Why were U.S. pursuit fighters at the start of WW2 of lower performance than European fighters?

[to_change22]

There was a wide consensus in U.S. military circles ~1939-1940 that U.S. pursuit fighters were substantially less capable in terms of performance than their equivalent European counterparts. Specifically, in Germany, the BF109-E (the first version to use the Daimler-Benz DB-601 engine) began production in 1938, while the original airframe was designed in 1934. In Britain, the Spitfire airframe was designed in 1935 and the airplane went into production in 1938. The single-engined fighters which were being developed in the U.S. at the same time included the Seversky P-35, Bell P-39, and Curtiss P-40 (derived from the P-36). There was wide belief - confirmable by various performance metrics - that the U.S. fighters were inferior.

What accounted for this difference in performance?
Of note: I am looking mostly for an engineering answer, and references would be greatly appreciated!

Advances in in aircraft performance are generally governed by developments in 1) aerodynamics 2) propulsion and/or 3) structures.

Keeping this in mind, the most obvious causal factor in the superior performance of European fighters is that the European engines available for use in the 1935-40 timeframe were of higher performance in terms of P/W ratio (particularly at altitude) than similar engines then available in the U.S. The German DB-601 and British Rolls Royce Merlin engines were both superior to the American Allison engine, the only serious V12 the U.S. produced in the late 1930s. It would take until 1940 for the U.S. radial engine makers to launch high-output versions of their radial engines (e.g. supercharged R-2800s) and of course the U.S. capitalized on the high-performance, liquid-cooled Merlin for use in the P-51.

So the question is, was the entire scope of the performance difference due to powerplants alone or whether there were other salient developments in aircraft aerodynamics and/or structures that help account for the superior performance of British and German fighters to start the war.

I think the best way to do this comparison is to compare three specific aircraft c. 1940: 1) The BF-109E 2) The Spitfire Mk1 (or Mk2) 3) The Curtiss P-40 (alternatively, substitute the P-39).

Note - I am being very specific to the timeframe of 1935 - 1940 because later U.S. developments, such as the P-51 Mustang, F6F, etc., largely corrected much of the performance deficit. While one could still argue on the margins about the superiority of one design over the other, there was no longer a consensus amongst the U.S. military officials that their pursuit fighters were inferior.

Note 2 - there is a difference between a design choice & a technical advance. German and British fighters also may have had higher performance on the metrics I mentioned above not because German's had specific ideas that were more advanced than the U.S.'s designers, but also because they were designed to do with different goals in mind. I have tried to equalize by not comparing aircraft designed for obviously different goals (eg, a twin-engined interceptor vs. a single-engined fighter). But there still might be some differences. For example, U.S. fighters might have been heavier (thus reducing climb rates) because the USAAC put more emphasis on armor protection than the RAF did. If that is the answer, happy to hear that too. Just want to know!

 

[tomo pauk]

Keeping this in mind, the most obvious causal factor in the superior performance of European fighters is that the European engines available for use in the 1935-40 timeframe were of higher performance in terms of P/W ratio (particularly at altitude) than similar engines then available in the U.S. The German DB-601 and British Rolls Royce Merlin engines were both superior to the American Allison engine, the only serious V12 the U.S. produced in the late 1930s. It would take until 1940 for the U.S. radial engine makers to launch high-output versions of their radial engines (e.g. supercharged R-2800s) and of course the U.S. capitalized on the high-performance, liquid-cooled Merlin for use in the P-51.

Several notes from the start:
- V-1710 could be barely be called a late 1930s engine when it is about actual, in-service use (eg. the 1st P-40 (so suffix) was delivered in June 1940, some 20 months after the 1st Bf 109E was delivered). However, it's 'altitude power was a tad better than what DB 601A did in mid-1940, and slightly lower than that of Merlin II or III
- Unfortunately for the V-1710, both Merlin and DB 601 were being improved at increased speed, and by 1941 the V-1710 was lagging behind a lot wrt. 'altitude power', while strugling in 1941 to even reach the 'book' power values - at least on P-40 - being down-rated in both RPM and boost allowed in service.
- We can note that P-40 (no suffix) was as fast as the much smaller Bf 109E3, and almost as fast as the Spitfire I; P-40 will climb less well since it was heavier than these two, and gotten ever heavier as the ww2 progressed
- P-39C was on par with speed with Spitfire V and under, and with Bf 109F1 and F2, despite having a lesser engine (European fighters will be faster above ~17000 ft, though); increase in weight and drag, coupled together with no increase of 'altuitde power' until late 1942 meant that P-39D, L and K were hopeless above 15000 ft vs. the fighters of note, both in speed and climb
- Stating that R-2800 was supercharged is superfluous - all ww2 aero engines of interest were supercharged

