Curtiss P-40 Warhawk

The Curtiss P-40 Warhawk was an American single-engine, single-seat, all-metal fighter and ground attack aircraft that first flew in 1938. It was used by the air forces of 28 nations, including those of most Allied powers during World War II, and remained in front line service until the end of the war. By November 1944, when production of the P-40 ceased, 13,738 had been built, all at Curtiss-Wright Corporation's main production facility at Buffalo, New York.

The P-40 design was a modification of the previous Curtiss P-36; this reduced development time and enabled a rapid entry into production and operational service.

Warhawk was the name the United States Army Air Corps adopted for all models, making it the official name in the United States 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.

The P-40's lack of a two-stage 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. Between 1941 and 1944, however, 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 high altitude performance was not as critical in those theaters, where it served as an air supremacy fighter, bomber escort and fighter bomber.

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

In theaters where high altitude performance was less important, the P-40 proved an effective fighter. Although it gained a post-war 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 the P-40 performed surprisingly well as an air superiority fighter, at times suffering severe losses, but also taking a very heavy toll on enemy aircraft. The P-40 offered the additional advantage of low cost, which kept it in production as a ground attack fighter long after it was obsolete in air superiority.

As of 2008, 19 P-40s were airworthy.

Design and development

The prototype 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 by a liquid-cooled, supercharged Allison V-1710 V-12 engine. The V-12 engine offered no more power than the radial engine but had smaller frontal area and therefore reduced drag.

Performance characteristics

The P-40 had good agility, especially at high speed and medium to low altitude. It was one of the tightest-turning monoplane fighters of the war, although at lower speeds it could not out-turn the extremely maneuverable Japanese fighters such as the A6M Zero and Nakajima Ki-43 "Oscar".

Allison V-1710 engines produced about 1040 hp at sea level and at 14,000 ft: not powerful by the standards of the time and the early P-40 variants' top speeds were unimpressive. Also, the single-stage, single-speed supercharger meant that the P-40 could not compete with contemporary designs as a high altitude fighter. Later versions, with Allisons or Packard Merlin engines were more capable. Climb performance was 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". Caldwell added that the P-40 was "faster downhill than almost any other aeroplane with a propeller."

The P-40 tolerated harsh conditions in the widest possible variety of climates. It was a semi-modular design and thus easy to maintain in the field. It lacked innovations of the time, such as boosted ailerons or automatic leading edge slats, but it had a strong structure including a five-spar wing, which enabled P-40s to survive some midair collisions: both accidental impacts and 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 it was 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 in (12.7 mm) machine guns firing through the prop and two .303 Browning machine gun s in each wing to be inadequate. This was rectified with the P-40E Kittyhawk, which had three .50 in (12.7 mm) guns in each wing, although Caldwell preferred the Tomahawk in other respects. It had armour around the engine and the cockpit, which enabled it to withstand considerable damage. This was one of the characteristics that allowed Allied pilots in Asia and the Pacific to attack Japanese fighters head on, rather than try to out-turn and out-climb their opponents. Late-model P-40s were regarded as well armored. Visibility was adequate, although hampered by an overly complex windscreen frame, and completely blocked to the rear in early models due to the raised turtledeck. Poor ground visibility and the relatively narrow landing gear track led to many losses due to accidents on the ground.

Operational history

In April 1939, the U.S. Army Air Corps, witnessing the new sleek, high speed, in-line-engined fighters of the European air forces, placed the largest single fighter order it had ever made for fighters: 524 P-40s.

French Air Force

An early order came from the French ''Armée de l'Air '', which was already operating P-36s. The ''Armée de l'Air'' ordered 140 as the Hawk 81A-1 but the French military had been defeated before the aircraft had left the factory, consequently, the aircraft were diverted to British and Commonwealth service (as the Tomahawk I), in some cases complete with metric flight instruments. In late 1942, as French forces in North Africa split from the Vichy government to side with the Allies, U.S. forces transferred P-40Fs to the ''GC II/5'', a squadron that was historically associated with the Lafayette Escadrille . GC II/5 used its P-40Fs and Ls in combat in Tunisia and, later, for patrol duty off the Mediterranean coast until mid-1944 when they were replaced by P-47 Ds.

