Should the US have used either the Vultee P66 or Curtis-Wright CW21?

[Shortround6]

I imagine a supercharger optimized for 18k' might have helped some but from charts it looks like the Allison -39 single-stage SC the P&W -86 first stage kicks in about 12-15 k' while the second stage of the P&W kicks in about 20k" I haven't found any P&W charts for a single stage supercharger so not sure where the G205 or similar engine (for example P&W 1830-90) kicks in.

A P&W R-1830 needed 48in of map to make 1200hp. Nobodies single stage supercharger of 1941 could deliver that pressure in a usable manner at 18,000ft except the Merlin modified by Hooker and even then the power needed to drive it cut into the power output.

ALL US radials with single stage superchargers had a critical altitude of under 15,000 even in high gear. edit> at the time, the Cyclone in the FM-2 has a critical altitude of 17,000ft. but it doesn't show up in production until the middle of 1943, First production FM-2 is in in Sept 1943) < edit

In a Navy proposal Curtiss estimated a top speed of 351 MPH for a navalized Hawk equipped with the -76 engine. [/I]"

Pratt did much better than that but not until the fall of 1942 with their test mule. the question is what did they give up?

This is a picture of the two stage Hawk tested in the 1939 Army fighter trials with an early P W two stage engine, it may have been a quick and dirty job to make the time limit, I don't know. I believe the bulge just behind the engine on the bottom is the auxiliary stage of the supercharger ( it corresponds to the position shown in patent drawings) unlike the engines used in the Wildcats were the Aux stage is behind the normal supercharger. Please notice the duct/pod under the cockpit and behind the left wheel/landing gear. This would be the inter-cooler, needed to get the high altitude performance but a real "drag" at low altitude. A two stage engine and inter-cooler could be several hundred pounds more than a single stage.

The P W test mule ( I believe I posted a picture in another thread ) had some really big scoops above and below the engine but didn't have any cowl guns and ammo tanks to get in the way of the supercharger bits and pieces.

FOund it :

 

[oldcrowcv63]

Thanks, SR, I kinda figured there'd probably be no easy answer to the prospect of an upgraded 2-stage P-36, but unless I asked the question...

 

[Shortround6]

Seems like the P-36 high altitude performance might have benefited from replacing the P&W 1830 SG205 with the F4F-4's two-stage supercharged, P&W 1830-76 or -86? Is there a reason why this couldn't have been done to give the USAAF a better high altitude capability than wither the P-40 or P-39 could manage? Was the production being monopolized by F4F-3 4 production?

At one point yes. While the Martlet II III may have gotten single stage superchargers because the US wouldn't release the two stage for export (just a guess, don't know for sure) the US did take 65 F4F-3As with single stage superchargers because of engine shortages, most went to the Marines.

 

[pinsog]

Pinsog, why don't you add the Republic P-43 to that list ??
Kris

I think I did a thread on the P43 one time. I think it would have been useful also. Maybe at Midway, Guadalcanal or Austrailia. The P47 proved if something was fast up high and could dive well, then it could be succesful using zoom and boom tactics. I would have preferred the P43 over the P40 against the Japanese.

 

[Civettone]

I wonder which would be the best: P-43 or P-66 ?



Kris

 

[oldcrowcv63]

I think I did a thread on the P43 one time. I think it would have been useful also. Maybe at Midway, Guadalcanal or Austrailia. The P47 proved if something was fast up high and could dive well, then it could be succesful using zoom and boom tactics. I would have preferred the P43 over the P40 against the Japanese.

According to Wiki:

https://en.wikipedia.org/wiki/Republic_P-43_Lancer

the P-43A is powered by a P&W 1830-49 engine with a single stage supercharger, its gross weight is about the same with empty about 300 lbs less than the P-40E. It has about the same level speed at, I assume, a similar altitude. How can it ceiling be 7.000' higher? I don't get it. It seems to me they'd be very similar performing aircraft. I would expect the high ceiling to be for turbocharged YP-43, not the production P-43A model. Any insight on this?

 

[oldcrowcv63]

I wonder which would be the best: P-43 or P-66 ? Kris

I'd expect the P-43A would have the performance edge. At the very least, it had growth potential. The P-66 also had the mixed armament of 2 x .50"'s and 4 x .30"s while the P-43 had the 4 x .50"'s which I tend to think was a better overall suite.

Oops, late entry, evidently at least some of the production P-43A did possess the prototype's turbocharger but the aircraft lacked armor and SSTs. Apparenly according to wiki there were other problems as well as vulnerability.

