p 40

[Shortround6]

For the Allison it is a question of what was actually available when.
The V-1710-45 (F7) was a 1940 project using the two stage system. The contract was dated Dec 2nd 1940, for one experimental engine.
However change order #1 was issued in June of 1942 and included changing the impeller from 9.5 in to 12.1875 in and changing from the friction clutch to the hydraulic clutch.
The original delivery date of Sept 1941 was changed to February 1943 so one can see how badly the program was slipping (free fall?)
A 2nd contract had been signed in Dec of 1941 for an experimental engine with intercooler.

It also does not appear that you can simply slap a 2nd stage on an engine, fit an "acme"* intercooler and "Bob's your uncle" have an engine that equals a two stage Merlin.
Unless I am reading it wrong This early Allison two stage was fitted with a liquid cooled after cooler, weighed 1545lbs and was to be rated at 1150hp military at 21,000ft running on 100/125 fuel.
Compare that to a Merlin 46 single stage engine.

The Allison V-1710-101 engine was first tested in July 1943 but performance was still a little behind. 1500hp WER at 6000ft (running at 3200rpm) wasn't going to set the world on fire and 1150hp at 20,000ft at 3,000rpm wasn't going to cause anything else to be canceled. There were some modifications done.

The Allison V-1710-121 is the one that matches the Merlin 14SM but it isn't even tested until early 1944.
1700hp at 26,000ft (3200rpm) with water injection is very good. It is too late (and it took quite a while for Allison to sort out the -121 engine, if it was ever fully sorted out?)

 

[tomo pauk]

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.

I'd advise stepping out from the US point of view and take a look at ww2 as a team effort. A team that was using thousands of fighters that were incapable of crossing the 400 mph TAS line unless in dive, even in 1944.
A P-59 jet fighter will not get us very far.

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.

Looks like a P-40 + a 2-stage V-1710 in 1943 can be only named P-40Q.

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

Allies are probably better with Gloster Gladiator there.

 

[Shortround6]

If you can get P-40"Q"s (or whatever you want to call them) with two Stage Allison's in late 1943/early 1944 with NO reduction in other types of planes AND the pilots to fly them (and ground crew) then yes the P-40 "Q" would have made a good addition to the US forces or even allied forces. This assumes that the version of the two stage Allison chosen actually stays operational under field conditions.
From 1943 on P-40s were sent as replacements only to US fighter units (no new squadrons posted overseas) and the number of squadrons using P-40s dwindled as P-40 units in the Field were converted to P-47s and P-51s.
US was starting to supply allied units with P-47s in 1944.
The RAF had 9 squadrons in the CBI theater flying P-47s in 1944.
In March of 1944 the US began supplying P-47s to Free French units that were flying Hurricanes. 446 P-47s were supplied to Free French units in North Africa, more were supplied later.
Brazil had a squadron of P-47s go into action Nov 11th 1944.
Mexico had a Squadron in the Pacific that did 96 sorties (and lost 7 pilots) in the last few months of the war.

The P-40 "Q" just didn't bring enough to the table at that point in the war.
Yes it was better than many of the aircraft that were being replaced but the they were replacing those aircraft anyway and with planes equal to or better than the P-40 "Q".

 

[Thumpalumpacus]

I'd advise stepping out from the US point of view and take a look at ww2 as a team effort. A team that was using thousands of fighters that were incapable of crossing the 400 mph TAS line unless in dive, even in 1944.
A P-59 jet fighter will not get us very far.

I'm not sure where this is coming from. I'm talking about the changes in production demands, not "rah rah USA" stuff.

 

[tomo pauk]

If you can get P-40"Q"s (or whatever you want to call them) with two Stage Allison's in late 1943/early 1944 with NO reduction in other types of planes AND the pilots to fly them (and ground crew) then yes the P-40 "Q" would have made a good addition to the US forces or even allied forces.

There was 2000 P-40s produced in 1944, and another 2000 in the last 6 months of 1943. Making instead 4000 of P-40s that can actually perform is not asking much from Curtiss and Allison.
Pilots that were flying Yaks, La-5s, Hurricanes, P-39s, P-63s, Spitfire Vs, earlier P-40s will benefit, and with them the Allied cause. Eg. Spitfire V was making half of all of Spitfires in RAF service in late 1943.

