Today's Message Index:
----------------------
1. 03:01 AM - Re: Re: Engine stumble in flight (A. Dennis Savarese)
2. 08:10 AM - Yak 50 for sale (GreasySideUp)
3. 08:12 AM - Re: Yak 50 for sale (GreasySideUp)
4. 08:44 AM - Re: Yak 50 for sale (William Geipel)
5. 09:22 AM - Re: Yak 50 for sale ()
6. 09:36 AM - Re: Yak 50 for sale (Walter Lannon)
7. 10:03 AM - Re: Yak 50 for sale (William Geipel)
8. 12:43 PM - Re: Engine stumble in flight (Looigi)
9. 10:07 PM - Re: Re: Engine stumble in flight (Walter Lannon)
10. 10:58 PM - Engine stumble (Frank Stelwagon)
11. 11:29 PM - Re: engine stumble (Looigi)
12. 11:30 PM - Re: Re: Engine stumble in flight (Jan Mevis)
Message 1
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| Subject: | Re: Engine stumble in flight |
I seriously doubt there is any possibility of that happening.=C2- George'
s explanation a few days ago is quite accurate regarding what happens when
a coil is failing.Dennis
From: Looigi <cdoburton@gmail.com>
To: yak-list@matronics.com
Sent: Sunday, February 25, 2018 11:04 PM
Subject: Yak-List: Re: Engine stumble in flight
Ok, so to add to the story.....
On Sunday I pulled the two magneto coils out of my machine.=C2-
I did a simple continuity test on the bench with a multimeter across the pr
imary and then the secondary windings of both coils thinking I could at lea
st compare the readings.=C2- The coil from the right magneto tested open
circuit intermittently on the secondary winding.=C2- To be honest I had p
lanned to put them in the oven at home to cook while the War Office was at
work so I wasn't expecting to find a fault so easily.=C2-
I am going to replace the faulty coil tomorrow and see how he goes from the
re.
There are many on here with brains bigger than mine so can I put a theory u
p for comment?
If the coil on my RH mag failed, like it has in the secondary (high tension
) winding, could that send a burst of HT energy down the P lead, and jump t
he terminals of one of the 3 switches in that circuit, back down the LH mag
P lead to the primary winding of the LH magneto coil, disrupting the magne
tic flux of the 'good' mag?
Thoughts??
Chris
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478262#478262
S -
WIKI -
-
=C2- =C2- =C2- =C2- =C2- -Matt Dralle, List Admin.
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My little girl is asking for flying lessons so it is time to trade in the Yak 50
for a Cessna 195. It is offered on Barnstormers with pictures.
1979 Yak 50 N369AG
This is the best performing Yak 50 on the planet. It is a 1979 Flush Riveted model
with nearly every performance and trick mod you can add to a Yak. The spar
was reinforced from the factory. The engine was built with lightweight pistons,
gapless rings and auto plugs and puts out a monstrous 420HP behind an MTV-9,
3 bladed propeller. This plane will hover. The motor and FWF are truly
a work of art. The engine mount, air tank, oil tank, linkage etc. was all powder
coated and looks fantastic. The oil cooler was relocated to the wing, cleaning
up the belly of the aircraft and adding a few knots in cruise. It has a
larger 36 gallon fuel tank, smoke tank with dual exhaust ports, clean kit, oil
shutoff with no start micro switch, new air tank, rebuilt oil pump, new tires,
new batteries, rebuilt gear actuators, Garmin SL40, Becker transponder and
original 360 degree attitude indicator and instruments. I never pulled more than
6 Gs to extend the life of the airframe.
TTAF 338.4
TSMOH 160
TSPOH 160
Annual due March 2019
The paint is an honest 6/10 but it looks great at 10 and perfect when in the air.
The money was spent on the motor, prop and systems. They run 100% mechanically
and are near bullet proof.
https://www.youtube.com/watch?v=lunZ0gVl3JI
This aircraft has unlimited aerobatic capability combined with the warbird aesthetic
and the Red Star Pilot Association for formation clinics and fly ins. The
community and support for this aircraft are awesome and it is something you
wont get with straight aerobatic aircraft. Post flight usually takes an hour
because of all the attention it gets on the ramp. It really does have a fantastic
combination of appeal from several different communities.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478271#478271
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| Subject: | Re: Yak 50 for sale |
A few pics.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478272#478272
Attachments:
http://forums.matronics.com//files/img_0119_125.jpg
http://forums.matronics.com//files/img_1235_148.jpg
http://forums.matronics.com//files/img_1234_143.jpg
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| Subject: | Re: Yak 50 for sale |
A C195 to teach her to fly?
