# P-40 Warhawk/Kittyhawk



## archerynut (Feb 24, 2009)

ever since i can remember, i have had a spot for this plane somewhere. that big intake on the bottom, the sharks mouth, it all goes together to make a plane that meant business more than anything else. all over the internet, its talked about as being one of the toughest, most reliable of the early war fighters. along its design history is talk of having been equipped with a rolls royce/packard merlin. this engine, in most cases, seemed to "make" the plane it was installed in. so why did they short change the p-40 by equipping it with the Allison instead? was it a matter of logistics or just convenience? with the merlin, it could have been a truly amazing airplane that would have performed brilliantly at ANY altitude that combat would have taken place. to look back at its combat record, i can't help but think the quality of the pilot is what made the p-40 what it is thought of being today. they had the training and they "had right on their side"!


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## davebender (Feb 24, 2009)

> why did they short change the p-40 by equipping it with the Allison instead?


Why was ANY American aircraft equipped with the Allison rather than the superior RR Merlin engine?


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## tomo pauk (Feb 24, 2009)

Allison was American engine. So, it was just natural to install it into US airframes.

I'd love to see what a R-2600 could do in the P-36 offspring, rather then the Merlin in the same plane.


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## Colin1 (Feb 24, 2009)

archerynut said:


> ...I have had a spot for this plane...
> 
> ...along its design history is talk of having been equipped with a rolls royce packard merlin...
> 
> ...


The problem with 'spots' is the tendency to look at the object of your affection through rose-tints

The Merlin _was_ fitted, in the P-40F and L versions, with the L making vigorous attempts to shed weight. All of this certainly improved the P-40 but I would stop short at calling it an 'amazing aeroplane that would have performed brilliantly at any altitude'. By 1943, the P-40 was an old, heavy design, outmoded by more modern a/c that more accurately addressed the new requirements of aerial warfare. The P-40 stayed in production far longer than it should have done largely because it was cheap, not because it was amazing or brilliant.

The P-40 wasn't short-changed, the Allison was the perfect engine to address the requirements that the a/c was designed for - low-level engagements. The Allison was a good low altitude engine at the beginning of the war and returned with a vengeance at the end of the war in its -119 configuration to become a good high altitude engine.

You're not alone in your affection for the P-40, it was an honest airplane and it was there when it was needed.


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## tomo pauk (Feb 24, 2009)

... sort of American Hurricane perhaps


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## davebender (Feb 24, 2009)

Will it fit? The R2600 radial is relatively large and heavy.

*R1830 twin radial.*
48.03 in diameter.
1,250 lb dry weight.

*R2600 twin radial.*
55 in diameter.
2,045 lb dry weight.

*Allison V1710 liquid cooled V12.*
41.18 in height.
1,445 lb dry weight.


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## tomo pauk (Feb 24, 2009)

Russians managed to re-engine the LaGG-3 with a heavier and bulkier engine in order to get the La-5; plus the one extra cannon weighted more then 2 Skash MGs that got removed.
Dry weight: M-105: 620 kg (1,365 lb) (LaGG-3)
Dry weight: M-82-112 model: 860 kg (1,894 Ib) (La-5)
Japanese have also went through similar trouble to re-engine the Ki-61 to produce Ki-100.

It would require some thinkering to mount the R-2600 in the P-36 airframe, but that's why we have engineers. The removal of engine MGs and the sinchronisation gear would help too.


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## TheMustangRider (Feb 24, 2009)

Another factor that led to the limited production of P-40Fs (around 1300 units) was that by the time the Packard V-1650-1 engine had already been prioritized for use in the P-51 Mustang.


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## delcyros (Feb 24, 2009)

tomo pauk said:


> It would require some thinkering to mount the R-2600 in the P-36 airframe, but that's why we have engineers. The removal of engine MGs and the sinchronisation gear would help too.



The R-2600 was about 800 lbs heavier than the r-1830 and 6.5" larger in diameter. With the assoiated structural enforcements we do talk about a netto weight increase in the area of 1500 +-100 lbs. in total for the P-36 with r-2600. More serious are the unadressed cg-shift fwd., which would tend to make the P-36 very nose heavy. It requires basically a complete new design of the fuselage. 
The P-36 would then weight in loaded over 7.500 lbs! Wingload would increase by 25% from 25.3 to ~31.6lbs/ft^2. Takeoff and landing speed inreases, handling will be more difficult with longer turn times and more severe torque effects during taxiing.
On the plus side You will have 1600hp instead of 1050/1200hp aviable.
Power/weight ratios would be basically unchanged due to the increased weight of the r-2600 installation.
Frontal area and wetted area are now significantly larger and thus more drag will be generated by the same airframe. It´s difficult to project a top speed but judging from France´s disappointing experiences with the Br-695 series and these engine changes, I doubt that You would see drastically improved performances unless a major aerodynamic clean up takes place. You end up with a plane which has basically the same performance but is more difficult to handle and consumes more fuel (=less range).


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## tomo pauk (Feb 24, 2009)

Okay, 
The R-2600 weights some 360kg more then the R-1830. Now we need to reduce that difference, since the hull MGs, their ammo and the sinchro gear are deleted. My guess is that we save around 100 kg, so the difference is about 260 kg. Much smaller then proposed 680kg, and very much close to the LaGG-3/La-5 conversion. 

Of course, we do have the added weight that is not at the centre of gravity of plane. Luckily, the added weight is pretty close to the CoG, so we'll compensate it by adding removing lighter stuff* aft of the pilot seat.
My guesstimate is that the plane would be 25-30% heavier then P-36 (with additional enforcements, wing guns engine added weight), but with 50-60% more HP.


*armor, radio, fuel etc.


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## delcyros (Feb 24, 2009)

The added weight is IN FRONT OF THE COG. Removing weight from BEHIND OF THE COG does make things worser! You need to elongate the hull and install dead weights (armour?) as far aft as possible to counter this. Or You move the wing forward.
Remember also that it´s engine dry weight, not netto weight increases. The support frames needs to be enforced to cope with the heavier loads and torque effects produced by the larger engine, too.


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## davebender (Feb 24, 2009)

I think the 30L R1830 engine could have been developed further. With a better supercharger and other improvements you could probably achieve 1,400 hp. In addition you clean up the P36 airframe to make it more streamlined. Together these improvements should push the top speed up to about 375mph. This keeps the P36 competitive through 1942.


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## Elvis (Feb 24, 2009)

archerynut said:


> ever since i can remember, i have had a spot for this plane somewhere. that big intake on the bottom, the sharks mouth, it all goes together to make a plane that meant business more than anything else...so why did they short change the p-40 by equipping it with the Allison instead? was it a matter of logistics or just convenience?


Because during the war, we were pumping as much equipment off the assembly lines as quickly as possible, thus every single piece of equipment was strictly prioritized.
The Merlin's went into the P-51, because it was just a better and faster airplane that could pack a heavier punch.
Even with the Allison, early P-51's were faster than contemporary P-40's...and the P-40 had already been through a few "developmental changes" by that time.
FWIW, the Merlin that _did_ make it into the P-40's were lower powered versions, making about 1300HP, and they didn't last long in the P-40. I think by the "K", they were back to outfitting them with Allisons.
Why? I don't know. Probably more "prioritizing".
The P-40 was a good honest airplane and one of the most successful designs of the war.
Early on, when we really had nothing else, it delivered a heck of a punch and gave us time to get our inventory "up to speed", but in the end, the 51 could just do everything better...outfitting it with the Merlin was just icing on the cake.



Elvis


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## Elvis (Feb 24, 2009)

davebender said:


> I think the 30L R1830 engine could have been developed further. With a better supercharger and other improvements you could probably achieve 1,400 hp. In addition you clean up the P36 airframe to make it more streamlined. Together these improvements should push the top speed up to about 375mph. This keeps the P36 competitive through 1942.


What do you think of outfitting that P-36 with an R-2000?
1425HP in the same sized package as the 1200HP R-1830.
The problem with all of this, may lie in sheer aerodynamics.
I know the Navy tried outfitting the R-2000 to the F4F (which also used the R-1830) and found that performance just didn't change enough to make the swap worth it. 
It did help lead to the development of the F6F, though.
I wonder if the same would hold true with the P-36.
....remember, one advantage the P-40 had over the 36 was much less frontal area, thus it was more aerodynamically efficient.



Elvis


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## davebender (Feb 24, 2009)

Sounds good to me.  

However you still need to make the P36 more aerodynamic if you want it to have a higher top speed. Otherwise you will only improve the acceleration and rate of climb.


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## Clay_Allison (Feb 24, 2009)

davebender said:


> Why was ANY American aircraft equipped with the Allison rather than the superior RR Merlin engine?


Allisons were in fact available in quantity, and it was not a bad engine in its' own right. I'd say the late Allison mark that powered the P-82 Twin Mustang was as good as any Merlin. The real question is why the stupid USAAF delayed domestic development of a good two-stage supercharger.


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## Clay_Allison (Feb 24, 2009)

davebender said:


> Will it fit? The R2600 radial is relatively large and heavy.
> 
> *R1830 twin radial.*
> 48.03 in diameter.
> ...


A later mark of 1830 would have been fine, it developed 1200 horsepower in the F4F with the -86.

The P-40 was ridiculously overweight for a fighter. It was a ground attack plane with some self defense capability from the beginning.

If the P-36 had been given later marks of engine and not overarmored so badly it might have been a better performer than the P-40 in fighter vs. fighter duels.


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## Elvis (Feb 25, 2009)

davebender said:


> Sounds good to me.
> 
> However you still need to make the P36 more aerodynamic if you want it to have a higher top speed. Otherwise you will only improve the acceleration and rate of climb.


True, thus my comments on aerodynamics.
...maybe if you used the big R-1340/R-2000 cylinders with the bottom end of the R-1535.
This would create an "R-1886" (possibly rounded up to "R-1890", for publications sake).
I know the Twin Wasp Jr. was about 6" narrower than the Twin Wasp, so if the fueslage was left alone, this would mean the cowling could be built in a more conical shape, aiding aerodynamics.
How much of a difference it would make overall?
I don't know.



Elvis


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## archerynut (Feb 25, 2009)

later in the development, like after they moved the machine guns from the cowling to the wings, i read they added almost 200 pounds of armour to the airplane, around the cockpit area. what would this have been? like heavy steel plating or something else bullet/shrapnel resistant?


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## Waynos (Feb 25, 2009)

Was the PW radial suitable for a Fw190/Sea Fury style close cowl? That was found to be the most aerodynamic way to cowl a big radial, maybe a model project in there?


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## tomo pauk (Feb 25, 2009)

delcyros said:


> The added weight is IN FRONT OF THE COG. Removing weight from BEHIND OF THE COG does make things worser! You need to elongate the hull and install dead weights (armour?) as far aft as possible to counter this. Or You move the wing forward.
> Remember also that it´s engine dry weight, not netto weight increases. The support frames needs to be enforced to cope with the heavier loads and torque effects produced by the larger engine, too.



Sorry if I haven't make myself clear (English is not my 1st language). The point was to put more armor fuel tanks behind pilot, and remove the radio further back.


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## davebender (Feb 25, 2009)

Like the Me-109 and Spitfire, the P-36 was a light weight fighter. There are limits as to how much armor and firepower you can add, unless you want to drastically reduce performance.

I think that a 375 mph P-36 armed with 4 x .50cal MGs would be good for Pacific service. It compares well with most Japanese fighter aircraft (both army and navy) and has adequate firepower for the job. Certainly better then both the naval F4F and army P-40.


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## HellToupee (Feb 25, 2009)

There were p-36s with more powerful engines 1200hp brits received a few called em Mohawks


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## tomo pauk (Feb 25, 2009)

davebender said:


> Like the Me-109 and Spitfire, the P-36 was a light weight fighter. There are limits as to how much armor and firepower you can add, unless you want to drastically reduce performance.
> 
> I think that a 375 mph P-36 armed with 4 x .50cal MGs would be good for Pacific service. It compares well with most Japanese fighter aircraft (both army and navy) and has adequate firepower for the job. Certainly better then both the naval F4F and army P-40.



Both Spit and 109 ended up with 2000 HP on board, so, while adding MGs and armor, we also add the power. 
I agree that a more moderate approach (1200HP and 4 HMGs) would serve it's purpose though.

Here is the _uber_ P-36/40, the XP-60:
Curtiss P-60 - Wikipedia, the free encyclopedia
It's combat performance was under 1944 standards.


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## Elvis (Feb 25, 2009)

I think a ground attack / second line fighter role would've probably been the best scenario for the P-36.
Minimal structure mods could've allowed it to carry a sizeable bomb/rocket load, and 4-50's would work well to back all those munitions up.
FWIW, I guess some P-36's actually made it into service, mostly with foreign nations.
In that case, I think the "best" engine it could've been outfitted with would've been a Wright Cyclone, as it seems a few copies were already being built in foreign countries, so there would've been an alternate supply of engines (besides us).

Interesting article on the P-60, Tomo. Thanks for posting the link.



Elvis


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## Elvis (Feb 25, 2009)

archerynut said:


> later in the development, like after they moved the machine guns from the cowling to the wings, i read they added almost 200 pounds of armour to the airplane, around the cockpit area. what would this have been? like heavy steel plating or something else bullet/shrapnel resistant?


Thin armour plating, which is essentially very heavy, very dense steel.
I used up an entire brand new 12" "Cuts-All" wheel (mounted on a chop saw) on one, one time, and barely scratched the surface.


Elvis


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## davebender (Feb 25, 2009)

Fact Sheets : Curtiss XP-42 : Curtiss XP-42
The P-42 is more what I have in mind. Improve the aerodynamics and engine HP without doubling the aircraft weight and tripling the aircraft cost. With a bit more effort the cooling problems could have been fixed in a manner similiar to the German Fw-190.


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## Clay_Allison (Feb 25, 2009)

Waynos said:


> Was the PW radial suitable for a Fw190/Sea Fury style close cowl? That was found to be the most aerodynamic way to cowl a big radial, maybe a model project in there?


They tried that with a bunch of different designs and they couldn't make it work.



> The cowling didn't significantly reduce drag and the engine had continuing cooling problems even though numerous cowlings were tested.


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## Elvis (Feb 25, 2009)

FWIW, here's some basic data on the P-36...

_Specifications: Curtiss P-36G Hawk / Mohawk 
Dimensions: 
Length: 28.51ft (8.69m)
Width: 37.01ft (11.28m)
Height: 9.25ft (2.82m) 
Performance: 
Max Speed: 322mph (518kmh; 280kts) 
Max Range: 650miles (1,046km) 
Rate-of-Climb: 2,500ft/min (762m/min) 
Ceiling: 32,349ft (9,860m; 6.1miles) 
Structure: 
Accommodation: 1
Hardpoints: 1 
Empty Weight: 4,676lbs (2,121kg)
MTOW: 5,880lbs (2,667kg) 
Power: 
Engine(s): 1 x Wright R-1820-G205A Cyclone piston radial engine generating 1,200hp. 
Weapons:
4 x 7.62mm machine guns
2 x 12.7mm machine guns_

I read that there was one or two test aircraft put together that was armed with one 23mm cannon on each wing (along with one .30 and one .50 MG mounted in the nose), so it may be that the military was considering a ground attack variation at one time.
Personally, I think two 50's in each wing may have proved more useful, if you consider the alternate "second line fighter" role it could've been pressed into, as well.



Elvis


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## JoeB (Feb 25, 2009)

Elvis said:


> FWIW, here's some basic data on the P-36...
> 
> 
> I read that there was one or two test aircraft put together that was armed with one 23mm cannon on each wing (along with one .30 and one .50 MG mounted in the nose), so it may be that the military was considering a ground attack variation at one time.


Thailand's Hawk 75N export versions had the 23mm cannon; also fixed undercarriage so somewhat slower. They saw air combat action against French Ms406's in the Thai-French war of 1940-41.







Joe


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## davebender (Feb 26, 2009)

Curtiss Hawk 75A-3 (P36G)
According to the above flight simulator site, which may or may not be accurate, the P-36 was very maneuverable at both slow and high speed. However it was slow and had a poor rate of climb. 

The P-40 had a decent top speed. However it still had a poor rate of climb and was less maneuverable then the P-36. The self sealing fuel tanks are nice. But this is offset by the liquid cooled engine being inheritly more vulnerable. 

At $23,000 each the P-36 cost 38% the price of a P-40 and 17% the price of a P-38. With a production cost that low it could become the ultimate Lend-Lease fighter aircraft. Produce 1,000 per month and give them to everyone in the Pacific except Japan. It is one of the few aircraft that can dog fight with the Japanese A6M, Ki-27 and Ki-43.


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## MikeGazdik (Feb 26, 2009)

davebender said:


> Curtiss Hawk 75A-3 (P36G)
> 
> At $23,000 each the P-36 cost 38% the price of a P-40 and 17% the price of a P-38. With a production cost that low it could become the ultimate Lend-Lease fighter aircraft. Produce 1,000 per month and give them to everyone in the Pacific except Japan. It is one of the few aircraft that can dog fight with the Japanese A6M, Ki-27 and Ki-43.



But who will make them? Curtiss was maxxed out, which is why North American was approached to build them.


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## davebender (Feb 26, 2009)

Build a new state of the art factory. Just like we did for the production of so many other aircraft models.


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## Elvis (Feb 26, 2009)

MikeGazdik said:


> But who will make them? Curtiss was maxxed out, which is why North American was approached to build them.


...on top of that, the Brewster F2A-1 was a more maneuverable airplane, had a better climb rate and was better armed.....plus I think the U.S. government was more willing to "lease" those, than the P-36's, if for no other reason than Brewster was kind of a pain in the government's _rear end_.
The relationship with Curtiss was older and much better.

Also, here's something that _might_ warm davebender's heart just a little.
A summary of how the P-36 fared in service to Finland...


Warbirds Resource Group said:


> Finland
> 
> After the fall of France, Germany agreed to sell captured Curtiss Hawk fighters to Finland in October 1940. In total, 44 captured aircraft of five subtypes were sold to Finland with three deliveries from 23 June 1941 to 5 January 1944. Not all were from the French stocks, but some were initially sold to Norway and captured in their wooden crates when the Germans conquered the country. The aircraft were given serial codes CU-551 to CU-585.
> 
> ...








So it seems the P-36 was used successfully by, at least some of, the foreign nations it flew under.
That being stated, though, the Finns were known to prefer the Brewsters over the Mohawks.



Elvis


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## Elvis (Feb 26, 2009)

JoeB said:


> Thailand's Hawk 75N export versions had the 23mm cannon; also fixed undercarriage so somewhat slower. They saw air combat action against French Ms406's in the Thai-French war of 1940-41.
> 
> 
> 
> ...


Hey, thanks Joe!
Cool pic of the bird, too.


Elvis


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## Elvis (Feb 26, 2009)

davebender said:


> Build a new state of the art factory. Just like we did for the production of so many other aircraft models.


Dave,

Other than North American (P-51) and Boeing (B-17), who else did that?...and for what aircraft?
Sounds like a lot, but I'm only aware of those two.



Elvis


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## FLYBOYJ (Feb 26, 2009)

The Hawk 75A IMO was one of the most under-rated fighters of WW2. Although it was said to be "slow," compare it to *early* Bf 109s, Hurricanes and Spitfires. From wiki, take it for what it's worth.

_On 8 September 1939, aircraft from Groupe de Chasse II/4 were credited with shooting down two Luftwaffe Messerschmitt Bf 109Es, the first Allied air victory of World War II on the Western front. During 1939–1940, French pilots claimed 230 confirmed and 80 probable victories in H75s against only 29 aircraft lost in aerial combat. Of the 11 French aces of the early part of the war, seven flew H75s. The leading ace of the time was Lt. Edmond Marin la Meslée with 15 confirmed and five probable victories in the type. H75-equipped squadrons were evacuated to French North Africa before the Armistice to avoid capture by the Germans. While under the Vichy government, these units clashed with British aircraft over Mers el-Kébir and Dakar. During Operation Torch in North Africa, French H75s fought against U.S. Navy F4F Wildcats, losing 15 aircraft to seven shot down American planes. From late 1942 on, the Allies started re-equipping French units formerly under Vichy and the H75s were replaced by P-40s and P-39s.

In Finnish service, the Hawk was well-liked, affectionately called Sussu ("Sweetheart"). The Finnish Air Force enjoyed success with the type, credited with 190 1/3 kills by 58 pilots, between 16 July 1941 and 27 July 1944, for the loss of 15 of their own.[2] Finnish ace Kyösti Karhila scored 13 1/4 of his 32 victories in the Hawk, while the top Hawk ace K. Tervo scored 15 3/4 victories. The Hawks were flown by Lentolaivue 32 throughout their wartime operational service._


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## MikeGazdik (Feb 26, 2009)

I think the P-36 and P-40 are both quickly and wrongly forgotten when speaking of fighters.

Both of these aircraft performed quite well, considering in almost all cases they were out-numbered, flown by less experienced pilots , and were flown when either poor tactics were used, or good tactics were only being discovered.

The scars and failures learned with (but not neccessarily the fault of )both of these planes, contributed to even better designs and tactics. That coupled with the reversal of pilot expererience and numbers, made the Allies later aircraft appear much better then they were.

If we gauged the Me 109 the same way, it would be considered an utter and complete failure. It lost the war, it couldn't stop the bombers, the alllied fighters shot it down in droves. But we know that is not true. It was a brilliant fighter with some deficiencies, I think, the same as the Curtiss Warhawk.


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## HoHun (Feb 27, 2009)

Hi Dave,

>Curtiss Hawk 75A-3 (P36G)

>According to the above flight simulator site, which may or may not be accurate, the P-36 was very maneuverable at both slow and high speed. However it was slow and had a poor rate of climb. 

Hm ... this site says "The Bf109E4 is faster than you by about 20kph", but I don't think the Hawk was so fast (or the Me 109E-4 so slow) that this could be realistic.

Here is an analysis of the Hawk I prepared a while back ...

Regards,

Henning (HoHun)


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## Clay_Allison (Feb 28, 2009)

Vultee could have made cheap P-36s under license for lend lease, Brewster could make Buffaloes for lend lease. One used the P&W Twin Wasp, the other used the Wright Cyclone 9, so there was a niche for both.


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## Elvis (Mar 1, 2009)

HoHun said:


> Hi Dave,
> 
> >Curtiss Hawk 75A-3 (P36G)
> 
> ...



HoHun,

Forgive me if this sounds like a silly question, but what is the line running through the graph represent?
It doesn't seem to corresspond with the plots.


Elvis


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## HoHun (Mar 1, 2009)

Hi Elvis,

>Forgive me if this sounds like a silly question, but what is the line running through the graph represent?
>It doesn't seem to corresspond with the plots.

The line is the performance I calculated for the Hawk 75C powered by the R-1830-17, running at 2700 rpm.

It is calibrated to the coresponding data point from T.O. 01-25CB-1 - as the other data point from that source is for another power setting, that one is not on the line.

The line also runs close to another data point for P-36A and C with the same engine.

The other data points are for differently-engined Hawk variants so they cannot be expected to coincede with the calculated performance line.

Regards,

Henning (HoHun)


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## Elvis (Mar 6, 2009)

Ah, I see now.
Thanks for explaining that.

...and since I'm here...



Clay Allison said:


> Vultee could have made cheap P-36s under license for lend lease, Brewster could make Buffaloes for lend lease. One used the P&W Twin Wasp, the other used the Wright Cyclone 9, so there was a niche for both.


I don't know about Vultee, but that's the very reason why Brewster and the US Government ended up on bitter terms.
Brewster kept promising to fill the orders, but could never deliver.
_Maybe_, if the Government had owned the Buffalo design (like what they did with the Jeep), Vultee could've been brought in to help produce the plane for sale/lease to foreign markets (thus a "Brewster / Vultee Buffalo" would've existed), along with the P-36, but Brewster, as the sole manufacturer, seemed to have a hard time actually producing the design in the numbers the military needed.
This could've eventually led to the two companies coming together, to create one "new" company, who's job would've been to produce planes (and maybe other munitions) for foreign sales / lease.
...and this probably would've included some P-40 manufacture, as well.
Of course, with the demand for "US-use-only" _items_ needed so desperately, I feel that may have been only part of what they would've been doing.

So maybe, "_B-V Aviation_", or "_Brew-Tee_", or maybe even, "_Vulster_" might have a been name that would now be remembered as one of the manufacturers that helped with the war effort during those years...had this actually happened.


Elvis


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## renrich (Mar 6, 2009)

I believe the Willow Run factory was built by Ford to build B24s. GM may have built a factory to build FM2s and TBMs and Goodyear also to build Corsairs.


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## renrich (Mar 6, 2009)

Mike the F4F was the same vintage fighter as the P40 and was flown by pilots in the beginning with no combat experience but acquitted itself well against tough competition.


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## Marshall_Stack (Mar 6, 2009)

I believe Bell created a plant in Marietta Georgia to produce B-29s and Boeing built a plant in Kansas to build B-29s.


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## HoHun (Mar 7, 2009)

Hi Elvis,

>FWIW, the Merlin that _did_ make it into the P-40's were lower powered versions, making about 1300HP, and they didn't last long in the P-40. I think by the "K", they were back to outfitting them with Allisons.

>Why? I don't know. Probably more "prioritizing".

Have a look at the performance curves here:

http://www.ww2aircraft.net/forum/aviation/p-40-performance-allison-versus-merlin-14118.html

The lower-powered Merlin versions used in the P-40F wasn't so much better than the Allison V-1710, all considered.

It might be that the Allison was in fact more attractive for the P-40 since emphasis in P-40 use had shifted away from fighter missions towards ground attack, where a better take-off performance when loaded and more power at lower altitudes were an advantage. I haven't checked if this matches the powerplant timeline, though.

Regards,

Henning (HoHun)


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## Marshall_Stack (Mar 9, 2009)

I read that the P-40s went back to Allisons because Packard was too busy making the Merlins for P-51s.


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## MikeGazdik (Mar 9, 2009)

renrich said:


> Mike the F4F was the same vintage fighter as the P40 and was flown by pilots in the beginning with no combat experience but acquitted itself well against tough competition.



You are very right, as I would say too of the P-40. ( one source,article by Corwin Meyer) shows the F4F/ FM kills at 1006, the P-40 at 706 in the Pacific.

Which considering the time in which they fought, far from useless.


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## Elvis (Mar 12, 2009)

HoHun said:


> Hi Elvis,
> 
> >FWIW, the Merlin that _did_ make it into the P-40's were lower powered versions, making about 1300HP, and they didn't last long in the P-40. I think by the "K", they were back to outfitting them with Allisons.
> 
> ...


Took a look at the link. Thanks for posting that.
Its clear that the Merlin was a more stoutly built engine, than the Allison, thus you could "huff it up" a lot more, and push it harder, without fear of breakage, compared to the Allison.
This is clearly evident in the performance improvement that occured between the 20 and the 60 series versions of the Rolls Merlin engine.
The fact that the Allison was built a little lighter was also probably one of the leading reasons why it had less supercharging available to it, thus its performance was more fitting to lower altitude operations.

That being said, I wonder how a single stage, two-speed _intercooled_ version of the Allison, with a larger supercharger (say around 12"-15") would've faired. Especially in one of the "G" engines, which had the better crankshaft in it.
I looked around a little the other night, but could not find mention of such a beast, so I'm assuming it never existed.  
That setup would be similar to the Merlin you aluded to, that was used in both the P-40 and the early Merlin-powered 51's.
According to my (rather rudimentary) calculations, an Allison setup in that fashion, and being one of those types, would have a peak HP rating somewhere in the upper 1300 - lower 1400 HP range.
...plus you trim about 300-400 lbs. off the plane, because the Allison is lighter.
I think the Allison could live very nicely setup in that fashion and probably would've had more useable power over a wider altitude range, than most of the versions that did exist during that time.
Now, you combine that with a _more efficient_ propeller and now you've got something.

The combination of engine / prop would probably have improved the P-40's lack of "bounce", in any case.




Elvis


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## HoHun (Mar 12, 2009)

Hi Elvis,

>That being said, I wonder how a single stage, two-speed _intercooled_ version of the Allison, with a larger supercharger (say around 12"-15") would've faired. 

Qualitatively, increasing the since of the supercharger increases high-level performance at the cost of reduced low level performance. As the two-speed gear allow the operation of the larger supercharger at a reduced speed, this will restore most of the low-level power.

In effect, the setup you're proposing is similar to the Merlin XX, and accordingly, the P-40F can be seen as a good example for the kind of performance one might expect.


(The main problem of the P-40 was its heavy weight ... I think most of its other characteristics were good or at least satisfactory. Weight unfortunately has quite an impact on climb rate and manoeuvrability though, so it was difficult to get around this. The lighter British designs would always get more performance and manoeuvrability out of an equivalent engine.)


>According to my (rather rudimentary) calculations, an Allison setup in that fashion, and being one of those types, would have a peak HP rating somewhere in the upper 1300 - lower 1400 HP range.
...plus you trim about 300-400 lbs. off the plane, because the Allison is lighter.

Hm, how did you calculate that? I'm interested even if it's a "rule of thumb" approach 

Regards,

Henning (HoHun)


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## claidemore (Mar 12, 2009)

Here's an interesting sight by a guy who flew P40-Fs in the MTO. 

http://www.charlies-web.com/WWII_med/index.html

A related website about 12 TAF.

12th Army Air Force


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## renrich (Mar 12, 2009)

The P40 had good results against the Japanese Army AC in the CBI, not as good against the IJN in the Pacific. My source has the P40 with 741 kills in the CBI and 661 kills in the Pacific. The F4F had 1408 kills in the PTO. My source gives the P40 592 kills in the Med and another source shows the P40 with 67059 sorties with 553 losses in the ETO. Those must have been in the Med which would have included Italy.


