Military, WW2

XP-40Q – The Super P-40 Warhawk

The XP-40Q was a last ditch attempt by Curtiss to bring the P-40 Warhawk on par with the newest fighters, such as the P-51 Mustang and P-47. It was hoped that such a machine could reverse the downward trending path the company was experiencing.

The P-40’s wings were clipped, a new engine was fitted, and the pilot was given a bubble canopy, completely transforming the aircraft, both visually and performance-wise.

But was this enough?


Origin of the XP-40Q

The XP-40Q’s origins can be traced back to Curtiss’ attempt to produce a modern aircraft that would be produced in large numbers.

This continuous improvement in aircraft performance, driven by the escalating demands of the Second World War, had quickly reduced the P-40’s usefulness.

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The Curtiss P-40 Warhawk had been a mainstay in the air forces of several Allied nations, known for its ruggedness and reliability. However, by the mid-war period, it was becoming increasingly outclassed by both enemy and friendly fighters.

P-40 in flight.
The P-40 itself was based on a mid-1930s aircraft. However it served until the very end of the Second World War.

The P-51 Mustang in particular, arriving in 1942, was a serious competitor right out the gate. The gap between the two would only increase as the Mustang was upgraded. This was to be expected though, as the Mustang was originally developed as a better alternative to the P-40.

The Curtiss-Wright Corporation, aware of the P-40’s limitations and the rapid advancements in the field, initiated a project in 1943 to upgrade the Warhawk, leading to the development of the XP-40Q series.

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This series was essentially an experimental endeavor that saw how far the P-40 design could be pushed, with most major areas of the airframe being upgraded.

XP-40N with bubble canopy.
Various attempts had been made to improve the P-40. The unofficially named “XP-40N”, shown here, featured a bubble canopy.

The XP-40Q-2A was the culmination of these efforts, incorporating a range of modifications aimed at addressing the shortcomings of earlier models and making the Warhawk competitive with contemporary aircraft.

The original P-40 was developed in the late 1930s, and was a low-mono wing, all metal fighter. At the front was a 1,200 hp Allison V-1710 V12 engine driving a 3-bladed propeller. With this arrangement, the P-40 was only able to reach a top speed of around 360 mph and an altitude of 30,000 ft.

With the XP-40Q, Curtiss aimed to improve on these capabilities.

Allison V-1710 V12.
The 1,710 cu in (28 litre) Allison V-1710 V12 engine, used in most P-40s.

Design Features of the XP-40Q

The XP-40Q was majorly overhauled in comparison with the standard P-40. XP-40Qs were created from damaged aircraft that were no longer suitable for combat.

One of the most notable changes was the installation of a more powerful version of the V-1710 engine, equipped with a two-stage supercharger to boost its power output from 1,200 hp to 1,500 hp.

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This engine was housed in a redesigned, lengthened cowling and paired with a new four-bladed propeller. The machine gun quantity was reduced, from six .50 caliber guns in the P-40, to four in the XP-40Q.

XP-40Q on the ground.
The first XP-40Q. Note the extended nose and four-bladed propeller.

This aircraft first flew in June 1943.

It still retained the greenhouse canopy from the standard P-40 though. By this point, bubble canopies were a much superior design choice as they offered vastly greater visibility to the pilot.

The XP-40Q-2, arriving by the end of 1943, changed that, now featuring a bubble canopy on top of the fuselage.

The XP-40Q-2 also had a shortened rear fuselage, and the air intake was returned to under the nose. The engine’s radiators were moved to wings’ leading edges.

XP-40Q-2 in flight.
The XP-40Q-2 with its bubble canopy nose and clipped wings.

Power was increased too, with the V-1710 now producing a very impressive 1,800 hp with the addition of water injection. Once again, a four bladed propeller was used.

The modifications were so major that just by looking at the XP-40Q-2, it is hard to believe this machine was a P-40 underneath.

Its performance numbers were also hard to believe. During tests, which began in early 1944, the XP-40Q-2 was capable of reaching an 422 mph! This is an incredible achievement when compared to the standard P-40’s top speed of 360 mph.

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Without water injection, it topped out at 407 mph – still a healthy number.

During its testing period, the XP-40Q-2’s wing tips were clipped, visually becoming a “P-51 from Wish”. Unfortunately this example was damaged during evaluations, so a third version was ordered.

XP-40Q-2A in flight.
XP-40Q-2A. This version was left in a bare metal finish.

This modification, known as the XP-40Q-2A, was mostly the same as the previous version, however it suffered from quite severe reliability issues and minimal testing was carried out.

As a result, Curtis began the construction of a forth, and final, XP-40Q, the XP-40Q-3.

This attempt was, again, mostly the same as the previous two, with the same engine, clipped wings, and a bubble canopy. On this aircraft though, the bubble canopy was slightly lower and more in proportion, having come from another project.

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The XP-40Q-3 was ready for testing in April 1944, but it also ran into issues and was damaged during a landing.

XP-40Q-3 side view.
The XP-40Q-3. Note the more streamlined canopy.

Cancellation and Racing Career

Despite the promise shown in its design and performance improvements, the XP-40Q never entered service.

By the time the XP-40Q was ready for evaluation, the landscape of aerial combat had shifted significantly. By this point, the USAAF was coping perfectly well with the P-51 and P-47, and there was no need for an aircraft that was at its limits just trying to keep up.

When in the air, the XP-40Q-2 and onwards were described as very agile, fast machines. One pilot even stated that it was the best performing version of the P-40. It possessed much greater speed than the P-40, and was significantly faster climbing and more agile.

XP-40Q side view.
No version of the XP-40Q entered service.

However, these improvements were not sufficient to justify its adoption into service, especially considering the logistical and operational advantages of standardizing on the newer aircraft types already in production.

As a result, the XP-40Q remained an experimental prototype, and the project was ultimately canceled, marking the end of the development line for the P-40 series.

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But that wasn’t the end for the XP-40Q. In 1946, pilot Joe Ziegler purchased the surplus XP-40Q-2A aircraft and entered it into the 1947 Thompson Trophy Race.

Joe Ziegler's XP-40Q-2A.
Joe Ziegler’s XP-40Q-2A racing aircraft. It was lost after catching fire.

However the aircraft’s previous mechanical issues were still present, and it caught fire while Ziegler was flying it in the race. He had to bail the out aircraft, and broke his leg on impact.

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Sadly, the XP-40Q was lost, bringing the story of this unique aircraft to a definitive end.