Dora vs Mustang: Turning

[Yo-Yo]

No, there is no 0 deg AoA CL figure, the line stops before 0 at around 2 deg AoA.

 

Do you know EXTRAPOLATION word? :) Or are you really think that CL vs AoA has a kind of discontinuity or a sudden change near 0 degree AoA???

[Kurfürst]

The Clmax of the Me109 has been measured both by British RAE and by the Germans themselves in the Charles Meudon wind tunnel. They both agree the Clmax for the wing as such (not wing section data like you posted!) is around 1.4.

 

Correction - the British did not measure ClMax of the 109E at all, they simply guessworked it from available Clmax figures for the Spitfire - which themselves were estimations from stall speed tests.

 

As for the Clmax measured at Charles Meudon - its a rather useless figure without stating the conditions.

 

This is of course for the Me109E but if you for some reason think the Me109G and K will be significantly different

 

What about the F-K having different wings, flaps and slats and wingtips...?

 

P.S. Not that I find any particular Clmax figures especially attractive but when guesswork is countered by guesswork, it is useless.

[Yo-Yo]

 

 

 

Again, read NACA report 829, the Corsair with the same airfoil features a near identical clean wing CL max. That is proof enough.

 

 

 

 

Corsair had 1.37 in clean configuration (Gliding).

[Pilum]

That having been said you seem to have already made up your mind on this matter, irrespective of what'ever evidence is provided, so I don't expect you to change your opinion.

 

Well I agree about made up minds only in my opinion it is yours: You began by claiming that the Clmax should be 1.7 for the Me109 and have progressed from basing this on 2D wing profile data for slats and when this failed propping up your theory on data for an American dive bomber and a gull winged carrier based fighter based on the fact that they use airfoils from the same NACA family. Why this can hardly be called evidence has already been explained to you but you persist anyway. So to me it seems you are the one who has his mind made up not me.

 

Remember that the onus is on you not me to provide credible evidence. I base my numbers on actual measured data on the Me109. Both German and British measurements place the Clmax at 1.4 to 1.45. You are pushing for 1.7 so it is up to you not me to provide the evidence for this. So far you are coming up short.

[Pilum]

Correction - the British did not measure ClMax of the 109E at all, they simply guessworked it from available Clmax figures for the Spitfire - which themselves were estimations from stall speed tests.

 

As for the Clmax measured at Charles Meudon - its a rather useless figure without stating the conditions.

 

 

 

What about the F-K having different wings, flaps and slats and wingtips...?

 

P.S. Not that I find any particular Clmax figures especially attractive but when guesswork is countered by guesswork, it is useless.

 

Based on the way Hummingbird frames his arguments and his posting style I was actually beginning to wonder if Hummingbird and Kurfurst were one and and the same person but now that you are here I guess that is not the case right? :smilewink:

 

Concering your statement that the Britsh Royal Aeronautical Establishment estimate of the Me109E Clmax is guesswork: First of all the RAE is a professional establishment so I don't agree with your opinion that they would publish guesswork. Secondly, I have actually read RM2361, Messerschmitt Me109 handling and manouverabity test, by M.B. Morgan & D.E Morris where this estimate is documented. Morgan was in his time a respected researcher at the RAE and what you call guesswork was actually a measurement with a swiveling pitot head suspended 60 ft behind the plane. Now the reason you trail a pitot is exactly for the reason to get an accurate measurement. So how you can call this guesswork is beyond me.

 

Anyway, since you usually have strong opinions on Me109 performance numbers and have dissed our input and the RAE measurements of Clmax=1.4 as guesswork, what is your opinion on the Me109E Clmax then?

 

Hummingbird think's it should be 1.7. So what is your estimate?

[Hummingbird]

Corsair had 1.37 in clean configuration (Gliding).

 

Clmax figures from NACA report 829:

 

F4U = 1.6

P-51 = 1.28

 

 

 

Edited September 2, 2014 by Hummingbird

[Hummingbird]

Well I agree about made up minds only in my opinion it is yours: You began by claiming that the Clmax should be 1.7 for the Me109 and have progressed from basing this on 2D wing profile data for slats and when this failed propping up your theory on data for an American dive bomber and a gull winged carrier based fighter based on the fact that they use airfoils from the same NACA family. Why this can hardly be called evidence has already been explained to you but you persist anyway. So to me it seems you are the one who has his mind made up not me.