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## MikeGazdik (Mar 13, 2009)

For what it is worth, I think it is difficult to compare U.S. Navy fighter kills vs the U.S. Air Corps fighter kills in the Pacific. The Navy was usually in a much more target rich environment than the Air Corps. What I am trying to say is the kill numbers don't tell the whole story.

Is there any information to compare kills vs loss on the F4F against the P-40?


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## Elvis (Mar 13, 2009)

HoHun said:


> Hi Elvis,
> 
> >That being said, I wonder how a single stage, two-speed _intercooled_ version of the Allison, with a larger supercharger (say around 12"-15") would've faired.
> 
> ...



Something you'll have to explain to me - why is it that I keep seeing comments about the P-40's weight?....or rather, _over_weight.

I think if you averaged out the weight for all the different models of P-40 that existed, I bet you'd find the plane generally found itself around 8500-10000 lbs.
Does this make the P-51, which was like 12500 lbs. by the time the "D" model came around, _obese_?
If so, why does that fact never seem to come up whenever the 51 is mentioned?
Comparitively, the P-40 seems like a lightweight and yet I see comments written all the time about the plane being overweight.

As for the power figures I aluded to, I should recheck those, but it was nothing more than a simple HP/Cu.In comparison, then I added in a little, allowing for the higher R's that version of the Allison could operate in.
Not really anykind of "rule of thumb". More like a "ballpark" figure.



Elvis


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## renrich (Mar 13, 2009)

The power loadings tell the tale. At 10000 feet the power loading of the P40F at 8678 lbs GW was 7.11 and at 20000 feet was 8.15. The corresponding for the P51D at 10176 lbs GW were 6.78 and 7.48. The P40 at all altitudes had more weight per HP available and was not nearly as clean so drag not only slowed it down but hampered it's climb significantly.


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## carson1934 (Mar 14, 2009)

This has nothing to do with P-40's but I take nevertheless the liberty to ask you whether someone of you guys could send thru a picture of the Curtiss A-12 Shrike while servicing in China or this aircraft with chinese (nationalist) markings.
Thanks a lot
carson1934


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## HoHun (Mar 14, 2009)

Hi Elvis,

>Something you'll have to explain to me - why is it that I keep seeing comments about the P-40's weight?....or rather, _over_weight.

Just have a look at the fighters it opposed - they were all lighter than the P-40, or in the case of the Fw 190, had a lot more power to make up for the weight.

>As for the power figures I aluded to, I should recheck those, but it was nothing more than a simple HP/Cu.In comparison, then I added in a little, allowing for the higher R's that version of the Allison could operate in.

Not a bad method, considering that indicated power depended on displacement. The effect of supercharger power being subtracted from indicated power, leaving a reduced brake power value, means it's not perfectly accurate, but I'm still searching for a perfectly accurate method to calculate brake power from the geometric parameters of an engine 

Regards,

Henning (HoHun)


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## renrich (Mar 14, 2009)

Elvis, switching from the other thread and discussing a P40 outclimbing a Spit, Bob Johnson in his book, "Thunderbolt" said the early Jug could not stay with a Spit in a steady climb. His tactics in a mock dogfight with a Spit were, with the Spit on his tail, to start rolling one way and then the other, as the Spit did not roll as well as the Jug. Once he had the Spit out of firing position, he would dive(the Spit could not stay with him in a dive) until reaching a very high speed and then zoom climb as the Spit could not zoom climb like a Jug, until far enough above where he could hammerhead stall and drop down on the Spit still laboring to get to his altitude. The P40 rolled well(better than the Jug) and dived well. Perhaps the pilot you quoted meant that he could outclimb a Spit in a zoom climb.


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## Sweb (Mar 14, 2009)

Intensifying an engine design, when good quality assurance standards are uninhibited at the manufacturing level, can produce some interesting results. One in particular is the Nakajima HA-45 Homare. It was an 18 cylinder, twin row air cooled short stroke engine with a diameter about 46 inches and HP rating of 1900. This was the engine used in the Ki-84. Had there been 100 octane fuel available to the Japanese Army this engine/airframe combination would (not might) have enjoyed equality with anything the Allies had at the time. But, the engine was a compact powerhouse plagued by quality control problems in its manufacturing.


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## drgondog (Mar 14, 2009)

Elvis said:


> Something you'll have to explain to me - why is it that I keep seeing comments about the P-40's weight?....or rather, _over_weight.
> 
> I think if you averaged out the weight for all the different models of P-40 that existed, I bet you'd find the plane generally found itself around 8500-10000 lbs.
> Does this make the P-51, which was like 12500 lbs. by the time the "D" model came around, _obese_?
> ...



A 51 at 12,500 pounds is one that just took off with two 160 gallon ferry tanks or two 1000 pound bombs, and a full internal load of 270+ gallons of fuel and 1860 rounds of 50 cal... and 200 pounds of pilot.

Yes, that would be obese for air to air combat - but the 51 would still be faster than the P-40K (and light) at 25,000 feet.

The empty airframe weight of both ships were close - the Mustang had the heavier engine and far more internal fuel.


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## Demetrious (Mar 14, 2009)

renrich said:


> Elvis, switching from the other thread and discussing a P40 outclimbing a Spit, Bob Johnson in his book, "Thunderbolt" said the early Jug could not stay with a Spit in a steady climb. His tactics in a mock dogfight with a Spit were, with the Spit on his tail, to start rolling one way and then the other, as the Spit did not roll as well as the Jug. Once he had the Spit out of firing position, he would dive(the Spit could not stay with him in a dive) until reaching a very high speed and then zoom climb as the Spit could not zoom climb like a Jug, until far enough above where he could hammerhead stall and drop down on the Spit still laboring to get to his altitude. The P40 rolled well(better than the Jug) and dived well. *Perhaps the pilot you quoted meant that he could outclimb a Spit in a zoom climb.*



I just came to the exact same conclusion in the Brewster Buffalo thread. 



drgondog said:


> Yes, that would be obese for air to air combat - but the 51 would still be faster than the P-40K (and light) at 25,000 feet.
> 
> The empty airframe weight of both ships were close - the Mustang had the heavier engine and far more internal fuel.



Thank you ever so much for pointing that out. I do get annoyed with people (often Spitfire fans) who deride the P-51 as a "pig" because of it's high loaded weight. One must remember that a P-51's "combat" weight- having reached the target, and burned up a little less then half of it's fuel- was much. much lighter. And if you want to compare the P-51 to a dedicated, short-legged interceptor like the Spitfire or the 109, then only factor in 30 minutes worth of fuel for the P-51, since a Mustang being used in that role wouldn't be prepped with more then was needed, to improve performance.


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## slaterat (Mar 14, 2009)

Back to the P 40 weight question. Lets compare it too a Hurricane IIb. Both planes of similar dimensions and size with the same engine.

Tare weights H IIb 5,467 lbs P 40f 6,482

Combat weights H IIb 7,255 P40f 8,979 (P 40 carries more fuel 174 gals to 94)

top speed HIIb 342 mph 24,000 ft, P40f 354 mph 20,400ft

Climb rate

H IIb 2,950 ft/min P40f 2,370 ft/min


I guess you could presume that the drag co efficient is fairly close, with a slight adv to the P40f ? But look at the neg affect weight has on climb rate.

Slaterat


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## renrich (Mar 14, 2009)

To me, as an armchair fighter pilot, climb means at least two things. One is how long it takes to climb to where the fight is or is going to be. The P40 really labored to get from the ground up to say 25000 feet. That hampered it in the interceptor role. Two is the ability to climb away from an opponent in ACM. The P40, if it started with an altitude advantage, could make a diving gunnery run, and then zoom climb to regain altitude advantage. If a P40 found itself with no altitude advantage against an A6M or BF109, it was in trouble as far as offensive action was concerned.


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## Demetrious (Mar 14, 2009)

I'll second the problems with interception in a P-40 (try climbing to chase bombers in that tub sometime in any game you might want to name,) but a lack of altitude is not as much a problem versus a Zero, whereas it's problematic versus a 109. Zero pilots loved to exploit their good climb rate, so sooner or later the Zero was going to dominate the altitude advantage- which could be negated by the P-40s higher top speed. Simply extend away and let the Zero hang there all it wants. 

You can't do that with a 109, however, and the 109's superior power makes it dominant in the vertical as well. Victory there would really rely on the P-40 managing to force a scissors or turn and burn fight, where it excels.


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## Elvis (Mar 14, 2009)

renrich said:


> The power loadings tell the tale. At 10000 feet the power loading of the P40F at 8678 lbs GW was 7.11 and at 20000 feet was 8.15. The corresponding for the P51D at 10176 lbs GW were 6.78 and 7.48. The P40 at all altitudes had more weight per HP available and was not nearly as clean so drag not only slowed it down but hampered it's climb significantly.


Ah, maybe that's it.
Yeah, without some decent SC'ing, that plane loses a lot, and fast, as it goes up.
So maybe the "overweight" comments were that it _seemed_ a bit "pudgy", due to the lack of power at altitude.
Ok, thanks, that's most likely it.

As for the P-40 vs. Spit comment, hey, like I said before, I don't know what else to tell you.
I ran the video and watched it myself, just before I wrote that, because I couldn't exactly remember how those comments went.

If you like, maybe you could get a copy of the video and watch it for youself, then you can tell me what he meant.

The video is called "Kittyhawk" and is about a restoration project by the late Col Paye.

Upon the restored plane's maiden flight at Scone in NSW, a bunch of WWII Aussie pilots were invited to watch the proceedings, Bobby Gibbs being one of them.

The host of the show interviewed Gibbs while sitting in an (that?) airplane and was asked to comment on some of the performance _pluses_ of the P-40.
Some of those comments are what I posted in that other thread.

Lastly, I finally drug my butt over to the "mustangsmustangs" website and yeah, you're right. 12500 was a little on the "portly" side for a D varient 51. 
Sorry, was working off the top of my head (as I usually do) and that's how I remembered it.




Elvis


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## Elvis (Mar 14, 2009)

A couple more musings about the P-40 / Spit comparison...

According to Chuck Hawks
A Spit Mk.IIA of 1940 had a "best" climb of 3,025 ft/min at 12,800 ft.
It could achieve 10,000 ft. in 3.4 min and 20,000 ft. in 7 min.

According to Joe Baugher 
"_The first flight of a P-40 (Ser No 39-156) was on April 4, 1940. Maximum speed was 357 mph at 15,000 feet, service ceiling was 32,750 feet, and *initial climb rate was 3080 feet per minute. An altitude of 15,000 feet could reached in 5.2 minutes.* The length of the P-40 was 31 feet 8 3/4 inches, which became standard for all early models. Weights were 5376 pounds empty, 6787 pounds gross, and 7215 pounds maximum._"

Now, if you look back at Chuck Hawk's comments of a Spit of similar vintage and average out those "time-to-altitude" figures, do you know what you end up with?

*15000 ft. in 5.2 min.*  

Exactly the same figure as Joe Baugher states for the first P-40 (incidentaly, that works out to 2884.6153 ft./min.)



Elvis


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## Ivan1GFP (Mar 14, 2009)

Hello Elvis,

Typically the climb rate of an aircraft improves slightly as the aircraft goes from sea level to 3000 to 5000 feet and then decreases as the altitude increases. Thus your identical average climb rates to different altitudes doesn't mean the aircraft climb rates are comparable.

This is just a personal opinion, but JoeB is about as reliable as it gets as far as facts and research. I don't believe I can say the same about your other source.

BTW, for the general discussion, consider that early Allison engine Mustangs had essentially the same engine as installed in contemporary P-40s and were about 30-40 mph faster. That says a lot for aerodynamics. I wonder what would have happened if the P-46 had been developed alongside the P-51.

- Ivan.


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## claidemore (Mar 15, 2009)

Elvis said:


> A couple more musings about the P-40 / Spit comparison...
> 
> According to Chuck Hawks
> A Spit Mk.IIA of 1940 had a "best" climb of 3,025 ft/min at 12,800 ft.
> ...



With the Merlin XII the MkIIa Spitfire shows a climb to 15,000 ft in 5.0 minutes. Climb rate at sea level was 2915, highest climb rate was at 3010ft/min at13000 ft. Climb rates improved dramatically with the MkV, IX and higher. 

Time-wise, (September 1940) I think a more accurate comparison would be the P40B or P40C with initial climb rates of 2860 and 2650 ft/min. 

Later variants, P40-D,E (Kittyhawk I) needed 8.85 minutes to 14,000 ft. The 'lightweight' P40N could reach 15,000 feet in 7.3 minutes. A Spit IX with Merlin 66 was getting to 15000 feet in about 3 1/2 minutes.


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## renrich (Mar 15, 2009)

Demetrious, the P40 did not have a tactically significant speed advantage over the A6M especially at altitudes above 15000 feet. It just did not have the power available, plus it did not accelerate as well. An interesting footnote is that in tests against the Aleutian Zero the US fighters had difficulty with mechanical problems whereas the Zero just kept performing well. Against the P40F the test was discontinued because the P40 engine could not be made to put out full power. The first production P40, the prewar H81 was the fastest of all P40s with a top speed of just over 365 mph at 15000 feet with military power. The late model N5 to N40s were almost 20 mph slower. The Allison P40K had a sea level rate of climb at just over 2000 fpm. The best advice for a P40 pilot against the Zero was the same as to all USN fighter pilots, "do not dog fight with a Zero."


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## Elvis (Mar 15, 2009)

Ivan1GFP said:


> Hello Elvis


Hello Ivan!



Ivan1GFP said:


> Typically the climb rate of an aircraft improves slightly as the aircraft goes from sea level to 3000 to 5000 feet and then decreases as the altitude increases. Thus your identical average climb rates to different altitudes doesn't mean the aircraft climb rates are comparable.


Yes, I understand what you're saying and have no reason to doubt you, whatsoever, but if it takes two planes the same amount of time to get from point A to point B, what does it matter if one is faster at a particular altitude, than the other, if it all equals out in the end?




Ivan1GFP said:


> This is just a personal opinion, but JoeB is about as reliable as it gets as far as facts and research. I don't believe I can say the same about your other source.


What do you know about Chuck Hawks?
PM me, if you prefer.




Ivan1GFP said:


> BTW, for the general discussion, consider that early Allison engine Mustangs had essentially the same engine as installed in contemporary P-40s and were about 30-40 mph faster. That says a lot for aerodynamics. I wonder what would have happened if the P-46 had been developed alongside the P-51.
> 
> - Ivan.


Yes, when it comes down to it, the 51 is just a more advanced design that the P-40 could not be "re-designed" to match.
However, this in itself, is a testament to the P-40's design, in that it was still adaptable enough to be of use as a _fighting vehicle_ all the way through the war.
...and not to get too far off track, but since you mentioned the 51, I've always wanted to see a B/C version with the Allison, but setup like the early Merlin (i.e., two-speed, single stage, intercooled).
Would probably put out about the same power (giviing a little more to the Alli's increased displacement...or maybe it would all equal out?), but the plane is lighter by about 300-400 lbs. and better balanced.
Would be interesting to see what improvements, if any, showed up and by what degree, compared to the Merlin version that actually existed.



Elvis


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## drgondog (Mar 16, 2009)

Elvis said:


> Hello Ivan!
> 
> 
> Yes, I understand what you're saying and have no reason to doubt you, whatsoever, but if it takes two planes the same amount of time to get from point A to point B, what does it matter if one is faster at a particular altitude, than the other, if it all equals out in the end?
> ...



If the Allison 1710-119 had been available in 1941 there would never have been a Merlin in the Mustang. It later powered the P-82 and was a superb engine with peak Hp in 2000hp range at max boost/water injection


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## Demetrious (Mar 16, 2009)

renrich said:


> Demetrious, the P40 did not have a tactically significant speed advantage over the A6M



Yes it did. 

The P-40, in the earlier war, had something in the neighborhood of 20-30 MPH advantage on the Zero, if memory serves, and that's all one needs to extend away from a bandit. You will slip away slowly, but you will slip away. However, that is nowhere near enough to simply "put the hammer down" and expect to be able to run from a bandit in close proximity, especially given the P-40's anemic acceleration. Key to using speed in a P-40 relied on retaining enough energy in the initial attack to put one beyond guns range (at least seven hundred yards to be safe,) at which point one could choose to re-engage, or extend away. 

According to data I found on the wide internet after a very non-vigourous search, the P-40C had an 18mph advantage on the A6M2. That's _just_ enough to prevent the Zero from controlling the engagement, but here the superior dive characteristics of the P-40, used in conjunction with it's roll performance and energy retention qualities are what would win the fight. As far as extending/disengaging, a dive to gain the needed distance, followed by a straight run, would probably be enough for the P-40 driver to escape (unless the Zero pilot was keen on tailing him all the way back to his base.) A potential for an escape seems significant to me, though it's not a real game changer. Of course, a 20mph advantage is insufficient to chase down a running Zero, but if you _really_ wanted you could nibble down the distance. 

The P-40E, however, also came out in 1941 (which strikes me as a very rapid deployment,) and it's speed advantage was around 30MHPH, which was a bit more useful. 

I think the consequences of this- determining the escape potential of a P-40 (which is likely guaranteed the ability to extend past gun range even given a few thousand feet of altitude to dive from,) is "significant," but as for making a difference during the actual engagement, I agree that it was useless. 



> The best advice for a P40 pilot against the Zero was the same as to all USN fighter pilots, "do not dog fight with a Zero."



The best advice was "don't turn-fight a zero." I'm not sure if that should be equated with dogfighting.


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## Vincenzo (Mar 16, 2009)

was "do not dog-fight with the zeke"


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## renrich (Mar 16, 2009)

One place where the Zero and the P40 were most likely to meet in the early war in any sustained combat would have been at Guadalcanal in late 42, early 43. The P40s were likely to be P40Es and the Zeros were likely to be A6M3s. That P40E had a Vmax of around 360 mph at miltary power at 15000 feet but it dropped off rapidly above and below that altitude. At 20000 feet it could barely touch 330 mph. The A6M3 could do 338 mph at 19690 feet so the P40 would have had to stay at 15000 feet to have a vmax advantage. I still don't believe that is tactically significant. ACM is not won by running away.


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## JoeB (Mar 16, 2009)

The chapter in the 5th AF's tactics manual (ca. early '44) about P-40 and Zero mentioned stuff like:

-that the intial anti-Zero tactic had been 'one pass and go home', referring to time period like spring-summer '42 when 49th FG was defending Australia v Zeroes escorting bombers; and per Japanese accounts the RAAF 75th Sdn operated similarly in New Guinea in same period (but Zeroes still held a definite real exchange ratio advantage in those campaigns). In early 1942 campaigns in Philippines and Dutch East Indies P-40's had worse results with 'come as you are' tactics v Zeroes.

-but 'extending away' from Zeroes, ones not yet in firing range, and coming back for more firing passes, was eventually made to work. One issue with that though is it probably mainly reflects experience in New Guinea in 1943 were the radial opponents were Type 1's (Oscars) not Zeroes. In CBI the AVG's initial opponents were Type 97's, against whom they established a winning trend which they maintained against Type 1's, and Type 1's remained the main opponents of the 10th and 14th AF P-40's until later Japanese Army types appeared; Zeroes were only encountered by USAAF fighters in China in a few cases much later on (1944).

-the terminology was 'don't dogfight', though they meant by that, no turning fight.

-escaping a Zero in firing position was always by diving steeply. If the P-40 was too low to dive, it wasn't viewed as any sure thing that a P-40 could stay ahead of a Zero in level flight near sea level (though on paper it should be able to). The instruction in case of Zero on tail at low altitude was porpoise, skid and 'a prayer would come in handy'.

Joe


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## renrich (Mar 17, 2009)

Actually Joe B, another point to add to your remarks. Ira Kepford had an extremely long mission and extremely harrowing one which demonstrates your point in the last paragraph. He found himself on the deck, in an F4U, after flaming a floatplane, being dived on by 3 or 4 Zekes. He forced an overshoot by the leader and shot him down and then went to combat power to extend away. Ran out of combat power and then in full military power could not shake the 2 or 3 Zekes who were slightly above and behind him and his course was taking away from his base. After a while, in desperation, he reefed the Corsair into a tight 180 and one Zeke trying to follow stalled out and went into the water and the other gave up. He got back to base with almost no fuel and exhausted. I think that us armchair "experts" get enchanted with paper numbers, especially vmaxs and think those numbers determine most ACM kills. I have quoted Lundstrom where Wildcats had to fight at 50% throttle to conserve fuel and they survived.


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## Demetrious (Mar 17, 2009)

> *I think that us armchair "experts" get enchanted with paper numbers, especially vmaxs and think those numbers determine most ACM kills. I have quoted Lundstrom where Wildcats had to fight at 50% throttle to conserve fuel and they survived.*



This. And also this:



> t wasn't viewed as any sure thing that a P-40 could stay ahead of a Zero in level flight near sea level (though on paper it should be able to).



Varying with atmospheric conditions, and the pilots skill with engine settings- and perhaps even the quality of the maintenance done on the engine- the P-40s slim advantage might vanish. In actual combat, it was up to the pilot not only to milk every erg of performance from his crate, but to innately understand the fight and secure advantages that, by rights, he shouldn't be able to get. 

I think much of the P-40s problems stemmed from the fact that the P-40s advantages were harder to understand and capitalize on, while the Zero's- which was "turn, turn, turn-" was easy and intuitive. There's a reason why most of the newbies in Aces High, the online fighter plane MMO, can be found in Spitfires. (Usually yelling at the _other_ newbies in Mustangs to stop running away and come turnfight. ^_^) I think this is one of the reasons I geek out over the P-40 like a schoolgirl with a new kitten: because a skilled pilot could take a seemingly underpowered and helpless machine and open a giant can of doom with it. 

Really, IMO, it was a fantastic airframe. It had a good turn radius, competitive against pretty much anything in the air, an excellent roll rate which was second only to a very few, a decently clean profile, a good armament, a good range, and on top of it all, it was incredibly rugged. The same outdated construction techniques that left it lacking in performance compared to new designs like the P-51 also gave it insane structural strength; the wikipedia page shows a ship that came home with 25% of one wing missing. 

If the P-40 had been equipped with a 1500 horsepower Merlin V engine like the Mustang D model had, I think the P-40s potential could have been truly realized.


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## Clay_Allison (Mar 17, 2009)

Demetrious said:


> This. And also this:
> 
> 
> 
> ...


I think that if they had used a large single stage, two (or three?) speed supercharger to give it improved altitude performance it would have been as good as the 109 and Spitfire until late-'42/early-'43.


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## Colin1 (Mar 17, 2009)

Demetrious said:


> The same outdated construction techniques that left it lacking in performance compared to new designs like the P-51 also gave it insane structural strength; the wikipedia page shows a ship that came home with 25% of one wing missing.
> 
> If the P-40 had been equipped with a 1500 horsepower Merlin V engine like the Mustang D model had, I think the P-40s potential could have been truly realized.


It depends on what you mean by construction techniques. The P-40 didn't have the same NACA wing-foil section as the P-51 but generally speaking WWII fighters were of the same aluminium monocoque design as one another. The P-40 was certainly closely related to the P-51 in this respect. 
The aerodynamicists-eye view of both planes however, was completely different; the P-51 was considerably more advanced, presumably that is what you meant.

I don't believe the P-40 possessed 'insane' structural strength, it was a hardy ship that could take some but a Hurricane pilot in the Battle of Britain lost two feet of his wing in an encounter. P-38s collided with telegraph poles. P-47s flew through treetops 'collecting firewood' in the mouth of their engine nacelles. All came home.

The P-40F and L were both fitted with Packard Merlins, the L in addition was stripped down in the quest for performance. This gifted it with a mere 4mph gain over the F which was good for roughly 360mph at a rated altitude of 10,000ft. The final variant of the P-40 was the P-40Q and at 420-odd mph it still wasn't as fast as the P-51. 
It would not and did not make commercial or tactical sense to introduce a competitor to the P-51 that wasn't as good. The P-40 already had truly realised its potential; at the time the 8th AF were escorting bomber streams into Europe, it was time for something new.


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## Demetrious (Mar 17, 2009)

Colin1 said:


> It depends on what you mean by construction techniques. The P-40 didn't have the same NACA wing-foil section as the P-51 but generally speaking WWII fighters were of the same aluminium monocoque design as one another. The P-40 was certainly closely related to the P-51 in this respect.
> 
> The aerodynamicists-eye view of both planes however, was completely different; the P-51 was considerably more advanced, presumably that is what you meant.



Well, wikipedia says of it thus: 

"It was a semi-modular design and thus easy to maintain in the field. It lacked innovations of the time, such as boosted ailerons or automatic leading edge slats, but it had a strong structure including a five-spar wing, which enabled P-40s to survive some mid-air collisions: both accidental impacts and intentional ramming attacks against enemy aircraft were occasionally recorded as victories by the Desert Air Force and Soviet Air Forces."

From what I've heard, the construction was overly "heavy," like the five-spar wing. Additionally, the older airfoil design was aerodynamically inferior to the NCA airfoil on the P-51, but it was also a lot sturdier (and heavier.) The P-51's airfoil was so thin that B model Mustangs didn't have electric gun chargers *and* jamming problems with their Brownings because the guns had to be installed at a funny angle. 

That was my impression, at any rate.



> I don't believe the P-40 possessed 'insane' structural strength, it was a hardy ship that could take some but a Hurricane pilot in the Battle of Britain lost two feet of his wing in an encounter. P-38s collided with telegraph poles. P-47s flew through treetops 'collecting firewood' in the mouth of their engine nacelles. All came home.



Yes, let's compare the P-40 to two of the hardiest aircraft of the war to dismiss it's durability as only average.  The P-47 and Hurricane were both legendary for their ability to absorb damage; putting the P-40 in that category firmly establishes it as one of the toughest, resilient air-superiority fighters of the war. That still means it's a very tough bird.



> The final variant of the P-40 was the P-40Q and at 420-odd mph it still wasn't as fast as the P-51.



Who cares? It still had superior turn and roll characteristics, making it more manuverable then the P-51, and with 420mph speed, it's one crippling vice- low power- would be compensated for nicely. As reinreich just pointed out, a 30MPH advantage "won't win ACM" (though it does obviously have consequences.)



> It would not and did not make commercial or tactical sense to introduce a competitor to the P-51 that wasn't as good. The P-40 already had truly realised its potential; at the time the 8th AF were escorting bomber streams into Europe, it was time for something new.



And where did I suggest that the P-40 should be introduced as a competitor to the P-51 in Europe? And what kind of crack would I have to be smoking to try, given that the P-51 was a long-range escort; a design unto itself? The P-40 wasn't even _used_ on the Western Front. 

As for commercial sense, the P-40 was $5,000 cheaper to build and more survivable, making it better at ground attack and arguably a better multi-role fighter (though that was true of the P-38 as well, which had an even better gun package and a longer range.) Of course, the P-40 was more manuverable then the P-38 as well, and the Merlin-engined models would not have had the crippling disability in the vertical. 

But this is neither here nor there. I'm simply saying that the P-40 was an excellent airframe, and all it lacked was a good engine to give it the ability to really walk and talk the way it wanted to. I never suggested that the Army should have produced Merlin-engined P-40s instead of some other aircraft type, since by the time those engines were available, the Army had already built tons of P-38s, F6Fs, and other planes that had excellent performance characteristics of their own. 

There might be something for suggesting that the Army could have saved themselves some trouble by tossing old Allison engines out of already-serving P-40s and installed new Merlins in them- an intelligent move at a time when _any_ combat aircraft was desperately needed- but every Merlin was badly needed for Mustangs in the ETO, and the same for the new 1200 horsepower Allisons for P-38s in the PTO.


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## Clay_Allison (Mar 17, 2009)

Seems like in the case of both the P-40 and the F4F, one of the big reasons that they "hung in there" for us was that they could take a beating and often get the pilot home, or give a pilot's buddy the time to bail him out when he was in a tight spot.


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## Colin1 (Mar 17, 2009)

Demetrious said:


> 1. Well, wikipedia says of it thus:
> 
> 2. The P-51's airfoil was so thin that B model Mustangs didn't have electric gun chargers *and* jamming problems with their Brownings because the guns had to be installed at a funny angle.
> 
> ...


You're deeper in 'schoolgirl with a new kitten' than you realise...

1. Wiki's OK up to a point, don't labour under any illusions that it is a bible of any sort

2. I'd describe that as a bug in the overall design (which was resolved), rather than a limitation in the overall design

3. Yes, keep using rolleyes to support your argument if you're bent on looking like a smart-ass... if you read my previous post (more carefully this time) I did not dismiss the P-40's durability as average, I described it as hardy. My point was that there were peers of the P-40 that were also hardy, some admittedly, more so.

4. I'd say the USAAF cared. The USAAF was The Customer (capitals intended), your argument MIGHT have worked in reverse; if the P-40Q had gotten there before the P-51, the speed differential might have been overlooked (but I'm by no means convinced).

5a. Your smoking habits are your business. So where would this P-40 of yours go? Send your top dog, the P-40Q wherever you like, the P-51 will turn up and do it better. The P-40 didn't serve in Europe because it wasn't deemed suitable, it wasn't considered a match for German fighters at the altitudes combat was expected to take place.

5b. And there you hit upon a very salient point; the P-51 was not designed as a long-range escort, there was sufficient potential in the design that it could evolve into the role and that's where the P-40 fell down, the P-40Q was the end of the evolutionary line and it still wasn't good enough

6. Commercially, you're talking production costs, I'm talking raw materials; even a country the size of the US had to allocate resources but while we're on the subject, it was cheapness that kept the P-40 in production long after obsolescence, not its ability.

7. Do you have any statistical data to support this?

8. Arguably indeed, explain

9. What do you mean?

10. It was fitted with one and it still wasn't walking or talking fast enough or high enough any more

11. Well sorry, but you did; you go on however to answer your own question, other types were prioritised over the P-40 - why do you suppose that was?

