Engine cut out on negative G.. and smoke issue

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Medtner
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Re: Engine cut out on negative G.. and smoke issue

Post by Medtner »

Scott - A2A wrote:Please check fuel pressure when this happens.

Scott.
The fuel pressure was normal when this happened to me. I tried wobbling some fuel too - indeed all kinds of combinations from flooded full throttle/no mixture starts - to a touch of primer and a mixture rich start.
When this first happened I kept on trying for quite a while - the engine warmed up from around 5 degrees to 40 in the time I was cranking and toiling. :-P
Erik Haugan Aasland,

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All the Accusim-planes are in my hangar, but they aren't sitting long enough for their engines to cool much before next flight!

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Re: Engine cut out on negative G.. and smoke issue

Post by MatzeH84 »

In my case fuel pressure was perfect. I also tried to wobble pump, however it didn't help. I will get back to my PC in a moment, and I will try to recreate the issue.
Kind regards, Matthias

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Re: Engine cut out on negative G.. and smoke issue

Post by MarcE »

Scott - A2A wrote:It would be helpful if we could determine if this strange engine dying issue ALWAYS happens after a negative G. If we know this 100%, I can hyper focus on this part of the system.

Scott.

I've tried it 3 times now. Every time the Gs go negative, the engine dies immediately. The prop keeps turning of course and using the primer it is possible to get some ignitions but what ever you do with the mixture lever, the manual fuel pump, pumping with the throttle or pulling 3-4gs.. you will not get the engine run again.

Autostart lets the engine run until the primed fuel is burned and so you can start the engine manually. A simple aircraft reload will fix it.

Greets,
Marc

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Re: Engine cut out on negative G.. and smoke issue

Post by Lewis - A2A »

Hey Marc,

to help re-produce please can you let us know how much neg G you are giving, what are you doing exactly to get the results?

thanks
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Re: Engine cut out on negative G.. and smoke issue

Post by Scott - A2A »

Yes Marc, if you are able to reproduce this on demand, you are a rare bird here, so don't try to fix this issue. You're being able to reproduce this allows us to send you a test to see if this issue gets fixed. And to support what Lewis is saying, can you explain EXACTLY what you are doing to reproduce this effect? Please include power settings and everything you can think of.

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joers182
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Re: Engine cut out on negative G.. and smoke issue

Post by joers182 »

These issues sound very similar to the issues I'm having. Once the engine is shutdown you are unable to restart it without restarting the sim.

I don't know weather its related to the negative G (I didn't pull any negative G's) but maybe its the same issue, the engine dies and you are unable to restart it. I can fully reproduce it every time on the ground without even moving.
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Re: Engine cut out on negative G.. and smoke issue

Post by MatzeH84 »

Ok I just did a test: level flight, cruise power setting, push -1G momentarily, engine cuts out and never comes back.
Kind regards, Matthias

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Re: Engine cut out on negative G.. and smoke issue

Post by MarcE »

Scott,

sry for the delay, I was on a short visit at my parents..

I got the P3D version on P3Dv3.2.

It's weird, reminds me on the clickspot thing. sometimes it happens, sometimes not. I found it hard to reproduce it on purpose after I let the aircraft parked after a reload for about 2 hours. But before I wrote 3 hours ago I was on level autopiloted flight with 25-26MP, 1800RPM on 8000ft and leaned mixture with the lever half back. Then I had the idea to do some clean stalls, go into a spin and during that spin the engine cut. I did an emergency landing as I couldn't make it start in flight. Then I put the airplane back to friday harbour using the airport selection and couldn't start it eather. it just did as described above, it burned the primer fuel. With an aircraft reload it worked as it should. Gs were not that much negative, just the stick fully forward at maybe 130-140mph. -1/-2g approx.

Now I tried to kill the engine again in flight and it caughed, but caught itself as soon as the Gs were stable positive. Both leaned and rich. same power setting. then I cut off the mixture and brought it back to rich and it did NOT restart. Now I'm paused in flight with turning prop, mags on, mixture rich, carb mixt (!) and carb heat half way back. I am not sure if the carb heat was on 3h before, but I know that the carburator was not iced.

