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View Full Version : Any thoughts on new neg G cutout post beta patch?


Targ
04-16-2011, 07:59 AM
This is directed at people that were thought it was off and to sensitive.

What are your thoughts on it now?

IvanK
04-16-2011, 08:05 AM
Pretty good.

41Sqn_Banks
04-16-2011, 08:16 AM
(old values were sneezing at .5G, and cut-out at .25 which we felt were dead on, but this apparently confused most of the players)


http://img685.imageshack.us/img685/4564/neggcutout1.jpg

The old values were right, the new values are wrong.

Wolf_Rider
04-16-2011, 08:23 AM
here's something to mine...

http://www.ww2aircraft.net/forum/archive/f-59.html

Extreme_One
04-16-2011, 08:32 AM
I couldn't get the engine to cut out last night no matter what I did.
I even ended up doing a complete push over loop and still the engine kept running. The revs were reduced but the engine didn't die even under extreme negative G.

Doesn't seem right to me.

Targ
04-16-2011, 08:43 AM
I dunno Ivan,

seems way off to me now. It did seem a bit sensitive before and may have needed to be tweaked a bit but now?



I pushed the stick all the way forward until a red out happened and the plane righted itself going in the opposite direction and the engine never sputtered or cut out. It did seem to lose some RPM but kept pushing the plane thru the air.

I did barrel rolls, loop de loops and everything else I could think of and the most noticable cut out was when pushing the stick all the way forward and pointing the nose straight down it did seem to lose RPM and than after a slow bit cut of very gently but came back to full power as soon as any pressure was lifted off the stick.

reflected
04-16-2011, 08:47 AM
I think the reality must lay between the two. Before it was a bit too sensitive, still it was closer to reality.

IvanK
04-16-2011, 08:54 AM
Err just tried the Quick Mission Hurri over Dover Max Boost good healthy push and hold RPM dropped to Minimum Boost to very low value and engine about 5RPM. Seems pretty reasonable representation of the effect.

Loops,Barrrel rolls etc are all positive G manoeuvre's Tarq so nothing should happen these. Try a genuine slow roll (thats using the full gambit of rudder to control nose position and roll rate plus a healthy push through the inverted and then co ordinated rudder pitch and roll in the last half .... tell me if the engine splutters.

Targ
04-16-2011, 09:01 AM
Yeah, no one doubts that the engine will slowly cut out now. It now seems to take a large amount of neg G to do so.

I can push the stick full forward and nose down and red out and reverse heading and the rpm's and boost do drop but the engine never cuts out or sputters.

IvanK
04-16-2011, 09:11 AM
What do you expect it to do STOP ?

Try starting in Level 1 G flight, max Boost about 10-15degrees nose up. Roll inverted and fly at -1G holding the canopy on the Horizon. It doesnt take long to end up with about 5RPM (counting the blades ... there is not much power being developed here), Roll back to 1G flight Engine eventually recovers as it should, You have wind milling RPM, Fuel, Ignition all you need so after 5 or so seconds it recovers..... as it should.

We now have both a Spitfire and Hurricane that allow normal GF type control inputs without a cough .... we couldn't do that previously. If you push a little more then the coughing and power drop occurs. IMO this is far closer to reality than what we had before. It also now matches a whole lot better to the descriptions of the effects by 2 accounts from current Early model Hurricane pilots in the original thread. ...:

"First, I can tell you that it does not require negative g to make the engine suffer from a shortage of fuel supply; a significant reduction of g down to, say, 0.3g can be enough to make the engine misfire. This can be experienced towards the top of a wing-over but I would estimate that the reduction in g needs to be maintained for 2 seconds or more before there are any effects. Undoubtedly, if the reduction in g was greater (to less than zero g) and particularly if the bunt was abrupt then the effect could be instantaneous. I have never, though, experienced any misfiring in turbulence; albeit, were the turbulence severe enough to produce g spikes to less than zero g, I would not rule out the possibility of the odd cough from the engine. Of interest to you I am sure is that on recovery from an episode of fuel starvation the engine recovers through a short period of over-richness shown by, I would estimate, up to a second of black, sooty exhaust before normal combustion is resumed."

No mention here of the engine stopping, also the pilot considers around 2 seconds of exposure before any real effects are noticeable. Again what we have is pretty close to this description.... certainly a whole bunch better than what we had before.

Extreme_One
04-16-2011, 09:30 AM
I'm no expert, just entering the debate with what I've read and picked up from previous sims.

I believe the engine would cut out if subjected to constant negative G

The early versions of the Rolls-Royce Merlin engine came equipped with a SU carburettor. When these aeroplanes performed a negative G force manoeuvre (pitching the nose hard down), fuel was forced upwards to the top of the float chamber of the carburettor rather than into the engine, leading to loss of power. If the negative G continued, the fuel would collect in the top of the float chamber, forcing the float to the floor of the chamber. This would in turn open the needle valve to maximum, flooding the carburettor with fuel and drowning the supercharger with over-rich mixture. This would lead to a rich mixture cut-out, which would shut down the engine completely, a serious drawback in combat.

This engine cut out no longer appears to be modelled with the current beta patch.