An interesting old thread with some little relevance.

http://www.ww2aircraft.net/forum/en...percharging-high-altitude-fighters-24494.html

 

[pinsog]

I'd expect the P-43A would have the performance edge. At the very least, it had growth potential. The P-66 also had the mixed armament of 2 x .50"'s and 4 x .30"s while the P-43 had the 4 x .50"'s which I tend to think was a better overall suite.

Oops, late entry, evidently at least some of the production P-43A did possess the prototype's turbocharger but the aircraft lacked armor and SSTs. Apparenly according to wiki there were other problems as well as vulnerability.

An interesting old thread with some little relevance.

http://www.ww2aircraft.net/forum/en...percharging-high-altitude-fighters-24494.html

ALL P43's had the turbo charger, hence the high altitude performance edge over any other USA fighter except the P38

 

[davebender]

G4M naval bombers were a superior weapon during 1941 and early 1942 but Japan didn't have many. In fact they didn't even have enough for IJN 11th Air Fleet so part of the force was equipped with older Nell bombers.

Ki-27 fighter and Ki-30 light bomber were most numerous IJA aircraft employed in Philippines and many other places. P-36 with properly trained pilot can handle that threat.

 

[oldcrowcv63]

G4M naval bombers were a superior weapon during 1941 and early 1942 but Japan didn't have many. In fact they didn't even have enough for IJN 11th Air Fleet so part of the force was equipped with older Nell bombers.

Ki-27 fighter and Ki-30 light bomber were most numerous IJA aircraft employed in Philippines and many other places. P-36 with properly trained pilot can handle that threat.

But what took out a quarter of the FEAF Pursuit assets on the first day was the A6M and they continued to come in waves on subsequent days. By the end of December there were only about 25% of the original number left, most victims of the Zeros, although accidents and misc aircraft also took a toll. The pursuit ships were finally pulled from defense and spent virtually the rest of the campaign in mainly recon or occasional limited low-altitude strike duty. Java was a replay of the PI as was Darwin. The latter campaign lasted for the next 6 months or longer although by about April/May '42, the 49th FG may have been making mods to their aircraft to even the odds.

 

[davebender]

I disagree.

FEAF was devastated 8 Dec 1941 (Philippine time) by Gen. Brereton's incompetence. Incoming IJN air raid was tracked on radar yet he was unable to coordinate aerial interception. By noon he gave up and ordered his pilots to land en masse so they could eat lunch. To make matters worse the aircraft weren't properly dispersed after landing. While his pilots were eating lunch IJN 11th Air Fleet arrived and cleaned house.

 

[oldcrowcv63]

I disagree.

FEAF was devastated 8 Dec 1941 (Philippine time) by Gen. Brereton's incompetence. Incoming IJN air raid was tracked on radar yet he was unable to coordinate aerial interception. By noon he gave up and ordered his pilots to land en masse so they could eat lunch. To make matters worse the aircraft weren't properly dispersed after landing. While his pilots were eating lunch IJN 11th Air Fleet arrived and cleaned house.

It seems to me, your description of events on December 8th is inaccurate in some essentials and your assignment of accountability appears misplaced.
FEAF was hurt but not totally devastated at Clark field on December 8th. The events are more complicated and owed much to the savvy of the Japanese veteran leadership and experienced, skilled airmen. The bombers got thru to knock out most of the 20th PS's P-40Bs, one of only two of the four squadrons of P-40s (3rd, 17th, 20th, 21st PS) that landed for 'lunch' (an unfair slight because they had been airborne for ~2.5 hours, awaiting the arrival of the first attack). The P-40E could not have stopped the raiders even if 'Brereton' had run a perfect intercept. Moreover, Brereton didn't run intercepts. That was done from a lower operational level. assigment of defensive priorities seems to have been one of the problems and besides Group CO Major Grover, it isn't clear who is to blame, if anyone. The P-40E could barely make it to the enemy aircraft's altitude, That was well established before December 8, from practice intercepts. The P-40Bs had a bit better capability but were among those A/C caught on the ground by high level bombing that was so accurate that I read somewhere there were questions about whether the Japanese had acquired the Norden Bombsight. The 20th pursuit's planes were nearly wiped out by high flying IJN bombers.