I will do another emerg landing and try to start the engine on the ground.

edit:
does not start on the ground.

looks like once you cut the fuel in flight you cant bring it back (maybe depending on MP and RPM? I don't know your coding :D)

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Re: Engine cut out on negative G.. and smoke issue

Post by Scott - A2A »

Great feedback, testing now.
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Re: Engine cut out on negative G.. and smoke issue

Post by Krycekuk »

I've just had this happen on the ground after landing with low fuel. I wanted to top off the tanks and take off again. However I could only get the engine running with constant priming. Tried all combinations of using the manual fuel pump, different mixture positions, throttle, different fuel tanks (plenty of fuel in both). Even with auto start the engine would quit if I didn't constantly prime.

I landed pretty gracefully with both fuel warning lights on but with fuel remaining in the tanks (confirmed with the shift 4 view), taxied in ok and shutdown the engine as normal, no serious negative g's involved.
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Re: Engine cut out on negative G.. and smoke issue

Post by MarcE »

Scott,

I have just started a complete new flight (restart of P3D, load up the default king air and switch to the T6, standard clear weather at MSL.

Engines running by default.

I took off with carb heat off, raised the gear and reduced the power to 25/2000, mixture leaned a quarter back. I climbed to 2000 feet, fuel lever on right tank which is a little fuller than the left tank. Then I pushed to -0,5 g. The engine caughed and ran at 25''MP and 1200RPM. NO lever touched, neither throttle, nor prop nor mixture. It runs absolutely smoothe, no rattling or shaking. no fire, no smoke, no explosion, just nothing but doesn't increase RPM anymore.

(flying...)


The fuel lever doesn't even cut the fuel now, it is without function... the throttle changes the MP, it's visible on the gauge, Prop lever and mixture have no effect.

Fuel pressure and temps are normal.

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Re: Engine cut out on negative G.. and smoke issue

Post by lonewulf47 »

Marc, if you seem to be able to reproduce the issue more or less "on demand", can you do me a favour and check something for me? I have seen this issue on a few occasions and I seem to be able to tie it to another phenomenon that showed up.

The thing I do ATM (only for testing purposes of course) is prior te each take-off I look at the SHIFT-2 page. You have certainly seen the numbers for FUEL ECO which is nothing else than the actual Fuel Flow. I then set some power (at last out of idle) and pull slowly back the Mixture Lever. I have found cases where the engine seems to run normally, but the Fuel Flow did not react on the Mixture Lever input i.e. it remained constant until a moment @~70% where it cut immediately. Pushing the Lever back the engine recovers immediately. Actually the Fuel Flow should decrease upon pulling the Mixture Lever.

Now each time I go flying with this strange Mixture issue I can be sure that the engine quits after applying a negative g-load and does not restart, but showing exactly the behaviour that you describe. The Fuel Pressure was indicating normally thereafter, but to be honest, I did not look at it when going through negative g.

So my presumption is the following: whenever this strange Mixture issue is showing up (I can't reproduce it in a reliable pattern), the engine quits when applying negative g. It possibly quits because a short interruption in fuel supply (will have to lookt after the Fuel Pressure next time it happens), but only if this interruption is caused by dropping Fuel Pressure. It's one more theory for this mysterious case. On my end I can at least say that WHENEVER THIS MIXTURE ISSUE IS PRESENT, THE ENGINE QUITS AT NEGATIVE G LOAD AND CANNOT BE RESTARTED.
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Medtner
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Re: Engine cut out on negative G.. and smoke issue

Post by Medtner »

lonewulf47 wrote:Marc, if you seem to be able to reproduce the issue more or less "on demand", can you do me a favour and check something for me? I have seen this issue on a few occasions and I seem to be able to tie it to another phenomenon that showed up.

The thing I do ATM (only for testing purposes of course) is prior te each take-off I look at the SHIFT-2 page. You have certainly seen the numbers for FUEL ECO which is nothing else than the actual Fuel Flow. I then set some power (at last out of idle) and pull slowly back the Mixture Lever. I have found cases where the engine seems to run normally, but the Fuel Flow did not react on the Mixture Lever input i.e. it remained constant until a moment @~70% where it cut immediately. Pushing the Lever back the engine recovers immediately. Actually the Fuel Flow should decrease upon pulling the Mixture Lever.

