The P-38J and L in the European theater.

[P-39 Expert]

Again, where?
There's already fuel cells installed in areas that won't affect the aircraft's performance (i.e.: roll rate, etc.) or compromise the wing's structural strength. There's really no room left. You can't just arbitrarily stuff a tank here and there without some sort of trade-off. Additional tanks means additional weight with the tank, interior baffles and self sealing compound. Then add the weight of the fuel itself and then pumps, plumbing and such.

And removing the guns? Then what does the pilot do, use the centerline cannon as it's sole armament?

Bell's engineers were pretty clever people, we can pretty much assume that they placed as much fuel capacity in the wings as was practical.

Again, where?
There's already fuel cells installed in areas that won't affect the aircraft's performance (i.e.: roll rate, etc.) or compromise the wing's structural strength. There's really no room left. You can't just arbitrarily stuff a tank here and there without some sort of trade-off. Additional tanks means additional weight with the tank, interior baffles and self sealing compound. Then add the weight of the fuel itself and then pumps, plumbing and such.

And removing the guns? Then what does the pilot do, use the centerline cannon as it's sole armament?

Bell's engineers were pretty clever people, we can pretty much assume that they placed as much fuel capacity in the wings as was practical.

Room for more fuel outboard of the present tanks, and forward of the main spar the entire span except where the landing gear strut goes through the spar. Lots of room there. Yes that would call for the removal of the water injection tank and the .50MG. Remaining armament of one 37mm cannon and two .50MGs is plenty for shooting down LW interceptors.
There would be no water injection for WEP but, honestly WEP added 3mph to the top speed of the P-51D and 8mph to the P-38L. Less than 10mph for the chance to blow up your engine (over enemy territory) and piss off your crew chief for the extra work.
The weight saved by deleting the WEP water (200#) and .50MGs (350#) alone is the equivalent of 91 additional gallons for a total of 223 gallons internal for NO EXTRA WEIGHT. Probably room for more fuel than that. Plus three drop tanks.
And Bell engineers were clever but the configuration, fuel, armament etc was specified by the AAF. Bell had very little say in the matter.

 

[P-39 Expert]

Biff - the dominant issue is a.) they were always late on deliveries, causing the NA-73X/Mustang I deliveries to RAF to slide, and b.) they made significant changes without alerting NAA, also causing re-work at NAA and see a.) above.

In fairness, Material Command were in Allison's shorts and caused many of the aforementioned changes

Could the late deliveries possibly be blamed on AAF allocating engines for domestic planes instead of a plane ordered by the British? Just a thought.
And the government was definitely in Allison's shorts. Took the AAF forever to delete the worthless backfire screens (mid '42) after Allison had told them that the backfire problems were behind them with adjusting valve clearance and moving to an aluminum intake manifold from the (flammable) magnesium manifold among other things.

 

[GrauGeist]

Room for more fuel outboard of the present tanks, and forward of the main spar the entire span except where the landing gear strut goes through the spar. Lots of room there. Yes that would call for the removal of the water injection tank and the .50MG. Remaining armament of one 37mm cannon and two .50MGs is plenty for shooting down LW interceptors.
There would be no water injection for WEP but, honestly WEP added 3mph to the top speed of the P-51D and 8mph to the P-38L. Less than 10mph for the chance to blow up your engine (over enemy territory) and piss off your crew chief for the extra work.
The weight saved by deleting the WEP water (200#) and .50MGs (350#) alone is the equivalent of 91 additional gallons for a total of 223 gallons internal for NO EXTRA WEIGHT. Probably room for more fuel than that. Plus three drop tanks.
And Bell engineers were clever but the configuration, fuel, armament etc was specified by the AAF. Bell had very little say in the matter.

So, forward of the main spar...ok, and what, remove the formers? Install dozens of tiny little tanks?

Removing the MGs from the wing leaves the syncro'd MGs in the cowl, which had a lower rate of fire. In a time when air forces were increasing armament, going back to a 1930's philosophy of two MGs is not providing much of an advantage, even if they increased it's range from 450 miles to a thousand.

And it was most certainly Bell's engineers that ran the show. The USAAF provides a specification and the engineers work to meet that spec. The Air Force didn't hand blueprints to Bell and asked them to make it.

