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

[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-40N you mentioned was the "ultralight" version with reduced armament, fuel and the new aluminum radiators. Only 400 built before reverting back to the full load in the N-5. Performance fell back to 350mph and 31000' ceiling. Not very competitive.

 

[GregP]

I have long wondered how a P-40Q with a 2-Stage Merlin would have performed, but have not invested any time in thinking about the details because they never built one even when the engine was available for experimentation. It would probably have been VERY competitive with the P-51B, which was already in serial production ... and, again, would likely not have been selected for production due to existing production of the P-51B.

The only way I can see the P-40Q with a 2-stage Merlin maybe being produced is if the plane were to be available at almost the same time as the XP-51B was. And, while it MIGHT have been possible, it never happened in real life, even when the 2-stage Merlin were available. Had it been available to Curtiss significantly sooner, and had they acted upon it, Curtiss might have gotten an order for some P-40Qs.

It's an interesting "what-if" that didn't happen and would not happen unless the timeline were to be significantly altered to favor Curtiss, and if they were smart enough to pursue it.

That we were "saddled" with the P-51 instead might be one of the best instances of serendipity ever to occur along with the private venture Spitfire working out so well for the British. We didn't "want" the P-51, but were forced to both acknowledge and accept its performance when we tested it. It certainly wasn't exactly perfect. But if it wasn't, it was as close as we ever got, aside from maybe the F-86 somewhat later.

 

[Dan Fahey]

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?

CW chose not to ask USAAF to manufacture the Q. They could have replaced the N version with the Q. The engine was available for the P63 and P51j. Q had better flight performance over all coupled with higher altitude performance CW imho became a Greedy manufacture. It would have saved lives. Example, The F87 was the last straw with the now DOD. After that CW was asset stripped by greedy investors. Second most profitable Defense contractor during WW2. Today CW is a speciality DOD contacting company.

The US failed to introduce the P63 to USAAF which would have been a far better Ground attack and fighter plane than any of the current fighters. For the same reason the P51 almost got ingnored. The NIH issue came up. Like the P40 and whole new design P51 because the calaboration of two engineering groups the P63 suffered the same fate.

 

[BiffF15]

Gents,

Those of you with a God's eye view of timelines answer me this. Was there some overt point at which the USAAF started picking winners and losers for upgrades and then actually stopped major upgrades? Example is the P72, P38K, P40Q? The P51 was getting the H, the P47 was getting the N and jets were on the horizon. I understand the P38K "might" have been not warranted for the threat (or lack thereof) faced in Asia and losses of new production aircraft during the transition (single production line drawback).

Cheers,
Biff

 

[Shortround6]

There seems to be a bit of confusion as to when the P-40Q was actually "ready."
They had 3 airframes and some of the airframes went through several different models of engines,

One report is dated from Nov of 1943 and that test is of the first XP-40Q serial number AC-9987. This plane started out as a P-40K .
The engine used was the V-1710-101 (F-27). No performance figures are given in the report. The performance figures most people seem to be quoting are from an
April 1944 report/test which had a different airframe and a different engine.
I would also note that P-40 production for 1944, even in the first part of 1944 (production stopped in Nov) was roughly 1/2 the number per month that it had been in 1943. Granted it probably could have been sped back up if really needed but the P-40 was seen as no longer needed or desirable before Jan of 1944.

In the Summer of 1943 this is what you had for a XP-40Q

From :Curtiss XP-40Q Fighter

For a good timeline/description of evolution.
The P-40Q was simply too late in timing.

 

[Navalwarrior]

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.

Resp:
The only theater where the P-38 performed poorly, if I can say that, was the ETO. If you were in the AAF in any other theater before Jan 1944, what was better than the P-38? The P-47N didn't make it until 1945. So there was the P-39, P-40 and P-38 (few P-47s in PTO/CBI). All of the fighters evolved, with most getting better. As for the Allison contract, think about how many fighters were already needing engines ( don't forget replacements in the field)? Not sure they could supply the Allisons need for another fighter. Just think out loud.

 

[GregP]

I think we've all agreed about the "too late."

Once the performance of the P-51B was known, the only real reason to produce the P-40Q would have been if the P-51B failed. And ... the P-40Q could have addressed most missions of the P-51B, but not long range escort, so ... the P-51B seems like the only game in town for that particular mission at the time.