So the question is, was the entire scope of the performance difference due to powerplants alone or whether there were other salient developments in aircraft aerodynamics and/or structures that help account for the superior performance of British and German fighters to start the war.

I think the best way to do this comparison is to compare three specific aircraft c. 1940: 1) The BF-109E 2) The Spitfire Mk1 (or Mk2) 3) The Curtiss P-40 (alternatively, substitute the P-39).

P-40 was no more draggy than the Spitfire or Bf 109E. If the bullet-proof glass is installed on the European fighters, as it was the case from mid-1940, it will add drag.
P-39 was less draggy than Spitfire or Bf 109E. Problem with P-39 is that it realistically cannot be called a 1940 fighter.

Note 2 - there is a difference between a design choice & a technical advance. German and British fighters also may have had higher performance on the metrics I mentioned above not because German's had specific ideas that were more advanced than the U.S.'s designers, but also because they were designed to do with different goals in mind. I have tried to equalize by not comparing aircraft designed for obviously different goals (eg, a twin-engined interceptor vs. a single-engined fighter). But there still might be some differences. For example, U.S. fighters might have been heavier (thus reducing climb rates) because the USAAC put more emphasis on armor protection than the RAF did. If that is the answer, happy to hear that too. Just want to know!

It was the other way around - Europeans were 1st to introduce armor and self-sealing tanks on their fighters (and other combat aircraft). American aircraft were heavier mostly due to carrying more fuel, eg. the P-40 started out with 180 US gals of fuel, while Hurricane, Spitfire and Bf 109E were carrying +-100 US gals. Bigger fuel tanks will require heavier self-sealing tanks, and will not favor a small aircraft to begin with. Three tanks will require more self-sealing materials than if the A/C has just one or two. A fighter that is not small and it is heavy will not climb well, even if the increse in weight is not hurting the top speed too much.
Bf 109 stated out with a 650 HP engine, ~70 US gals of fuel and was supposed to carry just two LMGs; that, coupled with Messerschmitt's gamble with not adhering to the prescribed wing loading value allowed the resulting A/C to be small and light. Once the major engine upgrade happened (DB 601A in the nose), size remained about the same, and the weight was still modest - the 109E became an excellent fighter.

 

[SaparotRob]

My uneducated opinion is that with the U.S. comfortably behind its ocean defenses, fighters weren't a priority. Small enemy fighters just weren't going to make it here. The only way they could get here would be by aircraft carriers. I'd bet a large sum of your money that in 1940, the U.S. carrier planes were better than any of the European nations carrier planes. A long range patrol bomber would be more useful.

 

[glennasher]

I suspect that range was a huge consideration, too. The smaller European fighters were designed mostly for point defense on their own borders, of much smaller countries, compared to the US. Range isn't a big consideration for, say, the Dutch or Belgians, compared to what might be required for point defense of the US.
Then you add the "stuff" required for modern fighting aircraft, selfsealing tanks, armor, bulletproof windshields, etc., as noted above, and you're getting a completely different aircraft being planned and built for a completely different set of circumstances.

