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Another look at turn times

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I think Panthera already gave a good explanation of how the slats work in a turn above but just let me add that the Handley-Page type sIats on the Me-109 were designed to open gradually beginning at a Cl of around 0.8 to become fully deployed at a Cl of circa 1.2 so there would be no jumps in the wing profile drag anyway. I can also confirm something else that Panthera pointed out earlier to Venturi:  The major source of drag in the turn is the induced drag and the C++ model takes into account the aspect ratio, the oswald factor and Mach effects with the Clmax as a function of Mach and the Oswald factor e a function of Cl so I’m assuming a reduction of e and as the stall is approached.

 

In addition, I just remembered I had some flight test data on a Finnish Me-109 G2 (MT-215) that stated turn performance at 1 Km altitude at 11 deg C ambient: Time for 360 degree turn at 360 Km/h, namely 22 s. For comparison, I get almost exactly the same turn time as the Finns at 360 Km/h, namely 22.7 s, at least if you take into account that I simulate for CINA condition (15 deg C ambient) and that taking this into account this would put the C++ estimate even closer to the measured figure.

 

To be honest I’m rather pleased at the level of correlation with those numbers and I think this is pretty much as close as you can get in terms of models and estimates when estimating the complex flow phenomena of an airplane close to stall.

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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. 

 

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

 

That is one long list but I notice the 202 is common so I will consider that one for the short list. Anyway, I have the Me-109 G6 modeled from before and seeing there are already discussions on-going regarding how the FN and G6 will mix I think I will put the La-5FN on the even shorter short list....... ;)

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That is one long list but I notice the 202 is common so I will consider that one for the short list. Anyway, I have the Me-109 G6 modeled from before and seeing there are already discussions on-going regarding how the FN and G6 will mix I think I will put the La-5FN on the even shorter short list....... ;)

 

Looking forward to the graphs Holtzauge :)

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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?

 

IMO its always a good idea to cross check [Edited]. For him, the 'good' tests are the ones that agree with his so called calculations, the ones that do not are dismissed by as 'outliers'. ;) Of course it also doesn't helps that sadly he doesn't understand neither Russian nor German and pretty much ignores important aspects in the test reports like different drag conditions of the planes in the test from a different piece of equipment, setting of the radiators etc. Such working method (bending reality instead of revising the calculation methods) has not only the side effect of going in circles for decades but also results in not getting very accurate. However I think these graphs still have certain educational value of how not to do these things. 

 

For example, here is what the NII VVS actually measured on the G-2 (with 20mm gondies and without) and the G-4 (which had less power than ours, same 1.3 ata as the G-2). The full paper is available at http://www.kurfurst.org/Tactical_trials/109G_Soviet/109G_NIIVVS_1944.pdf , but I did copy and mark out the page showing the turn times measured in left and right side turns real life tests to make it easier. 

 

The real world measurements of the Red Air Force on the Bf 109G-2, WNr 14153 captured at Stalingrad pretty firmly puts the G-2 (and the near identical G-4) turn time at 20 (20.5) secs at 1.3 ata.

 

So I would say the current Il-2 figures are a bit pessimistic at 22.2 secs (unless they are for the poorer turn) and the the AJ/HZ estimates figures of 18.9 or so are also inaccurate as well, the actual figures is right between these two outliers.

post-1271-0-63106300-1515058502_thumb.jpg

post-1271-0-11162500-1515058515_thumb.gif

Edited by Bearcat

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Both the Il-2 22.2s and Holtzauges 18.9s are sea level figures, while the VVS tested at 1000m. Sea level to 1000m typically adds a good second, which means the game is off by about 3 seconds, while Holtzauges calculation is pretty much a match.

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Interesting, if turn times of 20-20.5 sec were achieved at 1.3ata then I'd expect around 19-19.5 sec at 1.42ata, which puts the Bf-109G6 right alongside the late variant La-5FN in turn performance. 


Both the Il-2 22.2s and Holtzauges 18.9s are sea level figures, while the VVS tested at 1000m. Sea level to 1000m typically adds a good second, which means the game is off by about 3 seconds, while Holtzauges calculation is pretty much a match.

 

But it's still important to note that the Russians tested the aircraft at 1.3ata, not 1.42.  But AFAIK Holtzauges figures are also for 1.3ata.

