Could the Bf 109 E really out-turn the Spitfire Mk I?

[drgondog]

Reading that report it seems as though the 190 pilots had little to no situational awareness even while under attack so in this situation the boom and zoom attack was effective, saying that I can't imagine this would have worked in the early war years but by the second half of 1944 they were desperate for pilots and when they did get them there was very little fuel for training so knocking down 5 190's, a plane that caused so much grief when it first came out with such ease could be classed as an outlier?.

I believe the Fw 190s were of the Sturm group of converted ZG26 Me 410 pilots. ZG 26 was hammered on June 20, July 7 when it became clear there was no safe airspace for t/e fighters attacking bomber forces, even when escorted.

 

[Holtzauge]

Both WarThunder and IL-2 1946 used polares lookup to build FMs, while the WarThunder way is slightly more advanced featuring component-level polares and the Mach effect. A better way of achiving FM is by actively implementing CFD-like method (extremely simplified) to simulate real-time airflow interaction, like the X-plane and newest microsoft flight simulator.

If you have an accurate Cl/Cd polar this will actually give you very good modeling close to stall since this involves significant parts of the wing with detached flow and vortex separations, and which is something CFD LES/DES modeling needs weeks or months to solve for just ONE angle of attack.

There is a reason that NASA still keeps the National Full-Scale Aerodynamics Complex (NFAC) and absorbs the huge cost of maintaining such a facility. However, this does not stop some flight simulator developers from claiming they used CFD "extensively", which I hope is a statement from their marketing department, because if this is what their engineers are saying I would be deeply troubled.

The original 1946 FMs were made very badly, and commonly mixed with different people with different opinons during different upgrades, just as its DMs for different planes are programmed so differently that you are basically flying an apple to fight oranges.

Yes, the first releases of Il-2 had really weird FM's. And even though it has gotten better over time, there are still some strange modeling choices in that sim, an example of which was posted here.

About 109's FM in WarThunder, a very interesting fact is that they used completely different CLmax values for 109 families. Starting from early BF-109A/B/E, CLmax been only 1.24-1.25. Starting BF-109F its 1.4, and G-6 onward increased to 1.43, with G-14 been the highest with a CLmax of 1.46. In reality we had RAE tests on BF-109E that featuring a CLmax ~1.37 (rounded up to 1.4) power-off clean and ~1.9 with flaps extended. Considering its airfoil NACA2R1 had similar CLmax level as NACA-00 series, 1.37 seems to be a reasonable figure, but I doubt on late model 109s to have an increased CLmax due to their much dirtier in aerodynamic shapes.

The Bf 109 was also tested in the full-scale Chalais-Meudon facility after the Germans captured that, and they did a number of runs, the average of which was around 1.41 IIRC.

So this tabs pretty well with RAE's 1.4 figure for the Bf 109 E. Interesting that you say it was actually 1.37. Can you provide a reference for that?

Since the RAE usually defines Clmax with two significant digits, e.g. 1.36 for the Spitfire, my interpretation that they wrote just 1.4 for the Bf 109 E was that it was 1.40, and that per mathematical convention the zero was dropped. But if you have evidence that it was actually 1.37, I would be very interested to see where this was written down.

 

[Steamed_Banana]

I assume that the "Il-2 Sturmovik" mentioned earlier was the so-called "Great Battles" edition, not the older (2001) original.

Just for info, the old game (nowadays called Il-2 Sturmovik 1946) has a cool utility called IL2 Compare. Among other parameters, it contains turn times and speeds with/without flaps. The utility was developed for several game versions, including modded versions such as HSFX, Ultrapack and BAT. There is even an Android app.