> On Feb 26, 2018, at 09:09, GreasySideUp <greasysideup@hotmail.com> wrote:
>
>
> My little girl is asking for flying lessons so it is time to trade in the Yak
50 for a Cessna 195. It is offered on Barnstormers with pictures.
>
> 1979 Yak 50 N369AG
>
>
>
> This is the best performing Yak 50 on the planet. It is a 1979 Flush Riveted
model with nearly every performance and trick mod you can add to a Yak. The
spar was reinforced from the factory. The engine was built with lightweight pistons,
gapless rings and auto plugs and puts out a monstrous 420HP behind an
MTV-9, 3 bladed propeller. This plane will hover. The motor and FWF are truly
a work of art. The engine mount, air tank, oil tank, linkage etc. was all powder
coated and looks fantastic. The oil cooler was relocated to the wing, cleaning
up the belly of the aircraft and adding a few knots in cruise. It has
a larger 36 gallon fuel tank, smoke tank with dual exhaust ports, clean kit,
oil shutoff with no start micro switch, new air tank, rebuilt oil pump, new tires,
new batteries, rebuilt gear actuators, Garmin SL40, Becker transponder and
original 360 degree attitude indicator and instruments. I never pulled more
than 6 Gs to extend the life of the airframe.
>
>
>
> TTAF 338.4
>
> TSMOH 160
>
> TSPOH 160
>
> Annual due March 2019
>
>
>
> The paint is an honest 6/10 but it looks great at 10 and perfect when in the
air. The money was spent on the motor, prop and systems. They run 100% mechanically
and are near bullet proof.
>
>
>
> https://www.youtube.com/watch?v=lunZ0gVl3JI
>
>
>
> This aircraft has unlimited aerobatic capability combined with the warbird aesthetic
and the Red Star Pilot Association for formation clinics and fly ins.
The community and support for this aircraft are awesome and it is something you
wont get with straight aerobatic aircraft. Post flight usually takes an hour
because of all the attention it gets on the ramp. It really does have a fantastic
combination of appeal from several different communities.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=478271#478271
>
>
>
>
>
>
>
>
>
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Find an instructor who really understands the 195 as they are ground looping witches.
I learned!
Frank N23021
-----Original Message-----
From: owner-yak-list-server@matronics.com [mailto:owner-yak-list-server@matronics.com] On Behalf Of William Geipel
Sent: Monday, February 26, 2018 8:43 AM
Subject: Re: Yak-List: Yak 50 for sale
A C195 to teach her to fly?
> On Feb 26, 2018, at 09:09, GreasySideUp <greasysideup@hotmail.com> wrote:
>
> --> <greasysideup@hotmail.com>
>
> My little girl is asking for flying lessons so it is time to trade in the Yak
50 for a Cessna 195. It is offered on Barnstormers with pictures.
>
> 1979 Yak 50 N369AG
>
>
>
> This is the best performing Yak 50 on the planet. It is a 1979 Flush Riveted
model with nearly every performance and trick mod you can add to a Yak. The
spar was reinforced from the factory. The engine was built with lightweight pistons,
gapless rings and auto plugs and puts out a monstrous 420HP behind an
MTV-9, 3 bladed propeller. This plane will hover. The motor and FWF are truly
a work of art. The engine mount, air tank, oil tank, linkage etc. was all powder
coated and looks fantastic. The oil cooler was relocated to the wing, cleaning
up the belly of the aircraft and adding a few knots in cruise. It has
a larger 36 gallon fuel tank, smoke tank with dual exhaust ports, clean kit,
oil shutoff with no start micro switch, new air tank, rebuilt oil pump, new tires,
new batteries, rebuilt gear actuators, Garmin SL40, Becker transponder and
original 360 degree attitude indicator and instruments. I never pulled more
than 6 Gs to extend the life of the airframe.
>
>
>
> TTAF 338.4
>
> TSMOH 160
>
> TSPOH 160
>
> Annual due March 2019
>
>
>
> The paint is an honest 6/10 but it looks great at 10 and perfect when in the
air. The money was spent on the motor, prop and systems. They run 100% mechanically
and are near bullet proof.