Edited by Panthera

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Both the Il-2 22.2s and Holtzauges 18.9s are sea level figures, while the VVS tested at 1000m. Sea level to 1000m typically adds a good second, which means the game is off by about 3 seconds, while Holtzauges calculation is pretty much a match.

 

True, the altitudes needs to be reconciled. However as the DB 605A-1 actually puts out a bit more power at 1000m, i.e. 1360 PS vs 1310 PS at 0m (static), so I am note sure how you arrive at that 1 seconds. One second of difference when it comes to turning is quite a lot, actually.

 

In any case, the discrepancy between the stated figures in Il-2 data is strange, unless the Il-2 data is (i) valid for a different speed (ii) refers to turning in the worse direction.

 

Interesting, if turn times of 20-20.5 sec were achieved at 1.3ata then I'd expect around 19-19.5 sec at 1.42ata, which puts the Bf-109G6 right alongside the late variant La-5FN in turn performance. 

 

But it's still important to note that the Russians tested the aircraft at 1.3ata, not 1.42.  But AFAIK Holtzauges figures are also for 1.3ata.

 

The G-6 however is also a bit heavier and draggier, than the G-2, cc. 3100 kg vs 3037 kg at takeoff. On the balance of things, I'd say that the effects of increased drag and weight compared to the G-2 might cancel off the increased power (which is rather arbitrarily capped at 1 mins anyway). Cc. 19 secs is something I would expect from a late methanol powered variant, however, you still gain a pretty hefty +10% better power-loading which will be less noticeably on the most visible stats like top speed, but generally improve the acceleration and dynamism of the plane.

 

As for the La 5FN, its a very impressive performing plane, but only up to about 2000 m altitude, above that it runs out of power very quickly...

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True, the altitudes needs to be reconciled. However as the DB 605A-1 actually puts out a bit more power at 1000m, i.e. 1360 PS vs 1310 PS at 0m (static), so I am note sure how you arrive at that 1 seconds. One second of difference when it comes to turning is quite a lot, actually.

It's experience from numerous calculations and (game) tests. It's a simple necessity coming from the lower density air. Can't say how much exactly it is for the 109, but as a ballpark it works. You'd need about 20% more engine power to maintain turn time, and the DB got 4%.

 

In any case, the discrepancy between the stated figures in Il-2 data is strange, unless the Il-2 data is (i) valid for a different speed (ii) refers to turning in the worse direction.

Time to test in game, I guess.

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In game specifications, as copied from the Il-2 Gamepedia page:

 

109 E-7:

Maximum performance turn at Boosted power, 270 km/h IAS:
Sea level: 20.5 seconds
3000 m: 25.5 seconds

 

109 F-2

Maximum performance turn at sea level: 23.6 s, at 270 km/h IAS.
Maximum performance turn at 3000 m: 29.0 s, at 270 km/h IAS.

 

109 F-4

Maximum performance turn at sea level: 20.3 s, at 270 km/h IAS.
Maximum performance turn at 3000 m: 26.1 s, at 270 km/h IAS.

 

109 G-2

Maximum performance turn at sea level: 22.2 s, at 270 km/h IAS.
Maximum performance turn at 3000 m: 28.3 s, at 270 km/h IAS.

 

109 G-4

Maximum performance turn at sea level: 21.2 s, at 270 km/h IAS.
Maximum performance turn at 3000 m: 27.2 s, at 270 km/h IAS.

 

Only for the Emil do they mention which engine power setting is used, for the others I can only imagine it being a mix of 1.3 and 1.42 ATA, looking at the vastly different turn times for the different 109 models.

Especially the F-2 seems really off compared to the others.

 

 

 

 

 

 

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Only for the Emil do they mention which engine power setting is used, for the others I can only imagine it being a mix of 1.3 and 1.42 ATA, looking at the vastly different turn times for the different 109 models. Especially the F-2 seems really off compared to the others.

 

No, actually they do mention it in the notes.

 

Note 1: the data provided is for international standard atmosphere (ISA).

Note 2: flight performance ranges are given for possible aircraft mass ranges.

Note 3: maximum speeds, climb rates and turn times are given for standard aircraft mass.

Note 4: climb rates are given for Combat power, turn times are given for Emergency power.

Edited by II/JG17_SchwarzeDreizehn

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Regarding BOS 109s most of them underperform in sustained turn time a about 1-2 second according to VVS test. 109F2 and G2 seemed to be the most hurt. But also Spitfire looks very high

Edited by 303_Kwiatek

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No, actually they do mention it in the notes.

