17, 2018 9:10 pm Post subject: Engine stumble in flight |
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You have a bad mag coil. Happens about 15 to 20 minutes into the flight. Sudden engine stoppage with belching of unburned fuel in the supercharger as it misfires followed by normal engine for a short time. No mag drop on the ground. Think Doug Sapp still has some new mag coils in stock.
Doc
Sent from my iPad
| Quote: | On Feb 17, 2018, at 10:14 PM, Looigi <cdoburton(at)gmail.com> wrote:
I thought I would consult the Oracle before I rip into pulling things apart.
One of the boys was flying the Yak today and he had a bit of a scare. He was cruising at about 800’, 70% RPM and 700mm manifold pressure when the engine stopped running for 1-2 seconds. When the engine started again, there was lots of smoke out the exhaust. He continued with his flight, but when it happened again he returned and landed safely.
I had him do a run up and the mag drops were fine, oil level was normal and the engine ran fine. I am suspecting a fuel issue?
He said however that the engine had been harder to start (slow to turn over) on the last couple of flights - I am thinking that this is a seperate problem though.
Any thoughts?
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478062#478062
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Looigi
Joined: 20 Apr 2015
Posts: 81
Location: Christchurch, New Zealand
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| Posted: Sat Feb 17, 2018 9:32 pm Post subject: Re: Engine stumble in flight |
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Thanks Doc, I was wondering about that. Is there any way to test for this? I would like to confirm the fault, or at least which one it is. Or is it the tried and true shotgun method?
No, Old school Russian plugs.
Cheers
Chris
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jbsoar(at)gmail.com
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| Posted: Sat Feb 17, 2018 9:49 pm Post subject: Engine stumble in flight |
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This may be a coil problem. But having one coil fail would cause the engine to lose a slight bit of power, as if one grounded one magneto.Replacing the coils on both mags would likely cure this problem.
The auto plug conversion is worthwhile. The engine will run better.
On Sat, Feb 17, 2018 at 11:32 PM, Looigi <cdoburton(at)gmail.com (cdoburton(at)gmail.com)> wrote:
| Quote: | --> Yak-List message posted by: "Looigi" <cdoburton(at)gmail.com (cdoburton(at)gmail.com)>
Thanks Doc, I was wondering about that. Is there any way to test for this? I would like to confirm the fault, or at least which one it is. Or is it the tried and true shotgun method?
No, Old school Russian plugs.
Cheers
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478069#478069
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FORUMS -
eferrer" target="_blank">http://forums.matronics.com
====================================
WIKI -
errer" target="_blank">http://wiki.matronics.com
====================================
b Site -
-Matt Dralle, List Admin.
rel="noreferrer" target="_blank">http://www.matronics.com/contribution
====================================
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jackpot
Joined: 13 Jul 2010
Posts: 65
Location: Las Vegas, Nevada
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| Posted: Sat Feb 17, 2018 10:27 pm Post subject: Engine stumble in flight |
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Russian plugs work just fine. Check the mag point gap. I had that problem and it turned out the gap had been set to wide. Make sure not to use 1000th of an inch. But make sure you use the metric gap specified in the manual. That is a good place to start. It will occasionally miss and stumble. If a coil goes it is usually dead. Good hunting. Gary. CJ. N22YK. LAS
On Feb 17, 2018, at 21:48, John B <jbsoar(at)gmail.com (jbsoar(at)gmail.com)> wrote:
| Quote: | This may be a coil problem. But having one coil fail would cause the engine to lose a slight bit of power, as if one grounded one magneto.Replacing the coils on both mags would likely cure this problem.
The auto plug conversion is worthwhile. The engine will run better.
On Sat, Feb 17, 2018 at 11:32 PM, Looigi <cdoburton(at)gmail.com (cdoburton(at)gmail.com)> wrote:
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richard.goode(at)russiana
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| Posted: Sun Feb 18, 2018 1:26 am Post subject: Engine stumble in flight |
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Not correct, I'm afraid! For reasons that I can't explain, a failing coil in one magneto will cause the whole engine to "stumble", and indeed when seriously deteriorated, will cause the engine to completely stop for a short time, which can be extremely disconcerting. We have seen this on a number of aircraft!
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of John B
Sent: 18 February 2018 05:48
To: Yak-List Digest Server <yak-list(at)matronics.com>
Subject: Re: Re: Engine stumble in flight
This may be a coil problem. But having one coil fail would cause the engine to lose a slight bit of power, as if one grounded one magneto.