British Commonwealth units in Mediterranean and European theaters

Deployment

In all, 18 British Royal Air Force (RAF) squadrons, as well as 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 tank s. These were installed in subsequent shipments. The British pilots found that when landing the P-40, it was advisable to perform a "wheels" landing (i.e. touching down on the mains first) rather than a "three-point" landing used with their British aircraft. This was due to the P-40's rear-folding mainwheels, which were more prone to collapse when heavily loaded. Testing showed the aircraft did not have adequate performance for use in Northwest Europe in high-altitude combat due to the effective service ceiling limitation.

RAF Spitfires used in the theater operated at heights around , while the Allison engine, with its single-stage, low altitude rated supercharger, worked best at or lower. When the Tomahawk was used by Allied units based in the UK from August 1941, this limitation relegated the Tomahawk to low-level reconnaissance and only one squadron, No. 414 Squadron RCAF was used in the fighter role. Subsequently, the British Air Ministry deemed the P-40 completely unsuitable for the theater. P-40 squadrons from mid-1942 re-equipped with aircraft such as Mustangs.

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 major improvements, and were the DAF's air superiority fighter for the critical first few months of 1942, until "tropicalised " Spitfire s were available.

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 in the fighter-bomber role.

From July 1942 until mid-1943, elements of the US 57th Fighter Group (57th FG) were attached to DAF P-40 units. The British government also donated 23 P-40s to the Soviet Union.

Combat performance

Tomahawks and Kittyhawks would bear the brunt of ''Luftwaffe'' and ''Regia Aeronautica '' fighter attacks during the North African campaign. The P-40s were considered superior to the Hurricane, which they replaced as the primary fighter of the Desert Air Force.

According to some sources the P-40 initially proved quite effective against Axis aircraft and contributed to a slight shift of momentum in the Allied favor. The gradual replacement of Hurricanes by the Tomahawks and Kittyhawks led to the ''Luftwaffe'' accelerating retirement of the Bf 109E and introducing the newer Bf 109F; these were to be flown by the veteran pilots of elite ''Luftwaffe'' units, such as ''Jagdgeschwader'' 27 (JG27), in North Africa.

The P-40 was generally considered roughly equal or slightly superior to the Bf 109 at low altitude, but inferior at high altitude, particularly against the Bf 109F. Most air combat in North Africa took place well below , thus negating much of the Bf 109's superiority. The P-40 usually had an edge over Bf 109 in horizontal maneuverability, dive speed and structural strength, was roughly equal in firepower, but was slightly inferior in speed and outclassed in rate of climb and operational ceiling.

The P-40 was generally superior to early Italian fighter types, such as the Fiat G.50 and the Macchi C.200 . Its performance against the Macchi C.202 ''Folgore'' elicited varying opinions. Some observers consider the Macchi C.202 superior. Clive Caldwell, who scored victories against them in his P-40, felt that the ''Folgore'' would have been superior to both the P-40 and the Bf 109 except that its armament of only two or four machine guns was inadequate. Other observers considered the two equally matched, or favored the ''Folgore'' in aerobatic performance, such as turning radius. Boyne wrote that over Africa, the P-40 and the ''Folgore'' were "equivalent".

Against its lack of high altitude performance the P-40 was considered to be a stable gun platform, and its rugged construction meant that it was able to operate from rough front line airstrips with a good rate of serviceability.

The Flying Tigers, known officially as the 1st American Volunteer Group, were a unit of the Republic of China Air Force, recruited from U.S. aviators. From late 1941, the P-40B was used by the Flying Tigers. They were divided into three fighter intercept squadrons, the "Hells Angels", "Adam & Eves" and "Panda".

Compared to opposing Japanese fighters, the P-40B's strengths were that it was sturdy, well armed, faster in a dive and possessed a excellent rate of roll. While the P-40s could not match the maneuverability of Japanese Nakajima Ki-27 s and Ki-43s in a slow speed turning dogfight, at higher speeds they were more than a match. AVG leader Claire Chennault trained his pilots to use the P-40's particular performance advantages. The P-40 had a higher dive speed than the Japanese fighters, for example, and could be used to exploit so-called "boom-and-zoom" tactics. The AVG was highly successful, and its feats were widely-published, for propaganda purposes. According to their own count, in just nine months, the Flying Tigers shot down 286 aircraft for the loss of just four of their own.