Wolf_Rider
04-16-2011, 09:41 AM
^ beat me to it




The early versions of the Rolls-Royce Merlin engine came equipped with a SU carburettor. When these aeroplanes performed a negative G force manoeuvre (pitching the nose hard down), fuel was forced upwards to the top of the float chamber of the carburettor rather than into the engine, leading to loss of power. If the negative G continued, the fuel would collect in the top of the float chamber, forcing the float to the floor of the chamber. This would in turn open the needle valve to maximum, flooding the carburettor with fuel and drowning the supercharger with over-rich mixture. This would lead to a rich mixture cut-out, which would shut down the engine completely, a serious drawback in combat.[1]

Negative G commonly occurs when manoeuvring to fire on an enemy aircraft in a dogfight. Moving the stick forward would starve the engine of fuel, producing a sudden loss of power. This would let the enemy get away, and if continued the maneuver would cause the carburettor valve to open, provide far too rich a mixture and kill the engine. During the Battles of France and Britain, the German fighter aeroplanes had fuel injected engines and therefore did not suffer from this problem as the fuel injection pumps kept the fuel at a constant pressure whatever manoeuvre were made. The German pilots could exploit this by pitching steeply forward while pushing the throttle wide open, the pursuing British aircraft being left flat footed since trying to emulate the maneuver would result in loss of power, or fuel flooding and engine shutdown. The British countermeasure, a half roll so the aircraft would only be subjected to positive G as they followed German aircraft into a dive, took enough time to let the enemy escape in most instances.

1 Price, Alfred. The Spitfire Story: Second edition. London: Arms and Armour Press Ltd., 1986. ISBN 0-85368-861-3 p78

IvanK
04-16-2011, 09:57 AM
This is becoming painfull and full of genearalisations and quotes from fairly generic accounts.
For those that haven't followed this discussion in the various threads understand these words below come from someone who currently flies a Hurricane I equipped with the early style carburettor affected by the cut out out issue and was asked specifically for his opinion. We have a similar though more abbreviated comment from another pilot current on similarly equipped aircraft. So read the following closely:

""First, I can tell you that it does not require negative g to make the engine suffer from a shortage of fuel supply; a significant reduction of g down to, say, 0.3g can be enough to make the engine misfire. This can be experienced towards the top of a wing-over but I would estimate that the reduction in g needs to be maintained for 2 seconds or more before there are any effects. Undoubtedly, if the reduction in g was greater (to less than zero g) and particularly if the bunt was abrupt then the effect could be instantaneous. I have never, though, experienced any misfiring in turbulence; albeit, were the turbulence severe enough to produce g spikes to less than zero g, I would not rule out the possibility of the odd cough from the engine. Of interest to you I am sure is that on recovery from an episode of fuel starvation the engine recovers through a short period of over-richness shown by, I would estimate, up to a second of black, sooty exhaust before normal combustion is resumed."

Quote from a current Hurricane I pilot !

Wolf_Rider
04-16-2011, 09:59 AM
"say, 0.3g" is uncannily close to "0.5/ 0.25" eh?


do you have a link perhaps... to see what else may be gleaned?








"The use of carburettors was calculated to give a higher specific power output, due to the lower temperature, hence greater density, of the fuel/air mixture compared to injected systems.[40] However, the Merlin's float controlled carburettor meant that both Spitfires and Hurricanes were unable to pitch nose down into a steep dive. The contemporary Bf 109E, which had direct fuel injection, could "bunt" into a high-power dive to escape attack, leaving the pursuing aircraft behind because its fuel had been forced out of the carburettor's float chamber by the effects of negative g-force (g). RAF fighter pilots soon learned to "half-roll" their aircraft before diving to pursue their opponents.[41] "Miss Shilling's orifice",[nb 7] a holed diaphragm fitted across the float chambers, went some way towards curing the fuel starvation in a dive; however, at less than maximum power a "fuel rich" mixture still resulted. Another improvement was made by moving the fuel outlet from the bottom of the S.U. carburettor to exactly halfway up the side, which allowed the fuel to flow equally well under negative or positive g.[42]



40 Hooker, Stanley Not Much of an Engineer London: Airlife, 1984. p62
41 McKinstry, Leo. Spitfire – Portrait of a Legend. London: John Murray, 2007 p205
42 Smallwood, Hugh. Spitfire in Blue. London: Osprey Aerospace, 1996 p135

Extreme_One
04-16-2011, 10:02 AM
The writer doesn't mention continued negative G effects.

What we had before the patch was too sensitive.
We shouldn't have suffered misfires and reduced revs because of turbulence so in that respect what we have now is (more) correct.

Now if I attempt to completely starve the carburettor by continually pushing negative G I do suffer from reduced revs as expected but I expect the engine to cut out after pushing negative G further.

Sure my expectations may well be wrong, the accounts I've read may be wrong and previous sims may have modelled this badly in the past.

IvanK
04-16-2011, 10:02 AM
Yes its currently about 5 threads below this !!!

http://forum.1cpublishing.eu/showthread.php?t=20462

Extreme One what do you mean by Cut out ? .... Prop stopped ? That wont happen if you have any forward airspeed it will windmill at very low RPM. This can easily be demonstrated in the current Beta following sustained negative G. In these circumstances there is pretty close to Zero thrust output from the prop.

Targ
04-16-2011, 10:04 AM
This is what we have now with the beta.

http://www.youtube.com/watch?v=LQesJO2otXo&feature=mfu_in_order&list=UL

Does a full red out with no engine cut out seem right?

I put some pretty good negative G moves in that vid with very little effect.

This is a huge change from before.

Extreme_One
04-16-2011, 10:07 AM
...

Does a full red out with no engine cut out seem right?
...

That's what I'm talking about. I don't think this is right.