Replacing the coils on both mags would likely cure this problem.
The auto plug conversion is worthwhile. The engine will run better.
On Sat, Feb 17, 2018 at 11:32 PM, Looigi <cdoburton(at)gmail.com (cdoburton(at)gmail.com)> wrote:
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This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
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dsavarese0812(at)bellsout
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| Posted: Sun Feb 18, 2018 4:48 am Post subject: Engine stumble in flight |
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A coil that is failing in flight typically occurs between 20 and 40 minutes of flight, depending on the outside air temperature. When a coil does fail in flight, it is due to heat breakdown. Termikas did some testing in a heat chamber with a fulling operational magneto with a questionable coil. The heat in the heat chamber was continually increased as the magneto was operating. At 60 degrees C, the questionable coil began to fail. The test fixture and heat chamber was configured to display all 9 spark outputs as they occurred. Once the coil reached 60 degrees C, we could see the display becoming intermittent and as the heat built up even further, one could see the coil go into complete failure.
A single coil failing in flight will virtually shut the engine down for "one heartbeat"; YOUR heart beat, and then pick up rpm again. Sometimes an exhaust pop can be heard and ;during a formation flight, I personally have seen a short puff of smoke out of one exhaust stack when the pilot of the aircraft with the suspected coil problem, was saying "it happened again".
Two ways to identify which magneto coil is failing:
- In the air, when you first feel the engine "shut down for one heart beat", do a mag check but leave the mag on one mag to see if that mag coil is failing. If the engine continues to run smooth, switch to the other mag and let the engine run on that mag.
- On the ground, you must run the engine with the cooling louvers closed until the CHT is well over 200C. What you're trying to do is build up the heat under the cowl so the suspect coil will eventually begin to fail. Once the coil starts to act up, switch to one mag and see if the misfiring is on that mag. If not, run it on the other mag. Believe me, if you have a bad coil, it WILL show up on the ground if you get the engine hot enough.
Dennis
From: Looigi <cdoburton(at)gmail.com>
To: yak-list(at)matronics.com
Sent: Sunday, February 18, 2018 12:34 AM
Subject: Re: Engine stumble in flight
--> Yak-List message posted by: "Looigi" <cdoburton(at)gmail.com (cdoburton(at)gmail.com)>
Thanks Doc, I was wondering about that. Is there any way to test for this? I would like to confirm the fault, or at least which one it is. Or is it the tried and true shotgun method?
No, Old school Russian plugs.
Cheers
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478069#478069
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Vic
Joined: 12 Aug 2008
Posts: 116
Location: Southern Bavaria
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| Posted: Sun Feb 18, 2018 6:33 am Post subject: Re: Engine stumble in flight |
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We had quite some troubles with bad/new coils in past years and this took some time to find out all sides of the problem. Since we do a mag run up AFTER most flights after clearing the runway and have min. 70 percent , better 80 percent revs to get a reliable check of ignition system.
I built my own heat chamber and did 5 hour runs at min. 70 degrees C to test coil and capacitor. Remember, the alu foil capacitor is wound between primary and secondary windings within the coil - the worst place to put a capacitor. My guess is that the dielectric material and materials in the coil wires may age and since the electrical properties of components will become unsuitable to operate.
Why do we NOT see the same hiccup of the engine when we do the mag check on the ground , switching off one mag, compared to a short failure in flight ??? I just cannot figure that out . . .
Vic
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sun Feb 18, 2018 9:26 am Post subject: Engine stumble in flight |
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As Dennis said. I was one of the ones that Dennis observed having the inflight mag failure. I did an inflight mag check to find the bad coil. Not so excited about heating the engine up on the ground to above 200C but it can be done.
Altitude is your friend when doing the airborne mag check.
Doc
Sent from my iPad
| Quote: | On Feb 17, 2018, at 11:32 PM, Looigi <cdoburton(at)gmail.com> wrote:
Thanks Doc, I was wondering about that. Is there any way to test for this? I would like to confirm the fault, or at least which one it is. Or is it the tried and true shotgun method?
No, Old school Russian plugs.
Cheers
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478069#478069
|
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sun Feb 18, 2018 9:29 am Post subject: Engine stumble in flight |
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Having personally experienced it on three occasions it does shut the "Whole" engine down for a heartbeat. Then it comes back up like nothing happened.
