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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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 Posted: Fri May 29, 2015 10:58 am Post subject: Engine roughness, as in stops. starts. stops. starts. |
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Mark,
Been there, got the T shirt x 3. Two for coils and one because the RU supplier filled the mag bossing off and sold the mag as a 9F.
Doc
Sent from my iPad
[quote] On May 29, 2015, at 9:58 AM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil> wrote:
Might as well add my 2 cents. First of all, I totally concur with Richard Goode, not only because he has been around these aircraft longer than most anyone else on this list, but also because I have experienced the exact same symptoms troubleshooting a YAK-52 just a few months ago.
Very likely NOT the carb. And this is not meant as sarcasm, but after some "mechs" mess around with it for a while it might very well end up being that as well. Very few people know how to adjust these pressure carbs properly and there is much more to it than turning the "screw" on the outside. Of course there is nothing like "doing" to help in learning, as long as it is on your aircraft and not mine please. What I am saying here is that messing around with the carb should be LAST on anyone's list and never first. Also it is the nature of pressure carbs that if you adjust one thing, it impacts another. Just had a Bendix PS-7BD rebuilt and flowed ($3000 by the way) and while not Russian, the theory is the same and worth reading about.
There is a very simple test to run here. Go up and fly it one more time and just simply fly it until it starts doing this again, and then switch off one mag and then the other to see if it then STOPS doing it or gets much worse on one. It is very unusual for both mags to have something go bad with them at the same time (thankfully). STRONGLY recommend this before applying fingers or tools to the carb.
The problem with the coils is legendary. If you own one of these aircraft it is not a matter of "if" you will have a coil go bad, but when. Other things can cause the coil to over-heat faster and these range from wide gaps on spark plugs, to misadjusted points "or dwell" as mentioned. Also, I have seen the point assembly actually crack leading to erratic ignition (you mentioned that one yourself). Points will not usually come out of adjustment through normal use enough to cause what you are experiencing, but if they are cracked and flexing they can cause these exact symptoms too.
I have had two personal experiences with mag issues on my own aircraft. In one case, the internal gearing in the mag (M9F) let go, and the engine just STOPPED. Ernie (in another message) mentioned that this should not happen should it? Well, that is what we are all taught, but as it turns out it is not necessarily accurate. I did not time how many seconds it just STOPPED, but it was enough time for me to think: "Oh crap, I am going to have to land this thing on the freaking OUTER BANKS! Should I go in gear up or down?". And then it came back running rougher than blazes. I tried the mag switch, and it ran on one mag perfectly and on the other it just stopped. So why did that happen? It should not have. But it did. Lots of "might be maybe" theory, but honestly I do not know.
Second time was a mag coil. Pretty much exactly what you are talking about here. Again, simply switching between mags in flight isolated the problem very quickly. Why did it impact engine performance on both? Well, all I can think of is a spark plug firing way in advance. In my mind, only three things can happen with ignition. It doesn't work at all, it fires early, or it fires late. Not working at all would not make the engine cough and gag, UNLESS you had a problem with the OTHER ignition set that you didn't know about (bad plug, etc.) If it fired late, it would not matter at all. But if it fired early... way early, as the piston was coming up on the compression stroke ..... some weird stuff would happen, bad detonation and engine coughing and puking being one. So that is my "theory".
If this test is performed in flight and it does it again on EITHER MAG, then the next step is a compression test. But really, you need to fly it one more time.
Mark
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Viperdoc |
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sun May 31, 2015 10:22 am Post subject: Engine roughness, as in stops. starts. stops. starts. |
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No. Ask Termikus about it.
Sent from my iPad
| Quote: | On May 31, 2015, at 12:05 PM, Jan Mevis <jan.mevis(at)informavia.be> wrote:
Massive discharge with the heat induced break down of the capacitor?
I don't understand this, can you explain please?
Jan
> On 31/05/15 18:48, "Roger Kemp" <f16viperdoc(at)me.com> wrote:
>
>
>
> As explained by the Lithuanian engineers the massive discharge with the
> heat induced break down of the capacitor in the coil results in arcing in
> the distributor cap so that discharge flows / jumps to the next cylinder
> in line on the intake stroke. With the intake valve open when that
> aberrant discharge arrives the spark will consume the supercharger
> contents. The backfire is most likely through the carb when the charge is
> consumed.
> The pilots of the aircraft in formation with me said they saw a sudden
> belch of black smoke from under the chin of my bird. I felt the
> hesitation as well as saw the momentary hesitation of the prop slowing.