I'm not sure where this is coming from. I'm talking about the changes in production demands, not "rah rah USA" stuff.

Unless a pilot was in the USAF, his chance to fly a P-51 or P-47 were low, even in 1944. USA was not making fighters for themselves, they were also shipping them to the other Allies.
USAF themselves used a good deal of not-P-51s, not-P-38s and not-P-47s in late 1943 and early 1944.

 

[Thumpalumpacus]

Unless a pilot was in the USAF, his chance to fly a P-51 or P-47 were low, even in 1944. USA was not making fighters for themselves, they were also shipping them to the other Allies.
USAF themselves used a good deal of not-P-51s, not-P-38s and not-P-47s in late 1943 and early 1944.

This is weird. I think you're assuming or imputing views to me that I don't hold. Walking away from this conversation looks like smart money to me. Enjoy your evening, and please don't take this rancorous.

 

[Shortround6]

There was 2000 P-40s produced in 1944, and another 2000 in the last 6 months of 1943. Making instead 4000 of P-40s that can actually perform is not asking much by Curtiss and Allison.

The Allison V-1710-101 engine was first tested in July 1943 but performance was still a little behind. 1500hp WER at 6000ft (running at 3200rpm) wasn't going to set the world on fire and 1150hp at 20,000ft at 3,000rpm wasn't going to cause anything else to be canceled. There were some modifications done.

Allison engines used those late 1943/early 1944 P-40s were the ones with the 9.60 supercharger gears.
engine...............................take-off.............................miltary.................................WER
V-1710-99..........................1200hp..................1150hp/15,500ft................1410hp/9.600ft
V-1710-101.......................1325hp..................1100hp/28,500ft.................1220hp/25,000ft
V-1710-101 (alt).............1325hp..................1250hp/12,000ft..................1500hp/6000ft.

Page 154 of Vees for Victory.

P-40 "Q" went 9000lbs with the weapons load of P-40L or an P-40N-1. The "Stripper" models.

They could have made better "performing" planes in late 1943/early 1944. Go back to the four guns and 235rpg of the L and and first N.
The Later Ns were about 180lbs lighter than the M despite having about 90lbs more radio gear. taking out two guns would save 150lbs and using 235rpg would save another 140lbs.
A bit more work on weight saving, (better workmanship?) clip the wings, perhaps a trip to the wind tunnel
But they didn't. They were using them as trainers and as fighter bombers/ground attack planes and phasing them out (slowly?) in combat theaters.

 

[pbehn]

The Allison V-1710-101 engine was first tested in July 1943 but performance was still a little behind. 1500hp WER at 6000ft (running at 3200rpm) wasn't going to set the world on fire and 1150hp at 20,000ft at 3,000rpm wasn't going to cause anything else to be canceled. There were some modifications done.

Allison engines used those late 1943/early 1944 P-40s were the ones with the 9.60 supercharger gears.
engine...............................take-off.............................miltary.................................WER
V-1710-99..........................1200hp..................1150hp/15,500ft................1410hp/9.600ft
V-1710-101.......................1325hp..................1100hp/28,500ft.................1220hp/25,000ft
V-1710-101 (alt).............1325hp..................1250hp/12,000ft..................1500hp/6000ft.

Page 154 of Vees for Victory.

P-40 "Q" went 9000lbs with the weapons load of P-40L or an P-40N-1. The "Stripper" models.

They could have made better "performing" planes in late 1943/early 1944. Go back to the four guns and 235rpg of the L and and first N.
The Later Ns were about 180lbs lighter than the M despite having about 90lbs more radio gear. taking out two guns would save 150lbs and using 235rpg would save another 140lbs.
A bit more work on weight saving, (better workmanship?) clip the wings, perhaps a trip to the wind tunnel
But they didn't. They were using them as trainers and as fighter bombers/ground attack planes and phasing them out (slowly?) in combat theaters.

Also allow your competitors the same latitude, the P-51D was in no way optimised solely for performance, it was optimised to do the job that it was bought to do, that means carrying more guns and sacrificing some speed for a better view etc.

 

[Shortround6]

For the fans of the V-1710-121 engine the P-40Q-2A was unserviceable for 40 of the 70 days the aircraft was under test. It suffered 3 forced landings due to engine problems, the last on Sept 1st 1944, which pretty much ended it's career with the USAAF. It was used as a racer in 1947, crashing due to engine failure.
The P-40Q-3 crashed due to engine failure only few days into it's test program.