 

[Geoffrey Sinclair]

A number of reasons, not in any order. The development cycle, all air forces knew it would take longer from specification to service compared with WWI but were generally surprised by how much longer, and engines were much worse than airframes. The urgency in Europe versus the US. The amount of money for higher performance prototypes, the US military was a much smaller percentage of the aviation market than in Europe, and the civilian market had different improvement priorities. Germany was pushing its aviation industry hard but in number, not airframe weight terms, was building comparable numbers to the depression hit US one in the late 1930's. Specifications based on the expected next war, the US started to put more supercharging in to bombers before fighters, giving the 1930's US fighters an altitude problem, the P-40 was essentially the P-36 with a liquid cooled engine. Throughout the inter war years the which is best, radial or liquid cooled swung back and forth as improvements were made. The Allison was a crucial couple of years behind the Merlin and DB601 and would hit the initial wartime problem of you can have improved versions or more standard ones, choose. Think of how many US civil types used liquid cooled engines in the 1930's. Lots of European designs used NACA research material, the US was publishing a lot of cutting edge data.

Armour and self sealing fuel tanks were standard in the Luftwaffe pre war, becoming standard in the RAF at the outbreak of war and came to the US in 1940. Overall US fighters tended to be heavier.

Depression economics cut back military spending, the final P-26C arrived in March 1936, the P-30/PB-2A April to July 1936, the P-35 had 3 accepted July to November 1937 then production December 1937 to August 1938, the first 3 P-36A were accepted in May 1938 then production September to March 1939 with 177 accepted, P-36C 1 in December 1938 then 30 March to May 1939. Sweden bought the P-35 and the order was built in 1940. While Curtiss turned out 274 P-36 types for export 1938/39, and 481 in 1940, surely the design was not that bad? Compared to the Hurricane and Bf109D? P-40 production began in May 1940, ignoring the YP-38 and 39 the P-38 and P-39 were 1941 aircraft. Note the rather large time gap in USAAF fighter production. Over at the USN the 1935 fighter was the F2F, the 1936 on the F3F-1, the 1938 one the F3F-2, the 1939 one the F3F-3, the late 1939/early 1940 one was the F2A. Or to put it another way USN fighter production 1935 to 1939 was by year 56, 56, 15, 70, 44 (6 for Finland). USAAF fighter types was 7, 67, 11, 260 (82 P-36 for foreign orders), 310 (192 foreign P-36).

 

[EwenS]

My uneducated opinion is that with the U.S. comfortably behind its ocean defenses, fighters weren't a priority. Small enemy fighters just weren't going to make it here. The only way they could get here would be by aircraft carriers. I'd bet a large sum of your money that in 1940, the U.S. carrier planes were better than any of the European nations carrier planes. A long range patrol bomber would be more useful.

You sure? The only European nation with operational carriers in 1940 was Britain. The French Bearn was little more than a transport by that point.

In 1940 the main US carrier fighter was still the bi-plane Grumman F2F/F3F series with max speeds of 231/264mph, and remained so into 1941. Performance comparable to the Sea Gladiator, Skua and Fulmar I.

By June 1940 VF-3 on Saratoga had received the first 10 Brewster F2A-1 Buffalo. These were the only deliveries of that model to USN squadrons. Deliveries of the F2A-2 only started in Sept 1940 and it was 1941 before this version reached its first two squadrons, VF-2 &VF-3 on Lexington & Saratoga.

The first 22 F4F-3 Wildcats built for the USN didn't begin to reach squadrons VF-4 & VF-7 on Ranger & Wasp until Dec 1940.

 

[SaparotRob]

I'm standing pat. We definitely had superior aircraft carrier capabilities over any of the European Axis powers hands down.

 

[Shortround6]

The single-engined fighters which were being developed in the U.S. at the same time included the Seversky P-35, Bell P-39, and Curtiss P-40 (derived from the P-36). There was wide belief - confirmable by various performance metrics - that the U.S. fighters were inferior.

even 1935 to 1940 covers a huge chunk of time in propeller aircraft design. The P-35 entered in service in 1938 and was running late. It might have compared rather well to European fighters of 1938. First Squadron Spitfires only went operational with them in Dec of 1938, Hurricanes had fixed pitch props, very few (if any service) 109s had DB 601 engines. P-35A's were commandeered export Swedish planes. The P-40s were sort of in no man's land in 1940, they could perform just about as well as any European fighter except the Spitfire but they weren't actually combat ready. They were not fitted with protective equipment until the end of the year and the .50 cal guns which made up 1/2 of their fire power were not suitable for combat in 1940 (or even part of 1941). However the P-40 was faster than the Hurricane and it was just about as fast as the 109E-3/4 while being a larger/heavier aircraft.