They would have invested a lot of bucks in P-51B to make it work before trying out the P-40Q. As it happened, they didn't need to do that since it basically worked right off the drawing board. In retrospect, it does seem like North American had a very good set of shoulders upon which to rest their fortune and Curtiss had great difficulty producing a plane that performed better than the standard P-40.

 

[P-39 Expert]

Resp:
The only theater where the P-38 performed poorly, if I can say that, was the ETO. If you were in the AAF in any other theater before Jan 1944, what was better than the P-38? The P-47N didn't make it until 1945. So there was the P-39, P-40 and P-38 (few P-47s in PTO/CBI). All of the fighters evolved, with most getting better. As for the Allison contract, think about how many fighters were already needing engines ( don't forget replacements in the field)? Not sure they could supply the Allisons need for another fighter. Just think out loud.

The competition was a lot better in Europe. In the PTO the Lightning had the speed and climb advantage. In the ETO their speed and climb was just barely able to keep up but the low Mach number and less maneuverability hurt them. And of course the cost to maintain a twin.

 

[swampyankee]

The competition was a lot better in Europe. In the PTO the Lightning had the speed and climb advantage. In the ETO their speed and climb was just barely able to keep up but the low Mach number and less maneuverability hurt them. And of course the cost to maintain a twin.

I'm not sure "the competition was a lot better in Europe"; although the competion was a lot higher. There were several aircraft that did much better in Europe than against Japan.

The design defects in the early variants of the P-38, in its induction system, ergonomics, and nimbleness, mostly roll acceleration, and defects in pilot training were all contributory. By the time those were sorted, better aircraft were coming on line.

 

[drgondog]

CW chose not to ask USAAF to manufacture the Q. They could have replaced the N version with the Q. The engine was available for the P63 and P51j. Q had better flight performance over all coupled with higher altitude performance CW imho became a Greedy manufacture. It would have saved lives. Example, The F87 was the last straw with the now DOD. After that CW was asset stripped by greedy investors. Second most profitable Defense contractor during WW2. Today CW is a speciality DOD contacting company.

The US failed to introduce the P63 to USAAF which would have been a far better Ground attack and fighter plane than any of the current fighters. For the same reason the P51 almost got ingnored. The NIH issue came up. Like the P40 and whole new design P51 because the calaboration of two engineering groups the P63 suffered the same fate.

CW hardly chose 'not to ask' for a contract to manufacture the Q. They were already looking at the end of the P-40N line with no follow on. They had failed to bring the XP-46 and XP-60 to successful achievement of promised performance, leaving their strong supporters (Echols) holding the bag as airframe after airframe specified by Material Command failed. They were staring into the abyss.

The biggest blunder of Material Command, namely the XP-75 - was already being deemed dangerous to fly by Ben Bradley, the then current Fighter Projects Director. Material Command at that time had lost a lot of stroke with AAF in context of selecting 'winners' and they were tagged by that time with a.) being advocates of failed CW proposals, and b.) open obstructors to NAA at the expense of war fighting capability.

The XP-51F with Performance estimates of Far superior capability to even the P-51B was well along on the engineering side as USAAF Next Gen along with P-47M with all Republic manufacturing capability poised to produce them. It would have taken pretty dumb AAF decision makers to select P-40Q for any mission other than replace P-40s for Commonwealth/Allies.

The P-63 was deemed superior to the P-39 and P-40 but not superior to P-51B and only the Russians were interested in it. It was not remotely close to P-47D/P-38H/J or P-51B contemporaries in combined CAS and escort flexibility.

Same basic issue as P-40Q - no well defined mission (AAF) urgent enough to ramp up Logistics supply chain to introduce yet another new airframe and engine into the mix. By that time the Planners were well acquainted with requirement for range to maximize tactical footprint over the battlefield. .

The fighters in serial production were better than the P-40Q. The Military Requirements Division had zero critical mission (CAS, Interceptor, Escort) for which the P-40Q was superior to the P-47D/P-51B, the P-38H/J or P-51B, the P-38H/J and P-51B respectively.

The P-40Q had less range than the P-51A on pure internal fuel and had no provision for external stores, especially combat tanks. It could outclimb the P-51A and out roll it - but so what if it was being compared to the P-51B?

Last point, really a question? How do you assign corporate Greed to the failure to select P-40Q, when the P-40 was basically dead for AAF future plans?