United States Army Air Forces

A total of 15 entire USAAF pursuit/fighter groups (FG), along with other pursuit/fighter squadron s and a few tactical reconnaissance (TR) units, operated the P-40 during 1941–45.

As was also the case with the P-39, many USAAF officers considered the P-40 inadequate, and it was gradually replaced by the P-38 , P-47 and P-51 . However, the bulk of the fighter operations by the USAAF in 1942–43 were borne by the P-40 and the Bell P-39 Airacobra. In the Pacific, these two fighters, along with the U.S. Navy's F4F Wildcat, contributed more than any other U.S. types to breaking Japanese air power during this critical period.

Pacific theaters

The P-40 was the main USAAF fighter aircraft in the South West Pacific and Pacific Ocean theaters during 1941–42.

In the first major battles, at Pearl Harbor and in the Philippines , USAAF P-40 squadrons suffered crippling losses on the ground and in the air to Japanese fighters such as the Ki-43 Oscar and A6M Zero.

However, in the Dutch East Indies campaign , the 17th Pursuit Squadron (Provisional), formed from USAAF pilots evacuated from the Philippines, claimed 49 Japanese aircraft destroyed, for the loss of 17 P-40s. And in the Solomon Islands and New Guinea Campaigns, as well as the air defense of Australia, improved tactics and training allowed the USAAF to more effectively utilize the strengths of the P-40.

Due to aircraft fatigue, scarcity of spare parts and replacement problems, the US Fifth Air Force and Royal Australian Air Force created a joint P-40 management and replacement pool on 30 July 1942 and many P-40s went back and forth between both air forces.

The 49th Fighter Group was in action in the Pacific from the beginning of the war. Robert DeHaven scored 10 kills (from 14 kills overall) in the P-40 with the 49th FG. He compared the P-40 favorably with the P-38:If you flew wisely, the P-40 was a very capable aircraft. [It] could outturn a P-38, a fact that some pilots didn't realise when they made the transition between the two aircraft. [...] The real problem with it was lack of range. As we pushed the Japanese back, P-40 pilots were slowly left out of the war. So when I moved to P-38s, an excellent aircraft, I did not [believe] that the P-40 was an inferior fighter, but because I knew the P-38 would allow us to reach the enemy. I was a fighter pilot and that was what I was supposed to do."

The 8th, 15th, 18th, 24th, 49th, 343rd and 347th PGs/FGs, flew P-40s in the Pacific theaters, between 1941 and 1945, with most units converting to P-38s during 1943-44. In 1945 the 71st Reconnaissance Group employed them as armed forward air controllers during ground operations in the Philippines until it received delivery of P-51 Mustang s. They claimed 655 aerial victories.

Contrary to conventional wisdom, with sufficient altitude the P-40 could actually turn with the A6M and other Japanese fighters, using a combination of nose-down vertical turn with a bank turn, a technique known as a low yo-yo . Robert DeHaven describes how this tactic was used in the 49th Fighter group:[Y]ou could fight a Jap on even terms, but you had to make him fight your way. He could outturn you at slow speed. You could outturn him at high speed. When you got into a turning fight with him, you dropped your nose down so you kept your airspeed up, you could outturn him. At low speed he could outroll you because of those big ailerons ... on the Zero. If your speed was up over 275, you could outroll [a Zero]. His big ailerons didn't have the strength to make high speed rolls... You could push things, too. Because ... [i]f you decided to go home, you could go home. He couldn't because you could outrun him. [...] That left you in control of the fight.

China-Burma-India theater

USAAF and Chinese P-40 pilots performed well in this theater, scoring high kill ratios against Japanese types such as the Ki-43, Nakajima Ki-44 "Tojo" and the Zero. The P-40 remained in use in the CBI until 1944, and was reportedly preferred over the P-51 Mustang by some US pilots flying in China.

The American Volunteer Group (Flying Tigers) was integrated into the USAAF as the 23rd Fighter Group in June 1942. The unit continued to fly newer model P-40s until the end of the war, racking up a high kill-to-loss ratio.

