WWII Rate of Turns

[Zipper730]

Which stall speed?

Generally, I tend to use the power-off stall speed as a guideline.

At which altitude?

That has to do with mach effects on airspeed? I have no idea how to compute that out, though I'm curious if there are any form of correction factor to come up with something remotely accurate, reasonably speaking.

An aircraft can stall out on full power while pulling many "G". Thats where these "spanwise lift distribution" discussions are important. A plane that is completely benign coming in to land obviously at 1 G can stall with no warning at all its power on limit.

Accelerated stall piles on more loads on the wing, wing twists start to take hold, you have airflow asymmetries that are involved (turns), and things happen more abruptly. Snap-rolls are awesome to watch -- a rapid pitch up and jerky but fast roll. It also dumps speed so you can force overshoots with it..

Any plane that needs to pile on the G load to do its job, such as fighters, fighter-bombers, attack planes, etc, while it may be sluggish in roll, isn't likely to be sluggish in pitch, as that's the working parameter in all combat maneuvering.

Yet attack planes often do seem to require more pounds per-g than do fighters, and are often trimmed nose-up for dive-recovery. That said, I would not suspect that they were extremely sluggish in terms of pitch -- just moreso than fighters.

What do you mean by "its power on limit"?

I guess power on stall?

One thing I don't get is why AOA indicators have been so slow to take hold in the civilian world.

Actually, that is good point: When did they first appear in the commercial aircraft industry?

Calculating the Stall Speed is easy.
Here is the formula:

View attachment 567737

V = Stall Speed (Metres Per Second)
L = Lift Force (Newton's)
CL = Wing Lift Coefficient
P = Air Density (1.225kg/m3 at sea level)
A = Wing Area (Metres Squared)

Just out of curiosity

• Newtons is 1/(kg*m/s^2), correct?
• Coefficient of lift is a ratio of the lift to dynamic force right?
• What would you use for imperial measurements in terms of lift-force and air-density? I can enter either one, but I figure it's useful to be able to use either conversion factor.

On this website it will calculate the stall speed for you
Airplane Aircraft Wing Lift Design Equations Formulas Calculator - Velocity

Cool

Kurfürst - R.A.E. - Messerschmitt Me.109 Handling and Manoeuvrability Tests
Here are the British stall speed tests to determine the CL_Max (Wing Lift Coefficient) for BF-109E

So they plugged in all the other figures to get the C/L?

 

[CORSNING]

sustained 360 horizontal turn
A7M2 - 14-15 sec
Ki-84 - 17 sec
Ki-100 - 17 sec
N1K2-J - 17 sec
Ki-44-II - 18 sec
J2M3 - 18 sec
BF-109G-10 - 19 sec
F4U-4 - 20 sec
La-9 - 20-21 sec
F6F-5 - 21-22 sec
P-38J - 22 sec
Ki-94-II - 23 sec
P-47N - 26 sec

Laurelix,
I have a few questions about the times you have posted for the above aircraft sir.
1. What is your source for all your posted times?
2. At what altitude were these times recorded?
3. Are any of the aircraft take-off weights listed in your sources?
I have a listing of all the Soviet turn times recorded at 1,000 m. and a list of about 85 A/C turn times at 4,000 m.
which according to Erik Pilawskii these are observed tests. The above aircraft are not listed for the sourced I
have and I am very interested in adding them if the source is solid.

Thank you in advance, Jeff

 

[Laurelix]

Laurelix,
I have a few questions about the times you have posted for the above aircraft sir.
1. What is your source for all your posted times?
2. At what altitude were these times recorded?
3. Are any of the aircraft take-off weights listed in your sources?
I have a listing of all the Soviet turn times recorded at 1,000 m. and a list of about 85 A/C turn times at 4,000 m.
which according to Erik Pilawskii these are observed tests. The above aircraft are not listed for the sourced I
have and I am very interested in adding them if the source is solid.

Thank you in advance, Jeff

All calculated. But it matches sources. For example I calculated 19 sec for La-7 and that's exactly what the Russian tests concluded.

 

[CORSNING]

sustained 360 horizontal turn

The following is what I have on file for these aircraft. The 4,000 m figures are from
Erik Pilawskii's book Fighter Aircraft of WW2, A Comparative Study. He states in
his book that the figures are observed. The 1,000 m figures are Soviet turn times.