 

[Peter Gunn]

I will say this, the P-40AQ in SR6's post #305 is one sleek looking ship. I like it better than the bubble top version, but only for aesthetic purposes, I am partial to all the razor backs.

 

[GregP]

Well said, Bill. The fact that I really like the P-40Q with the bubble canopy does nothing to change your succinct summary. Had they installed a 2-stage Merlin, it might have been better at some things than a P-51, but range alone would preclude it from ever replacing the P-51, even IF P-40Q performance with a Merlin proved to be better then the P-51 and, without analysis, that is highly doubtful to start with.

I had not brought up the rather pedestrian XP-46 and XP-60 series (I do like the XP-60E alone in the series), but when you did, it more or less drives the nail in the coffin.

Maybe we can put this one to bed.

 

[Bad-Karma]

I will say this, the P-40AQ in SR6's post #305 is one sleek looking ship. I like it better than the bubble top version, but only for aesthetic purposes, I am partial to all the razor backs.

Finally a post I'm qualified to weigh in on

To heck with the performance numbers they should have stopped at N based on looks alone! Possibly even E !

 

[FLYBOYJ]

Curtiss XP-40Q Fighter

 

[Schweik]

Well, range and the fact that they KNEW the P-40 couldn't compete with the 109s on even terms. Even using P-40Fs. They did use hundred of P-40s in that theater along with P-39s. The P-38s flew top cover for the tactical bombers (B-25/B-26s) and the lower altitude fighters.

The P-40s could hold their own but only at the lower altitudes, which is no way to win a campaign. It only works IF your enemy co-operates and flies were your aircraft are the strongest.

Actually not true. The P-38s rarely flew top cover for P-40s - they used P-40Fs for that because of their higher performance ceiling (about ~20k feet) and Spit Vs (both RAF and American) when the range allowed.

The five USAAF P-40 fighter groups (almost all flying P-40F or L) all had good records against the Luftwaffe and Regia Aeronautica. Most had 3-1 or better on claims, which translated to slightly better than 1-1 in actual combat when you look at the German records. The best (57th FG and 325FG) did a little better than that, apparently - though the numbers aren't all published yet. There were 18 USAAF Aces flying P-40s in the Med.

There are a few reasons for this not necessarily attributable to the aircraft type - unlike the RAF the USAAF squadrons were using 'finger four' formations with wingmen, they had better radios, they were attacking the German bases and thus often facing German fighters forced to come up from below at least some of the time, they did not use 'defensive circles', and so on. And the P-40F / L could still fight well up to 20,000 feet vs. 12-15,000 feet for the Allison engined models that the RAF / Commonwealth were (mostly) using).

P-38s didn't do all that well in North Africa and after a few bad days operating and medium to low altitude, they specialized in escorting the heavy bombers, mainly B-24s of which there were a lot in Theater, sometimes B-17s, at high altitude. If you look at Shores Mediterranean Air War Vol III, you'll see that most of the P-38 missions were of this type, often in long range strikes. Sometimes they were also used in Maritime patrol.

P-38 squadrons had a lot of bad days in the Med including one squadron flying in on a ferry mission (with only 50 rounds of .5 ammo loaded and no 20mm) being shot down by some Ju 88s.

S

 

[Schweik]

I think Bungey (His book "Most Dangerous Enemy") pretty much has debunked that common mythology. Only one airfield (Manston) was ever put out of operation. Virtually no planes were caught on the ground. The radars were hard to take out, only a Stuka might do it and they were easy prey, and the RAF had redundancy and mobile radars and quick repairs. The Luftwaffe tried that for weeks and got nowhere, except large losses.

The Germans attacking London was a last resort because nothing else had worked, the RAF just kept inflicting unacceptable losses. The Germans had worse problems getting new pilots and they didn't have the production of the British to replace machine losses.

Only if they had hit Sector stations and took out the controllers could they have done it...and they didn't know they existed, their importance or where they were.

They needed a quick victory (to enable an invasion), so they depended on the RAF being stupid. That is put up all their fighters in the air so that the Luftwaffe experten could shoot them down at a 5:1 ratio (as if) or get their planes caught on the ground. Neither of these things happened, Park tactically managed his forces beautifully.

