WW2 fighter turning performance comparisons

[Crumpp]

Hi drgondog,

Thank you for the kind words.

I think you misunderstood what I wrote regarding turn performance. Don't worry it is a difficult concept to grasp but as I said, it is a very powerful fact of aircraft performance. You will begin to see why sustained level turn is just not very important to a fighter designer.

Notice in the development of the radius of turn equation that the weight (W) canceled out of the equation. This is a very important observation since it means that the size of the aircraft has no effect on the radius of turn. Thus, two aircraft flying at the same angle of bank and velocity will make the same radius of turn even if one is 1000 times larger than the other.

Radius of Turn

Turn performance is based on the relationship of power available to power required. In a very simplistic form, wing loading is a reflection of this relationship. However aircraft are a system and not one characteristic. The designers in WWII were very competent and I would even venture to say much more competent in high power piston aircraft design than we are today. There simply is not much of a market for 2000hp single engine aircraft.

Not all aircraft can sustain the same angle of bank at the same velocity. The L/D characteristics of the design play a very important role. In fact all aircraft performance depends on the L/D curve.

For WWII fighter design contemporaries, the differences are a very small portion of the total maneuvering envelope.

In your example, the F-105 simply cannot travel as slow as the Zeke, velocity being the key component to turn radius.

Now the Zeke cannot travel as fast as the F-105 either. So at the higher velocities the F-105 is comfortable maneuvering, the Zeke cannot sustain the same turn performance.

Just as excess power extends into the low velocity realm, it also extends into the high velocity realm. At Vmax, an airplane only has enough power to sustain wings level flight.

In the graph above the red lines represent the radius of turn for any airplane, at 10,20...80 degrees of bank. Keep in mind that the radius of turn equation is universal, therefore this graph is valid for any airplane, from a C-150 to a Boeing 747.

The blue line in the graph is for an airplane with a stall speed of 60 knots in straight and level flight. This line will be different for every airplane of course.

Minimum Radius of Turn

You can confirm this aerodynamic fact easily with the following program:

Gyles AeroDesign - Freeware Turn Radius Calculator

All the best,

Crumpp

[drgondog]

Originally Posted by Crumpp

Hi drgondog,

Thank you for the kind words.

I think you misunderstood what I wrote regarding turn performance. Don't worry it is a difficult concept to grasp but as I said, it is a very powerful fact of aircraft performance. You will begin to see why sustained level turn is just not very important to a fighter designer.



Radius of Turn

Turn performance is based on the relationship of power available to power required. In a very simplistic form, wing loading is a reflection of this relationship. However aircraft are a system and not one characteristic. The designers in WWII were very competent and I would even venture to say much more competent in high power piston aircraft design than we are today. There simply is not much of a market for 2000hp single engine aircraft.

Not all aircraft can sustain the same angle of bank at the same velocity. The L/D characteristics of the design play a very important role. In fact all aircraft performance depends on the L/D curve.

For WWII fighter design contemporaries, the differences are a very small portion of the total maneuvering envelope.

In your example, the F-105 simply cannot travel as slow as the Zeke, velocity being the key component to turn radius.

Now the Zeke cannot travel as fast as the F-105 either. So at the higher velocities the F-105 is comfortable maneuvering, the Zeke cannot sustain the same turn performance.

Just as excess power extends into the low velocity realm, it also extends into the high velocity realm. At Vmax, an airplane only has enough power to sustain wings level flight.





Minimum Radius of Turn

You can confirm this aerodynamic fact easily with the following program:

Gyles AeroDesign - Freeware Turn Radius Calculator

All the best,

Crumpp

Crumpp - I wasn't having a problem grasping the concepts - strictly to the statement and question I posed. Like you I have both the education and the experience behind the stick to agree the points you made.

In my example with the Zeke I was perhaps not clear enough.

The F-105 could in fact fly at 300 kts, and enter a turn with a Zero at three hundred kts, and not be able to keep up in the turn radius no matter how much power is subsequently added by the 105 jock to try to maintain bank angle...