 

[P-39 Expert]

I think the P-40Q WAS an answer to MANY U.S. needs during WWII. It would have been a very welcome addition / replacement everywhere the P-40 was flying in wartime service, and we flew them from before the war started until after the war ended. Had it been possible to extend the range, it could have been useful in places other than where the P-40 was the mainstay.

I am not saying it would have replaced something and become a war winner. I am saying it was head and shoulder better than ANY standard P-40, and we flew those in every theater of war right up to and past the end of the war. So, Yes, the P-40Q would have very useful and welcome by any P-40 command.

Regarding Post #275, good synopsis. Had Allison been instructed to work on a 2-stage integral supercharger, then they would have done so or at least tried.

I have been part of Motorola in the past, we we were asked to so so many things in electronics by the government that caused issue with other things that it isn't even funny. It would not surprise me in the least to find out things were the same in WWII.

Agree completely. The two stage Allison would have totally transformed the performance of the P-40, P-39 and P-51.

 

[P-39 Expert]

So, forward of the main spar...ok, and what, remove the formers? Install dozens of tiny little tanks?

Removing the MGs from the wing leaves the syncro'd MGs in the cowl, which had a lower rate of fire. In a time when air forces were increasing armament, going back to a 1930's philosophy of two MGs is not providing much of an advantage, even if they increased it's range from 450 miles to a thousand.

And it was most certainly Bell's engineers that ran the show. The USAAF provides a specification and the engineers work to meet that spec. The Air Force didn't hand blueprints to Bell and asked them to make it.

Bell came up with ideas and put them on paper, but the AAF completely controlled (specified) everything about any plane that they purchased. They are the buyer, they got exactly what they wanted at the time.

Yes you would need new formers for the new tanks just like the tanks presently there. Should have been specified by the AFF long before production began.

Armament was adequate and a worthy tradeoff for the extra endurance. The P-51B/C only had 4 .50MGs.

 

[eagledad]

Room for more fuel outboard of the present tanks, and forward of the main spar the entire span except where the landing gear strut goes through the spar. Lots of room there. Yes that would call for the removal of the water injection tank and the .50MG. Remaining armament of one 37mm cannon and two .50MGs is plenty for shooting down LW interceptors.
There would be no water injection for WEP but, honestly WEP added 3mph to the top speed of the P-51D and 8mph to the P-38L. Less than 10mph for the chance to blow up your engine (over enemy territory) and piss off your crew chief for the extra work.
The weight saved by deleting the WEP water (200#) and .50MGs (350#) alone is the equivalent of 91 additional gallons for a total of 223 gallons internal for NO EXTRA WEIGHT. Probably room for more fuel than that. Plus three drop tanks.
And Bell engineers were clever but the configuration, fuel, armament etc was specified by the AAF. Bell had very little say in the matter.

P-39 Expert,

Am I mis-reading your statement, or are you implying that the 51D and 38L had water injection? I don't believe that either pilot manual mention that these aircraft had water injection. I know the 51H had the provisions, but the 38L and 51D?

Just curious.

Eagledad

 

[wuzak]

There would be no water injection for WEP but, honestly WEP added 3mph to the top speed of the P-51D and 8mph to the P-38L. Less than 10mph for the chance to blow up your engine (over enemy territory) and piss off your crew chief for the extra work.

The WEP top speed was at a lower altitude than the Military power top speed.

So while it was 3 or 4mph faster overall, it was achieved at a lower altitude.

In this report the P-51D had a top speed of 442mph @ 26,000ft WEP (3,000rpm, 67inHg MAP/+18psi boost), 438 @ 28,000ft Military Power (3,000rpm, 61inHg MAP/+15psi boost) and 420 mph @ 29,400ft Normal Rated Power (2,700rpm, 46inHg MAP/+8psi boost). These speeds were all at the critical altitude in high gear.*

But comparing speeds below critical altitude, the gain from Military to WEP was 12mph @ sea level, 16mph @ 10,000ft (low gear critical altitude), 11mph @ 20,000ft and 10mph @ 25,000ft.

Unfortunately that report only has WEP climb data, but I think you'll find that climb was improved significantly below critical altitude of WEP. But this report does.