 

Remember that the onus is on you not me to provide credible evidence. I base my numbers on actual measured data on the Me109. Both German and British measurements place the Clmax at 1.4 to 1.45. You are pushing for 1.7 so it is up to you not me to provide the evidence for this. So far you are coming up short.

 

Again you keep stating a CLmax of 1.4 which is not what was measured at Charles Meudon, the figure measured there was 1.48, and for a shorter wing without slats. In other words it was a measurement of a low AR wing with the 2R1 airfoil. An increase in the AR would lower the Cdi and slightly increase the CLmax, whilst the addition of outboard slats would further increase the overall CLmax by as much as 20%.

 

I have provided ample evidence to support my points already, incl. windtunnel tests from the same institute on wings with the airfoil types in question and with similar planforms. That you continue to ignore/deny these is your problem, not mine.

 

The facts are clear:

 

1. The F4U's wing utilizes the exact same NACA 23XXX airfoil as the FW190, and the measured CLmax of the F4U's wing was ~1.6 in clean wing configuration, pretty much exactly the same as the FW AG measurements. In the same windtunnel the P-51's wing was tested and a CLmax of 1.28 was achieved.

 

 

2. Airplane no.7 (an A25) with similar wing planform and outboard wing slat installation as the Bf-109 F series onwards was measured with a CLmax of 1.8.

 

 

To back up this evidence we need again only look as far as the landing speeds & take off distances of the aircraft in question:

 

Landing speed / Take off distance

BF109G6 at 3148 kg = 140 kph / 300 m

FW190D9 at 4270 kg = 170 kph / 365 m

FW190A8 at 4300 kg = 172 kph / 430 m

P-51D at 4445 kg = 178 kph / 487 m

Edited September 2, 2014 by Hummingbird

[Hummingbird]

Do you know EXTRAPOLATION word? :) Or are you really think that CL vs AoA has a kind of discontinuity or a sudden change near 0 degree AoA???

 

Do you honestly want to argue against the figures in the NACA document?

[Yo-Yo]

Do you honestly want to argue against the figures in the NACA document?

 

My honest answer is: please calculate for the Corsair what AoA it would have at the maximal speed if it had this CL vs AoA dependance you quoted with CL = 0.6 at zero AoA...

 

Then I will post the profound NACA report data about F-4U flight charactersitics having more realistic CLmax value.

 

By the way, are you sure that FW had the same airfoil thickness and wing twist F-4U had?

[Pilum]

Again you keep stating a CLmax of 1.4 which is not what was measured at Charles Meudon, the figure measured there was 1.48, and for a shorter wing without slats. In other words it was a measurement of a low AR wing with the 2R1 airfoil. An increase in the AR would lower the Cdi and slightly increase the CLmax, whilst the addition of outboard slats would further increase the overall CLmax by as much as 20%.

 

I have provided ample evidence to support my points already, incl. windtunnel tests from the same institute on wings with the airfoil types in question and with similar planforms. That you continue to ignore/deny these is your problem, not mine.

 

The facts are clear:

 

1. The F4U's wing utilizes the exact same NACA 23XXX airfoil as the FW190, and the measured CLmax of the F4U's wing was ~1.6 in clean wing configuration, pretty much exactly the same as the FW AG measurements. In the same windtunnel the P-51's wing was tested and a CLmax of 1.28 was achieved.

 

 

2. Airplane no.7 (an A25) with similar wing planform and outboard wing slat installation as the Bf-109 F series onwards was measured with a CLmax of 1.8.

 

 

To back up this evidence we need again only look as far as the landing speeds & take off distances of the aircraft in question:

 

Landing speed / Take off distance

BF109G6 at 3148 kg = 140 kph / 300 m

FW190D9 at 4270 kg = 170 kph / 365 m

FW190A8 at 4300 kg = 172 kph / 430 m

P-51D at 4445 kg = 178 kph / 487 m

 

No, I do not keep stating 1.4, I have said 1.4 to 1.45. The 1.4 comes from the British flight test which you studiously choose to ignore and the 1.45 from the German Charles Meudon wind tunnel test.

