Curtis P-40 Warhawk

The Curtiss P-40 Warhawk, an American single-engined, single-seat, all-metal fighter-bomber, first took to the skies in 1938. This aircraft was a significant evolution from its predecessor, the Curtiss P-36 Hawk, which allowed for a reduced development timeline and a swift transition into production and operational service. The Warhawk was widely used by Allied powers during World War II and remained in frontline service until the war’s conclusion. It became the third most-produced American fighter of the war, following the North American P-51 Mustang and Republic P-47 Thunderbolt, with a total of 13,738 units built by November 1944 at Curtiss-Wright Corporation’s main production facilities in Buffalo, New York.

The name “P-40 Warhawk” was initially given by the United States Army Air Corps, and after June 1941, the United States Army Air Forces (USAAF) adopted this name for all models, making it the official designation in the United States. The British Commonwealth and Soviet air forces, however, used different names for various models: “Tomahawk” for the original P-40, P-40B, and P-40C, and “Kittyhawk” for the P-40D and subsequent variants. The P-40 first saw combat with British Commonwealth squadrons in the Desert Air Force during the Middle East and North African campaigns in June 1941. Notably, No. 112 Squadron of the Royal Air Force was among the first to operate Tomahawks in North Africa and famously adopted the “shark mouth” logo, inspired by similar markings on Luftwaffe Messerschmitt Bf 110 fighters.

The P-40’s Allison V-1710 engine lacked a two-speed supercharger, making it inferior to Luftwaffe fighters like the Messerschmitt Bf 109 and Focke-Wulf Fw 190 in high-altitude combat. As a result, it was seldom used in operations in Northwest Europe. However, between 1941 and 1944, the P-40 played a crucial role in three major theatres: North Africa, the Southwest Pacific, and China. It also had significant roles in the Middle East, Southeast Asia, Eastern Europe, Alaska, and Italy. In these theatres, where high-altitude performance was less critical, the P-40 served effectively as an air superiority fighter, bomber escort, and fighter bomber.

Despite gaining a postwar reputation as a mediocre design suitable only for close air support, more recent research indicates that the P-40 was a surprisingly effective air superiority fighter. It suffered severe losses at times but also inflicted heavy tolls on enemy aircraft. Over 200 Allied fighter pilots from countries including the UK, Australia, New Zealand, Canada, South Africa, the US, and the Soviet Union became aces flying the P-40. This included at least 20 double aces, primarily in North Africa, China, Burma, India, the Southwest Pacific, and Eastern Europe. The P-40’s low cost and durability were additional advantages, keeping it in production as a ground-attack aircraft long after it became obsolescent as a fighter.

The origins of the P-40 trace back to October 14, 1938, when Curtiss test pilot Edward Elliott flew the prototype XP-40 for the first time in Buffalo. This prototype was the 10th production Curtiss P-36 Hawk, modified by replacing its Pratt & Whitney R-1830 Twin Wasp radial engine with a liquid-cooled, supercharged Allison V-1710 V-12 engine, as directed by Chief Engineer Don R. Berlin. The initial prototype featured a glycol coolant radiator positioned under the belly, just aft of the wing’s trailing edge. USAAC Fighter Projects Officer Lieutenant Benjamin S. Kelsey flew this prototype approximately 300 miles in 57 minutes, achieving a speed of around 315 miles per hour (507 km/h). Although Kelsey was initially disappointed, he optimistically told reporters that future versions would likely achieve speeds 100 miles per hour (160 km/h) faster. Kelsey favoured the Allison engine for its sturdiness, dependability, and smooth, predictable power curve. The V-12 engine offered as much power as a radial engine but had a smaller frontal area, allowing for a more streamlined cowl and promising a theoretical 5% increase in top speed.

Curtiss engineers worked to improve the XP-40’s speed by moving the radiator forward in steps. When these changes yielded little gain, Kelsey ordered the aircraft to be evaluated in a NACA wind tunnel to identify solutions for better aerodynamic qualities. From March 28 to April 11, 1939, the prototype was studied by NACA. Based on the data obtained, Curtiss moved the glycol coolant radiator forward to the chin, with its new air scoop also accommodating the oil cooler air intake. Other improvements to the landing gear doors and the exhaust manifold combined to give a performance that satisfied the USAAC. Without beneficial tailwinds, Kelsey flew the XP-40 from Wright Field back to Curtiss’s plant in Buffalo at an average speed of 354 mph (570 km/h). Further tests in December 1939 proved the fighter could reach 366 mph (589 km/h).