. It would take until 1940 for the U.S. radial engine makers to launch high-output versions of their radial engines (e.g. supercharged R-2800s)

This rather ignores the two stage supercharged Twin Wasps in the Wildcats (made in small numbers in 1940) and the 1200hp Wright Cyclones (admittedly an oil problem or two) and the Wright R-2600. not used in fighters but was being loaded into A-20s (over 1900 R-2600s built in 1940, nobody else came close).

Where the US did drop the ball was in being too ambitious and going for brand new designs and/or not improving the P-40 in a good way in 1940/41. Going to catch a lot of flak for that
The P-39 and P-40 were good basic designs, but the US overloaded them with guns and later with protective equipment while the engine design stayed pretty much static.

For most of 1940 the Allison engine was as good as the Merlin or DB601 in basic design. Trouble was that they were so busy getting it into mass production that all they did in 1940/41 was change the propeller reduction gear box and strengthen a few parts to allow the 1040/1090hp engine to make 1150hp at a lower altitude and then they stuck it in much heavier aircraft.
Problem here is that the Merlin was not sitting still. The Merlin XII showed up just before the BoB in the first Spitfire IIs and was strengthen Merlin III and the Merlin XX showed up in Sept 1940 in the first Hurricane IIs with two speed supercharger (from the Merlin X bomber engine) and Hooker improved supercharger. Spit V showed up in March 1941 with the Hooker supercharger and the single speed drive.


The US fuel capacity was a bit of a puzzle, yes the planes would hold much more fuel than the European planes would but they were not intended to fight with that amount of fuel onboard. The Performance figures were always take at a much lower fuel weight. The extra fuel was usually listed as overload or for ferry flights. Filling the tanks would overload the airplane and they were supposed to operated with flight restrictions as to allowable maneuvers.

Allison engine development and planning at this time is complicated by the P-38. The crash of the prototype set the program back by around 6 months. The Early turbo Allison's were supposed to be good for 1150hp at 25,000ft which puts them way ahead of the Merlin and DB601 engines. However as we know from the P-3X saga fitting the turbo Allison into a single engine fighter was not as easy at seemed.
The next problem was that Allison was not responsible for the turbo, GE was and the Army was buying the the turbo's from GE, The Army was also buying the turbo controllers from somebody else. Allison was being told to develop an engine that would deliver XXX power with YYY amount of air being delivered to the carb at ZZZ pressure and temperature.
Lockheed was responsible for the intercooler. Way too many cooks stirring the soup. Quite possible that Allison did not have the number of engineers to handle all the responsibilities but the Army was acting as it's own general contractor. The Army believed that turbos were the way to go and only small amounts of money were going to improved single stage superchargers.


The guns and ammo in the P-40E and the P-39s was way, way heavier than anybody else was trying to stick in single engine fighters in 1940/41 except possibly for the Hurricane MK IIC.

US 1940 100 octane fuel was not the same as British 1940 100 octane fuel so the US planes were a bit behind there. Not the difference that there was between British 87 octane fuel and British 100 octane but somewhere in-between. Trying to run a Summer of 1940 Allison with US 100 octane fuel at 54in pressure was probably not going to end well.

Edit. going to catch flak for the last but British 100 octane in the dessert in 1941 was not the 100 octane fuel the British were using during the BoB and certainly not the 100 octane the Americans were using in 1940. The Fuel the British were using in the BoB was 100/115-120. The American fuel was 100/??? 98/99 to 102??? Some (not much) under test actually measured under 100 at full rich. The US came up with a 100/125 specification and the British joined in briefly (?) and then went to 100/130 and the US joined in on that and by the end of 1942 they were on the 3rd specification for 100/130 with what was actually allowable for production. Now what was actually in the fuel tanks where in world is a whole other question. The max allowable lead for instance for 100/130 fuel changed 3 times from the 1st specification to the 3rd.
IN 1940 there was no way to measure the rich mixture of the fuel. They had to come up with a rating scale and test procedure to able to apply it to all fuel purchased/produced.
They got that in 1941, and the fuel refiners could blend fuels to give the desired results.