> Then the engine picked back up like nothing occurred. Have had that
> happen twice since owning my 52. Did an airborne mag check the second
> time with the engine quitting on selection of the #1 mag. In both cases
> changing the mag coils resolved the problem.
> Litaurus and Termikus are the bearers of that tidbit of info. Made sense
> to me then and now.
> Doc
>
> Sent from my iPad
>
>> On May 31, 2015, at 3:38 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:
>>
>>
>>
>> I'm with Egon, getting an engine anywhere near 200°C on the ground is
>> very hard on them, let alone 250°C. Without the proper cooling airflow
>> wrapping around the cylinders they are getting unevenly hot, with
>> hotspots that may exceed the temperature of where the thermocouple is
>> placed.
>>
>> I've got to ask - what are we talking about lighting the whole
>> supercharger 'charge' on fire?
>>
>> Do they mean the spark is so advanced it lights off way early and the
>> flame front travels backwards through the induction system? Is this even
>> physically at anything above starting RPM?
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=442829#442829
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Viperdoc |
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sun May 31, 2015 10:28 am Post subject: Engine roughness, as in stops. starts. stops. starts. |
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Massive maybe overstatement but the whomp from the engine with the prop hesitation was impressive.
Doc
Sent from my iPad
| Quote: | On May 31, 2015, at 12:05 PM, Jan Mevis <jan.mevis(at)informavia.be> wrote:
Massive discharge with the heat induced break down of the capacitor?
I don't understand this, can you explain please?
Jan
> On 31/05/15 18:48, "Roger Kemp" <f16viperdoc(at)me.com> wrote:
>
>
>
> As explained by the Lithuanian engineers the massive discharge with the
> heat induced break down of the capacitor in the coil results in arcing in
> the distributor cap so that discharge flows / jumps to the next cylinder
> in line on the intake stroke. With the intake valve open when that
> aberrant discharge arrives the spark will consume the supercharger
> contents. The backfire is most likely through the carb when the charge is
> consumed.
> The pilots of the aircraft in formation with me said they saw a sudden
> belch of black smoke from under the chin of my bird. I felt the
> hesitation as well as saw the momentary hesitation of the prop slowing.
> Then the engine picked back up like nothing occurred. Have had that
> happen twice since owning my 52. Did an airborne mag check the second
> time with the engine quitting on selection of the #1 mag. In both cases
> changing the mag coils resolved the problem.
> Litaurus and Termikus are the bearers of that tidbit of info. Made sense
> to me then and now.
> Doc
>
> Sent from my iPad
>
>> On May 31, 2015, at 3:38 AM, JL2A <info(at)flyingwarbirds.com.au> wrote:
>>
>>
>>
>> I'm with Egon, getting an engine anywhere near 200°C on the ground is
>> very hard on them, let alone 250°C. Without the proper cooling airflow
>> wrapping around the cylinders they are getting unevenly hot, with
>> hotspots that may exceed the temperature of where the thermocouple is
>> placed.
>>
>> I've got to ask - what are we talking about lighting the whole
>> supercharger 'charge' on fire?
>>
>> Do they mean the spark is so advanced it lights off way early and the
>> flame front travels backwards through the induction system? Is this even
>> physically at anything above starting RPM?
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=442829#442829
|
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Viperdoc |
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Viperdoc
Joined: 19 Apr 2014
Posts: 484
Location: 08A
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| Posted: Sun May 31, 2015 4:48 pm Post subject: Engine roughness, as in stops. starts. stops. starts. |
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Yes, along with Stem Cells and PRP intradiscal above and below the fusion to slow degeneration in the discs above and below from all that low frequency vibration transmitted to your tired Ol Army Aviator But from that thing you rotor heads call a Jesus Nut! Maybe could have helped that sheared off tail boom by that tail grabber that caused that abrupt auto rotation along with CFT resulting burst fracture in your back in the day. Unfortunately it happened to you before we started getting smart on the use of autologous mesenchymal Stem Cells and Platelet Rich Plasma mixed with donor bone powder to accelerate fracture healing. We've come a long way baby but we are not there yet!
But alas my ex rotor head bud are forever condemned to tincture of Jeremiah Weed and lap dancers at that Ol Piano bar on the coast! 😜
Yes and no this does not have mush to do with Yakovating And Zghang flings unless you have a bad day.