Units arriving in the China-Burma-India theater after the AVG in the 10th and 14th air forces continued to perform well with the P-40, claiming 973 kills in the theater, or 64.8 percent of all enemy aircraft shot down. Aviation historian Carl Molesworth stated that "...the P-40 simply dominated the skies over Burma and China. They were able to establish air superiority over free China, northern Burma and the Assam valley of India in 1942, and they never relinquished it."

In addition to the 23rd FG, the 3rd, 5th, 51st and 80th FGs, along with the 10th TRS, operated the P-40 in the CBI (note, although part of the US 14th AF, the P-40s of 3rd and 5th FGs of the Chinese American Composite Wing were flown by both American and Chinese pilots). In addition to its role as a fighter aircraft, CBI P-40 pilots used the aircraft very effectively as a fighter-bomber. The 80th Fighter Group in particular used its so-called ''B-40'' (P-40s carrying 1,000-pound high explosive bombs) to destroy Japanese-held bridges and kill bridge repair crews, sometimes demolishing their target with a single bomb. At least 40 U.S. pilots reached ace status while flying the P-40 in the CBI.

Europe and Mediterranean theaters

Warhawks were used extensively in the Mediterranean Theater of Operations (MTO) by USAAF units, including the 33rd , 57th , 58th , 79th , 324th and 325th Fighter Group s.

While the P-40 suffered heavy loses in the MTO, many USAAF P-40 units achieved high kill-to-loss ratios against Axis aircraft. For example, the 324th FG scored better than a 2:1 ratio in the MTO. In all, 23 U.S. pilots became aces in the MTO while flying the P-40, most of them during the first half of 1943. As in the Pacific, success in combat depended in part on experience and effective tactics.

The much-lightened P-40L was most heavily used in the MTO, primarily by U.S. pilots. Many US pilots stripped down their P-40s even further to improve performance, often removing two or more of the wing guns from the P-40F/L.

Royal Australian Air Force

The Kittyhawk was the main fighter used by the RAAF in World War II, in greater numbers than the Spitfire. Two RAAF squadrons serving with the Desert Air Force, No. 3 and No. 450 Squadron s, were the first Australian units to be assigned P-40s. Other RAAF pilots served with RAF or SAAF P-40 squadrons in the theater.

At the same time as the heaviest fighting in North Africa, the Pacific War was also in its early stages, and RAAF units in Australia were completely lacking in suitable fighter aircraft. Spitfire production was being absorbed by the war in Europe; P-38s were trialled, but were difficult to obtain; Mustangs had not yet reached squadrons anywhere, and Australia's tiny and inexperienced aircraft industry was geared towards larger aircraft. USAAF P-40s and their pilots originally intended for the U.S. Far East Air Force in the Philippines, but diverted to Australia as a result of Japanese naval activity were the first suitable fighter aircraft to arrive in substantial numbers. By mid-1942, the RAAF was able to obtain some USAAF replacement shipments; the P-40 was given the RAAF designation A-29.

Late in 1945, RAAF fighter squadrons in the South West Pacific began converting to P-51Ds. However, Kittyhawks were in use with the RAAF until the end of the war, in Borneo. In all, the RAAF acquired 841 Kittyhawks (not counting the British-ordered examples used in North Africa), including 163 P-40E, 42 P-40K, 90 P-40 M and 553 P-40N models. In addition, the RAAF ordered 67 Kittyhawks for use by No. 120 (Netherlands East Indies) Squadron (a joint Australian-Dutch unit in the South West Pacific). The P-40 was retired by the RAAF in 1947.

Royal Canadian Air Force

In mid-May 1940, the Royal Canadian Air Force had its first look at the P-40. At that time a party of American officers flew to Uplands Airport near Ottawa where they saw the XP-40 and a Spitfire flown in comparative tests. When Canadian Army requirements for France were drawn up, one of the units was to have been an Army Co-operation Wing (No. 101) consisting of three squadrons: No. 400 (previously No. 110) Squadron and No. 414 , equipped with P-40 Tomahawk aircraft, formed No. 39 (Army Co-operation) Wing (RCAF). By January 1943, all three squadrons had converted to the Mustang Mk I. In all, the RCAF received 72 Kittyhawk I, 12 Kittyhawk Ia, 15 Kittyhawk III and 35 Kittyhawk IV aircraft, for a total of 134 aircraft, plus the loan of nine P-40Ks in the Aleutians, all in lieu of the 144 P-39 Airacobras originally allotted to Canada and rejected.