Some graphs.
IL2 Compare for 4.13.4 (stock game version).
Bf 109 K-4
View attachment 886686
View attachment 886687

IL2 Compare for Ultrapack 3RC4.
Bf 109 E-4 (blue) vs Spitfire MkI (red)
View attachment 886689
Larger curves - no flaps.
I think that fuel is 100% by default. Some variants of IL2 Compare used to include additional sets of data for other fuel conditions.
This pack contains IL2 Compare variants for several stock game versions (4.09, 4.11, 4.10.1, 4.13.4) and for modded versions (HSFX, BAT, UP):

IL2 Compare

MediaFire is a simple to use free service that lets you put all your photos, documents, music, and video in a single place so you can access them anywhere and share them everywhere.

www.mediafire.com

Weirdly, I think IL2 1946 has the better flight models, especially for European Theater planes and in particular those that fought on the Russian front, though still with a lot of flaws. The newer version is much more precise but seems to have thumb on the scale a good bit more, i.e. favoring certain types over others. The older version improved somewhat over time as a result of a lot of people complaining and providing data like from WW2 flight tests etc. but they are much more resistant to that with the newer version.

I'd been told about a very weird incident in which Ubisoft apparently got sued by American aerospace company for use of their IP in the form of flight models, though maybe that was BS I can't find it on google right now.

 

[bada]

Weirdly, I think IL2 1946 has the better flight models, especially for European Theater planes and in particular those that fought on the Russian front, though still with a lot of flaws. The newer version is much more precise but seems to have thumb on the scale a good bit more, i.e. favoring certain types over others. The older version improved somewhat over time as a result of a lot of people complaining and providing data like from WW2 flight tests etc. but they are much more resistant to that with the newer version.

I'd been told about a very weird incident in which Ubisoft apparently got sued by American aerospace company for use of their IP in the form of flight models, though maybe that was BS I can't find it on google right now.

Ubisoft got sued by Northtrop-Gru$$sman not because of flight models, but because they used the name Grumann and Hellcat (or wildcat, don't rememeber exactly) on the jacket of the game (il-2 Pacific Fighters) without autorisation( what means paying NG ) . Both names being Trademarked.

Agree with you that the old il-2/46 FM's feel more accurate(even if some are totally porked) than the ones in BoX, but my favorites stays the ones in CoD, even if they need some polishing. The "feel" of energy loss or gain is more perceptible in Cod than in Box, the plane handling totaly differently in both situations.

 

[Steamed_Banana]

Can you break down what those names / acronyms mean? CoD, BoX etc.?

I think the FMs were off in 1946 for the Pacific Theater planes especially, but the types were on the Russian front were better modeled (after a lot of tinkering and iterations etc.)

 

[Steamed_Banana]

I tried googling this again and AI gave me this - one never knows is Google AI is making things up or what though

"Northrop Grumman threatened legal action against Ubisoft over the unauthorized use of trademarked military aircraft names in the 2004 flight simulator Pacific Fighters, a standalone expansion of IL-2 Sturmovik. While often referred to in gaming communities as a full-blown lawsuit, the dispute was primarily a high-stakes trademark conflict that resulted in Ubisoft altering its packaging, promotional material, and in-game content to avoid formal litigation. [1, 2]

Key Details of the Dispute

• • The Core Conflict: Ubisoft used historical aircraft names and likenesses—such as the Grumman F6F Hellcat, F4F Wildcat, and TBF Avenger—without licensing them from Northrop Grumman, which had acquired the original Grumman Aerospace Corporation in 1994. [1, 2]
  • Ubisoft's Miscalculation: The publishers initially assumed that because the original Grumman company no longer existed as an independent entity, the historical designations of World War II aircraft were free to use. Northrop Grumman's legal team fiercely contested this, asserting that they held the active intellectual property rights to the legacy Grumman brand and designs. [1]
  • The Financial Impact: Rather than entering a prolonged and costly courtroom battle against a massive defense contractor, Ubisoft opted to scrub or alter trademarked references on its promotional disc cases, marketing materials, and retail packaging, which cost the publisher a significant amount of money. [1]

The Legacy Impact on Flight Simulators
This incident became a watershed moment for the flight simulation industry, establishing a legal precedent that permanently changed how military video games are developed.