>
>
>
> https://www.youtube.com/watch?v=lunZ0gVl3JI
>
>
>
> This aircraft has unlimited aerobatic capability combined with the warbird aesthetic
and the Red Star Pilot Association for formation clinics and fly ins.
The community and support for this aircraft are awesome and it is something you
wont get with straight aerobatic aircraft. Post flight usually takes an hour
because of all the attention it gets on the ramp. It really does have a fantastic
combination of appeal from several different communities.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=478271#478271
>
>
>
>
>
>
>
>
>
---
This email has been checked for viruses by AVG.
http://www.avg.com
Message 6
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| Subject: | Re: Yak 50 for sale |
a c195 Trainer? You are joking of course.
-----Original Message-----
From: GreasySideUp
Sent: Monday, February 26, 2018 8:09 AM
Subject: Yak-List: Yak 50 for sale
My little girl is asking for flying lessons so it is time to trade in the
Yak 50 for a Cessna 195. It is offered on Barnstormers with pictures.
1979 Yak 50 N369AG
This is the best performing Yak 50 on the planet. It is a 1979 Flush
Riveted model with nearly every performance and trick mod you can add to a
Yak. The spar was reinforced from the factory. The engine was built with
lightweight pistons, gapless rings and auto plugs and puts out a monstrous
420HP behind an MTV-9, 3 bladed propeller. This plane will hover. The
motor and FWF are truly a work of art. The engine mount, air tank, oil
tank, linkage etc. was all powder coated and looks fantastic. The oil
cooler was relocated to the wing, cleaning up the belly of the aircraft and
adding a few knots in cruise. It has a larger 36 gallon fuel tank, smoke
tank with dual exhaust ports, clean kit, oil shutoff with no start micro
switch, new air tank, rebuilt oil pump, new tires, new batteries, rebuilt
gear actuators, Garmin SL40, Becker transponder and original 360 degree
attitude indicator and instruments. I never pulled more than 6 Gs to
extend the life of the airframe.
TTAF 338.4
TSMOH 160
TSPOH 160
Annual due March 2019
The paint is an honest 6/10 but it looks great at 10 and perfect when in
the air. The money was spent on the motor, prop and systems. They run 100%
mechanically and are near bullet proof.
https://www.youtube.com/watch?v=lunZ0gVl3JI
This aircraft has unlimited aerobatic capability combined with the warbird
aesthetic and the Red Star Pilot Association for formation clinics and fly
ins. The community and support for this aircraft are awesome and it is
something you wont get with straight aerobatic aircraft. Post flight
usually takes an hour because of all the attention it gets on the ramp. It
really does have a fantastic combination of appeal from several different
communities.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478271#478271
---
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
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| Subject: | Re: Yak 50 for sale |
Like they say, Cowboy up, or go sit in the truck
> On Feb 26, 2018, at 10:34, Walter Lannon <wlannon@shaw.ca> wrote:
>
>
> a c195 Trainer? You are joking of course.
>
> -----Original Message----- From: GreasySideUp
> Sent: Monday, February 26, 2018 8:09 AM
> To: yak-list@matronics.com
> Subject: Yak-List: Yak 50 for sale
>
>
> My little girl is asking for flying lessons so it is time to trade in the Yak
50 for a Cessna 195. It is offered on Barnstormers with pictures.
>
> 1979 Yak 50 N369AG
>
>
>
> This is the best performing Yak 50 on the planet. It is a 1979 Flush Riveted
model with nearly every performance and trick mod you can add to a Yak. The
spar was reinforced from the factory. The engine was built with lightweight pistons,
gapless rings and auto plugs and puts out a monstrous 420HP behind an
MTV-9, 3 bladed propeller. This plane will hover. The motor and FWF are truly
a work of art. The engine mount, air tank, oil tank, linkage etc. was all powder
coated and looks fantastic. The oil cooler was relocated to the wing, cleaning
up the belly of the aircraft and adding a few knots in cruise. It has
a larger 36 gallon fuel tank, smoke tank with dual exhaust ports, clean kit,
oil shutoff with no start micro switch, new air tank, rebuilt oil pump, new tires,
new batteries, rebuilt gear actuators, Garmin SL40, Becker transponder and
original 360 degree attitude indicator and instruments. I never pulled more
than 6 Gs to extend the life of the airframe.