Doc
Sent from my iPad
On Feb 18, 2018, at 3:24 AM, Richard Goode <richard.goode(at)russianaeros.com (richard.goode(at)russianaeros.com)> wrote:
| Quote: | <![endif]--> <![endif]-->
Not correct, I'm afraid! For reasons that I can't explain, a failing coil in one magneto will cause the whole engine to "stumble", and indeed when seriously deteriorated, will cause the engine to completely stop for a short time, which can be extremely disconcerting. We have seen this on a number of aircraft!
Richard Goode Aerobatics
Rhodds Farm
Lyonshall
Hereford
HR5 3LW
Tel: +44 (0) 1544 340120
Fax: +44 (0) 1544 340129
www.russianaeros.com
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of John B
Sent: 18 February 2018 05:48
To: Yak-List Digest Server <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Subject: Re: Re: Engine stumble in flight
This may be a coil problem. But having one coil fail would cause the engine to lose a slight bit of power, as if one grounded one magneto.
Replacing the coils on both mags would likely cure this problem.
The auto plug conversion is worthwhile. The engine will run better.
On Sat, Feb 17, 2018 at 11:32 PM, Looigi <cdoburton(at)gmail.com (cdoburton(at)gmail.com)> wrote:
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This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
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cjpilot710(at)aol.com
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| Posted: Sun Feb 18, 2018 6:16 pm Post subject: Engine stumble in flight |
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This happened to me numberer of years ago. I was chasing the problem for quite a while., when on the way to OSH over Americus Ga. it really gave me a scare. Landing there a local kid who worked on crop dusters figured that my harness was breaking down. Doing a high tension test it turned out a least 3 plug wires were bad. I noted you said that you use Russian plugs which means that you more than likely have original ignition harness. Age will cause the wires insulation to break down and you get cross firing. I changed to Dennis's auto conversion and have not had that problem since. Its an easy conversion and much cheaper in the long run. Suggest you have the harness tested. Willing to bet that's your problem.
Jim "Pappy" Goolsby
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wlannon(at)shaw.ca
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| Posted: Mon Feb 19, 2018 9:26 pm Post subject: Engine stumble in flight |
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I have a really hard time accepting that a coil failure in one mag. can
cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power
& mag. check on a 1340 with American Bosch mags. Went dead as a doornail on
that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two
different aircraft & engines, x-country at around 7500 ft. throttle fully
open trying to maintain about 65% power, mixture up to throttle (max. lean).
Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as
lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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jbsoar(at)gmail.com
Guest
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| Posted: Mon Feb 19, 2018 11:13 pm Post subject: Engine stumble in flight |
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A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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j.mevis(at)computer.org
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| Posted: Tue Feb 20, 2018 1:43 am Post subject: Engine stumble in flight |
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A coil failure is not simply having the mag grounded or turning it off.
Those who have witnessed it in flight will agree: it makes your heart beat “stumble” too (it did when I witnessed it).
As far as I know there’s still no scientific explanation of what happens exactly.
The problem with old coils is that the solvents used for applying the insulation, are vapoured out.
Some tiny holes exist in the insulation material.
If humidity gets in, then at higher temperature the gases in the holes ionize and cause a high-tension brake through.
I have a hunch (a guestimate) that the bad coil fires when it shouldn’t fire.
But once again, I am not sure at all.
Anyway, bad coils is a serious problem.
Only my 2 cents,
Jan
From: <owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)> on behalf of John B <jbsoar(at)gmail.com (jbsoar(at)gmail.com)>
Reply-To: "yak-list(at)matronics.com (yak-list(at)matronics.com)" <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Date: Tuesday, 20 February 2018 at 08:12
To: "yak-list(at)matronics.com (yak-list(at)matronics.com)" <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Subject: Re: Re: Engine stumble in flight
A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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Richard.goode(at)russiana
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| Posted: Tue Feb 20, 2018 2:29 am Post subject: Engine stumble in flight |
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I'm sorry, but that is not correct! But over the last 25 years, I have experienced coil problems on at least as many aircraft. Logic will tell you that a coil failure in one magneto will leave the engine running perfectly well on the other magneto with a slight power loss. The practicality is different, and the engine will stop totally if the coil failure is serious. Of course it will then restart, but enough to give the pilot, and indeed any passengers, a fright.
Our own view is that, as has been said, the magneto gets very hot in operation. And of course the coil is inside, and worse still, the capacitor is inside the coil, which is intrinsically getting hot with the current going through the coil. In order to partially overcome this problem, we have developed coils with an external capacitor which will run rather cooler, and have had very satisfactory results with them. The capacitor is small; bonded to the outside of the coil and makes no difference to installation of the coil inside the magneto.