• • Mandatory Licensing: Major defense contractors like Lockheed Martin, Boeing, and Northrop Grumman began aggressively enforcing intellectual property rights on video games. Software developers were forced to pay substantial licensing fees to legally use aircraft names, logos, and cockpits. [1, 2]
  • The "Generic Name" Workaround: To avoid paying these licensing fees, many subsequent combat flight simulators began omitting official manufacturer names, using only military designations (e.g., calling an aircraft simply the "F6F-3" or "Hellcat" rather than the "Grumman F6F Hellcat")."

 

[Irregualr23]

If you have an accurate Cl/Cd polar this will actually give you very good modeling close to stall since this involves significant parts of the wing with detached flow and vortex separations, and which is something CFD LES/DES modeling needs weeks or months to solve for just ONE angle of attack.

There is a reason that NASA still keeps the National Full-Scale Aerodynamics Complex (NFAC) and absorbs the huge cost of maintaining such a facility. However, this does not stop some flight simulator developers from claiming they used CFD "extensively", which I hope is a statement from their marketing department, because if this is what their engineers are saying I would be deeply troubled.



Yes, the first releases of Il-2 had really weird FM's. And even though it has gotten better over time, there are still some strange modeling choices in that sim, an example of which was posted here.



The Bf 109 was also tested in the full-scale Chalais-Meudon facility after the Germans captured that, and they did a number of runs, the average of which was around 1.41 IIRC.

So this tabs pretty well with RAE's 1.4 figure for the Bf 109 E. Interesting that you say it was actually 1.37. Can you provide a reference for that?

Since the RAE usually defines Clmax with two significant digits, e.g. 1.36 for the Spitfire, my interpretation that they wrote just 1.4 for the Bf 109 E was that it was 1.40, and that per mathematical convention the zero was dropped. But if you have evidence that it was actually 1.37, I would be very interested to see where this was written down.

X-plane used blade-element method, which is basically an FM-lookup mixed with sort of panel method, and the behaviour is extensively tunned during trail and error. As the conventional polares look-up method not ideal to simulate propeller stream effect, ut should be a better and a good enough guide to simulate FM especially stability under dynamic air, but far from the level of high fidality CFD simulation. Microsoft used another way but I doubt whether they actually used it for FM or just for visual effect.

Speaking of that RAE handling test of Me-109, the CLmax figures in the table were rounded to 1 decimal number so that showed 1.4. With information given in the table as been recorded, W=5580lbs, S = 174sqft, Vstall = 95.5mph CIAS, with formula C_L = (2 * W) / (rho * V**2 * S) gives CLmax = 1.375 instead of 1.4. For flaps lowered it is 1.91.

To some reason the RAE decieded to keep 3-decimals for slats openning CL but all other CL been rounded to 1-decimal. They may want to remain some ambiguity as the test was only ran once with only 60ft long suspended static source was used, and they may consider the captured airplane to have a degraded condition to some extent. Whatever their reason, this specific test gives CLmax 1.375 for this 109E in clean condition.

 

[Irregualr23]

Back to the topic, I think one interesting point to be noted is that bf-109 seemed to have a fairly large slotted flap and a slotted aileron used as high-lift devices. Which made it to have a full-span flaperon, and it is quite advanced considering its era. I believe that most people had over-estimated the effect of slats on 109s, outer wing slats mostly used to provide better aileron control near stall point while bouns on CLmax can be some what minor, its high-lift devices design actually boosted more CLmax around 0.5 for the 109 and almost made it to the level of a naval airplane.

A good point for deploying slotted flaps in combat is that you would only need to lower it by a few degrees to obtain much of the lift boosted. The manual flap wheel that is critised on the 109 may not be a problem, as the pilot would only roll it for a few circle with his left hand to obtain the optimal flap setting for combat, achiving CLmax level around 1.5 - 1.7 in an instantenous turn to match with the Spitfire. I think this may explain some observation in the dogfight.