Targ
04-16-2011, 10:16 AM
I am not a pilot nor do I know what "should" be right or wrong. Nor do most folks here.

This just seems like a huge swing in the other direction from before. I read all the threads Ivan and it seemed to me that the merlin engine neg G was off a bit and seemed to need some tweaking, what we have now is no small tweak but a 180.

Wolf_Rider
04-16-2011, 10:16 AM
Yes its currently about 5 threads below this !!!

http://forum.1cpublishing.eu/showthread.php?t=20462




erm... where?



"Further improvements were introduced throughout the Merlin range: 1943 saw the introduction of a Bendix-Stromberg pressure carburettor that injected fuel at 5 pounds per square inch (34 kPa; 0.34 bar) through a nozzle directly into the supercharger, and was fitted to Merlin 66, 70, 76, 77 and 85 variants. The final development, which was fitted to the 100-series Merlins, was an S.U. injection carburettor that injected fuel into the supercharger using a fuel pump driven as a function of crankshaft speed and engine pressures.[43]"


43 Lumsden, Alec. British Piston Engines and their Aircraft. Marlborough, Wiltshire: Airlife Publishing, 2003 p212

IvanK
04-16-2011, 10:18 AM
You dont call Minimum RPM a cut out ??? ... how much power and thrust do you think the prop/engine RPM combination is putting out with the RPM full scale anticlockwise ? You went from 3000RPM to something less than perhaps 1000RPM in a heartbeat !

Targ
04-16-2011, 10:25 AM
You dont call Minimum RPM a cut out ??? ... how much power and thrust do you think the prop/engine RPM combination is putting out with the RPM full scale anticlockwise ? You went from 3000RPM to something less than perhaps 1000RPM !

I also did a full neg G induced red out and noticed zero change in performence other than the RPM and boost gauge dropping.

I also notice that if I pushed the stick full forward and to the right it would cut out fast but a quick pull back than full forward and right again the engine would recover and continue on its merry way doing negative G's.

look at the 1 minute mark, odd to me at least.

doghous3
04-16-2011, 11:00 AM
Even judging by pilot accounts, they mention mis-fire which I presume is the sputter/cough and black smoke. That doesn't happen (or at least didn't to me whilst I was testing it) however you fly, the engine didn't cough black-smoke once.

IvanK
04-16-2011, 11:27 AM
"zero change in performence other than the RPM and boost gauge dropping."

RPM dropping to full minimum and Boost dropping to zero and even less IS an immense loss of performance !
The Engine has gone from producing full Combat Output to next to nothing. Boost and RPM is a measure of engine performance. .... thats a Cut to me.

Here is my attempt negative G throughout until the recovery.

http://www.youtube.com/watch?v=Sbn7sY8Lag0&feature=youtube_gdata

Wolf_Rider
04-16-2011, 11:38 AM
at what G is this happening at though?

Sauf
04-16-2011, 11:38 AM
I havent as yet tried any of the RAF a/c but have been following the arguments, Viper2000 posted this in the other thread, has anyone had a chance to compare in game (25 sec's in)?



http://www.youtube.com/watch?v=9BCl8RuME-M&feature=related

Viper2000
04-16-2011, 12:02 PM
erm... where?
Try this (http://forum.1cpublishing.eu/showpost.php?p=263770&postcount=94) from page 10 of the thread, complete with diagram.

The analysis linked to above only talks about mixture strength, and not the effects of that mixture strength on the engine.

During the lean cut, power initially falls away a bit slower than fuel flow because the design point was rich of stoichiometric, and therefore the temperature rise per unit fuel flow goes up. EGT would also initially rise. There might be incipient detonation, followed by misfiring as the mixture becomes too weak to support combustion (cylinder to cylinder variations in temperature and mixture strength mean that this behaviour will not affect all of the cylinders at the same time).

The lean cut will be less severe at lower power output under reduced positive g because fuel flow is less and so the fuel in the small chamber will therefore last longer; indeed at high altitude the engine might just go straight to rich cut. (Under negative g the small chamber empties much faster because fuel flow can escape from the holes in the small chamber which were provided to admit it.)

During the rich cut, power output falls because the Fuel:Air Ratio is approximately 2.4 times design point (which was already somewhat rich of stoichiometric for high power running). This lowers the combustion temperature considerably which kills the engine's BMEP.

However, combustion will continue because there is still oxygen and a source of ignition in the combustion chamber - the chemistry just changes so that it makes CO, H20, sundry cracked petroleum products, and of course some carbon (soot).

Boost shouldn't initially change during the cut unless engine rpm starts to fall, because the ABC doesn't know anything about the cut, and the supercharger pressure ratio is simply a function of its rpm; since it is geared to the engine.

Therefore, the chain of events is


Power reduction
Possible rpm reduction
Boost reduction


The rich cut is worse at lower engine power outputs because the fuel flow from the pumps is a fixed function of rpm, whilst the amount of fuel needed by the engine is a function of power.

At 30000' where the engine is only capable of producing about 500 bhp instead of nearly 1300 at its +12 psi FTH, the fuel flow during the cut would be 2.4*(1300/500) ~ 6.24 times that actually required by the engine. This is such a severe over-rich case that nett power output might fall to zero or even go negative (the prop will obviously windmill, so the engine won't stop; as long as it keeps turning the mags will keep going and so there will still be a spark and therefore recovery will follow).