If you want a P-40Q in service in late 1943/early 1944 it would have to use a much lower performance engine than the V-1710-121.

 

[GregP]

Hi nuuumannn,

About your post that the Spitfire XIV was so much better than the mythical P-40Q, I agree. But, and here's the thing, the Spitfire XIV wasn't in service with the U.S.A.A.F., it was in service with the British, which would never help then-current U.S.A.A.F. P-40 drivers.

The proposed P-40Q wasn't in competition with the P-80, either since we only sent four P-80s abroad during the actual war. Four of anything wasn't even worth being called a factor in the war, and they weren't a factor.

What I said and meant was that, for U.S.A.A.F. pilots actually flying existing P-40s in combat during WWII, and they WERE in combat until the war ended, moving from their existing P-40 of any other model to a P-40Q would be a big step up in performance, and that is true notwithstanding the fact that we didn't actually produce any P-40Qs. Had we done so, their new P-40Qs would have climbed better, would have been faster, and would have handled better, all of which are good things for a P-40M/N/etc. driver in 1944 - 1945.

I do not dispute that the P-51 was a bit faster or that it was better overall. The P-40Q would have been a better airplane than any other P-40s that were flown in combat. We produced about 3,400 P-40s in FY 43/44/45. Had they been P-40Qs instead of P-40M/Ns, there would have been virtually no impact to any other production because we actually built and delivered those airframes, so the P-40Qs would not have had to displace any other production other than the P-40s that WERE produced. Of course, we didn't do that. So, the P-40Q is a "what if" that we cannot say anything definite about exactly because it IS a "what if."

I like the airplane myself, but would not have produced it at the time, either, had I been in charge.

As for the Me 262s in combat, the number 300 that saw combat pops up all over the place. One such place is:

Messerschmitt Me 262 A-1a Schwalbe (Swallow) | National Air and Space Museum.

Yes, I believe Afolf Galland. Anyone who wants to dispute him about the state and history of German fighter defenses in WWII had better have some REALLY IMPRESSIVE credentials since he was there and pretty much in the know and pretty much in charge. It's hard to get better data than from the people who were in and directed the war. I call it definite primary source data.

 

[tomo pauk]

The Allison V-1710-121 is the one that matches the Merlin 14SM but it isn't even tested until early 1944.
1700hp at 26,000ft (3200rpm) with water injection is very good. It is too late (and it took quite a while for Allison to sort out the -121 engine, if it was ever fully sorted out?)

The -121 was not able to make 1700 HP at 26000 ft at any RPM. Max altitude for 1700 HP was 15000 ft during the climb (= small ram pressure), or at 20600 ft on 3200 rpm during max speed (= maximum ram pressure); per the XP-40Q-2 flight test report.

Unless I am reading it wrong This early Allison two stage was fitted with a liquid cooled after cooler, weighed 1545lbs and was to be rated at 1150hp military at 21,000ft running on 100/125 fuel.
Compare that to a Merlin 46 single stage engine.

I was going by the power chart of the E11 engine, as installed on P-63A for the early 2-stage engines the P-40 might be powered with by Summer of 1943. Earlier engines - the ones from winter of 1942/43 for example - will do worse.
Merlin 46 power graph is stated as 'provisional' for a good reason; the real figures were worse. Instead the expected +9 psi boost at 22000 ft without ram for power of 1100 HP at 3000 rpm, Spitfires with Merlin 46 were achieving +9 psi boost at 19900 ft at max speed (= max ram pressure). IOW, barely better than Merlin XX or 45.
Closest to the provisional figures were the test examples outfitted with a proper carb, having +9 psi at 22500 ft with max ram pressure/high speed.

 

[P-39 Expert]

The V-1710-93 mechanical two stage engine was in production in April 1943. The first P-63 wasn't ready until October. That's the reason for all the testing between April and October, the engine was ready but the airplane wasn't. By the end of the year they had made only 28 P-63s.

Nothing different about the -93 except the auxiliary stage supercharger. Engine section was the same as any contemporary V-1710. Only variables were the E models had the remote reduction gears and F models did not. Supercharger gears varied between (at this stage of the war) 8.1 (for two stage engines), 8.8 and 9.6. Otherwise the power sections were the same.

