Curtiss P-36A

The Curtiss P-36 was the first of the new generation of monoplane fighters to enter service with the USAAC. It was a contemporary of the Supermarine Spitfire, the Hawker Hurricane, and the Messerschmitt Bf 109, all of which were introduced within a few months of each other in the mid 1930s. Even though the P-36 owed very little to previous Curtiss biplane pursuits, the name *Hawk* was still generally applied to the aircraft.

The P-36 pursuit had its origin in the Model 75 project which was originally developed as the Curtiss entry in the US Army pursuit aircraft competition scheduled for May 1935. Curtiss lost the initial contest but was the real winner in the end, with 227 examples sold to the USAAC, 753 exported, and at least 25 built under license in other countries.

The Model 75 owed relatively little to previous Curtiss designs. The principal designer was Donovan A. Berlin, who had come over to Curtiss from Northrop, and the structure of the Model 75 was heavily influenced by earlier Northrop designs. The prototype carried the civilian registration of X-17Y. The Model 75 was an all-metal low-wing monoplane, with the metal-frame moveable control surfaces being fabric covered. The cockpit was enclosed by a sliding canopy, with the canopy being faired into a high rear turtledeck. Both the main undercarriage units and the tailwheel retracted, the main legs rotating backward 90 degrees and turning 90 degrees on their axes simultaneously to lay the wheels flat in the thin rear portion of the wing. This retraction mechanism had originally been developed by Boeing, which received a royalty whenever any other aircraft manufacturer used it. The wing was built in two halves joined on the aircraft's centerline. Portions of the outer wing structure were sealed to provide flotation in case of a forced landing in water. Hydraulically-actuated split flaps were fitted to the trailing edge of the wing. Initial armament was the standard US fighter armament of the time--one 0.30-in and one 0.50-in machine guns under the forward fuselage deck, firing through openings in the top of the cowling. No armor protection or self-sealing fuel tanks were fitted.

Prototype construction began in November 1934. Initially, the aircraft was powered by the unfortunate 900 hp Wright XR-1670-5 (SCR-1670-G5) twin-row air-cooled radial. The first flight of the Model 75 took place in May of 1935. During early tests, the prototype had demonstrated a maximum speed of 281 mph at 10,000 feet, a service ceiling of 30,000 feet, and a range of 537 miles. Weights were 3760 lbs empty, 4843 lbs gross. Length was 28 feet 3 1/2 inches, wingspan was 37 feet 0 inches, and wing area was 237 square feet.

On May 27, 1935, Curtiss submitted the Model 75 to the USAAC Material Division's single seat fighter competition which was to be held at Wright Field that very month. However, the Model 75 was the only competitor ready in time for the scheduled flyoff. The primary competitor, the two-seat Seversky SEV-2XP, had been "heavily damaged" during delivery to Wright Field, and did not arrive there until June 18. The SEV-2XP was soon returned to the Seversky factory where it was reworked into a single seater with retractable undercarriage. The competition was delayed until the SEV-1XP could be ready. It finally arrived at Wright Field on August 15, bearing the designation SEV-1XP. The only other serious competitor, the Northrop 2A had taken off on its maiden flight on July 30, headed out over the Pacific, and promptly disappeared into thin air, never to be seen again.

Curtiss protested that this delay had given the Seversky competitor an unfair advantage, and convinced the Army that it should defer its decision until after a further competitive evaluation which was to take place in April of 1936. During the early flight tests, the XR-1670-5 engine which powered the Model 75 had proven itself to be totally unsatisfactory. Don Berlin took the opportunity afforded by the delay to replace this engine by a 700 hp Pratt & Whitney R-1535. Since this engine model had passed its peak of development, a nine-cylinder single-row Wright XR-1820-39 (G5) Cyclone radial was quickly substituted. This engine was rated at 950 hp for takeoff and at 850 hp normal maximum output. With this engine, the prototype was designated Model 75B (Model 75A had been reserved for the export version of the Hawk). In its final form, the Model 75B had a strengthened cockpit canopy and introduced a scalloped aft fuselage decking behind the cockpit for a somewhat improved rear view.

