SHOULD the P39 have been able to handle the Zero? Was it training or performance?

[Peter Gunn]

Out of the first 3 P-47 tests on WWII Aircraft Performance 2 have 6 guns installed, ammo and fuel state not given, 3rd has a very similar weight (down 5lbs) but 8 guns.

*SNIP*

Not to go off topic but wasn't there a bit of experimentation in the 4th FG when they first got Thunderbolts were they removed two of the .50's?

Thanks.

 

[Peter Gunn]

"*SNIP*
they went in a flat spin and so they were screwed so a very good Genoese Pilot, Moresi left his skin, another Sergeant left his skin, even though they were saying, ehhhh, do you know what I say, if you loop, do it fast,
*SNIP*"

I'm pretty sure I know what that means but just for clarification ( for my small brain ), I assume they were killed?

 

[Elmas]

I'm pretty sure I know what that means but just for clarification ( for my small brain ), I assume they were killed?

 

[MIflyer]

"Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86."

I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."

From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger. Given that the V-1710 was built in an automotive fashion, with engine block, gearcase, and accessory section as separate section it would have far easier than with the one-piece Merlin engine case and need not interrupt production. If required they could have gotten Continental or Maytag Washing Machines or some other company to build the new 2 speed section. Going the next step to a two stage two speed supercharger would have been more challenging, but well within their capabilities. As it was, Packard redesigned the Merlin supercharger for easier production and had Wright redesign the impeller.

So that taxpayer paid feather merchant decided the Allison was not worth his time and an real opportunity, low hanging fruit, was missed.

A book I read recently on the Bell X-1 program showed that NACA did its level best to sabotage the program. Finally the USAAF said "ta hell with this," put Chuck Yeager in the cockpit and started going somewhere.

 

[Shortround6]

The P-39 may not have been a bad aircraft but it was not a great one either. It was also a victim of it's size (which contributed to it's performance) and to timing.
The timing covers a range of things. It covers Allison's slow (but understandable) development of superchargers, The Army's slow (and less understandable) approval of combat power settings. It also covers the rapid improvements to other fighters the US was purchasing at the time.
The gestation period of aircraft has been brought up already in this thread. By the time you get to the P-39N with 9.60 gears and an approved WEP power rating Bell was already working on what would become the P-63 King Cobra, this had a long and tortured history that dated back to at least April 10th 1941 with the order of two P-39Es which had very little in common with any other P-39, new wing, long fuselage, new engine, etc.
The Army had also bet heavily on the P-47 with 3 factories either making them or tooling up for them in the fall/winter of 1942. Several thousand are on order with all the extended ordering of parts from subcontractors that entails.
P-51 production has been extended by the A-36 funding trick and the contract for a large part of the P-51As with Allison's is changed to P-51Bs with Merlins, By Jan of 1943 thousands of Merlin P-51s are on order.
Lockheed is struggling to solve cooling problems with the P-38 as Allison keeps making higher powered engines. I don't know who was promising what when but the P-38 G had 1325hp engines in June of 1942 and the H had 1425hp engines by March of 1943, the only difference between an H and and early J was the intercooler set up and both planes were produced at the same time for short period until intercooler supplies caught up. granted this was in the fall of 1943.

The P-39 was simply too small to allow for a significant increase in fuel and too small to fit a larger, more sophisticated supercharger set up. perhaps, if Allison had the engineering staff, a two speed (not two stage) supercharger with larger impeller could have been squeezed in but that was not what was wanted by the customer (the USAAF), not enough performance increase given the time needed to develop and deploy the modifications, and development work went into the two stage Allison for the P-63 which had the larger fuselage to accommodate it. The P-63 still wound up way short of fuel compared to the other planes.
According to some sources the P-63 was supposed to have an intercooler but the company/s involved failed to deliver and the P-63 resorted to water injection.
I would note that all the radial engine fighters wound up with both water injection and intercoolers.
Any major improvements to the P-39 would probably have meant delays in either the P-63 or P-59 jet programs, and even such improvements as under wing bomb/drop tank points weren't going to really change the capabilities of the US forces in general.