Ki-43-I - 12.5-13 sec 10.8-11/600 m from pilots handbook. (5,254 lb.)
A6M2 - 13-14 sec 14.1/4,000 m (5,314 lb.)
A6M3 - 14-15 sec 15.0/4,000 m (5,609 lb.)
A6M5 - 15-16 sec 17.0/4,000 m (5,975 lb.)
Ki-61-I - 16 sec 18.0/4,000 m (Ki.61-Ib/6,901 lb.)
N1K2-J - 17 sec 18.0/4,000 m (9,261 lb.)
BF-109E - 17 sec 20.2/4,000 m, 18.92/sea level (German tests)
P-39N - 17-18 sec 19.0/1,000 m & 19.0/4,000 m (7,056 lb. both tests)
Yak-9 - 18 sec 16-17/1.000 m (6,327 lb.), 18.0/4,000 m (6,334 lb.)
Yak-3 - 18 sec 17.0/1,000 m (5,945 lb.), 20.0/4,000 m (5,935 lb.)
P-40F - 18 sec 18.5 A&AEE tests
Yak-9U - 18-19 sec 19.5/1,000 m & 18.5/4,000 m (7,056 lb. both tests)
BF-109F-4 - 19 sec 19.6 - 20.8/1,000 m (6,398 lb.) 20.5/4,000 m (6,372 lb.)
La-7 - 19 sec 18.5/1,000 m (7,276 lb.), 19.5/4,000 m (7,104 lb.)
F4U-1 - 21 sec 19.5/4,000 m (11,990 lb.)
P-51D (67Hg) - 22 sec 21.5/4,000 m (9,514 lb.)
FW-190A-5 - 23 sec 21-22/1,000 m. (8,974 lb.)

Two figures for one altitude signify left-right turns.

, Jeff

 

[Laurelix]

Mind you Yak-9U tests probably shown 19.5 because in the beggining it didn't have fuel injection and was limited to 1500hp but later had 1650hp which would of given it 18-19 sec

as for BF-109E test, they must of screwed something up really bad during the test to get 23-26 sec because the aircraft was capable to turn with the spitfire initially when it deployed its flaps. This wouldn't be possible if it had 23-26 turn time. You'd need the BF-109E to have like 1.02 CL_Max

the British themselves tested the stall which was 154km/h (1.4 CL) compared to the 163km/h on Yak-3. So BF-109E has lower stall speed than Yak-3 and with 1160hp for 2530kg weight which gives slightly worse power to weight ratio than yak-3. With 9-11km/h lower stall speed the BF-109E should easily beat Yak-3 in a turn fight. Now if Yak-3 has 17-18 sec turn time, how can BF-109E have 23-26 sec?

just goes to show how flawed turn rate tests can be and sometimes it's just better to trust the maths and the physics

also the P-40F turn rate of 18.5 sec at 8500m is complete nonsense do you even know how lack luster it's engine is at that altitude to sustain a turn, never mind the extremely low air density

P-40F has 3855kg loaded weight, 21.93m2 wing area, 850 horsepower at 9000m.
The air density at 8500m is 0.4951kg/m3.
P-40F has 1.41 CL max wing lift.

At 8500m the P-40F would have 253km/h stall speed (imagine how huge the turn radius is)
On top of that the engine is only spewing out 850 horsepower trying to support a 3855kg of weight... getting 18.5 sec sustained turn in these conditions is nothing short of bullshit

I don't know about you but my turn times make far more sense and look far more realistic than these actual tests than have so many other factors that could effect it and cause the test to be ruined and then getting the wrong values.

at sea level with 1.225kg/m3 air density the P-40F would have 161km/h stall speed and at sea level it's engine can produce 1420 horsepower. BF-109E has lower stall speed and FAR BETTER power to weight ratio to sustain turns than P-40F.

 

[CORSNING]

OK then, I pulled the P-40F @ 28,000 ft. until I can locate and study the
report closely. I believe 18.5 is the turning ability for this aircraft. To
compare, the Spitfire LF Mk.IX's turn time was 18.5/1,000 & 4,000 m.

Since you mentioned it, seems to me the 23-26 seconds for the Bf.109E-3
was measured with some trouble with the slats opening...? I believe the 18.92
and 20.2 times were correct. 17.0 seconds would put it on par with
the Yak-9, and that, it was not.

Nope, I found the Bf.109E-3 report. The supercharger wasn't functioning
correctly.

 

[Laurelix]

OK then, I pulled the P-40F @ 28,000 ft. until I can locate and study the
report closely. I believe 18.5 is the turning ability for this aircraft. To
compare, the Spitfire LF Mk.IX's turn time was 18.5/1,000 & 4,000 m.

Since you mentioned it, seems to me the 23-26 seconds for the Bf.109E-3
was measured with some trouble with the slats opening...? I believe the 18.92
and 20.2 times were correct. 17.0 seconds would put it on par with
the Yak-9, and that, it was not.

That's only what you think.

eighter way a plane with lower stall speed that can sustain it better will have superior sustained turn than a plane with higher stall speed (bigger turn radius) and worse sustainability. In this case BF-109E is on par in turn but it's not as fast as Yak-9. BF-109F/G obviously turned worse

 

[CORSNING]

That's only what you think.

Yep, me and all the guys who recorded the actual testing of the aircraft.

 

[Laurelix]

According to that book, Yak-9 is turning better than a spitfire LF IX?
I can tell you right now it's sustained turn is like 16 sec, not 18.5 sec
Otherwise La-7 turns as good as spitfire LF IX which too is nonsensical

 

[CORSNING]

The 18.5 turn for the La-7 was for a late 1945 version. The earlier
La-7 was tested at 20-21/1,000 m & 19.5/4,000 m.
I have nine tests for Spitfires from Mk.I to Mk.IX. None of these
tests recorded less than 17 seconds ability. However, the 17 seconds
for the Mk.I & II were at 4,000 m.
I remember reading about a fighter competition in Italy where Soviet
and Allied pilots flew their fighter aircraft against each other in mock
combat. One of the British pilots claimed that the interior of the Yak-9
was very crude but none of the aircraft there were able to stay with the
Yak-9 through maneuvers. The Yak-9 in question was the Yak-9DD,
perhaps the least maneuverable of the series.