>
>
>
> TTAF 338.4
>
> TSMOH 160
>
> TSPOH 160
>
> Annual due March 2019
>
>
>
> The paint is an honest 6/10 but it looks great at 10 and perfect when in the
air. The money was spent on the motor, prop and systems. They run 100% mechanically
and are near bullet proof.
>
>
>
> https://www.youtube.com/watch?v=lunZ0gVl3JI
>
>
>
> This aircraft has unlimited aerobatic capability combined with the warbird aesthetic
and the Red Star Pilot Association for formation clinics and fly ins.
The community and support for this aircraft are awesome and it is something you
wont get with straight aerobatic aircraft. Post flight usually takes an hour
because of all the attention it gets on the ramp. It really does have a fantastic
combination of appeal from several different communities.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=478271#478271
>
>
>
>
>
>
>
>
>
> ---
> This email has been checked for viruses by Avast antivirus software.
> https://www.avast.com/antivirus
>
>
>
>
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| Subject: | Re: Engine stumble in flight |
Yep, George's theory sounds plausible. If the primary circuit winding went open
circuit at the right time then the magnetic flux would collapse and one plug
could fire prematurely. That could consume the charge in the intake pipes and
the engine would hesitate until it is refreshed, but wouldn't there also be
a backfire out the carb?
In our case George's theory doesn't fit what was observed. It is the secondary
winding that is intermittently open circuit and there was no backfire. Also,
when the engine restarted, there was a big cloud of smoke as the unburnt fuel
in the cylinders was consumed.
Please don't misunderstand me here, I am not claiming to be right about my theory
either but here is my reasoning...
At the time of our event he was 800' up, 700mm manifold pressure and 70%RPM, dirty
side down in a stable cruise enjoying the scenery.
The pilot reported the engine quit, "Just like someone had turned the mags off."
When he returned to the airfield I had him do an extensive ground run where
of course the engine performed flawlessly.
My first reaction was that it was a fuel issue, but I went through the fuel system
with a fine tooth comb and I found nothing amiss. Sunday here was a 29C (84F)
clear day and no other normal signs so carb ice can be ruled out.
In the Yak-52, if you ignore the cylinders themselves, there are only four components
in common with both magnetos.
1. The ignition harness,
2 & 3. The mag switch in each cockpit,
4. The 'Start Selector' switch in the rear cockpit.
Cross firing in a harness usually causes rough running, not a dead cut so I discounted
that as a possibility. Whatever goes wrong in one magneto somehow effects
what happens in the other one, hence my thoughts about the cross arcing across
a switch.
I have been working on round engines for many years now but I definitely don't
claim to be an expert. I have a good engineers understanding of how they work
and how to fix them, although most of my experience is on P&W engines. I suspect
the solution to finding the cause here is to find the man with a good designers
knowledge of how these Russian lumps tick.
It would be nice to pin this down to a demonstrable, repeatable defect and come
up with a permanent fix....
Haha, Right..... I am off to preflight the pigs!
dsavarese0812(at)bellsout wrote:
> I seriously doubt there is any possibility of that happening. George's explanation
a few days ago is quite accurate regarding what happens when a coil is
failing.
> Dennis
>
>
>
>
>
> From: Looigi
> To: yak-list@matronics.com
> Sent: Sunday, February 25, 2018 11:04 PM
> Subject: Re: Engine stumble in flight
>
>
>
>
>
> Ok, so to add to the story.....
>
>
>
> On Sunday I pulled the two magneto coils out of my machine.
>
>
>
> I did a simple continuity test on the bench with a multimeter across the primary
and then the secondary windings of both coils thinking I could at least compare
the readings. The coil from the right magneto tested open circuit intermittently
on the secondary winding. To be honest I had planned to put them in
the oven at home to cook while the War Office was at work so I wasn't expecting
to find a fault so easily.
>
>
>
> I am going to replace the faulty coil tomorrow and see how he goes from there.
>
>
>
> There are many on here with brains bigger than mine so can I put a theory up
for comment?
>
>
>
> If the coil on my RH mag failed, like it has in the secondary (high tension)
winding, could that send a burst of HT energy down the P lead, and jump the terminals
of one of the 3 switches in that circuit, back down the LH mag P lead
to the primary winding of the LH magneto coil, disrupting the magnetic flux of
the 'good' mag?