If he continued to try to maintain the turn and the rule of this engagement is a.) do not add any more throttle, and b.) put the engagement on the deck, the 105 will be severely out turned by the Zero.

I would pose the same outcome for a MiG21 and F-105 entering a turning fight on the deck, each entering at 550 kts and let the 105 be able to increase his power to all available as he is faster on the deck. The 105 would be able to enter with the same bank angle but would not be able to sustain it (or lose bank angle/energy less slowly than the MiG).

This is the end of my only rebuttal to a statement that I think you did not mean in the context I parsed it..

As to 'not very important', at low altitude and very little excess energy available to break combat with a fighter with significantly better turn performance....it might be critical.

As to the pilot who knows his ship and understands the strengths of his speed and zoom, then he avoids the circumstances above - and makes it 'less important' -

And to your point a superior pilot (say, in a P-47) on the deck might be able to outfly the inferior pilot in a 109 or 190 in a turn, entering at the same speed and bank angle, and defeat them by being able to skirt closer to the stall - in which case as you pointed out, the turn radius (optimal) was not the critical factor, but the skill of the pilot in the a/c with 'inferior' turn potential performance and his ability to ultimately 'out turn' the better a/c in that manuever.

This is a lot of words for what I thought was a minor point of disagreement for a literal statement I wasn't sure you meant - <smile>

If you meant it, I tip my hat and withdraw from the debate.

Regards,

Bill

[Glider]

I admit that I am with Drgondog on his comments about radius of turn. Some aircraft have lift devices that enable them to reduce the turn radius for a given speed. This must be reflected in the final result somewhere along the line.
Weight surely must also play a part. The heavier plane is going to have a harder time in the turn due to the additional forces in play trying to 'throw' the plane out of the turn, plus of course wing design. I cannot see an F104 staying, say with an F86 in a turn at the same speed and bank, due to the different amount of lift generated by the wing.

Also isn't there a significant danger in looking at this in isolation. For example the roll rate has a major impact on how long it takes to get into a bank for the turn to take place. I have some experience in gliders and I am confident nothing powered could keep up with me in a turn, but my roll rate is shocking and to get into a turn takes an appreciable amount of time compared even to a simple Cessna.

[Crumpp]

The F-105 could in fact fly at 300 kts, and enter a turn with a Zero at three hundred kts, and not be able to keep up in the turn radius no matter how much power is subsequently added by the 105 jock to try to maintain bank angle...

If we are not considering the effects of power then yes, our F-105 would turn exactly the same as our Zeke at 300KEAS at the same angle of bank. It could keep up and match turn performance exactly. There would be no difference in the two aircraft's turning ability.

However power available to power required is the fundamental relationship of aircraft performance. We have to consider the effects of power.

Lets just use EAS so we can simply things by eliminating density effects.

Actually the Zeke is incapable of turning at 300KEAS. In fact it is incapable of even reaching that speed in KEAS in level flight. It does not have the power available. If the pilot attempted to turn at 300Kts he would have to trade altitude for airspeed if he wanted to maintain 300KEAS.

The F-105 would end up above him.

The Zeke could give up energy in the form of airspeed to maintain alitude. As he travels at a slower velocity he will now turn a smaller radius but will have lost energy.

Here we can see the Zeke 52 maximum sustain load factor using TAIC data:



Here is the excel spreadsheet data from the sheet I designed:



Here we can see the P47D-22 using AHT data at combat weight. Notice the curve is very similar to the Zeke’s. However the Zeke can sustain this at a much lower velocity. The P47D-22 however can sustain a turn at 250KEAS of 2.76G's while the Zeke can only sustain 1.5G's at 250KEAS.



Now which would you rather dogfight in? The aircraft that has to give up a large portion of its energy to maneuver or the aircraft that can remain fast and still maneuver?

Speed is life.

All the best,

Crumpp

[Crumpp]

I have some experience in gliders and I am confident nothing powered could keep up with me in a turn,

Certainly it can outturn most "powered" aircraft for a while at least. Your glider has much more power available than a Cessna as long as it exchanging PE for KE to maintain that altitude. It uses it's lightweight and low drag to gain the advantage in Pa. Great example of how L/D characteristics determine performance.