The 17th and 20th were assigned to patrol at 15,000' North of Clark AB and intercept raiders before they reached the base. The 34th was assigned to a backstop position over Clark. The 17th 20th PSs were in position at ~8:45 AM. At ~11 AM the two squadrons landed at Clark to refuel. At 11:47 AM a warning was received at Clark ops that Iba Radar had picked up raiders headed South at ~70 miles West of Lingayan Gulf. That flight appeared to Maj. Grover to be headed for Manila. Grover issued orders to launch the 3rd PS at Iba to orbit Iba at 15k' (which would have been wise if the P-40E could have actually protected the RADAR there). He also ordered the 21st (at Nichols field near Manila) and 34th PS (at Del Carmen south of Clark) to launch and cover Clark AB. So far so good. Except orders to actually launch the P-35As at del Carmen were never received and apparently never issued.

Shortly after t/o, during their climb, the planes of the 17th PS are redirected to cover Manila. At 11:45 AM The 21st is also launched and unlike the other squadron COs, Dyess takes his P-40Es to 24k', an altitude which is about as high as he can go and still retain some decent forward speed to get where he needs to go to effect an intercept. Dyess also receives the order to orbit Manila Bay and cover the western approach to the city. Apparently Grover, Group CO, Believed the 3rd PS couldn't intercept the japanese aircraft over Iba and decided their target was Manila.

At 12:15 PM, Grover orders the 17th into the air from Clark, but he wants them to patrol Manila Bay and protect the city. What in the world was he thinking? Finally at 12:20 PM at Nielson field (near Manila) Air Warning HQ, Harold George and his Ops Officer Bud Sprague intercede and orders via the teletype to intercept enemy a/c headed for Clark. The only untasked A/C available to respond are the 20th PS, the pilots of which are sitting in their P-40B cockpits ready to launch, awaiting orders. Yet, Grover holds the 20th back from immediate launch. At about that time, 8 P-40Es of the 3rd PS on patrol at ~15k' over Manila bay had heard radio traffic alerting them of a threat to Clark field. At about the same time, 4 P-40Es of the 21st PS apparently at 24k' also arrive almost by accident over Clark. For a brief moment, Clark is actually covered by 12 P-40Es which would have been woefully inadequate but at least something to interpose ineffectually between Clark field and a relentless enemy bent on destroying it. This was the first combat intercept of the war for the USAAF and its not hard to imagine them botching it.

Seeing nothing happening over Clark all 12 P-40Es head for Iba. At 12:30 PM, Iba reports a large group of A/C headed for Iba Field, NOT Clark. The first direct warning of an attack at Clark is by a 20th PS crew chief on the ground who sees them coming at 12:35 PM.

Yes, there was radar tracking but for some reason, there was a problem in figuring out where the track was headed. Clark AB as the target apparently had only about 10-15 minutes of warning, at best.

The first three of the 20th PS P-40Bs T/O and then the bombs hit damaging or destroying most of the remaining 9 P-40Bs of the 20th A, B, and C Flights killing 4 pilots and seriously wounding 3 others. They weren't having lunch, they were following orders to take off which is what they had been waiting to do since their a/c had been serviced. Sandwiches had been brought out to them to eat while they sat in their cockpits at the ready. Brereton didn't issue the order to land before the attack, the squadron CO's did, out of necessity, not for lunch. Not having to worry about interceptors, the A6Ms were soon down among the P-40s wreaking havoc among the 3rd PS. Observers reported the bombers hitting Iba were at ~25k', well above the highest of the P-40s which were no higher there than about 15k'. 3rd PS CO Thorne approached burning Iba at 15k', saw retiring IJN bombers at 23k' he was unable to climb past 21k' to intercept due to a variety of factors. That was the closest to a revenge intercept made that day.

During the 8th of December, the 6 airborne flights of the 17th and 21st PS orbit ineffectually over Manila Bay and never engage the enemy.

On subsequent days and in other campaigns, the inability of the P-40E to intercept Japanese raids became well known and equally well documented.

I too looked for a scapegoat on whom to hang the FEAF disaster and have come to the conclusion the leaders and men fought about as well as could be expected for that stage of the war. I don't see Brereton or even Big Mac as culprits any more. Compared to the military disasters befalling other nations in other southeast asian sectors, they did fairly well in the long run. Perfection seems a bit much to hope for at this early stage of the war especially when it was elusive even in more mature or experienced times.

This post owes much to renrich. MHRIP

 

[oldcrowcv63]

Questions I have had about December 8 include:

1. why did the IJN choose a path that followed the West coast of the PI rather than coming straight toward Clark and Iba Field (the two primary targets) from their bases on Formosa?