>
>
>
> Thoughts??
>
>
>
> Chris
>
>
>
>
>
>
>
>
>
> Read this topic online here:
>
>
>
> http://forums.matronics.com/viewtopic.php?p=478262#478262 (http://forums.matronics.com/viewtopic.php?p=478262#478262)
>
>
>
>
>
>
>
>
>
>
> http://www.m================
>
> http://wiki.matronics.com===================
>
> http://w=====
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478280#478280
Message 9
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| Subject: | Re: Engine stumble in flight |
Looigi, et al;
George, Jan, Mark, Richard and Vic I believe are all on the right track. I
think all believe the capacitor (condenser) is the source of the problem and
after a considerable time "back to the books" I most certainly agree.
Like you all my time spent working on and flying radials has been on P&W
engines almost invariably with Bendix mags. Over 60 years (85 four days
ago) and never heard of such a problem!
I knew the capacitor was there to inhibit arcing of the points but really
had no idea how it worked (electrical is not my long suite). In the Bendix
mags. the primary
capacitor is wired in parallel with the points. Capacitors (so I read) can
be subject to leakage depending on charge level, capacitor type, size, high
temperatures. age, etc.
As Vic or Richard pointed out being buried between the coil windings seems
like the worst possible place to install it. I can't picture how it can be
wired in parallel
in such a location.
The scenario I think goes like this: The cap. is fully charged and for some
reason leaks across the plates. That charge by-passes the points and
energizes the primary/secondary circuit firing spark plugs totally out of
sync. Apparently the cap. can release that full charge in a millisecond
and then go back to normal.
For what it's worth;
Walt
-----Original Message-----
From: Looigi
Sent: Monday, February 26, 2018 12:42 PM
Subject: Yak-List: Re: Engine stumble in flight
Yep, George's theory sounds plausible. If the primary circuit winding went
open circuit at the right time then the magnetic flux would collapse and one
plug could fire prematurely. That could consume the charge in the intake
pipes and the engine would hesitate until it is refreshed, but wouldn't
there also be a backfire out the carb?
In our case George's theory doesn't fit what was observed. It is the
secondary winding that is intermittently open circuit and there was no
backfire. Also, when the engine restarted, there was a big cloud of smoke
as the unburnt fuel in the cylinders was consumed.
Please don't misunderstand me here, I am not claiming to be right about my
theory either but here is my reasoning...
At the time of our event he was 800' up, 700mm manifold pressure and 70%RPM,
dirty side down in a stable cruise enjoying the scenery.
The pilot reported the engine quit, "Just like someone had turned the mags
off." When he returned to the airfield I had him do an extensive ground run
where of course the engine performed flawlessly.
My first reaction was that it was a fuel issue, but I went through the fuel
system with a fine tooth comb and I found nothing amiss. Sunday here was a
29C (84F) clear day and no other normal signs so carb ice can be ruled out.
In the Yak-52, if you ignore the cylinders themselves, there are only four
components in common with both magnetos.
1. The ignition harness,
2 & 3. The mag switch in each cockpit,
4. The 'Start Selector' switch in the rear cockpit.
Cross firing in a harness usually causes rough running, not a dead cut so I
discounted that as a possibility. Whatever goes wrong in one magneto
somehow effects what happens in the other one, hence my thoughts about the
cross arcing across a switch.
I have been working on round engines for many years now but I definitely
don't claim to be an expert. I have a good engineers understanding of how
they work and how to fix them, although most of my experience is on P&W
engines. I suspect the solution to finding the cause here is to find the
man with a good designers knowledge of how these Russian lumps tick.
It would be nice to pin this down to a demonstrable, repeatable defect and
come up with a permanent fix....
Haha, Right..... I am off to preflight the pigs!
dsavarese0812(at)bellsout wrote:
> I seriously doubt there is any possibility of that happening. George's
> explanation a few days ago is quite accurate regarding what happens when a
> coil is failing.
> Dennis
>
>
> From: Looigi
> To: yak-list@matronics.com
> Sent: Sunday, February 25, 2018 11:04 PM
> Subject: Re: Engine stumble in flight
>
>
>
>
> Ok, so to add to the story.....
