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Gaston444
12-27-2009, 01:34 AM
I've noticed you never hear WWII fighter pilots talk about the "Corner Speed" or the "Peak Turn Rate".

WWII turn tests are usually about the sustained turn time, or the minimum radius of turn.

In "Aces High", the "Corner Speed" or "peak turn rate" of the P-51D Mustang is said to be at around 280 MPH, at around 8 G with flaps down...

Was this determined from an actual flight test?

Consider the following comments by "The Society of Experimental Test Pilots" testing the P-51, P-47, FG-1 and F6F in 1988. The testing was limited to slightly short of maximum performance, but it is still close enough to be very significant in my view, especially considering the quality, and level of test experience, of these pilots...

http://bbs.hitechcreations.com.../topic,261798.0.html (http://bbs.hitechcreations.com/smf/index.php/topic,261798.0.html)


Here is the critical quote: "Corner speeds of all were very close to the maximum level flight speed,
implying very rapid energy loss when turning at the structural limit."


To me this implies that the actual "Corner Speeds" of the P-51/P-47 are at around at least 340-350 MPH, if not even higher...

Then there is the big increase in turn RATE mentionned here at very low speeds (at or below 200 MPH, and correlated in numerous similar Merlin P-51 combat accounts) with high prop pitch, lowered throttle and flaps:

http://www.spitfireperformance...hanseman-24may44.jpg (http://www.spitfireperformance.com/mustang/combat-reports/339-hanseman-24may44.jpg)


Note I think the 1988 test did not thoroughly explore the low-speed P-51 "trick", or the very low-speed sustained turn rate of all the aircrafts in detail, with various flaps-throttle configurations: Only METO is mentionned and no flaps... So I actually think BOTH "peak" turn performances are quite compatible... Here are the 1988 sustained turn comments:

"SUSTAINED TURN PERFORMANCE at METO at 10,000 ft.
The F6F out-turned the other three by a conclusive margin (1g). The other
three were all about the same."

It seems to me the peak turn performance speed of the P-51D, whether the "Corner Speed", or the best sustained turn rate, is to be found everywhere EXCEPT at around 280 MPH...

IF the "Corner Speed" is indeed widely accepted as being around 280 MPH for the P-51D Mustang (I suppose IL-2's P-51D is about the same), exactly WHEN was this tested in an actual real-metal P-51D, what was the DATE of the test, and what was the airframe's serial number used in the test?

From numerous combat anecdotes, it seems to me the P-51D's best sustained turn rate was around 180-200 MPH, and the Finnish Aces website has an interview with a well-known ace that places the peak sustained turn rate of the Gondola 5-gun Me-109G-6 at around 160-170 MPH...:

http://www.virtualpilots.fi/fe...icles/109myths/#g6r6 (http://www.virtualpilots.fi/feature/articles/109myths/#g6r6)

The quote goes:

" When the enemy decreased power, I used to throttle back even more. In a high speed the turning radius is wider, using less speed I was able to out-turn him having a shorter turning radius. Then you got the deflection, unless the adversary did not spot me in time and for example banked below me. 250kmh seemed to be the optimal speed."

That does NOT seem to match the common in-game "best sustained turn rate speed" for the Me-109G...

At the other end of the spectrum, for a different type of performance, the actual 1988 tests have the "Corner Speed" of a P-51D at around 350 MPH at least, if not much more...

I would like to see the actual test date and airframe number of a P-51D's "Corner Speed" being at around 280 MPH...

Note that a LOT of WWII "performance data" is actually just calculated figures treated as if they were solid "real tests", even though they are not. A prime example of this is the multiplicity of Soviet "turn times" covering an unrealistic number of minute variants for each aircraft type. So far no test date or airframe number has surfaced out of that entire, and gigantic, "testing programme"... Hmmmm...

The lack of airframe code or serial#, control weight data or pilot handling comments is also a dead giveaway of "calculus tests". It would be nice to know exactly where the P-51D real-life peak turn data, if any, came from...

If the WWII source was so clear-cut and reliable, why did these test pilots bother to do those 1988 tests?

Gaston


P.S. I think that what is foiling "calculations" here is that ADDING power to a lenghty nose pulls the aircraft "out" of the turn, the longer the nose the worse the effect, therefore reducing power increases the turn rate at speeds well below "Official" calculated "Corner Speeds"... These calculations don't make ANY distinction with the effects of jet PROPULSION from the rear vs propeller TRACTION from the front... A pretty basic difference I would think...