Oh yes the RAF was under pressure all right, but so was the Luftwaffe. Neither side really knew how the other one was suffering. The Luftwaffe fell prey to over confidence, the RAF, correctly, remained very conservative. Even at the worst point, when Dowding broke up squadrons (allocated as A, B C categories) Fighter Command actually had more pilots than at the beginning of the Battle (don't forget the huge losses they suffered in France which had to made good). They were under establishment (ie theoretical) strength, but they still had plenty...plus reserves, which the Luftwaffe didn't.

And the Luftwaffe newbies were just as bad as the RAF ones, ie cannon fodder.

So the BoB would still have turned out the way it did, even if the Luftwaffe had kept on at the airfields (etc) and never touched London.

The Luftwaffe were not stupid they also tried very hard to take out aircraft production...and like Bomber Command and the USAAF did later, failed, despite the fact that (at that time) the Supermarine and Hawker production were well within 109 escort range (closer than London).

So we are back to inaccurate bombing again, which had little effect, so the bombers were just the reason to get the RAF up so they could be shot down. Trouble was, FC (after France) had a hard core of experienced pilots ..and, which they could never understand (and didn't understand later in '43 and '44) the concept of a 'General' maintaining effective tactical control over his forces.

You have to remember the Heer (Army part of the Wehrmacht) training, leadership, doctrine, etc (such as Mission Command) was all worked out before the Nazis took over. It was a master of 3rd Generation warfare. Hence why it was so good.. and took the combined forces of the USSR, UK and US to beat them.

The Luftwaffe was created by the Nazis. Hence it's doctrine and ethos were very different. Full of the 'warrior hero' nonsense. Technology, logistics, tactics, were secondary to 'will power' and all that piffle. Hence things like Galland not wanting radios in fighters in the BoB, pilots never getting breaks (while their soldier brothers were far better looked after). Marseille feted, who slaughtered huge numbers of Hurricanes and P-40s...and shot down only 4 bombers in his entire career (leaving his soldier brothers to get hammered by the DAF while he got the headlines...dickhead).

Galland, even at the end, still couldn't except tight effective tactical ground control. To him the pilots in the air were the 'kings'...and then repeated the mistakes of Leigh Mallory in France in '41...the same which mistakes he benefited from in getting his 'score' (and medals).

So it was a weird and very disfunctional organisation, the most effective leader of it all was Kesselring, a very (prior and later) good ground general..who got thumped twice by Park.

Park was like Monty, a really good General who knew his stuff inside out. He knew what he wanted to achieve, he learned, he taught, he changed things. He out thought the enemy at all points...he denied them of what they wanted. He never risked too much at any point in time, hence his opposition to (along with many other reasons) the 'big wing stuff. He understood that air warfare was 3 dimensional and that timing, position and surprise were more important than just raw numbers. 4 planes at the right time and place with the advantage of position and surprise can create more damage than 200 at a tactical disadvantage.

And he cared about his pilots. When the Luftwaffe was hitting the RAF's airfields (many not Fighter Command) his jumped up and down, not because the airfield's were out of operation ..they weren't (Spits and Hurris all took of in grass) but because the pilots didn't have a bed and food and so on. Unlike Leigh Mallory, Park got in his Hurricane and went all round his airfields and talked to his people regularly.

A true leader.

The Luftwaffe, unlike the Heer who produced many of them, was incapable of producing and using people like Park...hence they lost.

Though the RAF (overall) wasn't much better in may ways since it fired Park and Dowding real fast after the BoB.....took until the DAF to get it back being useful again.... 70% losses in Bomber Command (50% killed)? Which was the same the Luftwaffe overall suffered, as did the U-Boats.... Ideology (idiotology?) achieves nothing just gets people killed for nothing.

I think this is a pretty good analysis. The LW pilots interview excerpts in Shores MAW emphasize the frustration with the 'cult of personality' of the Experten and the kind of 'uber' mentality which, as a Strategy, promoted the kill scores of the experten, with the other pilots in the Stafflen reduced to protecting the star.

More seriously though was, as you mentioned, the emphasis on attacking fighters, or seeking out fights which would benefit the kill scores as opposed to preventing their troops from being bombed, let alone providing effective CAS for the Afrika Korps. This caused serious tension between the ground commanders including Rommel, and the Luftwaffe leadership. There was also apparently significant tension between the Italian and German fighter units.