 

Note 1: the data provided is for international standard atmosphere (ISA).

Note 2: flight performance ranges are given for possible aircraft mass ranges.

Note 3: maximum speeds, climb rates and turn times are given for standard aircraft mass.

Note 4: climb rates are given for Combat power, turn times are given for Emergency power.

 

My bad. Still makes me wonder why the F2's turn time is so high.

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My guess is that the F-2 figures are based on captured F-2 test made by the Soviets, however this plane was a pretty poor shape... the supercharger was operating so badly that they had to extrapolate the figured for altitude.

 

I believe it is the same case for the E-7, the Soviet figures in this case also show some rather abnormal dropoff in performance near ground level... since both of these point to some supercharger issues, actually I suspect that Russian oil might have been put into the hydraulic drive of the 109’s supercharger was incompatible. French trials of captured 109Es also hint at the same (MAP strangely drops off before it should)

My guess is that the F-2 figures are based on captured F-2 test made by the Soviets, however this plane was a pretty poor shape... the supercharger was operating so badly that they had to extrapolate the figured for altitude.

 

I believe it is the same case for the E-7, the Soviet figures in this case also show some rather abnormal dropoff in performance near ground level... since both of these point to some supercharger issues, actually I suspect that Russian oil might have been put into the hydraulic drive of the 109’s supercharger was incompatible. French trials of captured 109Es also hint at the same (MAP strangely drops off before it should)

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Let's check the numbers regarding 109 F-2 vs.109 E-7:

 

109 F-2

Maximum performance turn at sea level: 23.6 s, at 270 km/h IAS

109 E-7:

Maximum performance turn at Boosted power, 270 km/h IAS:
Sea level: 20.5 seconds

 

Is there something wrong here? The engine of the 109 F2 is not that different. Let's check closer.

 

109 E-7 DB-601A Maximum power in Boosted mode at sea level: 1100 HP

Standard weight: 2614 kg

 

109 F-2 DB-601N Maximum power in Emergency mode at sea level: 1175 HP

Standard weight: 2789 kg

 

Wings surface

109 E-7 Wing surface  16.4 m^2

109 F-2 Wing surface: 16.1 m^2

 

Here the F-2 has 75 more HP. However the 109 E-7 at its standard weight is 175 kg lighter.

And the E-7 has a bigger wing surface.

 

wing loading is the total mass of an aircraft divided by the area of its wing. Larger wings move more air, so an aircraft with a large wing area relative to its mass (i.e., low wing loading) will have more lift available at any given speed

 

109 E-7     2614/16.4=159.39 kg/m^2

109 F-2     2789/16.1=173.22 kg/m^2

 

so the f2 has a bigger wing loading affecting negatively its sustained turn performance. So it is has the same wing area as the 109 f4 but with a weaker engine.

 

Power-to-weight ratio

 

109 E-7     1100/2614=0.4208

109 F-2     1175/2789=0.42129

So the F-2 ha slightly better trust/weight ratio however it cannot compensate for the wingloading in sutained turn scenario.

 

On the other hand this data is unreliable regarding the actual performance in game. According to the same data the turning speed Spitfire Mk.VB

Merlin 46 engine: Maximum performance turn at sea level: 25 s, at 270 km/h IAS.

Merlin 45 engine: Maximum performance turn at sea level: 22 s, at 270 km/h IAS.

 

I know this is not true from actual experience on the servers.

It cannot be true also because the wing loading is much lower and the power to weigh ratio is better.

Spitfire Mk.VB 2979/22.48=132,5 kg/m^2

 

Spitfire Mk.VB Power-to-weight ratio

1455/2979=0.488

 

Those basic mathematics ratios are speaking a lot regarding the perofmance of the aircrafts.

Edited by JG27_Kornezov

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All this is part of the initial analysis in the first post - even though looked at it from the other end.

 

In game, the E-7 is 20% more aerodynamically efficient then the Bf109F-2. A Yak-1S69 is 50% more aerodynamically efficient than the Bf109F-2. At least it was when I checked the numbers. There's no reason for the F-2 to turn as poorly as is does in game, slightly higher wingloading doesn't matter that much.

 

The aerodynamically most efficient Axis aircraft in game under sustained turning conditions is the Ju87D...