Typical L/D max for a sailplane is ~60:1. Typical L/D max for a Cessna 150 is ~7:1. Your glider is moving 60 feet forward for every foot of altitude lost. The Cessna 150 is moving 7 feet forward for every foot of altitude lost. It takes a lot less energy to move your glider than it does the Cessna.

Hence your glider has more power available in the turn. You will reach a point where you have exchanged all energy available and can no longer maintain that altitude. The Cessna on the otherhand will reach a point it can sustain performance at that altitude as long as it has fuel to convert to KE.

due to the different amount of lift generated by the wing.

This statement bothers me and I just want to clarify your meaning here. Airfoils on different aircraft due generate different amounts of lift. However all of them generate only the amount of lift required for a condition of flight.

It does not matter what airfoil or lift devices you place on a 2000lb aircraft for example. It will always generate only 2000lbs of lift in level flight. In climbing flight our wing will generate less lift than in level flight and in a dive it will generate more lift than in level flight.

For example the roll rate has a major impact on how long it takes to get into a bank

Yes, in fact designers consider roll rate to be much important than level turn ability. All manuvers begin with a roll.

Any aircraft with a significant roll rate advantage can use it to overcome a level turn advantage. Placing the vector of lift below the horizon adds weight directly to thrust based on the angle. Adding thrust to the turn equation directly increases our maximum sustainable load factor.

All the best,

Crumpp

[Crumpp]

Some aircraft have lift devices that enable them to reduce the turn radius

The effects depend on the device in question. Flaps for example, depending on the setting selected will actually reduce turn performance. In the first few degrees the tendancy is too gain more lift benefit than drag penalty. After that first few degrees, the drag penalty increases explosively.

While TE or trainling edge flaps do increase an airfoils usable angle of attack by changing camber, they also increase the angle of incidence. This has the effect of lowering the nose of the aircraft while maintaining the capability to fly at a lower velocity for the same lift production. If we did not have flaps, our body angle at approach velocity would be high enough to obstruct the pilots view of the landing site.

Airfoil lift devices can be divided into two broad catagories. Those that increase camber, and those that energize the boundry layer.

As for the calculations, the effects are acounted for in the forces required.

All the best,

Crumpp

[Crumpp]

Just to clarify on the Zeke/P47 comparision.

Any turn that is below the blue line, the two aircraft will make exactly the same turn and the performance is sustainable.

Any turn above the blue line, the two aircraft will make exactly the same turn but the performance is not sustainable.

So if the Zeke is sustaining performance in an area the P47 cannot sustain the same performance, the P47 can exchange energy if available to match performance up to the stall line. This goes both ways for both aircraft.

Hnece the expression all aircraft at the same angle of bank and velocity will make exactly the same turn.

The graphs only show the thrust limited performance. There is a lift or stall line which is not shown. Niether aircraft can achieve controlled flight if they pass the stall line.

Understand now?

All the best,

Crumpp

[Crumpp]

I wasn't having a problem grasping the concepts

Hi Bill,

I know that you do not have any trouble grasping the concepts. It is just a difficult concept to explain on a BBS over the internet.

I hope my explainations above make the concept I was conveying much clearer.

You are correct that there are situations where turn performance can be decisive. In fact turn performance is much more important in the Jet age due to the differences in thrust producers and power producers behavior in the region of reversed command.

It is an interesting line of discussion IMHO.

All the best,

Crumpp

[Soren]

I agree completely with Crumpp

The pilot is an extremely important factor, but taking away the pilot factor L/D & T/D ratio, lift-loading and power-loading are the most important factors as to how well an a/c turns.

Believe it or not the Me-262 A-1a is actually a very capable turn fighter as long as the speed is kept high, and the extremely low drag of this a/c coupled with its high AR wing & LE slats made sure it possesses a high L/D ratio, which means a much lower drag penalty for the amount of lift produced in aturn than normal - as its pilots explained the Me-262 was very slow to loose speed in a turn, which was very good cause if you did go slow you were in trouble as the acceleration of the jet-engines was very low at low speeds, making for a pathetic turn performance at low speed.