 

[GregP]

I'll say the U.S.A. was not on a war footing from 1929, when the stock market crash and started the Great Depression. The Allison V-1710 was a 1929 design that was originally funded as an airship engine, and was then of some interest to the Air Corps. Development was glacial. So, we built fighters and then acquired a few, but really didn't test them in any operational manner at war or with the prospect of going to war very soon.

That usually results in less than stellar development when it comes to military hardware, and it certainly did in this case. When we were at war, development started catching up rapidly.

 

[Shortround6]

The Allison did not really start out as an airship engine. It started as a general purpose engine and while the army was interested they had no money.
The Navy did and the army suggested that Allison look to the navy. The Navy was not really interested in a supercharged engine for airships but ordered 2 (?) the superchargers came later.
Army spent a lot of money (for the times) on the X-1430 project

See. Continental Hyper Cylinder and the O-1430 Aircraft Engine

and let's remember that the Army in the beginning of 1939 owed Allison 900,000 dollars for research and development already done and for which they never were paid.
Allison had to 'forgive' debt in order get permission to export the engine to France and England.

Continental didn't do anything until the Army paid and the Army didn't pay unless certain conditions were met. If an test engine broke during test the Army didn't pay until it was fixed and completed the contacted for test.

Now squeeze Lycoming into the mix

Lycoming O-1230 Flat-12 Aircraft Engine

In 1932, Lycoming began developing a high-performance engine to meet the Army Air Corps’ needs. The engine became the O-1230, but it was outclassed by the time it was ready for production.

oldmachinepress.com

Lycoming spent about 500,000 of their own money and got some from the Army late in the project.

and as has been said, P&W and Wright were more interested in the commercial market as they could not stay in business with government contracts. P&W built a bunch of R-1535 radials, almost all for the Navy, and P&W finally discontinued development due to the lack of commercial sales and the fact that the older R-1830 had been upgraded and was more suited to larger, more modern aircraft.

 

[Frog]

Just my $0.02, the inferior performance of the U.S Pursuit fighter had also something related to the USAAC fighter doctrine that seemed satisfied with single engines, small range, low altitude fighters.
Lockheed tried to circumvent this by offering the XP-38 as an interceptor.

 

[tomo pauk]

Just my $0.02, the inferior performance of the U.S Pursuit fighter had also something related to the USAAC fighter doctrine that seemed satisfied with single engines, small range, low altitude fighters.
Lockheed tried to circumvent this by offering the XP-38 as an interceptor.

We can take a look on the P-30, that was powered by a turbocharged engine already in early 1930s. The P-43 was also a high-altitude fighter. The stillborn XP-37 was trying to offer the same (= competitive high-altitude performance), so was the XP-39.
XP-39 was with 200 US gals of fuel, the P-39C was down to 170 US gals - both values were inconceivable in Europe with 1000+ HP fighters carrying ~100 US gals.

The P-40 was much better fighter for high altitudes than either the P-35 or P-36, and on par with better European fighters in 1940. That USAAC settled with Curtiss P-40 and Bell P-39 had a lot to do with the fact that respective companies failed in developing the workable 1-engined fighters with turbocharged engine (so the P-40 and P-39 emerged into existence as they were), rather than to these fighters being the answer to the USAAC prayers.

 

[GregP]

The Allison did not really start out as an airship engine. It started as a general purpose engine and while the army was interested they had no money.
The Navy did and the army suggested that Allison look to the navy. The Navy was not really interested in a supercharged engine for airships but ordered 2 (?) the superchargers came later.
Army spent a lot of money (for the times) on the X-1430 project

See. Continental Hyper Cylinder and the O-1430 Aircraft Engine

and let's remember that the Army in the beginning of 1939 owed Allison 900,000 dollars for research and development already done and for which they never were paid.
Allison had to 'forgive' debt in order get permission to export the engine to France and England.

Continental didn't do anything until the Army paid and the Army didn't pay unless certain conditions were met. If an test engine broke during test the Army didn't pay until it was fixed and completed the contacted for test.