>
>
> On Sunday I pulled the two magneto coils out of my machine.
>
>
> I did a simple continuity test on the bench with a multimeter across the
> primary and then the secondary windings of both coils thinking I could at
> least compare the readings. The coil from the right magneto tested open
> circuit intermittently on the secondary winding. To be honest I had
> planned to put them in the oven at home to cook while the War Office was
> at work so I wasn't expecting to find a fault so easily.
>
>
> I am going to replace the faulty coil tomorrow and see how he goes from
> there.
>
>
> There are many on here with brains bigger than mine so can I put a theory
> up for comment?
>
>
> If the coil on my RH mag failed, like it has in the secondary (high
> tension) winding, could that send a burst of HT energy down the P lead,
> and jump the terminals of one of the 3 switches in that circuit, back down
> the LH mag P lead to the primary winding of the LH magneto coil,
> disrupting the magnetic flux of the 'good' mag?
>
>
> Thoughts??
>
>
> Chris
>
>
> Read this topic online here:
>
>
> http://forums.matronics.com/viewtopic.php?p=478262#478262
> (http://forums.matronics.com/viewtopic.php?p=478262#478262)
>
>
> http://www.m================
>
> http://wiki.matronics.com===================
>
> http://w=====
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478280#478280
---
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One would suspect that if the fuel in the intake tract is burned it would backfire
thru the carb. That wont happen as the super charger impeller is a still forcing
the fuel/air towards the cylinders preventing the backfire thru the carb.
Frank N23021
Sent from my iPhone
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|
| Subject: | Re: engine stumble |
Hi Frank,
I can tell you from personal experience on P&W engines it is entirely possible
to backfire them out of the carburetor. In fact the old guys who flew DC3's
around southern New Zealand back in the day used to intentionally lean out the
mixture so the resulting backfire would clear the ice from the intake screen.
The supercharger produces relatively low pressure compared to a bunch of fast burning
fuel!
But good call dude, I had not considered the condenser. If that were to fail with
a short circuit the mag would cease to fire the plugs on that mag, but I am
not sure how to explain the other mag going out in sympathy??
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=478292#478292
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| Subject: | Re: Engine stumble in flight |
Hello Walt,
The capacitor does more than avoiding sparks on the points.
It also must help the primary circuit to swing up the energy:
Dielectric energy in the capacitor is transfered into magnetic energy in
the coil and vice versa.
Comparable to what happens into an oscillator circuit.
So indeed, the good working of the capacitor is a must for a flawless coil
functioning.
Nobody knows why the Russians implemented an internal capacitor but they
must have had their reasons for that.
This internal capacitor is not much more than two tiny sheets of metal
wrapped up with insulation material in between.
The frustrating thing about this problem is that well never know exactly
what happens until someone knowledgeable finds the time/money to have a
thorough look at it in a lab.
Thanks for your input,
Jan
On 27/02/2018, 07:07, "Walter Lannon" <owner-yak-list-server@matronics.com
on behalf of wlannon@shaw.ca> wrote:
>
>Looigi, et al;
>
>George, Jan, Mark, Richard and Vic I believe are all on the right track.
>I
>think all believe the capacitor (condenser) is the source of the problem
>and
>after a considerable time "back to the books" I most certainly agree.
>
>Like you all my time spent working on and flying radials has been on P&W
>engines almost invariably with Bendix mags. Over 60 years (85 four days
>ago) and never heard of such a problem!
>
>I knew the capacitor was there to inhibit arcing of the points but really
>had no idea how it worked (electrical is not my long suite). In the
>Bendix
>mags. the primary
>capacitor is wired in parallel with the points. Capacitors (so I read)
>can
>be subject to leakage depending on charge level, capacitor type, size,
>high
>temperatures. age, etc.
>
>As Vic or Richard pointed out being buried between the coil windings
>seems
>like the worst possible place to install it. I can't picture how it can
>be
>wired in parallel
>in such a location.
>
>The scenario I think goes like this: The cap. is fully charged and for
>some
>reason leaks across the plates. That charge by-passes the points and
>energizes the primary/secondary circuit firing spark plugs totally out of
>sync. Apparently the cap. can release that full charge in a millisecond
>and then go back to normal.