  • Upvote 1

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In game specifications, as copied from the Il-2 Gamepedia page:

 

109 E-7:

Maximum performance turn at Boosted power, 270 km/h IAS:

Sea level: 20.5 seconds

3000 m: 25.5 seconds

 

109 F-2

Maximum performance turn at sea level: 23.6 s, at 270 km/h IAS.

Maximum performance turn at 3000 m: 29.0 s, at 270 km/h IAS.

 

109 F-4

Maximum performance turn at sea level: 20.3 s, at 270 km/h IAS.

Maximum performance turn at 3000 m: 26.1 s, at 270 km/h IAS.

 

109 G-2

Maximum performance turn at sea level: 22.2 s, at 270 km/h IAS.

Maximum performance turn at 3000 m: 28.3 s, at 270 km/h IAS.

 

109 G-4

Maximum performance turn at sea level: 21.2 s, at 270 km/h IAS.

Maximum performance turn at 3000 m: 27.2 s, at 270 km/h IAS.

 

Only for the Emil do they mention which engine power setting is used, for the others I can only imagine it being a mix of 1.3 and 1.42 ATA, looking at the vastly different turn times for the different 109 models.

Especially the F-2 seems really off compared to the others.

 

 

IMO its always a good idea to cross check as good old HZ likes to pick between the real life tests. For him, the 'good' tests are the ones that agree with his so called calculations, the ones that do not are dismissed by as 'outliers'. ;) Of course it also doesn't helps that sadly he doesn't understand neither Russian nor German and pretty much ignores important aspects in the test reports like different drag conditions of the planes in the test from a different piece of equipment, setting of the radiators etc. Such working method (bending reality instead of revising the calculation methods) has not only the side effect of going in circles for decades but also results in not getting very accurate. However I think these graphs still have certain educational value of how not to do these things. 

 

For example, here is what the NII VVS actually measured on the G-2 (with 20mm gondies and without) and the G-4 (which had less power than ours, same 1.3 ata as the G-2). The full paper is available at http://www.kurfurst.org/Tactical_trials/109G_Soviet/109G_NIIVVS_1944.pdf , but I did copy and mark out the page showing the turn times measured in left and right side turns real life tests to make it easier. 

 

The real world measurements of the Red Air Force on the Bf 109G-2, WNr 14153 captured at Stalingrad pretty firmly puts the G-2 (and the near identical G-4) turn time at 20 (20.5) secs at 1.3 ata.

 

So I would say the current Il-2 figures are a bit pessimistic at 22.2 secs (unless they are for the poorer turn) and the the AJ/HZ estimates figures of 18.9 or so are also inaccurate as well, the actual figures is right between these two outliers.

 

Interesting, in this soviet report the 109-F2 did turn at 19.6 - 20.5 seconds at 1000m height. The one we have in the game with the same engine does 23.6 s at sea level according to game specifications...

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You are all forgetting that both the turn times listed in game, and the Russian turn time tests do not list weight or do not list a useful weight. 

 

In all of my testing with turning in game at sea level I adjust the fuel load of each plane to be equal to either liters available or fuel burn time. 

 

Testing turn times at percents or max aircraft weight is useless. The only valid test is for matching fuel load in terms of flight time. ie: both planes should have 50min of fuel at the tested power setting. 

 

Doing this resolves pretty much all issues in this regard with the game, except for the P-40. For example, the Spitfire at max boost and equal fuel weight can turn in 16 seconds, not 25 or whatever the game lists.. 

Edited by Fumes

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You are all forgetting that both the turn times listed in game, and the Russian turn time tests do not list weight or do not list a useful weight.

 

Note 3: maximum speeds, climb rates and turn times are given for standard aircraft mass

 

also in the notes (example F4)

Standart weight: 2890 kg

  • Upvote 2

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Let's check the numbers regarding 109 F-2 vs.109 E-7:

 

109 F-2

Maximum performance turn at sea level: 23.6 s, at 270 km/h IAS

109 E-7:

Maximum performance turn at Boosted power, 270 km/h IAS:

Sea level: 20.5 seconds

 

Is there something wrong here? The engine of the 109 F2 is not that different. Let's check closer.

 

109 E-7 DB-601A Maximum power in Boosted mode at sea level: 1100 HP

Standard weight: 2614 kg

 

109 F-2 DB-601N Maximum power in Emergency mode at sea level: 1175 HP

Standard weight: 2789 kg

 

Wings surface

109 E-7 Wing surface  16.4 m^2

109 F-2 Wing surface: 16.1 m^2

 

Here the F-2 has 75 more HP. However the 109 E-7 at its standard weight is 175 kg lighter.

