p 40

No question the P-40 was long in the tooth by mid-1943. But, in lower-priority theaters, such as the CBI and some of the Pacific, and maybe North Africa, it was used because they were sending the "best" to fight in Europe. No question the US strategy was to win in Europe first, fight holding actions other places, and then transfer the assets to the formerly low-priority theaters to prosecute the war as required.

That means the P-40 was used extensively around the world. Any P-40Qs that could have been built would have been game changers for former P-40E, F, etc, pilots.

I don't think the P-40, Q or otherwise, was ever going to be measured against jets during the war. We definitely WERE developing jets during the war, but we never deployed any during WWII except for four P-80s. Two were sent to England and two to Italy, none of which saw any action. All the rest stayed in the U.S.A. .

The British deployed their jets only at home and they never saw much action apart from over the UK either, and never against German jets. Jets were surely going to be the path forward, but WWII was soundly fought with piston aircraft except for Germany, and the German jets didn't have much effect because of small numbers. Factories produced 1,443 Me 262, but only about 300 ever saw any action, and never more than about 50 - 60 at any one time according to Adolf Galland and, if anyone should have known, it would have been him.

GregP said:

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The British deployed their jets only at home and they never saw much action apart from over the UK either, and never against German jets. Jets were surely going to be the path forward, but WWII was soundly fought with piston aircraft except for Germany, and the German jets didn't have much effect because of small numbers. Factories produced 1,443 Me 262, but only about 300 ever saw any action, and never more than about 50 - 60 at any one time according to Adolf Galland and, if anyone should have known, it would have been him.

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I agree that Galland should have known and probably he did but any way decided to promote "his" JV 44 and totally forgot to mention much more important JG 7, max number of Me 262s in service with combat units was on 9 April 1945 about 200, 76 with Stab, I. & III./JG 7, JV 44 about 50, KG(J) 54 (ex-bomber pilots flying fighters) 37, 10./NJG 11 (night fighters) about 9, I. & II./KG 51 21 fighter-bombers and NAGr 6 7 recce Me 262s.

I seriously doubt 200. Only about 300 ever saw combat, and they were not exactly long-lasting airplanes ... rather long-lasting engines. The engines were worn out after only as few as 8 - 12 hours, so there was large turnover of Me 262 flight-ready airframes. With only about 300 seeing combat, the total flight-ready Me 262 airframes would be lucky to launch 25 airplanes at any one time. That comes from decades of reading about WWII aviation, not from a single source.

Of the approximately 300 that saw combat, there were never more than about 200 operational at any one time, and never more than about 40 - 50 ready for flight at the same time. About 1/3 were in maintenance, about 1/3 ready for maintenance, and about 1/3 ready for missions. That balance holds true even today in large part. If not, why do we have so many jet mechanics serving in the armed forces? Me 262s collectively destroyed between 300 and 450 Allied aircraft and lost about 100 Me 262s in the air. They were the future but, during WWII, were not much of a threat. Their portent for the future of aerial warfare was much more significant than their actual combat success during the war was.

That does not detract from the threat of encountering one while in fight, but their very small numbers meant that not many were ever encountered. Most Allied airmen never saw one and, if they did, it was most likely not attacking them. If an Me 262 made a pass at an Allied bomber formation, he most likely was shooting at one bomber per pass. He didn't have many passes before fuel or an engine issue or a horde of escorts were upon him. Let's say they got 450 Allied planes and lost 100. So, for every 4.5 victories they lost one. Not a great record. Not bad, but not great. I'll grant that with the armament installed in the Me 262, if an Allied plane got hit, it was likely in serious in trouble.

During WWII, the UK lost 42,010 aircraft in the air in Europe. The U.S.A lost about 25,000 in Europe. France lost 413 in the air. That means the Germans shot down about 67,423 aircraft in Europe during WWII. So, the Me 262 shot down anywhere from 0.44% and 0.67% of all German air victories in Europe. Of all the threats that an Allied airplane could be downed by, jets accounted for less than 1% of them. While jets would be the main threat going forward in time after WWII, they were hardly worth mentioning during WWII as general threat. If one was attacking YOU, that gave little comfort, but the overall odds of being attacked by a jet during WWII were extremely small. You were much more likely to suffer an engine failure than be attacked by an Me 262.

Not sure how this relates to the P-40 ... oh yeah, it doesn't!

