reported shut down differences Endless backfiring on shutdown

[hazzer]

23 hours ago, SUNTSAG said:

This is my preferred approach to following the documented procedure….a picture paints a thousand words. Cheers.

I don't think we are questioning the shutdown procedure. The point being is that when you still get backfires and splutters when you shouldn't which is an incorrect modelling/simplification of the shutdown process, which applies to all the merlin aircraft at minimum.

[Nealius]

I tried the pilots notes technique except I shut off the mags immediately after pulling the cutouts. Right engine sputtered once, left engine didn't.

There's also way too much sputter/pops on startup, in my opinion. Watching footage of restored Mossies, you might hear one or two pops and that's it. In DCS, you'll hear 20+ pops until the engine gets above 400~500rpm or so.

Edited November 29, 2023 by Nealius

[SUNTSAG]

3 hours ago, hazzer said:

I don't think we are questioning the shutdown procedure. The point being is that when you still get backfires and splutters when you shouldn't which is an incorrect modelling/simplification of the shutdown process, which applies to all the merlin aircraft at minimum.

To be fair I realise no one is/was questioning the shutdown procedure but no one was using the correct one. So to be helpful, I provided the correct documented information.

As part of any route cause analysis, the starting point to determine if there is an issue or improvement opportunity; is to use the correct procedure as prescribed in the pilot notes. Any variation to the actual procedure could potentially result in the issues being encountered. Therefore in the first instance, common sense dictates follow the correct procedure.

Also during route cause analysis a single data point is insufficient to determine that a problem exists and statistically 8 data points are preferable and will potentially highlight a trend if charted. I hope this helps as to why I provided this information. I am not saying there isn’t an issue but I can confirm I haven’t experienced it personally. Cheers.

[Art-J]

3 hours ago, SUNTSAG said:

I am not saying there isn’t an issue but I can confirm I haven’t experienced it personally. Cheers.

Mate, with all due respect, I'm puzzled now by that statement and not sure you understand what detail exactly is being discussed here. The mysterious shutdown sputter has been a "thing" in Mustang, Spit and Mossie since their respective releases years ago, so it literally is impossible NOT to experience it.

Unless of all warbirds in DCS, you only ever flew Mossie and only in hot-started missions, which I know can not be the case because of great tutorial missions and videos you created for that plane.

Now, thinking about the Merlin engine itself, one could argue that fuel is being cut off at pressure carb level and thus there's still unspecified some of the mixture left in manifold between carb and intake valves. That still doesn't explain, however, why there's never any loud sputter after hot-stared missions, and there always is one (with 5 or 6 "bangs") after cold-started missions. Doesn't matter what shutdown procedure is followed.

I mentioned it before and showed in replay tracks posted on previous page already, but once again just for you - below is another replay track which follows "to a T" the period-correct shutdown procedure you posted. All by mouse to avoid variables in form of HOTAS buttons/witches assignments. And yet, with the same and repeatable result - fast and quiet shutdown after spawning hot-started, but longer and sputtery shutdown after engines are restarted.

P.S. - I guess there's one more thing we might check later - what would happen if we only used built in auto-start and auto-stop commands? Let's allow DCS code do its job without human interference and see the results.

Cheers!

 

2.9_cutoff_test 4.trk

Edited November 29, 2023 by Art-J
Track with better RPM added.

[grafspee]

4 hours ago, Art-J said:

Now, thinking about the Merlin engine itself, one could argue that fuel is being cut off at pressure carb level and thus there's still unspecified some of the mixture left in manifold between carb and intake valves.

 

This is why always say that, engine should not cut out at moment when you move mixture to cut off, engine should run for some time, and after noticeable delay engine should cut out and if any spontaneous fuel induction happen there is a time engine to splutter when rpm is quite high so that spark from magnetos is strong. In DCS we have instant reaction on cut off lever and perfect engine rpm run down to 100rpm and then magic happen. I wonder why in those planes you have something like boosters coil when engine without priming and coil boosting combust fuel without problem

 

 

Edited November 29, 2023 by grafspee

[Reflected]

This has been happening since release, I'm sure it's a bug. I'm following the procedure in the RL manual, I pull the cutoff handles - mind you, using a keybind.