The new Cyclone radial of the Model 75B proved to be almost as unsatisfactory as its R-1670 predecessor, and failed to deliver its full rated power. There were no fewer than four engine changes during the Wright Field trials. In addition, there were problems with incompatibility between the engine and the airframe. The Model 75B proved capable of attaining only 285 mph (versus the 294 mph at 10,000 feet guaranteed by Curtiss-Wright). Even though the Seversky entry also fell short on promised performance and in addition was more expensive than the Curtiss entry, the Model 75B lost out to the Seversky competitor, which won an order for 77 examples under the designation P-35.

Even though the prototype Model 75 never became Army property, some sources refer to the various configurations of this aircraft under the collective designation "XP-36". This was a matter of historical convenience only, since there never was any such official designation. The original configuration of the Model 75 prototype with the 900 hp Wright SCR-1670-G5 radial was given the retroactive company designation of Model 75D. The prototype aircraft was later rebuilt and delivered to the Army as the XP-37, of which more in a later installment.

On June 16, 1936, Curtiss got a consolation order from the Material Division for three examples of the Model 75B under the designation Y1P-36, perhaps because the USAAC was getting nervous about the inability of Seversky to meet its delivery schedules and was therefore hedging its bets. Serial numbers of the Y1P-36s were 37-68/70, and the company designation for these planes was Model 75E. At Army direction, they were to be powered with the Pratt & Whitney R-1830-13 Twin Wasp radial, virtually the same type of engine that was used by the P-35. The Twin Wasp was rated at 900 hp at 2550 rpm at 12,000 feet, having been de-rated from 1050 to 950 hp for takeoff. The engine drove a hydraulically-operated, constant-speed three-bladed Hamilton Standard propeller. Armament was the Army standard of the day, one 0.30-inch and one 0.50-inch machine gun under the cowling and synchronized to fire through the propeller arc. The Y1P-36 could be distinguished from the prototype by the R-1830 engine and also by the presence of modified and larger view scallops behind the cockpit.

The first Y1P-36 was delivered to the Army in March of 1937, and was tested at Wright Field in June of that year. The Wright Field test pilots were uniformly enthusiastic about the new Curtiss plane, commenting favorably about its maneuverability. The effectiveness and operation of all controls throughout the speed range of the fighter were excellent, and stability and ground handling were quite favorably rated. However, there was some criticism of the location of the undercarriage and flap controls, some complaints about the cabin ventilation, and some unfavorable comments about the curvature of the windshield which resulted in some distortion of vision during landing. With the R-1830 engine, the Y1P-36 did so well that it won a 1937 Army competition, and on July 7, 1937, the Army ordered 210 P-36As, the largest single US military aircraft order since the First World War. Curtiss's private venture had finally paid off.

Serials of the P-36As were 38-1/210. The principal difference between the P-36A and the Y1P-36 was the addition of engine cowl flaps and the addition of bulging "frog's eye" covers over the machine gun ports in the engine cowling. The P-36A had a fully-rated 1050 hp Pratt & Whitney R-1830-13 Twin Wasp engine driving a Curtiss Electric constant speed propeller. Empty and normal loaded weights were 4567 lb and 5470 lbs. Maximum speed was 300 mph at 10,000 feet. Normal range was 825 miles. Initial climb rate was 3400 feet/minute. An altitude of 15,000 feet could be attained in 4.8 minutes, and service ceiling was 33,000 feet.

Before completion, P-36A Ser No 38-10 was converted to the XP-40 (Model 75P) and 38-4 became the XP-42 (Model 75S). More of both of these later in the series!

The first Y1P-36 (Ser No 37-068) was briefly tested with two twin-bladed contrarotating propellers, the first such installation on an American aircraft.

The first production P-36A was delivered to Wright Field in April of 1938. The 20th Pursuit Group at Barksdale Field, Louisiana, comprising the 55th, 77th, and 79th Pursuit Squadrons, had been designated as the first recipients of the new Curtiss fighter, and they had relinquished their Boeing P-26s in anticipation of the deliveries of the new fighter. However, the new Curtiss fighters began to encounter an extensive series of teething troubles almost as soon as they reached the field. Severe skin buckling in the vicinity of the landing gear wells had appeared, dictating increased skin thicknesses and reinforcing webs. Engine exhaust difficulties and some weaknesses in the fuselage structure were also encountered. Despite both production line and field fixes, the P-36As were grounded again and again. At one time, the 20th Pursuit Group was down to six serviceable P-36As, and even these planes had to be flown under severe limitations on their speed, aerobatics, and combat maneuvers.