And the E-7 has a bigger wing surface.

 

wing loading is the total mass of an aircraft divided by the area of its wing. Larger wings move more air, so an aircraft with a large wing area relative to its mass (i.e., low wing loading) will have more lift available at any given speed

 

109 E-7     2614/16.4=159.39 kg/m^2

109 F-2     2789/16.1=173.22 kg/m^2

 

so the f2 has a bigger wing loading affecting negatively its sustained turn performance. So it is has the same wing area as the 109 f4 but with a weaker engine.

 

Power-to-weight ratio

 

109 E-7     1100/2614=0.4208

109 F-2     1175/2789=0.42129

So the F-2 ha slightly better trust/weight ratio however it cannot compensate for the wingloading in sutained turn scenario.

 

On the other hand this data is unreliable regarding the actual performance in game. According to the same data the turning speed Spitfire Mk.VB

Merlin 46 engine: Maximum performance turn at sea level: 25 s, at 270 km/h IAS.

Merlin 45 engine: Maximum performance turn at sea level: 22 s, at 270 km/h IAS.

 

I know this is not true from actual experience on the servers.

It cannot be true also because the wing loading is much lower and the power to weigh ratio is better.

Spitfire Mk.VB 2979/22.48=132,5 kg/m^2

 

Spitfire Mk.VB Power-to-weight ratio

1455/2979=0.488

 

Those basic mathematics ration are speaking a lot regarding the perofmance of the aircrafts.

 

You are forgetting about drag. Also during turn you need to take in consideration the horizontal stabilizer area because it is loaded as well...

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Yea F2 expecially with 1.42 Ata power rating should be in pair with 109 F-4.  Also G-2/G-4 looks really too high in turning times.

F-2 with 1.42 Ata got above 1200 HP at sea level also it got aerodynamic improvement over 109 E whats mean less drag - expecially rounded wing tips cause less induced drag to overcome which was significant at high angle of attack situations ( steep turn).

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IMO its always a good idea to cross check as good old HZ likes to pick between the real life tests. For him, the 'good' tests are the ones that agree with his so called calculations, the ones that do not are dismissed by as 'outliers'. ;) Of course it also doesn't helps that sadly he doesn't understand neither Russian nor German and pretty much ignores important aspects in the test reports like different drag conditions of the planes in the test from a different piece of equipment, setting of the radiators etc. Such working method (bending reality instead of revising the calculation methods) has not only the side effect of going in circles for decades but also results in not getting very accurate. However I think these graphs still have certain educational value of how not to do these things. 

 

For example, here is what the NII VVS actually measured on the G-2 (with 20mm gondies and without) and the G-4 (which had less power than ours, same 1.3 ata as the G-2). The full paper is available at http://www.kurfurst.org/Tactical_trials/109G_Soviet/109G_NIIVVS_1944.pdf , but I did copy and mark out the page showing the turn times measured in left and right side turns real life tests to make it easier. 

 

The real world measurements of the Red Air Force on the Bf 109G-2, WNr 14153 captured at Stalingrad pretty firmly puts the G-2 (and the near identical G-4) turn time at 20 (20.5) secs at 1.3 ata.

 

So I would say the current Il-2 figures are a bit pessimistic at 22.2 secs (unless they are for the poorer turn) and the the AJ/HZ estimates figures of 18.9 or so are also inaccurate as well, the actual figures is right between these two outliers.

 

The thing is it’s exactly the other way around Kurfurst: You have a history of going for the outliers not me. You consistently go for the high end outliers for the Me-109 and low end outliers for the Spitfire. So if anyone has zero credibility it’s you. You consistently try to improve performance for German planes and try to pork Allied planes. This is a fact. All it takes is a search of your post history to conclude this. Those who are so inclined can do a similar search on my posts and you will find that I sometimes post to improve, and sometimes to degrade performance for both Allied and Axis planes. You on the other hand can always be found on the pork Spitfire/OP Me-109 side of the fence, so yeah, I agree, zero credibility only not in the way you envision. But seeing you are a lawyer and not an aeronautical engineer like me I guess attacking the messenger is all that is left to you.

