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Table of Contents
[ Top of Page | Feedback ] Introduction The Curtiss H75 Hawk was one of a class of aircraft which set new fighter design standards in the mid 1930s. Low-winged monoplanes with all-metal construction, retractable undercarriage and enclosed cockpits; first with radial engines and later in-lines, this design standard applied to most World War Two fighters, and indeed was also the basic design of the fighters during the first ten years of the jet-age. The Hawk 75 line was distinguished by seeing early combat in every war theatre between 1938 and 1942. Chinese Hawks first flew against the Japanese in 1938, side by side with Soviet Polikarpovs; aircraft they later flew against in Finnish hands in the Continuation War. Siamese (Thai) Hawk 75s flew against French Morane-Saulnier M.S.406s in Indo-China in 1940; then later, flying alongside M.S.406s in France, scored the first kills for the French Armée de l'Air in 1939. P-36s, the United States Army Air Corps (USAAC) version of the Hawk 75 were airborne within 15 minutes of the Japanese attack at Pearl Harbor, scoring some of the earliest air combat victories of the Pacific War; Thai Hawk H75s also flew combat against the Japanese on the Malay Peninsula on the 7th December 1941, as did the Netherlands East Indies Hawks in January 1942 on Sumatra and Java. After their Government had formed an alliance with Japan, the Thai Hawk 75s then faced Allied forces in Burma who themselves were later flying Mohawks (H75s). The final act of the Hawk as a first-line combat fighter was when it was flown by Vichy French forces against Allied airforces during the invasion of Morocco in 1942 - "Operation Torch" -the first US land operation in the West. In spite of this proud combat heritage, the Curtiss Model 75 is often dismissed as simply "the precursor to the P-40 Kittyhawk" and no further interest taken in it. [ Top of Page | Feedback ] Prototype and Development The Hawk design originated in November 1934 (the same year as the Bf 109, the Hurricane and Spitfire) as a private-venture development of a single-seat fighter by Curtiss-Wright. It was a low-winged, all-metal monoplane, and originally had a 900-hp radial engine; the Wright XR-1670-5. This aeroplane was named the Curtiss Design 75 and was entered into a design competition against the Seversky P-35 (also privately developed) in April, 1936, which looked to select a replacement for the Boeing P-26 Peashooter pursuit fighter. Due to delays with the Seversky prototype time was available for Curtiss to re-engine the original Model 75, and a new 850-hp engine; the Wright XR-1820-39 (G5) radial, was fitted and the type designated the Model 75B. The original prototype was later retrospectively designated the Model 75D, but has also sometimes been wrongly named the XP-36.
The Model 75 had a number of features more typical of Northrop designs due to Donovan Berlin, the Chief Engineer, having recently come from that company. One innovative feature was the main landing gear rotating through 90° as it retracted to lay flush in the relatively thin wing section. Other features were fabric covered control surfaces, enclosed cockpit, hydraulic split-flaps, monocoque fuselage construction, and a wing built in two halves and joined at the centre-line. Initial combat fit was two .30 in machine guns in the top engine cowl, but it had no pilot armour or self-sealing fuel tanks fitted. In April 1936 when the competitive assessment was finally done, Seversky's P-35 won the competition. The Curtiss Model 75B had been only able to achieve a top speed of 285 mph at 10,000 ft, in spite of the specification requirement to achieve 294 mph. The USAAC eventually operated a total of 137 of the competing Seversky P-35s before the type was retired from front-line service after being hopelessly outclassed by the Japanese Air Forces during the invasion of the Philippines in December 1941. Although by losing the design competition Curtiss-Wright had missed out on a full production order for pursuit fighters in 1936, they were given a contract to manufacture three further Model 75s for testing and evaluation. These were designated as Model H75E (Army designation Y1P-36) and had 1,050-hp Pratt and Whitney R-1830-13 Twin Wasp radial engines fitted (de-rated to 950 hp). They also had improved pilots' visibility and retractable tail-wheels. This engine installation was very effective, and although being 362 lbs heavier than the earlier 75B (5,437 lbs vs 5,075 lbs gross weight) the first aircraft achieved 294.5 mph at 10,000 ft. The Army were impressed with this performance, and other characteristics of the aircraft, and on the 7th of July 1937, ordered 210 production aircraft - designated the P-36A. This