Recovery time to float-controlled operation upon return to positive g would probably be longer at higher altitudes because the recovery depends upon the rate at which the carburettor can dispose of the excess fuel in the float chamber. This depends upon how much fuel can be carried away by the airflow through the venturi (which is mostly a function of ambient conditions & engine rpm; fuel temperature will also have a 2nd order effect).

At or below FTH, with the mixture about 2.4 times as rich as it should be, power will probably fall to about 1/3rd of the expected value, or perhaps a little less. I could do a cycle analysis if there is sufficient interest; the main unknown is the design point Fuel:Air ratio; I can't lay my hands on my copy of The Performance of a Supercharged Aero-Engine by Hooker et al at the moment...

DC338
04-16-2011, 12:10 PM
Feel like your banging your head up against a wall Ivan?

People if you don't think that it is effecting your performance go to wonder woman view roll upside down an keep at -1G and watch what happens to your airspeed.

It could perhaps do with a little bit more of a cough but it is definitely better than before.

Wolf_Rider
04-16-2011, 12:29 PM
Thanks there Viper, but that didn't quite get to the Ivank's pilot's quotes.

I had noticed earlier though in that thread, the references to the "general pilot's notes1943".






remember, this is late 1940 era, not '41/ '42/ or '43

Moggy
04-16-2011, 02:54 PM
Thanks there Viper, but that didn't quite get to the Ivank's pilot's quotes.

I had noticed earlier though in that thread, the references to the "general pilot's notes1943".






remember, this is late 1940 era, not '41/ '42/ or '43

Slow down there Tiger! Although the notes I provided were from 1943 a lot of it (not all) is still applicable to 1940. The reason is simple, the British were still using 1940 aircraft in 1943. Not as frontline aircraft but in O.T.U. schools for training. In the 1943 FAA training film Fleet Fighter, the pilots are trained on Mk.I Hurricanes.
So naturally, a trainee pilot will need notes for aircraft from 1940 through to 1943.

Viper2000
04-16-2011, 02:54 PM
Thanks there Viper, but that didn't quite get to the Ivank's pilot's quotes.

I had noticed earlier though in that thread, the references to the "general pilot's notes1943".






remember, this is late 1940 era, not '41/ '42/ or '43

The current pilot's quote is here:
http://forum.1cpublishing.eu/showpost.php?p=263445&postcount=93

The health warning I would apply to any current pilot's account is that the mod state of the airframe & engine will not be exactly as it was in 1940, and as the pilot says, the way that the machine is operated is also somewhat different.

In particular, a lot of display pilots will tend to stay at or below max continuous for the whole display. This reduces fuel flow, which means that the lean cut onset will be somewhat delayed under reduced positive g; the rich cut will actually be worse however.

The challenge is therefore to track down the mod state of the aeroplane and engine, and also the power settings used, so that we can make a reasonable apples to apples comparison with what we've got in the sim.

I think that this is complicated by the fact that there may well be other issues with the fuel metering model at the moment (ie misbehaviour at high altitude, at least in the last official patch for both Merlin and DB600 series), and so there may be an interaction between multiple bugs.

I think that we'll get there in the end, but since the model is much more complex than in IL2 it will inevitably take longer to get it right.

As for AP2095, these things get updated periodically, but since old equipment was still around in 2nd line units etc it still contains relevant material on old equipment.

As with all of these things, you've got to sift through carefully to build up a clear picture of what was really going on; most sources make all manner of assumptions as to the reader's frame of reference, which can make things complicated 70+ years later.

Deadstick
04-16-2011, 03:19 PM
I seem to remember reading that the developers wanted to make this 'the most realistic flight sim/combat sim ever' (or words to that effect).

They will of course not be able to get every Aircraft absolutely correct. But it sounds as if too much of a change in the other direction has been made. ( I have not run the new patch yet, so I have no personal experience in the change meade to the neg G cut-out).

Now the developers statement of intent about realism seems to have been compromised because a bunch of people (some seemingly more informed than others), pulled out 'facts' from sources that seem to fit in with how THEY think it SHOULD be.

Disappointed.

41Sqn_Banks
04-16-2011, 03:24 PM
Actually there was no Pilot's Notes General in 1940, the first edition was published in mid 1941 (June/July, I'm not sure about the month).
I have here a Pilot's Notes General (1st Edition), I just checked for anything about negative g cut-out, but didn't find any sentence. It mainly includes stuff about propellers and superchargers, though. Compared to the 2nd Edition it's rather short.

I also checked AP 129 Flying Training Manual Part 1 Landplanes (1937, reprint of 1941) but I didn't find a detailed description of negative g cut out so far.

Moggy
04-16-2011, 03:34 PM
Actually there was no Pilot's Notes General in 1940, the first edition was published in mid 1941 (June/July, I'm not sure about the month).
I have here a Pilot's Notes General (1st Edition), I just checked for anything about negative g cut-out, but didn't find any sentence. It mainly includes stuff about propellers and superchargers, though. Compared to the 2nd Edition it's rather short.

I also checked AP 129 Flying Training Manual Part 1 Landplanes (1937, reprint of 1941) but I didn't find a detailed description of negative g cut out so far.

The 2nd edition is where I found the information about negative G cutouts, starts on page 49. I took a few scans and posted them here;

http://forum.1cpublishing.eu/showpost.php?p=263432&postcount=92

41Sqn_Banks
04-16-2011, 03:39 PM
The 2nd edition is where I found the information about negative G cutouts, starts on page 49. I took a few scans and posted them here;

http://forum.1cpublishing.eu/showpost.php?p=263432&postcount=92

Yes I know, I have the 2nd edition as well. Problem is that the 2nd Edition is always critized that it wouldn't fit into the time frame :)

Moggy
04-16-2011, 03:46 PM
Yes I know, I have the 2nd edition as well. Problem is that the 2nd Edition is always critized that it wouldn't fit into the time frame :)

LOL uh huh, despite the fact...it actually does! :grin:

effte
04-17-2011, 05:51 PM
So we have a pilot with Hurri experience stating around 0.3 G, and a POH warning that it will happen at 0.5 G.