Note how a shorter nose seems to tremendously boost the turn rate of the La-5 vs the Lagg-3, or that of the Ki-100 vs the Ki-61... Weight of course plays a big part, but the differences here were well beyond any calculation, and a well-documented surprise to the engineers in BOTH cases... It seems possible to me that the reduced nose-lenght "leverage" allowed more power to be put down without pulling the aircraft "out of the turn".

G.

BillSwagger
12-27-2009, 02:57 AM
Originally posted by Gaston444:
Here is the critical quote: "Corner speeds of all were very close to the maximum level flight speed,
implying very rapid energy loss when turning at the structural limit."


To me this implies that the actual "Corner Speeds" of the P-51/P-47 are at around at least 340-350 MPH, if not even higher...



I think thats quite a big leap in logic to make given that we don't have the actual test results to refer to, instead we see a summary.
It sounds like they tested these planes using a 1g turn, which makes more sense given the numbers.

Waldo.Pepper
12-27-2009, 03:22 AM
On this minor point...


Originally posted by Gaston444:
I've noticed you never hear WWII fighter pilots talk about the "Corner Speed" or the "Peak Turn Rate".

I suspect that this is because REAL WW2 pilots knew that by turning they were greatly increasing the danger to themselves. In short, obsessing about turning performance is for noobs, and they were much more interested in getting in - loosing off a few rounds - and then beating a hasty retreat as quickly as possible.

It turns out dogfight is not so much fun. Despite what the History Channel is trying to tell us.

X32Wright
12-27-2009, 04:33 AM
Keep in mind that most P-51s today are not flown past the 40"-50" Hg intake manifold pressure to not stress and preserve the Packard Merlin engine. In WWII they did not care much about this http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Anybody who had done extensive CEM with the Mustang knows that you look at the Intake Manifold Pressure gauge more than anything along with the rpm when flying this beast.

AndyJWest
12-27-2009, 06:31 AM
Gaston444 wrote:


Here is the critical quote: "Corner speeds of all were very close to the maximum level flight speed,
implying very rapid energy loss when turning at the structural limit."


To me this implies that the actual "Corner Speeds" of the P-51/P-47 are at around at least 340-350 MPH, if not even higher...

If you don't understand the implications of that quote, please don't cite it as evidence for anything. If a plane is losing energy, it is not in a sustained-rate turn, by definition.

And as for the suggestion that the length of the nose makes any difference to sustained turn rate, or whether thrust comes at the front or the rear, I think a little basic physics would suggest otherwise, though in any case, the thrust forces on a jet aircraft will be exerted on the engine itself, not the tailpipe.

M_Gunz
12-27-2009, 07:41 AM
The term Corner Speed was coined well -after- WWII so finding it quoted or taught before then is not proof
of anything but a desire to pursue yet another agenda.

Corner Speed is not pulling the highest G's, it is doing so at the smallest radius. Lift increases with the
square of speed, it takes about 1.4 times stall speed at minimum to make a 2 G turn and 2.4 times for 6 G's.
The actual number varies because nothing is 100% efficient and I round the square roots off too.
8 G's should roughly take 2.8 times stall which clean is around 100 mph for a P-51 depending on model and LOAD.

But when you can't handle or accept the physics then sure, drag out the anecdotes and play games with the
meanings of the words used, act like the people being quoted used perfect yet cryptic descriptions just for
later master-sleuths to discover the truths that have evaded mankind for so many decades even as the science
used has developed to a higher degree. But when you want something bad enough, first put the blinders on then
charge ahead.

JtD
12-27-2009, 08:10 AM
I've been thinking about replying at all, knowing it's going to be a waste of time, but eventually, so many errors can not be left uncommented.


Originally posted by Gaston444:
In "Aces High", the "Corner Speed" or "peak turn rate" of the P-51D Mustang is said to be at around 280 MPH, at around 8 G with flaps down...

Was this determined from an actual flight test?

It's a game, so there's no way for a game figure to come from an actual flight test.

If, however, you wonder how well this relates to real life figures, the answer is simple. Stall speed were determined frequently in flight tests. And these, plus the structural limit of the plane, are all you need to know for determining the peak turn rate.

So, for a 9100lbs P-51B a stall speed of 94 mph was tested. This means a 8g turn is possible at 266 mph.

Please note that this is instantaneous turn.


Originally posted by Gaston444:

Here is the critical quote: "Corner speeds of all were very close to the maximum level flight speed, implying very rapid energy loss when turning at the structural limit."