An unusual production feature was a special truck rig designed to speed delivery at the main Curtiss plant in Buffalo, New York. This rig moved the newly built P-40s in two main components—the main wing and the fuselage—the eight miles from the plant to the airport, where the two units were mated for flight and delivery.

The P-40 was conceived as a pursuit aircraft and was agile at low and medium altitudes but suffered from a lack of power at higher altitudes. At medium and high speeds, it was one of the tightest-turning early monoplane designs of the war and could out-turn most opponents it faced in North Africa and on the Russian Front. In the Pacific Theater, it was out-turned at lower speeds by lightweight fighters like the Mitsubishi A6M Zero and Nakajima Ki-43 Hayabusa (known to Allies as “Oscar”). American Volunteer Group Commander Claire Chennault advised against prolonged dog-fighting with Japanese fighters due to the speed reduction favouring the Japanese.

The Allison V-1710 engines produced 1,040 hp (780 kW) at sea level and 14,000 ft (4,300 m), which was not powerful compared with contemporary fighters. The early P-40 variants’ top speeds were only average. The single-stage, single-speed supercharger meant that the P-40 was a poor high-altitude fighter. Later versions, with 1,200 hp (890 kW) Allisons or more powerful 1,400 hp Packard Merlin engines, were more capable. Climb performance varied from fair to poor, depending on the subtype. Dive acceleration was good, and dive speed was excellent. The highest-scoring P-40 ace, Clive Caldwell (RAAF), who claimed 22 of his 28½ kills in the type, said that the P-40 had “almost no vices,” although “it was a little difficult to control in terminal velocity.” The P-40 had one of the fastest maximum dive speeds of any fighter of the early war period and good high-speed handling.

The P-40 tolerated harsh conditions and a variety of climates. Its semi-modular design was easy to maintain in the field. Although it lacked innovations such as boosted ailerons or automatic leading-edge slats, its strong structure included a five-spar wing, enabling P-40s to pull high-G turns and survive some midair collisions. Intentional ramming attacks against enemy aircraft were occasionally recorded as victories by the Desert Air Force and Soviet Air Forces. Caldwell said P-40s “would take a tremendous amount of punishment, violent aerobatics as well as enemy action.” Operational range was good by early war standards and was almost double that of the Supermarine Spitfire or Messerschmitt Bf 109, although inferior to the Mitsubishi A6M Zero, Nakajima Ki-43, and Lockheed P-38 Lightning.

Caldwell found the P-40C Tomahawk’s armament of two .50-inch (13 mm) Browning AN/M2 “light-barrel” dorsal nose-mount synchronized machine guns and two .303-inch (7.7 mm) Browning machine guns in each wing to be inadequate. This was improved with the P-40D (Kittyhawk I), which abandoned the synchronized gun mounts and instead had two .50-inch (13 mm) guns in each wing, although Caldwell still preferred the earlier Tomahawk in other respects. The D model had armour around the engine and the cockpit, enabling it to withstand considerable damage. This allowed Allied pilots in Asia and the Pacific to attack Japanese fighters head-on, rather than trying to out-turn and out-climb their opponents. Late-model P-40s were well-armored. Visibility was adequate, although hampered by a complex windscreen frame and completely blocked to the rear in early models by a raised turtledeck. Poor ground visibility and a relatively narrow landing gear track caused many losses on the ground.

Curtiss tested a follow-on design, the Curtiss XP-46, but it offered little improvement over newer P-40 models and was eventually cancelled.

In conclusion, the Curtiss P-40 Warhawk stands as a testament to American ingenuity and adaptability during World War II. Its evolution from the P-36 Hawk, rapid production, and versatile combat performance across multiple theatres highlight its significance in the Allied war effort. Despite its limitations, the P-40’s contributions to achieving air superiority and supporting ground operations were invaluable, cementing its place in aviation history.