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mark.bitterlich(at)navy.m
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 Posted: Mon Oct 23, 2017 7:12 am Post subject: [Non-DoD Source] Re: Mags off, still got fire... |
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The question is whether the P leads are not working correctly, or if there was some kind of pre-ignition event.
1. Stay away from the prop when running this test, make sure everyone else stays away from it.
2. Release the clip lock on the back of the P lead plug. Just look at it, hard to describe but you just pull straight back on it and it swings out of the way.
3. HOLD THE BACK OF THE P LEAD CONNECTOR WITH ONE HAND! The part BEHIND the knurled knob part. While holding this, use your OTHER hand to grasp the knurled knob and screw it off. Then the P lead wire will pull straight out of the MAG.
4. With the MAG SWITCH OFF, use a meter and check the resistance of the P lead center contact to ground. It should be zero ohms. Straight short to ground. Now put the P lead back on.
5. Repeat step 3 & 4 with the opposite mag's P lead.
If they both read a short to ground, your mags should be inoperative.
Of course this was also verified when you shut the engine down with the mag switch.
The questions I would ask next would be:
1. What kind of fuel are you using? Car gas per chance?
2. What is the idle RPM on your engine?
3. Is there a chance that the prime pump handle was not vertical and off?
4. Does the engine feel rich at idle? Have you had any plug problems?
Looking for a fuel rich condition, hot CHT, engine not cooled off, idle too high, all of which would tend to cause a prop reversal.
Dennis can take it from here, or someone else.
Mark
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mark.bitterlich(at)navy.m
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| Posted: Mon Oct 23, 2017 7:17 am Post subject: [Non-DoD Source] Re: Mags off, still got fire... |
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I doubt it was a spark, although it could have a hot piece of carbon, etc.
Mark
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jbsoar(at)gmail.com
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| Posted: Mon Oct 23, 2017 7:25 am Post subject: [Non-DoD Source] Re: Mags off, still got fire... |
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Mark-You are right! This was a "compression fire" event. Hot carbon? Maybe. That causes engine "run on" in an old car.
Loaded with fuel, these engines can sometimes fire with the mags grounded.
John B
On Mon, Oct 23, 2017 at 10:14 AM, Bitterlich, Mark G CIV NAVAIR, WD <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:
[quote]--> Yak-List message posted by: "Bitterlich, Mark G CIV NAVAIR, WD" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
I doubt it was a spark, although it could have a hot piece of carbon, etc.
Mark
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bmsim
Joined: 02 Jun 2009
Posts: 32
Location: Alabama
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| Posted: Tue Oct 24, 2017 10:24 am Post subject: Re: [Non-DoD Source] Re: Mags off, still got fire... |
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I'd have to agree on this being a compression fire event, especially from all the off-board reading and conversing I've been doing. I'm definitely going to check the mags, but the engine was hot, and shutting off the mags killed it, so likely it just fired under compression. At least I know what NOT do to now.
Engine temp, not certain, but "in the green," so hot.
I'd have to check the idle RPM.
Running on Avgas.
She doesn't tend to run rich or foul out.
Thanks for the replies!!
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mark.bitterlich(at)navy.m
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| Posted: Tue Oct 24, 2017 12:43 pm Post subject: [Non-DoD Source] Re: Mags off, still got fire... |
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Replies to your questions embedded. These represent my personal opinions based on operating these engines for about 900 hours. Of course I could be wrong, but it has worked for me.
| Quote: | My question for the group, and pardon it being an uneducated one, is this - other birds like my Cessna kill the engine by shutting off fuel and letting it die, then switching off the mags. In the Yak, we shut off the mags to kill the engine, leaving fuel in it. This isn't an issue, unless like me you have to push it back into the hanger with the towbar. In cases where the prop stops at vertical, it needs to be shifted out of the way to fit the towbar, but you can't until it cools. My question is, should I kill it with the fire valve to eliminate this issue, or keep killing it with the mag switch?
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I would say that would be a very bad idea.
| Quote: | Since I'm asking, what is the reason the engine is killed with the mags and not the fuel shut off in the first place?
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First understand that at idle RPM it can run a pretty good long time before it quits by using the EMERGENCY FUEL SHUTOFF valve. Realize that if you were to adopt this method, you have now become a test pilot. You are ignoring published engine operating procedures written by the manufacturer. As such, the blunt truth is that if something were to go wrong using this procedure, it would be on you. That minor fact aside, when you run the engine out of fuel first you are now exposing parts that are normally immersed in fuel, to air. How many diaphragms in the carb are impacted by this? I honestly have no idea. Will the emergency fuel shut-off develop a leak after continual use, since it was never really designed for that purpose, and then leak fuel in the engine compartment that you might not even notice? It's possible. That said, it is your aircraft. But expect a few minutes of run time at idle before it stops running. Lastly this is a radial engine built in Russia. You really can't compare it to an opposed engine built here and ask why there are different procedures. Answer? They are totally different engine designs.
| Quote: | One other question now that I think about it. Her prior owner told me that even when landing to take on fuel, if she sat longer than about 10 minutes he would go ahead and pull her through 12 blades just as a precaution. Wouldn't that be inadvisable (unless engine temps had come down enough during the sitting phase).
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Damned if you do, damned if you don't. If you fail to pull it through, you have a strong potential for a hydraulic lock. Now you're talking really serious engine damage. ALWAYS PULL THE ENGINE THROUGH.
| Quote: | So I guess either fuel fast with the cowl flaps closed to hold in heat, or open the flaps to let the engine cool, and take your time fueling because it'll be a bit before you could pull her through????
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Why would you want to try to hold in heat after shutting the engine down? The idea is to cool it off completely before shutting it down, and that means louvers open .... way long before you even land. Slowly of course, but cooled off.
The real question to be asking is why your engine is doing what it is doing, on a regular basis, and other M-14's are NOT. The very first thing you should do is to have an A&P mechanic that is FAMILIER with this engine family, check the timing on both mags!
The next thing I would advise (open for discussion by those reading) is to pour a FULL QUART of Marvel Mystery Oil INTO THE FUEL and run that engine just as hard as you possibly can. WIDE FREAKING OPEN as long as you do not exceed oil temps, or CHT temps. Have the prop running 100%, or if this scares you, 99%. Push the throttle to the firewall and after take-off and once you are in level flight, pull the throttle back just enough until you see the manifold pressure start to move down. JUST AS YOU SEE IT MOVE, and then leave it there. Run it like that until you are out of fuel. Or close to it of course. Cool it down slowly in flight. Land, fill it up put in another quart of MMO and do it again.
Two things. You must make sure your timing is correct before doing this. The reason for MMO and full power is to try and get any LEAD out of the cylinders. I am ASSUMING you have done a compression check recently and have listened for any leaks coming out the exhaust pipes of any cylinders?
My input is to do the above and then see if the problem is not cured. Running these engines too cool and at "let's take it easy on the old girl" RPM is a BIG MISTAKE. Run the piss out of it, with MMO, and hope to blazes that you blow the carbon out, because unless your timing is all whacked up, that is the most likely cause of your whole problem.
Mark
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bmsim
Joined: 02 Jun 2009
Posts: 32
Location: Alabama
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| Posted: Wed Oct 25, 2017 4:26 am Post subject: Re: [Non-DoD Source] Re: Mags off, still got fire... |
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Thank you for all of the great advice, Mark. I appreciate you taking the time to type it out, and I will definitely act on it.
In regards to the "why would you hold in heat" question, my apologies, I was referring to a refuel stop on a XC flight, where you were just stopping for gas, etc.
Thanks again!
Brandon
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