[Soren]

At 540 km/h at a weight of 6,000 kg the Me-262 A-1a will be capable of a 8 G turn, which is more than what the average pilot can take.

Lift: 1.58*21.7*.5*1.225*150^2 = 472503.938 Newtons (N)

472503.938 N = 48181.99 Kgf

48181.99 kgf / 6000 kg = 8.03033167

G-force at Clmax at 540 km/h: 8.03

[Mike Williams]

Hey Mike - as a cynic I might have suggested a couple of months back that the prime off line instructions to the Navy pilots conducting the tests "Don't come back with a conclusion that the 51 is superior in any way" - which is why the Patuxent River tests are not accompanied by Turn and acceleration comparisons at various speeds and altitudes - lol - but definitely accompanied by statements that the F4U out turned, accelerated and climbed better –

Hello Bill:

It would be natural and understandable to have misgivings about trials where the Navy compared an Army aircraft against their own or vice versa. After reexamining the Evaluation and Comparison Trials of the P-51B and F4U-1 I don’t believe the findings were too terribly politicized if one assumes that the Navy was interested in comparing the P-51 against the best performance possible from standard production operational F4U’s as well as F4U’s that might be coming into service in the not too distant future.

Allow me to explain why I feel that this particular comparison is at least a reasonable interpretation of how the P-51 and F4U compared. The Navy utilized three aircraft in the trials, namely P-51B No. 37050, F4U-1 02390 and F4U-1A No. 17930.

Firstly, let’s check the performance of the P-51 obtained by the Navy and compare it against other sources.

Level Speeds:

P-51B 37050 (Navy, Patuxent River): 358 mph at SL and 450 mph at 29,200’ using 67” Hg, 3000 RPM.

P-51B No. 43-6883 (Army, Wright Field): 370 mph at SL and 442 mph at 29,400’.

P-51B FX953 (UK, Boscombe Down): 360 mph at SL and 450 mph at 28,000 ft.

See also P-51 Tactical Planning Characteristics & Performance Chart and Aircraft Data Sheet for Mustang III (P-51B)

Thus it can be seen that in this respect at least, the Navy’s findings are in good agreement with other flight trials and data sheets.

Climb:

P-51B 37050 (Navy, Patuxent River) 9,423/9,100 lbs.: F4U’s are 750 – 1,000 ft/min superior with the P-51B loaded to 9,423 lbs and “superior in climb to 20,000 feet, and the P-51B superior above that altitude” with the P-51B loaded to 9,100 lbs..

P-51B No. 43-6883 (Army, Wright Field) 9,205 lbs.: 3,450 ft/min at 13,800 feet

P-51B FX953 (UK, Boscombe Down) 9,200 lbs.: 3,610 ft/min at 10,600 feet

Unfortunately the Navy didn’t provide actual rate of climb figures for the P-51B, rather just the comparative figures as stated above.

The Navy tested two F4U’s during the comparison trials. F4U-1A No. 17930 is described as “a standard production raised cabin airplane, with a surface finish in rather poor condition, but with the tail hook removed. It is considered to have been in a drag condition representative of production airplanes after moderate service.” The report also notes that “F4U-1A No. 17930 was flown at the standard war emergency rating of 60” at 2700 RPM, with water injection.” The level speed results obtained, along with those of another F4U-1 tested by the Navy at the same power settings for comparison, are as follows:

Level speeds:

F4U-1 No. 17930: 365 mph at SL, 431 mph at 20,300 feet. 60” MAP, 2700 RPM. 31.5” carburetor impact pressure setting. (without tailhook & opening faired.)

F4U-1 No. 50070: 364 mph at SL, 421 mph at 19,850 feet. 60” MAP, 2700 RPM 31.5” carburetor impact pressure setting. (with tailhook)

In contrast the Bureau of Aeronautics-Navy Dept. Airplane Characteristics & Performance data sheet lists the level speeds of the F4U-1 as 359 mph at SL and 417 mph at 19,900 feet using water injection.