To me this implies that the actual "Corner Speeds" of the P-51/P-47 are at around at least 340-350 MPH, if not even higher...

And if we know knew anything about the planes used there, we might get to know something.


Originally posted by Gaston444:
Then there is the big increase in turn RATE mentionned here at very low speeds (at or below 200 MPH, and correlated in numerous similar Merlin P-51 combat accounts) with high prop pitch, lowered throttle and flaps:

http://www.spitfireperformance...hanseman-24may44.jpg (http://www.spitfireperformance.com/mustang/combat-reports/339-hanseman-24may44.jpg)

There's no increase in turn rate mentioned, he says he managed to turn inside the other guy. That could be a reduction in the turning radius. Also, no mention of the speed involved.


Originally posted by Gaston444:
It seems to me the peak turn performance speed of the P-51D, whether the "Corner Speed", or the best sustained turn rate, is to be found everywhere EXCEPT at around 280 MPH...

Ok, nice feeling, but where are the facts?


Originally posted by Gaston444:
IF the "Corner Speed" is indeed widely accepted as being around 280 MPH for the P-51D Mustang (I suppose IL-2's P-51D is about the same), exactly WHEN was this tested in an actual real-metal P-51D, what was the DATE of the test, and what was the airframe's serial number used in the test?

The P-51D in Il-2 can take 15 g's so the corner speed would be around 364 mph, if the stall speed was 94 mph again. Since it isn't, as it would be about 110 mph for a P-51 with the above mentioned weight, the corner speed in game is about 426 mph.


Originally posted by Gaston444:
Note that a LOT of WWII "performance data" is actually just calculated figures treated as if they were solid "real tests", even though they are not. A prime example of this is the multiplicity of Soviet "turn times" covering an unrealistic number of minute variants for each aircraft type. So far no test date or airframe number has surfaced out of that entire, and gigantic, "testing programme"... Hmmmm...

Hm. Yeah. So you never bothered to look. November 1943, La-5FN, no. 39210495, 19s sustained turn. Just as an example.


Originally posted by Gaston444:
If the WWII source was so clear-cut and reliable, why did these test pilots bother to do those 1988 tests?

Maybe because there are plenty of idiots around who neither understand basic aerodynamics nor believe in the test results of WW2 tests.



Originally posted by Gaston444:
P.S. I think that what is foiling "calculations" here is that ADDING power to a lenghty nose pulls the aircraft "out" of the turn, the longer the nose the worse the effect, therefore reducing power increases the turn rate at speeds well below "Official" calculated "Corner Speeds"... These calculations don't make ANY distinction with the effects of jet PROPULSION from the rear vs propeller TRACTION from the front... A pretty basic difference I would think...

So how exactly does the prop pull the plane "out" of the turn if the thrust vector is inward?
Where exactly does the "nose" of a plane start?
Corner speed has nothing to do with thrust, btw., it's just about g's and stall.


Originally posted by Gaston444:
Note how a shorter nose seems to tremendously boost the turn rate of the La-5 vs the Lagg-3, or that of the Ki-100 vs the Ki-61... Weight of course plays a big part, but the differences here were well beyond any calculation, and a well-documented surprise to the engineers in BOTH cases... It seems possible to me that the reduced nose-lenght "leverage" allowed more power to be put down without pulling the aircraft "out of the turn".

Please provide a number of documents that show the "surprise" of the engineers and how much the turn performance far exceeded calculations. Since it is so well documented, there must be a large number available. It's kind of a miracle that I missed all of them until now.
And how is a 19 seconds for a 360 sustained level turn a tremendous boost over the same 19 seconds for the same thing? That would be LaGG-3 vs. La-5, which essentially had the same sustained turn performance.

BM357_Sniper
12-27-2009, 09:22 AM
Originally posted by Gaston444:


<span class="ev_code_RED">In "Aces High", </span> the "Corner Speed" or "peak turn rate" of the P-51D Mustang is said to be at around 280 MPH, at around 8 G with flaps down...

It was after that, when I stopped reading. lol

Seriusly, have any of you gone over to those forums? I did out of curiosity and I felt like it should've been my 11 year old son instead of me. I had to leave when I realized I didn't own a gamepad.

I apologize in advance. http://forums.ubi.com/groupee_common/emoticons/icon_smile.gif

Kettenhunde
12-27-2009, 09:39 AM
Wow, there is quite a bit wrong with this statement both with science and engineering.


the "Corner Speed" or "peak turn rate" of the P-51D Mustang is said to be at around 280 MPH, at around 8 G with flaps down...