Now squeeze Lycoming into the mix

Lycoming O-1230 Flat-12 Aircraft Engine

In 1932, Lycoming began developing a high-performance engine to meet the Army Air Corps’ needs. The engine became the O-1230, but it was outclassed by the time it was ready for production.

oldmachinepress.com

Lycoming spent about 500,000 of their own money and got some from the Army late in the project.

and as has been said, P&W and Wright were more interested in the commercial market as they could not stay in business with government contracts. P&W built a bunch of R-1535 radials, almost all for the Navy, and P&W finally discontinued development due to the lack of commercial sales and the fact that the older R-1830 had been upgraded and was more suited to larger, more modern aircraft.

The Allison V-1710 DID start out as an airship engine according to original Allison papers in Joe Yancey's possession. Design started in 1929. Yes, it started out as a non-supercharged engine, but rapidly evolved into a potential aviation engine and a supercharger wasn't long in being developed. Allison was smart enough to develop the components strong enough to accept power increases, and the basic design except for the nose case, was good for a lot more power than originally intended. They looked at both left and right-turn engines and developed it so it was easy to make either engine, left or right turn, if you started with parts. There are a lot of outstanding features in the Allison V-1710.

The F-series nose case solved the limited power delivery level of the original long nose case, and the basic design was carried over to the G-series.

But it DID start out as an airship engine design.

 

[Deleted member 68059]

There was a wide consensus in U.S. military circles ~1939-1940 that U.S. pursuit fighters were substantially less capable in terms of performance than their equivalent European counterparts. Specifically, in Germany, the BF109-E (the first version to use the Daimler-Benz DB-601 engine) began production in 1938, while the original airframe was designed in 1934. In Britain, the Spitfire airframe was designed in 1935 and the airplane went into production in 1938. The single-engined fighters which were being developed in the U.S. at the same time included the Seversky P-35, Bell P-39, and Curtiss P-40 (derived from the P-36). There was wide belief - confirmable by various performance metrics - that the U.S. fighters were inferior.

What accounted for this difference in performance?
Of note: I am looking mostly for an engineering answer, and references would be greatly appreciated!

Advances in in aircraft performance are generally governed by developments in 1) aerodynamics 2) propulsion and/or 3) structures.

Keeping this in mind, the most obvious causal factor in the superior performance of European fighters is that the European engines available for use in the 1935-40 timeframe were of higher performance in terms of P/W ratio (particularly at altitude) than similar engines then available in the U.S. The German DB-601 and British Rolls Royce Merlin engines were both superior to the American Allison engine, the only serious V12 the U.S. produced in the late 1930s. It would take until 1940 for the U.S. radial engine makers to launch high-output versions of their radial engines (e.g. supercharged R-2800s) and of course the U.S. capitalized on the high-performance, liquid-cooled Merlin for use in the P-51.

So the question is, was the entire scope of the performance difference due to powerplants alone or whether there were other salient developments in aircraft aerodynamics and/or structures that help account for the superior performance of British and German fighters to start the war.

I think the best way to do this comparison is to compare three specific aircraft c. 1940: 1) The BF-109E 2) The Spitfire Mk1 (or Mk2) 3) The Curtiss P-40 (alternatively, substitute the P-39).

Note - I am being very specific to the timeframe of 1935 - 1940 because later U.S. developments, such as the P-51 Mustang, F6F, etc., largely corrected much of the performance deficit. While one could still argue on the margins about the superiority of one design over the other, there was no longer a consensus amongst the U.S. military officials that their pursuit fighters were inferior.

Note 2 - there is a difference between a design choice & a technical advance. German and British fighters also may have had higher performance on the metrics I mentioned above not because German's had specific ideas that were more advanced than the U.S.'s designers, but also because they were designed to do with different goals in mind. I have tried to equalize by not comparing aircraft designed for obviously different goals (eg, a twin-engined interceptor vs. a single-engined fighter). But there still might be some differences. For example, U.S. fighters might have been heavier (thus reducing climb rates) because the USAAC put more emphasis on armor protection than the RAF did. If that is the answer, happy to hear that too. Just want to know!