It can thus be concluded that F4U-1 17930’s condition while not exactly standard, is close to standard and its performance a bit stronger than would be typical of production models.

The other F4U-1 tested is certainly not typical of those F4U’s entering service at the time of the trials. It’s important to note that the Navy doesn’t try to pass it off as standard either. “F4U No. 02390 was a standard low-cabin production airplane, in a drag condition representative of that to be expected in the F4U-4 airplane as a Marine land-based fighter. … The principle changes included sealing and fairing the wing fold hinge line, removal of the tail hook, carefully fitted cowling, and a faired and smoothed, but not polished, skin. The total speed gain, as a result of drag reduction alone, in this airplane is estimated to be 8 mph at the airplane upper critical altitude.” “F4U-1 No. 02390 was flown at a special war emergency power rating of 65” manifold pressure and 2700 RPM, with water injection at an increased water flow rate.” One of the conclusions of the report on F4U-1 No 50030, dated August 2, 1945 was “A combat power rating in excess of 60” manifold pressure is considered to be impractical for general use when atmospheric temperatures are in excess of NACA standard.”

Climb:
F4U-1A No. 17930 max climb = 3210 ft/min at SL (12,162 lbs.)
F4U-1 No. 50070 max climb = 3460 ft/min at SL (12,162 lbs.)
F4U-1 No. 02390 unknown but stated as superior to the P-51B at various loadings except above 25,000’.

In contrast the F4U-1’s climb rate as shown on the Airplane Characteristics & Performance sheet is 2890 ft/min at SL at 12039 lbs and using water injection. It appears that the Navy is on less solid ground with their conclusions regarding climb comparisons of the F4U and P-51B.

Was the Navy trying to mislead their intended readership based on what we know so far? With respect to level speed performance, I don’t think so, but including F4U No. 02390 in the trial does muddy things up for us in this day and age if we are just reading their conclusions, looking at the charts and not examining the details. It does appear to me, however, they were stretching the truth a bit with respect to their conclusions regarding climb. Sure, the report is probably somewhat biased but in the end I believe the F4U served the Navy well and was probably a better choice for them just as the P-51 was the better choice for the Army Air Force.

Frankly the report only touches on maneuverability and response and apparently is little more than pilot’s impressions. It falls far short of "turn and acceleration comparisons at various speeds and altitudes" (well, to be fair, no one was doing that at the time) or full fledged tactical comparison trials such as those conducted by Eglin or AFDU in the UK. I’d agree with you that the report’s conclusions in this respect were a bit of a stretch. A USAAF report comparing an F4U and an Allison engined P-51 provides an interesting counterpoint.

There must be a good reason why most test centers of the period used comparative, head to head testing, for performance variables such as turn, acceleration, roll, etc. Interestingly the Navy did occasionally test and quantify roll rates such as that found in this report on the F4U and this report on the F6F. Quibbles with the report analyzed here aside, on the whole I find the Navy performance testing, especially that carried out at Patuxent River, to be very thorough, professional and the equal to Wright Field or A&AEE in the UK.

I suppose this ramble is not terribly on topic to the overall thrust of this thread but it is intended as a reply to Bill’s post and it’s what is interesting to me at this time and hopefully some of you too. What material I’ve found on WWII fighter turning comparisons can be found at the link in my signature, some reports and diagrams of which have already been linked to in this thread.

[Glider]

Originally Posted by Crumpp

Typical L/D max for a sailplane is ~60:1.

I do wish the ones that I could afford to buy, had been that good

[Crumpp]

I do wish the ones that I could afford to buy, had been that good

I misread the L/D characteristics. 60:1 is a typical racing sailplane. 43:1 is a typical high performance sailplane L/D max. They are not cheap for sure. Especially since the utility of a glider is rather small. "Fun toy" is about as far it gets IMHO when considering Glider ownership. Shame as you really need some decent piloting skills to get the most out of them.

I am considering installing a tow on one of my aircraft to get some of the "cost of flying" back.

The point still stands:

Certainly it can outturn most "powered" aircraft for a while at least. Your glider has much more power available than a Cessna as long as it exchanging PE for KE to maintain that altitude. It uses it's lightweight and low drag to gain the advantage in Pa. Great example of how L/D characteristics determine performance.