In the case of F2A, lowering the slotted flap by 4 degree would already boost CLmax from 1.51 to 1.64. In the case of 109, some 5 degree of flap can be easily operated with hand crank and done in a few seconds.

As in comparison, the Spitfire equipped with a pneumatic split flap, which is doubtful to be used in dogfight as the flap is simple with no intermediate position and operated by compressed-air with probably limited pressure avaliable. A Seafire with flap down was tested to have CLmax around 1.75 which is lower than BF-109's 1.91.

 

[Steamed_Banana]

Problem is, if you are using flaps for more than a few seconds, and turning with an opponent which is not using flaps, you are going to quickly fall behind in speed, and get to your stall speed more quickly.

 

[Holtzauge]

X-plane used blade-element method, which is basically an FM-lookup mixed with sort of panel method, and the behaviour is extensively tunned during trail and error. As the conventional polares look-up method not ideal to simulate propeller stream effect, ut should be a better and a good enough guide to simulate FM especially stability under dynamic air, but far from the level of high fidality CFD simulation. Microsoft used another way but I doubt whether they actually used it for FM or just for visual effect.

View attachment 888145

When looking at the final flight sim product, I think you have to consider errors introduced on two levels:

The first is in the actual assumed characteristics, as in what top speed, what climb rate and what turn rate are you targeting in your FM. The second is how do you map this into your in-game FM, and how close can you get to the values you are targeting. And X-plane may very well be doing this second step better than Il-2. I have not looked into this.

But that was not the point I was making: My point was that if you have erroneous assumptions in step one going in to your modeling, then this will aggravate the problem even more. For example, if you select high end outliers for one plane, and low end outliers for another, then the end results may show inconsistencies across the board.

Speaking of that RAE handling test of Me-109, the CLmax figures in the table were rounded to 1 decimal number so that showed 1.4. With information given in the table as been recorded, W=5580lbs, S = 174sqft, Vstall = 95.5mph CIAS, with formula C_L = (2 * W) / (rho * V**2 * S) gives CLmax = 1.375 instead of 1.4. For flaps lowered it is 1.91.
View attachment 888146
To some reason the RAE decieded to keep 3-decimals for slats openning CL but all other CL been rounded to 1-decimal. They may want to remain some ambiguity as the test was only ran once with only 60ft long suspended static source was used, and they may consider the captured airplane to have a degraded condition to some extent. Whatever their reason, this specific test gives CLmax 1.375 for this 109E in clean condition.

OK, so the 1.375 figure is your own calculation, and not RAE's number. In addition, you have assumed that the 1.4 figure in the report was RAE rounding this up. I don't think this is very plausible, since Table 4 from which you take these numbers from states that the speed numbers in it are INDICATED speeds (both for the pilot's ASI and the trailing pitot). Consequently, those numbers do not contain calibration and instrument errors. So a more plausible explanation is that the 1.4 figure stems from RAE's calculation of Cl when the indicated ASI as per the table has been calibrated and instrument errors included.

Further evidence of this can be found in figure 17 in the same report, where the power on Clmax for the Spitfire and Bf 109 is listed at different g-loads. For the Spitfire, this is 1.87 at 1 g's and 1.38 at 6 g's.

Now at 6 g's the slipstream effect is small, and which explains that the Clmax of 1.38 is close to the power off Clmax which is 1.36 on the Spitfire.

Then if we read off the Clmax for the Bf 109 at 6 g's in the same report, this is 1.44, and which is then more likely to be 1.42 in power off conditions.

Finally, remember that the Germans themselves measured a Clmax of 1.41 in average in the Chalais Meudon wind tunnel.

So in summary, both German and British measurements seems to agree on a Clmax of slightly above 1.4.