The 1st Pursuit Group at Selfridge Field, Michigan, consisting of the 17th, 27th, and 94th Pursuit Squadrons, had also been scheduled in 1938 for conversion to the P-36A. However, this Group was forced to await the efforts being made at Buffalo to wring out the new fighter's problems. In the event, only the 94th Squadron got any P-36As during 1938, operating them along with Seversky P-35s. The 27th Squadron received a few P-36As during early 1939, but neither the 27th nor the 94th Squadron ever got a full complement of P-36As, the balance being made up by Seversky P-35s. The 17th Squadron never got ANY P-36s, their strength being made up solely of P-35s.

In 1939, the 33rd, 35th, and 36th Squadrons of the 8th Pursuit Group at Langley Field, Virginia were equipped with P-36s.

By early 1941, the P-36 was already recognized as being obsolescent, and had been largely supplanted in first-line Army Air Force (as the Army Air Corps had been renamed) units by such aircraft as the Bell P-39 Airacobra and the Curtiss P-40. At home, the P-36s were largely relegated to training units. By the time of Pearl Harbor, P-36s were serving with the 35th Training Group based at Moffett Field, California and with the 36th Training Group based at Langley Field, Virginia. These outfits trained with the P-36 before they converted to more modern fighters. Other P-36s were transferred overseas. P-36s served with the 24th, 29th, and 43rd Squadrons of the 16th Pursuit Group and with the 51st, 52nd and 53rd Squadrons of the 32nd Pursuit Group, both groups being based at Albrook Field in the Canal Zone, where they flew alongside the now totally-obsolete Boeing P-26. During February of 1941, 20 crated P-36s were delivered to Alaska, and these planes served with the 23rd Squadron at Elmendorf Field in Alaska. At about the same time, 31 P-36s arrived in Hawaii from San Diego aboard the carrier *Enterprise*. These fighters entered service with the 78th Squadron of the 18th Pursuit Group and with the 46th and 47th Squadrons of the 15th Pursuit Groups, all being based at Wheeler Field, Hawaii.

At the time of the Pearl Harbor attack on December 7, 1941, 14 P-26As, 39 P-36As and 99 P-40s comprised the air defense of the islands. Most of these aircraft were destroyed or damaged on the ground, but four P-36As of the 46th Squadron managed to take off and attack a formation of nine Nakajima B5N1 torpedo bombers on the second wave. Two of the Najajimas were shot down, gaining the first USAAF "kills" of the Pacific War.

After Pearl Harbor, there was no other combat while in US service. P-36s were quickly withdrawn from combat outfits and relegated to training units. Ten P-36As (serials 38-39, 43, 51, 53, 54, 60, 106, 158, 159, and 175 were transferred to Brazil in March of 1942.

There is a P-36A on display at the Wright Patterson Air Force Base Museum in Dayton, Ohio. I am unaware of the service history of this particular airplane.

Curtiss P-36B
P-36A Ser No 38-020 was flown in November 1938 with an R-1830-25 engine offering 1100 hp for takeoff. This airplane was redesignated P-36B. It attained a maximum speed of 313 mph. The airplane was subsequently converted back to P-36A standards.

Curtiss P-36C
The P-36A had always been underarmed in comparison with contemporary foreign fighters (e. g. the Spitfire and Hurricane), and P-36A Ser No 38-085 had undergone an experiment in which the fuselage guns were supplemented by the addition of a 0.30-in machine gun in each outer wing panel. This installation was successful, and it was adopted for the last 30 aircraft in the original order (Ser Nos 38-181/210). These were redesignated P-36C. The P-36C also featured an R-1830-17 (S1C3-G) engine rated at 1200 hp for takeoff. These changes had been ordered on January 16, 1939, and the P-36C could be distinguished from the P-36A by the addition of cartridge case retainer boxes protruding underneath the wings. Despite the extra drag produced by the underwing cartridge boxes and the increased weight, the increased power of the engine raised the maximum speed of the P-36C to 311 mph, although the range was lowered to 600 miles. Service ceiling was 33,700 feet. Weights were 4620 lbs empty, 5734 lbs loaded. Wing span was 37 feet 4 inches, length was 28 feet 6 inches, and wing area was 236 square feet.