A: It seems to me that, not being totally familiar with Radar capabilities, the IJN leadership decided the safest route to follow South to their targets would be out to the West of Luzon and then approach their targets from direction, coming in to Luzon from over the ocean. Avoiding an approach over either Laoag City or Cape Engano both well over 200 miles north of their targets, they prevented an anticipated enemy early warning of over an hour. Approaching from the west, meant detection by ground based spotters would be limited to visual range with feet dry about ~35 miles from Clark AB or about ~10 to 20 minutes of early warning. Iba field would have no more than what visual range from the beach provided. That may seem obvious to most, but why wasn't it to Grover?

2. Why was Grover obsessed with Manila? Deploying the three airborne P-40E squadrons (3rd, 17th and 21st) to orbit Manila Bay seems extreme overkill and then sitting on the 20th when his own base is certain to be a target seems to defy common sense.

A1? Was he being directed by Mac's HQ to defend the General? If so would such orders have come from Mac? I doubt that. Mac was as oblivious to the personal risk he faced exposed to aerial bombardment as he was under artillery assault. On the other hand, the sycophantic Sutherland apparently fancied himself an aerial warfare expert and may have demanded that Grover defend his general in Manila. If so there are no records of which I am aware to confirm this.

A2? It was just as likely to be a combination of buck fever and Grover's confusion in interpreting the mixed warning signals coming in on the teletype. The USAAF did not have the experience of two years of war as had their British cousins.

Whatever Grover's shortcomings, it seems to me FEAF's air warning operations center located at Nielson Field near Manila understood fighter direction in theory but had no real experience in applying it under combat conditions. George and Sprague were exceptionally capable officers who became nearly legendary in the first few months of the war until they both suffered untimely deaths in April and February respectively. On Bataan, the Radar warning became, with experience, far more proficient, although probably never perfect. On board carrier, even with RN advisors, it was problematic throughout 1942.

I should add Bill Bartsch (Doomed at the Start) as a source of most of my info on this topic.

 

[pinsog]

So wouldn't they have been better off in the Phillipines campaign with either the P66, CW21 or the P43? All 3 of these fighters have the ability to climb high enough to intercept the attackers. The P40 was a good fighter below 15,000 feet, but if attackers are coming in higher than your service ceiling it doesn't matter how good you are down low. Back to my original question: Should we have built and used the P66, CW21 or P43? At least they could get high enough to engage the enemy.

 

[oldcrowcv63]

personally I am not a fan of the P-66, I don't believe it had a service ceiling sufficient to engage the IJN aircraft unless the engine was appropriately supercharged. With the P-66's mixed battery, I believe the P-40B/C/D would be a better choice than the first two (P-66, CW-21). The D had a higher service ceiling and climb rate than the E but was still a bit heavy. Service ceiling might have been perhaps ~1,000+ feet higher than the E by reducing the ammo load. On the other hand, dropping four 0.50" guns probably gives you something in excess of a 30,000 foot ceiling. The USAAF P-40E weight-reduction tests in Australia included deleting four of the six 0.5" guns. Australian tests combat-demonstrated a ceiling of 32,000 ft. Trouble with the USAAF's modifications was the deletion of the radio which was pretty essential tool for a radar directed interceptor. Deleting two or four of the P-40E's 0.50"s may also yield some maintenance or logistical benefits. This appears to have been the favored solution among some pilots of the 49th FG in Australia. The turbocharged P-43 sounds like a winner except for its lack of armor, SST and its reputed operating problems. If they can be corrected, then that might be the best choice. I just don't have a feel for how practical that would be or how many would have been available. As I understand it, the roughly 75+ P-40Es sent to the PI, were a large fraction of the P-43's total production.

I obtained the attached document from Australian Gordon Birkett. Since then I have been corresponding with a 49th FG radio technician who made the comm modifications to the test P-40E Base Fighter (see attached). He told me the concept as tested was abandoned because an interceptor without a radio was deemed useless

On the other hand, other modifications made prior to (and whose results may have motivated) the official test effort might have lived on. George Kiser is known to have flown and been quite successful with his 4-gun P-40E.

 

[Shortround6]

Back to my original question: Should we have built and used the P66, CW21 or P43? At least they could get high enough to engage the enemy.

Getting high enough is debatable.

Next question is are you talking about "as they existed" or "as hypothetical modified"?