 

[Holtzauge]

Back to the topic, I think one interesting point to be noted is that bf-109 seemed to have a fairly large slotted flap and a slotted aileron used as high-lift devices. Which made it to have a full-span flaperon, and it is quite advanced considering its era. I believe that most people had over-estimated the effect of slats on 109s, outer wing slats mostly used to provide better aileron control near stall point while bouns on CLmax can be some what minor, its high-lift devices design actually boosted more CLmax around 0.5 for the 109 and almost made it to the level of a naval airplane.

A good point for deploying slotted flaps in combat is that you would only need to lower it by a few degrees to obtain much of the lift boosted. The manual flap wheel that is critised on the 109 may not be a problem, as the pilot would only roll it for a few circle with his left hand to obtain the optimal flap setting for combat, achiving CLmax level around 1.5 - 1.7 in an instantenous turn to match with the Spitfire. I think this may explain some observation in the dogfight.

In the case of F2A, lowering the slotted flap by 4 degree would already boost CLmax from 1.51 to 1.64. In the case of 109, some 5 degree of flap can be easily operated with hand crank and done in a few seconds.

View attachment 888148


As in comparison, the Spitfire equipped with a pneumatic split flap, which is doubtful to be used in dogfight as the flap is simple with no intermediate position and operated by compressed-air with probably limited pressure avaliable. A Seafire with flap down was tested to have CLmax around 1.75 which is lower than BF-109's 1.91.
View attachment 888147

Absolutely. And if you watched my video in the OP, you will see that this is basically what I'm saying in it: Winding out the Bf 109's trailing edge flaps will improve turn performance under under certain conditions, and that the cockpit arrangement with the trim and flap control wheels placed together in the Bf 109 facilitated this, whereas on the Spitfire, with its two position system, this was not as feasible.

 

[bada]

Can you break down what those names / acronyms mean? CoD, BoX etc.?

I think the FMs were off in 1946 for the Pacific Theater planes especially, but the types were on the Russian front were better modeled (after a lot of tinkering and iterations etc.)

Il-2/46>Full version of il-2 with addons/pacific fighters included. release in 2006
il-2 CoD: Cliffs of Dover, release in 2011, fully reworked physics/dammage/terrain engine
il-2/ Box: Battle of X (put your battle name here) release in 2014. Based on Rise of Flight (WW1 simulator) engine.

 

[Irregualr23]

When looking at the final flight sim product, I think you have to consider errors introduced on two levels:

The first is in the actual assumed characteristics, as in what top speed, what climb rate and what turn rate are you targeting in your FM. The second is how do you map this into your in-game FM, and how close can you get to the values you are targeting. And X-plane may very well be doing this second step better than Il-2. I have not looked into this.

But that was not the point I was making: My point was that if you have erroneous assumptions in step one going in to your modeling, then this will aggravate the problem even more. For example, if you select high end outliers for one plane, and low end outliers for another, then the end results may show inconsistencies across the board.



OK, so the 1.375 figure is your own calculation, and not RAE's number. In addition, you have assumed that the 1.4 figure in the report was RAE rounding this up. I don't think this is very plausible, since Table 4 from which you take these numbers from states that the speed numbers in it are INDICATED speeds (both for the pilot's ASI and the trailing pitot). Consequently, those numbers do not contain calibration and instrument errors. So a more plausible explanation is that the 1.4 figure stems from RAE's calculation of Cl when the indicated ASI as per the table has been calibrated and instrument errors included.

Further evidence of this can be found in figure 17 in the same report, where the power on Clmax for the Spitfire and Bf 109 is listed at different g-loads. For the Spitfire, this is 1.87 at 1 g's and 1.38 at 6 g's.

Now at 6 g's the slipstream effect is small, and which explains that the Clmax of 1.38 is close to the power off Clmax which is 1.36 on the Spitfire.

Then if we read off the Clmax for the Bf 109 at 6 g's in the same report, this is 1.44, and which is then more likely to be 1.42 in power off conditions.

Finally, remember that the Germans themselves measured a Clmax of 1.41 in average in the Chalais Meudon wind tunnel.

So in summary, both German and British measurements seems to agree on a Clmax of slightly above 1.4.