 

You on the on the hand have persisted in stating 1.48 in bold text three times now for the Charles Meudon test. You cherrypicked the highest value in the test series results I have found which were 1.42, 1.45, 1.44, 1.42, 1.44, 1.48, 1.43 and 1.45. Taking the average of these we get instead 1.43 not 1.48 as the German estimate for the Me109E. So it seems my estimate of 1.45 was a bit too generous.

 

Since I agree with Yo-Yo that Cl=0.6 at low aoa like the figures you posted seemed high, I had a closer look at the figures both for the F4U (Airplane 6) and the Shrike A25 dive bomber (Airplane 7) you posted and if you look at the fine print at the very bottom you will se that they are Clmax figures with full flap deflection: 50 degrees for airplane 6 and 60 degress for airplane 7. So your argumentation for a clean wing Clmax of 1.58 and 1.7 for the Fw190 and Me109 just went out the door I’m afraid.

 

However, there is in fact a Clmax figure in NACA 829 for the F4U with no flap deflection on page 20 (Figure 14) and here the Clmax can be read off as between 1.1 to 1.25 depending on service condition.

 

So based on your persistent argumentation on the likeness between the Fw190 and F4U we can now conclude that the Fw190 should have a Clmax of 1.1 to 1.25 depending on service condition. No wait, since you argued for the 1.28 service condition Clmax for the P51 we should select the service condition value which is 1.1 for the F4U as well and based on the likeness we should consequently assign the same for the Fw190 right? :music_whistling:

 

Finally, how on earth can you call landing and take off speed figures evidence in this context? These are obviously with flap deflection, larger for landing and less for start, different between aircraft and different makers/user probably use different speed margins to stall. So there is no way you can use these to determine clean wing Clmax.

[Yo-Yo]

I must add that CLmax we are talking about is different regarding the conditions we measure it.

CL measured at wind tunnel tests generally is higher than trimmed CL.

[[DBS]TH0R]

Very interesting conversation.

 

Since I agree with Yo-Yo that Cl=0.6 at low aoa like the figures you posted seemed high, I had a closer look at the figures both for the F4U (Airplane 6) and the Shrike A25 dive bomber (Airplane 7) you posted and if you look at the fine print at the very bottom you will se that they are Clmax figures with full flap deflection: 50 degrees for airplane 6 and 60 degress for airplane 7. So your argumentation for a clean wing Clmax of 1.58 and 1.7 for the Fw190 and Me109 just went out the door I’m afraid.

 

However, there is in fact a Clmax figure in NACA 829 for the F4U with no flap deflection on page 20 (Figure 14) and here the Clmax can be read off as between 1.1 to 1.25 depending on service condition.

 

So based on your persistent argumentation on the likeness between the Fw190 and F4U we can now conclude that the Fw190 should have a Clmax of 1.1 to 1.25 depending on service condition. No wait, since you argued for the 1.28 service condition Clmax for the P51 we should select the service condition value which is 1.1 for the F4U as well and based on the likeness we should consequently assign the same for the Fw190 right? :music_whistling:

 

In comparison, Figure 16 on page 21 is also interesting - showing CLmax of a "low drag wing" from Plane 1 (P-51B by the looks of it). Unless I am mistaken, also with no flap deflection (δf=0°). Is that where the CLmax value of 1.28 comes from?

Edited September 3, 2014 by T}{OR
δf

[Yo-Yo]

And this is the ace from the sleeve:

 

ALL THESE STALL TESTS MEANS NOTHING as we are talking about turn rate, especially about the turn rate at more or less hihg altitude.

[Wolf Rider]

My honest answer is: please calculate for the Corsair what AoA it would have at the maximal speed if it had this CL vs AoA dependance you quoted with CL = 0.6 at zero AoA...

 

Then I will post the profound NACA report data about F-4U flight charactersitics having more realistic CLmax value.

 

By the way, are you sure that FW had the same airfoil thickness and wing twist F-4U had?