Allison produced prototype versions of the -93 in 1942 in Feb, April, June, Aug and Sept, and in 1943 in Jan and Feb. Production in April. No airframe for 6 more months.

Much better to upgrade the P-40 and P-39 with two stage engines than to wait on the P-63. But the Soviets were the main customer for the P-39 and P-40 and our government may not have been interesting in giving them high altitude planes.

Auxiliary stage took way too long to develop. Just an impeller in a diffuser driven by a short shaft from the starter dog. Give up on the intercooler early and mount the carb on the engine like all the other V-1710s and gain another 3000'+ critical altitude. Now it has 1150HP at around 25000'. Single stage V-1710s made about 750HP at that altitude. 400 additional HP at high altitude would have made a big difference. This is without WEP which would have only needed water injection. Not a Merlin, but it had advantages.

 

[GregP]

Several sources report the April 10, 1945 Me 262 mission as 55 aircraft. Here's one:

https://acesflyinghigh.wordpress.com/2019/08/17/the-survivors-messerschmitt-me-262-germanys-jet-fighter/#:~:text=Me 262 losses were reported, been lost mainly to accidents!

"Me 262 losses were reported as only 100 in air to air combat but up to 1,200 Me 262's were destroyed on the ground and in accidents – on April 10th, 1945 a formation of 55 Me 262's went up to attack Allied bombers and by the end of the day 27 of them had been lost mainly to accidents! The jet age had come and changed air combat forever but it was all too late to help the battered Luftwaffe turn the tide of the air war over occupied Europe and Germany."

Reported numbers are always a bit suspect, but sometimes a single document is all we have to go by. So, now we have that mission reported as 76 Me 262s by Juha3 and 55 by another source or sources. I decline to go searching for more sources just now. Suffice to say there was likely a near-maximum Me 262 effort on that day.

Also, suppose you have 50 airplanes ready for a mission and they launch, AND you have 50% of them that are capable of being refueled, rearmed, and launched for a second mission. Now you have 75 airplanes on the same day, but not all at the same time. The number of airplanes doesn't have to be that high to get 75 airplanes into the air in a day.

German records from late 1944 are spotty, sometimes accurate, sometimes mistaken, and sometimes just missing, as could be expected from the wartime situation and the fact that squadron records were usually kept at the squadrons, which were being attacked on a daily basis. I daresay some RAF records were lost, too, for the same reason. I'm not saying that any numbers are exactly accurate down to the last airplane, but I AM saying that the number of combat airworthy Me 262s was very low in general from the various reports and summaries I've read.

 

[Shortround6]

I was going by the power chart of the E11 engine, as installed on P-63A for the early 2-stage engines the P-40 might be powered with by Summer of 1943.

If I may ask which power chart is that?
Not challenging you. Just the only chart I remember at the moment is the one in AHT. Not saying it is wrong, I just doubt the date the WER powers were available.
There may be a bit of disconnect on the E11 engine, They started testing it in April or May of 1943 but , perhaps due to the lack of production P-63s, they didn't finish the 150 hour test until Nov 27th and the WER test was completed until Dec 1943. Early P-63s flew under restrictions in the last few months of 1943 until the tests were completed, then the restrictions were lifted.
The extended test period was due to the effort to develop water injection and the improved pistons and rings needed to stand up to the WER ratings.

 

[pbehn]

Hi nuuumannn,

About your post that the Spitfire XIV was so much better than the mythical P-40Q, I agree. But, and here's the thing, the Spitfire XIV wasn't in service with the U.S.A.A.F., it was in service with the British, which would never help then-current U.S.A.A.F. P-40 drivers.
.

The MKXIV Spitfire had about the same top speed as a P-51B/C or D with better climb and less range which is why the P-51 replaced the P-40.

 

[GregP]

Yeah, I wasn't trying to say the P-51 wasn't better than the proposed P-40Q.

I was trying to say the proposed P-40Q would have been head and shoulders better than the actual P-40 models that were produced. Both would have gone to the same places the actual P-40s went, but the Qs would have performed better than the P-40 models they got ... I wasn't thinking of suggesting trading P-40s for Spitfire XIVs.

Cheers.