 

[b0ned0me]

I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."

Maybe here? https://history.nasa.gov/SP-4306/ch2.htm

The Cleveland Laboratory's work on the Allison engine increased its horsepower through the use of water injection and supercharging. However, from Ben Pinkel's point of view, this work was a "tremendous waste of effort" because of the basic flaws in the engine's design. Only after the Army substituted the British Merlin engine, in the P-51 Mustang did the United States finally have a fighter for high-altitude flight.

From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger.

Maybe, but a child's play BuAer didn't seem interested in. Can't really blame Allison for not pursuing it on their own dime when their main customer was flogging them bloody demanding they achieve 1001 other things by yesterday.

 

[P-39 Expert]

Ah, the legendary P-39.
From a performance and handling standpoint the P-39 was a tribute to the capabilities of the Bell sales organisation.
Recognizing the desperate need for competitive aircraft, Bell could always be relied upon to miss every performance requirement while citing delivery needs, and to miss every date requirement citing the need to work on performance.
Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86.
The US was stuck between Lockheed's small production of expensive, complex, difficult-to-use but high-performance aircraft and Curtiss' high production of simple, robust but obsolescent under-performers. They needed something cheap, reliable with competitive performance and Bell was able to give them an aircraft that was expensive, complex, difficult to operate and an under-performer.

Frankly, when it comes to the P-39 the jokes just write themselves. Within the constraints of the USAAFs then doctrine of 'turbo or bust' it was a creditable attempt at rethinking how to build a better interceptor but turned out to be badly flawed in execution, and unfortunately had to be pressed into service for lack of anything better. Once the first panic was over the western allies had far better aircraft to choose from so it went to the USSR who were delighted to supplement their own tactical low-altitude fighters built in tractor factories by farmers with a zero-cost tactical low-altitude fighter built in aviation factories to aviation specs.

It certainly did a lot of good work but it also got people killed who would have survived in better aircraft, and once aircraft like the P-51 were available it was frankly not worth a cup of warm piss.

Should it have been able to handle the Zero? Depends on what is meant. With better training and tactics might the allied P-39 pilots have died slowly enough and bled the Japanese more, enough to make a difference? Quite possibly.
If two identically skilled pilots squared off in P-39 v A6M with no tactical advantages, should the P-39 driver be expected to win the majority of the time? I doubt it very much.

No, you prefer your fanboy obsessions over the experience of the people who actually had dealings with these aircraft in WW2 and everyone who has researched them in the decades since WW2. Just like all the Wehraboos who insist the Germans could have won the war if only they built Napkinwaffe jets in 1941 or got Hugo Boss to make them a sharper-looking uniform.

And there is no such word as heresay. You can have heresy or you can have hearsay, but you cannot combine them into one word. However that is another fact I am sure you will continue to ignore.

I did misspell hearsay, wasn't caught by spellcheck.

Why all the venom? Aren't we just discussing airplanes that are now over 70 years old? Am I not entitled to an opinion?

Please allow me to add an alternative view to all your hearsay.

Regarding your first paragraph, how did we start talking about the F-86? Did I somehow say the P-39 would outfly a Korean War jet? You cite what the US needed. They needed fighter planes in production NOW, not turbocharged superplanes that wouldn't see combat until very late 1942 (P-38) or May 1943 (P-47). So they deleted the turbo to get the P-39 (and P-40) into service asap. The P-39 was available from the beginning of WWI, along with the P-40 and F4F.

Second paragraph, when was the first panic over? P-38 didn't get into combat until very late 1942. US fought WWII with only the P-39 and P-40 until very late 1942. Most historians agree that the US would have been hard pressed without the P-39 for our first year in the war.