There is some misconceptions on just what "corner speed" or "maneuvering speed" actually is on an aircraft.

"Corner speed" or "maneuvering speed" is also termed Va in our V-speeds.

We seem to know the technical definition as Stall speed multiplied by the square root of the load factor. However the concept itself is being improperly applied.

It is not something that we "go faster" to define.

Va is the point at which our airplane will not longer stall at full control deflection before the airframe is damaged.


Va. Known as maneuvering speed. This has to do with the MAX speed at which you can safely stall an airplane.

http://www.askacfi.com/29/defi...ng-speed-and-vno.htm (http://www.askacfi.com/29/definition-of-va-maneuvering-speed-and-vno.htm)

If we go faster than Va, we can break our airplane before we stall it. The fighter with the higher velocity Va holds an advantage.

It is usually defined as beginning at the damage load factor (~6G's) so that we do not risk damage to the airframe.

Airframe damage has a very small chance of being non-fatal to the aircraft whereas airframe failure is always fatal.

Gaston444
12-27-2009, 02:52 PM
-OK, so the "Corner Speed" is the lowest speed at which the maximum "allowable" G can be pulled. What is "allowable"? IF that is 15 Gs on a P-51D (as you say), then they are refering to a value they did not reach, since they did not go beyond 6-7 Gs due to the age and value of the airframes.

So in effect, their comment about "Corner Speed being VERY close to Maximum level speed is a CALCULATED deduction, not something they actually tested... This seems odd and unlikely, given that it defeats their whole purpose of verifying what was not apparently clear to them, and thus worth the whole enormous trouble to have a test done in 1988...

They do speak of this turning at the "structural limit" as being a big speed bleeder, but if 15 Gs cannot be sustained for more than microseconds by the pilot in real-life, exactly how is there the TIME needed to create the dramatic bleed of the speed they comment on as being a serious issue? Microseconds at 15 Gs cannot bleed any significant amounts of speeds because it takes TIME to decelerate a 9000 lbs aircraft... Therefore what they refer to as the "structural limit" can only be the maximum allowable, unsustainable, turn at the 8 G accelerated stall limit which is the recognized P-51D limit...

So I think what is being confused here is the "engineering structural limit" of 15 Gs, which has NOTHING to do with the "test pilot structural limit" that is being discussed in this test summary, and which is, at 8 G, the only one of significant enough duration to bleed any real speed on a 9000 lbs aircraft going at 400 MPH...

The "engineering structural limit" is a margin of safety against airframe buffeting, which can create these loads for micro-seconds, long enough to crack the spar... They probably calculate this based on pure metal strenght, not wing lift.

It is just like these mountain-climbing ropes that are stressed to 15 000 lbs: It does not mean the climber weights that much, but for a micro-second a slip can get him there long enough to get close breaking the rope... A microsecond is NOT what is at issue when there is talk of "very rapid energy loss" in a 9000 lbs aircraft going at 400 MPH...

It seems likely to me there is a confusion of similar terms accross the engineering and flight testing profession. In these tests "very rapid energy loss" can only be at 8 G and NOT at 15 G, which would mean more pilot endurance to G than available today for an F-16 pilot at 9 G...

Therefore the nasty speed-bleeding "Corner Speed" here can only be at 8 G, not 15...

Quote, BnZs, (from AH forum): "For instance, take an airplane with known to stall in clean configuration at 100mph IAS, and which is structurally limited to 8gs. The square root of 8 being 2.83, that means the accelerated stall speed for that aircraft *will* be 283 mph IAS, in *clean* configuration. However, the corner speed for the P-51 is usually quoted not in clean configuration, but with one notch of flaps deployed, which will increase lift and lower corner velocity somewhat to...around the same 270mph IAS that has been known for 60 some odd years. Rather anticlimactic outcome, aye?"

-Except that this still correlates very poorly with "very close to the maximum level speed" of the actual 1988 flight test...


Quote, BillSwagger: "I think thats quite a big leap in logic to make given that we don't have the actual test results to refer to, instead we see a summary.
It sounds like they tested these planes using a 1g turn, which makes more sense given the numbers."

-1 G could not be the "Corner Speed"... I think the sentence clearly says the lowest speed the P-51D can pull a 6-7G or a closely extrapolated 8G turn is "VERY close to the maximum level speed", or at least 340-350 MPH at the 10 000 ft. test altitude running at METO, and this could even be with flaps down. But then, as was noted, they didn't go beyond 6-7 Gs owing to airframe age and value... Still, these are EXPERIMENTAL test pilots, so their conclusions are not exactly "guessing"...