 

[Zipper730]

I think it's about time we bring this thread back to life.


BTW: Notes to self, to determine newtons in regard to lift, use mass in kg * 9.80665; propulsive efficiency is the percentage of HP that gets turned into thrust

 

[Zipper730]

This comes from a multi series article on Greg's Planes and Automobiles about the P-47, and an image (to be added shortly) which covers the Me-262 (and sustained turn-rates with airspeeds).



This seems to cover a bit, though I'm not sure I get everything here (the propeller efficiency thing I kind of didn't quote grasp). There were links below, that I think would be useful to everybody here, and probably me when my mind works better as things start coming online. I did get up at around 7 PM, so today might not be my day to do this.

 

[Zipper730]

L Laurelix97 , swampyankee

The coefficient lift figures which you posted earlier on the Ki-84 (CL Max w/ Flaps 0: 1.46; w/ Flaps 15: 1.7; w/ Flaps 30: 1.92): I'm curious if theres any online sources that have reliable CL figures for aircraft seen in WWII?

Furthermore, when it comes to altitude: Would you simply input a different air-density that correlates to the different altitude and air-temperature?

As for computing power to weight: Does that produce accurate sustained turning performance? After all, with different propellers producing different thrust, different thrust coming out of the exhaust system at different altitudes, and tip-velocities nearing the speed of sound at high speeds seem all to be something that would affect overall thrust.

Regarding the formula FPS * (550*HP). For a 2000 horsepower engine, I end up with 1,100,000 foot/pounds. I'm not sure how that can be used to provide overall engine thrust, as I've never heard thrust figures that high for any propeller engine.

 

[Laurelix]

someone copied and pasted Ki-84 manual details into the comment section here.
I happen to come across it and realised that it included wing lift coefficient of the wings.
Nakajima Ki-84 Hayate / FRANK - fighter

 

[Zipper730]

Was there any changes made to the Ki-84 wing

 

[Laurelix]

Was there any changes made to the Ki-84 wing

all Ki-84's used the same wing.

 

[Zipper730]

I honestly should have bookmarked this particular page.

 

[GregP]

Reference post #124.

The A6M was NOT a weak airplane and its wings did not break off easily. U.S. fighters were stressed to 8 g's with a safety factor of 0.5, for an ultimate load factor of 12 g's. The A6M was stressed to 6 g's with a safety factor of 1.0, for an ultimate load factor of 12 g's.

This means that the U.S. fighter could sustain 8 g's many times with no damage. If loaded to over 8 g's, the structure would take it, but could be damaged beyond continued use. You'd expect structural failure at anything over 12 g's. For the A6M, it could sustain 6 g's many times without failure but could be damaged at loads over 6 g's. Again, you'd expect structural failure at anything over 12 g's.

The A6M was not and IS not flimsy, weak, or poorly made. It is a good, solid airplane that, like all other airplanes, has limitations. The A6M was designed to excel at dogfighting at speeds of 180 - 290 mph, and it did that job VERY well. Since the designer didn't have a 1,500+ hp engine to work with, he had to make design choices to get good performance. In the case of the A6M, that meant lighter structure and no armor, resulting in a plane that was good at dishing out punishment, but not so good at taking it. That was acceptable to the Japanese military.

When the same designer had a more powerful engine, he came up with the J2M Raiden. It was a match or better for most late-war Allied fighters in ceiling, armament, climb, and maneuverability. It was was slightly slower than most late-war U.S. fighters, but could still catch a B-29, something that many other Japanese fighters could not do. They just never got to built very many of them.

 

[GregP]

So, you believe that post above about the CL and the flight test report translation?

It MIGHT be true, but I have seen too many people with an agenda make false claims to believe it without seeing the reference. The reference he translated might also be bogus and I can't find it. Maybe not, but maybe. I can't say for sure. So, it falls into hearsay, for me rather than reference values. One post makes it seem like Ron is Shinpachi in this forum. If so, I have more faith in the text than before.

I found an English language flight test dated Nov 46 and found no CL or empty weight.

Hi Shinpachi, was that post from you?

 

[Zipper730]

Okay, I was looking at the figures cited from America's Hundred Thousand, which I've put into an Excel sheet (then turned that into a screen-cap)

The red stuff was things I either know are wrong or strongly suspect, the gray item was something I was just unsure of: The P-61B's wing area is 662.36 square feet and, while I'm unsure the exact C/L for the P-51, I've heard some sources that listed numbers lower (1.5). I'm curious if anybody has more accurate data on the coefficient of lift figures for the aircraft in question since I have doubts as to the accuracy of the source.

The wing-area for the P-51 seems to vary a bit from 233 to 235.7 or so. I'm not sure why there are variations in this area.

Thanks