According to Joe Baugher's web site performance for eh the Vultee 48C was: "The maximum speed was 340 mph at 15,100 feet. Initial climb rate was 2520 feet per minute, and an altitude of 19,680 feet could be attained in 9.2 minutes. Service ceiling was 28,200 feet,..."

Once again, service ceiling is the altitude at which the plane can still climb at 100 ft per minute. the operational ceiling is several thousand feet lower, perhaps 6-8,000ft lower
See performance for a P-40B; http://www.wwiiaircraftperformance.org/P-40/P-40B_41-5205_PHQ-M-19-1227-A.pdf

Please note that it can out climb the Vultee 48C/P-66 by a fair margin, Please also note that at max continuous power (not Military) it took 8 min to climb from 25,000ft to 30,000ft and another 12 minutes to climb 2400ft to it's SERVICE CEILING

Please note that these tests were done at the manufacturer's plant in Buffalo, New York in the spring time. Performance in tropical conditions would be less.

If the service ceiling of the P-66 is 4,000 ft lower than a P-40B one can only wonder what it's operational ceiling was like.

There seems to be quite a bit of debate about the actual performance of the CW-21 and even some as to it's armament. The 4,500fpm climb is rather doubtful and with the radio listed as "optional" instead of "standard" actual performance in combat equipped condition even without armor and self sealing tanks is subject to question.

Please note that the engine was good for several hundred LESS horsepower than the engine in the early P-40s at 12-13,000ft. Armament could be one .50 and one .30, one .50 and three .30s, two .50s and two .30s. with penalties in performance for the heavier armament.

Another question is timing, Both the P-66 and CW-21 had been out of production for months before Pearl Harbor. When do you order them to get them to the Philippines in time for Dec 1941?
There are more P-43s available but here you may run into the reverse problem, Last P-43s come of the production line in March of 1942 On Long Island New York. You would have had to ship aircraft to the Philippines in Sept/Oct of 1941 at the latest to have them ready in the beginning of Dec. The AVGs P-40s were shipped in June/July of 1941 and did not go into action until AFTER Pearl Harbor.

 

[pinsog]

Getting high enough is debatable.

Next question is are you talking about "as they existed" or "as hypothetical modified"?

According to Joe Baugher's web site performance for eh the Vultee 48C was: "The maximum speed was 340 mph at 15,100 feet. Initial climb rate was 2520 feet per minute, and an altitude of 19,680 feet could be attained in 9.2 minutes. Service ceiling was 28,200 feet,..."

Once again, service ceiling is the altitude at which the plane can still climb at 100 ft per minute. the operational ceiling is several thousand feet lower, perhaps 6-8,000ft lower
See performance for a P-40B; http://www.wwiiaircraftperformance.org/P-40/P-40B_41-5205_PHQ-M-19-1227-A.pdf

Please note that it can out climb the Vultee 48C/P-66 by a fair margin, Please also note that at max continuous power (not Military) it took 8 min to climb from 25,000ft to 30,000ft and another 12 minutes to climb 2400ft to it's SERVICE CEILING

Please note that these tests were done at the manufacturer's plant in Buffalo, New York in the spring time. Performance in tropical conditions would be less.

If the service ceiling of the P-66 is 4,000 ft lower than a P-40B one can only wonder what it's operational ceiling was like.

There seems to be quite a bit of debate about the actual performance of the CW-21 and even some as to it's armament. The 4,500fpm climb is rather doubtful and with the radio listed as "optional" instead of "standard" actual performance in combat equipped condition even without armor and self sealing tanks is subject to question.

Please note that the engine was good for several hundred LESS horsepower than the engine in the early P-40s at 12-13,000ft. Armament could be one .50 and one .30, one .50 and three .30s, two .50s and two .30s. with penalties in performance for the heavier armament.

Another question is timing, Both the P-66 and CW-21 had been out of production for months before Pearl Harbor. When do you order them to get them to the Philippines in time for Dec 1941?
There are more P-43s available but here you may run into the reverse problem, Last P-43s come of the production line in March of 1942 On Long Island New York. You would have had to ship aircraft to the Philippines in Sept/Oct of 1941 at the latest to have them ready in the beginning of Dec. The AVGs P-40s were shipped in June/July of 1941 and did not go into action until AFTER Pearl Harbor.

Just from what limited info I have found, the CW21 seemd so close to the Zero in every way, I assumed the performance was nearly the same, with the advantage that the CW21 engine had more potential for growth than the Zero did.

If available, with perfect 20/20 hindsight of course, I think I would have had a mix of P43 and P40's.