Quote, JTD: "The P-51D in Il-2 can take 15 g's so the corner speed would be around 364 mph, if the stall speed was 94 mph again. Since it isn't, as it would be about 110 mph for a P-51 with the above mentioned weight, the corner speed in game is about 426 mph."

-I will re-iterate my point that the P-51D cannot bleed SIGNIFICANT amounts of speed at 15 Gs, since, for one, these Gs could hardly be generated by the strenght of the pilot at the required speeds: VMax: 20 lbs-G stick force, or (20 lbs X 15: 300 lbs...), and also the pilot could not withstand these 15 Gs for long enough to slow down his airplane in any way worth talking about... This is simply not part of the flight enveloppe...

I always assumed "Corner Speed" on the P-51D was at 8G, and not at some engineering structural limit to safeguard against buffeting and vibrations...

Thanks to Kettenhunde for having provided a date (and serial no.) for the Russian turn times of the La-5: It actually answers some of the questions I asked. But there were a LOT more Russian turn times than just for the La-5... Of greater interest to me would be the contentious Me-109G and FW-190A turn times...

Quote, JTD: "There's no increase in turn rate mentioned, he says he managed to turn inside the other guy. That could be a reduction in the turning radius. Also, no mention of the speed involved."

-That is bull. He says he gradually gained by decreasing the throttle in FRONT of a TAILING and GAINING aircraft, after a large number of consecutive 360s on the deck, and that tailing aircraft STOPPED gaining and started losing as a result of his decreasing the throttle at high prop pitch-flaps down: That is an increase in turn rate no matter how you twist it: He is NOT just cutting accross the circle: Pulling off the power made him gain in turn rate, period, regardless of what the radius is...

Quote, Kettenhunde: "So how exactly does the prop pull the plane "out" of the turn if the thrust vector is inward?
Where exactly does the "nose" of a plane start?"

-The nose being straight, it ALWAYS points OUT of the turn, and that forward point is where the thrust comes from... Pretty obvious...

As for where the nose start, I always consider the leading edge of the wing the most significant part: Prop-to-leading edge is the most obvious difference between in-line engines and radial engines... Hence the big surprise when a switchover is made, even compared to the weight difference...

Quote, Kettenhunde: "And how is a 19 seconds for a 360 sustained level turn a tremendous boost over the same 19 seconds for the same thing? That would be LaGG-3 vs. La-5, which essentially had the same sustained turn performance."

-ON PAPER I"ll bet they did... See the La-5 development history for a touch of reality...

As for the Ki-100, it was considered capable by Japanese pilots of taking on and winning against THREE Ki-84s... And at least for that I DO have the reference article if you want... I will bet the engineers did not calculate that in advance, now, did they? Or why would they have not put this radial engine in there back in 1943, when it was already available?

Still hoping for these P-51D actual 8G turn tests...



Gaston

JtD
12-27-2009, 03:40 PM
Hm, you fail to assign the proper quotes to the proper posters. Matches the quality of your statements to 100%, but still, this is where I draw a line. I'm not willing to discuss this any further.

Kettenhunde
12-27-2009, 03:42 PM
Quote, Kettenhunde:

I think you have made a mistake. I have no memory of ever saying any of that.


Russian turn times of the La-5

The VVS combat turn was not a sustained level turn so the times are not applicable to sustained turn performance.

It was what we call a chandelle.

http://en.wikipedia.org/wiki/Chandelle

This is all covered in another thread and I have already explained how to determine sustained level turn performance as well.

Kettenhunde
12-27-2009, 03:50 PM
So in effect, their comment about "Corner Speed being VERY close to Maximum level speed is a CALCULATED deduction, not something they actually tested... This seems odd and unlikely, given that it defeats their whole purpose of verifying what was not apparently clear to them, and thus worth the whole enormous trouble to have a test done in 1988...

No you have just misunderstood the comment. It is very true in the context of what these Gentleman are saying.

These gentlemen operate real airplanes and speaking from Vmax at maximum continuous at their current ratings, they are correct.

You on the other hand are looking at Vmax at some emergency rating and thinking that is where the airplane normally operates or is flown.

8G BTW comes from the F-51 manual from IIRC, 1951. It is applicable to a P51 series weighing 8000lbs or less. If you correctly apply the same chart for a WWII P-51, it comes out to ~6 G's. The formula is in the legend of the chart.

The use of any degree of flap at 8G is pure fantasy.

Good Luck Gaston.