Curtiss XP-36D
P-36A Ser No 38-174 was withdrawn from squadron service early in 1939 and fitted with four belt-fed 0.30-in machine guns in the wings. At the same time, the fuselage mounted armament was changed to a pair of 0.5-in machine guns. Thus armed, the modified aircraft was redesignated XP-36D.

Curtiss XP-36E
P-36A Ser No 38-147 was fitted with new outer wing panels each housing FOUR 0.30-in machine guns (a la Spitfire and Hurricane). The fuselage-mounted 0.50-in gun was retained but rendered inoperable. As such, the aircraft was redesignated XP-36E. The XP-36E was retired to an Army mechanics' school in August of 1943.

Curtiss XP-36F
The XP-36F was created by taking P-36A Ser No 38-172 and fitting it with two 23-mm Danish-built Madsen cannon in underwing fairings. The standard P-36A fuselage armament was retained. Unfortunately, this additional armament caused the maximum weight to rise to 6850 pounds and the maximum speed to fall to 265 mph. Consequently, the experimental armament was soon removed and the airplane reverted to a standard P-36A. It was surveyed in October 1944.

Curtiss P-36G
The Norwegian government had issued an order for 36 Hawk 75A-8 export versions of the P-36 just before the German occupation. These aircraft were powered by the export-model 1200 hp Wright R-1820-G205A Cyclone radial. Since Norway was under German occupation at the time these aircraft were completed in January of 1941, they were impounded by the US government.

These 36 planes were delivered to Free Norwegian forces in Canada in February of 1941, where they were operated as fighter trainers by the "Little Norway" training establishment near Toronto. They were used as advanced trainers for Norwegian fighter pilots after their initial training on Cornells and Harvards.

The training on the Hawk 75A-8s was halted in early 1943, and the 30 survivors were sold, 18 to Curtiss and 12 to the USAAF. All 30 of these planes were redesignated P-36G and were assigned the USAAF serial numbers 42-36305/36322 and 42-108995/109006. The export-model Wright R-1820-G205A Cyclone radial engine which powered these planes was redesignated R-1820-95 by the Army.

Since these aircraft were considered useless as combat types and in addition were incompatible with other P-36s because of their Wright engines, the P-36Gs were sent to Peru under Lend-Lease in 1943. One survives in the Peruvian Air Force Museum.

Curtiss Model 75A Demonstrator

Model 75A was the company designation for a Curtiss-owned demonstrator which carried a civilian registration of NX22028. This demonstrator aircraft was used to carry out several company-originated experiments. First, it was fitted with an external mechanical supercharger mounted underneath its Pratt & Whitney R-1830 engine and briefly designated Model 75J. Then, it was experimentally fitted with a turbosupercharged R-1830-SC2-G engine. The supercharger was fitted underneath the nose just aft of the engine cowling, and the intercooler was mounted underneath the trailing edge of the wing. The company designation for this modification was Model 75R. Empty and normal loaded weights went up to 5074 lbs and 6163 lbs. During trials in January 1939, it attained a maximum speed of 330 mph at 15,000 feet. However, the poor reliability and complexity of the turbosupercharger led the USAAC to decide not to proceed with a supercharged variant of the P-36, choosing instead to purchase the turbo-supercharged Seversky (Republic) XP-41, which had been converted from the last P-35. After trials at Wright Field, the aircraft was returned to the Curtiss plant in Buffalo, where it was fitted with a Wright R-1820 engine and resumed its role as a demonstrator.

Curtiss Hawk with Armee de l'Air

Although the P-36 saw very little combat in American hands, the Curtiss fighter was to see quite a bit of combat in foreign hands. In fact, it is one of the few military aircraft actually to see combat on BOTH sides during the Second World War.

The largest foreign operator of the Hawk was the Armee de l'Air, the French Air Force. Next to the Morane-Saulnier M.S.406, the Curtiss Hawk was numerically the most important fighter in French service during the German onslaught into Western Europe in May of 1940.