order was worth over four million dollars - the largest fighter order ever placed by the Army Air Corps at that time. The US Government then allowed Curtiss to accept foreign orders and various models of the Model 75 ultimately flew in at least fifteen air forces. A simplified version was developed for export which was based on the Model H75E. It was called the Hawk 75 (Model 75H) - the first model to use the name Hawk - and had fixed undercarriage shrouded in streamlined spats, wing bomb racks and an 875 hp Wright GR-1820-G3 radial engine. The engine could be changed to suit customer requirements, and this model was exported to a number of countries, some of which assembled it under license. During the construction of the Y1P-36s (Model 75E) for the USAAC the Model 75I was also being built. It was a conversion of the prototype 75B aircraft designed to demonstrate an in-line liquid cooled engine. Curtiss was aware that air-cooled radial engines would eventually become limiting so added an Allison V-12 engine (V-1710-11) capable of developing 1,150 hp when supercharged (at 20,000 ft). The resulting prototype fighter exceeded 300 mph, the first US fighter to do so. Test flights began in April 1937, and the Army took delivery of the aircraft as the XP-37 in June. The cockpit was moved back to balance the plane, and other modifications made. It was eventually retired to a mechanics school after 152 flying hours. It cost $104,352 when purchased from Curtiss. Thirteen further test aircraft were ordered as YP-37s. They incorporated changes derived from the XP-37 tersting, including a lengthened fuselage, nose cowling reshaping, a V-1710-21 engine and new supercharger and aerodynamic modifications. The unsatisfactory engine/supercharger performance continued, and all were eventually retired with the highest time aircraft only having logged 212 hours. They had cost $34,481 each.
The fourth P-36A was used for aerodynamic research into streamlining engine cowls around radial engines. By extending the propeller drive shaft, the cowl could be shaped more like that of an in-line engine. This aircraft was designated as the XP-42 (Model 75S) and continued in this research role until scrapped in 1947. The most significant development of the Model 75 was the fitting of an Allison V-1710-19 in-line supercharged engine to the tenth production P-36A as the Model 75P. Redesignated as XP-40 (Hawk 81) this aircraft became the first P-40 Warhawk, a type which was to later play an important role during World War Two. [ Top of Page | Feedback ] Curtiss P-36 The three Y1P-36s (Model 75E) delivered to the USAAC had Pratt and Whitney R-1830-13 Twin Wasp engines, one .50 cal and one .30 cal machine-gun in the cowl with no bulged fairing, view panels behind the cockpit and no cowl flaps. They were valued at $43,432, $43,477 and $73,477 respectively. During the trials at Wright Field they achieved speeds of 294.5 mph at 10,000 ft with 900 hp, and 256 mph with 660 hp at gross weight of 5,437 lbs. The 1050 hp twin Wasps were derated to 950 hp at take off, and a Hamilton Standard constant speed propeller was fitted. At the completion of the test program the three Y1P-36s were re-designated P-36. Two hundred and ten P-36As were ordered by the USAAC with the first delivery in April 1938. These production machines differed from the Y1P-36s by having cowl flaps, bulbous fairings over the nose guns, a Curtiss constant speed propeller and a fully rated Wasp engine. Normal ammunition load was 500 rounds of .30 cal and 200 rounds of .50 cal. With the fully rated engine these aircraft achieved 313 mph at 10,000 ft with a full combat weight. However in little over a year from the first delivery there had been 81 changes to the design giving a gross weight of 5,650 lbs and the maximum available speed at 10,000 was then 300 mph. One hundred and seventy six were completed as P-36As. One of the production P-36As was temporarily converted to trial an 8:1 supercharger gearing modification and designated as P-36B in 1938. It was later returned to its original configuration. Two were converted on the production line to the XP-40 (Model 75P) and XP-42 (Model 75S) respectively. They are described in the Prototype and Development section above. In December 1938 the eighty-fifth P-36A was converted to a prototype P-36C with the addition of a .30 cal gun with 500 rounds to each wing. The ammunition storage was in a slim streamlined magazine projecting underneath the wing and became a visible characteristic of the P-36C. The final 30 aircraft of the original 210 ordered were completed as P-36Cs and were also up-engined to a 1,200 hp Pratt and Whitney R-1830-17 Twin Wasp. Although the gross weight had now climbed to 5,734 lbs, the P-36C could still achieve 311 mph at 10,000 ft.