12. I wonder why the Army didn't think of that? Am I allowed to use rolleyes?


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## Amsel (Mar 17, 2009)

Erik Schilling wrote


> As early as September 1941 Chennault was teaching the AVG to
> hit and run, requiring speed, which was the P-40's forte against
> the Japanese. When properly used, the P-40 outclassed the Japanese
> Zero. It took the military 2 more years before they stumbling on
> ...





> The P-40B was. . .
> 40 mph faster than the AM6-2 (21) Zero.
> 50 mph faster than the Hyabusa, or Ki-43.
> 70 mph faster than the fixed gear I-96.
> ...


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## MikeGazdik (Mar 17, 2009)

This is a great thread, I have enjoyed reading every post.

If I may speak for Demetrious, I think I feel what he is getting at, because it is something I believe.

Nobody is suggesting to consider the P-40 when talking about aircraft in the league of the P-51, or Fw 190 or any late model top of the line fighter. 

But usually, even when considering only early war and pre war fighters, the Warhawk is overlooked or quickly dismissed. We are just trying to give it some love. And it is simply because the ONLY thing it lacked was the higher horsepower engine at altitude. It could manuever with the best of the early fighters, it had good firepower, overly stout construction, equal or better range, and decent load carrying ability. And as long is it was at 10 thousand feet or lower, its only disadvantage was climb performance. Obviously once it had to go to altitude the lack of power and power at altitude started to compound itself.

Because the U.S. was so fortunate to have many manufacturers and incredible internal competition, several aircraft were made that quickly outdated the Curtiss Warhawk. It would have been stupid to continue to push the P-40 when much better designs were available.

Because we are fans of the P-40, it is just fun to fantasize the possiblities if we were forced to primarily stick with our pre war fighter like Great Britain's Spitfire or Germany's Messerschmitt.

Demetrious, if I spoke words for you that you don't agree with, forgive me.


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## Colin1 (Mar 18, 2009)

MikeGazdik said:


> Nobody is suggesting to consider the P-40 when talking about aircraft in the league of the P-51, or Fw 190 or any late model top of the line fighter.
> 
> Because we are fans of the P-40, it is just fun to fantasize the possiblities if we were forced to primarily stick with our pre war fighter like Great Britain's Spitfire or Germany's Messerschmitt


Well OK
but the point I'm trying to make is why the P-40 came to the end of the line when it did and why it did. The P-40Q came as close to the P-51 as likely was possible and it still wasn't good enough.

The UK and Germany didn't stick with the Spitfire or the Bf109 series because they had to, both types were still competitive at war's end, implying development potential.

You're right, it's a great thread and I don't think there are any P-40 haters or deriders commenting in it but the dedicated fans of the type seem to be getting overly optimistic about what it was capable of.


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## tomo pauk (Mar 18, 2009)

Some disagreements with mr. Schilling's words:



> The P-40B was. . .
> 40 mph faster than the AM6-2 (21) Zero.
> 50 mph faster than the Hyabusa, or Ki-43.



Not really, it's some 10-20mph difference.



> 195 mph faster than the cruise speed of the Ki-21 Sally.



One should either compare cruising or max speed, not the max speed of one with cruise of another.



> P-40 was 5 mph faster than the Me 109 E-3 at 15,000 feet
> P-40 was 9 mph faster than the Spitefire Mk.IA at 15,000 feet
> The P-40 could out turn the Me. 109 E-3, and could out dive it.


1st: It's redicioulus to compare thw WWII planes that are two years apart. So, the P-40B shuld've been compared with Spit V and Bf-109Fs.
2nd: Mr. Schilling should compare the best max speed, not the one at the altitude that favoures the pet pony.


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## renrich (Mar 18, 2009)

Amsel, if Schilling asserts that the AVG mastered the Zero, I believe he is in error as I question if the AVG ever fought the Zero. I would be surprised if the P40, through 1943, was ever able to do better than break even against the A6M.


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## MikeGazdik (Mar 18, 2009)

Colin1 said:


> .
> 
> The UK and Germany didn't stick with the Spitfire or the Bf109 series because they had to, both types were still competitive at war's end, implying development potential..



You are right, and the only thing that kept them competitive was thier respective powerplants. Niether aircraft had great range, less so than the Warhawk if I remember correctly. Niether were great at hauling payloads for air to mud either. And that is the argument in a nutshell, IF the Warhawk was given an engine with the same capabilities as the Rolls Royce or Daimler, it would have made a world of difference.


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## Amsel (Mar 18, 2009)

renrich said:


> Amsel, if Schilling asserts that the AVG mastered the Zero, I believe he is in error as I question if the AVG ever fought the Zero. I would be surprised if the P40, through 1943, was ever able to do better than break even against the A6M.


I understand that. Members of the AVG loved their P-40's. The P-40 was prolific through much of the war and did quite well in capable hands. It's not the machine it's the man is what Schilling was essentially saying.


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## Amsel (Mar 18, 2009)

tomo pauk said:


> Some disagreements with mr. Schilling's words:
> 
> 
> 
> ...


I don't beleive Mr. Schilling is with us anymore. He was a military aviator from before WWII through Nam and knows his aircraft. I take alot stock in his writings as an lifelong aviator.


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## Clay_Allison (Mar 18, 2009)

Colin1 said:


> Well OK
> but the point I'm trying to make is why the P-40 came to the end of the line when it did and why it did. The P-40Q came as close to the P-51 as likely was possible and it still wasn't good enough.
> 
> The UK and Germany didn't stick with the Spitfire or the Bf109 series because they had to, both types were still competitive at war's end, implying development potential.
> ...


The development of the Allison lagged for some reason during a crucial period, causing the P-51 to be reengined, among other things. Why did it fall behind when it had been going since 1930, and had the best fuel in the world to experiment with? Was it just the war department being stupid about not wanting to develop better supercharging?

The penultimate version, -119, was as good as any of its final generation competitors, powering the P-82.


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## JoeB (Mar 18, 2009)

Amsel said:


> Erik Schilling wrote
> As early as September 1941 Chennault was teaching the AVG to
> hit and run, requiring speed, which was the P-40's forte against
> the Japanese. When properly used, the P-40 outclassed the Japanese
> ...


We have to distinguish the late Mr. Schilling's bravery in combat in 1940's from his analysis on the internet in 1990's-2000's: a lot of the latter was full of errors.

And he got a kind of irrational bug up his ass about Dan Ford after Ford wrote 'Flying Tigers' which compared AVG claims to losses given in pretty standard Japanese sources, which were of course considerably less. A lot of the AVG and their fans got really pissed about that, even though AVG claims were no *more* exaggerated than those of the Allied fighter units against the Japanese in 1942, in fact generally less exaggerated.

The Thach Weave and the weave the AVG did were not the same. Thach's manuever was pretty unique in fighter combat history actually. It wasn't just cooperating elements scissoring across each other's flight paths, but the elements flying far enough apart to meet each other *head on* as they crossed. Thach was inspired to invent new tactics based on reports on high effectiveness of Japanese fighters in China, but his concept otherwise had little to do with Chennault, and nothing to do with the AVG.

And as mentioned, the AVG never met Zeroes. The bulk of its fighter opponents were Type 97's, although it also did well in a smaller sample of combats with Type 1's later on (and it met a few Type 2's and Type 2 two seat fighters as well). But 100% of its opposition was JAAF, the JNAF withdrew its fighter units from China in the fall of the 1941 to concentrate its strength on the coming Pacific War, and none flew in Burma (where the AVG did most of its fighting) until a few in 1943.

Joe


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## Clay_Allison (Mar 18, 2009)

JoeB said:


> We have to distinguish the late Mr. Schilling's bravery in combat in 1940's from his analysis on the internet in 1990's-2000's: a lot of the latter was full of errors.
> 
> And he got a kind of irrational bug up his ass about Dan Ford after Ford wrote 'Flying Tigers' which compared AVG claims to losses given in pretty standard Japanese sources, which were of course considerably less. A lot of the AVG and their fans got really pissed about that, even though AVG claims were no *more* exaggerated than those of the Allied fighter units against the Japanese in 1942, in fact generally less exaggerated.
> 
> ...


One historical account of the Thach weave I read said that there were in fact other weaves prior to that, later called "Bastard Weaves" but that specific maneuver was unique to Thach.


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## HoHun (Mar 19, 2009)

Hi Tomo,

>Not really, it's some 10-20mph difference.

Here is my Pacific fighters speed comparison again ... it really depends on which exact P-40 model you pit against the A6M2.

(I'm not sure right now the P-40F ever served in the Pacific, but I included it in the comparison for some reason ... 

Regards,

Henning (HoHun)


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## Demetrious (Mar 19, 2009)

> Because we are fans of the P-40, it is just fun to fantasize the possiblities if we were forced to primarily stick with our pre war fighter like Great Britain's Spitfire or Germany's Messerschmitt.
> 
> Demetrious, if I spoke words for you that you don't agree with, forgive me.



No, you are spot-on. Us P-40 fans just like to point out that the P-40 was every bit as good as the Spitfire or Bf-109. It is simply that, unlike those other two fighters, it's country of origin produced new fighter types at a fantastic pace, so the P-40 never received the constant upgrades that kept the other airframes lethal performers right until the end of the war (again, like the Spitfire or Bf-109.) History likes to deride the P-40 as a weak and failed aircraft, and that's sad.



Colin1 said:


> You're deeper in 'schoolgirl with a new kitten' than you realise...



Ah, so you _are_ viewing my whole argument from the base assumption that I am a hopeless fanboy who is completely prepared to argue that the P-40 could whip the FW-190, the P-51, La-7, Jesus, and Optimus Prime all at the same time. 



> 1. Wiki's OK up to a point, don't labour under any illusions that it is a bible of any sort



The inadequacy of wikipedia is keenly felt here, as all it really says is "the P-40 was strongly built." Well, duh. I am left wanting for more detailed information.



> 2. I'd describe that as a bug in the overall design (which was resolved), rather than a limitation in the overall design



It wasn't resolved, since the thin NCA airfoil was key to the P-51's success. I wouldn't describe the superior performance granted by it a "bug" OR a "limitation," personally. I mean, the Hurricane's construction made it very durable, but I don't think anybody would say that made it a better ship then the Spitfire. The performance trade-off is significant. 



> 3. Yes, keep using rolleyes to support your argument if you're bent on looking like a smart-ass... if you read my previous post (more carefully this time) I did not dismiss the P-40's durability as average, I described it as hardy. My point was that there were peers of the P-40 that were also hardy, some admittedly, more so.



Which in turn implies that you thought I was saying the P-40 was alone in the durability class? When both the P-47 and Hurricane were superior? Again, you have made assumptions about my statements and my position.



> 4. I'd say the USAAF cared. The USAAF was The Customer (capitals intended), your argument MIGHT have worked in reverse; if the P-40Q had gotten there before the P-51, the speed differential might have been overlooked (but I'm by no means convinced).



No. No, no, no. The USAAF needed a _long-range escort fighter,_ that was the P-51. The P-40 was a great air superiority fighter AND had significantly better range then the Spitfire and Bf-109, but an 8 hour duration was out of the question. 

The P-40Q, IMO, was silly. The P-40E, with the simple addition of a 1500 horsepower Merlin or Allison engine, was all that was needed. 



> 5a. Your smoking habits are your business. So where would this P-40 of yours go? Send your top dog, the P-40Q wherever you like, the P-51 will turn up and do it better. The P-40 didn't serve in Europe because it wasn't deemed suitable, it wasn't considered a match for German fighters at the altitudes combat was expected to take place.



That's because air combat in the ETO for the USAAF consisted of high-altitude escort for the bombers. As I have already pointed out, that was not a role for the P-40 from the beginning. However, on the Eastern Front, the P-40 proved itself quite capable against the Me-109, and you still have the African theater, Italian theater, and Pacific Theater to consider. The P-40 could out-turn, out-roll, and out-dive the P-51. The P-51 was much faster and had much better performance in the vertical (a very important attribute in ACM,) but again, with the simple addition of the currently available Allison or Merlin engine with 1500 horsepower, the P-51s "dominant performance" in both those areas would have been reduced to an "edge." Then it would have been the P-40's significant manuverability advantage vs. the P-51s 50mph speed and moderate climb advantage. A wash, I'd say. The P-40 is the superior furballer, the P-51, the superior energy fighter. 



> 5b. And there you hit upon a very salient point; the P-51 was not designed as a long-range escort, there was sufficient potential in the design that it could evolve into the role and that's where the P-40 fell down, the P-40Q was the end of the evolutionary line and it still wasn't good enough



Neither could the Bf-109 or the FW-190 "evolve" into a extreme-long range escort. So the Bf-109, who's performance skyrocketed steadily from 1939 to 1945, remaining competitive to the end, was clearly the end of the evolutionary line and wasn't good enough!

To me, it is a testament to the amazing performance of the P-51 that a fighter built to do the near-impossible- achieve an 8 hour flight duration for long-rage escort- was _also_ capable of holding it's own in a dogfight. The Mustang was a unique ship in this regard. Just because another fighter couldn't achieve that kind of long range didn't make it clearly inferior, it just made it like _every other fighter plane in the world._



> 6. Commercially, you're talking production costs, I'm talking raw materials; even a country the size of the US had to allocate resources but while we're on the subject, it was cheapness that kept the P-40 in production long after obsolescence, not its ability.



It was only about 5 grand cheaper then the Mustang, which wouldn't have been enough to forgive higher combat losses or poorer kill ratios. 



> 7. Do you have any statistical data to support this?



That's fairly common knowledge, you know. 



> 8. Arguably indeed, explain



It could absorb ground fire much better, a very important attribute for ground-attack.

On the other hand, the P-51 could haul twice the payload (2,000lbs to the P-4os 1,000.) Oh, wait, with a proper engine the P-40 could have matched that, too.



> 9. What do you mean?



Performance in "the vertical" is a very important element of ACM. Basically, if an airplane can't turn OR roll worth a damn, but it can climb like a rocket, it can still dominate a fight. This is because it can simply climb away from a target on it's six, loop over, and dive on the enemy, blasting away from an angle the enemy can't match because it can't climb well enough to put it's guns on target. 

Versus another airplane with good vertical performance, you can easily get a "turn-fight" that takes place in the vertical. 

Now, the P-40s weak engine left it _crippled_ in the vertical. Where another plane could climb to meet a diving enemy (as Bockle said one must as far back as 1918,) the P-40 could not. That meant that many enemy planes- most notably the Bf-109- that were inferior in every other aspect (roll, turn, dive,) could still wage a good fight. 

The addition of sufficient power to the P-40 would have corrected it's one and only vice. It would not have made it _dominant_ in that arena, but simply made it adequate enough that it would not be an easily exploited weakness. 



> 10. It was fitted with one and it still wasn't walking or talking fast enough or high enough any more



For long range bomber escort and that only.



HoHun said:


> Here is my Pacific fighters speed comparison again ... it really depends on which exact P-40 model you pit against the A6M2.



Having tried this extensively in a few good simulators flying both the A6M and the P-40, and from what I've read on ACM, I think what made the P-40 a better energy fighter is simply that it retained energy much better then the A6M Zero. 

Most air combat, of course, does not take place at the maximum airspeed. In fact it can take several minutes of acceleration for a WWII fighter to reach it's maximum speed for it's altitude, and energy is rapidly bled off in violent maneuvers. Now, the A6M could accelerate faster, replacing that lost energy better, but the P-40 could keep more of it in the first place through violent maneuvers. Simply put, the P-40s higher mass gave it more inertia, and that, plus it's somewhat cleaner profile then the light, radial-engined A6M, let it keep a higher energy state once it had entered a fight. (I think inertia is the right term- if I'm wrong, feel free to correct me.) This same principle is why the P-47 could zoom climb faster then anything in the air.

As far as I can tell, the P-40s superior energy retention is what was really significant. The speed advantage was just icing on the cake.


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## Marshall_Stack (Mar 19, 2009)

This might be a stupid question, but what is ACM?


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## renrich (Mar 19, 2009)

ACM is air combat maneuvering, a modern term. One has to be really enthusiastic to believe the P40 was the equal of the Spit and 109. The Spit and 109 are two of the classic designs of fighters in world history. The P40 might be underappreciated, but was hardly classic. It was too heavy, not very clean and based on results was probably not equal to the Wildcat in ACM, which hardly qualifies it for greatness. In air to ground it was probably better than the 109 or Spit but once the bombs were dropped and it had to defend itself, it was at a disadvantage. There was a good reason the P40 did not get into the fight in the ETO.


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## Colin1 (Mar 19, 2009)

...I am a hopeless fanboy who is completely prepared to argue that the P-40 could whip the FW-190, the P-51, La-7, Jesus, and Optimus Prime all at the same time. 
*Oh God, not another one...* 

It wasn't resolved, since the thin NCA airfoil was key to the P-51's success. I wouldn't describe the superior performance granted by it a "bug" OR a "limitation," personally. 
*Are you actually bothering to read my responses or are you inadvertently answering questions from another forum? It WAS resolved, the wing's chord was thickened so that the guns could sit upright. This negated stoppages incurred as a result of high-torsion manoeuvres and who said the superior performance was the "bug" OR "limitation"? *

I mean, the Hurricane's construction made it very durable, but I don't think anybody would say that made it a better ship then the Spitfire. The performance trade-off is significant.
*Bit of a tangent but I don't think anyone is arguing with you there; trade-off is significant, yes - it always is. Can you see from your own case point how and why the Hurricane came to a dead-end after the Battle of Britain whilst the Spitfire kept developing right up until the end of the war? Development potential. If not for precisely the same reasons, that's what happened to the P-40.*

Which in turn implies that you thought I was saying the P-40 was alone in the durability class? When both the P-47 and Hurricane were superior? Again, you have made assumptions about my statements and my position.
*Hey! Who's the one making assumptions here!? I didn't imply anything, I answered your original claim that the P-40 had 'insane' structural strength with the consideration that its peers too, could take some! 
The P-40 was structurally a strong aircraft but only within the context of US fighter design philosophy - strength, speed and firepower ie it was a robust fighter in a whole inventory of robust fighters.*

No. No, no, no. The USAAF needed a _long-range escort fighter,_ that was the P-51. The P-40 was a great air superiority fighter AND had significantly better range then the Spitfire and Bf-109, but an 8 hour duration was out of the question.
*You can almost guess what's coming; Yes, Yes, Yes, Yes. On 29May40 the USAAF didn't even know they needed a P-51 (presumably you understand the significance of that date); it was to utilise the same Allison employed by the P-40. Greater minds than ours at the time realised they could attempt to improve the P-40 or try and come up with something better; given the exact same engine, they did. Long-range escort came later and I don't believe even NAA saw that coming, the P-51 simply had the development potential to evolve into the role. You show me where in NA-73 it stipulates long-range escort capability.*

The P-40Q, IMO, was silly. The P-40E, with the simple addition of a 1500 horsepower Merlin or Allison engine, was all that was needed. 
*Silly? In your opinion? Can you qualify your opinion with slightly more than 'it was silly'? If the P-40F and L weren't good enough with the Packard Merlin fitted, why do you think the P-40E would have fared any better?*

As I have already pointed out, that was not a role for the P-40 from the beginning
*The P-40 was requiremented and designed pre-war, it was envisaged that engagements would take place at low level; when the war started aircraft development picked up the pace and the US realised that the P-40 wasn't really what they needed any more.*

However, on the Eastern Front, the P-40 proved itself quite capable against the Me-109
*The Luftwaffe hit the Soviets hardest low down, guess what the P-40 was designed for? (see above)*

A wash, I'd say. The P-40 is the superior furballer, the P-51, the superior energy fighter.
*Unbelievable. Do you really think a P-51 pilot, sitting on his 50mph speed advantage is going to furball with a furballer? He's going to use his superior energy to run through him and bite lumps off him. *

Neither could the Bf-109 or the FW-190 "evolve" into a extreme-long range escort. 
*Yes, quite; you see, that's the difference between interceptors and long-range escort fighters...*

So the Bf-109, who's performance skyrocketed steadily from 1939 to 1945, remaining competitive to the end, was clearly the end of the evolutionary line and wasn't good enough!
*I've no idea what you just said there*

To me, it is a testament to the amazing performance of the P-51 that a fighter built to do the near-impossible- achieve an 8 hour flight duration for long-rage escort- was _also_ capable of holding it's own in a dogfight. The Mustang was a unique ship in this regard. Just because another fighter couldn't achieve that kind of long range didn't make it clearly inferior, it just made it like _every other fighter plane in the world._
*It wasn't built to do that, it was - quite mundanely - on Britain's shopping list for hardware in the face of by now, inevitable war with Germany. Nobody then even dreamed it would be escorting thousand-bomber raids to Berlin and back in 6 hour flights.*

That's fairly common knowledge, you know.
*Let's imagine for a minute that it isn't... *

It could absorb ground fire much better, a very important attribute for ground-attack.
*OK, ground attack, that's one attribute of 'multi-role', what about the rest?*

On the other hand, the P-51 could haul twice the payload (2,000lbs to the P-4os 1,000.) Oh, wait, with a proper engine the P-40 could have matched that, too.
*and where on the wings would you strap 2,000lbs of ordnance to a P-40?*

That meant that many enemy planes- most notably the Bf-109- that were inferior in every other aspect (roll, turn, dive,) could still wage a good fight. 
*I've a feeling you'll be hearing on this one...*

Having tried this extensively in a few good simulators flying both the A6M and the P-40, and from what I've read on ACM, I think what made the P-40 a better energy fighter is simply that it retained energy much better then the A6M Zero. 
*I'm not sure about that, although not certain I'm pretty sure that chin radiator arrangement didn't make the P-40 the most energy-conscious of fighters*

As far as I can tell, the P-40s superior energy retention is what was really significant. The speed advantage was just icing on the cake.
*Well, I'm still not so sure about this whole energy-retention issue but I'd describe a speed advantage as a little more than icing on the cake, it was usually the difference between going home and not going home.*


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## tomo pauk (Mar 19, 2009)

Amsel said:


> I don't beleive Mr. Schilling is with us anymore. He was a military aviator from before WWII through Nam and knows his aircraft. I take alot stock in his writings as an lifelong aviator.



My post was not meant as insult/attack to the man that can't defend himself, so I'd like to repeat JoeB's words:


> We have to distinguish the late Mr. Schilling's bravery in combat in 1940's from his analysis on the internet in 1990's-2000's: a lot of the latter was full of errors.


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## tomo pauk (Mar 19, 2009)

Hi Henning,

The difference, according to your graph, is indeed 25mph*, so not far away from what I've said. 

*P-40B faster then both Zeke Oscar by that margin.


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## drgondog (Mar 19, 2009)

Colin - although I agree your points in the prior post, the P51B/C/D/K all had the same wing (NACA/NAA 45-100) with one exception. The root chord was extended on the D/K to give a little more structural strength at the root and a little more room for the Wheel and a slightly different door cover. The effect of lengthening the root chord would have had the effect of increasing very slightly the maximum thickness from root to the point where the swept portion intersected with the leading edge of the rest of the wing.

At that point the thickness and space available for the guns and planform of the wing are exactly the same for A-K models.

The A,B,C all had space to insert one more M3 in the same bay as the paired .50's and curiously had the ability to mount the guns vertically - as they were in the D/K/H/P-82

The H (and G,J) had a slightly different wing with just a little camber in addition to a slight difference in thickness at root and tip.

IIRC the primary root causes for the jams were lubricant freezing for both the 50's and the feed belt boost motor when the heater failed to operate properly. The High G turns also contributed to feeding issues and jams - mostly resolved with the upright M3's and a better heater.

The Fighter Group Armorers also developed better QC processes for sorting unlinked ammo and then linking them in the June 1944 timeframe. 

Regards,

Bill


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## Colin1 (Mar 19, 2009)

drgondog said:


> Colin - although I agree your points in the prior post, the P51B/C/D/K all had the same wing (NACA/NAA 45-100) with one exception. The root chord was extended on the D/K to give a little more structural strength at the root and a little more room for the Wheel and a slightly different door cover. The effect of lengthening the root chord would have had the effect of increasing very slightly the maximum thickness from root to the point where the swept portion intersected with the leading edge of the rest of the wing


Hi Bill
thanks for that, interesting
My bad, I thought the wing was both thickened (the jamming issue) and strengthened to take hard points and the combination of changes were the reason flight commanders were crying 'foul' once they realised their flights (still in Bs and Cs) were 3-5mph faster than they were.

Thanks for that, I'll do the homework on it.


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## renrich (Mar 19, 2009)

As was mentioned before, the H81(P40B) was the fastest of all P40s produced although not many were built. It was not really war ready so comparing it to operational Zekes is not really appropriate. According to Lundstrom, Thach worked out his beam defense maneuver(Thach weave) at home on the dining room table with match sticks. The USN got reports if memory serves on the Zeke in October 1941.


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## drgondog (Mar 19, 2009)

Demetrious said:


> The P-40 was a great air superiority fighter AND had significantly better range then the Spitfire and Bf-109, but an 8 hour duration was out of the question.
> 
> The P-40Q, IMO, was silly. The P-40E, with the simple addition of a 1500 horsepower Merlin or Allison engine, was all that was needed.
> 
> ...



Can you offhand cite an opponent the P-40 faced in 1943 (and beyond) which had Less Energy? I can't, but am sure wasn't a contemporary F190, Me 109, A6M, etc? IFAIK the p-40 was reasonably close to 1:1 vs the LW in Africa as most of the battles were at low altitude where a P-40 might be able to contain the fight to the horizontal but it did not do well against the LW in USSR and certainly not against IJN Zero's.


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## drgondog (Mar 19, 2009)

Colin1 said:


> Hi Bill
> thanks for that, interesting
> I thought the wing was both thickened (the jamming issue) and strengthened to take hard points and the combination of changes were the reason flight commanders were crying 'foul' once they realised their flights (still in Bs and Cs) were 3-5mph faster than they were.
> 
> Thanks for that, I'll do the homework on it.



Mustang by Gruenhagen is the best single source, Mustang Designer by Wagner is also good but more about Schmeud but does touch on many design issues.

I thought at one time that the H had a slightly Thinner wing (NACA 66-(1.8) 15.5 root) but I researched it more and it actually had a 15.5/12% thickness at Root/tip whereas the 51A-K (NAA/NACA 45-100) had 15.1/11.4% at root/tip.


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## Colin1 (Mar 19, 2009)

drgondog said:


> Mustang by Gruenhagen is the best single source, Mustang Designer by Wagner is also good but more about Schmeud but does touch on many design issues.
> 
> I thought at one time that the H had a slightly Thinner wing (NACA 66-(1.8) 15.5 root) but I researched it more and it actually had a 15.5/12% thickness at Root/tip whereas the 51A-K (NAA/NACA 45-100) had 15.1/11.4% at root/tip.


Thanks Bill
drop the ISBNs by when you have time


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## renrich (Mar 19, 2009)

I think that the best thing the P40 had going for it was that it was available and operational when the war for the US began. In spite of it's short comings it could give a decent account of itself if used with it's strengths in mind but, in spite of all Curtis's efforts it just did not have much "stretch." It was in action on the 7th of December, 1941 and it soldiered on under many flags until the end. It and the Wildcat had similar careers and probably deserve the sobriquet supposedly from Darrell Royal, "ole ugly is better than ole nothing."


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## drgondog (Mar 19, 2009)

Colin1 said:


> Thanks Bill
> drop the ISBNs by when you have time



CCN 78-93504 and SBN 668-02079-2

isbn 0-517-56793-8 for Mustang Designer


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## tomo pauk (Mar 19, 2009)

renrich said:


> I think that the best thing the P40 had going for it was that it was available and operational when the war for the US began. In spite of it's short comings it could give a decent account of itself if used with it's strengths in mind but, in spite of all Curtis's efforts it just did not have much "stretch." It was in action on the 7th of December, 1941 and it soldiered on under many flags until the end. It and the Wildcat had similar careers and probably deserve the sobriquet supposedly from Darrell Royal, "ole ugly is better than ole nothing."



Amen.


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## imalko (Mar 19, 2009)

renrich said:


> I think that the best thing the P40 had going for it was that it was available and operational when the war for the US began. In spite of it's short comings it could give a decent account of itself if used with it's strengths in mind but, in spite of all Curtis's efforts it just did not have much "stretch." It was in action on the 7th of December, 1941 and it soldiered on under many flags until the end. It and the Wildcat had similar careers and probably deserve the sobriquet supposedly from Darrell Royal, "ole ugly is better than ole nothing."



I agree.

I have read somewhere that "P-40 was a useful fighter rather than outstanding" and that "it was available in numbers exactly when it was needed". (At the beginning of the war for the US that is.) 

I think that's about sums it up.


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## Amsel (Mar 19, 2009)

imalko said:


> I agree.
> 
> I have read somewhere that "P-40 was a useful fighter rather than outstanding" and that "it was available in numbers exactly when it was needed". (At the beginning of the war for the US that is.)
> 
> I think that's about sums it up.



Except the P-40n was not available in the beginning of the war and it was the most prolific of all the models.


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## Colin1 (Mar 20, 2009)

drgondog said:


> ...the P51B/C/D/K all had the same wing (NACA/NAA 45-100) with one exception. The root chord was extended on the D/K to give a little more structural strength at the root...
> 
> At that point the thickness and space available for the guns and planform of the wing are exactly the same for A-K models.
> 
> The A,B,C all had space to insert one more M3 in the same bay as the paired .50's and curiously had the ability to mount the guns vertically - as they were in the D/K/H/P-82


Ha! I've just re-read my post
I did indeed say chord, I meant thickness - not that it matters if that didn't change either


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## drgondog (Mar 20, 2009)

Colin1 said:


> Ha! I've just re-read my post
> I did indeed say chord, I meant thickness - not that it matters if that didn't change either



The change in root chord length for the D from the A/B would have the effect of increasing very slightly the actual thicknes of that section of the wing over the shorter chord of the B (but not the %) from the root chord to the wing station where it blended in with the rest of the leading edge just inboard of the first machine gun... 

from that point outboard the airfoil/chord/thickness is exactly the same for A/B/C/D/K all the way to the tip.


