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Another look at turn times

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I hope that this thread gets updated post release of 2.012.

In my opinion it is one of the best data driven analyses of the current FMs.

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Preliminarily I'm at 21s and 19s instead of 25s and 22s as stated, turning at 160-170mph. You can probably chop off another one or two seconds by going from 9lb to 12lb or 16lb, so yes, it's a very good turn fighter.

 

First aircraft tested to behave completely different in game than stated by the developers.

Just going against it in QMB's, I'd say the closest thing it reminds me of in regard to turn time is the I-16.

 

It's also not as vertically challenged as I expected either.

Edited by hrafnkolbrandr

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If I could, I'd like to engage in an interesting thought experiment. Given the information we know about the P-51D, what does the turn time for this aircraft come out to on paper?

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Just going against it in QMB's, I'd say the closest thing it reminds me of in regard to turn time is the I-16.

 

It's also not as vertically challenged as I expected either.

It really feels like a super I-16 which Im not complaining about, i love the I-16. Oddly enough it also reminds me of the hurricane from clod.

 

The spit was no slouch in the vertical though. It seems a lot of people have the impression it was a poor or mediocre climber. Sure it was outclimed by a 109 but then again most anything is. Im pretty sure even the MkV could outclimb the 190 and I am almost positive that the mkIX could outclimb them. (feel free to correct me on these facts I am just going off of fuzzy memories of things read a while ago.)

Edited by TheJay13

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If I could, I'd like to engage in an interesting thought experiment. Given the information we know about the P-51D, what does the turn time for this aircraft come out to on paper?

In reality:

From US reports you can only gather that a plane turns either good or bad or average. They never made tests like Soviets did. We also know form the training video that the P-51 has mild stalling characteristics and that it "doesn't whip over like some other planes do" and that recovery from spin is completely normal by slight rudder input and nose down attitude.

In sims:

Turn time for P-51D? Depends on power rating and fuel state. With 67'power about 30% of fuel the plane can hold a sustained turn at about 20 sec. With full wing tanks about 23sec but with full fuel its going to be impossible to hold in DCS. 75'hg would cut down the turn time by 1 sec probably, at least from what I got from other sims WT/IL2/AH.

Conclusion

I don't think that P-51D can tell us much about P-40E though. Those planes are so different in design and engine that it is realy hard to compare. Even P-51 Mustang MK1A, using the same engine as P-40 does, was faster than the Warhawk and Spitfire that used a more powerfull Merlin. :coffee:

Edited by =LD=Solty

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Well, it's informative that multiple pilots have stated that the P-40 was a better turning plane than the P-51. I just get the feeling that there's something missing from the mathematical models, and this interests me. 

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Well, it's informative that multiple pilots have stated that the P-40 was a better turning plane than the P-51. I just get the feeling that there's something missing from the mathematical models, and this interests me.

AnPetrovich said that P-40 had "ощутимо завышенное индуктивное сопротивление" (i.e. inductive resistance was too big) - https://forum.il2sturmovik.ru/topic/2965-voprosy-razrabotchikam-2/page-52?do=findComment&comment=542513https://forum.il2sturmovik.ru/topic/2965-voprosy-razrabotchikam-2/page-52?do=findComment&comment=543035

Edited by bivalov
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Yes, great news. Can't wait for 2.012!

 

(And yes, I absolutely intend to keep the calculations up to date.)

Edited by JtD

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AnPetrovich said that P-40 had "ощутимо завышенное индуктивное сопротивление" (i.e. inductive resistance was too big) - https://forum.il2sturmovik.ru/topic/2965-voprosy-razrabotchikam-2/page-52?do=findComment&comment=542513https://forum.il2sturmovik.ru/topic/2965-voprosy-razrabotchikam-2/page-52?do=findComment&comment=543035

 

Can someone de-google translate this, because I'm not sure I understand what he was meaning here:

 

cac45.jpg?width=1460&height=458

Edited by Kai_Lae

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There is a P-40N sheet that states it is the best turner in the US arsenal, but in any other way it is inferior. It also stated that the P-40 had big issues with instability. I'll try to find it later. It is on this site somewhere:

http://www.wwiiaircraftperformance.org/P-40/P-40.html

Edited by =LD=Solty

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Han has given the figures for the Hs129, so I've updated the first post. Personally, I'm a little bit disappointed. Utilizing maximum power and maximum lift coefficient, it still should be possible to complete a sustained turn in less than 25s, which would then agree with my expectations.