 

[tomo pauk]

If I may ask which power chart is that?
Not challenging you. Just the only chart I remember at the moment is the one in AHT. Not saying it is wrong, I just doubt the date the WER powers were available.

No probs
Table at pg. 348, as well as tables at the end of the 'Vee's for victory' book note 1150 HP at 22400 ft for the E11. Data in AHT (1150 HP at 25000 ft) is too optimistic, probably incudes maximum ram. Another figure (1180 HP at 21500 ft) is more realistic for no-ram conditions.

 

[kool kitty89]

For the Allison it is a question of what was actually available when.
The V-1710-45 (F7) was a 1940 project using the two stage system. The contract was dated Dec 2nd 1940, for one experimental engine.
However change order #1 was issued in June of 1942 and included changing the impeller from 9.5 in to 12.1875 in and changing from the friction clutch to the hydraulic clutch.
The original delivery date of Sept 1941 was changed to February 1943 so one can see how badly the program was slipping (free fall?)
A 2nd contract had been signed in Dec of 1941 for an experimental engine with intercooler.

It also does not appear that you can simply slap a 2nd stage on an engine, fit an "acme"* intercooler and "Bob's your uncle" have an engine that equals a two stage Merlin.
Unless I am reading it wrong This early Allison two stage was fitted with a liquid cooled after cooler, weighed 1545lbs and was to be rated at 1150hp military at 21,000ft running on 100/125 fuel.
Compare that to a Merlin 46 single stage engine.

The Allison V-1710-101 engine was first tested in July 1943 but performance was still a little behind. 1500hp WER at 6000ft (running at 3200rpm) wasn't going to set the world on fire and 1150hp at 20,000ft at 3,000rpm wasn't going to cause anything else to be canceled. There were some modifications done.

The Allison V-1710-121 is the one that matches the Merlin 14SM but it isn't even tested until early 1944.
1700hp at 26,000ft (3200rpm) with water injection is very good. It is too late (and it took quite a while for Allison to sort out the -121 engine, if it was ever fully sorted out?)

The USAF "Reciprocating Engine Characteristics" chart lists the -45 as 1515 lbs, but your source may be more accurate (in any case that's little more than the Merlin 20 series single stage 2-speed drive or Packard V-1650-1 at 1520 lbs). If the earlier simple friction clutch was lighter that would've put it more as single-stage 2-speed Merlin competition, but the greater length would still make it more difficult to install on existing production designs. I'm assuming you mean simple mechanical clutch with friction plate for synchronous gear shifting for the "friction clutch" and a fluid coupling torque converter impeller + turbine for the hydraulic one (and not just hydraulic actuation of a mechanical clutch).

If the early mechanical clutch design was still only single-speed, you'd have low blower when de-clutched (with aux-stage free-wheeling similar to when the fluid coupling has no oil in it) and high blower with it engaged. In that context, the intercooler would be more useful/necessary (even conventional air-to-air ones) due to the charge heating you'd get with the aux stage engaged. OTOH, if the integral stage was already geared 8.8 for medium altitude (FTH reduced somewhat due to drag through the pinwheeling aux stage) and single-speed aux stage providing FTH similar to the V-1650-1 or optionally higher than that (more like the Merlin 47) you'd still have low-blower for reasonable take-off and low altitude performance. (the drag from the aux stage should actually allow more take-off power at given manifold pressure than normal 8.8 supercharged engines due to that reduced FTH meaning less drag from the throttle plate and smoother drag from the "dead" aux impeller acting like a swirl throttle)

The big problem with the aux stage V-1710 isn't even it's timing, but inability to be bolted-on to existing designs with minimal modification. If they'd used a bevel gear drive to run the aux stage perpendicular to the integral stage, flush with the port or starboard side of the engine (like the DB or Jumo engines) it should've avoided that issue. Even if the installation protruded and added to frontal area, it should've been better, and the location of a ram intake on the side would've improve the P-40 and P-51's view over the nose slightly, while may have actually improved RAM pressure on the P-39. If they could've done that sort of arrangement with an earlier, more primitive single-speed aux drive, it could've been worthwhile. (2-speed drive on the aux stage would be better, too)