One of the most significant uses of the RCAF P-40s occurred in the 1942 Aleutians campaign . When the Imperial Japanese Navy moved to attack Midway , it sent a diversionary battle group to attack the Aleutian Islands. The RCAF sent No. 111 Squadron RCAF , flying the Kittyhawk I, to a forward base on Adak Island, Alaska. During the drawn-out campaign, 12 Canadian Kittyhawks operated on a rotational basis from a new, more advanced base on Amchitka , southeast of Kiska . Two RCAF fighter squadrons, No. 111 and No. 14 , took "turn-about" at the base. During the deployment, one Nakajima A6M2-N seaplane was shot down by Squadron Leader Ken Boomer . After the Japanese threat diminished, the RCAF units returned to Canada and eventually transferred to England without their Kittyhawks.

Royal New Zealand Air Force

Some Royal New Zealand Air Force (RNZAF) pilots and New Zealand ers in other air forces flew British P-40s while serving with DAF squadrons in North Africa and Italy, including the ace Jerry Westenra .

A total of 301 P-40s were allocated to the RNZAF under Lend-Lease , for use in the Pacific Theater, although four of these were lost in transit. The aircraft equipped 14 Squadron , 15 Squadron , 16 Squadron , 17 Squadron , 18 Squadron , 19 Squadron and 20 Squadron .

RNZAF P-40 squadrons were successful in air combat against the Japanese between 1942 and 1944. Their pilots claimed 100 aerial victories in P-40s, whilst losing 20 aircraft in combat.Geoff Fisken , the highest scoring British Commonwealth ace in the Pacific, flew P-40s with 15 Squadron, although half of his victories were claimed with the Brewster Buffalo .

The overwhelming majority of RNZAF P-40 victories were scored against Japanese fighters, mostly Zeroes. Other victories included Aichi D3A "Val" dive bombers. The only confirmed twin engine claim, a Ki-21 "Sally" (misidentified as a G4M "Betty") fell to Fisken in July 1943.

From late 1943 and 1944, RNZAF P-40s were increasingly used against ground targets, including the innovative use of naval depth charges as improvised high-capacity bombs. The last front line RNZAF P-40s were replaced by F4U Corsair s in 1944. The P-40s were relegated to use as advanced pilot trainers.

The remaining RNZAF P-40s, excluding the 20 shot down and 154 written off, were mostly scrapped at Rukuhia in 1948.

Soviet Union

The Soviet ''Voenno-Vozdushnye Sily'' (VVS; "Military Air Forces") and ''Morskaya Aviatsiya'' (MA; "Naval Air Service") also referred to P-40s as Tomahawks and Kittyhawks. In fact, the Curtiss P-40 Tomahawk/Kittyhawk was the first Allied fighter supplied to the USSR under the Lend-Lease agreement.

Their units used 2,097 146 Tomahawks were shipped from Great Britain and 49 more arrived from the US, many of them coming incomplete, lacking machine guns and even the lower half of the engine cowling. In late September 1941, the first 48 P-40s were assembled and checked in USSR. Test flights showed some manufacturing defects: generator and oil pump gears and generator shafts failed repeatedly, which led to emergency landings. The test report indicated that the Tomahawk was inferior to Soviet “M-105P-powered production fighters in speed and rate of climb. However, it has good short field performance, horizontal manoeuvrability, range and endurance”.

Nevertheless, Tomahawks and Kittyhawks were used against the Germans. The 126th IAP fighting on the Western and Kalinin fronts were the first unit to receive the P-40. The regiment entered action on 12 October 1941. By 15 November 1941, that unit had shot down 17 German aircraft. However, Lt (SG) Smirnov noted that the P-40 armament was sufficient for strafing enemy lines but rather ineffective in aerial combat. Another pilot, S.G. Ridnyy (Hero of Soviet Union), remarked that he had to shoot half the ammunition at 50–100 meters (164–339 ft) to shoot down an enemy aircraft.