What would you choose with 20/20 hindsight that was historically available?

 

[davebender]

If attackers are coming higher then your service ceiling your engine needs a better supercharger. It doesn't matter if that engine powers a P-40 or CW21, without a proper supercharger you will be at an altitude disadvantage.

Give the P-40 a better supercharger and forget about the P66 and CW21.

 

[Shortround6]

Just from what limited info I have found, the CW21 seemd so close to the Zero in every way, I assumed the performance was nearly the same, with the advantage that the CW21 engine had more potential for growth than the Zero did.

There is an awful lot about the CW-21 that doesn't add up. Like the gross weight of 4500lbs. If the empty weight is 3,382 lb that leaves 1118lbs for payload which isn't really enough. Most countries figured 200lbs for the pilot (including parachute) but lets use 180lbs, that brings us to 938lbs. Two .50 cal guns and two .30 cal guns weigh 197.5lbs (without accessories), giving them 200 rounds for each .50 and 500 rounds for each .30 is another 165-175lbs, that leaves 575lbs. The Brewster 239 with same engine engine held 68lbs of oil. that leaves 507lbs for a radio, oxygen equipment, assorted little stuff (like gun sight, flare pistol, etc) and FUEL. Even upping the weight to 4750lbs leaves you rather short of payload. Makes you really wonder how much exaggeration was in the advertised performance figures and what a combat equipped aircraft could really do.
The Cyclone did have more potential for growth but the Cyclone went through several major changes in it's life, The "G" engine used in the CW-21 and the Early Buffaloes was direct drive (no reduction gear) and was several hundred pounds lighter than the next series engines, The "G100" Series (about 1100hp) and the "G200" series went to 1200hp. BUT they used different crankcases and had other changes. They also needed larger (heavier Propellers).

The CW-21 has too many unknowns or modifications to really tell how it would have wound up.

If available, with perfect 20/20 hindsight of course, I think I would have had a mix of P43 and P40's.

What would you choose with 20/20 hindsight that was historically available?

The P-43 is also a bit iffy, it it worked the way it was supposed to it might be a very good choice, unfortunately while we are told it had problems we are not told how bad they were (although self sealing tanks that leak without getting shot are pretty bad). What we don't know is what percentage of aircraft had these problems or how often they occurred (and faulty turbo controls can negate it's main advantage).

The best choice might be to take the P-40 and just cut the armament/fuel load/tanks. Take a P-40C and throw out the cowl .50s and replace with .30 cal mgs. that saves 84lbs (or more) but the big savings comes with the ammo. 380rpg of .50 cal ammo weighs 228lbs
compared to 65lb for 500 rpg of .30 cal ammo. if you cut the ammo to 400rpg you can save over 283 lbs maybe over 300lbs total. six. 30 cal guns should take care of most early war Japanese planes.
Pulling the the behind the seat tank or swapping it for a non-self sealing tank will save another 400lbs or so if the tank is taken out or not filled if non-self sealing for intercept duties (purge with CO2?).
Cutting roughly 10% in weight from the P-40C may improve performance at height enough.

 

[Shortround6]

If attackers are coming higher then your service ceiling your engine needs a better supercharger. It doesn't matter if that engine powers a P-40 or CW21, without a proper supercharger you will be at an altitude disadvantage.

Give the P-40 a better supercharger and forget about the P66 and CW21.

There is another way, more later.

Except there is no better supercharger available at the time, there are two solutions in the works but they are too late. The P-40F first rolls out the Factory door Jan 3 1942 but Buffalo New York is a long way from the front lines. The Allisons with the 9.60 supercharger gears are months away for production, the existing gear case is too narrow. The narrow 9.60 gears tried in prototype engines fail. The gear case is part of the block casting so you need new engine block molds/patterns to fit the new gears.

The other way to "improve" service ceiling to lighten the plane. The P-40 went from 6800lbs on the early ones to 8290lbs (without drop tank) for the "E", while armor and self sealing tanks get some of the blame the increase in gun and ammo weight was substantial. From around 335lbs to 900lbs and that may not reflect the full weight of the ammo boxes and accessories. Throw 550lbs into a 109E or Spitfire or Hurricane and see what happens to the service ceiling.

A P-40B had about twice the rate of climb at 25,000ft that a P-40E had and could climb to 25,000ft in 12 minutes instead of 19.4 minutes. Other tests may vary but should show a somewhat similar difference. The US paid a lot for that six .50 armament.

Enough change to make the difference?