In February 1938, two months before the first P-36A had rolled off the Buffalo assembly lines for the USAAC, the French government entered into negotiations with the Curtiss company for the supply of 300 fighters of the Hawk 75A type which Curtiss had offered to the Armee de l'Air. The Hawk 75A was an export version of the P-36A, and was being offered for sale with either the Pratt & Whitney Twin Wasp or the Wright Cyclone engine.

However, the unit price asked by Curtiss was considered exorbitant by the French--almost twice as high as that of the Morane-Saulnier M.S.406. In addition, the proposed delivery schedule commencing in March of 1939 with 20 planes and continuing at a rate of 30 planes per month was considered totally unacceptable. Furthermore, the USAAC was itself unhappy with the Curtiss company's inability to meet delivery schedules for its P-36As, and felt that the French sale would only slow things up still more. Consequently, the USAAC opposed the French sale.

Nevertheless, the rapidity of German rearmament made the modernization of the Armee de l'Air's equipment a matter of the utmost urgency, so the French persisted with the negotiations. As a result of the direct intervention of President Roosevelt, a leading French test pilot, Michel Detroyat was permitted to fly a Y1P-36 service test prototype at Wright Field in March of 1938. He submitted a thoroughly enthusiastic report. In addition, Curtiss suggested that more acceptable delivery schedules could be offered if the French government would finance the construction and equipping of supplementary assembly facilities.

The French still felt that the unit price was too high, and on April 28, 1938 they decided to delay their decision until the completion of the test trials of the Bloch MB-150, the quoted price of which was scarcely half that of the Curtiss fighter. However, the MB-150 was suffering an extensive series of teething troubles (the first prototype couldn't even fly!) and had been subjected to a succession of modifications for nearly two years. By mid-1938, it was felt that the Bloch fighter's main problems had been overcome. However, it was soon realized that in order to adapt the design for mass production, a complete structural redesign would have to take place.

The rework of the Bloch MB-150 would obviously be a costly and time- consuming process, and time was something the Armee de l'Air did not have. Consequently, on May 17, 1938 the Minister for Air announced that the French would acquire the Curtiss Hawk, and that a French purchasing commission was instructed to order 100 Hawk airframes and 173 Pratt & Whitney R-1830 Twin Wasp engines. The contract stipulated that the first Hawk should be flown at Buffalo by November 25, 1938 and that the 100-th plane should be delivered by April 10, 1939.

Hawk 75A-1
The initial production version of the Hawk was designated Hawk 75A-1 by Curtiss, of which 100 had been ordered by France. According to the original plan, the majority of the Hawk 75A-1s were to be shipped by Curtiss in disassembled form to France, with assembly being completed in France by the Societe Nationale de Constructions Aeronautiques du Centre (SNCAC) at Bourges. The first Hawk 75A-1 was flown at Buffalo early in December 1938, only a few days after the committed date. The first Hawk 75A-1s (actually the fourth and fifth examples off the line) were delivered by ship to France on December 14, 1938. Fourteen more Hawk 75A-1s were delivered in fully-assembled form for Armee de l'Air trials, but the rest were delivered in disassembled form. The first assembly was commenced by SNCAC in February 1939.

During March and April of 1939, the 4e and 5e Escadres de Chasse had initiated conversion from the Dewoitine 500 and 501, and by July 1, 1939 the 4e Escadre had 54 Curtiss fighters on strength and the 5e Escadre had 41. The conversion had not been without problems, one Hawk 75A-1 having crash- landed when an over-speeding propeller had caused the engine to overheat, and another one had been destroyed in a fatal crash as a result of a flat spin that developed during aerobatic trials with full fuel tanks. Throughout the entire service history of the Hawk 75A, there were problems with maneuverability and handling when all the fuel tanks were completely full.

The Hawk 75A-1 was powered by the Pratt & Whitney R-1830-SC-G engine, with an international rating of 900 hp at 12,000 feet and 950 hp for takeoff. Armament comprised four 7.5 mm machine guns, two mounted in the upper decking of the fuselage nose and two in the wings. Apart from the altitude indicator, all instruments were metric calibrated. A modified seat was fitted to accommodate the French Lemercier back parachute. The throttle operated in the "French fashion", i.e. in the reverse direction to the throttles of British or US aircraft.