Three further P-36As were converted for weapons trials. The XP-36D was fitted with 2 .50 cal guns in the nose, each with 400 rounds, and two .30 cal guns in each wing with 500 rounds each. This was the same armament as the Hawk 75A-2. The XP-36E had one .50 cal with 200 rounds in the nose and three .30 cal guns with 500 rounds each in each wing for a total of seven. This aircraft was retired and used for mechanic training after 1942. The final trial aircraft, the XP-36F, was the most heavily armed with the original .50 and .30 cal in the nose, and a Masden 23 mm cannon with 100 rounds mounted in a gondola under each wing. It was only tested briefly before the cannon were removed and it reverted to a P-36A.
The P-36G aircraft were simply redesignated Model 75A-8s originally destined for Norway. The USAAC retained thirty of them, but because of their Wright Cyclone engines they were considered unsuitable for USAAC combat use. Eventually they were transferred to Peru as P-36Gs.
[ Top of Page | Feedback ] Curtiss P-36 Variants These variants were not designated in alphabetical order as they were designed. They are listed here in order of manufacture.
[ Top of Page | Feedback ] Curtiss P-36 Specifications
[ Top of Page | Feedback ] Curtiss P-36 in Operation United States of America The United States Army Air Corps was operating P-36s at the outbreak of the war with Japan. More data will be added at a later stage. Peru P-36s were operated in Peru during and after WWII. [ Top of Page | Feedback ] Curtiss Model 75 Hawk At the same time as Curtiss were preparing the three Model 75E's (Y1P-36) for the USAAC, they were also developing a prototype export model to meet the demand for modern combat aircraft throughout the world. This aircraft differed from the Model 75E by having fixed undercarriage with spats, a variable armament fit, bomb racks fitted, and a Wright 875 hp GR-1820-G3 Cyclone engine. It was marketed as the "Hawk 75" and designated Model 75H by Curtiss. Two demonstrators were built.
The main export model was the Hawk H75A. It had retractable undercarriage and four guns - a nose-mounted .50 cal and.30 cal. and a .30 cal in each wing. This was a weak armament by current European standards, and the Hawk 75A was also relatively slow. However it was maneuverable and of very rugged construction. Two models of each of the Wright Cyclone and Pratt and Whitney Twin Wasp were available for installation. France alone ordered 1,130 Hawk H75As of various models from 75A-1 to 75A-4, although 511 of these were not manufactured due to the German defeat of France. At least 91 further Hawk H75As of various models were built to order for other countries, the designators finally reaching A-9. The sub-types of the Hawk H75A differed in armament fit and engines and are listed on the table below. China, which was already fighting a desperate war against the invading Japanese, showed early interest in the Hawk 75, and purchased one of the demonstration 75Hs, and then ordered more, with delivery starting in May 1938. This order was designated as the Model 75M and 112 were supplied in total. They had fixed undercarriage and two wing mounted .30 cal guns as well as the cowl mounted .50 and .30 cals. Two further demonstrators, designated as Model 75Q, were later built for sale to China, one of them being converted to retracting undercarriage. The Royal Thai Air Force took delivery of twelve Hawk 75s designated as Model H75N. These had an extra pair of .30 cal guns mounted in gondolas outboard of the fixed wheels making six guns in all. The second Hawk 75H demonstrator was purchased by Argentina. They ordered 29 further aircraft which Curtiss designated as Model H75O, and also built twenty under licence. [ Top of Page | Feedback ] Curtiss Model 75 Hawk Variants These variants were not designated in alphabetical order as they were designed. They are listed here in order of manufacture. The prefix "H" was added to export variants.