Third paragraph, got people killed? Was one of the safest fighter planes, tricycle landing gear for safer ground handling, almost every fighter pilot flew one in training. TRAINING. Not worth a cup of warm piss? Chuck Yeager's favorite plane, three of the top 4 Russian aces flew it along with scores of 20 victory aces. Warm piss?

Should it have been able to handle the Zero? All models, even the earliest ones were at least 30mph faster than comparable Zeros at all altitudes. Their pilots were navy pilots with experience in China. Our boys were fresh out of flying school with NO experience except for Buzz Wagner who reportedly actually got off the ground at Pearl Harbor. One mission. They had established bases all along the north coast of NG and at Rabaul. US had just arrived at Port Moresby April 30 with 2 squadrons (about 40 planes). Pretty long odds. But these green kids managed a 1:1 kill ratio and kept them out of Port Moresby. Would you have rather flown a plane with no armor or self sealing fuel tanks, or a fully armored and heavily armed plane that was significantly faster?

Thanks for calling me a fanboy. Name calling. I'm 67 years old and enjoy WWII history. Not a fan, and not a boy. I just believe there is more to the P-39 than we have been led to believe. And I think I can prove it with facts and statistics. Not hearsay and name calling.

 

[Peter Gunn]

I'm pretty sure b0ned0me was making a joke that it would take Bell until 1947 to produce a fighter equal to most late WWII fighters. A pretty glib comment I think.

 

[yulzari]

I just believe there is more to the P-39 than we have been led to believe.

Whatever the engineering and rivet counters statistics may say mission and machine met in Russia where they were excellent tactical fighter escorts for low flying tactical light and medium bombers. The range was short, the fighting took place within the best power outputs at height of the engine, the firepower was adequate (I still have to be convinced of the 37mm) and the nose wheel reduced ground handling accidents. Elsewhere the OTL machine was a mismatch to it's missions but that might be down to the user's specification rather than Bell's engineering. When there was noting better it was used. When there were better things it was sent to the user who had missions that matched it's performances. A bit like the Valentine tank.

 

[Hansie Bloeckmann]

I did misspell hearsay, wasn't caught by spellcheck.

Why all the venom? Aren't we just discussing airplanes that are now over 70 years old? Am I not entitled to an opinion?

Please allow me to add an alternative view to all your hearsay.

Regarding your first paragraph, how did we start talking about the F-86? Did I somehow say the P-39 would outfly a Korean War jet? You cite what the US needed. They needed fighter planes in production NOW, not turbocharged superplanes that wouldn't see combat until very late 1942 (P-38) or May 1943 (P-47). So they deleted the turbo to get the P-39 (and P-40) into service asap. The P-39 was available from the beginning of WWI, along with the P-40 and F4F.

Second paragraph, when was the first panic over? P-38 didn't get into combat until very late 1942. US fought WWII with only the P-39 and P-40 until very late 1942. Most historians agree that the US would have been hard pressed without the P-39 for our first year in the war.

Third paragraph, got people killed? Was one of the safest fighter planes, tricycle landing gear for safer ground handling, almost every fighter pilot flew one in training. TRAINING. Not worth a cup of warm piss? Chuck Yeager's favorite plane, three of the top 4 Russian aces flew it along with scores of 20 victory aces. Warm piss?

Should it have been able to handle the Zero? All models, even the earliest ones were at least 30mph faster than comparable Zeros at all altitudes. Their pilots were navy pilots with experience in China. Our boys were fresh out of flying school with NO experience except for Buzz Wagner who reportedly actually got off the ground at Pearl Harbor. One mission. They had established bases all along the north coast of NG and at Rabaul. US had just arrived at Port Moresby April 30 with 2 squadrons (about 40 planes). Pretty long odds. But these green kids managed a 1:1 kill ratio and kept them out of Port Moresby. Would you have rather flown a plane with no armor or self sealing fuel tanks, or a fully armored and heavily armed plane that was significantly faster?