Climb rates (ft/min):

Altitude      WEP       MP
Sea Level  3,410     3,030
7,500ft    3,510
9,700ft              3,170
21,200ft   2,680
23,200ft             2,300

Note that the climb rate and speed when using WEP will fall after critical altitude until they reach the same values as Military Power at the critical altitude of Military power. In WEP the change from Lo to Hi gears will also occur at a lower altitude.

* Altitudes seem high for a V-1650-7

 

[wuzak]

The gains in WEP for the P-63 are both more dramatic and underwhelming!

At 5,000ft WEP gives ~20mph gain over Military power. About 12mph @ 10,000ft, up to 18mph @ 15,000ft and about 4mph at 20,000ft. After which WEP is no advantage (actually, same rating as MP from then on).

http://www.wwiiaircraftperformance.org/P-63/42-78015.pdf

No climb data in that report.

 

[swampyankee]

Room for more fuel outboard of the present tanks, and forward of the main spar the entire span except where the landing gear strut goes through the spar. Lots of room there. Yes that would call for the removal of the water injection tank and the .50MG. Remaining armament of one 37mm cannon and two .50MGs is plenty for shooting down LW interceptors.
There would be no water injection for WEP but, honestly WEP added 3mph to the top speed of the P-51D and 8mph to the P-38L. Less than 10mph for the chance to blow up your engine (over enemy territory) and piss off your crew chief for the extra work.
The weight saved by deleting the WEP water (200#) and .50MGs (350#) alone is the equivalent of 91 additional gallons for a total of 223 gallons internal for NO EXTRA WEIGHT. Probably room for more fuel than that. Plus three drop tanks.
And Bell engineers were clever but the configuration, fuel, armament etc was specified by the AAF. Bell had very little say in the matter.

Water injection wasn't so much for speed as to increase rate of climb and improve energy retention.

 

[GregP]

Could also be that the end of P-40 production in Nov 44 was known at the time, and the decision was not so much to not go with the P-40Q in the P-40 production run as much as it was to terminate production of P-40s entirely. Now THAT is understandable. I am somewhat leaning toward the situation where the P-40Q, while interesting and a very good performer, was simply too late in the line of P-40s to be considered for production unless they rescinded the decision to terminate P-40 production. It is likely that the money to be spent for potential P-40s was already tied up in production contracts for other aircraft, negating any chances for the P-40Q.

That seems much more logical to me than the USAAF not recognizing the quantum leap in performance the P-40Q would have offered over the standard P-40 series.

Either way, though I am fond of the prototypes, they didn't make it, like so many other planes with good potential at first or any glance from many countries. C'est la vie.

Oh, and the P-40Q could compete quite well with the P-51D. It was slower by some 15 mph, which is nothing in combat, but could out-roll the P-51 easily, was likely more maneuverable, had very good climb, and most likely more forgiving handling in general. It DID fall short in range as an escort, but the P-40 was never an escort fighter to begin with. Notwithstanding, it wasn't selected and I would not say the reasons were wrong until I could actually see the real reasons enumerated, which isn't likely if we haven't seen it to date.

So, no argument for it other than it could definitely have been useful in almost any role the P-40 was actually used for.

 

[wuzak]

I am somewhat leaning toward the situation where the P-40Q, while interesting and a very good performer, was simply too late in the line of P-40s to be considered for production unless they rescinded the decision to terminate P-40 production. It is likely that the money to be spent for potential P-40s was already tied up in production contracts for other aircraft, negating any chances for the P-40Q.

The P-40Q was just too late, full stop.

 

[Dan Fahey]

The P-40Q was just too late, full stop.

P40Q was available and sorted out in early 1943.
CW do not want to stop Production to retool for the Q.

 

[P-39 Expert]

P-39 Expert,

Am I mis-reading your statement, or are you implying that the 51D and 38L had water injection? I don't believe that either pilot manual mention that these aircraft had water injection. I know the 51H had the provisions, but the 38L and 51D?

Just curious.

Eagledad

Didn't mean to confuse you, I was talking about deleting the water injection from the P-63 and replacing it with additional fuel and then saying how little WEP (War Emergency Power) added to the speed of the P-51D and P-38L at altitude. They didn't have water injection because they had an intercooler for WEP.