>
>For what it's worth;
>Walt
>
>
>-----Original Message-----
>From: Looigi
>Sent: Monday, February 26, 2018 12:42 PM
>To: yak-list@matronics.com
>Subject: Yak-List: Re: Engine stumble in flight
>
>
>Yep, George's theory sounds plausible. If the primary circuit winding
>went
>open circuit at the right time then the magnetic flux would collapse and
>one
>plug could fire prematurely. That could consume the charge in the intake
>pipes and the engine would hesitate until it is refreshed, but wouldn't
>there also be a backfire out the carb?
>
>In our case George's theory doesn't fit what was observed. It is the
>secondary winding that is intermittently open circuit and there was no
>backfire. Also, when the engine restarted, there was a big cloud of
>smoke
>as the unburnt fuel in the cylinders was consumed.
>
>Please don't misunderstand me here, I am not claiming to be right about
>my
>theory either but here is my reasoning...
>
>At the time of our event he was 800' up, 700mm manifold pressure and
>70%RPM,
>dirty side down in a stable cruise enjoying the scenery.
>
>The pilot reported the engine quit, "Just like someone had turned the
>mags
>off." When he returned to the airfield I had him do an extensive ground
>run
>where of course the engine performed flawlessly.
>
>My first reaction was that it was a fuel issue, but I went through the
>fuel
>system with a fine tooth comb and I found nothing amiss. Sunday here was
>a
>29C (84F) clear day and no other normal signs so carb ice can be ruled
>out.
>
>In the Yak-52, if you ignore the cylinders themselves, there are only
>four
>components in common with both magnetos.
>1. The ignition harness,
>2 & 3. The mag switch in each cockpit,
>4. The 'Start Selector' switch in the rear cockpit.
>
>Cross firing in a harness usually causes rough running, not a dead cut so
>I
>discounted that as a possibility. Whatever goes wrong in one magneto
>somehow effects what happens in the other one, hence my thoughts about
>the
>cross arcing across a switch.
>
>I have been working on round engines for many years now but I definitely
>don't claim to be an expert. I have a good engineers understanding of
>how
>they work and how to fix them, although most of my experience is on P&W
>engines. I suspect the solution to finding the cause here is to find the
>man with a good designers knowledge of how these Russian lumps tick.
>
>It would be nice to pin this down to a demonstrable, repeatable defect
>and
>come up with a permanent fix....
>
>Haha, Right..... I am off to preflight the pigs!
>
>
>dsavarese0812(at)bellsout wrote:
>> I seriously doubt there is any possibility of that happening. George's
>> explanation a few days ago is quite accurate regarding what happens
>>when a
>> coil is failing.
>> Dennis
>>
>>
>>
>>
>>
>> From: Looigi
>> To: yak-list@matronics.com
>> Sent: Sunday, February 25, 2018 11:04 PM
>> Subject: Re: Engine stumble in flight
>>
>>
>>
>>
>>
>> Ok, so to add to the story.....
>>
>>
>>
>> On Sunday I pulled the two magneto coils out of my machine.
>>
>>
>>
>> I did a simple continuity test on the bench with a multimeter across
>>the
>> primary and then the secondary windings of both coils thinking I could
>>at
>> least compare the readings. The coil from the right magneto tested
>>open
>> circuit intermittently on the secondary winding. To be honest I had
>> planned to put them in the oven at home to cook while the War Office
>>was
>> at work so I wasn't expecting to find a fault so easily.
>>
>>
>>
>> I am going to replace the faulty coil tomorrow and see how he goes from
>> there.
>>
>>
>>
>> There are many on here with brains bigger than mine so can I put a
>>theory
>> up for comment?
>>
>>
>>
>> If the coil on my RH mag failed, like it has in the secondary (high
>> tension) winding, could that send a burst of HT energy down the P lead,
>> and jump the terminals of one of the 3 switches in that circuit, back
>>down
>> the LH mag P lead to the primary winding of the LH magneto coil,
>> disrupting the magnetic flux of the 'good' mag?
>>
>>
>>
>> Thoughts??
>>
>>
>>
>> Chris
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> Read this topic online here:
>>
>>
>>
>> http://forums.matronics.com/viewtopic.php?p=478262#478262
>> (http://forums.matronics.com/viewtopic.php?p=478262#478262)
>>
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> http://www.m================
>>
>> http://wiki.matronics.com===================
>>
>> http://w=====
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=478280#478280
>
>
>---
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