I don't really agree with the premise of this at all, I think considering the late entry to the war, the remoteness from Europe geographically, the numerous political reasons to avoid war (or in some cases support THE OTHER GUYS WITH THE EXPENSIVE BLACK OUTFITS), the lack of funding in the early 30`s, the USA did almost unbelievably well to catch up. In fact in certain areas the USA were miles ahead of Britain, specifically pressure carburettor use.

The USA was just let down by a deficit in compressor research. In my view nobody in Europe fielded a better all round single seat piston aircraft than the P-51D right up to the end of the war.

 

[Shortround6]

Just my $0.02, the inferior performance of the U.S Pursuit fighter had also something related to the USAAC fighter doctrine that seemed satisfied with single engines, small range, low altitude fighters.
Lockheed tried to circumvent this by offering the XP-38 as an interceptor.

The P-39, after the prototype, and the P-40, were designed around the highest critical altitude engine/s Allison could provide at the time, using a single speed-single stage engine.
The Army was gambling on a short development time as they figured that the Turbo versions were over two years away from service use.
Please look at the 1939 fighter competition. You will read things that contradict with themselves.

From Joe Baugher's web site.

"At this time, the Army was still thinking in terms of low-altitude, short-range fighters. Among the contenders were the Lockheed XP-38, the Bell XP-39, no less than three planes from Curtiss, the H75R, XP-40, and XP-42, plus two parallel designs from Seversky/Republic--the XP-41 (AP-2) and XP-43 (AP-4). "

However.

XP-38, turbo chargers.
XP-39 Turbo charger.
H75R , Sometimes described as having a turbo, other times described as having a two stage mechanical blower, it may have had both at different times. P & W engine.
XP-40, single speed-single stage.
XP-41, two stage mechanical blower, P & W engine
XP-42, single stage single speed blower, P & W engine 1000hp at 14,500ft.
XP-43. turbo supercharger, P & W engine.

Now the YP-43s (13 of them) were ordered in March of 1939, the 12 YP-37s with turbos had been ordered in 1938. They ordered 13 YP-38s in April of 1939 at the same time they were ordering the P-40s.

So he says they thinking of low altitude, short range fighters and then lists 7 fighter where 3 have turbos and 2 have two stage mechanical superchargers and only have two have single stage single speed superchargers. BOTH of these engines have FTH several thousand feet higher than the DB 601 engines used in the 109s of 1938-39 and early 1940. They have FTH higher than the Hispano engines going into the French fighters of 1939 (French were planning on going higher and did go up a bit in 1940).
Sorry, not seeing the low altitude American fighters here. Tomo has already addressed the "short range'. That claim doesn't hold up either as Tomo has pointed out.

The P-40s were ordered because the Army needed something, anything, to equip the US fighter/pursuit squadrons with and they could not wait to get the aircraft they really wanted (the ones with turbos).

 

[pbehn]

The question is framed to suit a particular answer. The USA did not have an immediate threat of war so started later in the game of rearmament. The P-38 first flew in Jan 1939 and was introduced in 1941 with an Allison engine and Turbo. The Mustang MkI first flew in Oct 1940, the Alisson engined Mustangs were the mount of choice for the RAF in tactical recon. The P-43 Lancer first flew in March 1940 and led to the P-47.

The war in Europe after the fall of France was across a stretch of water which favours higher altitude performance, same with Malta, the bombers are the battlefront and things stack up above them. In N Africa, the Eastern front and Europe after landings in Italy and France there was a battle front on the ground so fighting in the air stacks up from that. The P-40 performed well in N Africa and the P-39 performed well in the East there was lots of fighting at low to medium altitude. In 1940 no European country had a bomber anything near to the performance of the B-17.

 

[Shortround6]

In 1940 no European country had a bomber anything near to the performance of the B-17.

IN 1940 the US barely had a bomber anywhere near the performance of the B-17
Only somewhat joking, It took Boeing from July 29, 1939 to March 30, 1940 to deliver39 B-17Bs. It took until Nov 29th 1940 to complete the next 38 aircraft. 20 were sent to Britain, the rest were sent back to the factory to be upgraded to B-17D specs.