Typical L/D max for a sailplane is ~60:1. Typical L/D max for a Cessna 150 is ~7:1. Your glider is moving 60 feet forward for every foot of altitude lost. The Cessna 150 is moving 7 feet forward for every foot of altitude lost. It takes a lot less energy to move your glider than it does the Cessna.

Hence your glider has more power available in the turn. You will reach a point where you have exchanged all energy available and can no longer maintain that altitude. The Cessna on the otherhand will reach a point it can sustain performance at that altitude as long as it has fuel to convert to KE.

All the best,

Crumpp

[drgondog]

Originally Posted by Mike Williams

Hello Bill:

It would be natural and understandable to have misgivings about trials where the Navy compared an Army aircraft against their own or vice versa. After reexamining the Evaluation and Comparison Trials of the P-51B and F4U-1 I don’t believe the findings were too terribly politicized if one assumes that the Navy was interested in comparing the P-51 against the best performance possible from standard production operational F4U’s as well as F4U’s that might be coming into service in the not too distant future.

Allow me to explain why I feel that this particular comparison is at least a reasonable interpretation of how the P-51 and F4U compared. The Navy utilized three aircraft in the trials, namely P-51B No. 37050, F4U-1 02390 and F4U-1A No. 17930.

Firstly, let’s check the performance of the P-51 obtained by the Navy and compare it against other sources.

Level Speeds:

P-51B 37050 (Navy, Patuxent River): 358 mph at SL and 450 mph at 29,200’ using 67” Hg, 3000 RPM.

P-51B No. 43-6883 (Army, Wright Field): 370 mph at SL and 442 mph at 29,400’.

P-51B FX953 (UK, Boscombe Down): 360 mph at SL and 450 mph at 28,000 ft.

See also P-51 Tactical Planning Characteristics & Performance Chart and Aircraft Data Sheet for Mustang III (P-51B)

Thus it can be seen that in this respect at least, the Navy’s findings are in good agreement with other flight trials and data sheets.

Climb:

P-51B 37050 (Navy, Patuxent River) 9,423/9,100 lbs.: F4U’s are 750 – 1,000 ft/min superior with the P-51B loaded to 9,423 lbs and “superior in climb to 20,000 feet, and the P-51B superior above that altitude” with the P-51B loaded to 9,100 lbs..

P-51B No. 43-6883 (Army, Wright Field) 9,205 lbs.: 3,450 ft/min at 13,800 feet

P-51B FX953 (UK, Boscombe Down) 9,200 lbs.: 3,610 ft/min at 10,600 feet

Unfortunately the Navy didn’t provide actual rate of climb figures for the P-51B, rather just the comparative figures as stated above.

The Navy tested two F4U’s during the comparison trials. F4U-1A No. 17930 is described as “a standard production raised cabin airplane, with a surface finish in rather poor condition, but with the tail hook removed. It is considered to have been in a drag condition representative of production airplanes after moderate service.” The report also notes that “F4U-1A No. 17930 was flown at the standard war emergency rating of 60” at 2700 RPM, with water injection.” The level speed results obtained, along with those of another F4U-1 tested by the Navy at the same power settings for comparison, are as follows:

Level speeds:

F4U-1 No. 17930: 365 mph at SL, 431 mph at 20,300 feet. 60” MAP, 2700 RPM. 31.5” carburetor impact pressure setting. (without tailhook & opening faired.)

F4U-1 No. 50070: 364 mph at SL, 421 mph at 19,850 feet. 60” MAP, 2700 RPM 31.5” carburetor impact pressure setting. (with tailhook)

In contrast the Bureau of Aeronautics-Navy Dept. Airplane Characteristics & Performance data sheet lists the level speeds of the F4U-1 as 359 mph at SL and 417 mph at 19,900 feet using water injection.

It can thus be concluded that F4U-1 17930’s condition while not exactly standard, is close to standard and its performance a bit stronger than would be typical of production models.