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## Elvis (Mar 22, 2009)

I didn't see anyone else address this particular question (apologies if you did and I overlooked your response), so I'd like to take a stab at it, as I believe understanding the powerplant is essential to understanding why the P-40 (and the early 51's) are remembered in the way that they are.



Clay_Allison said:


> The development of the Allison lagged for some reason during a crucial period, causing the P-51 to be reengined, among other things. Why did it fall behind when it had been going since 1930, and had the best fuel in the world to experiment with? Was it just the war department being stupid about not wanting to develop better supercharging?
> 
> The penultimate version, -119, was as good as any of its final generation competitors, powering the P-82.


Clay, 

You have to remember is that the Allison was originally designed as an _airship_ powerplant.
Used in that fashion, it would be treated almost like a generator powerplant, in that it would see hours and hours of "steady state" crusing, without a whole lot of fluctuation in engine speed.
This means it doesn't have to be built as "stout" as an engine that would see a lot of wide ranging variences in throttle settings over a short period of time, which can be very stressful on an engine.
I believe this is one reason why the Allison was about 300-400 lbs. lighter than the Merlin, even though it displaced an extra 60 cubes.
Granted, it ended up being developed into quite a usable mill, almost too late to make a difference in the war, the development was most likely slow due to the fact I stated above, compounded by the fact that the British already had a suitable powerplant that was ready to go....and they were more than happy to let us use it.
Here's something else:
A few years ago, I traded some E-mails with a guy who used to crew on some Unlimited Hydroplanes during the 1970's, an era where literally all of those boats were powered by either an Allison or a Merlin V-12.
He told me that, although he didn't know exactly why, the mechanics could ALWAYS pull more power out of the Merlin than the Allison. 
This eventually led to the favouring of the Merlin, and later the Rolls Griffon, in most Unlimited's towards the end of the "piston engine" era.
It was just the way those engines were set up from the get-go.
...I suspect, to some degree, that was because of the more stout design of the Merlin, too.

Still, that being said (and I hope that answers your question), I would've still liked to have seen the P-40N and the P-51 B/C's outfitted with an Allison fitted with a single stage, two-speed, _intercooled_ supercharging system featuring impeller size in the 12" to 15" range, and a better prop for high altitude work (of course, this means that the "G" motor would've had to come to fruition more quickly than it did).
Anyway, I think this would've improved the upper altitude performance of both planes and while I think the 51, at least, would've eventually found itself mated with the Merlin, that particular event would've probably happened later, AND, the P-40 might be remembered as a more favourable match to the 109, the Zero and the Tony.
--------------------------------------------------

One more thing....

I saw quite a few references from someone about the P-40Q in particular.

Wasn't that one a one-off experimental version that was built at the behest of the P-40's designer, to show how "equal" it was to a similarly outiftted 51? 
(I think the P-51D was the model being compared to, at that time)

The jist I got from those posts were that the "Q" version was built in number and implemented into the war effort, which is not how I understand it.

Am I wrong? Please enlighten me.


Elvis


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## Vincenzo (Mar 22, 2009)

From Baugher page
"The proposed production models of the P-40Q were to have carried either six 0.50-inch machine guns or four 20-mm cannon, but the XP-40Q was still inferior to contemporary production Mustangs and Thunderbolts, and development was therefore abandoned. Consequently, the production life of the P-40 ended with the N version."


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## Elvis (Mar 22, 2009)

Thanks Vincenzo, that's what I thought.



Elvis


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## Demetrious (Mar 23, 2009)

Colin1 said:


> ...I am a hopeless fanboy who is completely prepared to argue that the P-40 could whip the FW-190, the P-51, La-7, Jesus, and Optimus Prime all at the same time.
> *Oh God, not another one...*



... I'm going to assume you're being funny here, because if you _actually_ missed the "your base assumption is" part preceding that, then you make me sadface, sir.



> Can you see from your own case point how and why the Hurricane came to a dead-end after the Battle of Britain whilst the Spitfire kept developing right up until the end of the war? Development potential. If not for precisely the same reasons, that's what happened to the P-40.[/B]



I've seen that comparison made before- I know percisely where you're coming from- but I'm not so sure it's an accurate one. Simply put, I don't know if it's fair to regulate the P-40 to the same era of out-dated aircraft that the Hurricane belonged to. I personally think the P-40 had more potential then it was given credit for.



> *Hey! Who's the one making assumptions here!?*


*

Fair 'nuff!

You show me where in NA-73 it stipulates long-range escort capability.

Perhaps not long range escort, but long range, certainly. I'd wager that simply because the short range of the Spitfire was very limiting, so the British request for a new aircraft would likely include better range. This is interesting, in fact, because the P-51 came about as a direct result of the British trying to buy P-40s. As Wikipedia says:



Wikipedia said:



North American Aviation (NAA) was already supplying their Harvard trainer to the RAF, but were otherwise underutilized. NAA President "Dutch" Kindelberger approached Self to sell a new medium bomber, the B-25 Mitchell. Instead, Self asked if NAA could manufacture the Tomahawk under license from Curtiss.Kindelberger replied that NAA could have a better aircraft with the same engine in the air in less time than it would take to set up a production line for the P-40.

Click to expand...


Earlier in the article it says that the only American aircraft that came close to what the RAF purchasing commission required was the P-40. I'd wager that a good range was part of that requirement. 

In any case, though, the fact that North American Aviation chose to develop the P-51 rather then build P-40s is a direct vindication of your insistence that the P-51 was a generation above the P-40. Nobody disputes that, certainly. I just think that the P-40 had much potential then most people give it credit for, and the reason it wasn't fully realized is that the American war machine was going all out- current fighters were being built and upgraded even as several new designs were being built. America had more resources available in terms of production lines and such then Germany, or England. If Germany had had the resources, they would have thrown all their resources into building FW-190s and 190Ds instead of continuing to upgrade the Bf109, but it was easier to upgrade a proven design then work out the kinks in an entirely new one. 




Silly? In your opinion? Can you qualify your opinion with slightly more than 'it was silly'? If the P-40F and L weren't good enough with the Packard Merlin fitted, why do you think the P-40E would have fared any better?

Click to expand...


The P-40Q, as others have just pointed out, was an attempt to make the P-40 into a clone of the P-51, which it would never, ever be. The P-40 just didn't have it in it to be a high-altitude high speed fighter. However, simply adding a decently powerful powerplant to an already proven design would have improved it's usefulness drastically for very little invested in R&D costs- and time, always a crucial factor when you need every fighter at the front right away. After all, the Curtiss factory was going all-out even as the P-51 was entering production. Now, the P-39D2, in 1941, had a 1600 horsepower Allison V-1710-63 engine in it, a massive improvement over the 1100 horsepower Allison it had before. The P-40E of the same era only had the Allison V-1710-39, with an anemic 1150HP. Why couldn't they get the Allison -63 into the P40? Does anybody know the reason? 




The P-40 was requiremented and designed pre-war, it was envisaged that engagements would take place at low level; when the war started aircraft development picked up the pace and the US realised that the P-40 wasn't really what they needed any more.

Click to expand...


Dude. The FW-190, with it's radial engine, was a poorer high-altitude performer then the Bf-109. And yet, the 190 was preferred because most dogfights took place below 15,000 feet, where the 190 was superior. 

The US needed a high-altitude fighter to escort the bombers, the P-51 excelled here. In every other theater, low-altitude fighting was the norm- for example, Italy and Africa. 

And consider that Luftwaffe pilots found that the Mustangs performance advantages were only at altitude, and that they disappeared the closer to the ground you got. 




Unbelievable. Do you really think a P-51 pilot, sitting on his 50mph speed advantage is going to furball with a furballer? He's going to use his superior energy to run through him and bite lumps off him. 

Click to expand...


Yes. Yes, I know, hence my anecdote about the Aces High Spitfire pilots who moan and demand the P-51s come furball with them (to my infinite amusement.) 

But that doesn't mean for one second that the energy fighter (in this case, the P-51) could dominate the fight. The Mustang could be a thousand yards away before the P-40 could turn to face him, but that also means that the P-40 will always have plenty of time to get his nose on target with the P-51 for the next pass. In this case, the fight degenerates into a series of head-on passes, and that's not good. You've got a 50/50 chance of coming out on top, even if you have better guns- and that's just a wash. 




Yes, quite; you see, that's the difference between interceptors and long-range escort fighters...

Click to expand...


But gee, I thought you said that the P-51 was never originally designed to be a long-range escort fighter! But it had the potential to grow into a long-range fighter, and the 190 didn't. 

Therefore, by your logic, both the 109 and 190 were obsolete. 




I've no idea what you just said there

Click to expand...


The Bf-109s performance increased impressively throughout the war. The Bf-109 "Emil," that fought the Battle of Britain, turned 360 degrees in 24 seconds and had 1,000 HP to work with. By 1942, the "Gustav" Bf-109 had 1400 HP and could turn 360 degrees in only 20 seconds. Later war models had even better performance. 

There's some debate on that, since German engineers loaded the aircraft down with hundreds of pounds of extra weight as the design advanced, with negated some of the advantage it could have gained from the power upgrades. In the end though, the late Bf-109s had marked performance increases over the first ones. 

(post too long, continued below)*


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## Demetrious (Mar 23, 2009)

> *It wasn't built to do that, it was - quite mundanely - on Britain's shopping list for hardware in the face of by now, inevitable war with Germany. Nobody then even dreamed it would be escorting thousand-bomber raids to Berlin and back in 6 hour flights.*



I guess this would depend on how much different the A-model mustangs were from the D-models that went into Germany.



> *Let's imagine for a minute that it isn't... *



Let me guess, unless I can dig up extensive technical documents or pilot accounts comparing the durability of the P-40 to the P-51, you're going to cry foul? 

No. Even after extensive googling I'm unable to find even maximum g-limits for the P-51 OR the P-40. Even the basic data is hard to find, much less esoteric information comparing the number of wing spars. I know the P-40 had five wing spars, but I cannot even find that data for the P-51. The best I have is a desktop made from a promotional poster for the P-51 that shows a wing cross-section in which it appears that the P-51B only has two wing spars. (If anybody wants that desktop, holler- it's a nice one.)

Somebody here might be able to find that data, but it's not me. If the general consensus in the literature that the P-40 was more durable then the P-51 isn't good enough for you, then too bad. (And I mean this honestly, because pilot anecdotes often ARE not good enough! But the simple fact is that this data is just very, very hard to find. It really _is_ too bad.  )



> *OK, ground attack, that's one attribute of 'multi-role', what about the rest?*



Are you really going to argue that the P-51 was a better low-altitude fighter then the P-40? When the P-40 could out-turn and out-roll the P-51, and the P-51's speed advantage was slimmest on the deck? 

In any case, I find it very interesting that the P-51 actually _was_ deployed as a purpose-built fighter bomber- the A-36! It was used in North Africa, and was basically a P-51B with dive brakes. By all accounts, they fared quite well. This demonstrates, I think, that the P-51 wasn't a _bad_ low-altitude fighter- it's just that the Pony does a lot better at altitude. On the deck it's equal, at 30,000 feet it shines. 



> *and where on the wings would you strap 2,000lbs of ordnance to a P-40?*



Actually, Wikipedia says that the P-40E could carry two-thousand pounds of ordinance, and had two wing hardpoints, which was news to me. Wikipedia seems to have it's cites in order on this article, but I remain skeptical. 



> That meant that many enemy planes- most notably the Bf-109- that were inferior in every other aspect (roll, turn, dive,) could still wage a good fight.
> *I've a feeling you'll be hearing on this one...*



Yes, I eagerly await the rest of the forum telling me how an excellent power to weight ratio is not tremendously useful.  



> *I'm not sure about that, although not certain I'm pretty sure that chin radiator arrangement didn't make the P-40 the most energy-conscious of fighters*



It wasn't the cleanest ship, not by a long shot- but it WAS a superior energy fighter to the Zero, only because the Zero was a very dirty ship with that big radial, and was so very light. Against pretty much every other fighter of the war, the P-40 was a furballer- slow, but manuverable. The Zero is the only exception, because the Zero was right on the extreme end of the scale.



> Well, I'm still not so sure about this whole energy-retention issue but I'd describe a speed advantage as a little more than icing on the cake, it was usually the difference between going home and not going home.[/B]



Yep, that's what I've been saying. In the actual engagement, if one chose to stay and fight, the energy retention was the deciding factor, but if you want to flat out run for it, yeah, it's decisive. 



drgondog said:


> Can you offhand cite an opponent the P-40 faced in 1943 (and beyond) which had Less Energy? I can't, but am sure wasn't a contemporary F190, Me 109, A6M, etc? IFAIK the p-40 was reasonably close to 1:1 vs the LW in Africa as most of the battles were at low altitude where a P-40 might be able to contain the fight to the horizontal but it did not do well against the LW in USSR and certainly not against IJN Zero's.



Zeros. The Zero would _enter_ the fight at the same speed but with less energy, since it was a much lighter plane, and thus had less mass. Once the fight commenced, the P-40 could hold it's energy rather better. 

Against everything else, as you say, the P-40 had significantly less energy then the Bf-109 (which had awesome power-weight, really. Try it in a simulator sometime- you give that baby the gas and she just _steps-_) and the 190. The P-40 could dominate the 109 in a scissors or turn fight, but could never catch it. A better engine would have reduced that single deficiency nicely and really given the 109 trouble, even more then it did historically. The 190 had the P-40 in roll rate, on the other hand, the 190's power-weight wasn't as good. This didn't matter, though, because it was still leagues ahead of the P-40s anemic engine. As you say, victory really depended on forcing a horizontal fight, and that was best achieved by diving to the deck and dueling there.


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## Vincenzo (Mar 23, 2009)

P-40K has a similar engine of P-39D-2 (1600 hp is wrong i think), and its performance are similar to P-40E


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## Colin1 (Mar 23, 2009)

... I'm going to assume you're being funny here, because if you actually missed the "your base assumption is" part preceding that, then you make me sadface, sir.
*Not THAT funny, I don't recall Jesus ever flying a P-40 but you might want to consider that line of response could well be offensive to any number of members on here.*

I've seen that comparison made before- I know precisely where you're coming from - but I'm not so sure it's an accurate one. Simply put, I don't know if it's fair to regulate the P-40 to the same era of out-dated aircraft that the Hurricane belonged to. I personally think the P-40 had more potential then it was given credit for.
*Whether it's fair or otherwise, the P-40 belonged to the same mid-30s-designed range of fighters that the Hurricane belonged to. You will need to spell out exactly why you think the P-40 had more potential that it was given credit for and it won't do you any good trotting out the 'fit it with a Merlin' argument again - we've already shown you that in the P-40F and L it didn't exactly light the plane up.*

...because the P-51 came about as a direct result of the British trying to buy P-40s. As Wikipedia says:

Originally Posted by Wikipedia 
North American Aviation (NAA) was already supplying their Harvard trainer to the RAF, but were otherwise underutilized. NAA President "Dutch" Kindelberger approached Self to sell a new medium bomber, the B-25 Mitchell. Instead, Self asked if NAA could manufacture the Tomahawk under license from Curtiss.Kindelberger replied that NAA could have a better aircraft with the same engine in the air in less time than it would take to set up a production line for the P-40.
*But don't you see why that damns your argument? Why did Kindleberger suggest something better (that didn't even exist yet!) if the P-40 had so much development potential left in it?*

Earlier in the article it says that the only American aircraft that came close to what the RAF purchasing commission required was the P-40. I'd wager that a good range was part of that requirement.
*I'd wager the other part was the lack of anything else to choose from; you can come close just by being the best of a bad bunch...*

I just think that the P-40 had much potential then most people give it credit for, and the reason it wasn't fully realized is that the American war machine was going all out- current fighters were being built and upgraded even as several new designs were being built. America had more resources available in terms of production lines and such then Germany, or England. If Germany had had the resources, they would have thrown all their resources into building FW-190s and 190Ds instead of continuing to upgrade the Bf109, but it was easier to upgrade a proven design then work out the kinks in an entirely new one.
*We've yet to nail this elusive potential of yours...
I don't really see anything that provides any new clarity in the rest of the piece in fact, I'd say it rambles a bit*

The P-40Q, as others have just pointed out, was an attempt to make the P-40 into a clone of the P-51, which it would never, ever be. The P-40 just didn't have it in it to be a high-altitude high speed fighter. However, simply adding a decently powerful powerplant to an already proven design would have improved it's usefulness drastically for very little invested in R&D costs- and time, always a crucial factor when you need every fighter at the front right away. After all, the Curtiss factory was going all-out even as the P-51 was entering production. Now, the P-39D2, in 1941, had a 1600 horsepower Allison V-1710-63 engine in it, a massive improvement over the 1100 horsepower Allison it had before. The P-40E of the same era only had the Allison V-1710-39, with an anemic 1150HP. Why couldn't they get the Allison -63 into the P40? Does anybody know the reason?
I don't think anyone pointed that out.
*The XP-40Q had a -121 Allison with two-speed supercharging and water injection good for around 1430hp - I'd call that a decently powerful powerplant. I'm not really sure what the rest of this piece is trying to tell me either.*

Dude. The Fw190, with its radial engine, was a poorer high-altitude performer than the Bf109. And yet, the 190 was preferred because most dogfights took place below 15,000 feet, where the 190 was superior
*At the time of the Fw190's introduction to the ETO it was pasting Spitfire Vs left, right and centre. The RAF was getting kicked in the teeth. It wasn't until the introduction of the Spitfire IX that they had a hope of engaging the Fw190 on something like level terms, or not, if they chose to remain at altitude. The 190, unlike the P-40, was able to develop into something that could redress the balance and kept developing until the end of the war. This is the train that you keep missing, development potential - the P-40 didn't have alot of it*

And consider that Luftwaffe pilots found that the Mustangs performance advantages were only at altitude, and that they disappeared the closer to the ground you got
*That's still not a good enough reason to keep the P-40*

But that doesn't mean for one second that the energy fighter (in this case, the P-51) could dominate the fight. The Mustang could be a thousand yards away before the P-40 could turn to face him, but that also means that the P-40 will always have plenty of time to get his nose on target with the P-51 for the next pass. In this case, the fight degenerates into a series of head-on passes, and that's not good. You've got a 50/50 chance of coming out on top, even if you have better guns- and that's just a wash.
*Fighter comparisons are usually made with all things being equal eg both at same altitude, both at their optimal cruising speed, both pilots see each other at the same time etc etc. The P-51 could be a thousand yards away before... yes and by that standard of comparison the P-40 could be tucked underneath the P-51 in his blind spot and gun him down before the P-51 knew what hit him. There are countless instances where a P-40 could shoot down a P-51 but my money's still on the P-51.*

But gee, I thought you said that the P-51 was never originally designed to be a long-range escort fighter! But it had the potential to grow into a long-range fighter, and the 190 didn't. Therefore, by your logic, both the 109 and 190 were obsolete. 
*That wasn't my logic at all (and alot of your argument seems to centre around this technique; I have to search my previous posts trying to figure out which of my responses you are countering). I did say that and I maintain that argument, it wasn't originally designed for that. But here comes that term again development potential - the P-51 evolved into the role. Pure interceptors on the other hand are simply the smallest possible airframe wrapped around the biggest possible engine, not alot of room for internal, range-extending fuel.
Neither the 109 nor the 190 series were obsolete and continued to be a headache for Allied escort pilots up until the end of the war.*


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## Colin1 (Mar 23, 2009)

I guess this would depend on how much different the A-model mustangs were from the D-models that went into Germany.
*There you are, some homework for you*

Let me guess, unless I can dig up extensive technical documents or pilot accounts comparing the durability of the P-40 to the P-51, you're going to cry foul? 
*This is the corner you've fought yourself into; yes, I would like to see at least some documentation that supports this.*

Are you really going to argue that the P-51 was a better low-altitude fighter then the P-40? When the P-40 could out-turn and out-roll the P-51, and the P-51's speed advantage was slimmest on the deck? 

In any case, I find it very interesting that the P-51 actually was deployed as a purpose-built fighter bomber- the A-36! It was used in North Africa, and was basically a P-51B with dive brakes. By all accounts, they fared quite well. This demonstrates, I think, that the P-51 wasn't a bad low-altitude fighter- it's just that the Pony does a lot better at altitude. On the deck it's equal, at 30,000 feet it shines. 
*No, I'm not arguing anything, you are arguing that the P-40 was a better multi-role (better than what, you don't say) fighter. You still haven't presented a case for the P-40 multi-role supremo*

Yes, I eagerly await the rest of the forum telling me how an excellent power to weight ratio is not tremendously useful.
*Excellent power to weight ratio? Presumably this explains the P-40's less than sparkling climb rate? However, you did, as ever, respond to a point I wasn't making, that of the Bf109 being inferior in every respect; I'm sure there more learned Bf109 students than I on here who will tell you exactly what a Bf109F would make of a P-40*

It wasn't the cleanest ship, not by a long shot- but it WAS a superior energy fighter to the Zero, only because the Zero was a very dirty ship with that big radial, and was so very light. Against pretty much every other fighter of the war, the P-40 was a furballer- slow, but manuverable. The Zero is the only exception, because the Zero was right on the extreme end of the scale.
*Wrong way around, the P-40 was pretty dirty, I don't believe the A6M could be described as very dirty. The rest of the piece is back in ramble mode I'm afraid, I'm not sure what you're trying to say*


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## Demetrious (Mar 23, 2009)

Colin1 said:


> *Not THAT funny, I don't recall Jesus ever flying a P-40 but you might want to consider that line of response could well be offensive to any number of members on here.*



Yes, in the same breath that I mention Optimus Prime- thus establishing that I am referencing both as examples of supreme, unassailable power? Yes, what a _shattering_ insult to the Christian faith, of which I am a member. I expect adults- especially the people I have been privileged to speak with on this forum- to be rational enough to understand what is being said.



> You will need to spell out exactly why you think the P-40 had more potential that it was given credit for and it won't do you any good trotting out the 'fit it with a Merlin' argument again - we've already shown you that in the P-40F and L it didn't exactly light the plane up.[/B]



*Listen very carefully,* because I am tired of repeating myself. 


The P-40 had an excellent turn rate, better then most fighters of the war.
The P-40 had an excellent roll rate, better then most fighters of the war.
The P-40 was a very durabe fighter, able to absorb much damage.
*The P-40's performance suffered only because of insufficient engine power, which was easy to remedy with a more powerful powerplant.*
In short, the only aspect of the P-40s performance that was lacking was the powerplant. With the addition of a more powerful engine, the otherwise-excellent performance characteristics of the P-40 would have kept it a competetive fighter.



> *But don't you see why that damns your argument? Why did Kindleberger suggest something better (that didn't even exist yet!) if the P-40 had so much development potential left in it?*


*

Because people disagree. Just because Kindleberger said the P-40 was tapped out doesn't mean it was. A disagreement between the Army and the Navy over the B-36 bomber led to something called the "Admiral's Revolt."

Oh, and lets not forget that by building their own fighter, North American Aviation wouldn't have to pay a licensing fee to Curtiss-Wright for each fighter built.  




I'd wager the other part was the lack of anything else to choose from; you can come close just by being the best of a bad bunch...

Click to expand...


It was, in fact. 




We've yet to nail this elusive potential of yours...


Click to expand...



It's only drawback was a weak engine. There. Put a better engine in it, you have a much better fighter. That's it. 




The XP-40Q had a -121 Allison with two-speed supercharging and water injection good for around 1430hp - I'd call that a decently powerful powerplant. I'm not really sure what the rest of this piece is trying to tell me either.

Click to expand...



That engine was needed in the production P-40s to improve their performance, not in some ill-conceived "P-51 clone."




This is the train that you keep missing, development potential - the P-40 didn't have alot of it

Click to expand...


Prove it. Even the late Merlin-engined models received only 1200hp engines, not the 1500 hp ones they needed. You can't dismiss the P-40s potential simply because nobody actually used it. 




That's still not a good enough reason to keep the P-40

Click to expand...


The P-40 was tougher, more manuverable, and cheaper. Good enough? 




There are countless instances where a P-40 could shoot down a P-51 but my money's still on the P-51.

Click to expand...


You fail to understand the scenario that I am describing. Assuming a "fair fight," i.e, both aircraft head-to-head and spot each other at a good distance, the P-51 will not turn in a circle to fight the P-40, but will fly a distance off and turn around to make another pass, by which time the P-40 will be turned around to face it. It will be a series of head-on passes if the P-51 chooses to energy fight.



Colin1 said:



This is the corner you've fought yourself into; yes, I would like to see at least some documentation that supports this.

Click to expand...


Cool, show me some documentation that proves that the P-40s development potential was used up.



Colin1 said:



Excellent power to weight ratio? Presumably this explains the P-40's less than sparkling climb rate?

Click to expand...


You seem to have trouble with basic reading comprehension. I was talking about fighters that DID have good power-to-weight ratio, not the P-40. How could you make this error when I've spent the entire thread talking about how badly the P-40 needed a more powerful engine!?



Colin1 said:



No, I'm not arguing anything, you are arguing that the P-40 was a better multi-role (better than what, you don't say) fighter. You still haven't presented a case for the P-40 multi-role supremo

Click to expand...


Mostly because the P-40 was more durable and was a better gun platform (the P-51 was notoriously twitchy on the controls.) It was a better gun platform because the sturdier wings didn't flex as much, though I don't know if this advantage was marked. 

The success of the A-36 as a dive-bomber shows that the P-51 was just fine at jabo, however. I'm not saying the P-40 was "supreme" at multi-role, but there were some reasons to favor it in theaters where ground attack was borne by fighter-bombers instead of high-altitude bombers that required escort. 



Colin1 said:



However, you did, as ever, respond to a point I wasn't making, that of the Bf109 being inferior in every respect; I'm sure there more learned Bf109 students than I on here who will tell you exactly what a Bf109F would make of a P-40

Click to expand...


The P-40 had a superior turn and roll rate. The Bf-109 had much better power to weight ratio. I can tell you exactly what a P-40 would make of a 109. It'd save it's airspeed to put it's nose on target if the 109 tried to climb and attack from a dive; dive to the deck to make such attacks more difficult (the ground precludes a diving escape afterward, forcing either a more vulnerable zoom climb or a transition to a slower, more horizontal approach,) and then attempt to force a scissors or turn fight, where the P-40 is dominant. Alternately, the 109 pilot might insist on a series of head-on passes, in which case the victory is down to luck, nerve, and who is the better shot.*


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## drgondog (Mar 23, 2009)

Demetrious said:


> I guess this would depend on how much different the A-model mustangs were from the D-models that went into Germany.
> 
> *Well, the major differences in the A to the B were 1.) drop the wing and redesign the cowl to digest the Merlin, b.) redesign the radiator scoop/cowl, c.) add the 85 gallon fuselage tank, move the carburator intake from top of cowl to 'chin', d.) add about 400 pounds to the airframe.
> 
> ...



Can you step away from your strong affection for the P-40 and think through all the classic comparisons of ACM metrics (WL, Power to Weight Ratio, Roll Rate, Power profile of the Engines) and still make a case that the P-40 was as good as either the Me 109 or Fw 190 or P-51B?


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## Colin1 (Mar 23, 2009)

Yes, what a shattering insult to the Christian faith, of which I am a member. I expect adults- especially the people I have been privileged to speak with on this forum- to be rational enough to understand what is being said.
*Your arrogance will be your undoing my friend, just because you don't find something offensive doesn't mean others won't. It's precisely because they're adults that you don't need to resort to overblown superlatives normally expected from a teenager*

The P-40 had an excellent turn rate, better then most fighters of the war.
The P-40 had an excellent roll rate, better then most fighters of the war.
The P-40 was a very durable fighter, able to absorb much damage.
*Yes it did, when did anyone say that it didn't?*

The P-40's performance suffered only because of insufficient engine power, which was easy to remedy with a more powerful powerplant.
In short, the only aspect of the P-40s performance that was lacking was the powerplant. With the addition of a more powerful engine, the otherwise-excellent performance characteristics of the P-40 would have kept it a competitive fighter.
*There was more to the P-40's lack of power than the engine, it was a dirty airframe and that's where it was out of favour with newer designs. These were complementing the better powerplants with cleaner designs and more efficient methods for dealing with losses around the airframe. That's why the Packard Merlin in the P-40F only made a difference over previous versions of the P-40; stacked up against similarly-engined but newer designs, it wasn't competing.*

That engine was needed in the production P-40s to improve their performance, not in some ill-conceived "P-51 clone."
*So if the 1500hp Packard wasn't doing it for the P-40, why do you think the 1430hp Allison would have?*

Prove it
*History*

Even the late Merlin-engined models received only 1200hp engines, not the 1500 hp ones they needed. 
*Packard Merlins were not 1200hp*

You can't dismiss the P-40s potential simply because nobody actually used it.
*It was used, they wrung as much as they could get from the P-40 airframe and then they moved on. *

The P-40 was tougher, more manuverable, and cheaper. Good enough? 
*No. It wasn't fast enough and couldn't climb well enough; it was turning into a boom and zoom victim for the newer fighters. Cheapness is what mainly kept it in production for so long after its obsolesence.*

You fail to understand the scenario that I am describing. Assuming a "fair fight," i.e, both aircraft head-to-head and spot each other at a good distance, the P-51 will not turn in a circle to fight the P-40, but will fly a distance off and turn around to make another pass, by which time the P-40 will be turned around to face it. It will be a series of head-on passes if the P-51 chooses to energy fight.
*Oh, I think I understand you; isn't that what Japanese fighters tried to do when the late-war USN fighters came scything through them?*

Cool, show me some documentation that proves that the P-40s development potential was used up.
*There's one set called NA-73*

You seem to have trouble with basic reading comprehension. I was talking about fighters that DID have good power-to-weight ratio, not the P-40. How could you make this error when I've spent the entire thread talking about how badly the P-40 needed a more powerful engine!?
*and you seem to have trouble with professional courtesy and manners when presented with an opinion counter to your own. You gave a very strong impression that you were referring to the P-40 when you said that*

Mostly because the P-40 was more durable and was a better gun platform (the P-51 was notoriously twitchy on the controls.) It was a better gun platform because the sturdier wings didn't flex as much 
*Do you know this from your days on flight sims?*

I'm not saying the P-40 was "supreme" at multi-role, but there were some reasons to favor it in theaters where ground attack was borne by fighter-bombers instead of high-altitude bombers that required escort
*Actually you did, but ground attack, down low, would favour the P-40; let's leave it there and pretend you never said multi-role...*


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## Demetrious (Mar 24, 2009)

drgondog said:


> Can you step away from your strong affection for the P-40 and think through all the classic comparisons of ACM metrics (WL, Power to Weight Ratio, Roll Rate, Power profile of the Engines) and still make a case that the P-40 was as good as either the Me 109 or Fw 190 or P-51B?