Richard Goode
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of John B
Sent: 20 February 2018 07:13
To: Yak-List Digest Server <yak-list(at)matronics.com>
Subject: Re: Re: Engine stumble in flight
A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:[quote]
--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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Ernie
Joined: 11 Jan 2006
Posts: 513
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| Posted: Tue Feb 20, 2018 6:44 am Post subject: Engine stumble in flight |
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Wrong
On Tue, Feb 20, 2018 at 5:28 AM, Richard Goode <Richard.goode(at)russianaeros.com (Richard.goode(at)russianaeros.com)> wrote:
[quote]
I'm sorry, but that is not correct! But over the last 25 years, I have experienced coil problems on at least as many aircraft. Logic will tell you that a coil failure in one magneto will leave the engine running perfectly well on the other magneto with a slight power loss. The practicality is different, and the engine will stop totally if the coil failure is serious. Of course it will then restart, but enough to give the pilot, and indeed any passengers, a fright.
Our own view is that, as has been said, the magneto gets very hot in operation. And of course the coil is inside, and worse still, the capacitor is inside the coil, which is intrinsically getting hot with the current going through the coil. In order to partially overcome this problem, we have developed coils with an external capacitor which will run rather cooler, and have had very satisfactory results with them. The capacitor is small; bonded to the outside of the coil and makes no difference to installation of the coil inside the magneto.
Richard Goode
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of John B
Sent: 20 February 2018 07:13
To: Yak-List Digest Server <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Subject: Re: Re: Engine stumble in flight
A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]
--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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jbsoar(at)gmail.com
Guest
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| Posted: Tue Feb 20, 2018 6:44 am Post subject: Engine stumble in flight |
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It seems the problem is difficult to define... Would cooling air blast tubes to each magneto help? We in the West are likely running these engines at higher ambient temperatures than they were in Russia. One could drill a hole in each magneto cover, in the area of the coil, and duct filtered air to the coil, but what happens when one flies in the rain?
On Tue, Feb 20, 2018 at 3:42 AM, Jan Mevis <j.mevis(at)computer.org (j.mevis(at)computer.org)> wrote:
[quote]A coil failure is not simply having the mag grounded or turning it off.
Those who have witnessed it in flight will agree: it makes your heart beat “stumble” too (it did when I witnessed it).
As far as I know there’s still no scientific explanation of what happens exactly.
The problem with old coils is that the solvents used for applying the insulation, are vapoured out.
Some tiny holes exist in the insulation material.
If humidity gets in, then at higher temperature the gases in the holes ionize and cause a high-tension brake through.
I have a hunch (a guestimate) that the bad coil fires when it shouldn’t fire.
But once again, I am not sure at all.
Anyway, bad coils is a serious problem.
Only my 2 cents,
Jan
From: <owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)> on behalf of John B <jbsoar(at)gmail.com (jbsoar(at)gmail.com)>
Reply-To: "yak-list(at)matronics.com (yak-list(at)matronics.com)" <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Date: Tuesday, 20 February 2018 at 08:12
To: "yak-list(at)matronics.com (yak-list(at)matronics.com)" <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Subject: Re: Re: Engine stumble in flight
A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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pa3arw(at)ziggo.nl
Guest
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| Posted: Tue Feb 20, 2018 7:54 am Post subject: Engine stumble in flight |
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What do you mean “wrong”…are you doubting on what Richard said?
Apparantly you must have a lot more experience with this phenomena…..lol.
Hans O.
Van: <owner-yak-list-server(at)matronics.com> namens Ernest Martinez <erniel29(at)gmail.com>
Beantwoorden - Aan: <yak-list(at)matronics.com>
Datum: dinsdag 20 februari 2018 om 15:43
Aan: yak-list <yak-list(at)matronics.com>
Onderwerp: Re: Re: Engine stumble in flight
Wrong
On Tue, Feb 20, 2018 at 5:28 AM, Richard Goode <Richard.goode(at)russianaeros.com (Richard.goode(at)russianaeros.com)> wrote:[quote]
I'm sorry, but that is not correct! But over the last 25 years, I have experienced coil problems on at least as many aircraft. Logic will tell you that a coil failure in one magneto will leave the engine running perfectly well on the other magneto with a slight power loss. The practicality is different, and the engine will stop totally if the coil failure is serious. Of course it will then restart, but enough to give the pilot, and indeed any passengers, a fright.