Ck 6
Doc
Sent from my iPad
On May 31, 2015, at 7:01 PM, Jon Blake <jblake207(at)comcast.net (jblake207(at)comcast.net)> wrote:
[quote]Doc, does that spinal infusion come with a little umbrella and slice of lime?  JB
Sent from my Verizon Wireless 4G LTE DROID
Roger Kemp <f16viperdoc(at)me.com (f16viperdoc(at)me.com)> wrote:
--> Yak-List message posted by: Roger Kemp <f16viperdoc(at)me.com (f16viperdoc(at)me.com)>
Jan,
I personally do not know what is breaking down in the coil between the primary and secondary windings that causes the aberrant high voltage discharge. I do not know how the Russians build their secondary winding pies or how they insulate them. Is it an internal resistor that fails, is it the waxed cardboard insulation or the break down of the rubberized insulation that results in the current leakage. Is it internal heat build up and air bubble expansion that allows internal arching I do not know. I just know I was told there is a breakdown and that results in an aberrant spark that causes an impressive internal backfire with momentary engine pause that causes an eye opening experience.
I personally accepted what Litaurus and Termikus said because it made sense it its simplified term. It is kind of like me telling a cancer patient suffering from intractable pain that I can put a catheter in their subarachnoid space in their spinal canal that infuses micro-milliliters of narcotic and local anesthetic into the cerebrospinal fluid with the tip of the catheter over the dermatonal segment that corresponds to their afferent pain input into level three and seven of the Rexed Lamina in the posterior horn of the cord. Using that combination we will be blocking nocioceptive and neuropathic pain.
All they care about is their pain going to be better controlled and they are not going to be gorked on drugs in their last months or days. Litaurus's explanation fits the simplified answer. All I wanted was does changing the coil out stop the problem. It did in my case. I now have two spare coils sitting in my spares cabinet.
Doc
Sent from my iPad
| Quote: | On May 31, 2015, at 11:48 AM, Roger Kemp <f16viperdoc(at)me.com (f16viperdoc(at)me.com)> wrote:
--> Yak-List message posted by: Roger Kemp <f16viperdoc(at)me.com (f16viperdoc(at)me.com)>
As explained by the Lithuanian engineers the massive discharge with the heat induced break down of the capacitor in the coil results in arcing in the distributor cap so that discharge flows / jumps to the next cylinder in line on the intake stroke. With the intake valve open when that aberrant discharge arrives the spark will consume the supercharger contents. The backfire is most likely through the carb when the charge is consumed.
The pilots of the aircraft in formation with me said they saw a sudden belch of black smoke from under the chin of my bird. I felt the hesitation as well as saw the momentary hesitation of the prop slowing. Then the engine picked back up like nothing occurred. Have had that happen twice since owning my 52. Did an airborne mag check the second time with the engine quitting on selection of the #1 mag. In both cases changing the mag coils resolved the problem.
Litaurus and Termikus are the bearers of that tidbit of info. Made sense to me then and now.
Doc
Sent from my iPad
> On May 31, 2015, at 3:38 AM, JL2A <info(at)flyingwarbirds.com.au (info(at)flyingwarbirds.com.au)> wrote:
>
> --> Yak-List message posted by: "JL2A" <info(at)flyingwarbirds.com.au (info(at)flyingwarbirds.com.au)>
>
> I'm with Egon, getting an engine anywhere near 200°C on the ground is very hard on them, let alone 250°C. Without the proper cooling airflow wrapping around the cylinders they are getting unevenly hot, with hotspots that may exceed the temperature of where the thermocouple is placed.
>
> I've got to ask - what are we talking about lighting the whole supercharger 'charge' on fire?
>
> Do they mean the spark is so advanced it lights off way early and the flame front travels backwards through the induction system? Is this even physically at anything above starting RPM?
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=442829#442829
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Viperdoc
Joined: 19 Apr 2014
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| Posted: Mon Jun 01, 2015 5:59 pm Post subject: Engine roughness, as in stops. starts. stops. starts. |
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Thanks Mark.
Doc
Sent from my iPad
[quote] On Jun 1, 2015, at 3:48 PM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil> wrote:
The problem being discussed was focused on a primary to secondary short. Not the primary failing open.
That said, yes... you are correct. If the points were closed, and the flux field was at maximum, and then suddenly the primary opened, there would indeed be a single spark discharge.
At that point, the coil primary would remain open, and that mag would then be totally dead. High Voltage coil windings do not open and then fix themselves and start working again.
The rest of the thread explained what component does exhibit those tendencies and what such a failure would cause.
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