Thanks for calling me a fanboy. Name calling. I'm 67 years old and enjoy WWII history. Not a fan, and not a boy. I just believe there is more to the P-39 than we have been led to believe. And I think I can prove it with facts and statistics. Not hearsay and name calling.

We are both students of WW2, especially the aircraft and pilots involved. I haven't been a boy for many years, but as a lad, built many model aircraft, both WW1 and WW2 era- American, British, German, Italian- even a few Japanese.
Growing up, the first real scaled models of WW2 and the Korean War that I collected were made by the Topping Co., in Akron, Ohio- true to scale, and made my "attempts" at replicating the real aircraft seem "not quite right"--Hansie

 

[pbehn]

Chuck Yeager's favorite plane..

This is not a "fact" and you have posted it twice. Yaeger was a Bell employee in the post war years, he broke the sound barrier in a Bell X1. He could only possibly favour it as a WW2 aircraft considering the performance of other high performance jets he flew. Basically he preferred the P-39 until he flew the P51 but in WW2 he only flew those two as far as I have read. Did he ever attempt any violent manoeuvres with all ammunition spent, for example?

 

[Schweik]

"Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86."

I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."

From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger. Given that the V-1710 was built in an automotive fashion, with engine block, gearcase, and accessory section as separate section it would have far easier than with the one-piece Merlin engine case and need not interrupt production. If required they could have gotten Continental or Maytag Washing Machines or some other company to build the new 2 speed section. Going the next step to a two stage two speed supercharger would have been more challenging, but well within their capabilities. As it was, Packard redesigned the Merlin supercharger for easier production and had Wright redesign the impeller.

So that taxpayer paid feather merchant decided the Allison was not worth his time and an real opportunity, low hanging fruit, was missed.

A book I read recently on the Bell X-1 program showed that NACA did its level best to sabotage the program. Finally the USAAF said "ta hell with this," put Chuck Yeager in the cockpit and started going somewhere.

That is really incredible if true. If they had put a two stage supercharger on the Allison by say, late 1942 it would have saved so many lives, might have even shortened the war.

 

[Elmas]

Root: NACA 0015, tip: NACA 23009, no washout (2 deg constant incindence).

Geoffrey De Havilland, if I remember well, once said "a beautiful aeroplane always will fly well" but I'm afraid that P-39 probably was the classical exeption that confirms the rule.

In these days, reading the posts of this interesting 3d, I was excavating a little bit more deeply in the Airacobra design, a thing that I never did as after the end of WWII between the American airplane production delivered with MAP two planes were kept as far as possible by Italian Pilots, P-39 and SC2-5 Helldiver ("B" was taken out as, after the Peace treaty, Italy could not have bombers).

Great expectations were placed on the P-39 at his appearance on the stage, not only by the Air Corps but by the whole aeronautical community in the world over: in those times there were still around machines like P-26, not to speak of biplanes, so the appearance of Airacobra was certainly more dazzling than that of, say, F-22 in modern times.

No doubt that many aeronautical designers were looking at this airplane in search of "inspiration".
So I discovered with my great surprise that Re. 2005 and Airacobra had the same profile in the wing design: a NACA 0015 at the root, symmetrical biconvex 15% thick, needed for structural strenght

And a NACA 5 digit 24009 at the tip, with an high Cl

The designer of Re. 2005, Ing. Roberto Longhi, did work in U.S.A. in the '30s at the Republic-Seversky factory before returning to Italy, so the early Reggiane fighters, Re 2000 in particular, have a close resemblance with P-35. He was well aware of the tremendous amount of work made in wind galleries from NACA, while in other countries, Germany excepted, wing profiles were designed "by nose" or, "to be in the safe side" the ubiquitous Clark Y was used.