France used the manufacturer's model number as the official designation, and numbered the aircraft consecutively within the model. This information appeared in three lines on the rudder as so:

CURTISS H75-C1 No. 09
The C stood for Chasse (pursuit) and the 1 indicated a single-seater, and the 09 was the ninth H75 ordered by France.

Hawk 75A-2

Following the placing of the initial French order for the Hawk 75A in May of 1938, an option had been taken for 100 more machines. This option was converted into a firm order on March 8, 1939. These aircraft differed from the A-1 in having an additional 7.5 mm machine gun in each wing, some structural reinforcement of the rear fuselage, and the minor modifications necessary to permit interchangeability between the R-1830-SC-G and the more powerful R-1830-SC2-G, the latter affording 1050 hp for takeoff.

The new model was designated Hawk 75A-2 by Curtiss. The four wing guns and the new engine made the Hawk 75A-2 more or less equivalent to the US Army's XP-36D. The first A-2 was delivered to France at the end of May, 1939. The first 40 of these were basically similar to the A-1 in both powerplant and armament. The first A-2 to have both the uprated engine and the increased armament was actually the 48th off the Buffalo line. French Air Force numbering continued from the Hawk 75A-1, the first Hawk 75A-2 being numbered 101.

Hawk 75A-3
One hundred and thirty-five of the Hawk 75A-3 version were ordered by France on October 9, 1939, with improved 1200 hp R-1830-S1C3G engines and armament similar to that of the A-2 (six 7.5-mm machine guns). Maximum speed was 311 mph at 10,000 feet. Initial climb rate was 2350 feet per minute, service ceiling was 33,700 feet, and range was 820 miles. Wingspan was 37 feet 3 1/2 inches, length was 28 feet 7 inches, and wing area was 236 square feet. Weights were 4483 lbs empty, 5692 lbs gross. About sixty Hawk 75A-3s reached France before the surrender, with the rest being diverted to Britain.

Hawk 75A-4
The last French order before the Armistice was for 395 Hawk 75A-4 aircraft. These were armed like the A-3s but were fitted with 1200 hp Wright R-1820-G205A Cyclone engines. Cyclone-powered 75s could be distinguished from Twin Wasp models by their short-chord cowlings of slightly greater diameter and by the absence of engine cowling flaps and bulbous nose gun port covers. Maximum speed was 323 mph at 15,100 feet. Initial climb rate was 2820 feet per minute, service ceiling was 32,700 feet, and range was 670 miles. Weights were 4541 lbs empty, 5750 lbs gross. Wingspan was 27 feet 3 1/2 inches and length was 28 feet 10 inches. Only two hundred and eighty-four of these A-4s were actually built, and of these, only six A-4s actually reached France before the surrender.

Action with Armee de l'Air
The French Hawks were in action from almost the first day that the war began in Europe. On September 8, 1939, the Groupe de Chasse II/4, operating Hawk 75As succeeded in destroying two Messerschmitt Bf 109Es, the first Allied aerial victories of World War 2. However, during the invasion of France in May of 1940, the Hawks were generally outmatched by the Messerschmitt Bf 109E. The Hawk 75A served with Armee de l'Air Groupes de Chasse III/2, I/4, II/4, I/5 and II/5, these units claiming 230 confirmed kills and 80 "probables", as against losses totaling only 29 aircraft destroyed in aerial combat. Although these figures are probably over-optimistic, it seems likely that the French Hawks gave better than they got. The Hawk 75A was neither as fast nor as well-armed as the Messerschmitt Bf 109E, but it was more maneuverable and could take more punishment. The leading French ace of 1939/40 was Lt Marin La Meslee, who scored 20 "kills" while flying the Hawk.