In January 1942 some 198 aircraft sorties were flown (334 flying hours) and 11 aerial engagements were conducted, in which five Bf 109s, one Ju 88, and one He 111 were downed. These statistics reveal a surprising fact: it turns out that the Tomahawk was fully capable of successful air combat with a Bf 109. The reports of pilots about the circumstances of the engagements confirm this fact. On 18 January 1942, Lieutenants S. V. Levin and I. P. Levsha (in pair) fought an engagement with seven Bf 109s and shot down two of them without loss. On 22 January, a flight of three aircraft led by Lieutenant E. E. Lozov engaged 13 enemy aircraft and shot down two Bf 109Es, again without loss. Altogether in January two Tomahawks were lost; one downed by German antiaircraft artillery and one lost to Messerschmitts.

The Soviets stripped down their P-40s significantly for combat, in many cases removing the wing guns altogether in P-40B/C types, for example. Soviet Air Force reports state that they liked the range and fuel capacity of the P-40 which were superior to most of the Soviet fighters, though they still preferred the P-39. Soviet pilot Nikolai G. Golodnikov recalled: "The cockpit was vast and high. At first it felt unpleasant to sit waist-high in glass, as the edge of the fuselage was almost at waist level. But the bullet-proof glass and armoured seat were strong and visibility was good. The radio was also good. It was powerful, reliable, but only on HF (high frequency). The American radios did not have hand microphones but throat microphones. These were good throat mikes: small, light and comfortable." The biggest complaint of some Soviet airmen was its poor climb rate and problems with maintenance, especially with burning out the engines. VVS pilots usually flew the P-40 at War Emergency Power settings while in combat, this would bring the acceleration and speed performance closer to that of their German rivals, but could burn out engines in a matter of weeks. They also had difficulty with the more demanding requirements for fuel quality and oil purity of the Allison engines. A fair number of burnt out P-40s were re-engined with Soviet Klimov engines but these performed relatively poorly and were relegated to rear area use.

The P-40 saw the most front-line use in Soviet hands in 1942 and early 1943. It was used in the northern sectors and played a significant role in the defense of Leningrad . The most numerically important types were P-40B/C, P-40E and P-40K/M. By the time the better P-40F and N types became available, production of superior Soviet fighters had increased sufficiently so that the P-40 was replaced in most Soviet Air Force units by the Lavochkin La-5 and various later Yakovlev types. In spring 1943, Lt D.I. Koval of the 45th IAP gained ace status on the North-Caucasian front, shooting down six German aircraft flying a P-40. Some Soviet P-40 squadrons had good combat records. They provided close air support as well as air-to-air capability while Soviet pilots became aces on the P-40, not as many as on the P-39 Airacobra , which was the most numerous Lend Lease fighter used by the Soviet Union. However Soviet commanders considered the Kittyhawwk significantly outclassing the Hurricane, although it was “not in the same league as the Yak-1”. The aircraft was regarded as excessively heavy, with poor vertical manoeuvrability and rate of climb. It had inferior armament and generally considered no match for the Messerschmitt at low and medium altitude where it was 30–40 km/h (19-25 mph) slower than the Bf 109F-4 and Bf 109G-2. Subsequently, the P-40s were gradually relegated to the air defence role.

Variants and development stages

P-40

The P-40 (Curtiss Model 81A-1) was the first production variant, 199 built.

P-40A

One P-40 was modified with a camera installation in the rear fuselage and re-designated P-40A.

*Revised versions of the P-40 soon followed: the P-40B or Tomahawk IIA had extra .30in in (7.62 mm) U.S., or .303 in (7.7 mm) machine guns in the wings and a partially protected fuel system; the P-40C or Tomahawk IIB added underbelly drop tank and bomb shackles, self-sealing fuel tanks and other minor revisions, but the extra weight did have a negative impact on aircraft performance. (All versions of the P-40 had a relatively low power-to-weight ratio compared to contemporary fighters.)

*Only a small number of P-40D or Kittyhawk Mk Is were made, less than 50. With a new, larger Allison engine, slightly narrower fuselage, redesigned canopy, and improved cockpit, the P-40D eliminated the nose-mounted .50 in (12.7 mm) guns and instead had a pair of .50 in (12.7 mm) guns in each wing. The distinctive chin airscoop grew larger in order to adequately cool the large Allison engine.