 

[P-39 Expert]

The WEP top speed was at a lower altitude than the Military power top speed.

So while it was 3 or 4mph faster overall, it was achieved at a lower altitude.

In this report the P-51D had a top speed of 442mph @ 26,000ft WEP (3,000rpm, 67inHg MAP/+18psi boost), 438 @ 28,000ft Military Power (3,000rpm, 61inHg MAP/+15psi boost) and 420 mph @ 29,400ft Normal Rated Power (2,700rpm, 46inHg MAP/+8psi boost). These speeds were all at the critical altitude in high gear.*

But comparing speeds below critical altitude, the gain from Military to WEP was 12mph @ sea level, 16mph @ 10,000ft (low gear critical altitude), 11mph @ 20,000ft and 10mph @ 25,000ft.

Unfortunately that report only has WEP climb data, but I think you'll find that climb was improved significantly below critical altitude of WEP. But this report does.

Climb rates (ft/min):

Altitude      WEP       MP
Sea Level  3,410     3,030
7,500ft    3,510
9,700ft              3,170
21,200ft   2,680
23,200ft             2,300

Note that the climb rate and speed when using WEP will fall after critical altitude until they reach the same values as Military Power at the critical altitude of Military power. In WEP the change from Lo to Hi gears will also occur at a lower altitude.

* Altitudes seem high for a V-1650-7

Right, WEP only helps performance below critical altitude. Purpose of the second stage was to increase critical altitude.

 

[drgondog]

P40Q was available and sorted out in early 1943.
CW do not want to stop Production to retool for the Q.

CW didn't have a contract to produce P-40Q. Had a contract been forthcoming from Material Command, CW would been delighted to invest in tooling.

AAF finally saw the light on the Merlin Mustang potential mid 1942, and orders for Hybrid NA-99 to NA-102/103 kicked in at end of Q3. The deliveries of the P-51B-1 started at approximately the timeframe that P-40Q was being tested and modified. At the end of 1942, substantiation from Mustang X and Spit IX high altitude promise, combined with unfiltered reports by pilots that flew the XP-51 and P-51-1 outside the Material Command domain made it pretty clear that the P-51B had far more potential than P-40Q.

Greg's comments about maneuverability advantage the P-40Q promised were sound, but range and speed at altitude were already fully confirmed with first flight tests of the P-51B-1-NA by Chilton in May 1943. At the take off Gross weight of 8600 pounds (closer to interceptor/fighter role with only 105 gallons of fuel) the speed attained was 450+ at 29K, with climb rate of 3800+ fpm at 12K at MP of 61. This was without racks, specially prepared wing with sanded finish and taped gun ports. The follow on test at WP on the 18th May states 'equipped as production fighter' but unclear re: Racks had 442 and 3600 fpm from SL to 13K (3520fpm) in Low Blower.

Notable is that the actual flight test performance achieved by Chilton and Army flight tests were Very close to the original Performance Estimates Report NA-5534 dated 10-19-1942, BEFORE the first flight of XP-51B #1.

When the P-40Q started testing, the P-51B-1 was already in serial production on a brand new line funded by A-36/P-51A contracts, the Dallas P-51 line was receiving plans and tooling to begin NA-103 P-51C.

Curtiss had a very spotty 'estimate to actual' record including P-36, P-40, XP-46 and XP-60 and speculatively had a much higher performance estimate for the P-40Q than revealed in flight tests?

As a War Plans and Requirements Division of Air Staff, why would you allocate Tooling and supply priorities to a fighter with less potential?

Summary, the P-40Q offered zero advantage over the P-51B-1 (save roll rate), and due to increasing delta in advantage of P-51B-1 at escort altitudes and above, combined with far greater range - why would Army buy the P-40Q?

 

[FLYBOYJ]

P40Q was available and sorted out in early 1943.
CW do not want to stop Production to retool for the Q.

That wasn't a CW decision - had CW been given a production contract they would have retooled in a New York minute!

CW didn't have a contract to produce P-40Q. Had a contract been forthcoming from Material Command, CW would been delighted to invest in tooling.

BINGO!

 

[P-39 Expert]

CW didn't have a contract to produce P-40Q. Had a contract been forthcoming from Material Command, CW would been delighted to invest in tooling.