Now each time I go flying with this strange Mixture issue I can be sure that the engine quits after applying a negative g-load and does not restart, but showing exactly the behaviour that you describe. The Fuel Pressure was indicating normally thereafter, but to be honest, I did not look at it when going through negative g.

So my presumption is the following: whenever this strange Mixture issue is showing up (I can't reproduce it in a reliable pattern), the engine quits when applying negative g. It possibly quits because a short interruption in fuel supply (will have to lookt after the Fuel Pressure next time it happens), but only if this interruption is caused by dropping Fuel Pressure. It's one more theory for this mysterious case. On my end I can at least say that WHENEVER THIS MIXTURE ISSUE IS PRESENT, THE ENGINE QUITS AT NEGATIVE G LOAD AND CANNOT BE RESTARTED.
Yeah, you've seen the same as I have. Only difference is that I haven't done any negative Gs...
The good thing is that we're on to something! Let's hope we can root out this goblin. :P
Erik Haugan Aasland,

Arendal, Norway
(Homebase: Kristiansand Lufthavn, Kjevik (ENCN)

All the Accusim-planes are in my hangar, but they aren't sitting long enough for their engines to cool much before next flight!

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Re: Engine cut out on negative G.. and smoke issue

Post by MarcE »

Oskar,

being parked I applied some power to maintain 1000rpm and had a fuel flow of 7 gph according to the shift 2 menu. I then pulled the mixture back slowly and the FF decreased just normal to the point where it cut. I immediatley increased mixture slowly back to full rich and the engine ran smooth at 1000rpm. the fuel flow went back to 7gph.

I then cut the power very quickly, the engine cut and is also able to restart itself, but the fuelflow doesn't decrease anymore when i lean slowly but cuts at a point. When I apply throttle, FF increases too. Running at 1500rpm and reducing mixture doesn't affect FF either but cuts it at a point.

Fuel pressure is ALWAYS jumping around 4 without any exception.


again in german:

wenn ich anfangs das gemisch langsam zurückziehe, reduziert sich auch der fuel flow entsprechend und nimmt auch bei langsam zunehmendem mixture selbst wieder langsam zu. wie es eben sein sollte. wenn ich aber ruckartig auf cut off ziehe, hängt sich der fuel flow irgendwie bei 7 gph auf und lässt sich nicht mehr reduzieren, bis er eben ganz ausgeht. höhere throttle-einstellungen bringen einen höheren verbrauch, leanen reduziert diesen aber nicht mehr. wie gesagt, der treibstoffdruck verharrt stur auf diesen 4 lbs pro inch². der ändert sich auch beim negativ-drücken nicht die bohne. ich vermute, da ist irgendwo beim leanen der wurm drin.
Last edited by MarcE on 28 Mar 2016, 10:09, edited 1 time in total.

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lonewulf47
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Re: Engine cut out on negative G.. and smoke issue

Post by lonewulf47 »

MarcE wrote:Oskar,

being parked I applied some power to maintain 1000rpm and had a fuel flow of 7 gph according to the shift 2 menu. I then pulled the mixture back slowly and the FF decreased just normal to the point where it cut. I immediatley increased mixture slowly back to full rich and the engine ran smooth at 1000rpm. the fuel flow went back to 7gph.

I then cut the power very quickly, the engine cut and is also able to restart itself, but the fuelflow doesn't decrease anymore when i lean slowly but cuts at a point. When I apply throttle, FF increases too. Running at 1500rpm and reducing mixture doesn't affect FF either but cuts it at a point.

Fuel pressure is ALWAYS jumping around 4 without any exception.
Now, if you go flying with the Mixture issue according to my theory it should quit at negative g-load and NOT be restartable and my presumption is that this is caused by a short drop of Fuel Pressure.
Last edited by lonewulf47 on 28 Mar 2016, 10:11, edited 1 time in total.
Oskar

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