Now, consider the fact that the POH was intended to keep 19-year-olds from getting themselves into trouble. Which source is likely to err on the conservative side?

What we had before was almost certainly incorrect. Engines coughing due to turbulence - I don't think so! This had a huge impact on game play, as aircraft misbehaved during normal flight.

What we have now may be incorrect in the opposite direction, as engines perhaps should start coughing after prolonged reduced G and not only during actual -ve G. However, this has next to no impact on game play. The tactical advantage still goes to the pilots of the fuel injected planes, as the tactic employed should be a negative G push - in which case the Merlins will still flood and lose power if the unvary Allied pilot follows. I think we can be fairly certain that LW pilots didn't gently reduce the G load when they found a spit on their tail, waiting for the spitfire carb to empty and produce a lean cut.

41Sqn_Stormcrow
04-17-2011, 05:59 PM
Oh, it does have an impact but of course under non standard circumstances. So it should be there if it was there.

Viper2000
04-17-2011, 07:27 PM
I suspect that the problem is that IRL there would have been a lag between application of reduced or negative g and engine misbehaviour, such that flying around in bumpy air wouldn't cause problems. The model that we had in the last general release version had no lag, so going below 0.5 g for 0.01 second or something would cause engine trouble.

So at the simplest level what we need is the g limits from the previous patch, plus a lag so that misbehaviour only starts if the limits are exceeded for a length of time.

Since the lag was a function of the degree to which the limit was exceeded, the best solution would be to model the rates of fuel flow into and out of the carburettor as a function of g and just let the simulation sort itself out; that way you'd naturally generate both the lean and rich cuts without the need to hard-code behaviour...

Viper2000
04-17-2011, 07:53 PM
"Another thing we did was to devise a manoeuvre which was aimed at getting us out of a difficult corner if we ever got into one. This may sound very extraordinary, probably, to practising pilots today, but it consisted of putting everything into the left-hand front corner of the cockpit. If you saw a 109 on your tail, and it hadn't shot you down at that point, you put on full throttle, fine pitch, full left rudder, full left stick and full forward stick. This resulted in a horrible manoeuvre, which was in fact a negative-g spiral dive. But you would come out of it with no Me 109 on your tail and your aeroplane still intact." (Roland Beamont (http://en.wikipedia.org/wiki/Roland_Beamont))

Harvey-Bailey, A. 1995. The Merlin in Perspective - the combat years. Derby: Rolls-Royce Heritage Trust.

Of course, the engine should be somewhat unhappy during the manoeuvre; then again, the same might be said for the pilot's stomach...

jimbop
04-18-2011, 06:01 AM
I'm not qualified to comment on whether the current settings simulate reality but I can say that flying the Hurricane is really easy now. I was getting the hang of not getting close to neutral G pre-patch and post-patch you just don't realise there's a possible cutout problem any more. I get the feeling it is too easy now but as above, not qualified to comment.

Reality every time please!

unknwn
04-18-2011, 01:13 PM
"First, I can tell you that it does not require negative g to make the engine suffer from a shortage of fuel supply; a significant reduction of g down to, say, 0.3g can be enough to make the engine misfire. This can be experienced towards the top of a wing-over but I would estimate that the reduction in g needs to be maintained for 2 seconds or more before there are any effects. Undoubtedly, if the reduction in g was greater (to less than zero g) and particularly if the bunt was abrupt then the effect could be instantaneous. I have never, though, experienced any misfiring in turbulence; albeit, were the turbulence severe enough to produce g spikes to less than zero g, I would not rule out the possibility of the odd cough from the engine. Of interest to you I am sure is that on recovery from an episode of fuel starvation the engine recovers through a short period of over-richness shown by, I would estimate, up to a second of black, sooty exhaust before normal combustion is resumed."

This quote could indicate that previous values were right but engine misfire shouldn't occur instantly like it used to. It should take 2 secs of G reduction (~0,3G) for effect to occur while instant cut out should occur when higher negative G is reached.

winny
04-18-2011, 01:24 PM
Here's the opening sequence from "The Battle of Britain"

The Hurricane does a barrel roll and you can hear the cough and see the smoke.

http://www.youtube.com/watch?v=BNOKXfZTEAE

It seems pretty quick to me.

Winger
04-18-2011, 01:29 PM
Just as usual.The slightest whining in the community about a probable wrong performance reducing thing on an allied plane and it gets fixed immediately (no matter if it actually WAS historically correct or not).
And the 109? Ist STILL much too slow, can be outturned (as its supposed to) outclimbed and outspeed by the Spit. Thats just not right DEVS!!!
I have been sick of that from the ROF devs but seemingly this here is not a bit diffrent...

Winger

Moggy
04-18-2011, 01:36 PM
Just as usual.The slightest whining in the community about a probable wrong performance reducing thing on an allied plane and it gets fixed immediately (no matter if it actually WAS historically correct or not).
And the 109? Ist STILL much too slow, can be outturned (as its supposed to) outclimbed and outspeed by the Spit. Thats just not right DEVS!!!
I have been sick of that from the ROF devs but seemingly this here is not a bit diffrent...