The RAE stalling test in Table 4 provided already corrected CIAS through trailling static source, the reading aquried from swievlling pitot and trailling static source, this value is used to correct PE for ASI, and was not subjected to PE. Which is the one you quoted earlier as the "only reliable source". The "assumed values" of CLmax was never explained in the report, and how these assumption were made, there should be one more stall test to be done with power-on but appearently not included. Morgan may believed that the German 109 should be in a better condition and thus assume the number best to be rounded from 1.375 to 1.4.

Again I don't know what is your insistance on 109's CLmax to must be exactly over 1.4, while other plane should perform badly with only 1.35. Technically, these were not solid evidence that a BF-109 should MUST have a CLmax advantage over most WW2 airplanes in clean-condition, as its airfoil profile was not optimal in terms of CLmax (NACA 2R1 superior to CYH but was overcasted by NACA 4 digits and more by 5 digits) at the time of WW2. Its H-tail area is small (14% of total wing area), which won't be expected to gain any CL from its tail-arrangement. Moreover, its slat doesn't help much on improving CLmax as quoted in the MTT report.

The conditon for the BF-109 V-24 tunnel test still mostly remained unclear, how closed the V-24 related to a production BF-109? is it tested with propeller or not? if it is, is it fully idling or at neutral thrust? what airpspeed was used? What reference area was used in calculating CLmax (Chalais Meudon did a mistake in calculating FW-190's CL polares, and was later to be corrected, whether the same happened to this 109, and also French had a tendency to use wing-area that excludes fuselage area, even NACA did similar error in calculating the CL for F4U-4). It is better if the report can be displayed with more details.

I'm not denying BF-109's ability to achieve CLmax over 1.4, actually I'd believe that most WW2 fighter planes should perform at these region. I would say since NACA 2R1-12 airfoil performs similarly with NACA 0012, and with similar in-line engine design and wing planform, P-39 could be made to be closely comparable with the BF-109, it was tested by NACA to have a CLmax around 1.35 in a stalling test, but is able to perform over 1.4 under certain Mach and Re numbers.

 

[Simon Thomas]

Info on the 2R1 12% thick aerofoil is here. Bf109 Airfoil

 

[Holtzauge]

The RAE stalling test in Table 4 provided already corrected CIAS through trailling static source, the reading aquried from swievlling pitot and trailling static source, this value is used to correct PE for ASI, and was not subjected to PE. Which is the one you quoted earlier as the "only reliable source". The "assumed values" of CLmax was never explained in the report, and how these assumption were made, there should be one more stall test to be done with power-on but appearently not included. Morgan may believed that the German 109 should be in a better condition and thus assume the number best to be rounded from 1.375 to 1.4.

View attachment 888168

Again I don't know what is your insistance on 109's CLmax to must be exactly over 1.4, while other plane should perform badly with only 1.35. Technically, these were not solid evidence that a BF-109 should MUST have a CLmax advantage over most WW2 airplanes in clean-condition, as its airfoil profile was not optimal in terms of CLmax (NACA 2R1 superior to CYH but was overcasted by NACA 4 digits and more by 5 digits) at the time of WW2. Its H-tail area is small (14% of total wing area), which won't be expected to gain any CL from its tail-arrangement. Moreover, its slat doesn't help much on improving CLmax as quoted in the MTT report.