Perhaps I'm not making myself clear. I have said- multiple times- that the P-40 was nigh crippled by it's very poor power-to-weight ratio. It had excellent performance in other categories- the airframe was inherently very manuverable- but without a proper engine, it's absolute disability in the vertical allowed aircraft like the Bf-109 to simply extend away, loop over the top, and make diving attacks from above with near impunity. 

Now, in 1940, the P-40 was pretty evenly matched with the 109, having superiority in manuverability but inferiority in power-weight ratio. For reference, the A-81 A-2 Hawk had a power-to-weight ratio of 0.31 (Horsepower/Kg.) The Emil Meschersmitt had one of 0.45. By the time the Me-109 Gustav came out, however, the discrepancy in power-weight between the two ships had gone from significant to dominant. By 1942 the Gustav was sporting a 1400 hp engine, while the P-40s engine still labored around 1200hp, where it had been since 1940. (Engine upgrades in the P-40 seem to have improved high-altitude performance, but not actual raw power output on the deck.) This meant that the Gustav had a power/weight of 0.52 hp/kg while the P-40 stayed at 0.31. The discrepancy went from an edge for the Bf-109 to a dominant advantage that the Bf-109 could exploit at will. 

A proper powerplant upgrade would have allowed the P-40 to counter the vertical advantage of later Bf-109s with some ability- by giving it enough power to reliably keep it's nose in the air long enough to meet a diving Bf-109 (or Fw-190, for that matter.) The necessity of meeting diving attacks by climbing to meet them was first observed by Boelcke in 1918. This wasn't as important in 1940, when the ability of the Bf-109 to get in such a position, as well as it's ability to extend far enough away to try it, wasn't as pronounced, but by the time the Gustav model came out, it was imperative. 

This same analysis can be applied to both the P-51B and Fw-190. Even though neither of these aircraft were known to be great climbers, the P-40 was such a poor one that it really didn't matter. 

I took some time to type up this explanation, so I'd appreciate it if you didn't dismiss it as my "affection for the P-40." 

Now, on to Colin!



Colin said:


> Your arrogance will be your undoing my friend, just because you don't find something offensive doesn't mean others won't. It's precisely because they're adults that you don't need to resort to overblown superlatives normally expected from a teenager



It's called hyperbole, and it is a useful literary technique. 



Colin said:


> There was more to the P-40's lack of power than the engine, it was a dirty airframe and that's where it was out of favour with newer designs. These were complementing the better powerplants with cleaner designs and more efficient methods for dealing with losses around the airframe.



Agreed. The P-40 was not, and never would be, a high-speed energy fighter. The issue of the powerplant was simply that it required mediocre, adequate performance in speed and power-to-weight ratio, elsewise it's advantages could be neutralized handily. 



Colin said:


> Packard Merlins were not 1200hp



Which models received 1500hp Merlins? Wikipedia says that even the late-model N production runs were still being fitted with Allisons. Did any other model besides the experimental Q prototype mount a Packard Merlin? I throw myself upon the greater knowledge of my fellows here, for I know not.



> So if the 1500hp Packard wasn't doing it for the P-40, why do you think the 1430hp Allison would have?



Who says the 1500hp Packard _wasn't_ doing it for the P-40? Just because the P-40 so equipped wasn't as fast as the P-51? A P-40M Warhawk with a 1500hp engine would have had a power-weight ratio of 0.51 hp/kg. Or the 1400hp Allison, which would yield a ratio of 0.47, still much better. (I'm still curious as to why that Allison engine in the P-39 was never put in the P-40- technical difficulties, perhaps?) The Allison in the P-39 was most certainly available by 1942. 



Colin said:


> No. It wasn't fast enough and couldn't climb well enough; it was turning into a boom and zoom victim for the newer fighters.



All which could have been greatly alleviated by a better powerplant. This is what I'm trying to say- all the reasons that you give for why the P-40 was lacking could have been addressed with a better powerplant. It wouldn't have _eliminated_ them, but they would have been far less problematic.



Colin said:


> Oh, I think I understand you; isn't that what Japanese fighters tried to do when the late-war USN fighters came scything through them?



Scything? Not even a Hellcat driver was eager to pit his ship against the firepower of the Zero's 20mm cannons. No, the scything owed much more to other factors, not the least of which being the Zero's high vulnerability and the rapid attrition of trained Japanese aviators. 

Ask any WWII pilot what attack he'd prefer- a head-on attack, or an angle where the enemy couldn't shoot back at him- and I think you'll get the latter reply every time. 



Colin said:


> There's one set called NA-73



I addressed that already. 



Colin said:


> and you seem to have trouble with professional courtesy and manners when presented with an opinion counter to your own



If I didn't want your opinion I'd hardly be discussing the matter with you! It's simply very frustrating to spend so much time and effort making these verbose and detailed posts, only to have my meaning inverted 180 degrees several times by accident. 



> Do you know this from your days on flight sims?



While we're discussing politeness, we might say a few things about your condescending, high-handed attitude. I try not to read too much into these things- much is lost in translation in the textual medium, after all- but it's poor form to call me impolite and then use an insult yourself in the next breath.


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## Demetrious (Mar 24, 2009)

Sorry for the double post ladies and gentlemen, but Colin requested proof of the P-40s structural strength, and I was able to find it for him:



> On the whole, because of their durability and flight range, the pilots liked both the Tomahawk and the Kittyhawk. The strength of its 5-longeron wing became legendary after an aerial engagement on 8 April 1942 [19]. On this day, flight commander Lieutenant Aleksey Khlobystov rammed German aircraft two times in a single engagement. He cut off the tail assembly of one Messerschmitt in an overtaking maneuver and severed a portion of the wing of a second Messerschmitt. Both times he struck the enemy aircraft with the same right wing panel. Both Messerschmitts went down and the Tomahawk landed safely at its airfield, where it was repaired without any particular difficulty. Its pilot, who did not suffer even a scratch, was recommended for the HSU rank and received the monetary bonus of 2000 rubles for two destroyed enemy fighters.



The source is here:

The P-40 in Soviet Aviation

This confirms the claim of a five-spar wing, and the strength offered by it. Finding similar data to compare the P-40 to the P-51 might be difficult, but I'll see what I can find regarding the P-51 in mid-air collisions- or even wing diagrams showing the number of spars. 

The best I can do for now is this: http://img155.imageshack.us/img155/7608/1222905782388.jpg

I think that diagram shows a two-spar wing, but I can't be sure. In any case, it makes a lovely desktop.


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## Colin1 (Mar 24, 2009)

Demetrious said:


> ...ladies and gentlemen, but Colin requested proof of the P-40s structural strength, and I was able to find it for him


It won't take much detective work for your ladies and gentlemen to realise that I made no such request. I do however, recall saying this:-



Colin1 said:


> The P-40 was structurally a strong aircraft... ...it was a robust fighter in a whole inventory of robust fighters


I don't require any such proof and neither I suspect, does anyone else. 

Its structural strength wasn't enough to prevent the P-40 from being rendered obsolete.


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## Demetrious (Mar 24, 2009)

Colin1 said:


> It won't take much detective work for your ladies and gentlemen to realise that I made no such request.



All anybody has to do is scroll up to see this:



Colin said:


> Let me guess, unless I can dig up extensive technical documents or pilot accounts comparing the durability of the P-40 to the P-51, you're going to cry foul?
> *This is the corner you've fought yourself into; yes, I would like to see at least some documentation that supports this.*



Your reply, as per your standard practice, is the one in bold- specifically requesting documentation to support my comparison of durability.

In any case, the same article, in the footnotes, says that a one or two spar wing was the norm in those days. I think it's a safe assumption that the P-40 paid for the extra structural strength from three additional spars with equivalent weight. 

*drgondog:* An apology is in order, I missed 9/10ths of your last post, because it was in a quote box. I didn't realize you'd replied in bold.



drgondog said:


> Well, the major differences in the A to the B were 1.) drop the wing and redesign the cowl to digest the Merlin, b.) redesign the radiator scoop/cowl, c.) add the 85 gallon fuselage tank, move the carburator intake from top of cowl to 'chin', d.) add about 400 pounds to the airframe.
> 
> To go from the A to the D - first add all the above, then redesign the turtledeck/birdcage canopy to accomodate teardrop canopy, add 2 x .50 cal and 600 rounds of ammo, provide structural beef up of vertical stabilizer spar, add wheel uplock kit, add tail ventral fin for models past the -5, change the incidence angle of the horizontal stabilizer, increase the Wing root chord to provide better strength in whell well area, add stronger wing hardpoints to permit 160 gallon ferry tanks or a 1,000 pound bomb.



Thank you! So the D-model Mustang gained a lot of weight, but the cutting down of the fuselage behind the cockpit eliminated some weight in turn and improved the aerodynamics of the ship? I'd assume the D model was faster, but the B model, lighter (and probably the better climber,) and the A model, even more so.



drgondog said:


> There is no reason, nor is there a body of data, to suggest that one coolant system was 'better' than the other.



Agreed. A liquid cooled system is a liquid cooled system is a liquid cooled system. The only real difference is how much armor any given plane had installed around it.



drgondog said:


> Can anyone on the forum name Fewer than 10 fighters that would be considered superior to a P-40 as a manueveing dogfighter?
> 
> The USSR had at least 5 if you stick with just the Yak and Laag, the Germans at least two without dipping into Fw 190D or Ta 152, the Brits at least three with Spit, Typhoon, Tempest, The Japanese with virtually every low wing fighter after the Type 97.



What? 

The P-40 was one of the tightest-turning monoplane fighters of the entire war. It could do a 360 in 20 seconds, whereas most Bf-109 variants required 23. It could also outroll the Spitfire (at higher speeds,) easily outroll the Tempest, and the roll rate of the Zero was just hopeless (the Type 97 was a bit better.) The only ship that could really out-turn the P-40 was the Spitfire (I've seen numbers from 17-19 for the Spitfire.) I'll try to find a single chart that compares the P-40 and P-51 turn radius/rate (so don't be surprised if I edit.)

EDIT: Righto, I've found some data given by our fellows on this very forum in days past; attributed to Soviet testing:

Soviet Testing of the P-40. That seems to confirm my "19-20" second figure, at any rate. I'll see if I can find us data on the P-51s rate. 

EDIT THE SECOND: 



> The turning characteristics of the subject aircraft are substantially the same as the P-40F and the P-39D. None of these appears to have any definite superior turning characteristics.\
> 
> In close "dog fighting" the subject aircraft has the very decided advantage of being able to engage or break off combat at will. However, if neither airplane attempts to leave the combat, the P-40F is considered to have a slight advantage.



Source: World War II Aircraft Performance.

"Turn rate," is only one axis of manuverability. Roll rate is more important, since every aerobatic maneuver starts with a roll. For this reason I'd rate the Fw-190 as superior in maneuverability, because even though the P-40 could out-turn it without much trouble, nothing, absolutely nothing, could touch the 190s roll rate. 



drgondog said:


> Slippery statements. The P-40 in equivalent gross weight operational conditions had slightly better wing loading which suggests that it could make a tighter turn as long as it had the power to sustain that turn in level flight - BUT the 51 was cleaner, had more power to weight, lost energy slower in a turn and could sustain a level turn longer for those reasons. Don't know if a P-40 can gain and SUSTAIN a turn advantage long enough to get on a 51 tail - pilot skill being equal. You have sources of comparative tests to prove your thesis?



Well, pretty much everything I've read gives the P-51 24 seconds to make a 360 degree turn- but I'll say now that that usually doesn't tell the whole story, since there are so many other factors effecting turn rate. 

What is this about "sustaining a level turn longer?" Planes don't just turn and turn until they fall out of the sky, they have a "sustained turn speed," at which the difference between induced drag by high AoA and engine power balance out. The sustained turn speed for the P-51 is most certainly higher then the P-40, for all the reasons you named- it's a cleaner ship with a bigger engine. Another consideration is that pure wing loading doesn't tell the whole story with the '51- the laminar flow wing made for less drag then another wing with the same wing loading, allowing the '51 to keep a higher energy state then another aircraft with the same wing loading- and thus make a faster turn. 

However, that higher speed meant the turn _radius_ would be larger, as well, so the P-40 would be able to turn inside the -51. This explains the phenomena nicely.



Colin said:


> As to roll, the P-40 might out roll the 51 at low speed, What is your source to suggest the P-40's superior roll capability and if, cited, for which flight regimes?



You're in luck, some nice people in another thread just showed me this: Roll rates. Observe how the P-40 is superior to the P-51 until about 280MPH, where they balance out. The Mustang is truly designed to work with speed. 



drgondog said:


> I am really curious why you think this. While mV>>2 is classic 'energy', Energy in ACM context is the ability to sustain Velocity in Manuever and to quickly change Energy states (i.e trade speed for altitude - with the better 'energy' going to the fighter that losses less V for the same H, or holds V for greater H) Why do you think the P-40 excels over the Zero in Energy Manueverability in any region except Dive?



Oh, simple. really. Since mV>>2 determines total energy, and the P-40 had more mass then the Zero, at the same airspeed, the P-40 had more energy stored in it then the Zero. This meant that it could bleed off more during violent maneuvers and still have some left to work with. Since both aircraft had about the same wing area- and thus induced about as much drag at any given angle of attack- the P-40 held more energy simply because it entered the fight with more. 

The superior power to weight ratio of the A6M, however, meant it could replace energy much faster. P-40 pilots had to make very sure they didn't bleed off too much energy with needless maneuvers, because replacing it without trading altitude would be hard.

Again, all the P-40s problems come calling right back to the power plant, don't they?


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## claidemore (Mar 25, 2009)

Demetrious said:


> Again, all the P-40s problems come calling right back to the power plant, don't they?



Actually the P40 had a few other problems. 
Stability comes to mind, something they finally addressed with the N models by lengthening the fuselage. 
They also required constant trimming, something that made them somewhat dangerous in the ground attack role, particularly for bombing, and something that kept the P40 pilot task overloaded in a dogfight. 
Here's a quote from Wing Commander James Edwards who flew Kittyhawks in North Africa. 



> On the P40 series:
> 
> "... not an easy aircraft to fly properly and as a result, we lost a good number of pilots while training."
> "In the first few months after conversion to Kittyhawks, all the squadrons lost heavily to the 109s."
> ...



Also a quote about reliability of armament in desert P40's. 


> A new, and deadly, problem cropped up for the Kittyhawk pilots. Under the high-g forces of dog-fighting and severe dust conditions their six .50 caliber guns would often develop stoppages. They would get in a few bursts and then nothing. In the middle of a dog-fight they would be left without guns. No doubt, many Kittyhawks and pilots were lost because of this problem. The problem never was completely fixed on Kittyhawks, the guns were always unreliable in the desert.



The landing gear was also 'relatively narrow' which did lead to some accidents. The 109 and Spitfire had the same fault, though for some reason the Spit never got a rep for ground accidents.


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## Colin1 (Mar 25, 2009)

Demetrious said:


> Originally Posted by Colin
> As to roll, the P-40 might out roll the 51 at low speed, What is your source to suggest the P-40's superior roll capability and if, cited, for which flight regimes?


Though irritating
it's one thing to suggest I submitted a post when people can check that I clearly didn't, it's quite another to doctor a post to make it look as if I posted it.

Your incoherent ramblings are beginning to cross the line of decent behaviour, kindly refrain from this in future.


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## Demetrious (Mar 25, 2009)

claidemore said:


> Actually the P40 had a few other problems.
> Stability comes to mind, something they finally addressed with the N models by lengthening the fuselage.
> 
> They also required constant trimming, something that made them somewhat dangerous in the ground attack role, particularly for bombing, and something that kept the P40 pilot task overloaded in a dogfight.
> Here's a quote from Wing Commander James Edwards who flew Kittyhawks in North Africa.



Clive Cadwell, highest scoring Aussie ace and a pilot in the African theatre, had this to say:



> The highest-scoring P-40 ace, Clive Caldwell (RAAF), who scored 22 of his 28.5 kills in the P-40, said the type had "almost no vices", although "it was a little difficult to control in terminal velocity".



That seems to confirm that the P-40 was tricky in the dive, but (seems) to conflict on stability. Not that surprising, however- P-47 pilots transferring to the P-51 often complained about how twitchy and sensitive the controls were, when even the official evaluations of the P-51 praised it's exceptionally stable handling. 

All in all I'm inclined to believe that the P-40 was on the unstable side, because the N-models weren't lengthened for giggles, after all. Clearly it was a difficult aircraft to exploit to it's fullest.

By all accounts the P-40 was a good gun platform (owing primarily to the strength of the wings, which didn't vibrate as much, and the weight of the aircraft,) but problems with inherent stability would counteract that. In any case it doesn't seem to be as good a jabo fighter, if only for the problems in a dive. 

Another issue with it's ground attack ability is an anecdote I recall from _God is My Copilot,_ where it was said that a dive angle of over 30 degrees was avoided, because the centerline mounted bomb might strike the prop as it separated. 

Hmm, perhaps the P-51 and variants really were the better Jabo fighters!



> Also a quote about reliability of armament in desert P40's.



Was this a problem attributable to the P-40s design, or the M2 Brownings? Maintenance of machinery in a desert environment is notoriously difficult, since sand is so damaging and gets into everything. Designs that expose too many critical components don't help, however.



Colin said:


> Though irritating
> it's one thing to suggest I submitted a post when people can check that I clearly didn't, it's quite another to doctor a post to make it look as if I posted it.
> 
> Your incoherent ramblings are beginning to cross the line of decent behaviour, kindly refrain from this in future.



My apologies, sir. In trying to respond to both you and drgondog at the same time, I accidentally typed your name into those quote tags instead of drgondog. This is a typo, nothing more.

I can only assume that you thought that quote was the request for technical information I asserted you had requested. You were asking after comparative durability, not roll rate, of course, and you asked for that verification in this post (most recently.) You were well within your rights to request supporting data, I might add.


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## drgondog (Mar 25, 2009)

Demetrious said:


> All anybody has to do is scroll up to see this:
> 
> In any case, the same article, in the footnotes, says that a one or two spar wing was the norm in those days. I think it's a safe assumption that the P-40 paid for the extra structural strength from three additional spars with equivalent weight.
> 
> ...



No D, they also reduce to aerodynamics. In ACM, stick forces for roll and turn are also important and differed quite a bit between various WWII ships. ALL airframe design is a study in performance trade-offs for the target mission but all things being equal you are better served with the cleaner airframe.


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## Colin1 (Mar 25, 2009)

Demetrious said:


> ...the P-40 could keep more of it in the first place through violent manoeuvres






Demetrious said:


> ...P-40 pilots had to make very sure they didn't bleed off too much energy with needless manoeuvres


So which?


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## Colin1 (Mar 25, 2009)

Demetrious said:


> My apologies, sir. In trying to respond to both you and drgondog at the same time, I accidentally typed your name into those quote tags instead of drgondog. This is a typo, nothing more.
> 
> I can only assume that you thought that quote was the request for technical information I asserted you had requested. You were asking after comparative durability, not roll rate, of course, and you asked for that verification in...


Fair enough
though I'm not sure what this 'sir' thing is all about...
I do recall the post, but it was _some_ documentation from a general call for _any_ documentation to support your notion in its entirety; what can you see that the 1940s powers-that-were couldn't see in the P-40? I'm reasonably well-versed in how the US thought fighters should be built


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## Demetrious (Mar 25, 2009)

drgondog said:


> Hard to say D - the spar design approach is a shear web with caps top and bottom. The 'taller' the spar, the more effective it is in taking out bending loads - but also heavier.



Interesting. We'd probably need more detailed schematics to be sure.



drgondog said:


> Parasite Drag will dominate at high speed and induced Drag dominates at low speed. In addition, the wild card factors are stick forces for elevator and rudder as well as Trim drag component of Parasite Drag as the elevator/rudder deflections increase in the manuever - which ones do you want to talk about?



All of them, actually...



drgondog said:


> That being said D- are you 'engineering' in a 'no engineering zone'. While I agree with much of what you just said I am curious regarding how deep you want to go in the math?



As far as you can take me! Some months ago I heard some people calling the P-51 a mediocre turner, and started investigating wing loading data. I suspected that wing loading was far from the only determinator of turn rate, and soon I was into drag coefficients. And then there was turn rate vs. turn radius to consider...

Suffice it to say I still don't understand the aerodynamic principles effecting turn performance nearly as well as I'd like to. 



drgondog said:


> You care to display the math? Start with Thrust = Drag. Supply the CD0 of both ships and look up Cl as f(AoA) so we can get Induced Drag at all velocities of interest, Lets get the Hp charts, the gross weights you want to talk about and forget about trim drag at high AoA for the moment.
> 
> Prove your thesis?



Assuming an equal playing field- that is, both aircraft at co-alt, and having had time to build to their maximum speed at the given altitude (which was pretty much the same for the Zero and the P-40 for much of the war,) the P-40 will have more initial kinetic energy simply because it has more mass.



drgondog said:


> If it entered the engagement with approximately the same velocity it has more initial system energy by virtue of extra mass. The problem with the P-40 is that the Wing Loading is much higher, it has less Hp/mass to transfer continuously to Thrust Req'd to sustain the rate turn of the Zero.



Sustain the turn rate? I never suggested the P-40 could keep a sustained turn with a Zero, never (and if I did, I was telling lies.) The wing loading of a Zero is insanely low.



> If the P-40 engages in turning manuever a) it loses velocity faster than the Zero, and b.) the only remaining manuever the P-40 may perform to re-generate system energy is to intially trade altitude (potential) energy by diving to regain velocity.



Are you saying that the P-40, while having more initial energy, also bleeds it off faster in any given maneuver? Fast enough to negate it's advantage?

When I speak of energy fighting, I speak of maneuvers that take advantage of instantaneous turn rate, but not ones that continue long enough to continually sap energy. Simply put, I imagine a P-40 pulling a hard instantaneous turn to gain lead on a Zero for a shot, and yet still keep enough kinetic energy that it will be safely out of guns range by the time the Zero reverses to put it's nose on target. 



drgondog said:


> The Zero may outclimb, out accelerate, out turn the P-40 as ACM options. When the speed of the ships reduces below 300mph the Zero also out rolls the P-40.



This chart from WWII aircraft performance has the Zero rolling significantly worse then the P-40 at all speeds, at 10,000 feet. 

Your sources may vary, of course. I sadly haven't found any other roll comparison charts yet to compare with this one.

Agreed on the climb and accelerate parts, however. A P-40 pilot really has to be careful not to let a Zero boom and zoom them (thankfully they're not the best at that,) and use their roll rate to turn a defensive situation into an offensive one. That, and keep their speed up, with the exception of guns defense break turns.



drgondog said:


> Hmmm. You just spent a couple of lines describing why the P-40 had energy to burn in violent manuevers





drgondog said:


> So which?



The P-40 started a fight with a Zero with a superior cache of energy, but once that energy was gone, it was _gone._ This principle of course applies to all energy fighters and all energy fighting- no aircraft can accelerate fast enough to escape an enemy right on their six that they've foolishly slowed down to furball with- but in the P-40s case the underpowered engine made this rule an absolute. Where other fighters could burn off a little more energy and replace it with good acceleration, the P-40 simply could not.

EDIT: 



Colin said:


> Fair enough
> though I'm not sure what this 'sir' thing is all about...
> I do recall the post, but it was some documentation from a general call for any documentation to support your notion in its entirety; what can you see that the 1940s powers-that-were couldn't see in the P-40? I'm reasonably well-versed in how the US thought fighters should be built



I call everybody sir. It's polite. 

I think the powers that be back in the 1940s could see plenty in the P-40- it was just that by the time they had proper engines available for the P-40, they also had brand-new fighters available as well. I certainly can't fault them for going the route they did; that's just the way history played out.


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## Glider (Mar 25, 2009)

Its understandable that we tend to emphasise the fighter abilty of an aircraft. However its worth remembering that the P40 was a very capable GA aircraft able to carry a payload that at the time, few other aircraft could carry.

Yaks, Zero's, Ki43, Me109's Spitfires and Hurricanes couldn't match it.

For that alone it deserves bonus points.


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## slaterat (Mar 25, 2009)

Hurricanes lugged 2 x 500lbs, I thought the P40 was only good for a single 500lber.

slaterat


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## Glider (Mar 26, 2009)

I have seen pictures of P40's carrying 3 x 500lb bombs and even 6 x 250lb bombs but the most I have seen on the Hurricane was 2 x 250lb. 
I believe the impact on range was greater on the Hurricane than on the P40 and often in the Far East the Hurricane carried one bomb under one wing and a drop tank on the other, the same with 4 x rockets on a wing.

Certainly could be wrong on this and any information welcome


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## Elvis (Mar 29, 2009)

Demetrious,

You aluded, in a post that appears on page 8 of this thread, that the V-1710-63 engine, used in the P-39D, made 1600HP.


> Now, the P-39D2, in 1941, had a 1600 horsepower Allison V-1710-63 engine in it, a massive improvement over the 1100 horsepower Allison it had before.


Actually, it made 1325HP @ 3000 RPM on take-off 1150HP @ the same RPM @ 11800 ft.
It seems that Curtiss skipped this particular version of that engine and went straight to the "-73", going on to mount the "-81" and finally, the "-99" versions of this engine in successive models of the P-40.
The "-73" differs from the "-39" in that there is no gun synchonizer installed and it has improved take-off ratings.
Performance for "-73" is as follows:
1150HP @ 3000RPM - take-off
1150HP @ 3000RPM @ 11800 ft.
The "-81" differed from the "-73" in the supercharger's gear ratio and and it was equipped with an automatic boost control.
Performance for the "-81" is as follows:
1200HP @ 3000RPM - take off
1125HP @ 3000RPM @ 14600 ft.
The "-99" differed from the "-81" due to an "engine regulator" (define that as you will. Sounds like a governer to me) and an automatic manifold pressure regulator.
Performance for the "-99" is as follows:
1200HP @ 3000RPM - take off
1125HP @ 3000RPM @ 15000 ft.

On page 9, you stated you were unaware that a 1200 HP Packard-Merlin engine was used.


> Wikipedia says that even the late-model N production runs were still being fitted with Allisons. Did any other model besides the experimental Q prototype mount a Packard Merlin?


The "F" and "L" versions of the P-40 both utilized the Packard-Merlin engine.
I understand the practice was halted due to engine manufacture needed for P-51 use.
Also, the Packard-Merlin used in those P-40's was the 20 ("XX") series engine, which only made about 1300HP.

Here's the link to the Allison engine info - ModDesig

Here's the link to the Packard-Merlin engine info - http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/1650-1.pdf

Here's the link to the P-40 info - Perils P40 Archive Data


Ok, that was all.
Pardon the intrusion.





Elvis


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## pbfoot (Mar 31, 2009)

Just listened to Stocky Edwards around 20kills and he said the P40 stated off with 2 250lbs bombs but later used 2 500lb bombs an interesting thing in this vid is he says the wing guns used to jam after pulling g's about 3-4 minutes into the following vid anyone else ever hear of this

_View: https://www.youtube.com/watch?v=p_umy5aRfLw_


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## Glider (Mar 31, 2009)

A P40 with 6 x 250lb bombs
File03372.011 kittybomber.jpg - Wikipedia, the free encyclopedia


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## Vincenzo (Mar 31, 2009)

Max bomb load for P-40N was 2*1000 pounds (wing) and 1*500 (belly)
F&L can load 1*600 in belly position and 6*30 in wing position it's not told if both. D&E can load the six small in the wing and a 500 in belly (as above for both)


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## Clay_Allison (Mar 31, 2009)

would a near miss by a 250lb bomb kill a Panzer?


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## Ivan1GFP (Apr 2, 2009)

There are a few misconceptions floating around in this discussion about the various aircraft in this discussion: The P-40, P-51, A6M Zero and to a very small extent, the Hurricane.

The A6M Zero was NOT a draggy plane as has been claimed multiple times. It was actually a very slippery and aerodynamic aircraft. Consider the speeds it achieved with VERY LITTLE installed power. The restriction on diving speed was structural strength. Increasing the gauge of the skinning was the means of increasing the dive speed of the late model A6M. The Zero was also probably not as slow as I have seen in one of the graphs posted here. Consider that a Model 21 in US Navy tests was able to achieve 332 mph even though it was admittedly (Cdr Hoffman) not quite 100%. Also worthy of note is the manifold pressure settings used to achieve this speed. It was NOT running "Overboost" or "WEP" during the USN tests. A fairly thorough examination out at J-aircraft puts the max speed at 345 mph at altitude.