[ Top of Page | Feedback ] Curtiss Model 75 Hawk Specifications
French Hawks were modified by the installation of FN Browning machine guns, metric instruments, a Munerelle oxygen supply, modified seat backs to fit the French Lemercier back-mounted parachute, a Radio-Industrie 537 radio, a Baille-Lemaire gunsight and reversed throttle controls. All Curtiss Hawks were numbered in a single sequence starting at No. 1 for the first H75A-1, and continuing with No. 101 for the first 75A-2 and 201 for the first 75A-3. H75A-1 100 were ordered, and all delivered. First deliveries were in December 1938. The first sixteen aircraft were tested at Buffalo before dispatch, and then checked on arrival at the SNCAC factory at Bourges. Later aircraft were shipped in a broken down form and assembled by SNCAC. They first entered squadron service in March 1939 with Groupe de Chasse (G.C.) 4 and G.C.5. H75A-2 100 were ordered and all delivered. Deliveries started in May 1939. H75A-3 135 were ordered of which approximately 60 were delivered. Some were delivered to French Morocco and Britain received more than 20 after the French surrender. H75A-4 795 were ordered, of which only 6 reached France before its defeat by Germany. 4 were lost at sea, 17 disembarked in Martinique, and 6 in Guadeloupe in the West Indies. The 23 in the West Indies were eventually shipped to Morocco in 1944 and used there for training by the Free French forces.
Curtiss H75A-1 Hawks of the French Groupe de Chasse II/4 scored the first recorded fighter-to-fighter combat kills on the Western Front in World War Two. On the 8th of September 1939 they flew into battle against a schwarm of Bf 109Es from I/JG53, shot down two 109s, and then forced Oberleutnant Werner Mölders to a forced landing with a damaged engine. The Hawks had opened their account in the west. By the end of 1939 France had ordered over 2,000 aircraft from companies in the United States, among them 1,150 Hawks for operation by the Armée de l'Air. During May 1940, with war looming, France desperately sought more combat aircraft from the United States. However they were informed on the 16th that Curtiss P-36s would not be released to France from US military stocks because the US Army was opposed to it. In the meantime however, on the 18th of May, the US Administration indicated to the British that they were prepared to release some of the 150 P-36s then possessed by the Army Air Corps to the RAF. France was obviously considered a lost cause. When the German forces finally attacked France
in May 1940, only 101 Hawks were operational with four Groupes de Chasse
and some Headquarters flights, all in metropolitan France. They were:
[note that these numbers are those given by Leulliot, 1999. Milde gives figures which are the same in total but distributed differently; GC I/4 32 Hawks (25 operational), GC II/4 32 (22), GC I/5 32 (27) and GC II/5 30 (23).] These four Groupes de Chasse remained operational with Hawks for the entire campaign, and were later joined in operations by G.C. III/2 which had given up their Moraine 406s and re-equiped with Hawks during early June. The performance of the Hawks in comparison to the Luftwaffe's Messerschmitt Bf 109s is open to question. Gunston says that; "they wrote a glorious chapter over France in May 1940", however Terraine considers their effectiveness relative to the Bf 109E fighter to be questionable. They were slower and less effectively armed than the Bf 109E, although their pilots liked them because of their maneuverability and ruggedness. They were able to take considerable punishment in battle and still survive. However, the Hawks certainly performed well against the Luftwaffe bombers. On the first day of the attack on France, GC I/5 shot down eight Dornier Do 17s from KG 3 and GC II/5 shot down three Heinkel He 111s of I./JG53. Between May 10th and June 24th the Groupes de Chasse operating Hawks claimed a total of 230 confirmed and 81 probable kills. These were distributed among the Groupes de Chasse as follows:
The Hawk equipped units performed much better than other French fighter units in May and June 1940. This was, at least in part, because they also had the elite pilots. There were at least six aces in C.G. I/5 alone:
