Curtiss P-40 Warhawk variants


The Curtiss P-40 Warhawk was a WWII fighter aircraft that was developed from the P-36 Hawk, via the P-37. Many variants were built, some in large numbers, under names including the Hawk, Tomahawk, and Kittyhawk.

Allison-engined Model 75

XP-37

In early 1937, after realizing the Hawk 75 was inferior to more modern European designs, the USAAC ordered one P-36 to be modified with an Allison V-1710 inline engine. The prototype Hawk was fitted with a turbo-supercharged 1,150 hp Allison V-1710-11 engine as the XP-37. The cockpit was moved back towards the tail to make room for the massive supercharger, and the engine was cooled by two radiators on either side of the nose. Armament was one.30 M1919 Browning MG and one.50 M2 Browning MG mounted in the nose. The XP-37 was plagued with supercharger and visibility problems.

YP-37

A further 13 Model 75Is were ordered in 1938 under the designation YP-37. These differed from the XP-37 in having a V-1710-21 with a more reliable supercharger and an extended nose. The project was cancelled after continued supercharger and visibility problems.

XP-40

In 1937, the 10th P-36A was fitted with a 1,150 hp V-1710-19. Unlike the Model 75I, the resulting XP-40 did not have a turbo-supercharger, thus the cockpit was not moved back, and the radiator was moved to the ventral position. Later the landing gear was redesigned and the radiator was moved under the nose. Armament was two.50 M2 Brownings mounted in the nose.
The new engine conferred a 50 mph speed advantage over the already popular Hawk, and export orders from England and France came in quickly. In April 1939, the United States Army Air Corps also put in a domestic order for 524 Model 75Ps, which was the largest single order for a US fighter aircraft at the time.
In August 1943, the XP-40 was fitted with rubber-tracked main landing gear. Testing began in 1944, revealing problems with snow and ice being packed between the wheels and track belt, stretching the latter.

Model 81

P-40

The production P-40 were nearly identical to the XP-40, but was built with a 1,040 hp V-1710-33s and one.30 M1919 Browning in each wing. The company designation was changed to Model 81 due to the extensive changes from the standard Model 75. France, who was a large operator of the P-36, was interested in this fighter and ordered 140 aircraft as Hawk 81A-1s. However, following the 1940 French Armistice the Royal Air Force acquired these aircraft as Tomahawk Mk.Is. This variant was not considered combat-ready, as they lacked heavy armament and armor, but as there was a shortage of decent fighter aircraft after the Battle of Britain, the RAF pressed these into service for use in North Africa anyway.

Sub-variants and modifications

  • P-40, 524 aircraft ordered, only 200 produced.
  • P-40A, one P-40 that was fitted with cameras for photo reconnaissance missions.
  • P-40G, 44 P-40s that were fitted with four-gun P-40B/C wings, the first of which being unofficially designated XP-40G.
  • Hawk 81A-1, export version, 140 aircraft ordered by the Armée de L'air, but were delivered to the Royal Air Force as Tomahawk Mk.Is. A number of minor changes were made, including replacing the.30 Browning MGs in the wings with.303 Browning MGs, which was done on most Tomahawk marks.

    P-40B

Of the remaining 324 aircraft of the initial order, 131 were built as P-40Bs.
Though strongly built, the first P-40 variant was poorly protected and lacked armor and self sealing tanks. This was partly rectified with the P-40B, which had additional armor behind the cockpit, but fuel system and control line vulnerability remained a problem to some extent with all Tomahawk types. The P-40B also had an additional.30 MG in each wing.

Sub-variants

  • P-40B, 131 aircraft built.
  • Hawk 81A-2, export version, 110 aircraft produced for the RAF as Tomahawk Mk.IIs and Mk.IIAs, the latter equipped with.303 Brownings.

    P-40C

The last 193 aircraft of the original P-40 order were completed as P-40Cs.
In an attempt to further rectify the problem of poor protection, the P-40C was given self-sealing fuel tanks. The obsolete SCR-283 radio of the earlier P-40s was replaced with an SCR-274N and provisions were made for a 52 gal drop tank. The latter change increased the combat radius dramatically, and was a standard feature in all subsequent P-40s.

Sub-variants and modifications

  • P-40C, 193 aircraft built.
  • Hawk 81A-3, export version, 930 aircraft built for the RAF as Tomahawk Mk.IIBs, many of which were diverted to other allies.
  • Hawk 81A-2/3, export version, 100 Hawk 81A-3 aircraft were diverted from an RAF order and delivered to the Nationalist Chinese Air Force for use by the American Volunteer Group. Although they were officially Hawk 81A-3s, they lacked the provisions for a drop tank.