The conditon for the BF-109 V-24 tunnel test still mostly remained unclear, how closed the V-24 related to a production BF-109? is it tested with propeller or not? if it is, is it fully idling or at neutral thrust? what airpspeed was used? What reference area was used in calculating CLmax (Chalais Meudon did a mistake in calculating FW-190's CL polares, and was later to be corrected, whether the same happened to this 109, and also French had a tendency to use wing-area that excludes fuselage area, even NACA did similar error in calculating the CL for F4U-4). It is better if the report can be displayed with more details.
View attachment 888169

I'm not denying BF-109's ability to achieve CLmax over 1.4, actually I'd believe that most WW2 fighter planes should perform at these region. I would say since NACA 2R1-12 airfoil performs similarly with NACA 0012, and with similar in-line engine design and wing planform, P-39 could be made to be closely comparable with the BF-109, it was tested by NACA to have a CLmax around 1.35 in a stalling test, but is able to perform over 1.4 under certain Mach and Re numbers.
View attachment 888170
View attachment 888171
View attachment 888174

Look: I'm not "insisting" it has to be 1.4. I'm deriving that from multiple sources: The British RAE say it is 1.4. The German test in Chalais Meudon says 1.41. Extrapolating the power on Clmax at different g-loads from the RAE report, this points to 1.42.

You on the other hand, first say that the RAE measured 1.375 and the rounded it off to 1.4. But then when asked where this figure can be found in the RAE data, it turns out that it's actually a calculation made by you. And in this calculation you write that it is based on "CIAS", by which I assumed you mean "calibrated" IAS? when in fact the "C" has been added by you with no evidence whatsoever. In fact, the report clearly states "Indicated airspeed Vi" and there is no C to be found.

I have worked in the aeronautical industry for years, and all measurement equipment we used was calibrated regularly, and any INDICATED measurement taken should be corrected against a table or figure to provide a CALIBRATED value. And if the value in Table 4 actually was calibrated, then they would probably not have written Vi and talked about indicated airspeeds, but calibrated airspeeds.

So in summary, there is a much simpler explanation to all this: And that is that the "Indicated airspeed Vi" in the RAE report is exactly what it says it is: Namely the IAS as INDICATED by the trailing pitot system, and that this INDICATED airspeed was compared to the INDICATED airspeed in the cockpit, and that the 95.5 mph figure is thus missing calibration, and that when this was added, the RAE arrived at the Clmax 1.4 printed in the report.

In fact, that the Bf 109 has a slightly higher Clmax than the Spitfire's 1.36 is also perfectly logical, given that the Spitfire's wing has wash-out, which the Bf 109's doesn't.

But we have had this type of argument before, and I'm sure this Occam's razor and the three different numbers all indicating a Clmax of around 1.4 will not be as appealing to you as your creative data extraction from the report. And it seems we will just have to agree to disagree yet again. And unless new compelling data on this subject emerges, I don't plan to post anything more on this.

 

[Irregualr23]

You on the other hand, first say that the RAE measured 1.375 and the rounded it off to 1.4. But then when asked where this figure can be found in the RAE data, it turns out that it's actually a calculation made by you. And in this calculation you write that it is based on "CIAS", by which I assumed you mean "calibrated" IAS? when in fact the "C" has been added by you with no evidence whatsoever. In fact, the report clearly states "Indicated airspeed Vi" and there is no C to be found.

95.5mph is already the corrected reading given by the RAE test equipment system with swivelling pitot + suspended static head system,as the original 109's airspeed indicator still worked in parallel. Which resulted in the number of 1.375. This number of 95.5mph subtracts the number of ASI is then the POSITION ERROR CORRECTION of the airspeed system. This swivelling + suspended pitot-static system is designed to record the CIAS in a stall test. If this is uncalibrated, then where would you get the airspeed calibration from in stalling test? Why would RAE recorded 2 incorrect airspeed and hide the real one? Your argument itself is going against Occam's razor.

To make the matter worse, if you ever put the trailling static CIAS of 120.5mph for slats opening into the CL formula, you get 0.864, which is only 0.001 off with the table number of 0.865. It is clear, that the CL is derived from the trailing static CIAS, and this BF-109 scored CLmax of 1.375 in this stall test, and Morgan decided to round up figure to 1-decimal, which causes the myth of 1.4.

Agreeing with the RAE number automatically with no further check, you then should also automatically agreeing F6F to have CLmax of 1.52, or even 1.64(neutral thrust) as was determined by RAE using similar method. But you worked so hard to oppose against it, I don't understand.