The P-40 and P-51 are radically different as far as drag. Folks here keep comparing the Allison engined P-40 and the Merlin Mustangs. There is a much more direct comparision. The early Allison Mustangs (P-51, A-36, F-6, P-51A) were quite fast aircraft down low. The P-51A was actually faster than the later P-51B and P-51D up to about 15,000 feet IIRC. The P-51 was faster than the P-40 by about 40 mph with similar installed power. Compare the P-40E and the P-51 (350 vs 390). Compare the P-40N with the P-51A (375 vs 415). Don't feel bad though: The Spitfire was also about 30 mph slower than the P-51 with very similar engines (Spitfire IX - 410 mph, P-51B - 440 mph).

In my opinion, the P-51 was not a particularly rugged airframe. Consider that the A-36 eventually had its dive brakes wired shut because at high speed, the stress sometimes ripped the wings off. A P-51B structural failure in a dive killed the pilot Tommy Hitchcock. Apparently a door over the gun installation deformed enough to change the airfoil shape and overstress the wing. The P-51B and P-51D did NOT have quite the same airfoil shape or handling according to at least one pilot quoted in a book by John Dibbs. (I can find the reference if anyone is curious.) This pilot continued to fly the B/C after his unit switched to the D model.
The change from Razorback to Bubbletop made the plane LESS streamlined AND also less directionally stable. The fin extension was one attempt to cure the problem. The longer fin on the P-51H was another attempt.

One of the things that I keep seeing mentioned is how the Me 109 had a great amount of stretch that it served throughout the war. I believe that there was enough difference between the 109E and 109F to deserve an entirely new designation. Compare the two aircraft. There isn't much that carried through from the E to the F.

Hope I haven't insulted anyone here.
- Ivan.


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## wombat40 (Apr 2, 2009)

Try to obtain a copy of "Pacific Hawk" by John Vader (Purnells History of WW2 series)
Seems that there was an attempt to fit a RR engine to the P40. Remember too that the first Mustangs were fitted with Alisons and designated A 36. They still outperformed the P40, design plays a part in performance, not just engine size and type


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## HoHun (Apr 3, 2009)

Hi Ivan,

>The Zero was also probably not as slow as I have seen in one of the graphs posted here. Consider that a Model 21 in US Navy tests was able to achieve 332 mph even though it was admittedly (Cdr Hoffman) not quite 100%. Also worthy of note is the manifold pressure settings used to achieve this speed. It was NOT running "Overboost" or "WEP" during the USN tests. A fairly thorough examination out at J-aircraft puts the max speed at 345 mph at altitude.

Hm, I guess you're thinking of my graph. However, I have compared all available data sets carefully and don't think there is much potential for the A6M to have been significantly faster than my calculation.

My calculation also takes the use of war emergency power into account, so I have to reject that aspect of your criticism.

Do you have a link to the examination you mention? If it's Richard Dunn's, I found it to be quite interesting, but don't think it's methodically good enough to warrant conclusions regarding any specific A6M top speed.

Regards,

Henning (HoHun)


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## FLYBOYJ (Apr 3, 2009)

Ivan1GFP said:


> The A6M Zero was NOT a draggy plane as has been claimed multiple times. It was actually a very slippery and aerodynamic aircraft. Consider the speeds it achieved with VERY LITTLE installed power. The restriction on diving speed was structural strength. Increasing the gauge of the skinning was the means of increasing the dive speed of the late model A6M. The Zero was also probably not as slow as I have seen in one of the graphs posted here. Consider that a Model 21 in US Navy tests was able to achieve 332 mph even though it was admittedly (Cdr Hoffman) not quite 100%. Also worthy of note is the manifold pressure settings used to achieve this speed. It was NOT running "Overboost" or "WEP" during the USN tests. A fairly thorough examination out at J-aircraft puts the max speed at 345 mph at altitude.


Although the Zero was able to attain those speeds, it handled like a brick at speeds over 300 mph. At speeds between 250 - 275 mph is when the Zero was at its best; above that the ailerons were heavy and the aircraft lost its maneuverability advantage.

One of our members is a CAF member and their chapter has owned a few Zeros, this was echoed by the pilots who flew them.


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## Ivan1GFP (Apr 3, 2009)

Hello HoHun,

I am still trying to find Intelligence Brief #3 for details about the testing of the Aleutian Zero. I agree with you that the argument by Richard Dunn is a bit optimistic, but the throttle settings used in the test are probably accurate.
BTW, The 98% comment I attributed to Cdr Hoffman was by Admiral Saunders. (My inaccurate recall.)

Hello FLYBOYJ,
Just for grins, Look for YOU-TUBE videos of the Zero and Oscar. I believe most of the Zero videos are of the CAF A6M5. Use a stopwatch while watching the videos. The actual filmed roll rates may surprise you. They surprised me! Unless these films are faked, these planes roll a whole lot faster than most folks think they do. Seems to me that 150-250 mph is a more ideal speed range for these planes.

- Ivan.


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## FLYBOYJ (Apr 3, 2009)

Ivan1GFP said:


> Hello FLYBOYJ,
> Just for grins, Look for YOU-TUBE videos of the Zero and Oscar. I believe most of the Zero videos are of the CAF A6M5. Use a stopwatch while watching the videos. The actual filmed roll rates may surprise you. They surprised me! Unless these films are faked, these planes roll a whole lot faster than most folks think they do. Seems to me that 150-250 mph is a more ideal speed range for these planes.
> 
> - Ivan.



I agree with the roll rates (especially with the Oscar) and stand corrected on the best maneuvering speeds. Point here is that when either aircraft is forced to fight at higher airspeeds the advantages of the Japanese aircraft are greatly diminished. As we've all heard on countless occasions, the Flying Tigers proved this with little doubt.

I saw a demo at Chino back in the early 80s - a Zero against an F4U. At lower airspeeds in the horizontal the Zero had an advantage out turning the F4U. As soon as both aircraft continued their demo at higher airspeeds, the Corsair went into the vertical and used a high yo-yo to his advantage. The Zero could not shake him.

Lastly at the end of the day, always consider the skill of the pilot as that could throw all performance estimates out the window.


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## Marshall_Stack (Apr 3, 2009)

Ivan1GFP said:


> Consider that the A-36 eventually had its dive brakes wired shut because at high speed, the stress sometimes ripped the wings off.



Not that it matters much (especially for this discussion), but I have read many times that having the dive flaps wired closed was a myth. Reading accounts from A-36 pilots seems to support this as a myth.


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## Ivan1GFP (Apr 3, 2009)

Hi FLYBOYJ,
I believe we are generally in agreement. Keep in mind that a modern flight exhibition may not be entirely representative of wartime performance though the conclusion from this demo seems quite reasonable. No one is running their engine at maximum performance and no one is going to pull enough G in their WW2 senior warbird to black out.

A modern WW2 warbird is probably MUCH lighter than the wartime version. Self sealing fuel tanks, armour, guns, ammunition, bomb racks, plumbing for external tanks, ancient radios and the like are typically deleted which makes at least the US warbird much more agile.

Hello Marshall_Stack,
I have not researched the topic of dive brakes other than in the last couple hours after seeing your message. I just read in one of the Mustang books that structural failure was the reason for wiring the dive brakes. Your account seems to be the correct one, though I will still check through a few books to see if I can find the A-36 structural failure reference.

- Ivan.


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## FLYBOYJ (Apr 3, 2009)

Ivan1GFP said:


> Hi FLYBOYJ,
> I believe we are generally in agreement. Keep in mind that a modern flight exhibition may not be entirely representative of wartime performance though the conclusion from this demo seems quite reasonable. No one is running their engine at maximum performance and no one is going to pull enough G in their WW2 senior warbird to black out.


From sme of the single engine warbird owners I've met, sonme of them are limited to 3.5 Gs either by feds or self imposed.


Ivan1GFP said:


> A modern WW2 warbird is probably MUCH lighter than the wartime version. Self sealing fuel tanks, armour, guns, ammunition, bomb racks, plumbing for external tanks, ancient radios and the like are typically deleted which makes at least the US warbird much more agile.


Way lighter. Just the radios alone could mean upwards of a few hundred pounds.


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## JoeB (Apr 3, 2009)

Ivan1GFP said:


> Consider that a Model 21 in US Navy tests was able to achieve 332 mph even though it was admittedly (Cdr Hoffman) not quite 100%. Also worthy of note is the manifold pressure settings used to achieve this speed. It was NOT running "Overboost" or "WEP" during the USN tests. A fairly thorough examination out at J-aircraft puts the max speed at 345 mph at altitude.


We must generally accept the fact that top speeds of WWII fighters under real combat conditions are still uncertain. In many cases apparently equally valid data disagrees. To make a single graph of course we must reject one conflicting datum or another, but that doesn't make the graph a single fact which surely correctly describes the situation. In general, the speeds of Japanese fighters in optimal conditions probably tended to be understated; by a very significant degree? not necessarily, and there's always actual performance in combat v ideal conditions (especially later in the war), but there is that tendency, and j-aircraft has been a good place to read about it over the years.

One thing the Zero could and often did do with perhaps understated speed was use energy tactics, which the JNAF did use contrary to myth even in 1942, when it had an altitude advantage. Most one on one analysis, and any fair flight demo, would tend to assume equal starting points for both fighters but of course that was seldom true of any given actual combat. So one key feature of a fighter was how well it might exploit an initial advantage to shoot down another fighter, v how well it might parry an initial disadvantage to avoid being shot down itself, seeking just to fight another day in that case. It might use different tactics or strengths depending which of those situations it was in. 

Joe


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## slaterat (Apr 10, 2009)

Joe B wrote 



> Most one on one analysis, and any fair flight demo, would tend to assume equal starting points for both fighters but of course that was seldom true of any given actual combat. So one key feature of a fighter was how well it might exploit an initial advantage to shoot down another fighter, v how well it might parry an initial disadvantage to avoid being shot down itself, seeking just to fight another day in that case. It might use different tactics or strengths depending which of those situations it was in.



That might be the truest words ever written on this forum.

Slaterat


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## Ivan1GFP (Apr 15, 2009)

This is a minor change of subject, but I believe it is directed to a pretty good audience:

What is the length of the P-40B/C and P-40D/E?

From what I have found (without having the actual aircraft to measure), 
the P-40B/C is 31 feet 8-Something inches
the P-40D is supposed to be about 6 inches shorter: I have seen numbers stating 31'2". The diagram in the Schematics area shows 31'7". America's Hundred Thousand says 31'8.5".

Which is correct? How can I confirm?
- Ivan.


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## drgondog (Apr 15, 2009)

Ivan1GFP said:


> This is a minor change of subject, but I believe it is directed to a pretty good audience:
> 
> What is the length of the P-40B/C and P-40D/E?
> 
> ...



Curtiss P-40D

All changes due to the 1710-39 engine resulting in a Thrust line change, as well as a shortened nose - adapted for all subsequent models.


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## Ivan1GFP (Apr 15, 2009)

Thanks Drgondog,

Your reference is one of the conflicting sources.
Earlier in the series you listed is this:
Curtiss P-40

Length is 31' 8 3/4" so Length of D/E would be 31' 2 3/4"

Please refer to the diagram at this discussion:
http://www.ww2aircraft.net/forum/schematics/p-40d-drawing-12109.html

Length is 31' 7"

If the diagram is in error, where is the error?

- Ivan.


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## drgondog (Apr 15, 2009)

Ivan1GFP said:


> Thanks Drgondog,
> 
> Your reference is one of the conflicting sources.
> Earlier in the series you listed is this:
> ...



Without access to Curtiss plan with full dimensions I don't know how you will reconcile the differences in the Wiki/Baugher, etc write ups


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## Ivan1GFP (Apr 16, 2009)

Hello Drgondog,

Now you see the problem. The schematic was supposedly based on Curtiss drawings and information compiled by William Wylam. The origin of the information from the other two sources is unknown. I am hoping someone can point me to a provably correct source.

- Ivan.


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## Elvis (Apr 16, 2009)

Ivan,

While I haven't checked out that particular aspect myself, have you investigated the Perils P40 Archive Data website?


Elvis


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## MikeGazdik (Apr 16, 2009)

Speaking of the thrust line change, was there any validity to the USAAC wanting to change the Allison engine prop gearing? I have read that the change reduced the load on the front of the crank, when changing to the design of the P-40E and beyond. (P-38 was also changed)

I have never read anything other than it was changed because the USAAC believed it should be done. But in my opinion, the USAAC was hardly ever absolutely right on any of thier pre-war beliefs.


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## Ivan1GFP (Apr 17, 2009)

Hi Elvis,
I HAVE checked the Perils P-40 stuff. Nothing conclusive there that I can find either. A simple stated number doesn't really help much because I have several of those. The best that I have found is the P-40D schematic hosted here because it gives a break down of the lengths of various parts.

Hello MikeGazdik,
I remember reading somewhere that the earlier reduction gear had a fairly low limit on the amount of torque it could handle. When the engines became more powerful, the older gearing could not reliably handle it, so the profile changed to the P-40D and later.

- Ivan.


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## Elvis (Apr 22, 2009)

Ivan,

Re: prop gearing

That sounds familiar to me, too, but the way I understand it, the actual _gear ratio_ didn't change, only the "stoutness" of the gear assembly itself.
Whether that meant bigger bearings and/or bigger gears, I don't remember now.
Do you know if there was an actual change to the ratio or was it just a change to a more robust assembly?


Elvis


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## V-1710 (Apr 22, 2009)

The early V-1710-C as used in the P-40/40B/40C used an internal spur gear on the prop shaft with a 2:1 propeller reduction drive ratio. The centerline of the prop shaft was 3-3/16" above the crank certerline. It was thought this design would provide for better streamlining, though it did cause a certain amount of trouble during development due to high bearing loads and lubrication requirements. The V-1710-F as used in the P-40D and later Warhawks used a simple external spur gear propeller shaft drive, still with a 2:1 ratio. The propeller shaft ceterline was now 8-1/4" above the crank. The two principle reasons for the change was the external spur gear was stronger and more reliable than the internal spur gear, and it was easier to engineer a left hand rotation version for the P-38.


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## MikeGazdik (Apr 22, 2009)

V-1710 said:


> The early V-1710-C as used in the P-40/40B/40C used an internal spur gear on the prop shaft with a 2:1 propeller reduction drive ratio. The centerline of the prop shaft was 3-3/16" above the crank certerline. It was thought this design would provide for better streamlining, though it did cause a certain amount of trouble during development due to high bearing loads and lubrication requirements. The V-1710-F as used in the P-40D and later Warhawks used a simple external spur gear propeller shaft drive, still with a 2:1 ratio. The propeller shaft ceterline was now 8-1/4" above the crank. The two principle reasons for the change was the external spur gear was stronger and more reliable than the internal spur gear, and it was easier to engineer a left hand rotation version for the P-38.



Geat info! My question is this, was it the belief by the USAAC that the internal spur gear was weaker than the external spur gear, or was it a fact that Allison had found themselves? Like I said alot of what the Army Air Corps pushed for or believed in during the pre-war period was suspect at best. If that theory was from Allison, or backed up by other aeronautical / engine designers than I fully respect that theory.


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## V-1710 (Apr 23, 2009)

MikeGazdik said:


> Geat info! My question is this, was it the belief by the USAAC that the internal spur gear was weaker than the external spur gear, or was it a fact that Allison had found themselves? Like I said alot of what the Army Air Corps pushed for or believed in during the pre-war period was suspect at best. If that theory was from Allison, or backed up by other aeronautical / engine designers than I fully respect that theory.



The internal spur gear required almost 1/3rd. of the engine oil flow at 75 p.s.i. to be properly lubricated. The V-1710 C was rated at 1150 h.p. with a max r.p.m. of 3700, and it is my understanding the limiting factor in the C's rating was the internal spur reduction gear. There seems to be some evidence the internal spur gear caused additional crankshaft stress too. Wright Field asked Allison the feasability of changing to an external spur gear as early as 1935, but the change required a redesign of the crankcase and crankshaft. This was eventually tested in 1937, and the design was used in the V-1710 F. So, it would seem that the idea to change the design came from the A.A.C..


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## Elvis (Apr 24, 2009)

V-1710,

Thanks for the reduction gear info.
Yeah, I didn't think the ratio changed.

Earlier in this thread, I saw a question pop up a few times that I don't think ever really got answered.

Why wasn't the supercharger on the Allison developed to further the engine's performance?

We already know why the turbo portion of the supercharger was only used with the P-38 and how the general feeling towards the Allison seemed to change, once it was found the Merlin could be successfully adapted to both the Mustang and the P-40.
However, once all P-M production had switched over to series 60/61 engines, I think this is when the Allison found its way back into the P-40 (because it was easier and quicker to relegate all P-M production to the higher performing series, thus discontinuing the older 20 series engine that was used in the P-40).
So, since the P-40 was once again "saddled" with the Allison, why send pilots out in a plane that lacked the neccessary engine performance to make it..._competitive_?
Ok, so it can't have the turbo, but why couldn't an _alternate_ supercharger be developed to help the engine make a little more power, at least at altitude, where it counted?
It could've been as easy as a larger impeller (which I think more than a few of us had mentioned before).

Does anyone know if any tests were carried out with a larger supercharger? (and not the "Q" version, a larger version of how the engine had been outfitted, pretty much all along)



Elvis


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## V-1710 (Apr 25, 2009)

Good question. I have never found a definitive answer as to why a 2-stage blower was not developed earlier when the turbocharged version turned out to be only feasable in the P-38. By the time Allison got around to the V-1710-93, the Packard built Merlin had already satisfied the requirement. My guess would be that the AAC may have felt the single stage V-1710 was wholly adequate for low altitude fighters such as the P-39, P-40, and P-51/51A, and thus there was good reason to continue to produce it for those aircraft. An interesting post-war side note- North American Aviation was developing the P-82 Twin Mustang as a long range escort fighter, and with the end of the war in sight, the decision was made to equip it with 2-stage Allisons. The reason was that when the war was over, Packard would have to pay Rolls-Royce a very substantial royalty for every Merlin it produced. The P-82 eventually did see service as a night fighter in Korea, and most versions were powered by 2-stage V-1710-143/145


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## claidemore (Apr 25, 2009)

There was always a need for low alt optimized engines, both Allison and Merlin. For example, most of the Spitfire Mks had low alt versions. 
The P40 design had already shown that it did not get significant increase in performance by the installation of the more powerful Merlin, so developing a more powerful Allison for a limited increase in perf, simply wouldn't make sense. 
There was plenty of low alt fighter bomber work to be done, which the P40 had proven very suitable for, and there were plenty of excellent performing high alt designs (P51/P47/Spitfire) to fill the escort and interceptor roles.

The question really isn't 'why didn't they develop the Allison further for the P40', but 'what need would have been filled if they had?'.


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## vanir (Apr 28, 2009)

From the fantastic link Elvis posted earlier in the thread, I noted the RAAF routinely modified the boost regulator for 70" Hg on the F3R and F4R and from an Allison document to the effect it seems restricted themselves under advisement to 60" Hg for the F20R due to likely engine damage with the impeller upsizing.
Nevertheless Allison states in excess of 1580-1780hp were the ratings "for an average engine" under these high boost conditions and considering the P-40M has a rated altitude around 4000m this seems to put it on equal terms with the LF MkVb Spit becoming available at the time.
It would seem as a fighter-bomber in ready numbers you couldn't do much better, I'm wondering if this was the reason the relatively few MkV Spits delivered to the RAAF were sent to the mainland for training squadrons whilst the P-40 remained in front line service.


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## Elvis (Apr 29, 2009)

Excellent points, everyone.
I think that answers my question, however, in regards to your question, Claidmore, maybe I should've written "_why didn't they develop the Allison further for the *P-51*?_"...or at least left the turbo on the engine, which begs another question...

...but that's getting off topic. 




Elvis


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## Shortround6 (Jul 9, 2009)

Elvis said:


> Excellent points, everyone.
> I think that answers my question, however, in regards to your question, Claidmore, maybe I should've written "_why didn't they develop the Allison further for the *P-51*?_"...or at least left the turbo on the engine, which begs another question...
> 
> ...but that's getting off topic.
> ...



The "turbo" was never "ON" the engine. The "turbo" was always mounted some distance away, it weighed somewere inthe area of 120-150lbs (without piping/ducts) and was about 2 feet across. See the P-37 toget an idea oh how much room was needed for the turbo. Turbo also needed an intercooler to be really effective. More space, weight and drag. Thousands of cubic ft per minute have to go through the intercooler (or over it, see P-38 ). Turbos only show any advantage at altitudes above 20,000ft and the higher above that the more advantage they show. 25,000-35,000 is were they really come into their own. 

If what you want is a low altitude engine a single stage, single speed supercharger works just fine. any extra stages just add weight and bulk with no gain in power. One might note the low altitude Spitfires that had their impellors cropped to about the diameter of the Allison's impeller. One might also note that they used a single speed, single stage supercharger. Many Beaufighters also had impellors cropped and gear boxes locked in "M" gear for low altitude work. The British designating superchargers as "Ground", Medium or moderate (4000-8000ft?) and High altitude. 
As a further note the Difference between a single stage Merlin, as used by the P-40 and a two stage Merlin as used by the P-51 was 8 in in length and about 250lbs dry weight on the engine. This does not include the weight of the inter-cooler radiator (Merlins used liquid cooled aftercooler vrs the air-cooled intercooler the americans used on the rest of their engines) or the coolant. Could the P-40 move it's firewall back 8in to maintain the CG or would other changes have to be made? Could the P-40 afford the extra 300-4000lbs of weight subtracted from it's gross weight? Or can the extra 3-400lbs just be accepted. The extra Power will only be useable somewere above 10-14,000ft.


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## Elvis (Jul 9, 2009)

...It appears I've been busted by The Semantics Police.
Ok, how about if I change that to "with", instead of "on".
Better?

...and what I'm trying to do is to take an existing design and make it an "all-altitudes" fighter, at least on par with the Me-109.
Clay Allison thinks re-fitting the P-40 with a R-R Griffon would do the trick (essentially creating a sort of "_American Me-109_"), and he may actually be onto something.
Personally, I think the Allison was already capable of creating enough performance to make it a _more worthy_ adversary of the 109, than it actually was.
What I noticed was that the Allison was originally designed to be a turbo-supercharged engine from the get-go and that those engines, such as the V-1710-89A, had very good performance numbers that could've made the P-40 into a better performing airplane at altitudes over 15K feet, while keeping the increase to the engine's weight (compared to the single stage, single speed version) as minimal as possible.
I believe the increase was only listed at around 100-200 lbs., at the most, according to the specs seen at enginehistory.org.

Another thing that struck me the other day, was to simply increase the c.r. of the engine, while utilizing a two-speed, intercooled version of the supercharger that was actually used on the P-40.
I sat down and ran the numbers last night.
The rule of thumb that I used was that there is a 4%-6% increase in horsepower for every point of compression increase (a little fact I read in Hot Rod magazine years ago).
Erring on the lower side of that scale, I found that if the c.r. were raised to 8.15:1 (from 6.65:1), the resulting HP increase would be 6%, or a raise from 1150HP to 1219HP.
@ 25K ft., I believe most of the engines that were actually used in the P-40 were rated at 800HP.
So HP @ 25K ft. is about 69.5% of take-off HP.
If you factor in the 6% increase in HP, that _nudges_ that rating to 848HP.
If the second speed of my proposed two-speed supercharger were enough to double the speed of the impeller (compared to the initial gear ratio that would be used at lower altitude), and that resulted in cutting the HP @25K ft. differential in half, then, with the S.C. in "high gear" and the engine running the higher c.r., would result in a HP @ 25K ft. of 1033.5.
At that point, I believe high altitude HP rating is about 84.7% of the take-off rating.
This is an improvement of 15.2% of the rated HP of the engine at altitude, comared to its take-off HP.

So what does this all mean?
Either nothing at all, or a marked improvement of high altitude performance, without loss of low altitude performance.

Would that improvement put it on par with an Me-109, at that altitude? 
Maybe, maybe not, but one would hae to see _some_ improvement over the form of the engine that was actually used, and even though Pilot Skill had a lot to do with the outcome of a lot of those sorties, you have to admit that the more you start off with, the more you can do.



Elvis


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## Clay_Allison (Jul 9, 2009)

Elvis said:


> ...It appears I've been busted by The Semantics Police.
> Ok, how about if I change that to "with", instead of "on".
> Better?
> 
> ...


I think that having some "Interceptor Hawks" with larger impellers for higher altitude work alongside the regular Warhawks would have been a good stopgap solution until more flexible all-altitude fighters became available.


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## vanir (Jul 9, 2009)

I think you'll find raising the compression will cause you to recalibrate the boost governer and return lowered throttle heights. The way you'd compensate this is a much larger diameter, lower pressure supercharger and/or an increase in engine capacity. You'll also have to play around with valve and ignition timing a fair bit, even combustion chamber and piston crowns and in those days...without computer modelling to help...

One historian said simply, in that period it took a new fighter two years to develop from drawing board to prototype, whilst it took a new aero engine six years.

Using the Merlin 20 series as roughly comparable to the F20 except for two speeds, even in the high gear the Allison only loses out around 4000ft of throttle height from the Merlin. A recalibration for higher CR could kill this tiny advantage, which for the most part could be made up for with ram and experienced piloting anyway. My impressions from various RAAF documentation is the P-40M and N were about as good as the P-40F, with cruise-altitude performance the most marked difference in the field. The P-40M was used in far greater numbers by the RAAF than the F, of which we used only a handful (I think it might've been a parts availability thing..but vets have said the Allison was very highly regarded and very well suited to conditions).


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## Clay_Allison (Jul 9, 2009)

> I think you'll find raising the compression will cause you to recalibrate the boost governer and return lowered throttle heights. *The way you'd compensate this is a much larger diameter, lower pressure supercharger* and/or an increase in engine capacity. You'll also have to play around with valve and ignition timing a fair bit, even combustion chamber and piston crowns and in those days...without computer modelling to help...



That's just what I was thinking in the last post, making a P-40 with the above changes and perhaps some load lightening for rate of climb (reducing guns to 4, etc) would have given Warhawk pilots in North Africa for instance a better shot at the 109.


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## Shortround6 (Jul 10, 2009)

Sorry about the "sematics" Elvis but the point is that the turbo-charger used up an awful amount of volume inside a fuselage. And the weight was not a small thing either. See the Republic P-43 Lancer which used a basic engine the same as many P-36 models.

For aircraft use compression ratio in the cylinder and boost fight each other. Raising either one increases the risk of detonation. For a given type of fuel if you raise the compresion you have to lower the boost. The Allison used a higher compression ratio than the Merlin, this did give it better fuel compsumption numbers. the Higher compression engine will have higher thermal effiencincy. But by using less boost it means that less fuel/air is going through the engine so there is less power. It was estimated that the 6.65 compression ratio in the Allsion limited it to about 10% less power than the Merlin with it's 6.0 compression ratio. The Allision's extra 60 cu. in. cut the actual difference to about half of that though. 

As far as your two speed super charger idea goes it is a question of when. 

There is a very definite limit as to how fast you can spin impellors. both from the exploding them due to centrifugal force and air flow. Just like propellors, having the tip speed of the impellor exceed the speed of sound does strange things to the airflow in the supercharger.

IN 1939-40 most peaples superchargers were doing good if they had a pressure ratio of 2.3 to 1. That is 69 in of manifold pressure at sea level. the problem is with altitude. The Early Allisons were limited to 42in of MP so they were using a pressure 1.4 already at sea level. At 10,000 ft the air is about 75% as dense as it is at sea level so you need a supercharger that can deliver a 1.33 ratio to get you sea level pressure. multiplying this times your 1.4 PR used at sea level means you need 1.86 pressure ratio to keep your sea level T-0 power rating. going to 20,000ft where the air is 50% as dense as sea level means you would need a supercharger with a pressure ratio of 2.8 to get 1040 hp from the Early Allison at 20,000ft. By 1941-42 superchargers were available with pressure ratios of 3 to 1. This is a limitation of the compressor and not how it was driven. 
It also takes an awful lot of HP to drive a supercharger delivering these kinds of pressure ratios. This was a large part of the reasoning behind two speed drives. By using a lower gear at low altitudes were the high pressure ratio was not needed the impellor turned slower, used up much less power ( allowing more to go to the propellor) and heated the intake air less resulting in denser air and less problems from detonation. In some cases two speed superchargers were as much about getting better take-off performance as they were about getting better high altitude performance. British bombers got the first 2 speed supercharged Merlin Xs not because they gave 1,010HP at 17,750ft compared to the Spitfires 1,030HP at 16,250 ft but because they allowed 1,075hp for take-off compared to the Spifires Melin III's 880hp take-off rating. 
The Allisons used a compromise setting/gear ratio that gave them not quite as much altitude as the Merlin III but but better take off and certanly much better altitude performance than the low gear in the Melrlin X would have given.

An easy way of getting a ball park estimate on engine power at altitudes is to graph the engine power. Plot your known power at altitude point and then draw a line to Zero Hp at 55,000ft.


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## Elvis (Jul 10, 2009)

Very informative comments, guys.
Thanks for chiming in.

BTW, it seems I failed to mention that I was actually thinking more along the lines of the later M and N model P-40's, which would've used the "-81/99" engines, so comments about "early P-40's" doesn't really apply.
My apologies for not making that more clear, earlier.

I'll grant you that some tweaking would need to be done with a raise in c.r., but the 8:1 range isn't an "outlandish" figure for a supercharged engine, however, I wouldn't want to go much higher.
That's why I picked it.
There'll have to be some testing and maybe a slight redesign to the cylinder head (i.e., possibly better sealing), but the fact remains that a higher c.r. will give increased effciency to an engine, all the way across its rpm spectrum.
Also, that higher c.r. I gave isn't much more condusive to detonation, than the lower ratio...anyway, those engines did have a water-injection system, to counter detonation at times when the "WEP" button was pushed, so there's an added "anti-detonation device" at your command.
As for the two-speed comments, there's a "time-to-altitude" chart over at Peril's P-40 page, that the RAF ran and I noticed that the P-40 seemed to achieve its best climb when going from 5k-10k feet (approx. 3k ft./min., IIRC), however performance fell off sharply once 10K feet was surpassed.
If the transmission were atmospherically controlled, so that the second (higher) speed was engaged at somewhere around 12k-15k feet, wouldn't performance at those higher altitudes improve, due to increased delivery rate of fuel/air and maintaining cylinder pressure (compared to say sea level to 5k feet)?
I think maybe the point some you may not have noticed (and I admit, I probably wasn't too clear making it, as well) is that I'm not against _tempering_ that higher impeller speed, so as to retain the best engine performance at the higher altitude.
"Halving/doubling" the figures I posted earlier just made the math easier.