Winger

And we still do not have the Battle of Britain Hurricanes or Spitfires...the 12 lb'ers!

My point is this, if you feel that upset about the 109s...why not make a new thread about it, present some evidence and make your case? Whining about it on a thread not even related to your point is well pointless isn't it?

Winger
04-18-2011, 01:46 PM
And we still do not have the Battle of Britain Hurricanes or Spitfires...the 12 lb'ers!

My point is this, if you feel that upset about the 109s...why not make a new thread about it, present some evidence and make your case? Whining about it on a thread not even related to your point is well pointless isn't it?

Neither do we have the E4 wich was actually the 109 wich was present in the majority of numbers in the BOB.
I dont make a new thread because i feel that this thread here is just the right one.
A thread that has a feature as topic that directly affects the performance of one of the planes (and therefor actually effectively REDUCING the relative performance of the opposite plane) IS in my opinion related to my concern.
But hey. Why dont you just ignore what i write instead of flaming me?

Cheers!

Winger

Viper2000
04-18-2011, 02:03 PM
Firstly, life would be a lot simpler if people actually read the original thread (http://forum.1cpublishing.eu/showthread.php?t=20462) (yes, all of it!) before throwing fuel on the fire in here; it's only about 10 pages long, and a lot of this stuff, such as the BoB video, has already been posted there (by me, on page 1 as it happens) and discussed at length.

Secondly, if we want this sim to be accurate then the performance of the Bf-109 is totally irrelevant in a thread discussing the performance of the Merlin engine.

I for one don't care about "balance" issues in the slightest; I want all the aeroplanes to be simulated as accurately as possible, and the relative performance that emerges from that is just the relative performance that emerges - I'm interested in flying the aeroplanes, not playing top trumps to decide which aeroplane is "best".

III/JG11_Simmox
04-18-2011, 02:04 PM
meh
doesnt feel or look as good imo
gotta have a decent balance between real and virtual i say,for the sake of gameplay

my limited time in the spit or hurri now shows me i dont half to half roll to follow the 109 when it pushes down to escape now.just push past his line then straighten up,and back to full power,no stutters or cough,nothing

id expect a carby fed engine to be bilging black rich unburnt fuel and take a small time to recover from the drown,after such a sustained -G on the engine
but it clears instantly as soon as 0 G is recovered

fix the climb rate on the 109 and i couldnt care less about them pommie planes:grin:

Moggy
04-18-2011, 02:06 PM
This thread has nothing to do with 109s does it? Re-read your post again...what are you really offering to the topic? I'll show you what I mean, earlier in the thread myself and Banks posted about what the RAF were telling new pilots about negative G cutouts in the RAF Pilot Notes General.

http://forum.1cpublishing.eu/showpost.php?p=263432&postcount=92

Now compare it to this...

"Just as usual.The slightest whining in the community about a probable wrong performance reducing thing on an allied plane and it gets fixed immediately (no matter if it actually WAS historically correct or not).
And the 109? Ist STILL much too slow, can be outturned (as its supposed to) outclimbed and outspeed by the Spit. Thats just not right DEVS!!!
I have been sick of that from the ROF devs but seemingly this here is not a bit diffrent..."

If you're going to add something, make it relevant to the thread and show some evidence. If you don't have evidence, then it's just opinion isn't it? There are people genuinely trying to make things as authentic as possible and your post really doesn't help. Imagine if I had posted something similar on a 109 thread about engine management...

"Just as usual.The slightest whining in the community about a probable wrong performance reducing thing on an axis plane and it gets fixed immediately (no matter if it actually WAS historically correct or not).
And the Spitfire? Ist STILL much too slow, can be outturned, outclimbed and outspeed by the 109. Thats just not right DEVS!!!
I have been sick of that from the ROF devs but seemingly this here is not a bit diffrent..."

I'd be flamed to hell wouldn't I and quite rightly so! If you're going to contribute then please contribute but do it sensibly, every titbit of information will help make this a better sim for everyone.

winny
04-18-2011, 02:16 PM
Firstly, life would be a lot simpler if people actually read the original thread (http://forum.1cpublishing.eu/showthread.php?t=20462) (yes, all of it!) before throwing fuel on the fire in here; it's only about 10 pages long, and a lot of this stuff, such as the BoB video, has already been posted there (by me, on page 1 as it happens) and discussed at length.



And look what happened, they 'fixed' it...

Any thread on this subject is valid as long as the 'fix' still exists.
Due to ill informed people everyone now has an unrealistic Merlin. The weight of evidence in both threads is overwhelming.

I'm a Spitfire fanboy, no apologies, but I don't want an unrealstic advantage.

Just a tick box for "Laws of physics within Carb - on/off" would do.
Or "Carb gravity field generator - on/off :-P

III/JG11_Simmox
04-18-2011, 02:30 PM
yea yea i heard ya the first time

but i dont think your right here
fact is WE are the ones going to have to put up with you guys in your supermarines and hurri;s
and the fact is well known,you allied guys cant be trusted to keep *ACCURACY* accurate:)

its a community thread and people are voicing there concerns on what yet again appears to be the FEW getting the goods on the majority.

it was changed without a consensus ,vote,raise of hands,nada,and now we know that its not all that impressive to the players.


oh and there is a thread on 109 FM quite interestingly enough.didnt make the patch though did it?
how rude:)

Viper2000
04-18-2011, 02:32 PM
I don't think that anybody in the original thread was asking for anything other than realistic performance; in fact the thread is basically devoted to trying to work out what realistic performance should be, rather than stridently crying out for any sort of "fix" at all.