 

I have now also included the Spitfire, for which we still don't know engine power in game at 3000/9lb at sea level. I've taken the figures I found in the manuals. It may look odd at first glance that the engine change changes the efficiency of the aircraft, I suppose this is mainly an effect of flying at as low lift coefficients as used for the Spitfire turning performance.

 

Waiting for the new patch, then I'll do some in game testing. I wouldn't be surprised to find some numbers change considerably.

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I mean, obviously we're assuming all the figures from the devs are correct.

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Yes, but they are not all from the same flight condition. A Spitfire which uses a cl of 0.9 is not really comparable to a Yak-1 that utilizes 1.3. Going by the trend over all data points given, this would account for an about 5-10% difference. It's that which I want to find out - how do the number look with the aircraft in as similar as possible sustained level turns.

 

Edit: Attached a chart with the data points and an added trend line.

post-627-0-69165600-1503733522_thumb.jpg

Edited by JtD

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You should use data point labels if possible so we can easily see which ac are the outliers. It does appear there are quite a few that diverge from trendline. Also that there is some sort of linear relationship between derived CL and efficiency.

 

It's interesting isn't it. That there is some underlying decrease of drag and or increased prop efficiency when increased CLs are being utilized. Or maybe those FMs are just older generation and there is something wonky about them. Like great wings.... Hmm. Obviously overall induced drag and/or prop losses are being modeled somehow differently for each airframe. A straight line would indicate that a lower CL is also overall correlating to a lower turning efficiency. Which one would expect with aircraft like a Junkers perhaps as compared to a fighter. Certainly you would get more form drag anyways.

 

Different polars would obviously give different drags for a given Cl, but you assume all polars are identical in your formula, bacuase you are simply taking a gestalt of the efficiency of the airframes.

 

So that difference from your formula vs the in game modeling of the polars / 3D wing drag/lift explains perhaps idiosyncratically part of the variation from trendline. However one would expect that if all fighter aircraft used CLmax of between 1.35 to 1.65, that it shouldn't be much different between them. .. and form drag ought to be fairly similar too... I wonder if the CLmax for the Spitfire was really so much lower than the Yak and LaGG (I know it's the same polar as the P-40, basically... just with more efficient wing tips...)

 

So the trendline might be usefully for that.

 

Still something strange is in the state of Denmark for the extremely efficient Soviet fighters along with variations between individual fighters which should be similar in efficiency. Just from these numbers. Because what we are seeing is big variations in either form drag, or prop efficiency, if these data points are all fighters. I'd like to see if 3D polars of the wing shape contribute as well to turning efficiency. (I am sure they do)

Edited by Venturi

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 I wonder if the CLmax for the Spitfire was really so much lower than the Yak and LaGG (I know it's the same polar as the P-40, basically... just with more efficient wing tips...)

 

 

It isn't.   The CLmax in game is, using the tech spec figures to calculate it from stall speeds:

 

Spitfire Vb 1.33-1.34  

Lagg-3      1.23-1.24

Yak-1        1.30-1.31

P-40         1.32-1.35

 

What the CL is during JtD's tests - or the tech spec turn time data - I have no idea.

Edited by unreasonable

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You take turning speed instead of stalling speed and load factor*weight instead of just weight, and you get to figures I'm listing in the 10th column. Load factor is in column 9.

 

Anyway, I'm looking forward to the FM revisions and expect to get some different numbers for some aircraft from the devs, and a new set of numbers from in game tests. I don't think there's a true point in making a detailed analysis with the current version of the game.

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Thanks for clarification. At least you will have the analysis settled and ready to have the new data plugged in.  I wonder if the new FM changes will alter the performance figures much, as opposed to stability and handling, but I agree  it seems pointless to do anything until the changes are bedded in.

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 I don't think there's a true point in making a detailed analysis with the current version of the game.

 

Nope :)

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109 feels way more stable in this patch. Easier to shoot with for sure and I can finally feel the "weight" of the plane when flying. At least for me, that sensation of gliding is gone and the rudders actually help out a lot during maneuvering. Overall, it is a positive impression and feels more realistic (even though I never really did fly one 109 IRL lol). What do you guys think of the 109 and its turning abilities now?

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109 feels way more stable in this patch. Easier to shoot with for sure and I can finally feel the "weight" of the plane when flying. At least for me, that sensation of gliding is gone and the rudders actually help out a lot during maneuvering. Overall, it is a positive impression and feels more realistic (even though I never really did fly one 109 IRL lol). What do you guys think of the 109 and its turning abilities now?

Pretty much what you think.