Ing. Longhi stated in a letter, published by Air Enthusiast Quarterly nr. 2 - 1976: "...I decided to change the wing section from that of the previous Reggiane fighters to one based on the two profiles utilised by the P-39 Airacobra, as these seemed better suited for the altitudes that were now being demanded. All other Reggiane aicrafts use a modified N38."

It has recently come out from a Reggiane designer's papers that the airfoil used for the wing profiles prior to Re. 2005 was not the N38 but the NACA CYH, also known as Clark YH, a classic Clark Y with a reflexed trailing edge.

Airfoil at wing root

Airfoil at wing tip

Re 2000, like all contemporary monoplane aircraft, certainly MC 200 and G.50 among Italians ( I have less information about P-35) suffered from bad stall caracteristics, until a German paper at the end of the 30's explained the importance of a correct wash-out. When a correct wash-out was introduced in the wing of MC 200 the flying caracteristics improved dramatically, and the same wing was retained in Macchi 202 and 205.
Re. 2005 had a wash-out of about -2,2°

So, in Airacobra, the small dimensions, the absence of wash-out in the wings and the inertia coupling, not well understood in those times ( but even it was not well undestood, it had equally his effects...) due to the particular position of the engine and consequent distribution of weights gave to the aeroplane some nasty flying habits, that compelled Pilots to wear "belt and braces" when inside a P-39.
Not the best way to fight with a Zero.

 

[P-39 Expert]

"Given adequate engineering support from NACA, Allison and the AF, Bell could have had an improved P-39 as good as any other late ww2 fighter, in front line service, several months before the F-86."

I wish I could find the reference again, but I recall reading that during WWII an NACA employee was given the job of improving the Allison V-1710 engine and complained "Why should we be bothered with this thing? It's a piece of junk."

From a mechanical engineering standpoint it would have been child's play to add a 2nd speed to the V-1710's single stage supercharger. Given that the V-1710 was built in an automotive fashion, with engine block, gearcase, and accessory section as separate section it would have far easier than with the one-piece Merlin engine case and need not interrupt production. If required they could have gotten Continental or Maytag Washing Machines or some other company to build the new 2 speed section. Going the next step to a two stage two speed supercharger would have been more challenging, but well within their capabilities. As it was, Packard redesigned the Merlin supercharger for easier production and had Wright redesign the impeller.

So that taxpayer paid feather merchant decided the Allison was not worth his time and an real opportunity, low hanging fruit, was missed.

A book I read recently on the Bell X-1 program showed that NACA did its level best to sabotage the program. Finally the USAAF said "ta hell with this," put Chuck Yeager in the cockpit and started going somewhere.

Just my opinion, but what the Allison needed was not a two speed supercharger but a (mechanical, not turbo) two stage supercharger.

We've had the two speed argument here before, and I still maintain that low gear's purpose is just to keep the pilot from overboosting the engine at takeoff and low altitude. The P-39 had plenty of performance at low altitude with their single speed unit regulated by the pilot in early models and the automatic boost control after mid '42. The Allison's single speed was in effect "high" gear, and the need for low gear was eliminated by the autoboost control. The whole two speed vs one speed argument is moot in my opinion.

The two STAGE engine was needed to keep up with the two STAGE Merlin 61 and the two stage R-2800s. The two stage engine provided more power at higher altitudes because the first (or auxiliary stage whether it be mechanical or turbo) stage boosted the thin air at high altitude up to sea level thickness and discharged it into the second (internal) stage which boosted it even further to get those fantastic speeds at high altitude. In effect, the first stage fooled the second stage into thinking it had sea level (high density) air at 25000' boosting power tremendously.

Please remember that the two stage engine was pretty much a British/American product. Americans had turbos and mechanical second stages and the British had only mechanical. The Germans, Japanese and Russians didn't have two stage engines in production planes. They had single stage engines, consequentially their critical altitude was around 18000', whereas two stage engines critical altitude was much higher. The two stage engines came into combat in mid 1942 (Spitfire IX), late 1942 (P-38), mid 1943 (P-47). High speeds for these planes was at 25000'-30000'.