[hazzer]

On 11/29/2023 at 3:00 PM, SUNTSAG said:

To be fair I realise no one is/was questioning the shutdown procedure but no one was using the correct one. So to be helpful, I provided the correct documented information.

As part of any route cause analysis, the starting point to determine if there is an issue or improvement opportunity; is to use the correct procedure as prescribed in the pilot notes. Any variation to the actual procedure could potentially result in the issues being encountered. Therefore in the first instance, common sense dictates follow the correct procedure.

Also during route cause analysis a single data point is insufficient to determine that a problem exists and statistically 8 data points are preferable and will potentially highlight a trend if charted. I hope this helps as to why I provided this information. I am not saying there isn’t an issue but I can confirm I haven’t experienced it personally. Cheers.

Sorry but as art has said, is 100% unavoidable if shutting down as per SOP in any merlin aircraft in dcs. So you might be missing the issue that we are highlighting.

[Skewgear]

For those saying the engines should splutter and backfire a bit on shutdown, it seems the real aircraft shuts down very quickly indeed with barely a pop:

 

[Skewgear]

On 11/29/2023 at 5:48 PM, Art-J said:

Mate, with all due respect, I'm puzzled now by that statement and not sure you understand what detail exactly is being discussed here. The mysterious shutdown sputter has been a "thing" in Mustang, Spit and Mossie since their respective releases years ago, so it literally is impossible NOT to experience it.

Unless of all warbirds in DCS, you only ever flew Mossie and only in hot-started missions, which I know can not be the case because of great tutorial missions and videos you created for that plane.

Now, thinking about the Merlin engine itself, one could argue that fuel is being cut off at pressure carb level and thus there's still unspecified some of the mixture left in manifold between carb and intake valves. That still doesn't explain, however, why there's never any loud sputter after hot-stared missions, and there always is one (with 5 or 6 "bangs") after cold-started missions. Doesn't matter what shutdown procedure is followed.

I mentioned it before and showed in replay tracks posted on previous page already, but once again just for you - below is another replay track which follows "to a T" the period-correct shutdown procedure you posted. All by mouse to avoid variables in form of HOTAS buttons/witches assignments. And yet, with the same and repeatable result - fast and quiet shutdown after spawning hot-started, but longer and sputtery shutdown after engines are restarted.

P.S. - I guess there's one more thing we might check later - what would happen if we only used built in auto-start and auto-stop commands? Let's allow DCS code do its job without human interference and see the results.

Cheers!

 

2.9_cutoff_test 4.trk 240.24 kB · 1 download

 

Thanks for this. Can't promise anything but your track does clearly show a difference between shutting down from hot start spawn and shutting down after a player engine start.

[Slippa]

This is another thread with some good info in it. Constructive and for someone not mechanically minded like me, sort of educational.

There was another great thread discussing the Jug and its cockpit layouts and whatnot. Like here, I was reading it appreciating the research and enjoying not feeling like the only person bothered about the prop birds. Instead of getting a thanks for the info and we’ll look into it the thread was locked, discussion over. Maybe I missed something I dunno? I’m reading wondering where this one will go too now. 

The only thing for it is to line up a newly released Typhoon, Wildcat, Lancaster, Ju88, He111, Me110 and a Horsa glider with paratroops and compare Mossie cold starts and shutdowns. 

 

[Nealius]

7 hours ago, Skewgear said:

it seems the real aircraft shuts down very quickly indeed with barely a pop

The startup as well. Not a single pop (that I could hear) on startup compared to the DCS racing pistol continuously popping until rpm gets above 400~500 or so.

[grafspee]

9 hours ago, Skewgear said:

For those saying the engines should splutter and backfire a bit on shutdown, it seems the real aircraft shuts down very quickly indeed with barely a pop:

 

This is exactly my point, if any splutter or backfiring happen it will happen while engine still has high rpm. Like on this recording, not at moment when engine is about to stop rotating.

[Nealius]

So according to the pilot's notes:

800rpm, pull cutouts, wait for prop to stop spinning, shut off magnetos. So I did. Right engine took 33 seconds to stop spinning after pulling the cutout.