If people were asking from an exemption from the laws of physics to make things "easier" for then they were doing so elsewhere.

I don't see much point in duplicating threads every time a patch or a beta patch comes out. It's a lot of wasted effort for all concerned, and it risks the loss of research work in the event that somebody decides to clean away old threads.

Moggy
04-18-2011, 02:33 PM
Simple question then for you 2...what are the current negative G cutouts set to for the Hurricane and Spitfire with this beta patch?

Winger
04-18-2011, 02:59 PM
Simple question then for you 2...what are the current negative G cutouts set to for the Hurricane and Spitfire with this beta patch?

Cutout at -X g, no cutout at +X g. Like stated in the patchnotes...

Winger

bw_wolverine
04-18-2011, 05:09 PM
To me it sounds like this is a situation where the game can't really appropriately simulate the effect of the carburetor and a 'fudge' has to be made.

Setting the effect to 0.5g, etc as per actual notes is probably not going to give the accuracy that people want. I doubt the game is simulating where the fuel is in the tank, etc etc. It's probably just saying "0.5g is achieved, make engine stutter". More factors are seemingly involved than can be accomodated if I understand what I've been reading here and elsewhere to be correct.

So, the change is made to make it only -g that induces the effect and we've got some people saying that it's now too much the other way.

I'm sure a happy medium will be found.

DISCLOSURE: I at first thought that the change was BAD ("should be realistic levels! Don't change it for the n00bs!, etc.") but after considering the fact that this kind of effect in the engine is based on so many little mingling things, I'd rather they spend more time on getting frame rates improved, adding FFB, and making trees hazardous to plane health than agonizing over the intricacies of the engine to make a carburetor fault behave perfectly.

Make the plane perform as close as you can to real. Whether or not the cut out starts at .5 or at -.1, I don't really care.

Viper2000
04-18-2011, 05:57 PM
Downloading the patch now. I didn't fly the beta, so this will be interesting...

TBH I'm expecting the correction to be somewhat too far the other way.

I don't think that a significant fudge has to be made, because the sort of behaviour that analysis predicts isn't exactly going to tax a modern CPU; I suspect that the main issue is that coding up this sort of thing is a bit of a pain and there are other priorities.

But I have great confidence that we'll get there in the end.

IvanK
04-18-2011, 11:44 PM
To me it sounds like this is a situation where the game can't really appropriately simulate the effect of the carburetor and a 'fudge' has to be made.

Setting the effect to 0.5g, etc as per actual notes is probably not going to give the accuracy that people want. I doubt the game is simulating where the fuel is in the tank, etc etc. It's probably just saying "0.5g is achieved, make engine stutter". More factors are seemingly involved than can be accomodated if I understand what I've been reading here and elsewhere to be correct.

So, the change is made to make it only -g that induces the effect and we've got some people saying that it's now too much the other way.

I'm sure a happy medium will be found.

DISCLOSURE: I at first thought that the change was BAD ("should be realistic levels! Don't change it for the n00bs!, etc.") but after considering the fact that this kind of effect in the engine is based on so many little mingling things, I'd rather they spend more time on getting frame rates improved, adding FFB, and making trees hazardous to plane health than agonizing over the intricacies of the engine to make a carburetor fault behave perfectly.

Make the plane perform as close as you can to real. Whether or not the cut out starts at .5 or at -.1, I don't really care.

Absolutely spot on Wolverine.

There is room to tweak this still further. The Changelog text was an unfortunate (maybe a language issue) use of the term "some users found this confusing" this lead to all this they are dumbing down the sim to placate some users opinion. That is just total BS. The Devs are working their hardest to get things as accurate as they possible can. I am sure you will see a little more adjustment in this area.

klem
04-19-2011, 12:15 AM
This is directed at people that were thought it was off and to sensitive.

What are your thoughts on it now?

First of all we no longer have a ridiculously overmodelled reduced G effect for the Merlins.

Secondly we do have an engine cut on heavily reduced or -ve G which hits performance and is a lot nearer to the truth than the original. I haven't had the opportunity to pitch it against a diving 109 yet.

Lets think about what might be right. We all want that. Someone posted reduced/negative G notes from the pilots General Flying Notes, well these are not specific Merlin notes. I set a lot of store by a current Hurricane I pilot's actual flying experience and opinion and frankly there's a lot of guessing and wishful thinking going on here from people who have never flown one themselves. Even carefully calulated assessments may not be correct although Viper's calculations are detailed, explanatory and pretty close to what our friendly pilot has said. Just how much nearer to the truth do you think you are going to get without specific Merlin notes and performance charts?

So much for what might be right.

But, is it now modelled correctly? I don't know, I suspect it might be a little off (pure speculation), and I was surprised when Luthier said:
"* Completely removed overload assessment from carburetters. Rolls-Royce engines will now cut if overload is negative, and will not cut if it is positive. (old values were sneezing at .5G, and cut-out at .25 which we felt were dead on, but this apparently confused most of the players)"

His original values of 0.5G and perhaps 0.25G weren't that far off what we have been hearing from good sources. So why did we have problems? One or two people may have touched on the answer. If the onset delay was not included or modelled reasonably we may well have had problems because the starvation and rich cut were not instantaneous but they appeared to be instantaneous in level flight assuming there was some turbulence.