Of course you can doubt the number, but it is based on LW strength info. And max number of Me 262 fighters taking off to intercept an USAAF raid was 76, that was on 10 April 1945, their targets were USAAF bombers and their escorts attacking German a/fs around Berlin. Good sources on Me 262 are e.g. Ethell & Price World War II Fighting Jets, Boehme, JG 7 and on KG(J) 54 Radtke, Kampfgeschwader 54, the latter probably only in German.
What is your source to the claim that "Only about 300 ever saw combat", hopefully not only Galland.

GregP said:

Any P-40Qs that could have been built would have been game changers for former P-40E, F, etc, pilots.

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See, this is the problem I have with the P-40Q. Less than a month after the prototype with the cut-down rear fuselage and impressive speed flew, this entered squadron service with the RAF:

Spitfire static-8

The Spitfire XIV could outperform the P-40Q in every respect, with the possible exception of range. The much-quoted maximum speed of the P-40Q that is mentioned in all the books and articles to emphasise how great it was: 422 mph? The Spit XIV could go nearly 25 mph faster at a higher altitude, and that's a production variant, not a prototype. The next thing I forsee is that The P-40Q was completed in prototype form only and it was a structural redesign on the basic P-40 airframe; it wasn't simply a standard P-40 with a new engine, unlike the Spitfire XIV, which on the production line was a Mk.VIII fitted with a Griffon. This meant that getting it into production would not be as simple as using existing jigs; all that has to be designed and what have you, which took time and would probably require establishing an entirely new production line, since Curtiss had its hand's full building P-40s in 1943/'44. So give or take a few months, the soonest you could expect to see a production P-40Q appear in service, the USAAF has this waiting in the wings...

El Aeroparque 14

It's superfluous before it gets put into production. If Curtiss wanted this as its replacement for the standard P-40 it needs to have acted in 1941 at the earliest for it to match its contemporaries. It's worth noting that Curtiss' attempts at replacing the P-40 from its own designers fell flat and did not get production orders, so had the 'Q come along earlier, it might have been something great, but it didn't.

nuuumannn said:

The Spitfire XIV could outperform the P-40Q in every respect, with the possible exception of range. The much-quoted maximum speed of the P-40Q that is mentioned in all the books and articles to emphasise how great it was: 422 mph? The Spit XIV could go nearly 25 mph faster at a higher altitude, and that's a production variant, not a prototype.

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The test report for the XP-40Q-2: link
(thank you, Mike)
Yes, Spitfire XIV was certainly an over-performer.

nuuumannn said:

The next thing I forsee is that The P-40Q was completed in prototype form only and it was a structural redesign on the basic P-40 airframe; it wasn't simply a standard P-40 with a new engine, unlike the Spitfire XIV, which on the production line was a Mk.VIII fitted with a Griffon. This meant that getting it into production would not be as simple as using existing jigs; all that has to be designed and what have you, which took time and would probably require establishing an entirely new production line, since Curtiss had its hand's full building P-40s in 1943/'44. So give or take a few months, the soonest you could expect to see a production P-40Q appear in service, the USAAF has this waiting in the wings...

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XP-40Q prototypes were re-engined P-40Ks, the -2 was 3rd such prototype.
Granted, not making a decision to have a P-40 outfitted with a 2-stage V-1710 until well into 1943 for trial purposes made the XP-40Q into series production as too late. 2-stage V-1710 will need to be installed on P-40 by late 1942 (concurent with XP-63) in order for such powered P-40s to be in production by Summer of 1943; we'd get around 400+ mph with early 2-stage V-1710s, certainly not 420+.
OTOH - having Curtiss sorting out the P-47G production would've yielded even better boon for the Allies.

tomo pauk said:

XP-40Q prototypes were re-engined P-40Ks, the -2 was 3rd such prototype.

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Thanks for the info Tomo, yup, this I know, but structurally, they were not a 'modified P-40K'. The last one had its rear fuselage cut down, work done on the cooling system and wings as a result, structural work done on the engine mounts, and so on. It was not a P-40K-with-a-new-engine, unlike the Spitfire XIV which was a Spitfire VIII-with-a-new-engine.

The point still remains. By the time it enters production and service, any perceived advantages it might have had in prototype form have been overtaken.

nuuumannn said:

Thanks for the info Tomo, yup, this I know, but structurally, they were not a 'modified P-40K'. The last one had its rear fuselage cut down, work done on the cooling system and wings as a result, structural work done on the engine mounts, and so on. It was not a P-40K-with-a-new-engine, unlike the Spitfire XIV which was a Spitfire VIII-with-a-new-engine.