*Retrospective designation for a single prototype. The P-40A was a single camera-carrying aircraft.

*The P-40E or P-40E-1 was similar in most respects to the P-40D, except for a slightly more powerful engine and an extra .50 in (12.7 mm) gun in each wing, bringing the total to six. Some aircraft also had small underwing bomb shackles. Supplied to the Commonwealth air forces as the Kittyhawk Mk IA. The P-40E was the variant that bore the brunt of air-to-air combat by the type in the key period of early to mid 1942, for example with the first US squadrons to replace the AVG in China (the AVG was already transitioning to this type from the P-40B/C), the type used by the Australians at Milne Bay, by the New Zealand squadrons during most of their air to air combat, and by the RAF/Commonwealth in North Africa as the Kittyhawk IA.

*P-40F and P-40L, which both featured Packard V-1650 Merlin engine in place of the normal Allison, and thus did not have the carburetor scoop on top of the nose. Performance for these models at higher altitudes was better than their Allison-engined cousins. The L in some cases also featured a fillet in front of the vertical stabilizer , or a stretched fuselage to compensate for the higher torque. The P-40L was sometimes nicknamed "Gypsy Rose Lee ", after a famous stripper of the era, due to its stripped-down condition. Supplied to the Commonwealth air forces under the designation Kittyhawk Mk II, a total of 330 Mk IIs were supplied to the RAF under Lend-Lease. The first 230 aircraft are sometimes known as the Kittyhawk Mk IIA. The P-40F/L was extensively used by U.S. fighter groups operating in the Mediterranian Theater.

*P-40G : 43 P-40 aircraft fitted with the wings of the Tomahawk Mk IIA. A total of 16 aircraft were supplied to the Soviet Union, and the rest to the US Army Air Force. It was later redesignated RP-40G.

*P-40K, an Allison-engined P-40L, with the nosetop scoop retained and the Allison configured scoop and cowl flaps. Supplied to the Commonwealth air forces as the Kittyhawk Mk III, it was widely used by US units in the CBI.

*P-40M, version generally similar to the P-40K, with a stretched fuselage like the P-40L and powered by an Allison V-1710-81 engine giving better performance at altitude (compared to previous Allison versions). It had some detail improvements and it was characterized by two small air scoops just before the exhaust pipes. Most of them were supplied to Allied countries (mainly UK and USSR), while some others remained in the USA for advanced training. It was also supplied to the Commonwealth air forces as the Kittyhawk Mk. III.

*P-40N (manufactured 1943–44), the final production model. The P-40N featured a stretched rear fuselage to counter the torque of the larger, late-war Allison engine, and the rear deck of the cockpit behind the pilot was cut down at a moderate slant to improve rearward visibility. A great deal of work was also done to try and eliminate excess weight to improve the Warhawk's climb rate. Early N production blocks dropped a .50 in (12.7 mm) gun from each wing, bringing the total back to four; later production blocks reintroduced it after complaints from units in the field. Supplied to Commonwealth air forces as the Kittyhawk Mk IV. A total of 553 P-40Ns were acquired by the Royal Australian Air Force, making it the variant most commonly used by the RAAF. Subvariants of the P-40N ranged widely in specialization from stripped down four-gun "hot rods" which could reach the highest top speeds of any production variant of the P-40 (up to 380 mph), to overweight types with all the extras intended for fighter-bombing or even training missions.

*P-40P : The designation of 1,500 aircraft ordered with V-1650-1 engines, but actually built as the P-40N with V-1710-81 engines.

*P-40R : The designation of P-40F and P-40L aircraft, converted into training aircraft in 1944.

*RP-40 : Some American P-40s were converted into reconnaissance aircraft.

*TP-40 : Some P-40s were converted into two-seat trainers.

*Twin P-40 : Probably the most unusual variant, it was a P-40C outfitted in 1942 with a pair of 1,300 hp (969 kW) Packard V-1650-1 Merlin engines mounted atop the wings, over the main landing gear.

Survivors

Of the 13,738 P-40s built, only 19 P-40s remain airworthy, with three of them being converted to dual-controls/dual-seat configuration. Approximately 80 aircraft are on static display or under restoration.