The other F4U-1 tested is certainly not typical of those F4U’s entering service at the time of the trials. It’s important to note that the Navy doesn’t try to pass it off as standard either. “F4U No. 02390 was a standard low-cabin production airplane, in a drag condition representative of that to be expected in the F4U-4 airplane as a Marine land-based fighter. … The principle changes included sealing and fairing the wing fold hinge line, removal of the tail hook, carefully fitted cowling, and a faired and smoothed, but not polished, skin. The total speed gain, as a result of drag reduction alone, in this airplane is estimated to be 8 mph at the airplane upper critical altitude.” “F4U-1 No. 02390 was flown at a special war emergency power rating of 65” manifold pressure and 2700 RPM, with water injection at an increased water flow rate.” One of the conclusions of the report on F4U-1 No 50030, dated August 2, 1945 was “A combat power rating in excess of 60” manifold pressure is considered to be impractical for general use when atmospheric temperatures are in excess of NACA standard.”

Climb:
F4U-1A No. 17930 max climb = 3210 ft/min at SL (12,162 lbs.)
F4U-1 No. 50070 max climb = 3460 ft/min at SL (12,162 lbs.)
F4U-1 No. 02390 unknown but stated as superior to the P-51B at various loadings except above 25,000’.

In contrast the F4U-1’s climb rate as shown on the Airplane Characteristics & Performance sheet is 2890 ft/min at SL at 12039 lbs and using water injection. It appears that the Navy is on less solid ground with their conclusions regarding climb comparisons of the F4U and P-51B.

Was the Navy trying to mislead their intended readership based on what we know so far? With respect to level speed performance, I don’t think so, but including F4U No. 02390 in the trial does muddy things up for us in this day and age if we are just reading their conclusions, looking at the charts and not examining the details. It does appear to me, however, they were stretching the truth a bit with respect to their conclusions regarding climb. Sure, the report is probably somewhat biased but in the end I believe the F4U served the Navy well and was probably a better choice for them just as the P-51 was the better choice for the Army Air Force.

Frankly the report only touches on maneuverability and response and apparently is little more than pilot’s impressions. It falls far short of "turn and acceleration comparisons at various speeds and altitudes" (well, to be fair, no one was doing that at the time) or full fledged tactical comparison trials such as those conducted by Eglin or AFDU in the UK. I’d agree with you that the report’s conclusions in this respect were a bit of a stretch. A USAAF report comparing an F4U and an Allison engined P-51 provides an interesting counterpoint.

There must be a good reason why most test centers of the period used comparative, head to head testing, for performance variables such as turn, acceleration, roll, etc. Interestingly the Navy did occasionally test and quantify roll rates such as that found in this report on the F4U and this report on the F6F. Quibbles with the report analyzed here aside, on the whole I find the Navy performance testing, especially that carried out at Patuxent River, to be very thorough, professional and the equal to Wright Field or A&AEE in the UK.

I suppose this ramble is not terribly on topic to the overall thrust of this thread but it is intended as a reply to Bill’s post and it’s what is interesting to me at this time and hopefully some of you too. What material I’ve found on WWII fighter turning comparisons can be found at the link in my signature, some reports and diagrams of which have already been linked to in this thread.

Mike - thx for the details.

Actually I am not a Mustang bigot with respect to performance and the F4U is probably the best fighter we put into combat in WWII when you look at every possible role. I wish it had been in Europe in 1943.

PS - I'm waiting for last detail from 357 guys on the 24 April mission - then I will send it your way.

[drgondog]

Originally Posted by Crumpp

Hi Bill,

I know that you do not have any trouble grasping the concepts. It is just a difficult concept to explain on a BBS over the internet.

I hope my explainations above make the concept I was conveying much clearer.

You are correct that there are situations where turn performance can be decisive. In fact turn performance is much more important in the Jet age due to the differences in thrust producers and power producers behavior in the region of reversed command.

It is an interesting line of discussion IMHO.

All the best,

Crumpp

Crumpp - I thought you explained it well. You actually had me digging up old (very old) performance text books to refresh my thinking. I had some minor points to debate but wasn't worth quibbling over.

Regards,

Bill