 

Now concerning the numbers you posted, you are comparing apples with pears but I see JtD and Panthera have already explained the facts here and why the numbers are different: As JtD says my number was for SL and the delta in turn time between 0 and 1 Km is usually around 1 s. In addition, the Finnish combat turn was at a higher speed than that for the best turn time which is why both mine and the Finnish test gave a higher turn time than the Russian figure at 1 Km altitude.

 

At 1 Km altitude with 1.3 ata I get the best turn time for the Me-109G2 at 20.2 s at 270 Km/h IAS so actually a rather good match with the Russian figure of 20 s. So thanks for posting the chart Kurfurst! It's good to get this type of data to validate my C++ model! :good:

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Your simulation model does seem to have produced quite accurate figures so far Holtzauge, and I have to say I'm rather impressed :)  Looking forward to seeing a compilation for the rest of the aircraft :)

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Thanks Panthera! As JtD’s table in the OP shows there are some strange inconsistencies concerning the aerodynamic efficiencies which are hard to explain and like others have pointed out above, the Me-109F2 sticks out as well not to mention the Spitfire which is currently off the charts (which OTOH is most likely simply a typo IMHO since in-game it’s more like the 16 s at SL as it should be AFAIK?). Another thing that is strange is the new turn times given for the Fw-190 with the new FM: Before the tuning the developers notes stated 34.3 s at 3 km altitude and now it has been reduced to 28 so the Fw-190 is now only off at low altitude. I don’t understand how that can be? Must be something strange with how this is tuned in-game since climb and turn performance is usually quite correlated and AFAIK the Fw-190 in-game climb rates at 0 and 3 Km are not off in the same way…..

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So here are the stationary turn rate (STR) C++ simulations for the La-5FN and Me-109 G6 at 0, 3 and 6 Km altitude with different power settings.

 

The plotted curves speak for themselves but it is interesting to note that at low altitude, up to about 2 Km then the FN dominates with WEP. However, with mil/Steig&K L. the planes are almost identical in STR performance.

 

At 2 Km and above the Ash-82 runs out of steam and the G6 with it’s better aspect ratio begins to display at bit higher STR but it is marginal, especially when the time at 1.4 ata is up and the G6 has to make do with 1.3 ata.

 

Other than that the general trend is that the FN has a better STR at higher speeds but that is expected since it is faster.

 

post-23617-0-06782800-1515431215_thumb.gif

  • Upvote 5

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All in all it's pretty close, and the better position will be very important for the eventual outcome. Thanks for crunching the numbers.

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Yes, as soon as the Ash-82 gets out of its comfort zone below 2 Km it seems there is little to choose between the two in terms of stationary turn rate. Not much left in the toolbox for the G6 at lower altitudes then: No speed, climb or turn rate advantage to work with. Well there is always the Mk108 of course....... ;) 

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So here are the stationary turn rate (STR) C++ simulations for the La-5FN and Me-109 G6 at 0, 3 and 6 Km altitude with different power settings.

 

The plotted curves speak for themselves but it is interesting to note that at low altitude, up to about 2 Km then the FN dominates with WEP. However, with mil/Steig&K L. the planes are almost identical in STR performance.

 

At 2 Km and above the Ash-82 runs out of steam and the G6 with it’s better aspect ratio begins to display at bit higher STR but it is marginal, especially when the time at 1.4 ata is up and the G6 has to make do with 1.3 ata.

 

Other than that the general trend is that the FN has a better STR at higher speeds but that is expected since it is faster.

 

 

Great chart once again Holtzauge :)

 

What's the HP ratings used for the Ash-82 at mil & WEP ? :)

 

PS: G2 or G4 with 1.42ata would be interesting to see as well, should be very close to the La-5FN according to my own calculations.

Edited by Panthera

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An extrapolation from your other chart:

qZlT9hY.gif

Edited by Panthera

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Btw, I wonder how trustworthy Russian speed readings were as the 640 km/h top speed @ SL for the La-7 seems extremely dubious at best.

 

Did you do any calculations on that subject Holtzauge?

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Great chart once again Holtzauge :)

 

What's the HP ratings used for the Ash-82 at mil & WEP ? :)

 

PS: G2 or G4 with 1.42ata would be interesting to see as well, should be very close to the La-5FN according to my own calculations.

 

I used the attached figures from TSAGI for power for the Ash-82 FN (Was the best I had and if you or someone has more input it would be appreciated).

 

I attach a revised STR figure below with the Me-109G2 included. Your estimate in the post above looks spot on! :good:

 

At first I thought it looked strange that the G2 did worse at high speed and then I remembered that the G2 is for 1.3 ata, not 1.42 ata like the G6 curve.