Now the actual production aux stage V-1710s had the advantage of that fluid coupling and smooth power curve along with reduced weight and complexity over an intercooler arrangement, but with the trade-off of charge heating at higher altitude (like the early P-38s or like using a turbo without intercooler, but probably not as bad as a turbo: either due to efficiency of compressor design or additional heating from the exhaust/turbine section, which is very closely coupled on GE turbos at least). However, once the P-51 was in production, it'd have been smarter to contract out modifications for a 2-stage 1710 version while NAA was occupied with Merlin Mustang production, but that's assuming good cooperation and interest between licensees (and from Curtiss's end you could consider other things like licensed F4U production or P-38 production: particularly handing off development of a non-turbocharged P-38 variant to Curtiss with proper ejector exhausts and ram air intake, both with the single and 2-stage alisons). Start with the P-51A as the basis, or start before that with a license given for the initial P-51 design and developing that further in parallel with NAA's efforts. You could simplify some things, omit the bubble canopy, maybe introduce P-40 style scaloping for better rear view along with a sliding canopy with blown out malcolm hood style for improved production (if adapting the P-40's canopy itself was feasible for initial production, transition to a hood would've been much easier to field-mod than the hooded Mustangs, too).




There is one other area specific to Curtiss that could have benefited the V-1710: cooperation with Curtiss-Wright's engine division. That could range from actual consult work to assist in supercharger development, or simply technology sharing: in the 1938/39 timeline range, you have both the R-1820 and R-2600 with larger superchargers and 2-speed drives that might have made a reasonable basis for an auxiliary supercharger on the V-1710. And, aside from using them as a second stage, the integral stage could also be deleted in favor of just a single 2-speed auxiliary stage without the same space constraints of the integral supercharger's location. (that deletion might also allow correcting the kink/bottleneck in the V-1710's induction system, or at least improving it somewhat: I forget if the kink was at the carb/supercharger inlet or downstream of the supercharger outlet, but I think the former, which should mean re-arranging the intake should help). A short-cut for that deletion might have been fitting a dummy impeller disc (if flywheel stability mass was needed), using the supercharger housing as a simple radial intake duct fed from one of the sides, and extending the impeller shaft outside of that casing so it could be used as the external supercharger drive (potentially with a bevel gear), that-is, if it was easier to do that than using the existing accessory drive gears to power the external supercharger. An R-2600 supercharger + V-1710 would also probably be more useful than any R-2600 design studies on the P-36/P-40 airframe.

Overall better technology-sharing between firms during war-time (and potentially waiving license/royaltee fees during war-time) between more engine manufacturers on both sides of the Atlantic (like RR sharing with Allison for that matter, or licensing the Merlin XX supercharger as the Allison's aux stage) may have helped a lot, but even aside from that, the Curtiss-Wright connection would've allowed potential cooperation well before the US entered the war and potentially before the war started in '39. (experiments with Wright superchargers on Allison engines starting in '38/39 resulting in small scale production engines by '41and full scale by '42 might have helped a lot) There could've been contractual conditions with Wright pre-war that gave them exclusive use of those engine models, but may have been later pressured into waiving that some time in 1940-41. (or something more like Wright either supplying the superchargers to Allison or getting royalties for each unit built: given Wright's problematic quality control during war-time, having Allison build them would've been better ... though pre-war or early war that may not have been a problem and I don't think superchargers were generally the point of failure with Wright's production, R-2600 or otherwise) But if it could've been arranged, sharing P&W's aux stage supercharging developments with Allison may have been more helpful (both from the R-1830 and R-2800).

Allison also probably would've had more resources to work on more V-1710 features (supercharger developments, water injection for super or turbo installations, different compression ratios) has the US not been investing in so many experimental, early development stage designs, like the Army's entire Hyper engine project and had undergone some sort of "rationalization" scheme for war-time like Britain did, aside from turbojet developments at least. (albeit prior to the Whittle design being brought over, I think all US turbojet developments were internally/privately funded efforts, and mostly or entirely limited to "paper" design studies)

Given GE's slower pace at improving impeller/diffusor efficiencies early-war, some sort of technology sharing on that front should've been helpful as well. (among other things, it might have even made some intercooler-less turbo installations viable, particularly if there was better compressor + turbine separation/isolation/insulation, or longer shaft arrangements designed specifically to nest behind a V-12 engine with the turbine shaft horizontal and perpendicular to the engine's drive shaft, with the compressor on one side and turbine section on the other, and the turbine shaft nested up against the crankcase) That or GE could have just supplied turbine drive sections a la carte and allowed engine companies to design and mount their own compressor sections to. (I think Wright did some of their own turbocharger development during the war and one or more was tested in the XP-60 project, but having the "hot" section ready-made from GE, offloading that end of development, might have allowed the best of both worlds)