    Model 87

P-40D

Soon after P-40 production started, Curtiss began development of its intended successor, the XP-46. This aircraft was based on the P-40, but was an almost entirely different aircraft. While retaining the rear fuselage of the P-40, the XP-46 had a new wing with wider track landing gear. The nose was redesigned too, as it housed a new 1,150 hp V-1710-39 engine. This "F-series" engine differed from the "C-series" engine of the Model 81 in having a more compact external spur gear-type reduction gear box. The production version of the P-46 was to have four.30 MGs in each wing and two.50 MGs in the nose for a total of ten guns. This would have been the heaviest armament for a US fighter at the time. Both the USAAF and RAF placed orders for this aircraft, with the latter naming it "Kittyhawk".
Due to delays in the P-46 program, the USAAF asked Curtiss to prioritize development of an improved P-40. Curtiss did so, and reworked the P-40 to accommodate the V-1710-39 of the XP-46. The resulting P-40D had a shorter nose with a larger radiator, four.50 Brownings in place of the.30 units, a revised windscreen, and provisions for two 20 mm cannons. The nose guns were deleted as there wasn't room for them in the final design. Upon testing both the P-40D and XP-46 prototypes, the USAAF found that the XP-46 offered no significant improvement over the P-40C, and was inferior to the P-40D. Both the USAAF and RAF cancelled their orders for the P-46 and the name "Kittyhawk" was given to the P-40D.

Sub-variants

  • P-40D, 2 aircraft built for testing purposes, both were later modified into the prototypes of subsequent variants.
  • P-40D-1, 21 aircraft built for service with the USAAF.
  • Hawk 87A-1, export version, 560 were built for the RAF as Kittyhawk Mk.Is. The first 20 of these aircraft were built with the standard four guns, but the rest had six, making them almost identical to the later Mk.IA. Some were diverted to other allies.

    P-40E

Starting with the 24th Model 87, an additional.50 MG was added to each wing and the carburetor intake was moved forward 6 in. Although these changes were relatively minor, this new variant was given the designation P-40E.
When the P-40D and E went into service, several problems were discovered. When maneuvering in high G turns the guns would often jam due to the way the ammunition was stored. Another problem was that engine and trim management were both somewhat complex and taxing with earlier P-40's required strong rudder pressure to offset engine torque and frequent trim adjustments were needed during rapid speed changes. Both these problems were remedied sometime late in production by enlarging the vertical stabilizer and changing how the ammunition was stored.
P-40's were more a powerful, faster-flying aircraft than the primary and advanced trainers most pre-war and early-war Allied pilots were familiar with, and transition training was often inadequate or neglected altogether in the early years of the war. The landing gear was also more narrow and not as strong as in fixed gear aircraft or on some other retractable gear fighters such as the Hurricane. As a result, novice pilots had a hard time adjusting to the new fighter and there were many accidents on landing and takeoff in the early years of the war, with both Tomahawk and Kittyhawk types. Therefore, two P-40Es were fitted with a second seat to be used as trainer aircraft under the designation P-40ES. With these aircraft and improved training techniques these problems subsided.

Sub-variants and modifications

  • Prototype P-40E, the second P-40D fitted with a six-gun wing.
  • P-40E, 820 aircraft built. Somewhere along the production line flared "fishtail" exhaust stacks appeared, and an unknown number of late production aircraft had larger vertical stabilizers.
  • P-40ES, two aircraft modified into two-seat trainer aircraft.
  • P-40EF, a number of P-40Es and Ks modified by the Soviet Air Force as two seat photo reconnaissance aircraft. The "EF" designation was unofficially given to the aircraft by the Soviets, with the F standing for "Foto", the Russian word for photo.
  • Hawk 87A-2, export version, the RAF received 1,500 Kittyhawk Mk.IAs under Lend-Lease. These were given the USAAF designation P-40E-1. Some were diverted to other allies.

    P-40J

The main problem with the P-40 was its effective altitude ceiling of about 12,000 feet. Above that altitude the single-stage Allison V-1710 engine started to perform poorly. As a result, unless combat was taking place at low altitude, P-40 pilots often faced attack from above in the opening stages of an interception, a chronic problem which cost many lives. In response, Curtiss proposed the P-40J, which was basically a P-40E with a turbo-supercharged V-1710. Although a good idea on paper, there were many problems with fitting a turbo-supercharged V-1710 into the P-40. One of the main problems was the size of the turbocharger, which would not fit in the standard P-40 airframe. On top of that the intended engines were reserved for P-38 production. In May 1942 the project was cancelled without any being built.