[Perina and Vasatko were both Czechoslovakians who had fled the German invasion of their own country and volunteered for service in the Armée de l'Air.] The Hawk units had performed well and with replacement
aircraft becoming available during the period of fighting, all remained
at nearly full strength when the Armistice was signed. Their status in
June 1940 was:
After the liberation of France in 1945, Hawks continued to operate within the Armée de l'Air. They were being used by the Fighter Training School - Ecole de Chasse - in Morocco in 1945, and later in metropolitan France at Cazaux in 1946. The last Hawk was retired in 1951. Norway H75-A6 Norway first ordered Curtiss Hawks in late 1939. These were engined with the 1200 hp Pratt and Whitney R-1830-SC3-G Twin Wasp, and armed with four 7.9 mm machine-guns. Delivery of the first batch of 12 commenced in February 1940, two months before the German invasion in April 1940. A second order had also been placed for 12 more H75-A6s, but only some of these 24 aircraft arrived before Norway was overrun by German forces. It is thought that 19 H75A-6s had been delivered to the Army's aircraft maintenance base at Kjeller Airfield by the 9th of April when Germany invaded. None of these aircraft were combat-ready and only 6 are believed to have been flyable, although still without weapons. Those capable of flying tried to fly-off to escape bombing, but the field had a packed snow surface which had softened during the day, and as they were not ski-equipped, but had wheeled undercarriage, they were unable to gain flying speed. None were damaged during Luftwaffe attacks so most of the aircraft which had been delivered were captured, some of them still in their shipping crates. Eight of these captured H75-A8s were later supplied to Finland by the Germans. H75-A8 Just before the invasion of Norway, the Government had ordered 36 Hawk H75-A8s, equipped with Wright Cyclone 1200 hp R-1820-G205A engines and two 12.7 mm, and four 7.9 mm machine guns. Delivery could not proceed after Norway was over-run by Germany, and the USAAC requisitioned 30 of them, designating them as P-36G. The remaining six H75-A8s were issued to the Free Norwegian Forces air training facility near Toronto in Canada during February 1941. The H75-A6s which remained undelivered to Norway (probably five) were also used at that facility for fighter pilot training by Norwegian forces. Netherlands H75-A7 The Dutch Government had ordered 20 Hawk H75-A7s with Wright Cyclone 9 R-1820-G205A engines of 1200 hp and 3 x .30 cal and 1 x .50 cal machine guns, but they had not been delivered by the time Germany had invaded. These aircraft were all diverted to the Netherlands East Indies Army Air Corps. Germany Germany captured a number of Hawks and passed some on to Finland to use in combat against the Soviet Union. More data will be added at a later stage. Finland More data will be added at a later stage. Africa, Mediterranean and the Middle East The South African Airforce and the Vichy French operated Hawk 75s in East Africa and Morocco respectively. More data will be added at a later stage. Vichy France (Morocco) More data will be added at a later stage. South Africa More data will be added at a later stage. The China/Burma/India Theatre Hawk 75s flew in combat with the Royal Siamese Air Force, the Royal Air Force in India and the Netherlands East Indies Army Air Force during the early part of the Pacific War. More data will be added at a later stage. Siam (now Thailand) More data will be added at a later stage. China More data will be added at a later stage. Great Britain More data will be added at a later stage. Netherlands East Indies (now Indonesia) More data will be added at a later stage. Other Operators Hawk 75s were supplied to four further Air Forces; those of Argentina, Brazil, Persia and Portugal. Argentina More data will be added at a later stage. Brazil More data will be added at a later stage. Persia (now Iran) More data will be added at a later stage. Portugal More data will be added at a later stage. [ Top of Page | Feedback ] Appendix A: Surviving Examples One Thai Hawk H75N was in the Royal Thai Air Force Museum in Bangkok in 1979. A P-36G was held in the Peruvian Air Force Museum in 1977. [ Top of Page | Feedback ] Appendix B: Production Figures
Numbers in brackets show aircraft converted from an existing airframe.
