The Curtiss XP-40Q; When a Mustang and a Warhawk love each other very much…

September 27, 2023

For the giant Curtiss-Wright aircraft company, the Second World War was very much their heyday. Even before the war in Europe broke out in 1939, Curtiss were supplying CW-21 fighters to the Chinese and P-36 Hawks to France. But it was with the P-40, dubbed the “Warhawk” in US service, that the company’s greatest contribution to the Allied war effort was arguably made.

With 13,738 of these fighters built, the P-40 was the ninth most-produced fighter of the conflict, surpassing the Vought Corsair and only beaten in numbers produced by only a couple of thousand or so of the more famous P-47 and P-51. Which, OK, is a not insignificant amount but does demonstrate that the P-40 was a critical aircraft throughout the war.

Which is funny because the P-40 wasn’t all that good.

Actually, that’s not completely fair, it would be better to say that the P-40 was good enough to remain useful throughout the war, and certainly capable of holding its own when flown by a competent pilot who was fully versed with the aircraft’s strengths and weaknesses. It certainly had attributes that suited it to the rigours of combat, being tough, hard hitting and a good attack aircraft as well as low-level fighter.

But the fact that the P-40 was always a marginal performer in air combat, as said needing a very careful comprehension of its strengths and weaknesses to enable it to be used successfully against contemporary enemy fighters, mean that it is still subject to debate today, with one side holding that it was a very marginal aircraft and the other that it is, in fact, greatly underappreciated.

In essence, though the Warhawk was an aircraft that was able to be adapted to changing circumstance and technology so as to remain useful – they wouldn’t have built so many of them if it hadn’t been – but which was an aging design that was replaced by later fighters as soon as feasible. It was, after all, basically an adaption of the even older P-36 Hawk fighter, a design with its roots in the mid-1930’s.

And though Curtiss-Wright were happy to build as many P-40’s as they could, they also knew this. In fact, even before the war had begun they had been planning a successor aircraft, the P-46. Indeed, throughout the war Curtiss’ aircraft development efforts were marked by a distinct lack of progress, evidence that the company was falling further and further behind in the field against rival manufacturers. This meant that their main success was in keeping improved models of the P-40 rolling off the production lines; as said more an exercise in good enough now beating better later…but in this case better was looming on the horizon in the shape of the Thunderbolt and Mustang.

In 1943 it was obvious that these two aircraft were going to become the mainstay of the United States Army Air Force (USAAF) and that the P-40 was going to find itself swiftly relegated to subsidiary theatres and duties as the more formidable new fighters came on strength. With no new designs on hand that could match these rivals, Curtiss did what had proven successful before.

They offered an even more improved version of the Warhawk; the P-40Q.

These aircraft were all built on damaged examples of earlier P-40’s that were modified to see if further improvements could be made to the basic P-40 that would allow the fighter to continue to remain a front-rank competitor. Considering that this policy had essentially been Curtiss’ strategy since the P-36, it wasn’t entirely unreasonable, and if comparatively minor changes could produce better combat performance with minimal disruption to existing production lines then the idea was eminently sensible.

The first P-40Q, the Q-1, was a comparatively straightforward conversion of a P-40K-10 that was damaged in a landing accident in January 1943.

This had the nose lengthened in order to accommodate an Allison V-1710-101 engine, with the P-40’s iconic air-cooled radiator and oil coolers being moved to a mid-wing position beneath the fuselage, while the engine air intake was above the nose. Allied was this was a four-bladed propeller and an armament of four 0.5-calibre Browning heavy machine guns; features that were standard across the P-40Q’s.

Flight testing began in June 1943, but Curtiss evidently felt they could do better, and the aircraft was then subjected to a much more thorough rebuild, becoming the P-40Q-2.

This saw the aircraft have the oil cooler and air intake once again returned to under the nose, though in a much slimmer configuration than standard P-40’s, while the radiators were moved to the wings. Perhaps most notable in appearance change was the fitting of a bubble canopy for much improved pilot visibility.

Flight testing began in January 1944 and, with an even more powerful V-1710-121 engine fitted that produced 1,800hp with water injection at 20,000 feet, the Q-2 recorded a top speed of 422 mph (679 km/h) at 20,500 ft (6,248 m). Test pilots reported it was the best P-40 flying and interest was enough for additional development work to be authorized.

Unfortunately, the P-40Q-2 was damaged in accidents during the testing and focus switched to the next model, the P-40Q-2A.

This had originally been a P-40K-1 and was in contrast to the earlier aircraft kept largely unpainted in natural metal finish.

First flying in March 1944, the Q-2A had many of the features of its predecessor, including clipped wings that had been added later to the Q-2. These, along with the bubble canopy, gave the aircraft a rather P-51ish look, though it’s important to note that the wings on the P-40Q were the original P-40 thickness and not laminar-types as used on the Mustang.

Further changes between the Q-2 and -2A were the addition of automatic cooling shutters for the inner wing intakes.

Flight testing showed performance to be broadly comparable to the Q-2, but the Allison engine proved extremely problematic and the Q-2A spent a great amount of time being repaired instead of undergoing testing.

Attention then briefly switched to another version was also ordered in early 1944, the P-40Q-3, which was built off a P-40N.

Once again this had the V-1710-121 engine and was essentially the same as the previous Q-2s except the canopy was slightly modified to give a lower profile and with the front windscreen being much flatter and more steeply angled.

The Q-3 also experienced engine problems and was damaged soon after delivery for testing in April 1944, meaning that very little data seems to have been recorded and it assumably was similar enough to the Q-2’s in performance that no real effort was made at repairing it for further examination.

Because despite the improved performance over the baseline P-40, the P-40Q’s still didn’t offer anything over the P-51 and P-47, which were themselves becoming more and more formidable and getting into service in mounting numbers. Indeed, the Warhawk’s days in production were now numbered, and the last one rolled off the line in November 1944.

And that would be that for the P-40Q’s story, except there was one still in existence at the end of the war; the P-40Q-2A. This aircraft was declared surplus to requirements and after the war it was purchased by one Joe Ziegler and entered in the 1947 Thompson Trophy Race.

To be honest, with its clean lines, hugely powerful engine and comparatively low flying hours, the P-40Q-2A must’ve seemed like a good prospect for a high-speed, low-level racer.

Unfortunately, the reliability issues with the engine struck once again and during the race the whole thing caught fire. Ziegler had to bail out, fortunately only suffering a broken leg, but the aircraft was lost, marking the final end of the P-40Q’s; the ultimate examples of the legendary Warhawk.

 

Sources/Related:

https://oldmachinepress.com/2015/08/18/curtiss-xp-40q/

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