But back onto the P-40 itself, I think it's fair to compare it directly to the Spitfire and 109 in design quality and potential for growth (or the base P-36 to the Spitfire Mk.I and 109D and E). The P-36 was larger and had much larger fuel capacity from the start, and maintained more internal fuel tankage even as it decreased up to the D/E with 149 US gal (then increased slightly again with the F/K to 157, then down to 122 in the stripper P-40N, but 161 gal with the non-stripper N versions). And comparing it to 2-stage merlin, let alone Gryphon engined Spitfires is hardly fair as US production didn't have those available (or had production consumed by the P-51B/C/D already). OTOH you could argue the lower weight of the 2-stage allison might benefit the Spitfire more than it did any P-40 or P-51 installations. (though it should've helped with range and/or specific fuel consumption: ie same range on less fuel in a hypothetical war-time Allison P-51) The P-40 is somewhat bigger, somewhat heavier, but pretty clean/low drag considering that vs the 109 and Spitfire, it had much better high speed control forces and handling from the start (and the Spitfire played catch up) and higher rate of roll even at low speeds, giving it turn-reversal advantages in combat, plus faster split-S diving (and better dive acceleration due to sheer weight + clean airframe) to allow for diving as an escape maneuver when wishing to leave combat.

Also note: part of why the P-40 was heavier was the same reason all US fighters tended to be overweight (even when unarmored pre-war), and that was due to higher max G-force specifications from the USAAC (and I believe USN as well, though carrier fighters need added strength for landing, too).

 

[GregP]

The Allison V-1710-101 engine was first tested in July 1943 but performance was still a little behind. 1500hp WER at 6000ft (running at 3200rpm) wasn't going to set the world on fire and 1150hp at 20,000ft at 3,000rpm wasn't going to cause anything else to be canceled. There were some modifications done.

Allison engines used those late 1943/early 1944 P-40s were the ones with the 9.60 supercharger gears.
engine...............................take-off.............................miltary.................................WER
V-1710-99..........................1200hp..................1150hp/15,500ft................1410hp/9.600ft
V-1710-101.......................1325hp..................1100hp/28,500ft.................1220hp/25,000ft
V-1710-101 (alt).............1325hp..................1250hp/12,000ft..................1500hp/6000ft.

Page 154 of Vees for Victory.

P-40 "Q" went 9000lbs with the weapons load of P-40L or an P-40N-1. The "Stripper" models.

They could have made better "performing" planes in late 1943/early 1944. Go back to the four guns and 235rpg of the L and and first N.
The Later Ns were about 180lbs lighter than the M despite having about 90lbs more radio gear. taking out two guns would save 150lbs and using 235rpg would save another 140lbs.
A bit more work on weight saving, (better workmanship?) clip the wings, perhaps a trip to the wind tunnel
But they didn't. They were using them as trainers and as fighter bombers/ground attack planes and phasing them out (slowly?) in combat theaters.

The Merlins weren't doing much better in large part ...

Merlin XX: 1480 hp ... 6000 ft
Merlin 47: 1415 hp ... 14000 ft (less at 28500 ft)
Merlin 61 made 1565 hp . .12250 ft and 1390 hp at 23,500 ft.

The above were a bit more powerful than the Allison, but not by a lot. Not insignificant, but not a huge leap, either. Still, the Merlin was a better choice for the war in the ETO, which was definitely a higher altitude war than other theaters.

Merlin 76/77: 1233 hp ... 35000 ft. Now this one was a pretty decent jump in hp / altitude.

P-40Q was a good airplane, but not a leap above others already in production. Still, it would have been much better than standard P-40s that were delivered, and would not have impacted other production. It didn't happen, but could have without affecting other-than-P-40 airplane deliveries. Sort of a "might have been done without a lot of negative effect."

Had I been in charge, I might not have produced the P-4Q, either, so I can't quibble about the decision.

 

[Macandy]

They were a tough, dependable workhorse.
They got the job done, and hung on right in there til the end of WWII bombing bad guys.