 

 

Oooo... is a Corsair on the way to the virtual livery? :pilotfly:

[Yo-Yo]

Oooo... is a Corsair on the way to the virtual livery? :pilotfly:

 

Not yet... as we are on the way to Europe.

[Wolf Rider]

:)

Edited September 3, 2014 by Wolf Rider

[Pilum]

Very interesting conversation.

 

In comparison, Figure 16 on page 21 is also interesting - showing CLmax of a "low drag wing" from Plane 1 (P-51B by the looks of it). Unless I am mistaken, also with no flap deflection (δf=0°). Is that where the CLmax value of 1.28 comes from?

 

Yes, the 1.28 comes from NACA 829 which also states 1.4 (Page 9 figure 4) for the P-51 in good condition and no flap deflection. This is interesting since it can be debated which one should be used. One could argue also for the 1.4 figure because some of the data (especially cited high speed data) on German planes is usually given for sealed and polished conditions. In addition, since the laminar airfoil on the P-51 requires it to be in good condition to give the benefits of the low drag bucket (i.e. the usually cited top speed figures) it is reasonable also to use the 1.4 good condition figure for the Clmax as well.

[Pilum]

I must add that CLmax we are talking about is different regarding the conditions we measure it.

CL measured at wind tunnel tests generally is higher than trimmed CL.

 

Yes, since the aircraft is stable there is a need for a negative force on the stabilizer/elevator to balance the airplane which will detract from the wings lifting force. So this could perhaps also explain the difference between the British Clmax value of 1.4 for the Me109E attained in flight, i.e. in balance and the German wind tunnel test. OTOH the difference could be due to how the wind tunnel correction factors were applied in the German test.

[Pilum]

And this is the ace from the sleeve:

 

ALL THESE STALL TESTS MEANS NOTHING as we are talking about turn rate, especially about the turn rate at more or less hihg altitude.

 

Well I agree with your statement about the high altitude turn but remember that most data available for comparisons of WW2 aircraft is for turn times at 1Km altitude and here the Clmax is important since the best turn time is attained at the intersection of the stall limit and the power limit at such low low altitudes. There is however a slight reduction due to Mach effects: For example, If I in my C++ simulation assume the Clmax for Fw190 is 1.35 then I get Cl available at best turn speed 1.31 at 1 Km altitude which is a slight reduction but the turn is still determined by the Clmax albeit reduced for Mach effects.

 

At a higher altitude, say 8 Km the Cl used at best turn is 1.11 while the Clmax as limited by Mach is around 1.25. So yes, I agree that for high up Clmax is not limiting but at the low level most simulator engagements occur Clmax is important.

[Yo-Yo]

Well I agree with your statement about the high altitude turn but remember that most data available for comparisons of WW2 aircraft is for turn times at 1Km altitude and here the Clmax is important since the best turn time is attained at the intersection of the stall limit and the power limit at such low low altitudes. There is however a slight reduction due to Mach effects: For example, If I in my C++ simulation assume the Clmax for Fw190 is 1.35 then I get Cl available at best turn speed 1.31 at 1 Km altitude which is a slight reduction but the turn is still determined by the Clmax albeit reduced for Mach effects.

 

At a higher altitude, say 8 Km the Cl used at best turn is 1.11 while the Clmax as limited by Mach is around 1.25. So yes, I agree that for high up Clmax is not limiting but at the low level most simulator engagements occur Clmax is important.

 

I mean that even at low altitude 100 m/s (360 kph) that is typically the best sustained turn speed Mach number is about 0.3M. CL max difference between stall (0.12-0.15 M) speed and the best sustained turn speed can be up to 0.15-0.2 (15%).

If we take in consideration the corner speed and instanteneous turn the difference becomes greater and, moreover, different airfoils have very differnet cirves for it vs M and Re.

 

For example, low-drag airfoils are better for 0.5-0.7M in comparison with conventional 23 or 44 NACA series.

Edited September 3, 2014 by Yo-Yo

[[DBS]TH0R]

Yes, the 1.28 comes from NACA 829 which also states 1.4 (Page 9 figure 4) for the P-51 in good condition and no flap deflection. This is interesting since it can be debated which one should be used. One could argue also for the 1.4 figure because some of the data (especially cited high speed data) on German planes is usually given for sealed and polished conditions. In addition, since the laminar airfoil on the P-51 requires it to be in good condition to give the benefits of the low drag bucket (i.e. the usually cited top speed figures) it is reasonable also to use the 1.4 good condition figure for the Clmax as well.