 

post-23617-0-18312400-1515443371_thumb.jpg

post-23617-0-09467600-1515443382_thumb.gif

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Btw, I wonder how trustworthy Russian speed readings were as the 640 km/h top speed @ SL for the La-7 seems extremely dubious at best.

 

Did you do any calculations on that subject Holtzauge?

 

No, I don't have the La-7 modelled but that sounds mighty fast.....

 

OTOH there does in many cases seem to be a large spread in stated Russian performance figures and I suspect this has to do with the many different factories putting out different models with varying standards. Don't know if that is applicable to the La-7 thought, but it certainly seems to be the case with the earlier planes.

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Btw, I wonder how trustworthy Russian speed readings were as the 640 km/h top speed @ SL for the La-7 seems extremely dubious at best.

 

Did you do any calculations on that subject Holtzauge?

There is one Tsagi graph showing for the La-7 a top speed at the deck of 583 in continuous and 614 in Boosted mode

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There is one Tsagi graph showing for the La-7 a top speed at the deck of 583 in continuous and 614 in Boosted mode

 

So did the La-7 have more power (higher boost?) or was it just a question of better aerodynamics? I get around 580 Km/h at SL for the La-5FN in boosted mode so even 614 km/h sounds respectable.

Edited by Holtzauge

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I used the attached figures from TSAGI for power for the Ash-82 FN (Was the best I had and if you or someone has more input it would be appreciated).

 

I attach a revised STR figure below with the Me-109G2 included. Your estimate in the post above looks spot on! :good:

 

At first I thought it looked strange that the G2 did worse at high speed and then I remembered that the G2 is for 1.3 ata, not 1.42 ata like the G6 curve.

 

Great, was using the same graph myself :) (1650 hp)

 

The G2/G4 running at 1.42ata I calculate as being very similar to the La-5FN in STR, but with the G2/G4 having the advantage in ITR. 

No, I don't have the La-7 modelled but that sounds mighty fast.....

 

OTOH there does in many cases seem to be a large spread in stated Russian performance figures and I suspect this has to do with the many different factories putting out different models with varying standards. Don't know if that is applicable to the La-7 thought, but it certainly seems to be the case with the earlier planes.

 

Maybe, not sure. My eyes just kind of widened when I saw 640 km/h at SL for just 1850 hp. 

 

There is one Tsagi graph showing for the La-7 a top speed at the deck of 583 in continuous and 614 in Boosted mode

 

Ah ok, see now that makes a lot more sense :)

Edited by Panthera

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The P-51 is a much bigger aircraft than a La-7, but of excellent aerodynamic quality for a WW2 aircraft. It needed (at least) 2000hp to obtain about 640km/h at sea level. The Ash-82FN produced 1850hp. Considering the smaller size of the La-7, 640km/h at sea level would be possible at this lower power, but it would be an individual aircraft with excellent finishing, considering that the overall aerodynamic layout of the Lavochkin was not as good as that of the P-51 (starts with laminar flow wings, and goes on). Certainly 614km/h can be considered plausible, aerodynamically it was considerably improved compared to a La-5.

 

Attached an Ash82 power chart from the manual. The curves show Ash-82F and Ash-82FN.

post-627-0-01333600-1515445303_thumb.jpg

Edited by JtD

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So did the La-7 have more power (higher boost?) or was it just a question of better aerodynamics? I get around 580 Km/h at SL for the La-5FN in boosted mode so even 614 km/h sounds respectable.

 

The engine was the same afaik, there were aerodynamics improvements, like deleting the upper cowling intake, and redesigning the oil radiator, placing it behind the wings similar to the late Yaks.

 

la-5-52-x.png

 

1_2_b1.jpg

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640 km/h at SL for a 1850 hp radial sounds fantastical though, esp. without a laminar flow wing. I wonder if the figure illustrated expected performance with the La-9's laminar wing?

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Some talk of the testing on La-5 which improved aero, which was used on La-7 (and some later model La-5FN)

 

"In February 1943, on the scales of full-scale wind tunnel T-101 Central hydrodynamic Institute in Zhukovsky established production sample La-5 No. 37210514. electric power, drives the rotation of a pair of fan pipe was such that the tests were conducted only at night - otherwise it would have to be disconnected from the power supply the whole city.