All the best,

Crumpp

M_Gunz
12-27-2009, 05:26 PM
Originally posted by Kettenhunde:
If we go faster than Va, we can break our airplane before we stall it. The fighter with the higher velocity Va holds an advantage.

It is usually defined as beginning at the damage load factor (~6G's) so that we do not risk damage to the airframe.

I take the view that the pilots could not take more than the planes. IIRC that is one of the things that defined
aerial combat in WWII, that the men and the machines were the closest to equal in that era.


Airframe damage has a very small chance of being non-fatal to the aircraft whereas airframe failure is always fatal.

I've read that Tom McGuire had often brought his planes back in tweaked condition and may have gone past limits
in his last flight.

I had forgotten about Maneuver Speed. Crank a P-51 up near full speed and pull the stick back full should result
in a broken airplane. I knew there was something definitely wrong with that quote about Corner near top speed!

JtD
12-28-2009, 04:34 AM
Originally posted by M_Gunz:

I knew there was something definitely wrong with that quote about Corner near top speed!

It could be an IAS-TAS conversion thing. 270 8g stall IAS is like 325 TAS at 3000 meters or 380 at 6000. Eventually you can make it true for any speed, just go high enough.

M_Gunz
12-28-2009, 11:18 AM
Go higher and your turn radius gets wider for the same IAS turn, the G's are less, lift is by IAS not TAS.

BillSwagger
12-28-2009, 03:45 PM
Originally posted by Gaston444:
Quote, BillSwagger: "I think thats quite a big leap in logic to make given that we don't have the actual test results to refer to, instead we see a summary.
It sounds like they tested these planes using a 1g turn, which makes more sense given the numbers."

-1 G could not be the "Corner Speed"... I think the sentence clearly says the lowest speed the P-51D can pull a 6-7G or a closely extrapolated 8G turn is "VERY close to the maximum level speed", or at least 340-350 MPH at the 10 000 ft. test altitude running at METO, and this could even be with flaps down. But then, as was noted, they didn't go beyond 6-7 Gs owing to airframe age and value... Still, these are EXPERIMENTAL test pilots, so their conclusions are not exactly "guessing"...




It says in the beginning of the "summary" that they held the planes with in a 6 G threshold. Don't quote me, but i think most planes of the era couldn't exceed far beyond that before structural damage or failure.

More importantly, Gaston, I might offer that each article that you are pointing to has a different frame of reference. Not that its bad information, but I think it makes more sense to do the math and figure it out that way, instead of looking at various sources and making an attempt to guess or summarize what this planes corner velocity was.

One could even say that a planes corner velocity is in direct relation to how well the plane is piloted, mathematically speaking i think you can talk more concretely about what that number is.



Bill

M_Gunz
12-28-2009, 04:07 PM
I haven't read about a 1 G turn here since Josf brought that one up.

Kettenhunde
12-28-2009, 09:24 PM
I've read that Tom McGuire had often brought his planes back in tweaked condition and may have gone past limits in his last flight.

This certainly occurred. One of the things any mechanic will check in a pre-buy is the plumb of the airframe.

Bent airplanes are a real possibility and sometimes a motivating factor for the sale.

Bent airplanes are a very dangerous possibility too. The limits apply to one axis and if the airframe is damaged, those limits are further reduced.

What would normally be a gentle maneuver that the airframe easily managed before now causes failure and collapse.

In wartime we hear of the stories of the few who successfully gambled and got away with it. We do not hear from those who gambled and lost.

Kettenhunde
12-28-2009, 09:34 PM
a 1 G turn

I take the view that the pilots could not take more than the planes. IIRC that is one of the things that defined aerial combat in WWII, that the men and the machines were the closest to equal in that era.

Often the pilot goes unconscious before the airframe overloads due to rapid onset Gz accelerations.

That is why instabilities and force reversals were so dangerous. With the instability, he can load the airframe very rapidly. Rapid enough to cause unconsciousness. If the pilot goes unconscious, he cannot provide the push force required to slow/stop the load factor accelerations and will die.

http://aeromedical.org/Articles/g-loc.html

Gaston444
12-29-2009, 05:23 AM
Quote, Kettenhunde: "8G BTW comes from the F-51 manual from IIRC, 1951. It is applicable to a P51 series weighing 8000lbs or less. If you correctly apply the same chart for a WWII P-51, it comes out to ~6 G's. The formula is in the legend of the chart."

-Thanks for this clarification.