The LW units, especially JG 27, went out of their way to find easy targets - especially low flying fighter bombers, and would concentrate their activities in those areas where they found 'easy pickings', rather than wherever the DAF was doing the most damage. The DAF, in turn, basically ignored the LW attacks for far too long, concentrating on their main mission of providing effective CAS and protecting their own ground forces from Stukas.

DAF were thus providing pretty effective CAS but were quite late in adapting to LW tactics - leading to serious morale problems among other issues. And I think it was really the arrival of the Americans, despite their inexperience, which tipped the balance back in the Allied favor decisively, though of course Spitfires helped a lot too. The USAAF were using better tactics and took the fight to the LW by attacking their airfields, as a conscious shift in strategy by the US FG commanders like Bill Momyer. This put a lot more pressure on JG 27 which 'broke' and had to be sent away for a while for R&R. JG 77 didn't do as well and was suffering casualties literally from the day they arrived (when they lost one of their squadron leaders).

S

 

[wuzak]

unlike the RAF the USAAF squadrons were using 'finger four' formations with wingmen, they had better radios

Really? The RAF were still using Vic formations in 1942/43?

And the USAAF had better radios than the RAF?

 

[Schweik]

Really? The RAF were still using Vic formations in 1942/43?

And the USAAF had better radios than the RAF?

yes and yes. RAF was just starting to use finger four / two pairs in late 1942. Up until then they were using Vics and 'weavers', 'fluid pairs' and various other formations all of which proved easy pickings for the Germans. Numerous Luftwaffe pilots quoted in MAW commented on this and how easy it made it for them. The RAF also habitually formed 'defensive circles' when attacked from above by Axis planes. Tactics started to change about the time the Americans showed up, a couple of the Experten interviewed said they didn't see proper formations until they faced the Americans - but I think this just means the 'finger four'. The tactic also changed into turning into the enemy attacks and making a head on pass.

Roughly the same situation with the radios. Per Bobby Gibbes and some others, the original radios were HF (UHF?) and required constant fiddling with the knobs to stay in tune. According to Gibbes, many died while trying to tune in their radios, oblivious to the frantic warnings being called out by their squad-mates. US planes came with "VF" (VHF?) radios which, per Gibbes and some others, stayed in tune much longer and changed channel via a button.

Everything started to change for the better for the Allies around the fall of 1942

S

 

[Schweik]

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 didn't get the green light for three reasons:

1) Multiple prototype accidents. Never a good sign.
2) P-51 was already looking good and production ready to take off
3) War Dept, Air Force and the government in general were sick of Curtiss Aircraft.

I think 3 is actually the most important reason. Curtiss was just screwing up right and left, they hadn't improved the P-40 nearly enough, the other P-40 replacements (P-46 and P-60 etc.) were failures (and looked like crap!) and numerous other aircraft they had produced turned out to be very expensive debacles. The Helldiver and the Seamew were epic fails. Experiments like the C-76 and the XP-55 failed. Their best designers had left after 1942, and even the P-40 run was having some production quality problems. The only planes they made even partly successful after the mid-war were the C-46 and the Seahawk and neither was critical to the war effort.

Curtiss as a company was just corrupt and bloated and incapable of delivering what was needed.

The P-40Q did look promising and may have been better in some respects than a P-51 but it would have meant taking a gamble on a once great company that had let them down time and time again. North American by contrast had a much better record both in terms of design and production.

S

 

[Schweik]

The P-40N you mentioned was the "ultralight" version with reduced armament, fuel and the new aluminum radiators. Only 400 built before reverting back to the full load in the N-5. Performance fell back to 350mph and 31000' ceiling. Not very competitive.

Actually they went back and forth, they had other N "interceptor" subvariants with the 4 gun armament and higher-rated engines (the short run N-10-CU for example - made for the Russians, and the final N-40 variant which had metal ailerons and a V-1710-115), couple of other variants that were even slower intended purely for training or FB work (most of the N-20 and N-30).

Some things were usually put back in to even the first 'stripped' N like the starter and battery but they kept a lot of the other weight savings (obviously the lighter radiator and wheels). The N types used by the RAF in Italy and 23rd, 51st and 80th FG in CBI could be configured various ways by taking out or adding gear. For fighting over 'The Hump' (Himalayas) they typically kept a lot of the weight savings including often removing two guns. They did the same with P-40K and M.

When fighting at lower alt over battling land armies further East they put the extra gun back in.

S