Now there WAS a two stage mechanical Allison, the first production model was the V-1710-93 for the P-63. It featured a separate second stage supercharger driven by a jackshaft from the Allison starter dog that drove through a hydraulic clutch that automatically regulated manifold pressure. The -93 developed 1325HP for takeoff and 1180HP at 21500' with 1825HP war emergency. This pushed the P-63 without wing guns to 422mph at 24000'. They bolted a comparable model onto a P-40 and called it the Q and even that old P-40 went 418mph at 24000' and climbed like a rocket. Only 3 of those Q's were built.

More importantly the -93 was in full production in April 1943 and the P-63 didn't fly until October. Why in the world didn't the Army just put one in the P-39? It fit into the experimental P-39E. The contemporary P-39 model was the P-39N at 7650#. Add the 200# auxiliary stage and balance the weight with a larger 4 blade propeller and you have a real hot rod at 8050#. By July 1943 these P-39s would be coming off the production line and would have rivaled the Spitfire IX and P-51B in speed and climb. But the -93 in a P-39 was not to be, probably because the Army didn't want the Russians to have it. They were the main customer for the P-39 at the time.

 

[Schweik]

That is really incredible if true. If they had put a two stage supercharger on the Allison by say, late 1942 it would have saved so many lives, might have even shortened the war.

Just to clarify, my comment is referring not just to P-39's, but also to P-40's and early Mustangs, all of which could have been vastly improved if their Allison V-1710 had a two stage supercharger. Even after packard merlins became available, production was limited particularly in the early years. If Allison was able to produce engines of near equivalent capability then we could have built thousands more highly capable front-line fighters (like the 6,000 + later model P-40's they made)

Even early P-38's which were having a lot of trouble with their turbochargers and intercoolers, might have benefited by switching engines to the equivalent of a Merlin 66... they would have done much better I think.

 

[MIflyer]

On the very early P-38's they had to change the supercharger gear in the V-1710 to increase the boost from the mechanical supercharger so they could reduce the boost required from the turbo at high altitudes. Early on they had a problem with the turbos coming apart at high boost. Those "fins" on the side of the booms between the cockpit and the turbos were shields to protect the pilot from disintegrating turbochargers.

 

[Ascent]

The impression I'm getting from all this discussion is that the P39 was a day late and a dollar short. For the western allies there was always something more suited for any role that could be found for it and by the time it had improved something else better was in service.

It was on the eastern front where it found its niche, it's drawbacks outweighed by it's advantages.

 

[Shortround6]

It is all very well and good to talk about installing two stage superchargers on P-39s. p-40s and early P-51s...........except...........





they don't fit.

In order to work they need intercoolers. Otherwise the intake mixture gets to too hot and the engine goes into detonation.
This was the trouble the P-38 had from about the 'D' model until the "J". It was the problem the P-63s had.
Finding another 1 ft or less behind the engine for the larger supercharger housing wasn't the problem (until Allison put the 1st stage in a separate housing and drove it with a seperate drive system). it was finding room for the intercoolers and ducting.
Please note that a 2 stage Allison in the P-63A could make 1800hp at sea level using 75in and water injection. WIthout water injection it made about 1500hp at 60in but by the time you got to to 21500ft it was down to 1180hp, whether you used water injection or not.
Please note a Merlin 46 could make 1100hp at 22,000ft with a single stage single speed supercharger and make 1440hp at 14,500ft. No intercooler either.

Everybody wants the performance of the two stage supercharger, nobody wants to pay the cost.
early P-51Bs were slower than Allison power Mustangs at low altitudes because of the higher drag of the larger fuselage, larger radiator/intercooler and heavier weight of the two stage engines. Once you got high enough for the two stage engine to start making significantly more power than the single stage the Merlin Mustangs really went into a world of their own.