Studies have shown that if the seal plane inside and outside the cabin from all sorts of air to flow and close the flaps of the dome landing gear wheels, it is possible, reducing aerodynamic drag and increase speed of about 35 km / h. The greatest increase in speed (24 km / h) afforded sealing fighter."

 

"In March - April 1943 goda La 5 with sealed engine hood and tunnel oil cooler with an air inlet, transferred under the fuselage (for the fifth frame), was examined in the full-scale wind tunnel TSAGI T-104. The results were encouraging: only this event gave the increase in speed of 25-30 km / h, and a number of smaller improvements add another 10-15 km / h. In addition, the improved motor temperature mode, since the air flow rate through the oil cooler has increased by almost a quarter.

So was another step towards the emergence of La-7."

 
excuse poor google translate
 
Cheers, Dakpilot

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The engine was the same afaik, there were aerodynamics improvements, like deleting the upper cowling intake, and redesigning the oil radiator, placing it behind the wings similar to the late Yaks.

 

la-5-52-x.png

 

1_2_b1.jpg

 

The La-7 looks really nice: One thing that is interesting to note is the boundary layer separation on the oil cooler intake and the rounded intake lips: most Me-109’s and the Spitfire (and early Russian planes) did not have a boundary layer separation of the air going into the cooler (giving problems with separation in the diffusor) and the early Russian fighters also had sharp intake lips which paradoxically actually gives higher drag in most conditions since you get boundary layer separation at the lips if they are sharp. The P-51 was AFAIK first with these modern attributes which today are pretty much taken for granted. In addition, looks like a revised wing root fillet design, cleaned up cowling and air exit, new location for ram air intakes in the wing and smaller gun ports.

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The P-51 is a much bigger aircraft than a La-7, but of excellent aerodynamic quality for a WW2 aircraft. It needed (at least) 2000hp to obtain about 640km/h at sea level. The Ash-82FN produced 1850hp. Considering the smaller size of the La-7, 640km/h at sea level would be possible at this lower power, but it would be an individual aircraft with excellent finishing, considering that the overall aerodynamic layout of the Lavochkin was not as good as that of the P-51 (starts with laminar flow wings, and goes on). Certainly 614km/h can be considered plausible, aerodynamically it was considerably improved compared to a La-5.

 

Attached an Ash82 power chart from the manual. The curves show Ash-82F and Ash-82FN.

 

Thanks for the chart JtD. Looks like the Ash-82FN engine model I have (based on the old chart I posted above earlier on) is OK then but what about the rpm difference on the FN? The power due to increased boost at low altitude is one thing but since WEP is 2500 rpm and mil 2400 that should improve critical altitude somewhat. Nice to have data for the Ash-82F as well!

Some talk of the testing on La-5 which improved aero, which was used on La-7 (and some later model La-5FN)

 

"In February 1943, on the scales of full-scale wind tunnel T-101 Central hydrodynamic Institute in Zhukovsky established production sample La-5 No. 37210514. electric power, drives the rotation of a pair of fan pipe was such that the tests were conducted only at night - otherwise it would have to be disconnected from the power supply the whole city.

Studies have shown that if the seal plane inside and outside the cabin from all sorts of air to flow and close the flaps of the dome landing gear wheels, it is possible, reducing aerodynamic drag and increase speed of about 35 km / h. The greatest increase in speed (24 km / h) afforded sealing fighter."

 

"In March - April 1943 goda La 5 with sealed engine hood and tunnel oil cooler with an air inlet, transferred under the fuselage (for the fifth frame), was examined in the full-scale wind tunnel TSAGI T-104. The results were encouraging: only this event gave the increase in speed of 25-30 km / h, and a number of smaller improvements add another 10-15 km / h. In addition, the improved motor temperature mode, since the air flow rate through the oil cooler has increased by almost a quarter.

So was another step towards the emergence of La-7."

 

excuse poor google translate

 

Cheers, Dakpilot

 

Interesting info and that puts the improvement in the range of 35-45 Km/h but to improve from 580 to 640 Km/h SL speed would either take about (640/580)**3=1.34 or 34% more power, i.e. from 1850 to a whopping 2586 hp on the La-5FN or one would need to reduce drag on the La-5FN by about 25% to circa 1/1.134 in the La-7. Maybe the latter is as JtD said doable for a vaxed pristine supersealed variant but for a production fighter it sounds like a tall order.

Edited by Holtzauge

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