I'll sum up the general impression these 1988 actual tests left me with: Unsustained speed maximum-rate 6 G turns in the P-51D, and several other US fighters like the P-47D, are at their highest peak in /second at a surprisingly close speed to the maximum level speed... Since piston-engine acceleration is poor at these high speeds, the speed decays very rapidly at the maximum WWII-corrected 6 G: Just like the report summary says...

On the other hand, combat accounts repeatedly make reference to a flaps-down/high prop pitch/low throttle "trick" to radically increase the sustained very low-speed turn rate of the Merlin P-51. Decreasing the throttle futher INCREASES the turn rate further, and the Me-109G-6 with Gondolas can also benefit in this way by lowering the speed to what a Finnish ace fighter-pilot estimated as a sustained low-speed turn rate "peak" of 260 km/h.

Even at these very low speeds of 160-200 MPH, increasing the P-51D's power does NOT increase the sustained turn rate, but increasing the power above this range is significantly worse for the Merlin P-51 than for the Me-109G, a trend that surely reverses itself at some point, given the well-accepted (and combat-account verified) superiority of the P-51D in turn rate, sustained or not, well above 300-350 MPH.

The unsustained higher-speed Turn rate "peak" for the P-51D could be as high as 350 MPH or even 370 MPH, and in combat accounts the turn superiority of the Merlin P-51 to the Me-109G-6 is quite large from 350 to 400 MPH or even 420 MPH. At this band of speeds (say 320-420), the P-51 is among the best maneuvering fighters of WWII, if not the best, but the control-heavy non-metal elevators are about to reach the pilot's limits... (They were changed to metal very late in 1945, around April)

Somewhere above 420 MPH, the fabric-elevator Merlin P-51 seems to abruptly develop very poor elevators, I think because the limits of pilot strenght are reached. Here, there are SEVERAL accounts of the Me-109G-6 having a slightly superior (tail-heavy trim likely) dive pull-out performance after a long dive: "We were locked in the dive at 500 MPH. To my surprise, he (a Me-109G) pulled out of it first"... The P-38L is also said to pull-out better at these speeds, so that "after a high speed dive at low altitudes, the P-38L often reaches the top of its pull-out loop directly above the chasing P-51D, typically just at the moment the P-51D finally BEGINS its pull-out".

To me, this likely implies a better available unsustained turn rate at these high speeds for both the P-38L and, to a lesser extent, the Me-109G if tail-heavy trimmed. (North American were very impressed with the Me-109G's moveable tailplane and pronounced it superior to their P-51's trim tabs: The concept thus went on to the F-86)

This is the convoluted summary of what I have observed so far, and it seems to me the range of speeds between 200-300 MPH is around where you would want to keep turnfighting a well-flown Merlin P-51, in a Me-109G at least...

If the minimum speed for pulling unsustained 6 G turns(WWII corrected) for the P-51D is really at or around 270 MPH, then drastically lowering the throttle in sustained turns after several LEVEL 360s cannot ever be an advantage because you are already at, or more than likely below, 270 MPH then: I'm sure that in fact it WAS an advantage for the P-51D to lower the throttle even below 270 MPH, if no diving was available...

This is where I think the longer nose could play a role in "pulling out of the turn", imposing a lower speed and thus a lower power than available to a radial engine for the same turn rate; said radial engine would therefore gain in the turn by greater speed and power.

This would explain some of the radical superiority of the Ki-100 to the Ki-61: The Ki-100 could outmaneuver and win alone against 3 of the much faster Ki-84s quite regularly (the Ki-100 always won one-on-one vs the Ki-84 immediately), and repeat the feat when all the pilots switched aircrafts... Not such thing with any variant of the Ki-61... (Note the earlier short-nosed ki-61 (a,b,c) were the only really "useable" Ki-61s, the "d" being a sort of overweight dud, and the short-nosed Ki-61s were in fact a touch LIGHTER than the Ki-100: 7650 lbs vs 7705 lbs...)

So if it is beneficial to a P-51D, in a turnfight against a Me-109G-6, to retain FULL power after several consecutive 360s on the deck, I would like to see the flight-test date evidence of that with-flaps 270 MPH 6 G Corner Speed...

Gaston

AndyJWest
12-29-2009, 09:14 AM
This is where I think the longer nose could play a role in "pulling out of the turn", imposing a lower speed and thus a lower power than available to a radial engine for the same turn rate; said radial engine would therefore gain in the turn by greater speed and power.

Thrust is measured as a vector. It has a direction and a magnitude. Whether it is 'pulling' or 'pushing' is meaningless.