Our own view is that, as has been said, the magneto gets very hot in operation. And of course the coil is inside, and worse still, the capacitor is inside the coil, which is intrinsically getting hot with the current going through the coil. In order to partially overcome this problem, we have developed coils with an external capacitor which will run rather cooler, and have had very satisfactory results with them. The capacitor is small; bonded to the outside of the coil and makes no difference to installation of the coil inside the magneto.
Richard Goode
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of John B
Sent: 20 February 2018 07:13
To: Yak-List Digest Server <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Subject: Re: Re: Engine stumble in flight
A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]
--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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Ernie
Joined: 11 Jan 2006
Posts: 513
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| Posted: Tue Feb 20, 2018 8:03 am Post subject: Engine stumble in flight |
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I was agreeing with Richard. I didn't see his response before I hit send
On Tue, Feb 20, 2018 at 10:53 AM, Hans Oortman <pa3arw(at)ziggo.nl (pa3arw(at)ziggo.nl)> wrote:
[quote]
What do you mean “wrong”…are you doubting on what Richard said?
Apparantly you must have a lot more experience with this phenomena…..lol.
Hans O.
Van: <owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)> namens Ernest Martinez <erniel29(at)gmail.com (erniel29(at)gmail.com)>
Beantwoorden - Aan: <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Datum: dinsdag 20 februari 2018 om 15:43
Aan: yak-list <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Onderwerp: Re: Re: Engine stumble in flight
Wrong
On Tue, Feb 20, 2018 at 5:28 AM, Richard Goode <Richard.goode(at)russianaeros.com (Richard.goode(at)russianaeros.com)> wrote:[quote]
I'm sorry, but that is not correct! But over the last 25 years, I have experienced coil problems on at least as many aircraft. Logic will tell you that a coil failure in one magneto will leave the engine running perfectly well on the other magneto with a slight power loss. The practicality is different, and the engine will stop totally if the coil failure is serious. Of course it will then restart, but enough to give the pilot, and indeed any passengers, a fright.
Our own view is that, as has been said, the magneto gets very hot in operation. And of course the coil is inside, and worse still, the capacitor is inside the coil, which is intrinsically getting hot with the current going through the coil. In order to partially overcome this problem, we have developed coils with an external capacitor which will run rather cooler, and have had very satisfactory results with them. The capacitor is small; bonded to the outside of the coil and makes no difference to installation of the coil inside the magneto.
Richard Goode
From: owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com) [mailto:owner-yak-list-server(at)matronics.com (owner-yak-list-server(at)matronics.com)] On Behalf Of John B
Sent: 20 February 2018 07:13
To: Yak-List Digest Server <yak-list(at)matronics.com (yak-list(at)matronics.com)>
Subject: Re: Re: Engine stumble in flight
A coil failure in a magneto will feel the same as simply grounding the mag, or turning the mag "off." In other words, a coil failure with both mags "on" or "not grounded," will feel like nothing, other than, say, a five percent loss of performance. It won't cause a total engine failure. However, it is entirely possible for both magnetos to have intermittently failing coils. One is tired, and the other quits when it gets hot, so the engine stumbles, terrifying the pilot and passenger. The brief engine stumble rattles the coil enough for it to correct it's internal short, and the engine smooths out. Or, one has a spark plug wire problem on one mag, and a failing coil on the other. The engine runs fine, until it gets good and hot and the coil associated with the good spark plug wires fails. Terrifying!
Magnetos get very hot in use. Has anyone fashioned dedicated cooling blast tubes to the magnetos? What does the Sukhoi use, if anything?
We did the auto plug conversion, and immediately were rewarded with a better running engine. The auto plug conversion will reduce the weight of your airplane by a couple of pounds, which is also of benefit. The cost of the kit is nominal.
On Mon, Feb 19, 2018 at 11:26 PM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
[quote]
--> Yak-List message posted by: "Walter Lannon" <wlannon(at)shaw.ca (wlannon(at)shaw.ca)>
I have a really hard time accepting that a coil failure in one mag. can cause the other mag to fail.
Have had only one definite coil failure. Occurred during pre-flight power & mag. check on a 1340 with American Bosch mags. Went dead as a doornail on that one but other just fine. New coil installed and back to normal.
Have had two instances of the Huosai wake up call (2 sec. of silence). Two different aircraft & engines, x-country at around 7500 ft. throttle fully open trying to maintain about 65% power, mixture up to throttle (max. lean). Maybe too lean!
Since then with a large throttle opening at altitude I don't go quite as lean and have not (so far) had a recurrence.
Don't know for sure but???????
Walt
--
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