 

All the changes on Bf-109 and on other planes also have taken this sim a big step in right direction. I think all planes feel more real now, pretty close what you could expect.

After the improved FM came to the beta testing, I could not fly the official version anymore. I tried a few times but it felt so "obsolete" that I wen't straight back to beta.

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109 feels way more stable in this patch. Easier to shoot with for sure and I can finally feel the "weight" of the plane when flying. At least for me, that sensation of gliding is gone and the rudders actually help out a lot during maneuvering. Overall, it is a positive impression and feels more realistic (even though I never really did fly one 109 IRL lol). What do you guys think of the 109 and its turning abilities now?

Yep, It was in that place between a kite and a baloon. It flies very nicely now. I don't like how planes in BOS like to helicopter a bit, but nothing is perfect. Still the 109 now feels like it actually has weight and it actually has proper stiffness on ailerons and elevators. You realy do want to avoid steep dives and use the horisontal stabilizer trim to get out of dives.

 

Very nicely done.

 

And have you guys seen the P-40E? :D It feels goooooooooooooooood. No more little rudder imputs that kill you. :)

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I think turn times are not changed with the new FM. The changes are in rolls and handling. Practically for me it is, as a brand new game. Only the skins remain. The FM is completely different addressing many shortcomings particularly boring to real pilots (like rudder behavior). The FM is more demanding now. Before you can turn arround with no rudder input and still be coordinated. Now it is not so, the FW 190 requires rudder in turns, the 109 too, I did not test other planes.

You cannot deploy flaps without penalty anymore (maybe I am wrong).

Edited by JG27_Kornezov

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Good thread. Was there a patch since this thread was created? I'm asking as I'm curious about the 109. I think it feels good now that I'm figuring it out but only wonder if the elevator is now just a touch too stiff. If the calculations say it is then I'd like to know so I'm not being a "Luftwhiner".

 

I've been trying it every patch since release and I'm finally really happy with it. I only just got active in the past two weeks. I knew it would be good so I kept buying it so it wouldn't die.

 

Anyway, thanks for the info! Look forward to any updates.

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The following is a comparison of the turn times given by the developers here and my C++ simulations. In general there is reasonably good agreement when it comes to the Russian fighters whereas the German fighters seem to be underperforming a bit.

 

Also attached is a “doghouse” plot showing the relative stationary turn rate for the Yak s69 and Me-109G2 with the developers numbers included as point marks. Note that the plots for the Yak should be extended a little bit to the left giving slightly better turn rates at minimum speed since when I did the simulation I was assuming a Clmax of 1.35 and not the 1.39 that the developers use AFAIK. However, this does not change the fact that the Me-109 G2 should IMHO based on the simulation results be much better in a turn fight than it is currently modeled. At SL they should be about on par but with increasing altitude the more powerful engine on the Me-109 becomes telling.

 

Of course, my C++ model is just like the developers quite complex and you have in the same way to judge the results by correlation to the output with IRL data. That being said I have been tuning it for more than 10 years so I’m inclined to trusts the results but I would be glad if someone else had a look at this as well to verify the results. Maybe JtD? I know you have an Excel based turn estimator and it would be good to see if you come to the same conclusions.

 

Also note that I have deliberately excluded the Spitfire Mk5 from the comparison because the turn rate figures in the developers notes for the Spitfire are way too high and probably the result of some typo: The Spitfire stationary turn rate at SL should be in the order of 16 s, not the 22-25 s stated in the developers notes. But again, this must be some sort of typo because the Spitfire in-game seems to turn much better than that.

 

post-23617-0-63928600-1514726643_thumb.gif

post-23617-0-91015600-1514726666_thumb.gif

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Holzauge, do you have turn times, from real world tests? The results from your simulation hits data for the VVS fighter. But why is the difference in case of 109 so great, especially in 3km?

As far as i know, the devs are still searching for the correct Prop data(DD 138) of the VDM Propellers. Could this be an explanation?

Edited by L3Pl4K

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Holzauge, do you have turn times, from real world tests? The results from your simulation hits data for the VSS fighter. But why is the difference in case of 109 so great, especially in 3km?

 

It is due to the engine: The DB keeps the power and even increases it up to 3 Km while the Klimov changes supercharger gear. You can improve the stationary turn rate in two ways: Either increase Clmax or wing area which will move the left part of the doghouse curve up to the left or increase power which will move the right hand part of the doghouse curve up to the right. In fact the dashed 6 Km figures are a perfect example: If the Yak had the same power as the Me-109 there, it too would have the right hand red dashed line at more or less the same position as for the Me-109.

