The following are from Larry Millberry's book "The Royal Canadian Air Force at War 1939 - 1945"

Tomahawk I History

The Curtiss P-40 Warhawk is an American single-engined, single-seat, all-metal fighter and ground-attack aircraft that first flew in 1938. The P-40 design was a modification of the previous Curtis P-36 Hawk which reduced development time and enabled a rapid entry into production and operational service. The Warhawk was used by most Allied powers during World War II, and remained in front line service until the end of the war. It was the third most-produced American fighter of World War II, after the P-51 and P-47; by November 1944, when production of the P-40 ceased, 13,738 had been built, all at Curtiss-Wright Corporation's main production facilities at Buffalo, New York.

P-40 Warhawk was the name the United States Army Air Corps and after June 1941, USAAF-adopted name for all models, making it the official name in the U.S. for all P-40s. The British Commonwealth and Soviet air forces used the name Tomahawk for models equivalent to the P-40B and P-40C, and the name Kittyhawk for models equivalent to the P-40D and all later variants.

P-40s first saw combat with the British Commonwealth squadrons of the Desert Air Force in the Middle East and North African campaigns, during June 1941. No. 112 Squadron Royal Air Force, was among the first to operate Tomahawks in North Africa and the unit was the first Allied military aviation unit to feature the "shark mouth" logo, copying similar markings on some Luftwaffe Messerschmitt Bf 110 twin-engine fighters.

The P-40's lack of a two-speed supercharger made it inferior to Luftwaffe fighters such as the Messerschmitt Bf 109 or the Focke-Wulf Fw 190 in high-altitude combat and it was rarely used in operations in Northwest Europe. However, between 1941 and 1944, the P-40 played a critical role with Allied air forces in three major theaters: North Africa, the Southwest Pacific, and China. It also had a significant role in the Middle East, Southeast Asia, Eastern Europe, Alaska and Italy. The P-40's performance at high altitudes was not as important in those theaters, where it served as an air superiority fighter, bomber escort and fighter-bomber. Although it gained a postwar reputation as a mediocre design, suitable only for close air support, more recent research including scrutiny of the records of individual Allied squadrons indicates that this was not the case: the P-40 performed surprisingly well as an air superiority fighter, at times suffering severe losses, but also inflicting a very heavy toll on enemy aircraft. Based on war-time victory claims, over 200 Allied fighter pilots from 7 different nations (United Kingdom, Australia, New Zealand, Canada, South Africa, the United States, and the Soviet Union) became aces flying the P-40, with at least 20 double aces mostly in the North Africa, CBI, Pacific and Russian Front theaters. The P-40 offered the additional advantage of low cost, which kept it in production as a ground-attack aircraft long after it was obsolete as a fighter.

Design and Development

Origins

On 14 October 1938, Curtiss test pilot Edward Elliott flew the prototype XP-40 on its first flight in Buffalo. The XP-40 was the 10th production Curtiss P-36 Hawk, with its Pratt & Whitney R-1830 (Twin Wasp) 14-cylinder air-cooled radial engine replaced at the direction of Chief Engineer Don R. Berlin by a liquid-cooled, supercharged Allison V-1710 V-12 engine. The first prototype placed the glycol coolant radiator in an underbelly position on the fighter, just aft of the wing's trailing edge. USAAC Fighter Projects Officer Lieutenant Benjamin S. Kelsey flew this prototype some 300 miles in 57 minutes, approximately 315 miles per hour (507 km/h). Hiding his disappointment, he told reporters that future versions would likely go 100 miles per hour (160 km/h) faster. Kelsey was interested in the Allison engine because it was sturdy and dependable, and it had a smooth, predictable power curve. The V-12 engine offered as much power as a radial engine but had a smaller frontal area and allowed a more streamlined cowl than an aircraft with a radial engine, 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. Seeing little gain, Kelsey ordered the aircraft to be evaluated in a NACA wind tunnel to identify solutions for better aerodynamic qualities. From 28 March to 11 April 1939, the prototype was studied by NACA. Based on the data obtained, Curtiss moved the glycol coolant radiator forward to the chin; its new air scoop also accommodated the oil cooler air intake. Other improvements to the landing gear doors and the exhaust manifold combined to give performance that was satisfactory to the USAAC. Without beneficial tail winds, 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 to speed delivery at the main Curtiss plant in Buffalo, New York. The 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.

British and Commonwealth Deployment

In all, 18 Royal Air Force (RAF) squadrons, four Royal Canadian Air Force (RCAF), three South African Air Force (SAAF) and two Royal Australian Air Force (RAAF) squadrons serving with RAF formations, used P-40s The first units to convert were Hawker Hurricane squadrons of the Desert Air Force (DAF), in early 1941. The first Tomahawks delivered came without armor, bulletproof windscreens or self-sealing fuel tanks, which were installed in subsequent shipments. Pilots used to British fighters sometimes found it difficult to adapt to the P-40's rear-folding landing gear, which was more prone to collapse than the lateral-folding landing gear of the Hawker Hurricane or Supermarine Spitfire. In contrast to the "three-point landing" commonly employed with British types, P-40 pilots were obliged to use a "wheels landing": a longer, low angle approach that touched down on the main wheels first.

Testing showed the aircraft did not have the performance needed for use in Northwest Europe at high-altitude, due to the service ceiling limitation. Spitfires used in the theater operated at heights around 30,000 ft (9,100 m), while the P-40's Allison engine, with its single-stage, low altitude rated supercharger, worked best at 15,000 ft (4,600 m) or lower. When the Tomahawk was used by Allied units based in the UK from February 1941, this limitation relegated the Tomahawk to low-level reconnaissance with RAF Army Cooperation Command and only No. 403 Squadron RCAF was used in the fighter role for a mere 29 sorties, before being replaced by Spitfires. Air Ministry deemed the P-40 unsuitable for the theater. UK P-40 squadrons from mid-1942 re-equipped with aircraft such as Mustangs.

A Kittyhawk Mk III of No. 112 Squadron RAF, taxiing at Medenine, Tunisia, in 1943. A ground crewman on the wing is directing the pilot, whose view ahead is hindered by the aircraft's nose.

The Tomahawk was superseded in North Africa by the more powerful Kittyhawk ("D"-mark onwards) types from early 1942, though some Tomahawks remained in service until 1943. Kittyhawks included many improvements and were the DAF's air superiority fighter for the critical first few months of 1942, until "tropicalised" Spitfires were available. In 2012, the virtually intact remains of a Kittyhawk were found; it had run out of fuel in the Egyptian Sahara in June 1942.

DAF units received nearly 330 Packard V-1650 Merlin-powered P-40Fs, called Kittyhawk IIs, most of which went to the USAAF, and the majority of the 700 "lightweight" L models, also powered by the Packard Merlin, in which the armament was reduced to four .50 in (12.7 mm) Brownings (Kittyhawk IIA). The DAF also received some 21 of the later P-40K and the majority of the 600 P-40Ms built; these were known as Kittyhawk IIIs. The "lightweight" P-40Ns (Kittyhawk IV) arrived from early 1943 and were used mostly as fighter-bombers. From July 1942 until mid-1943, elements of the U.S. 57th Fighter Group (57th FG) were attached to DAF P-40 units. The British government also donated 23 P-40s to the Soviet Union