 

Both tests (Figures) apparently feature propeller removed with no flaps, wind speed 60 MPH.

 

Figure 16 is also accompanied by text below it where comments values from Figure 4: "The maximum lift coefficient of 1.44 for the faired and sealed condition and of 1.40 for the service wing are higher than those obtained for airplanes 5 and 6".

 

Perhaps there are some graph scale errors in the Figure 16 with the X & Y axis.

 

 

EDIT: Things like these make me wonder if Hummingbird actually studied the document or just searched it for the values he wanted to find...

Edited September 4, 2014 by T}{OR

[Hummingbird]

Having read the document again I will concede that Pilum was right and I was wrong about the report - I apologize for my mistake Pilum.

 

I find all of this quite odd however considering the following:

 

Even more strange the results then become when u consider that the F4U featured a considerably lower stalling speed than the P-51, and was considered a much better turn fighter in comparitive trials.

 

As for the Charles Meudon test, again it needs to be remembered that it was for a shorter wing without slats, and that a higher AR plus the addition of slats would've increased the CLmax. Thus I still maintain that a CLmax of 1.65-1.7 for 109F,G & K is plausible.

 

http://www.grc.nasa.gov/WWW/k-12/airplane/Images/downwash.gif

Edited September 4, 2014 by Hummingbird

[Hummingbird]

Interestingly I found this:

http://digital.library.unt.edu/ark:/67531/metadc65534/m1/42/

 

Seems that there are a lot of discrepancies with the NACA windtunnel tests, esp. those with the 6 series airfoils. Surface cleanliness are very important for the 6 series airfoil if it is to achieve good results, much more so than the more conventional airfoils.

Edited September 4, 2014 by Hummingbird

[Hummingbird]

NACA 66(1)-212

NACA 23012

[Pilum]

Having read the document again I will concede that Pilum was right and I was wrong about the report - I apologize for my mistake Pilum.

 

I find all of this quite odd however considering the following:

 

Even more strange the results then become when u consider that the F4U featured a considerably lower stalling speed than the P-51, and was considered a much better turn fighter in comparitive trials.

 

As for the Charles Meudon test, again it needs to be remembered that it was for a shorter wing without slats, and that a higher AR plus the addition of slats would've increased the CLmax. Thus I still maintain that a CLmax of 1.65-1.7 for 109F,G & K is plausible.

 

http://www.grc.nasa.gov/WWW/k-12/airplane/Images/downwash.gif

 

I did a calculation of the delta in Clmax as affected by a change in aspect ration 5.22 (Me109E) to 6.14 (Me109K4) and this only gave a 0.02 increase when I used the NACA 230012 profile Clmax 1.6 as base. So there is not much of a difference in theoretical Clmax between the Emil and the Kurfurst as you would like to believe.

 

Concerning the 1.65 to 1.7 figure you can’t reason as you do: Irrespective if we are talking about the Emil or Kurfurst, the inner part of the wing will stall at around 18 degrees. At this aoa the slats are fully out because they start to deploy at around Cl=0.8 and are fully out at 18 degrees aoa and Cl=1.4 to 1.45. Now if we continue to increase the aoa, the slatted part of the wing will happily go along and the lift will increase on this part of the wing. However, what happens on the rest of the wing is that the flow separates and lift is lost. So the overall effect is that the wings Clmax goes down between 20-30 degrees aoa, ergo you reach your wings peak lifting capacity of Clmax=1.4 to 1.45 at 20 degrees aoa and if you go to higher aoa to try to utilize what the slats can do on that part of the wing, you loose more than you gain on the other part of the wing. You really need to let this go now…..

 

Also, I think that the reason the F4U turns better than the P-51 is simply because it has an 8% lower wing loading and 8% better P/W ratio so no mystery there.

 

Finally, I raise my hat since it is a rare day on the internet when someone concedes to being wrong about anything!

Edited September 4, 2014 by Pilum