...and Clay, you made a good point, by splitting up the existing inventory of P-40's into low altitude and high altitude configurations, but I keep going back to the thought that if a pilot is engaged in a fight, he'd want to have the plane perfom as good as possible, regadless of altitude, thus the idea of an "all-altitude" P-40.
Something that would perform as well at 25,000 feet as we already know it did at, say, 2500 feet.
I'd just rather an enemy not have an altitude advantage over me.
I don't know, I'm not a pilot, just what *I'd* want, if put in that situation.
Am I wrong in assuming that?


Elvis


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## Elvis (Jul 10, 2009)

Clay and Vanair briefly discussed putting a larger supercharger on the Allison engine.
I too was once on that bandwagon, stating in the past that moving up to an impeller size of around 12-15 inches would give improvements in high altitude performance.
However, I'm now seeing a bigger picture, which is that it may not be _financially_ feasible to produce a separate s.c. just for that one application.
I think implementing a two-speed gear box to the already existing s.c. would allow for a less expensive (and possibly less intesive) R&D phase, and I'm betting that production costs would not only be lower but would allow for an existing unit (the supercharger itself) to be used for more applications, making it "look' more versatile in the eyes of the US government...who, after all, are footing the bill for all of this.
So what you'd have is one s.c. unit with two different gear assembly's available for it. It may even be possible to make them 'removable", so that one could swap out the single speed gear set for the two-speed gear set.
I do think though, for the purposes of this aircraft, that the largest incarnation of that s.c. (which I believe was 10.2") would be the best platform from which to work the mods from.

Just a comment from the _other_ end of the discussion.



Elvis


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## Shortround6 (Jul 10, 2009)

We may have three problems here.

1. The single stage supercharger just doesn't work that well over 20,000ft now matter how many gears or what gear ratio you use or drive it with. The late model Allisons used higher pressure ratios at take off than the early versions (mainly becaue they could use improved fuels), the -73 vesion in P-40K ran at 51in of boost for take off and 1325hp and 60in of boost at war emergency for 1550hp at sea level for pressure ratios of 1.7 and 2.0 respectfully. going to even 20,000 feet at those power levels means you need pressure ratios from your supercharger of either 3.4 or 4.0. The higher the pressure ratio the more power it needs to drive it AT ALL altitudes and throttle settings. Two stage superchargers can give the same pressure ratios with less power input and less heating of the intake charge. Or even more boost for the same drive HP. 

2. Increasing compression gets more work or power from the same amount of fuel. Great for cruising or for engines without superchargers. An engine running at 60in of MP is putting 20% more fuel and air through the engine per minute than an engine running at 50in of MP. so 20% more gross power, deduct the extra power needed to run the supercharger at that level and you have your net or propellor HP. ANYTHING that gets in the way of getting the MAXIMIUM amount of fuel and air through the engine per minute is going to hurt PEAK power. AN 8 to 1 compresion ratio would seriously limit the ability to use high manifold pressure. Allison themselves dropped the Compresion ratio of the later two stage engines. 

3. Can the P-40 ever be made competitive with the Me 109? the basic weight of most P-40s (the E through Ms) is about 6900-7000lbs? That is no guns, fuel, ammo, pilot etc. vrs the normal loaded weight of the 109 at just about the same 6900-7000lbs. Loaded the P-40 is going to go about 1500lbs more. even allowing the P-40 a bit less becasue of it's larger full tanks that is a lot of extra weight to try to compesate for. even Calling the 109 at 6900lbs and the P-40 at 8000lb for combat weight you are going to need 1677hp at altitude to equel the power to weight ratio of the 109G. Yes the P-40 may have some advantages but it was never going to have the straight line speed and climb of the 109. unless it had an egine with much,much more power.

If you can get a copy I would strongly suggest "Vee's For Victory!" by Daniel Whitney. See if yoiu can get it from a library if nothing else. 

I used the early Allison and Merlin engines as an illistration of effects of different setups because at the time there was little difference in the performance of the superchargers on the two engines. Later superchargers with much differnt pressure ratio capabilities and efficiencies would tend to cloud the results.


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## vanir (Jul 11, 2009)

According to a letter from Allison Division dated late 42 the only differentiation made between F3R and F4R engines was the automatic regulator. MAP ratings were revised and new ones cleared, partly because squadrons in the field were already ignoring Allison released operating guidelines and running both these engine types at as much as 66" and 70" MAP on 100/130 fuel.
My impressions are the revised MAP ratings are common to all F-series engines retroactively and ranged from 44" take off and 52" WEP to 46" and then 50" take off with 57" and then 60" WEP, with engine speeds for take off revised from 2800rpm to 3000rpm and probably a few more figures tossed in there as it seems to have been a work in progress through 1942.

There was a tremendous change with the F20R onwards due to the higher ratio and Allison was particularly concerned about engine overspeeding associated with extreme (unsanctioned) boost pressures being used in the field. Their final limitation was around 50" take off with 60" WEP although 46" for take off and 57" WEP was preferred for all F-series engines during 1943 (and if you asked they'd probably prefer you used the higher ratings on the 8.8 ratio F-series only).

At least this is what I've gathered so far. And from a mechanical standpoint I can see no reason personally why you wouldn't apply anything from the F4R to the F3R as the only change is an introduction of an auto boost regulator I assume absorbed from Packard's Merlin license.


It does seem to me the ability to move a larger volume of fuel per cycle transfers to increased throttle heights, aside from the simpler perspective of compensating reduced air pressure with increased boost pressure.
Here is what I'd do in hindsight with the Allison,
raise the impeller diameter to 9.75" and keep the 8.8 ratio
revise chamber and port design, including crowns and manifolding
revise valve and spark timing and bump max nom op speed to 3200
raise stat comp to 7.5 with a dynamic around 6.7
aim for a 60" take off and a 70" WEP on 100/130, looking for a throttle height of 12K ft with 60" (18K ft with 56")

Let a 109 cop 1750hp at a 3600m combat height and 1550 at 5000m coming into 1943. I'm going for something that'll give a 190A pause. Well...at least that's how I'd put it to the commitee for war funding.

As far as I can tell the major problem with the Allison is there's no real power available over about 5000ft as it stands (it was capable of tons below that). I don't think it ever needed to perform up near 20K ft, but 12-18K feet is definitely typical air combat height and it was running out of puff there (ie. could basically perform at climb/combat without any extra reserve which is what made it seem inadequate). To me the Allison seems like it just needed to be pimped a little, and I think the ratio jump to 9.6 from F3/4 to F20~ was the wrong approach, tackling this by force feeding instead of a general efficiency revision.

The Allison F3/4R was a brilliant motor. Tell me a Merlin can do 70" on 100/130 without holing pistons.


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## Shortround6 (Jul 11, 2009)

This does tend to paid to the super P-40 therory.

Even the Flying Tigers were using 58" of boost instead of the book 40.6" on their C series engines. 1600hp up to 1,700feet. that is 1,700 ft not 17,000ft. 

So when reading combat reports of fights at low altitudes the pilots may have been using hundreds more horespower than the book figures say they had. 

While the engines seemed to stand up to this abuse fairly well and Allison themselves may have wished (at times) for higher book limits early in the war, some pilots and mechanics pushed things to an extent that gave Allison fits. Some peaple report using 62" on these early engines but that would require over speeding the engine to 3200RPM. This is supposed to give 1700hp but that is a 6.25% gain in power for a 14% increase in bearing loads and internal friction. 

There is an awful lot of things happening with engines and fuel in just a few years that mean that just because something was done in 1943 that it could have been done in 1941 or even in parts of 1942. For instance 100 octane fuel. In 1939-1940 British and American 100 octane fuel was not the same gasoline. British fuel would allow much higher boost pressure than American 100 octane ( by british and american I mean the specifications the fuel was manufactured to) under rich mixture conditions. the two fuels were just about the same under lean conditions. British fuel would eat or disolve gaskets and seals in some american fuel systems and self sealiing fuel tank liners. It discovered that British 100 octane acted like 120 octane (or more properly performance number) when run rich. From this they developed a 100/125 octane fuel that was soon replaced by 100/130 but it took a while for the 100/130 designation to catch on so you will reports (especially from squadrons) that refer to 100 octane when they mean 100/130. A few batches of American fuel (before America got in the war) actually dropped from 100 octane lean to 90 something rich. 
This may have something to do with the conservative ratings for American engines in regards to boost in the 1941-early 42. 

Another thing is that the engine manufacturer was trying to ensure long engine life. While an under performing engine is a liability in combat, and engine that fails in flight isn't much good either and changing engines every 50-100 hours doesn't do much for operations compared to an engine that will go 150-200hrs.
Once WER ratings were officially allowed for the Allison the company recommended the following :

1, Engines should be removed and replaced at the end of ten hours total time at War Emergency Rating.

2 , New exhaust spark plugs should be installed prior to any expected WER operation to avoid running plugs which may have previously become partially lead fouled. Such plugs may form lead globules which lead to immediate pre-ignition which causes piston and ring failure.

3, Intake plugs should be replaced at the end of one hour of WER operation, or after ten hours of total operation during which at any time, the engine operated at WER settings.


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## Elvis (Jul 11, 2009)

I don't know why you guys want to concern yourselves with variations that were superceeded by the mid point of the war, but whatever. 
I'm trying to work with the a later versions, mainly the "G" series motors, which had the advantage of a 7-main block and a counterweighted crankshaft.
This allowed Allison to remand their prior recommendation of max. engine speed, going from 3200 to 3600 rpm.
Those changes would allow the engine to work better under heavy load, and even allow it to sustain heavier loads, easier....not to mention smoother operation.

Shortround - Weight and balance stats for a P-40N, dated 12/18/42 - http://www.raafwarbirds.org.au/targetvraaf/p40_archive/pdfs/P40N-1 Weight spec.pdf
Unloaded weight was 6120. Loaded was apparently 8000.

I still say upping the c.r. and implementing two-speed gearbox is a step in the right direction, however, I will agree with vanair, in that it should also include a change in manifolding and possibly porting and definately some sort of intercooler.

Lastly, according to some of the info given by Shortround6, some improvements in the ignition system seem to be in order, as well.



Elvis


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## Shortround6 (Jul 11, 2009)

Well you would need a time machine for the "G" model Allison to do any good for the P-40.

By the time the G models were running on the test stands the P-40 was not only past it's prime, it was beyond "stick a fork in it, it's done". It was throw the scraps to the dog, done.

ALL Allisons used 7 main bearings and in fact the 12 counter weight crankshaft could be fitted to E and F series engine blocks. 

The first true G series engine didn't run until late 1944. Only 3 or 4 were built. The next the "G" the G-1RA didn't hit the test stands till March of 1945. The G-2 model was never built and the G-3R model (8 built) got to the test stands in December of 1946. 

It is true that the G-6 model did complete a 150 hour test in October of 1946 but I think you get the point. 

By the way, the ONLY versions of the "G" that used higher than a 6 to 1 compression ratio were the -97 (G-1R) mentioned above (3-4 built), the -131 ( G-3R) built for a couple of modified C-54 transports and G-5 model of which none were actually built.

Upping the compression ratio is definatly the WRONG way to go if you are looking for power and not economy. 

P-40N was the stripped, lightened version (using aluminum radiators and oil coolers and two less guns amongst other modifications) that isn't ordered until almost 2 months after the Americans start test flying Merlin engined Mustangs. The engines in the final P-40N-40 production block used the 12 counter-weight crankshaft.

Point of listing Allison recomendations was that the use of WER power levels came at a cost. Practically any engine that used those high boost settings came with similar instructions.
Use of ADI carried similar or even more maintainence requirements.
Later post-war commercial engines managed to over come some of them.


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## vanir (Jul 11, 2009)

That info on British-American fuels makes very good sense. Australian and Middle Eastern squadrons attributed with using extreme boost pressures of 66-70" could've been using either, whilst Stateside the published restrictions were probably wiser.
And I think these operating conditions were a matter of sheer desperation, I know that at the time the elite Lae Zero squadron was overflying Port Moresby taunting local pilots with aerobatics and then shooting down any attempt at interception. Hell, I'd tell my mechanics to bugger the documents and just get me more power too.
Whilst in the Middle East you've got the F and G series 109 and then the appearance of the Fw190 over Tunis at the end of 42.
Plus in both these places you've got short, rough fields in poor conditions with a high emphasis on army support operations. You want a bomb load off the ground as soon as possible, and you want a very fast escape and a good low altitude climb rate to get you out of trouble.

I think perchance, if the extreme boost potential at very low altitude of the P-40 had been compromised at this stage for improved high altitude performance, it would've been a less valuable type. Once again I do think the best improvement to the P-40 would've been simply raising throttle heights by only a few thousand feet and maintaining that bulletproof reliability.
Leave the high altitude work for the turbosuperchargers and newer airframes. Besides, as air superiority slipperiness goes, the P-40 is just frumpy.


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## Elvis (Jul 12, 2009)

Shortround6 said:


> By the time the G models were running on the test stands the P-40 was not only past it's prime, it was beyond "stick a fork in it, it's done". It was throw the scraps to the dog, done...Upping the compression ratio is definatly the WRONG way to go if you are looking for power and not economy.


Being "past its prime" is the whole point of trying to improve performance in the first place.
If its performance was already on par with the 109, then this whole discussion would be moot to begin with.
I still think you're wrong about upping the c.r., as it would make the engine more efficient. That would improve both power AND economy, however, I guess we'll just have to agree to disagree on that point.
I'm not saying the jump would be "huge", but even that small bump would be helpful to the engine's performance.


Elvis


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## Shortround6 (Jul 12, 2009)

The P-36/P-40 airframe was just too dated to really bother with by 1943. No real shame in that. There were plenty of other 1934 era aircraft that didn't last any longer. And plenty that didn't last anywhere near as long. The fact that 1 or 2 others did last that long doesn't mean the Curtis was bad, just not as lucky.
With the rapid advances in aerodynamic knowledge, structural design and even new materials NO designer could see 6-9 years into the future. They had to make a best guess and hope they guessed right. In fact, I would bet that any designer who's 1934 design (of any type of aircraft) was still being manufactured in 1943 was as surprised as anybody else because he had probably designed (at least in his head or on napkins) any number of "NEW, IMPROVED" versions or entirly new planes based on new knowledge.

Trying to equel the performance of the 109 with a larger, heavier aircraft means you need a proportionately more powerful engine. In America in late 1941, early 1942 you have two choices. The Wright R-2600 or the P&W R-2800. You do have to have a prototype flying at least 6 months to year before the plane/ engine combination really sees squadron service. To equel a 109G in 1943 you don't need 1500HP at 20,000ft, you need more like 1800-2000hp at 20,000ft. 
While the P-40 may have had certain advantages over the 109 it always had a larger fuel capacity (advantage range/endurance-disadvantage size of airframe to house/carry larger tanks) and from the F model of the 109 the P- 40 carried a heavier installed weight of armament. In some cases a much heavier installed armament. A 109G with a single MG 20mm gun and two 13mm MGs had 184lbs worth of guns. A P-40 with even four .50s had over 250lb of guns. Since installed weight (mounts, heaters, feed boxes, access hatches etc) can be 30-50% higher than the gun weight WITHOUT AMMO we can see that the P-40 was at a disadvantage weight wise from the start. 
While Allison started investigating two- stage supechargers in 1940 they really didn't get any flying hardware until 1943. Without the 2nd stage the Allison was going to have trouble making enough power at altitude (20,000ft? and higher) to compete. 

If you can show me how I am wrong about the compresion ratio question please do so.
Please remember however that aircraft engines are going to behave rather differntly than modern auto engines. 
Since heat in the cylinder is a major part of detonation the largerdiameter cylinders of the aircraft engines are harder to cool, less serface area to volume than smaller car cylinders. Car engines seldom run at full boost for anywhere near the time aircraft engines did. Modern superchargers may create less heat for the same amount of boost (higher effiency ) than the older superchargers. And of course 40-60 years more knoweldge in combustion chamber shape.


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## Elvis (Jul 13, 2009)

Shortround,

Took a look at 109 performance over at the Aviation-History page and I see your point.
By the time of the 109G, the aircraft were of similar weight (I'm thinking P-40N), but the DB605 was making much more power than the Allison ever did during the war, aiding in that plane's performance advantage over the P-40.
However, we all know that the Allison _eventually_ eclipsed those engine performance figures later on, so coaxing 1800HP, or so, would definately be in the realm of possibility. I just seems that Allison didn't have the R&D to fall back on, yet.
However, at that time, it seems an 1800HP Allison probably wouldn't be ready for production until around the end of the war, and by that time, it would be more prudent to install such an engine in the P-51.
FWIW, I found a trivial, but interesting, fact the other night.
It appears the Allison's 1150HP rating yields a very similar HP/cu.in. rating as the 605 was, at the time it was rated @ 1475HP.
Both work out to about .67+ HP/cu.in.

As for increasing c.r., I don't see how it couldn't be beneficial.
One is basically getting a better "quench" of the f/a mixture in the TDC area and that always yields better engine efficiency because you ensure a more complete burn (in conjunction, upping voltage of the ignition system, coupled with a little more gap in the plug doesn't hurt matters, either).
Supercharging can yield a similar effect, because of the rise in cylinder pressure, the its not quite the same thing.
Again, the bump in c.r. I'm proposing is a small one, because I am being mindful of engine construction, changes in ignition timing and detonation.
Even though the HP rating jump is also fairly small (only 5.4%, if the jump is to a straight 8:1 c.r.), its _something_, and that's better than nothing.

However, all that being stated, I think the "best" thing we possibly could've done, at that time, was to try installing an engine of larger displacement into the P-40, along with making some aerodynamic improvements (such as laminar flow flight surfaces).
I'm thinking along the lines of Clay Allison's query about replacing the Allison with a Rolls Griffon....but that's a discussion for another thread.



Elvis


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## Vincenzo (Jul 13, 2009)

for info on 109 one of best it's Kurfurst - Your resource on Messerschmitt Bf 109 performance


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## Shortround6 (Jul 13, 2009)

In 1938-40 the NACA did a series of tests on factors that affected detonation. they found in no ranked order.

compresion ratio
inlet air temperature
inlet air pressure
fuel/air ratio
spark advance
size and shape of the combustion chamber
Temperature of the combustion chamber and cylinder walls 
engine speed. 

I am sure that other countries were doing simaliar testing. 
According to some sources compression ratio acted as a multiplier. Whatever the incoming charge temperature was ( and it could be several hundred degrees from the supercharger) was multiplied by the compression rato, maybe not a straight "times' the comprsion ratio but a higher compresion ratio heated the charge in the cylinder to a higher temperature before the ignition system fired.

If the charge self ignited before the spark pug fired things could get very strange, what is even worse is true detonation were instead of the charge igniting in one spot and flame front traveling across the piston top the charge being so close to auto-ignition temperature that even the pressure wave of the moving flame front causes the rest of the fuel/air charge to all burn at once. 

In aircraft sized cylinders this could get VERY interesting. Bristol once blew a cylinder off a test rig, through the building roof and completly clear of the building. Not likely to happen with an enbloc V-12 but kind of points out why nobody wanted to happen in the air. 

As I have pointed out bfore the increase in compression, while it did increase engine efficiency also lowered the amount of boost that could be used. Amount of boost is almost directly related to power output at a give rpm because it is directly related to the amount of fuel/air going through the engine. Discounting pumping losses or power to turn supercharger a 10% increase in manifold pressure means a 10% gain in power. 

Some of the studies are available on the NACA/NASA server.


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## Elvis (Jul 14, 2009)

Vincenzo said:


> for info on 109 one of best it's Kurfurst - Your resource on Messerschmitt Bf 109 performance


THANK YOU!
I've been trying to find that site for months, but couldn't remember what it was called and subsiquent Google searchs came up with everything but that site. 
-------------------------------------------------------

Shortround,

I don't know what else to tell you, other than, like anything, there are tolerances that one can work within.
Detonation can be quelled via a number of _techiniques_, the most common of which is reworking of the ignition timing and camshaft timing.
Again, for the small bump in c.r. that I'm proposing, I think the engine could handle the amount of boost it was already receiving, and then some.
Look at the Hydroplane racers that used those engines, almost exclusively, from the 1950's through the 1980's.
They would often throw on multiple turbo applications, spin those motors faster than anyone in their right mind would've during the war, and especially in the later "piston-era", would use nitrous oxide injection on a regular basis in order to increase power.
...and many of those engines would last at least a season or two before they needed any kind of major work done to them.
A lot of those engines simply wore out, before they "broke", as you propose, mainly because parts became increasingly harder to find.
I just think you're making more out of the c.r. bump than what would actually transpire.





Elvis


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## Vincenzo (Jul 14, 2009)

np, it's must help


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## Shortround6 (Jul 14, 2009)

Well in racing boats you can swim home if the engine blows up
not really an option in an airplane. 

The US wanted a test engine to survive 7 1/2 hours at the WER before they would sanction the use of that power level. 

And as I have pointed out before even Allsion lower the compression of just about all their two stage engines. In fact of the 763 G series engiens that left the factory only about 13 had a compresion ratio higher than 6 to 1 and 8 of those engines were installed on re-engined DC-4 airliners( C-54s) called the Xc-114 and the YC-116 wer fuel economy was more important than sheer power. 

What we know now may not have been known then. 
Many aircraft engines used a fixed ingnition timing or sometimes a two position timing, one retarded for starting and the normal position for all other running. Yes this did limit performance but it was also one less thing to go wrong. Or more than one thing since the insulating ability of air diminishes with altitude and some engines resorted to pressurised magnetos to help out. one less rotaing or moveing seal.

Rolls kept the same compression from first Merlin to last while going from 6 lbs boost to 25lb and even the war commercial versions stayed at 6 to 1. 

6 to 1 is not a magic number it is just what ROlls used and the two stage Allisons. Other engines used different compression ratios but then they had different bore to strokes, different cooling, lower peak boost and other differences (including ingnition timing and cam timing)


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## Clay_Allison (Jul 15, 2009)

> *1. The single stage supercharger just doesn't work that well over 20,000ft now matter how many gears or what gear ratio you use or drive it with. *The late model Allisons used higher pressure ratios at take off than the early versions (mainly becaue they could use improved fuels), the -73 vesion in P-40K ran at 51in of boost for take off and 1325hp and 60in of boost at war emergency for 1550hp at sea level for pressure ratios of 1.7 and 2.0 respectfully. going to even 20,000 feet at those power levels means you need pressure ratios from your supercharger of either 3.4 or 4.0. The higher the pressure ratio the more power it needs to drive it AT ALL altitudes and throttle settings. Two stage superchargers can give the same pressure ratios with less power input and less heating of the intake charge. Or even more boost for the same drive HP.



Not necessarily. Higher altitude performence can be gained at the COST of poorer low altitude performance if you use a larger impeller. I now believe that the engine change wasn't necessary so much as putting one production line to work making "Interceptor" Hawks built for high altitude supercharging and maximum weight savings for rate of climb wherever they could get it.


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## Shortround6 (Jul 15, 2009)

Clay_Allison said:


> Not necessarily. Higher altitude performence can be gained at the COST of poorer low altitude performance if you use a larger impeller. I now believe that the engine change wasn't necessary so much as putting one production line to work making "Interceptor" Hawks built for high altitude supercharging and maximum weight savings for rate of climb wherever they could get it.



That may be true but how much low altitude performance do you want to give up?
You still have to take-off and climb to combat altitude. 
Some of the later P-40s did trade 125hp at take-off for an extra 100 or so hp at 20,000ft. if you want several hundred HP than that several thousand feet higher then you are going to loose several hunderd more HP at sea level. Take- off and low altitude climb using less than 1000hp isn't going to impress too many peaple.


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## Elvis (Jul 15, 2009)

Shortround6 said:


> Clay_Allison said:
> 
> 
> > Higher altitude performence can be gained at the COST of poorer low altitude performance if you use a larger impeller. I now believe that the engine change wasn't necessary so much as putting one production line to work making "Interceptor" Hawks built for high altitude supercharging and maximum weight savings for rate of climb wherever they could get it.
> ...


Thus my suggestion for the adapting a second gear to the existing supercharger setup.
This way you don't loose anything down low and gain some up on top.
Bumping the c.r. only aids overall engine efficiency across the engine's entire powerband, but my main point (before bringing up the c.r. issue) was that the addition of a second gear would help the plane perform better at altitudes above 12K-15K feet.



Elvis


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## Elvis (Jul 15, 2009)

...something else that just struck me, but I've heard from others in the past.

What if a two-speed/two-stage S.C. were added to the Allison? (I'm thinking about the "-81" and "-99" engines, in this particular case)

Would that be a more "compact" system than re-installation of the turbo that was used in the P-38?


Elvis


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## Shortround6 (Jul 15, 2009)

Elvis said:


> Thus my suggestion for the adapting a second gear to the existing supercharger setup.
> This way you don't loose anything down low and gain some up on top.
> Bumping the c.r. only aids overall engine efficiency across the engine's entire powerband, but my main point (before bringing up the c.r. issue) was that the addition of a second gear would help the plane perform better at altitudes above 12K-15K feet.
> 
> ...



No you gain very little on top Or at least over 18-20,000ft.

Later single speed Allisons could give over 1100hp at 15,500ft. using 44in of boost. You are already operating at a pressure ratio of 2.6. even a better supercharger that could give a presure ratio of 3 to 1 at the same or better efficency so that the charge temperature doesn't go up will only give you about 50.7in of boost for about 1300hp at that altitude. 

You are going to gain a lot on the low end however. THe above Allison was good for 1200hp at take off so by using a second gear you could go back to the 1325HP take off rating of the lower altitiude Allisons. THe better supercharge would really improve things at 4-7000 ft for WER. 

Pulling a stiffer gear dosn't solve the limitations of the compressor itself. Maybe with a stiffer gear you could pull 1100hp at 16,500-18,000ft instead of 15,500ft but that isn't enough to turn the plane into a high altitude fighter. 

Try checking out the performance of single speed single stage Merlins and two speed single stage Merlins. Leave out the two stage merlins (the 60 series and 70 series engines) . Try comparing the Merlins from the same year and see what you get.


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## Shortround6 (Jul 15, 2009)

Elvis said:


> ...something else that just struck me, but I've heard from others in the past.
> 
> What if a two-speed/two-stage S.C. were added to the Allison? (I'm thinking about the "-81" and "-99" engines, in this particular case)
> 
> ...



Yes it was more compact but it was still over a foot longer than the regular Allison. IF you are using the Allison system. You are also not using an inter-cooler which does tend to limit the potential. Allison used water injection on the P-63 set-up with this engine. This is also the set-up used in the P-40Q.

If you are using a Merlin type set up it is a bit shorter but you still need the Inter-cooler and the inter-cooler radiator.


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## Clay_Allison (Jul 16, 2009)

Shortround6 said:


> That may be true but how much low altitude performance do you want to give up?
> You still have to take-off and climb to combat altitude.
> Some of the later P-40s did trade 125hp at take-off for an extra 100 or so hp at 20,000ft. if you want several hundred HP than that several thousand feet higher then you are going to loose several hunderd more HP at sea level. Take- off and low altitude climb using less than 1000hp isn't going to impress too many peaple.


I'd probably be willing to trade 250hp at sea level to get it back up high if it meant having a few squadrons capable of "bouncing" 109s from above in North Africa. Remember I'm also suggesting stripping it of all armor and two guns to get its rate of climb up. It would be well worth it to me just to let the Germans and Japanese know that they were not guaranteed an altitude advantade.

You know it's a damned shame that we didn't have P-47s available in the early phases of the war. The Jug was in its element at 35k feet with that turbocharger. No axis fighter pilot ever wanted to see a P-47 above them. You could beat one when you had energy or you were down on the deck, but fighting them from below meant he had all the cards.


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## Elvis (Jul 16, 2009)

......


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## Elvis (Jul 16, 2009)

Shortround6 said:


> No you gain very little on top Or at least over 18-20,000ft.
> 
> Later single speed Allisons could give over 1100hp at 15,500ft. using 44in of boost. You are already operating at a pressure ratio of 2.6. even a better supercharger that could give a presure ratio of 3 to 1 at the same or better efficency so that the charge temperature doesn't go up will only give you about 50.7in of boost for about 1300hp at that altitude.
> 
> ...


Just to clairify, you do realize when I mentioned a "second gear" in my prior post, I was suggesting a change from the single-speed setup to a two-speed setup.
I state that because you seem to go on about the limitations of a single speed setup and this has me wondering if you overlooked the fact that my post concerned changing to a two-speed setup.
Also, the advantage of the second gear _may_ not match the performance of, say, a P-47, but it would make the plane a _better_ performer at altitudes above 12K-15K feet, compared to the single speed version that was actually used during the war.
There's no way that it couldn't improve the plane's performance above the listed altitude range.

Concerning your comments on my question about adapting a two-speed/two-stage S.C. system to the Allison, yes, I was thinking about the British setup.

FWIW, I did some rather rudimentary calculations last night and based on the listed take off power of the Merlin and Griffon engines, it seems a similarly set up Allison would have a take-off HP rating in the 1600HP range.



Elvis


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## Shortround6 (Jul 16, 2009)

Elvis said:


> Just to clairify, you do realize when I mention a "second gear", I'm saying change the single speed setup to a two-speed setup.
> Also, the advantage of the second gear might not match, say a P-47, but it would make it better than the single speed versioin, wouldn't you agree?
> 
> 
> ...