Edited by Holtzauge

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As far as i know, the devs are still searching for the correct Prop data(DD 138) of the VDM Propellers. Could this be an explanation?

 

No, I don't think the prop efficiency can explain it: In order for this to be a factor then Russian prop technology would have to be vastly superior to German and if it is one thing I have concluded doing my C++ simulations it is that there is little to choose between Allied an Axis prop technology: Sometimes different solutions were used, e.g. wooden propellers, hollow steel, 4-blade or wider 3-blade but in the end as long as the propeller solidity (number of blades x area), power loading and tip speeds etc were similar then the efficiency was pretty similar.

 

But you are right when it comes to the G2 at 3 Km: The 20% difference is huge and I don't know how they arrived at the figure of more than 28 s. OTOH the Fw-190 is now at 28 s turn time at 3 Km in the developers notes (i.e. pretty much spot on compared to my C++ estimate) and remember that before the latest Fw-190 tuning the developers notes stated 34.3 s.

Edited by Holtzauge

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Could you make simulation for other fighters from BOX? Could be interesting to compare your calculation with the data from the game.

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Which plane did you have in mind?

 

Edit: Unfortunately it looks like this will have to wait until next year since my wife has this silly idea that Champagne and Maine lobster is a better way to spend New Years eve compared to compiling C++ code. Ah, the sacrifices you have to make as a married man....... :rolleyes:

Edited by Holtzauge
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Thanks for posting. Would be interesting to see the F4 and the other Russian fighter types as well. Especially since the balance has changed here since the FM update.

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Which plane did you have in mind?

 

Edit: Unfortunately it looks like this will have to wait until next year since my wife has this silly idea that Champagne and Maine lobster is a better way to spend New Years eve compared to compiling C++ code. Ah, the sacrifices you have to make as a married man....... :rolleyes:

 

While it would take some work, it would actually be interesting to see all of them. Personally I'm interested in the 202, as I've often wondered if there's something missing from that plane. Right now it just feels like a weaker 109, with the only differences being better elevator authority and a better roll rate. 

 

Outliers would probably show areas where further investigation may be warranted. 

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Does your model incorporate the drag / 3d wing polar from open slats on the 109.... 

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Does your model incorporate the drag / 3d wing polar from open slats on the 109.... 

 

The slats accelerate the air over the wing preventing a stall. With propwash increasing the CLmax over the inboard section the slats help ensure the outboard section doesn't stall first, thus increasing the wing's overall CLmax.

 

If it wasn't for the lift increasing effect of prop wash designers would've installed full span slats, as we see on jets.

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They also increase drag...

There is no change in the curve to indicate when the slats are opening...

You do not answer the question...

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They also increase drag...

There is no change in the curve to indicate when the slats are opening...

You do not answer the question...

 

I doubt it will increase the drag in any other way than by increasing the CLmax, thus we're talking a Cdi increase, but that is 100% incorperated into Holtzauges calculations I'm sure. 

 

Also if you're expecting to see a change in the curve for when the slats are opening you will be disappointed as that doesn't happen considering the slats simply elongate the lift curve by increasing the critical AoA, they don't increase CL across the AoA range.

 

In short you're expecting something that just does not happen. 

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I’m not sure as you, sorry. You seem very persuaded by this nebulous C++ software... all I see are plots on a graph, and no evidence. Not even an explanation for a well-known drag phenomenon.

 

How do you find out the CLmax and induced drag while in a bank, of a wing with slats open? All I see is a smoooth curve with no explanation for the increased CLmax and drag of the wing with open slats... really I would expect a completely different 3D wing polar from the same wing with closed slats... by their nature and as you stated, that is what they do, and it should show on plots like these as critical AoA is reached...

Hmmm...

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Again you won't see any jump on the curve for when the slats start to open because they simply extend the lift curve toward a higher critical AoA and thus CLmax, they don't increase CLmax across the AoA range.

 

In short: Any extra drag added is from the extra lift generated, i.e. lift induced (CDi), and not because the slats themselves add any drag - at least not any amount that would have any effect on Holtzauge's graph.

 

Hence why automatic slats are so popular, they energize the boundary layer and increase the amount of lift that can be generated from any given wing area without any penalty in drag except for what comes with the extra lift.

 

PS: Remember that slats open and close depending on the AoA, thus they work both in turns and when the aircraft flies straight and slow, like when landing or taking off.

Edited by Panthera
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Which plane did you have in mind?

109F2, MC202, YAK 1B, La5/F

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