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We know that there was a series of Spitfires with cut-back rear fuselage; changes to cooling system were done on Spitfire Is that became SPitfire Vs, then when Spitfire Vs became Spitfire XIIs or IXs. Engine mounts for Griffon were a wee bit different than those for Merlin III or 45.
XP-40Qs (all 3 of them) started their life as P-40Ks.

nuuumannn said:

The point still remains. By the time it enters production and service, any perceived advantages it might have had in prototype form have been overtaken.

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I've made a similar statement already several times before, both in this and other threads.
For a really competitive P-40, it needs to receive a 2-stage supercharged V12 engine already by late 1942 for test purposes, with delivery by Summer of 1943.

tomo pauk said:

We know that there was a series of Spitfires with cut-back rear fuselage; changes to cooling system were done on Spitfire Is that became SPitfire Vs, then when Spitfire Vs became Spitfire XIIs or IXs. Engine mounts for Griffon were a wee bit different than those for Merlin III or 45.
XP-40Qs (all 3 of them) started their life as P-40Ks.

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Thankfully structurally, the changes made to the basic Spitfire airframe were minimal. In every Spitfire from the Mk.II airframe to the Mk.22 and 24 had the same structural centre fuselage, from Frame 5, which was the firewall, to Frame 19, which was where the tail section bolted on. Griffon Spits had the engine moved forward a bit and had the firewall canted forward to accommodate a bigger oil tank, but the fuselage was the same.

Fuselage

The P-40Q was not simply a 'modified P-40K'. It was built from a P-40K airframe, but incorporated structural changes and it was hand-built. A redesign on the drawing board would have been necessary if it got as far as being put into production. Look at the differences between it and a standard P-40 in a line drawing. It looks very different. The wing has to be redesigned since it's shorter. You can't just lob a section of outer wing off on a production line! You have to redesign the internal structure to incorporate necessary changes otherwise you'll compromise its integral strength! That's not even mentioning the re-ducting required for the cooling and air intake system. There isn't some magic hole that pipes and stuff can be re-routed inside an aeroplane. The leading edge wing root has to be redesigned, as does the fuselage around the firewall, which again has to be redesigned to accommodate the ducting. The P-40's wing was built in two halves, on which the seat was put, then the fuselage was placed on top of that. since big modifications to the wing root leading edge have to be made, the wing simply cannot be the same with a few cutouts in it. You'll reduce the structural integrity of it where its supposed to be at its strongest, where the fuselage attaches, and cause structural failure, which'll not be so good for your new fighter.

The rear fuselage is not even the same shape. The Spitfire's construction meant the top deck could be removed and refitted with little redesign. The P-40's could not. you have to cut the tops of the frames off, recontour them then reshape the outer skin. The nose cowls are not the same, the spinner is completely different. By the time redesign and testing has ended, I bet that the basic P-40 empennage would have changed as well. You're looking at an entirely new airframe.

it's a bit like saying that the Beaufighter was designed from the Beaufort - they had virtually nothing in common, except the maker's name. This is not something that can be done on a production line without considerable redesign of the aircraft structure.

tomo pauk said:

or a really competitive P-40, it needs to receive a 2-stage supercharged engine already by late 1942 for test purposes, with delivery by Summer of 1943.

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Do you honestly think that a P-40 with a two-speed two-stage supercharger is going to be competitive in 1945 when the P-40Q enters service? Nah, neither do I. Which is precisely why I said at the bottom a few posts back that work has to begin in 1941 at the earliest.

Allison actually started work in 1938, from "Vee's for Victory" page 345

"With the developing interest in removing the turbosupercharger from the XP-37, XP-39 and XFM-1 in 1938/39 it was clear to all involved (the Air Corp, Bell Aircraft, Curtiss-Wright and Allison) that an airplane with a two stage supercharger was still going to be needed. In November of 1938, Allison began efforts to develop such a unit, though they chose a fairly unique approach, that being a separate Auxiliary Stage supercharger that could be attached to the production engine with little modification or revision."

Allison started with a simple friction clutch and didn't change to the hydraulic clutch/variable drive until 1942.
They also tried to use a standard 9.5 in impeller in a housing with bigger passages to try to get the air flow needed.