A two stage Allison in a P-63 was around 150lbs heavier than the engine in a P-39N, it was longer and expecting to cool an engine making several hundred hp more needs a slightly bigger radiator (about 20-25lbs more for the P-63) the P-63 used a propeller about 60 lbs heavier.

You can do it, it takes a lot more changes than some people seem to think.

The Merlin system worked but it was also a bit on the crude side (at first look) and many engineers were trying to go one better. The Merlin ALWAYS both impellers spinning at the same time and spinning at the same speed. Effective but not very flexible with a two speed drive. P & W's two stage (first flown in 1939 so two stage superchargers aren't unknown in the US) had a single speed supercharger on the engine and a two speed drive with neutral on the auxiliary supercharger drive given three possible combinations. Allison stuck a hydraulic coupling in the drive the auxiliary supercharger giving an infinite number of combinations between a high and low limit. More elegant from an engineering point of view but you had to pay for it somehow.

The air to air intercooler is more resistant to battle damage. A liquid intercooler suffers just alike a liquid radiator from one or two minor hits. A couple pencil size holes in the airducts of an air to air intercooler isn't going to affect things that much. However keeping all those airducts air tight in day to day operation was more maintenance intensive. You pay your money and take your chances.

 

[Shortround6]

Now there WAS a two stage mechanical Allison, the first production model was the V-1710-93 for the P-63. It featured a separate second stage supercharger driven by a jackshaft from the Allison starter dog that drove through a hydraulic clutch that automatically regulated manifold pressure. The -93 developed 1325HP for takeoff and 1180HP at 21500' with 1825HP war emergency. This pushed the P-63 without wing guns to 422mph at 24000'. They bolted a comparable model onto a P-40 and called it the Q and even that old P-40 went 418mph at 24000' and climbed like a rocket. Only 3 of those Q's were built.

More importantly the -93 was in full production in April 1943 and the P-63 didn't fly until October. Why in the world didn't the Army just put one in the P-39? It fit into the experimental P-39E. The contemporary P-39 model was the P-39N at 7650#. Add the 200# auxiliary stage and balance the weight with a larger 4 blade propeller and you have a real hot rod at 8050#. By July 1943 these P-39s would be coming off the production line and would have rivaled the Spitfire IX and P-51B in speed and climb. But the -93 in a P-39 was not to be, probably because the Army didn't want the Russians to have it. They were the main customer for the P-39 at the time.

Ah, for a P-39 expert you are making a number of mistakes.
P-39E was originally designed for the infamous Continental O/IV/V-1410 which was considerably longer than the Allison engine. With no airworth examples of the Continental engine available (or likely to be) in 1942 the design was altered to take the two stage Allison. the fuselage was 1.75 feet longer than the standard P-39s. One of them weighed in at 8918lbs (some sources say they were nicknamed the "lead sled") P-39E also had a bigger wing. Relationship of wing to engine/fuselage may also be different

Notice where the door is compared to a normal P-39?
Auxiliary supercharger is right about where the oil tank is on a normal P-39.

The P-40Q was hardly a lightweight at 9000lbs when using the V-1710-121 engine, full internal fuel and four guns and ballast to represent 235rpg.
in an early test it using a V-1710-101 engine weighed 8203 lbs with 160 gallons of fuel which leaves us wondering what was left out.

 

[pbehn]

Re 2000, like all contemporary monoplane aircraft, certainly MC 200 and G.50 among Italians ( I have less information about P-35) suffered from bad stall caracteristics, until a German paper at the end of the 30's explained the importance of a correct wash-out. When a correct wash-out was introduced in the wing of MC 200 the flying caracteristics improved dramatically, and the same wing was retained in Macchi 202 and 205.
Re. 2005 had a wash-out of about -2,2°

.

Great post Elmas, but knowledge of washout couldn't just be just held in Germany, the Spitfire flew with it in 1936.