On the left engine, I decided to shut the mags off early to see what happens. Left engine stopped 4 seconds after shutting off mags, skipping the 33 seconds of sputtering.

 

[grafspee]

16 minutes ago, Nealius said:

So according to the pilot's notes:

800rpm, pull cutouts, wait for prop to stop spinning, shut off magnetos. So I did. Right engine took 33 seconds to stop spinning after pulling the cutout.

On the left engine, I decided to shut the mags off early to see what happens. Left engine stopped 4 seconds after shutting off mags, skipping the 33 seconds of sputtering.

 

This is so ridiculous. It makes me sick by watching this. 

I advice to cut fuel via tank selectors next to cut outs. This way you should avoid this engine splutter but engine will still keep running quite long before cuts out. Running engines up to 1500rpm will speed things up.

Edited December 2, 2023 by grafspee

[Nealius]

I have a suspicion that if I reverse the flow by turning off mags first then pulling the cutouts, it may work as intended.

[grafspee]

10 hours ago, Nealius said:

I have a suspicion that if I reverse the flow by turning off mags first then pulling the cutouts, it may work as intended.

That would be incorrect order because engine has to shut down due to fuel starvation not by lack of ignition.

So by shutting down fuel by fuel selectors is way closer then shutting engine via cutting off magnetos. I wish that ED would implement punishment for shutting down engines via magnetos by immediate fire of engine compartment, because when you cut magnetos and fuel is still introduced to inlet, hot fuel air mixture will come out of exhaust causing serious fire risk and on top of that those pressure carbs induce fuel even when engine is not rotating, so when engine stops fuel will pour out of engine inlet on the ground making small fuel puddle in quite short time. 

I just tested it and even when i cut off fuel via fuel tank selectors engines still get tis splutter at the lower rpm. Just same story perfect rpm run down to about 200rpm and then engines wakes up splatter loop with rpm spikes.

So at that moment switching magnetos off is probably only way to avoid this splatter loop.

Edited December 2, 2023 by grafspee

[hazzer]

Can someone from ED please confirm this issue (with all the merlin aircraft not just the Mosquito) is now being looked into and fixed. Please do not just close the thread as not a bug or reported. 

We have clearly raised an issue here and I fear just like a lot of them they fall on deaf ears. 

There is no question that the shutdown dynamics are wrong, even the startup ones aren't amazing. This is part of the simulation of these great aircraft, please improve it. 

[BIGNEWY]

We have a report open for the length of time the engine takes to shut down when cut off is pulled, there seems to be a difference with cold starts and hot, I will link this thread to the report for the team to take a look also. 

thanks

[Art-J]

BN forwarded the info where needed, but just for the record (figuratively and literally), I've experienced recently an engine shudown sequence which took 38 (thirty eight) seconds of poppin' and bangin' (25+ pops per engine) after pulling shutoff plugs, with extra overpriming fire animation (?!) thrown in as a "cherry on top".

Track below, recorded in current Open Beta. It's 28 min long so if anyone's still interested in watching, just fast forward to the end, it plays without desync (on my PC at least).

One aspect which is consistent with Nealius' latest video above is the fact that my mission was set to winter conditions, like his. Looks like low temps must affect this problematic aspect of simulation somehow.

 

2.9_Mossie_test.trk

[hazzer]

On 12/13/2023 at 1:07 PM, BIGNEWY said:

We have a report open for the length of time the engine takes to shut down when cut off is pulled, there seems to be a difference with cold starts and hot, I will link this thread to the report for the team to take a look also. 

thanks

Just to clarify it's not just the legnth of time (and it's not just the Mosquito). The fuel cut off, or the mixture going to idle cut off, removes the fuel from the engine... So there shouldnt be any backfiring once the cut off is selected. 

[Nealius]

Would be nice to have startups and shutdowns like this: smooth, no starter pistol pops, no massive flames. Even the failed starts don't sputter or pop.

 

Edited February 16 by Nealius

[grafspee]

On 2/16/2024 at 4:11 AM, Nealius said:

Would be nice to have startups and shutdowns like this: smooth, no starter pistol pops, no massive flames. Even the failed starts don't sputter or pop.

 

 

Indeed it would.