Currently we have a workable Merlin engine model. The engine does cut, as IvanK has demonstrated, and more sensibly than it did before. No it won't STOP if only due to windmilling and if I understand Viper correctly he is saying that there may still be combustion occurring at some level. The 109s still have an advantage diving away.

In the longer run 1C may have time to review how they are modelling this and perhaps find a need to revise it, just as they may need to look at the 109 pilot's gripes, but meantime the Merlin is reasonably on track.

At the moment there are now many other issues that need sorting (which may well include any performance issues for the 109).

41Sqn_Stormcrow
04-19-2011, 12:44 AM
I really hope that during the following patched they do find a good tweak for the Merlin that is fairly representative for the realistic behaviour. With the current patch the behaviour is just like old IL2. Back then it was alright but now completely different story.

Also the 109 needs an overhaul. I did many repetivite flights and I think the performance is not quite right on some points. I cannot yet tell what exactly apart from the speed issue. However my perception may be falsified by the uber-AI capabilities which also needs to be addressed in one patch or another.

But with the new patch the dev team showed what they are capable of and if this continues like this CoD will be a benchmark for flightsims for the next 10 years as the old IL2 was in its time.

IvanK
04-19-2011, 12:58 AM
Please read this related post from the realism thread:

http://forum.1cpublishing.eu/showpost.php?p=267479&postcount=33

Wolf_Rider
04-19-2011, 01:13 AM
have you found that link yet? :)

jimbop
04-19-2011, 02:58 AM
Please read this related post from the realism thread:

http://forum.1cpublishing.eu/showpost.php?p=267479&postcount=33

I have no problem if cutout is now modelled correctly since the planes are easier to fly and I like them. I am not qualified to comment.

However, the change log did state that the devs thought they had it right in the first place. I think this is where the dumbing down comments stem from. I.e. they changed the model from what they thought was correct to something else. Also, I don't think there's anything wrong with luthier's English, assuming he wrote it!

reflected
04-19-2011, 06:28 AM
After further testing, I must admit that Merlins were more realistic pre-patch. The only thing that's better now is that one can fly straight in turbulent weather without losing engine power - that was nonsense.

Voyager
04-19-2011, 08:00 AM
[...]
Currently we have a workable Merlin engine model. The engine does cut, as IvanK has demonstrated, and more sensibly than it did before. No it won't STOP if only due to windmilling and if I understand Viper correctly he is saying that there may still be combustion occurring at some level. The 109s still have an advantage diving away.
[...]

A dead engine should windmill if the prop is not feathered, simply because you're driving an airfoil through the air at an angle of attack. It's like blowing on a pinwheel, except you're blowing at 200-300mph. The difference is that instead of the engine providing the energy to turn the prop, you forward airspeed is being sapped to drive the system.

In a piston engine, if the crank is rotating, and the spark plugs functioning, once the fuel/air mixture reaches a combustible ratio, provided nothing else is wrong, the engine will start. This include the entrance conditions of either no fuel at all, or no air at all, though in the no air case, I would be worried about other systems failing before the correct fuel/air ratio is resumed.

That was one of the things that bugged me about the engine modeling in late Il-2: if the engine was shut down, for whatever reason, the prop was glued in place until you tried to restart, and then the restarts were always flaky at best.

Turbines and turboprops are a different kettle of fish, because they've got a howling gale going through them when in the air, which they don't in a ground start.

*Buzzsaw*
04-19-2011, 08:24 AM
Salute

The engine was clearly too sensitive before, there are no reports of aircraft suffering the fuel starvation simply because of turbulence, in fact there are quite a few accounts of Allied pilots flying in stormy conditions without any mention of this. (see BoB Tuck's bio, Sandy Johnstone's bio, etc. etc.)

Second, those who want the Merlin to actually die, stop and have to be restarted, have the wrong expectation. These engines would temporarily suffer a loss of power, but I have NEVER read in any bio or account a RAF pilot say his engine actually died because of negative G. The fact you could kill the engine in the originally modelled FM, is a clear indication it was overdone.

Third, there is a time/intensity factor. Negative G cutout happens when you:

a) induce a lot of neg G abruptly

or

b) maintain smaller amounts of neg G for a longer period of time

Cutout shouldn't happen when small amounts of neg G are introduced momentarily. An engine will fire through this type of occurence simply because of the existing inertial effects, as well as the overflow space within the float bowl.

It seems to me Merlin engined aircraft have a clear disadvantage with the currently modelled effect, cutout is clearly modelled, there is no reason to make further changes.

unknwn
04-19-2011, 11:43 AM
Third, there is a time/intensity factor. Negative G cutout happens when you:

b) maintain smaller amounts of neg G for a longer period of time


Cutout shouldn't happen when small amounts of neg G are introduced momentarily. An engine will fire through this type of occurence simply because of the existing inertial effects, as well as the overflow space within the float bowl.

It seems to me Merlin engined aircraft have a clear disadvantage with the currently modelled effect, cutout is clearly modelled, there is no reason to make further changes.


It was mentioned before that engine misfires could occur at G reduction (0,25-0,5G - values which we had before) lasting a longer period of time ( 2 seconds) but not instantly like it used to. And currently we don't have this in game. And if this information is true i don't see why there is no reason to make further changes.

41Sqn_Stormcrow
04-19-2011, 07:08 PM
I think we should have something in between the prepatch and postpatch behaviour. Before it was over sensitive. Now it is like old IL2 which was far too easy and unrealistically insensitive to low g.