Allison didn't get the order for the P-40 engines until April of 1939.
only 22 engines had been ordered in 1937 and 43 engines in 1938.
Allison had a lot more pressing needs in in 1939/40/41 than working on the two stage supercharger system.

nuuumannn said:

The P-40Q was not simply a 'modified P-40K'. It was built from a P-40K airframe, but incorporated structural changes and it was hand-built. A redesign on the drawing board would have been necessary if it got as far as being put into production. Look at the differences between it and a standard P-40 in a line drawing. It looks very different. The wing has to be redesigned since it's shorter. You can't just lob a section of outer wing off on a production line!

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Wing tip was removed. That tends to shorten the wing.

nuuumannn said:

You have to redesign the internal structure to incorporate necessary changes otherwise you'll compromise its integral strength! That's not even mentioning the re-ducting required for the cooling and air intake system. There isn't some magic hole that pipes and stuff can be re-routed inside an aeroplane. The leading edge wing root has to be redesigned, as does the fuselage around the firewall, which again has to be redesigned to accommodate the ducting.

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Seems like people at Supermarine have had magic holes to help out once the intercoolers were added to Spitfire, also bigger holes for greater needs of cooling with 2000 HP engines vs. 1030-1300 HP ones. They never needed any airframe strengthening when much heavier engines, guns etc were installed due to the laws of physics not applying to them. Relocating the oil tank, installation of intercooler liquid tank - can be done on Spitfire on a whim, but woe beholds the P-40 if it is to receive a 2-stage engine without an intercooler.

nuuumannn said:

The rear fuselage is not even the same shape. The Spitfire's construction meant the top deck could be removed and refitted with little redesign. The P-40's could not. you have to cut the tops of the frames off, recontour them then reshape the outer skin. The nose cowls are not the same, the spinner is completely different. By the time redesign and testing has ended, I bet that the basic P-40 empennage would have changed as well. You're looking at an entirely new airframe.

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Yes, let's assume whatever it takes.
P-40Q was not defined by the cut-back fuselage, but by installation of a 2-stage supercharged engine.

nuuumannn said:

Do you honestly think that a P-40 with a two-speed two-stage supercharger is going to be competitive in 1945 when the P-40Q enters service? Nah, neither do I. Which is precisely why I said at the bottom a few posts back that work has to begin in 1941 at the earliest.

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1943 is not 1945.
Allison was not making 2-speed 2-stage engines beyond couple of prototypes. The 2-stage supercharged V-1710s have had the 1st stage driven by hydraulic coupling, meaning that that stage have had variable speed drive.

tomo pauk said:

P-40Q was not defined by the cut-back fuselage, but by installation of a 2-stage supercharged engine.

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You're right (although the cut-down fuselage aided aerodynamics), but I'd imagine the changes in fuselage design would require some retooling/rejigging to the factory line, which would slow the conversion process. I think that's the point he's making.

Thumpalumpacus said:

You're right, but I'd imagine the changes in fuselage design would require some retooling/rejigging to the factory line, which would slow the conversion process. I think that's the point he's making.

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Change from 'razorback' to 'cut back' can wait. Installation of much better engine cannot. Same as when Spitfire I became Spitfire V, or Spit V -> IX, or Spit V -> XII, or with many Bf 109 marks.
BTW - the 1st P-40 with cut-back fuselage and bubble top was one-off P-40N.
I've commented on nuuumannn's points above in the thread, my counter-points still stand.

tomo pauk said:

Change from 'razorback' to 'cut back' can wait. Installation of much better engine cannot.

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I agree, the engine-swap means more in this context. However, cutting a couple of hundred pounds of fuselage weight probably made that same engine-swap more potent.

How would an alternative P-40Q with the same airframe as earlier models benefit solely from the engine upgrade? Put another way, do you know how much the airframe change contributed to increased performance? Would it have been worth retooling/rejigging? It's an interesting question to me but I lack the insight to tot up the scales on it.

Thumpalumpacus said:

I agree, the engine-swap means more in this context. However, cutting a couple of hundred pounds of fuselage weight probably made that same engine-swap more potent.

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I don't think that the weight savings were more than a few dozen of lbs, if even so. Fuselage of P-40 was between 420 and 450 lbs for the later models (E to N). This is firewall and aft, but without outfitting (tanks, radios, cockpit equipment, radios etc)
Gain from the cut-back fuselage was that enabled a far better cockpit canopy.