The US was looking ahead, way ahead, They had asked for the B-24, B-25 and B-26 to be developed in the Spring of 1939.
But the state of the art in 1939 even looking ahead with crystal ball did not look good for long range escort fighters.
The US starting taking delivery of the B-23 in July 1939. It had crap for defensive guns (few people had any better although the British were working on it) but it could max out at over 280mph, cruise at 210mph and carry a 4000lb load for 1400 miles which, IMO, put the escort fighter in prespective in 1939. Give the bomber a 200 mile reserve or 300miles.
You need to fly 550 miles, fight for a few minutes, and return 550 miles and have a reserve and forget the B-17, do it at the Altitude the B-23 can fly at.
Now you have to do it using the engines that available in 1939 or you expect to be available in 1940 or early 1941.
Again for perspective, the first 24/25 B-25s did not have power turrets (indeed did not more than one .50 cal gun and two .30s) and did not have self sealing tanks but did have a range of 2000 miles with a 3000lb bomb load. The next 40 or so had self sealing tanks, a bit of armor and the smaller fuel tanks cut the range to about 1300 miles.
Design you escort fighters to escort these B-25s.
Can you do it?
The P-40 can't
The Spitfire can't
The 109 can't.
So why are we criticizing the P-40 or P-39 for not being escort fighters?

 

[Greg Boeser]

IN 1940 the US barely had a bomber anywhere near the performance of the B-17
Only somewhat joking, It took Boeing from July 29, 1939 to March 30, 1940 to deliver39 B-17Bs. It took until Nov 29th 1940 to complete the next 38 aircraft. 20 were sent to Britain, the rest were sent back to the factory to be upgraded to B-17D specs.

The US was looking ahead, way ahead, They had asked for the B-24, B-25 and B-26 to be developed in the Spring of 1939.
But the state of the art in 1939 even looking ahead with crystal ball did not look good for long range escort fighters.
The US starting taking delivery of the B-23 in July 1939. It had crap for defensive guns (few people had any better although the British were working on it) but it could max out at over 280mph, cruise at 210mph and carry a 4000lb load for 1400 miles which, IMO, put the escort fighter in prespective in 1939. Give the bomber a 200 mile reserve or 300miles.
You need to fly 550 miles, fight for a few minutes, and return 550 miles and have a reserve and forget the B-17, do it at the Altitude the B-23 can fly at.
Now you have to do it using the engines that available in 1939 or you expect to be available in 1940 or early 1941.
Again for perspective, the first 24/25 B-25s did not have power turrets (indeed did not more than one .50 cal gun and two .30s) and did not have self sealing tanks but did have a range of 2000 miles with a 3000lb bomb load. The next 40 or so had self sealing tanks, a bit of armor and the smaller fuel tanks cut the range to about 1300 miles.
Design you escort fighters to escort these B-25s.
Can you do it?
The P-40 can't
The Spitfire can't
The 109 can't.
So why are we criticizing the P-40 or P-39 for not being escort fighters?

And yet, P-39s and P-40s were pressed into flying escort both in the South Pacific, and North Africa, both for medium bombers and lights. The P-38s got the job for the heavies.

 

[Thumpalumpacus]

I don't really agree with the premise of this at all, I think considering the late entry to the war, the remoteness from Europe geographically, the numerous political reasons to avoid war (or in some cases support THE OTHER GUYS WITH THE EXPENSIVE BLACK OUTFITS), the lack of funding in the early 30`s, the USA did almost unbelievably well to catch up. In fact in certain areas the USA were miles ahead of Britain, specifically pressure carburettor use.

The USA was just let down by a deficit in compressor research. In my view nobody in Europe fielded a better all round single seat piston aircraft than the P-51D right up to the end of the war.

I think geography had a big part to play, both in "hey, we've got an ocean either side of us a fighter can't cross" and "hey, we've got this Nazi bastard right close building a big air force, coming at us."

We Americans had the luxury of not being under direct threat, and also labored under the vast distances to cover simply our own spaces. So we could accept our fighters having lesser performance in exchange for longer range if it came down to that, is my thinking.

 

[SaparotRob]

I don't remember where I read this anecdote, probably here, that American aircraft had to at least make it from one end of Texas to the other.
It's a big country. I doubt there was a requirement written as such but thought along those lines must have been there. That might explain why American fighters were larger than their European counterparts.