Or otherwise, if you seemed to like the NACA way of determining CLmax by calibrating airspeed through flying a formation, as you've used to deny RAE's figure in the previous discussion regarding Hellcat's CLmax, then you would have to use a CLmax of 1.12 for the Spitfire, as in the same standard tested by NACA stalling test.

 

[Irregualr23]

Look: I'm not "insisting" it has to be 1.4. I'm deriving that from multiple sources: The British RAE say it is 1.4. The German test in Chalais Meudon says 1.41. Extrapolating the power on Clmax at different g-loads from the RAE report, this points to 1.42.

You on the other hand, first say that the RAE measured 1.375 and the rounded it off to 1.4. But then when asked where this figure can be found in the RAE data, it turns out that it's actually a calculation made by you. And in this calculation you write that it is based on "CIAS", by which I assumed you mean "calibrated" IAS? when in fact the "C" has been added by you with no evidence whatsoever. In fact, the report clearly states "Indicated airspeed Vi" and there is no C to be found.

I have worked in the aeronautical industry for years, and all measurement equipment we used was calibrated regularly, and any INDICATED measurement taken should be corrected against a table or figure to provide a CALIBRATED value. And if the value in Table 4 actually was calibrated, then they would probably not have written Vi and talked about indicated airspeeds, but calibrated airspeeds.

So in summary, there is a much simpler explanation to all this: And that is that the "Indicated airspeed Vi" in the RAE report is exactly what it says it is: Namely the IAS as INDICATED by the trailing pitot system, and that this INDICATED airspeed was compared to the INDICATED airspeed in the cockpit, and that the 95.5 mph figure is thus missing calibration, and that when this was added, the RAE arrived at the Clmax 1.4 printed in the report.

In fact, that the Bf 109 has a slightly higher Clmax than the Spitfire's 1.36 is also perfectly logical, given that the Spitfire's wing has wash-out, which the Bf 109's doesn't.

But we have had this type of argument before, and I'm sure this Occam's razor and the three different numbers all indicating a Clmax of around 1.4 will not be as appealing to you as your creative data extraction from the report. And it seems we will just have to agree to disagree yet again. And unless new compelling data on this subject emerges, I don't plan to post anything more on this.

I don't understand your opinion around CLmax, you are keep repeating an opinion that "BF-109 is of 1.4, others been inferior only 1.35"over the years, in IL-2 forum and in this forum, you kept denying any other claim to have an airplane with a CLmax over 1.4, or in other word, you never wish to see the figure that other ww2 fighter scores a better CLmax than 109's. You kept denying P-40's claim, P-47, FW-190,and Yaks (Oh I do agree with the Yak one as CYH is indeed inferior).

If you really worked in aeronautical industry, you would have know that it is not hard to reach a power-off CLmax of 1.5 for a propeller driven airplane, and even 1.8 is achivable. Your selective opion surrounding WW2 single engine fighter, especially with 109, making your professional creditability suspecious.

 

[Steamed_Banana]

Do we have an agreed upon CL max number for most WW2 fighters? Is there a list somewhere?

 

[bada]

If you really worked in aeronautical industry, you would have know that it is not hard to reach a power-off CLmax of 1.5 for a propeller driven airplane, and even 1.8 is achivable. Your selective opion surrounding WW2 single engine fighter, especially with 109, making your professional creditability suspecious.

Well, i don't know where your obsession with CLmax comes from, but the only situation when you can achieve it , it's when all "hypersustentation devices" are activated. This mean mostly at landing speed and being a drag-wall with zero energy. Not a situation that you would like to be found in an air combat, where you would only drop flaps in specific cases and only a few degrees. So, don't know what the CLmax has anything to do with the topic actually ...

 

[Galahad]

(Sorry, don't know if this has already been answered)

How that time were they able to measure (to verify the calculated data) the actual turning radius in flight? And how could one determine the altitude and speed where the tightest circle was possible?