[ Top of Page | Feedback ] Appendix C: Further Reading and Bibliography Bibliography Aerospace Publishers, 1980, 'Blitzkreig part 7: the race to the channel', in Illustrated Encyclopedia of Aviation, Volume Two, Orbis, London Aerospace Publishers, 1980, 'Curtiss Model 75 (P-36)', in Illustrated Encyclopedia of Aviation, Volume Six, Orbis, London Leulliot, N., 15 February 2000, Armée
de l'Air Order of Battle, 10th May 1940 Leulliot, N., 15 February 2000, Armée
de l'Air Order of Battle, June 1940 Beauchamp, G. and Cuny, J., Curtiss Hawk 75, VIP Publishers, Colorado. Bowers, P.M., 1979, Curtiss Aircraft 1907-1947, Putnam, London. Caven, W.F., and Cate, J.L., editors, 1948-1958, The Army Air Forces in World War II, Volume One, Plans and Early Operations, January 1939 to August 1942, Office of Air Force History, Washington. Cull, B., Lander, B. and Weiss, H., 1995, Twelve Days in May, Grub Street, London. Cuny, J. and Danel, R., 1974, L'Aviation de Chasse Française, 1918-1940, Docavia, Paris. Dias da Cunha, R., 10 April 2000, História
da Força Aérea Brasileira, the Curtiss P-36 in FAB Service
Ehrengardt, C-G. and Shores, C., 1983, L'aviation de Vichy au Combat, Vol.1: Les Campagnes Oubliées, Lavauzelle, Paris. Ganszauge, M. and Ripatti, P., 16 May 2000, Curtiss
Hawk 75A (P-36) Green, W., 1960, Warplanes of the Second World War, Volume Four, Fighters, Hanover House, New York. Gunfeldt, C., 1990, Fornebu .9 April, Wings, Oslo. Gunston, W., 1976, Encyclopedia of the World's Combat Aircraft, Salamander, London. Hall, H.D., 1955, North American Supply, History of the Second World War, United Kingdom Civil Series, Her Majesty's Stationary Office, London. Hooton, E.R., 1994, Phoenix Triumphant: the rise and rise of the Luftwaffe, Arms and Armour Press, London. Hsu, L. and Chang, M., 1971, History of the Sino-Japanese War (1937-1945), Chung Wu Publishing Co., Taipei. Jervås, B., 16 May 2000, Norwegian
Aircraft in 1940 Long, J., 16 May 2000, Curtiss
H-75A Hawk Martin, P., 1991, Invisibles Vainqueurs: Exploits et Sacrifice de l'Armee de l'Air en 1939-1940, Editions Yves Michelet, Paris. Milde, J-P., 2000 update, "Curtiss
H75A", in The French Campaign Milde, P., 7 March 2000, Personal Communication. O'Hara, D.P., 16 May 2000, The
Royal Thai Airforce, 1940-41 Prasad, B, editor, 1956, Expansion of the Armed Forces and Defence Organisations, Official History of the Indian Armed Forces in the Second World War 1939-45, Orient Longmans, Rawlings, J., 1969, Fighter Squadrons of the RAF and their Aircraft, McDonald, London. Swanborough, G. and Bowers, P.M., 1989, United States Military Aircraft Since 1909, Putnam, London. Terraine, J., 1997, The Right of the Line, Wordsworth Editions Limited, Ware. Thornburg, C, 30 January 2000, The
World's Airforces Further Reading Keskinen, K., Stenman, K. & Niska, K. 1975: Suomen Ilmavoimien historia 5. Curtiss Hawk 75 A. P-40M. Tietoteos, Espoo, Finland. Beauchamp, G., 1985, Mowhawks over Burma, Canada's Wings, Ontario. [ Top of Page | Feedback ]
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