ImpStarDuece
12-29-2009, 03:57 PM
Originally posted by Gaston444:
This would explain some of the radical superiority of the Ki-100 to the Ki-61

What would also explain it is the fact that the Ki-100 gained better than 25% in terms of power over the Ki-61, while at the same time gaining less than 1% in terms of weight. It was also turbocharged, so it maintained its power better through altitude.

In comparison, the basic Spitfire Mk IX was only 17.5% more powerful than the basic Mk V, but gained about 11% in weight.


North American were very impressed with the Me-109G's moveable tailplane and pronounced it superior to their P-51's trim tabs: The concept thus went on to the F-86

:choke:

Can you provide a picture of a -109G "movable tailplane" please?

And then maybe go do some research on the Miles M.52?

R_Target
12-29-2009, 08:28 PM
Three Ki-100 prototypes were equipped with a turbocharger. None flew operations as they were still being tested at the end of the war. Production was to start in September '45.

M_Gunz
12-30-2009, 02:41 AM
F-86 did not get the all-flying tail until after it was shown effective on the X-1 research.
That had D1ck to do with the 109 trim system. Is it time for the F-86 vs MiG-15 doghouse charts?

JtD
12-30-2009, 06:59 AM
Originally posted by M_Gunz:
Go higher and your turn radius gets wider for the same IAS turn, the G's are less, lift is by IAS not TAS.

Hi there, same way the 1g stall speed remains the same IAS over altitude the 8g stall will. You're right that the turn changes - at high altitude you fly a larger turn at higher speed -, but the g/stall speed relation doesn't.

M_Gunz
12-30-2009, 12:57 PM
Originally posted by JtD:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by M_Gunz:
Go higher and your turn radius gets wider for the same IAS turn, the G's are less, lift is by IAS not TAS.

Hi there, same way the 1g stall speed remains the same IAS over altitude the 8g stall will. You're right that the turn changes - at high altitude you fly a larger turn at higher speed -, but the g/stall speed relation doesn't. </div></BLOCKQUOTE>

No, it doesn't. But at full TAS you can pick an alt where the IAS will max out at some G's or less.
Are V-speeds by TAS? I don't think so! AFAIK Stall is a V-speed and it sure doesn't!

I looked at the Gaston-post at page-top (Ignored post by Gaston444 posted Tue December 29 2009 04:23) and saw so much
apples to oranges to coconuts to grapes (all carefully picked) comparisons that he could set up a fresh fruit stand.

Gaston444
12-30-2009, 07:18 PM
Quote, AndyJWest: "Thrust is measured as a vector. It has a direction and a magnitude. Whether it is 'pulling' or 'pushing' is meaningless."


-Apparently a lot of people assume that, but lifting the propeller nose "up" in a 90 banked turn requires pushing sideways a churning propeller that is about 12' in diameter and is providing the entire thrust to the whole thing...

To say that pushing this churning propeller nose sideways is the same thing as pushing sideways a lightweight nose cone that contains nothing more physically active than a radar, is pushing the relevance of maths theories beyond the breaking point...

Besides, the fact that the center of lift, and the center of gravity, are both far behind the point where thrust is applied, instead of being far in FRONT of it, has implications that requires at the very least a specific set of math formulas. Even then, I would think variables among props, wings and nose and fuselage shapes that are BATHING in the flux of that thrust, which happens to be a SPIRAL, would make even these specific formulas very approximate at best...

In a jet, none of the aircraft's shape components are bathing in the actual engine thrust flux... The fact that the same formulas appear to be indifferently applied to powerful single-engine prop aircrafts or jets indicates to me the greater complexities of prop-airframe interactions are ignored. And why would they not be? Propeller fighters as weapons of war were already receding into the past almost as soon as the war was over...

I'll bet many computer game prop fighters such as the P-47D, FW-190A or the A6M turn much the same right or left... Not so simple in real-life with an actual prop in front...

Gaston

AndyJWest
12-30-2009, 07:57 PM
...the fact that the center of lift, and the center of gravity, are both far behind the point where thrust is applied, instead of being far in FRONT of it, has implications that requires at the very least a specific set of math formulas

Um, what are these formulas then, Gaston444?

As for 'computer game prop fighters' turning the same in either direction. I suggest you try this for yourself in IL-2. Though I don't suppose the spiral-thrust factor is modelled, P-factor and gyroscopic effects surely are.

M_Gunz
12-31-2009, 06:20 AM
I'd like to see those formulae myself! Especially from someone who thinks the FW-190 is a low speed turn fighter!