AAF finally saw the light on the Merlin Mustang potential mid 1942, and orders for Hybrid NA-99 to NA-102/103 kicked in at end of Q3. The deliveries of the P-51B-1 started at approximately the timeframe that P-40Q was being tested and modified. At the end of 1942, substantiation from Mustang X and Spit IX high altitude promise, combined with unfiltered reports by pilots that flew the XP-51 and P-51-1 outside the Material Command domain made it pretty clear that the P-51B had far more potential than P-40Q.

Greg's comments about maneuverability advantage the P-40Q promised were sound, but range and speed at altitude were already fully confirmed with first flight tests of the P-51B-1-NA by Chilton in May 1943. At the take off Gross weight of 8600 pounds (closer to interceptor/fighter role with only 105 gallons of fuel) the speed attained was 450+ at 29K, with climb rate of 3800+ fpm at 12K at MP of 61. This was without racks, specially prepared wing with sanded finish and taped gun ports. The follow on test at WP on the 18th May states 'equipped as production fighter' but unclear re: Racks had 442 and 3600 fpm from SL to 13K (3520fpm) in Low Blower.

Notable is that the actual flight test performance achieved by Chilton and Army flight tests were Very close to the original Performance Estimates Report NA-5534 dated 10-19-1942, BEFORE the first flight of XP-51B #1.

When the P-40Q started testing, the P-51B-1 was already in serial production on a brand new line funded by A-36/P-51A contracts, the Dallas P-51 line was receiving plans and tooling to begin NA-103 P-51C.

Curtiss had a very spotty 'estimate to actual' record including P-36, P-40, XP-46 and XP-60 and speculatively had a much higher performance estimate for the P-40Q than revealed in flight tests?

As a War Plans and Requirements Division of Air Staff, why would you allocate Tooling and supply priorities to a fighter with less potential?

Summary, the P-40Q offered zero advantage over the P-51B-1 (save roll rate), and due to increasing delta in advantage of P-51B-1 at escort altitudes and above, combined with far greater range - why would Army buy the P-40Q?

The whole P-40Q question is based on serial production of the two stage Allison beginning in March 1943. Curtiss, Bell and NAA all knew that the two stage Allison was coming, being tested and would be in production in early '43. They all could (should) have started modifications necessary to adapt their planes (P-40, P-39 and P-51) to this engine to coincide with it's serial production. All three would have had excellent high altitude capability shortly thereafter in mid '43.

The P-40Q first flew in April '44, much too late to put into production. Air superiority had already been secured in Europe so there was no need. But the engine was available in production much sooner a little over a year earlier.

Really no reason to continue P-40 production unless it had a two stage engine. An Allison P-40 reached combat ceiling (1000fpm climb) at UNDER 20000' in clean condition (no drop tanks). With an external tank it was even lower. Every engagement with any Axis fighter normally resulted in the P-40 being attacked first from above. Not good. Either give it a two stage engine or quit wasting resources producing it.

Same with the P-38. It wasn't really a good plane until the ultimate J-25 and L got into production in June of '44. Air superiority had already been won. Much better to have high altitude single engined fighters at half the cost to build, maintain and operate.

 

[drgondog]

The whole P-40Q question is based on serial production of the two stage Allison beginning in March 1943. Curtiss, Bell and NAA all knew that the two stage Allison was coming, being tested and would be in production in early '43. They all could (should) have started modifications necessary to adapt their planes (P-40, P-39 and P-51) to this engine to coincide with it's serial production. All three would have had excellent high altitude capability shortly thereafter in mid '43.

Nope. More comments below. The V-1710-119 and -121 which appeared in the P-40Q, then XP-51J - did not operated to specs.

The P-40Q first flew in April '44, much too late to put into production. Air superiority had already been secured in Europe so there was no need. But the engine was available in production much sooner a little over a year earlier.

Nope. The Q-1 first flew in June 1943, was further modified and delivered to Eglin, Jan 1944. By that time more than 1400 P-51B-1, B-5 and C-1 had been delivered to AAF.