I do realize what you mean buy a second gear.
A second gear can make a lot of difference to an airplane.
It just does't change things much at 20,000ft if the original single speed engine was already using a high altitude gear.

As far as not matching the P-47, the P-47 at 27,000 feet was getting a 5.2 to 1 pressure ratio from it's supercharger set up. A far cry from the 2.4 Pressure ratio of the Allison engine using 8.80 gears. 

The stiffer the gear the more power it takes to drive the supercharger. For instance the Allison required around 110-120 hp to the supercharger to get 10,000lb of air an hour uisng 6.44 gears. It required around 250 hp to get the same amount of air using 9.60 gears. So assuming you are at an altitude that both gears will allow the supercharger to deliver 10,000lb an hour the high gear ratio costs you 130 hp to the propellor. The advantage of the 2 speed supercharger. keeping performance at 15-20,000ft without sacrificing take -off and sea level power. Yes the stiffer gear does allow the supercharger to deliver the required air higher up but you are getting into diminsioning returns. Too stiff a gear is going to suck up almost all the extra power at a given altitude.
A large part of the power consumed goes into heating the intake charge so that doesn't help things. 

By the way the later 10.4" supercharger using 7.48 gears used almost the same amount of power as the 9.5in supercharger using 8.10 gears. They had about the same tip speed. The 10.4in supercharger could flow a larger volume however.


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## Elvis (Jul 17, 2009)

Shortround6 said:


> I do realize what you mean buy a second gear.
> A second gear can make a lot of difference to an airplane.
> It just does't change things much at 20,000ft if the original single speed engine was already using a high altitude gear.


Who says the single speed s.c. used "high altitude gearing"?
Its apparently a compromise, meant to give good performance at sea level and retain some semblence of that performace for as high up as they could get (and that appears to be in the 12K-15K foot range).
Of course, adding another gear is going to cost HP. This is the downfall of any gear-driven supercharger.
However, that faster gearing has to help in some way, otherwise even the vaunted two-stage systems would be single speed units.




Shortround6 said:


> As far as not matching the P-47, the P-47 at 27,000 feet was getting a 5.2 to 1 pressure ratio from it's supercharger set up. A far cry from the 2.4 Pressure ratio of the Allison engine using 8.80 gears.
> By the way the later 10.4" supercharger using 7.48 gears used almost the same amount of power as the 9.5in supercharger using 8.10 gears. They had about the same tip speed. The 10.4in supercharger could flow a larger volume however.


I only cited the P-47 for comparison purposes, so lets not drag that one into this conversation any more than is neccesary, please.
Thank you.
Interesting comparison you made with the two superchargers you listed.
Even though power usage is the same, the larger supercharger is still moving a larger volume of air, so it is having an even more positive affect on engine power output, compared to the smaller impeller.

If you really want to get hot and heavy with the calculator, try to figure out the gear ratio of the higher gear so that it creates the most NET power in the 15K-25K foot range.
I don't think I have the mathamatical capability to handle it, but if you feel up to it, please...be my guest.
It would be interesting to see how much different the higher gear ratio would be, compared to the lower one and what the increase in power would be.
If you need a "base line" to compare to, I believe the "-81" and "-99" engines made 1150HP on take-off 800HP @25000ft.

...also, I'd like to explore the idea of adapating the Birtish Two-Speed/Two-Stage S.C. to the Allison.
I'll see if I can find any evidence of that ever being attempted.



Elvis


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## Elvis (Jul 17, 2009)

While searching around for something on the Brit s.c.'d Allison, I ran across this thread from another form...

http://warbirdsforum.com/showthread.php?t=1282

Some very interesting comments in there.



Elvis


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## Shortround6 (Jul 17, 2009)

Elvis said:


> Who says the single speed s.c. used "high altitude gearing"?
> Its apparently a compromise, meant to give good performance at sea level and retain some semblence of that performace for as high up as they could get (and that appears to be in the 12K-15K foot range).
> Of course, adding another gear is going to cost HP. This is the downfall of any gear-driven supercharger.
> However, that faster gearing has to help in some way, otherwise even the vaunted two-stage systems would be single speed units."
> ...


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## Elvis (Jul 17, 2009)

So Shortround6, let's say you're a bright and enterprising young engineer who is sequestered by Allison to help them squeeze better performance out of the V-1710 engine.

What would _you_ do, to improve the high altitude performance of the Alllison,without sacrficiing its low altitude performance?

...and lets call the dividing line between "high" and "low" altitude that 12K-15K foot range I've been mentioning (in fact, if you like, you can call that range, "mid" altittude).


Elvis


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## Shortround6 (Jul 18, 2009)

Here is an interesting site:

motorgeek.com :: Turbo/Engine Flow Calculations and Maps

Just be sure to plug in some realalistic numbers.

To get manifold pressure as we know it you have to add the environmental air pressure to the boost pressure. And 0.5 pressure loss through an inter-cooler is a bit optomistic. 

THe program is for airflow requirements and does not take into acount riction with rpm orthe power needed to drive the supercharger. While it doesn't have anything for detonation limits the heat rise in the supercharger is interesting as are the intercooler and water injection sections. 

OF course nothing there considers size, cost, engineering time and other factors which decide wither something is done or not. 

And remember in WW II no computers. You had anywhere from a couple of men to a couple of hundred working at desks with sliderules, adding machines, and pencil and paper to do complex calculations. 

To get back to you question you have three basic choices.

1. A. Use a 2 speed gear box on the existing engine supercharger. 
Advantages=quick, cheap (both in engineering effort and manufacture) , minimal impact on engine size or weight so minimal (or no) problems installing in existing airframes. better take-off, low altitude (6-7000ft?) performance and climb.
Disadvantages= does nothing to improve perfomance at any hight above what the 81-99 engiens can already do. Some slight increase in intial cost and maitainence.
B. design larger capacity, higher effecincy 2 speed supercharger. 
Advantages= only a bit more expensive in engineering erfort and manufacture. Only a bit heavier and larger in volume so that installing in exisrting airframes should still be easy. 
Disadvantages= may only raise critical height (full throttle) by about 2,000ft, may do nothing for engine at lower altitudes compared to option A. 

2. use a 2 speed, 2 stage supercharger. 
A. Use a set-up like the Merlin. both impellors on a common shaft, always turning at the same speed. aftercooler not required but strongly recommended. 
Advantages= compact for a two stage supercharger. will boost performance into the low 20,000ft area, higher with aftercooler. cheapest 2 stage in terms of intial layout and set up.
Disadvantages=size and weight compared to option 1. may require a fair amount of deveopment time in impellor and diffuser design to "match" the superchargers. it will impact engine installationin existing airframes but probably not to an extent that prevents use.
B. Use set up Like U.S. Navy. 1st stage (auxilary stage) supercharger has it's own 2 speed gearbox with clutch whihle engine has a single speed drive. Auxilery supercharger is dis-engaged for take off/low altitude to save power. Lowgear is engaged for medium altitude and high gear used for high altitude. Intercooler used when 1st stage is engaged.
Advantages= good high altitude performance with no real engine penelities at low altitudes, being able to vary the speeds of the 1st impellor may make supercharger m"matching" easier?
Disadvantages=weight and bulk are starting to get even bigger. engineering time could be getting rather large and the intercooler if aircooled is no longer universal but specific to each air frame. 
C. As in B but using a hydralic drive to the first stage. This is what Allsion was working on. Allison also skipped the intercooler and substituted water injection instead. Trade voume of intercooler for smaller but denser ADI tank. 

3. Use a turbo-charger. Already being done.
Advantages= Great high altitude performance
Disadvantages= weight and bulk of installation make a tremendous impact on airframe. Maintainence issues for part of the war and perhaps an allocation of resources problem.

So as a bright young spark which way do you go? quick and cheap with limited performance or long and expensive with high performance.


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## Elvis (Jul 19, 2009)

> So as a bright young spark which way do you go? quick and cheap with limited performance or long and expensive with high performance.


Hey now, don't be smart young man, or I'll have you doing coffee runs for the whole shop in that leaky old 
P-12 we've got parked out back.

Please refrain from throwing the question I posed to you, back at me, without answering it first.
That's very poor form to do otherwise.



Elvis


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## Shortround6 (Jul 19, 2009)

Elvis said:


> Hey now, don't be smart young man, or I'll have you doing coffee runs for the whole shop in that leaky old
> P-12 we've got parked out back.
> 
> Please refrain from throwing the question I posed to you, back at me, without answering it first.
> ...



Well, I gave you 6 options in total. I just didn't pick one. To narrow the choice you have to be more specific with the question. 

How much improvement are you looking for?
When is the start of the project (1940 or 1944)?
How soon do you want the engine in production( 3 months from start of project or 2years)?
what airframes do you want to use it in?

we will leave finicial costs out of it for now. I sure don't have enough information on that area to do moe than take a wild guess.

The best choice from a pure perfomance standpoint of the engine was the turbo charger option but they were already working on that one and it might not fit (in fact it didn't fit ) in all airframes.


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## Elvis (Jul 20, 2009)

Why are you giiving _me_ options?

I asked YOU.

What would YOU do, based on the knowledge you've gained over the years as professoinal mechanic.
Forget the BS parameters you mentioned in your last post, just tell me what you would do.
That's all I'm asking.

...and Charlie wasnts 2 cearms, non-fat, and one sugar, non-saccarin, in his coffee. There's a good lad. Thanks sport. 


Elvis


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## Clay_Allison (Jul 20, 2009)

Shortround6 said:


> Well, I gave you 6 options in total. I just didn't pick one. To narrow the choice you have to be more specific with the question.
> 
> How much improvement are you looking for?
> When is the start of the project (1940 or 1944)?
> ...


I think 1940 is the time frame to focus on and the question is, "How do you get a high-altitude interceptor available to the US by Jan 1942.

Assuming you want to use the P-40 airframe, how do you fix the power plant to get high altitude performance and decent rate of climb?


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## Elvis (Jul 22, 2009)

You help the British develop the Griffon V-12 and park that little puppy under the "hood".





Elvis


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## Shortround6 (Jul 22, 2009)

Clay_Allison said:


> I think 1940 is the time frame to focus on and the question is, "How do you get a high-altitude interceptor available to the US by Jan 1942.
> 
> Assuming you want to use the P-40 airframe, how do you fix the power plant to get high altitude performance and decent rate of climb?



Stick a rocket in the thing and pray

Attemps by Curtiss to build newer fighters than the P-40

Fact Sheets : Curtiss XP-46 : Curtiss XP-46

A contract for two aircraft was signed on Sept. 29, 1939.

Fact Sheets : Curtiss XP-53 : Curtiss XP-53

Two prototypes, designed for the Continental XIV-1430-3 inverted Vee engine, were ordered in October 1940.

Fact Sheets : Curtiss XP-60 : Curtiss XP-60

XP-60 ordered 6 weeks after the XP-53.THE XP-60 prototype first flew 18 September 1941 with Merlin engine.Curtiss was given a contract for 1,950 P-60A'swith turbo-charged Allisons on October 31st, 1941.
Contract Changed after Peral Harbor to 1400 P-40s and 2,400 P-47s.
Jan 1942 Curtiss is given contracts for 1 each: XP-60A. XP-60B, XP-60C and XP-60D

Curtiss was well aware of the fact that the P-40 was not in the forefront of world fighters and was trying to come up with a new airframe.


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## Elvis (Jul 22, 2009)

Shortround6 said:


> Fact Sheets : Curtiss XP-60 : Curtiss XP-60
> 
> XP-60 ordered 6 weeks after the XP-53.THE XP-60 prototype first flew 18 September 1941 with Merlin engine.Curtiss was given a contract for 1,950 P-60A'swith turbo-charged Allisons on October 31st, 1941.
> Contract Changed after Peral Harbor to 1400 P-40s and 2,400 P-47s.
> ...


I think this excerpt from the XP-60 page says a lot, as to why the Allison was never developed as "fully" during the war, as was the Merlin...



NMUSAF's XP-60 page said:


> The Army Air Corps wanted a "Merlin"-powered aircraft...


...and isn't it funny how, after the war, when R-R wanted us to start paying royalties on further production of the Packard-Merlin engine, that the Allison "suddenly" became a 2000+HP engine and P-M production was halted.





Elvis


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## Clay_Allison (Jul 22, 2009)

It might have been possible to create a successor to the P-40 with the easily available Wright R-2600. There is a significant dry weight difference in the engines, but perhaps not as much in installed weight. 1600 Horses would be a huge jump in power from 1100. Also I think our supercharger technology for radials was much better developed.


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## Elvis (Jul 22, 2009)

...another way to go about this is to go back to the P-37 design, but modify it by utilizing a tricycle landing gear arrangement.
This would essentially eliminate the pilots lack of "view" when taxiing and allow the P-36/P-40 airframe to (more) successfully utitilize the Turbo-Supercharged version of the Allison.


Elvis


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## Colin1 (Jul 22, 2009)

Elvis said:


> ...another way to go about this is to go back to the P-37 design, but modify it by utilizing a tricycle landing gear arrangement.
> This would essentially eliminate the pilots lack of "view" when taxiing and allow the P-36/P-40 airframe to (more) successfully utitilize the Turbo-Supercharged version of the Allison


Elvis
I'm not sure how you'd get that to work, there is an awful lot of aeroplane behind the main landing gear on the P-37 and even if you did somehow persuade it to keep its nose gear on the ground, where would the nose gear fold into?

Have a look at the P-37 in profile in Aviation Pictures/Curtiss P-40 Pictorial History, it really is a non-starter.

The pilot's lack of view while taxying was something that prop job drivers just learned to live with, sure, there were tails chewed off the guy in front and worse but by and large, they coped with it.


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## Shortround6 (Jul 22, 2009)

Clay_Allison said:


> It might have been possible to create a successor to the P-40 with the easily available Wright R-2600. There is a significant dry weight difference in the engines, but perhaps not as much in installed weight. 1600 Horses would be a huge jump in power from 1100. Also I think our supercharger technology for radials was much better developed.



Depends on which company is making the Radial.
Wright either used a two speed single stage or used turbos. 
P&W actually built two stage engines for Wildcats 2 years before the Merlin 60 series showed up. 
I have no details on the installation or much on it's performance except it allowed the R-1830 to give 1200HP at sea level and 1000HP at 19,000ft. Theree are some accounts of 'surging" troubles with this engine. 
P&W used both rather complicated 2 stage systems on the R-2800 and turbos. 

The Early Wright R-2600s were rated at about 1400hp at 12,000ft for military power and that is high gear. The 1700hp engines in the B-25Ds were rated at 1700hp at 12,000ft for 5 minutes. While the engine is 550-600lbs heavier than the Allison you do get the ditch the radiators and coolant to save some weight. 
what you can't ditch is the strange fact that the R-2600 is actually about 1.5" larger in diameter than an R-2800 and has about 1 square foot more frontal area
or 16sq.ft. compared to the Allisons 6.1-6.2sq.ft.
of course after factoring in the radiators and oil coolers and the fact that even a liquid cooled engine needs a little air flowing over the outside of it things aren't quite that bad.

Granted good cowling can make up for a lot but in 1941-42 really low drag cowlings for aircooled engines were few and far between.


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## Shortround6 (Jul 22, 2009)

Colin1 said:


> Elvis
> I'm not sure how you'd get that to work, there is an awful lot of aeroplane behind the main landing gear on the P-37 and even if you did somehow persuade it to keep its nose gear on the ground, where would the nose gear fold into?
> 
> Have a look at the P-37 in profile in Aviation Pictures/Curtiss P-40 Pictorial History, it really is a non-starter.
> ...


 
Another problem with long noses is deflection shooting. If both planes are turning and the pursuer has to "lead" the target there is only so much lead that can be applied before the target disappears below the nose. 

Bell had also schemed a "model 3" a little earlier than the Aircobra (the model 4). imagine an Aircobra with the engine move forward but still leaving room for a 25mm cannon in front with the pilot sitting not only behind the engine but behind the trailing edge of the wing.

The state of the art in turbo installations in 1939-40-41 was actually pretty dismal. Lots of potential when things worked right but too often they didn't and minor problems, like way higher than estimated drag, caused the potential not to be realised for a while longer.


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## Clay_Allison (Jul 22, 2009)

Why was the P-40 so much heavier than the P-36 anyway? The P-36 had a loaded weight of 5,600 lb, the P-40 wound up being 8,200. There had to be some way to just put upgraded R-1830 engines (or even R-2000) in the P-36 and add guns and resealing fuel tanks for less than 2,800 pounds. The P-36 was very well liked by the Finns and the French pilots who flew them. You'd think that they could have continued to be developed as an all-altitude dogfighter to supplement their heavy ground-pounding counterpart.


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## Elvis (Jul 23, 2009)

Clay,

Maybe the P-40 was heavier due to balancing out the heavier V-12 engine?
...just a guess.
FWIW, I think most of the importP-36's were actually powered by R-1820's.
This is actually a lighter weight engine than either the R-1830 or R-2000.
Notice the nose of an FM-2 compared to an F4F sometime. Notice the FM's nose looks longer?
That's because there's about 187 lbs. difference between the P&W engine and the Wright, so the Wright engine was placed a little farther away from the firewall in order to help balance the plane out.
----------------------------------------------------------------------

Shortround, 

I'd have to to research the bore and stroke of the R-2800 and R-2600, but I seem to remember the Wright engine having an unusually long stroke....possibly longer than that of the P&W.
This would probably account for the increased surface area of the R-2600, compared to the R-2800.

...and feel do that research for me, if you like. 


Elvis


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## Shortround6 (Jul 23, 2009)

Elvis said:


> Clay,
> 
> Maybe the P-40 was heavier due to balancing out the heavier V-12 engine?
> ...just a guess.
> ...



THe Wright engine was a 9 Cyllinder single row radial while the P&W R-1830 was a 14cylinder 2 row radial. Depending on model the P&W engine could be a foot longer. Of course this is measured from the front of the propellor shaft to the end of the last accessory ( generator, fuel pump, vacumm pump,etc) bolted to the back of the engine.

I should hope the R-2600 used a longer stroke, it was a 14 cylinder engine after all But it was only .3125in (8mm) longer. It used the same sized cyliinders as the Wright R-3350 and strangly enough, depending on model and source, the two Wright engines had the same diameter.
It's problem as a fighter engine from a design standpoint ( I have no idea if there were service issues) was that for slightly less frontal area the P&W R-2800 offered more power. The 150-400hp advantage of the P&W (depending on year, model, etc) was probably enough to offset it's greater weight.


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## Shortround6 (Jul 23, 2009)

Clay_Allison said:


> Why was the P-40 so much heavier than the P-36 anyway? The P-36 had a loaded weight of 5,600 lb, the P-40 wound up being 8,200. There had to be some way to just put upgraded R-1830 engines (or even R-2000) in the P-36 and add guns and resealing fuel tanks for less than 2,800 pounds. The P-36 was very well liked by the Finns and the French pilots who flew them. You'd think that they could have continued to be developed as an all-altitude dogfighter to supplement their heavy ground-pounding counterpart.



Again the"all-altitude" problem is a supercharger problem. Even early models of the Merlin 61 were compressing the ambiant air at 23,500 ft by a factor of 5.1 to 1. No singlestage supercharger can match that no matter how many gears are put on it. And that is for a power output of 1,390HP. 

While there is some weight growth on the P-40 that is hard to account for you do have to make sure you are comparing apples to apples. For instance the P-36A at 5,600lbs had only one .50 cal gun and one .30 cal gun. It might also have had only 105 US gallons of fuel on board. There was an internal auxilary tank of 57 gallons and the P-36A is also listed as having a MAX gross weight of 6,010 pounds. 

To try to equilize things the P-36A in one source says 4,567lb empty compared to the XP-40s 5,417lb empty and 6,260lbs with 100gallons of fuel. Production P-40s ( two .50 cal guns only) are given as 6,787lbs "normal " gross weight which I interperate as with 100-105 gallons of fuel ( XP-40 weighed 83lbs more than that with overload fuel). By the time we get to the P-40C the empty equiped weight (with some armour and self sealing tanks) is 5,812lbs and normal loaded is 7,549lbs. Now you have added 85-90lbs worth of .30 cal guns in the wings and about 100lbs of .30cal ammo. but not including gun mounts, heaters, ammo boxes etc. 

How much of the 850 pound difference between a P-36A and the XP-40 is due to other things than the engine swap I don't know. 

One spec for a P&W R-2000 that I have found gives a weight of 1595lbs a take off rating of 1450HP but a military rating (NOT WER) of 1100hp at 16,000ft in high gear. Not sure of the year of the engine.


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## Clay_Allison (Jul 24, 2009)

Shortround6 said:


> Again the"all-altitude" problem is a supercharger problem. Even early models of the Merlin 61 were compressing the ambiant air at 23,500 ft by a factor of 5.1 to 1. No singlestage supercharger can match that no matter how many gears are put on it. And that is for a power output of 1,390HP.
> 
> While there is some weight growth on the P-40 that is hard to account for you do have to make sure you are comparing apples to apples. For instance the P-36A at 5,600lbs had only one .50 cal gun and one .30 cal gun. It might also have had only 105 US gallons of fuel on board. There was an internal auxilary tank of 57 gallons and the P-36A is also listed as having a MAX gross weight of 6,010 pounds.
> 
> ...


The F4F-3 had a two-stage supercharger with the same engine though with the R-1830-76 engine, P&W alone (apparently) among American engine makers saw the need to develop a two-stage supercharger and one was available for the R-1830 before pearl harbor! It seems pretty clear that the engine switch was a mistake and that the successor to the P-36 in whatever form should have had the R-1830.


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## Shortround6 (Jul 24, 2009)

Clay_Allison said:


> The F4F-3 had a two-stage supercharger with the same engine though with the R-1830-76 engine, P&W alone (apparently) among American engine makers saw the need to develop a two-stage supercharger and one was available for the R-1830 before pearl harbor! It seems pretty clear that the engine switch was a mistake and that the successor to the P-36 in whatever form should have had the R-1830.



I have been able out find out very little about the R-1830-76 engine except that is was supposed to have "surging problems" and that later versions of the Wildcat (like the F4F-4) went back to a 2 speed single stage supercharger. A 2 stage R-1830 was also used in the XP-41 according to some sources.
This engine was rated at 1200hp at 2700rpm for take-off and had max continous ratings of 1050Hp at sea level, 1080hp at 4000ft, 1080hp at 11,000ft and 1050hp at 17,500ft all at 2550rpm. it aslo weighed 200lbs more than a single stage R-1830.
Army went with Turbo-ed R-1830s in the P-43s, I don't know if the Army was still favoring the Turbos in therory but the record of the P-43s shows that Turbos weren't quite ready for prime time at that time. 
By the way, an experimental P-36 (actually the company owned demonstrator hawk 75R) with a turbo was reported to have made 330mph at 15,000ft and compeated in the same trails that saw the P-40 adopted.


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## Clay_Allison (Jul 24, 2009)

Shortround6 said:


> I have been able out find out very little about the R-1830-76 engine except that is was supposed to have "surging problems" and that later versions of the Wildcat (like the F4F-4) went back to a 2 speed single stage supercharger. A 2 stage R-1830 was also used in the XP-41 according to some sources.
> This engine was rated at 1200hp at 2700rpm for take-off and had max continous ratings of 1050Hp at sea level, 1080hp at 4000ft, 1080hp at 11,000ft and 1050hp at 17,500ft all at 2550rpm. it aslo weighed 200lbs more than a single stage R-1830.
> Army went with Turbo-ed R-1830s in the P-43s, I don't know if the Army was still favoring the Turbos in therory but the record of the P-43s shows that Turbos weren't quite ready for prime time at that time.
> By the way, an experimental P-36 (actually the company owned demonstrator hawk 75R) with a turbo was reported to have made 330mph at 15,000ft and compeated in the same trails that saw the P-40 adopted.


The army's obsession with Turbos (along with their general dismissal of high altitude performance) was the single most unfortunate idea that existed in prewar aerial doctrine with the possible exception of the self-defending bomber. The two problems were, of course, related since the lack of a recognized need for escort fighters led to an obsession with low-altitude performance at the cost of air superiority.

Still, the -76 existed and the two-stage supercharger was worth 200 pounds. A little development and we could have had an all altitude fighter with 4 guns, self-sealing tanks, and a little pilot armor at 6250 pounds loaded.


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## Elvis (Jul 24, 2009)

Shortround6 said:


> THe Wright engine was a 9 Cyllinder single row radial while the P&W R-1830 was a 14cylinder 2 row radial. Depending on model the P&W engine could be a foot longer. Of course this is measured from the front of the propellor shaft to the end of the last accessory ( generator, fuel pump, vacumm pump,etc) bolted to the back of the engine.
> 
> I should hope the R-2600 used a longer stroke, it was a 14 cylinder engine after all But it was only .3125in (8mm) longer. It used the same sized cyliinders as the Wright R-3350 and strangly enough, depending on model and source, the two Wright engines had the same diameter.
> It's problem as a fighter engine from a design standpoint ( I have no idea if there were service issues) was that for slightly less frontal area the P&W R-2800 offered more power. The 150-400hp advantage of the P&W (depending on year, model, etc) was probably enough to offset it's greater weight.


It appears the R-2600 is a de-stroked, 14-cylinder version of the R-1820 (6.125 x 6.3125 vs. 6.125 x 6.875) so I must've been thinking of a different engine, when I made my "unusually long stroke" comment in an earlier post.
Still, the R-2800 had a slightly shorter stroke (6") than R-2600, which _should_ translate to a shoter cylinder, thus the lessened frontal area, in comparison to the Wright engine.
The R-2800's main attributes were lots of power (pretty much more than anything else we had) along with lots of reliability.
There's many stories of R-2800 powered aircraft still running well enough to bring the pilot home, despite severe battle damage.
That kind of reputation will get you work, and lots of it!
------------------------------------------------------------------------------------

Shortround,

I don't know what you're getting at with the comments about the length of afforementioned engines. We were discussing the different in frontal area of those engines, but I'm sure it'll be pertinent information somewhere down the line, so thanks for conveying that anyway.



Elvis


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## Elvis (Jul 24, 2009)

Elvis said:


> Clay,
> 
> Maybe the P-40 was heavier due to balancing out the heavier V-12 engine?
> ...just a guess.
> ...


The information I relayed in this post, that I've highlighted in the quote, is incorrect.
Sorry about that guys, I was thinking of a different comparison when I wrote that.
According to the Aviation-History page on both the R-1830 and the R-1820, the difference in the listed weights of those engines (geared version) is only 102 lbs.




Elvis


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## Elvis (Jul 24, 2009)

Shortround6 said:


> I have been able out find out very little about the R-1830-76 engine except that is was supposed to have "surging problems" and that later versions of the Wildcat (like the F4F-4) went back to a 2 speed single stage supercharger. A 2 stage R-1830 was also used in the XP-41 according to some sources.
> This engine was rated at 1200hp at 2700rpm for take-off and had max continous ratings of 1050Hp at sea level, 1080hp at 4000ft, 1080hp at 11,000ft and 1050hp at 17,500ft all at 2550rpm. it aslo weighed 200lbs more than a single stage R-1830.
> Army went with Turbo-ed R-1830s in the P-43s, I don't know if the Army was still favoring the Turbos in therory but the record of the P-43s shows that Turbos weren't quite ready for prime time at that time.
> By the way, an experimental P-36 (actually the company owned demonstrator hawk 75R) with a turbo was reported to have made 330mph at 15,000ft and compeated in the same trails that saw the P-40 adopted.


From what info I've picked up on the web, concerning the R-1830 (mainly when used in the Wildcat), the "-76" version of that engine used an older cylinder head design and suffered from (lack of) cooling problems. 
The replacement "-86" and "-90" engines addressed this issue and made the engine more reliable with a longer TBO period.
This was augmented by mods to the prop and cowling, to further improve cooling of the engine.


Elvis


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## Clay_Allison (Jul 24, 2009)

I always heard that the F4F operated fine at altitude if you could get it there. The problem was the climb rate from having an overly heavy plane.


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## Elvis (Jul 24, 2009)

Clay, 

That metality is derived mainly from the "-4" / FM-1 version of the Wildcat.
Much like the later versions of the Brewster Buffalo before it, the plane was modified with more armour, fuel capacity and guns, gaining quite a bit of weight, while the powerplant was never addressed.
This degraded certain performance aspects that made it even less of an adversary for the Zero and other axis aircraft.
As for climb rate in particular, the "-3" actually wasn't too bad, for a pre-war aircraft. 2350 ft./min. is the figure I often see for that one.
However, the above mods slowed the ascent rate to 1950 for the "-4" / FM-1.
The problem seemed to be corrected fairly quickly, though and the next version, the FM-2, was re-engined and re-designed to make it (probably) the best version that existed.
The FM-2 had a climb rate of 3650 ft./min. and had a top speed in the 320-330 mph range.
Those two performance aspects, alone, made it a much better adversary to the Zero than the "-4" could've ever hoped to have been.
FWIW, there were more FM-2's built than any other version of the Wildcat. In fact, I believe FM-2 production alone exceeds the total number of Wildcats that were built before it.
According to the History of War website, "_In all 7,885 Wildcats were produced by Grumman and General Motors. Over 60% were General Motors produced FM-2s. 1,100 were supplied to the Royal Navy._'
Again, according to their production figures, there were 4,777 FM-2's built during the war. This leaves only 3,108 Wildcats that _weren't_ FM-2's.



Elvis


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## Shortround6 (Jul 24, 2009)

You are quite right about the performance of the FM-2 but since the first one wasn't delievered from the factory until sept of 1943 or 9 months after the Hellcat stared to be delivered or just 2 months before the P-51B arrives in England the FM-2 and it's engine don't realy solve the early 1942 problem.


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## Elvis (Jul 25, 2009)

....yeah, and?  


Elvis


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