Thumpalumpacus said:

How would an alternative P-40Q with the same airframe as earlier models benefit solely from the engine upgrade? Put another way, do you know how much the airframe change contributed to increased performance? Would it have been worth retooling/rejigging? It's an interesting question to me but I lack the insight to tot up the scales on it.

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Radiators were certainly best on the P-40Q-2 (earlier Qs have had ... iffy radiators). This on itself was probably worth 10 mph vs. for example P-40N. Clipped wingtips - another 5 mph, if even so? The rate of roll would be improved a bit with clipped wings, although P-40 was already rolling at excellent rate.
I'll also note that Q-2 was outfitted with best ww2-vintage 2-stage V-1710, featuring the carburetor between the compressor stages and with faster-turning 1st impeller. Water/alcohol was also used, that was in use by winter of 1943/44 - allowed for boost of up to 75in Hg vs. ~60 in Hg without it at low and mid altitudes; more boost = more power. It was also capable for 3200 rpm operation. Net result was the rated altitude for ~1100 HP power at ~27000 ft, vs. at 22500 ft for the 1st generation and 25000 ft for the 2nd generation.
All in all, we'd probably get a P-40 making close to 400 mph just due to the engine swap (with 1st gen of engine, mid-1943 production) and then slowly improve up to 420 mph (mid-1944 production) as Allison improves their engine, radiators get better and water/alc injection is used.

tomo pauk said:

I don't think that the weight savings were more than a few dozen of lbs, if even so. Fuselage of P-40 was between 420 and 450 lbs for the later models (E to N). This is firewall and aft, but without outfitting (tanks, radios, cockpit equipment, radios etc)
Gain from the cut-back fuselage was that enabled a far better cockpit canopy.



Radiators were certainly best on the P-40Q-2 (earlier Qs have had ... iffy radiators). This on itself was probably worth 10 mph vs. for example P-40N. Clipped wingtips - another 5 mph, if even so? The rate of roll would be improved a bit with clipped wings, although P-40 was already rolling at excellent rate.
I'll also note that Q-2 was outfitted with best ww2-vintage 2-stage V-1710, featuring the carburetor between the compressor stages and with faster-turning 1st impeller. Water/alcohol was also used, that was in use by winter of 1943/44 - allowed for boost of up to 75in Hg vs. ~60 in Hg without it at low and mid altitudes; more boost = more power. It was also capable for 3200 rpm operation. Net result was the rated altitude for ~1100 HP power at ~27000 ft, vs. at 22500 ft for the 1st generation and 25000 ft for the 2nd generation.
All in all, we'd probably get a P-40 making close to 400 mph just due to the engine swap (with 1st gen of engine, mid-1943 production) and then slowly improve up to 420 mph (mid-1944 production) as Allison improves their engine, radiators get better and water/alc injection is used.

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I sure appreciate your detailed reply. Had the submodel been started earlier, it looks like it could have been very useful. First flying in 1944, with equally-good planes already in the air, and better ones in pre-production, I'm not sure producing the -Q would have been smart money.

Thumpalumpacus said:

I sure appreciate your detailed reply. Had the submodel been started earlier, it looks like it could have been very useful. First flying in 1944, with equally-good planes already in the air, and better ones in pre-production, I'm not sure producing the -Q would have been smart money.

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A P-40 with a 2-stage V-1710 beats the P-63 in usability.
A lot of allied pilots were flying in fighters making 330-380 mph in 1944, both in Europe and Asia/pacific, while another good deal was flying in the ones doing 380-400 mph - a 400-420 mph P-40 would've been a welcome improvement.

tomo pauk said:

A P-40 with a 2-stage V-1710 beats the P-63 in usability.
A lot of allied pilots were flying in fighters making 330-380 mph in 1944, both in Europe and Asia/pacific, while another good deal was flying in the ones doing 380-400 mph - a 420 mph P-40 would've been a welcome improvement.

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Again, the point is that changes to a production line that was already full of orders for a plane that only matched rather than improved upon current performance (compared to the P-47 or -51) doesn't seem like smart money, when jets are already on the horizon. You're slowing down production of standard P-40s that are already very useful, while only matching the performance of the front-line planes. And all the while, jets are right over the horizon.

The P-40Q could have been a great fighter, but it really was a year or so late, in a first-come, first-serve time.

Not sure how much a -Q could have helped the PTO. Would probably be useful in CBI, though.