Really no reason to continue P-40 production unless it had a two stage engine. An Allison P-40 reached combat ceiling (1000fpm climb) at UNDER 20000' in clean condition (no drop tanks). With an external tank it was even lower. Every engagement with any Axis fighter normally resulted in the P-40 being attacked first from above. Not good. Either give it a two stage engine or quit wasting resources producing it.

By the time the P-40N was being tested at Eglin in June 1943 it proved to have a Service Ceiling of 38K. 1000 fpm is pretty arbitrary as a 'combat ceiling'.

Same with the P-38. It wasn't really a good plane until the ultimate J-25 and L got into production in June of '44. Air superiority had already been won. Much better to have high altitude single engined fighters at half the cost to build, maintain and operate.

The P-38H was a good airplane, didn't have the range r high altitude ETO reliability of the P-38J-15 or the roll capability of the J-25 - but they did just fine all the way through VE Day in the Far East and SW Pacific.

The P-40Q first flew in June 1943. The limitations including very low oxygen supply (2 3/4 hrs at 20K), no external wing rack capable of carrying either drop tanks or bombs of same weight, no internal space to add extra fuel tank, limited capability to pressurize tanks without modification, 20-30mph slower than Production P-51B with much better performance using an engine that was in full production (1650-3) rather than development stage (V-1710-119) and -121).

The same engine was installed on the XP-51J and first flown April, 1945 - with a pot load of engine issues that were never solved by Allison for boost above 61-63" MP. The experience was so bad that NAA abandoned testing with less than 10 hours and sent it to Wright Patterson.

 

[michael rauls]

This whole " why didn't the p38 do well in Europe" narrative is so frustrating with even the defenders of the p38 accepting the premise. First off by way of comparison wich p38,p47,or p51 and in what time frame are we talking about? Say 42 to 43 or 44,45? If we're talking42,43, yes the p38 had shortcomings but it was the only one of the 3 major fighter types that could even get to the fight much of the time. The 47 didn't have the range and the alison engine 51s were usless abouve20,000 feet. And in spite of there shortcomings bomber losses plunged when p38s began escort. If were talking 44,45 then its a much closer comparison but p38s were therein limited numbers(the 474th used them till the end) and they achieved just shy of a 5 to 1 kill ratio durring this time. Now i would subbmit that a 5 to 1 kill ratio achieved while flying low and slow ladden with ordinance(the38s ussual mission profile during this time) vs the p51s 7 or 8to 1 kill ratio(depending whos numbers you use) while flying unladden at high altitude out ahead of the bombers where the could often have a tactical advantage is at least compatible if not better when the comparative mission profiles are taken into account. So in my mind and I would think the mind of anyone who looks at it objectively the p38 has NOTHING to apologize for its performance in the European theater. All that being said if I were marking the decisions I would have gone largely with the p51 also just because half the cost,just as effective.

 

[P-39 Expert]

The P-40Q first flew in June 1943. The limitations including very low oxygen supply (2 3/4 hrs at 20K), no external wing rack capable of carrying either drop tanks or bombs of same weight, no internal space to add extra fuel tank, limited capability to pressurize tanks without modification, 20-30mph slower than Production P-51B with much better performance using an engine that was in full production (1650-3) rather than development stage (V-1710-119) and -121).

The same engine was installed on the XP-51J and first flown April, 1945 - with a pot load of engine issues that were never solved by Allison for boost above 61-63" MP. The experience was so bad that NAA abandoned testing with less than 10 hours and sent it to Wright Patterson.

The P-40Q first flew in June 1943. The limitations including very low oxygen supply (2 3/4 hrs at 20K), no external wing rack capable of carrying either drop tanks or bombs of same weight, no internal space to add extra fuel tank, limited capability to pressurize tanks without modification, 20-30mph slower than Production P-51B with much better performance using an engine that was in full production (1650-3) rather than development stage (V-1710-119) and -121).

The same engine was installed on the XP-51J and first flown April, 1945 - with a pot load of engine issues that were never solved by Allison for boost above 61-63" MP. The experience was so bad that NAA abandoned testing with less than 10 hours and sent it to Wright Patterson.

I'm talking about the -93 that went into the P-63. It was in series production from March '43 with over 2500 built. You are talking about the -101 that began TESTING in July 1943 and first flew in the P-40Q in November '43. Neither it nor the follow on -121 saw production.