Only 291 Hawk 75A fighters were actually taken on strength by the Armee de l'Air before the collapse of French resistance, but a number were lost en route to French ports. As mentioned before, only six A-4s actually reached France before the Armistice. Thirty A-4s destined for France were lost at sea during transit, seventeen were disembarked in Martinique and a further six were unloaded in Guadeloupe. These machines were, incidentally, shipped from the West Indies to Morocco during 1943-44, placed in flying condition and used for training, their unreliable Cyclone 9 engines being replaced by Twin Wasps. The rest of the French Hawk 75A-4 order was taken over by Britain as Mohawk IVs.

After the collapse of French resistance, those Armee de l'Air Hawks which had not escaped to unoccupied French territory or flown to England were taken over by the Luftwaffe. Some of the Armee de l'Air Hawk 75As were captured while still in their delivery crates. These were transported to Germany, whey they were overhauled and assembled by the Espenlaub Flugzeugbau, fitted with German instrumentation, and then sold to Finland. Finland received 36 former Armee de l'Air Hawk 75A-1s, A-2s and A-3s, along with eight former Norwegian Hawk 75A-6s. These Finnish Hawks participated in the war on the Axis side when Finland entered the war against the Soviet Union on June 25, 1941. These Hawks gave a good account of themselves in Finnish service, and some Hawks remained in service in Finland until 1948.

After the Armistice, Armee de l'Air Groupes de Chasse I/4 and I/5 continued flying their Hawks with the Vichy Air Force, the former unit based at Dakar and the latter at Rabat. These Vichy Hawk 75As were to fight against other American planes when the Allies made the Operation Torch landings in North Africa in November 1942. In an air battle between these Hawks and carrier-based Grumman F4F Wildcats, 15 Vichy planes were shot down versus the loss of seven Wildcats. This is one of the few occasions during the Second World War in which American-built planes fought against each other.

RAF Mohawk

Considerable interest in the Hawk had been aroused in Britain as a result of a test flight carried out with an Armee de l'Air Hawk by an RAF pilot in France. The Hawk 75A possessed remarkably good controls and the ailerons were fairly light at high speeds in contrast with the early Spitfire which had ailerons which were almost immobile at speeds over 300 mph. At the end of 1939, the Royal Aircraft Establishment arranged for a loan of a Curtiss Hawk from France (the 88th production Hawk 75A-2) for comparative trials against a Spitfire I (K9944). In many respects, the Hawk turned out to be superior to the Spitfire. The RAE found that the Hawk did indeed have exceptional handling characteristics and beautifully harmonized controls. In a diving attack at 400 mph, the Hawk was far superior to the Spitfire I owing to its lighter ailerons. In a dogfight at 250 mph, the Hawk was again superior, because its elevator control was not over-sensitive and all-round view was better. However, the Spitfire could break off combat at will because of its much higher speed. When the Spitfire dived on the Hawk, the Curtiss could avoid its opponent by banking and turning rapidly. The Spitfire could not follow the Hawk around and would overshoot the target. The Hawk 75A displayed appreciably superior take-off and climb characteristics. The swing on takeoff was smaller and more easily corrected than on the Spitfire, and during the climb the Hawk's controls were more effective. However, the Hawk tended to be rather slow in picking up speed in a dive.

Based on these trials, the British government briefly toyed with the idea of ordering the Hawk for the RAF. For whatever reason, these plans were never carried out. However, the fall of France in June 1940 caused quite a few Hawks to fall into British hands.

Those Hawk 75As which had not yet been delivered to France before the surrender (most of them A-4s), plus those whose pilots had flown them to England to escape the German occupation were taken over by the RAF and given the name Mohawk. The total number of Mohawks impressed by the RAF was 229 planes. Most of them were former French machines, but a few former Persian Hawks and even some Indian-built machines were included in the Mohawk total as well.

There were four RAF sub-variants: Mohawk I, II, III, and IV.

Former French Hawk 75A-1s were named Mohawk I by the RAF, with Hawk 75A-2s being named Mohawk II. There was a total of 29 of these planes. Unfortunately, it is difficult to track which planes were A-1s and which were A-2s, since Mohawk I and Mohawk II aircraft were intermixed with each other and with Mohawk IVs in the RAF serial number blocks AX880/898, BK876/879, and BL220/223.

More than 20 former French Hawk 75A-3s were taken over by Britain as Mohawk IIIs. RAF serials for these Mohawk IIIs were BK569/588, but some A-3s were mixed in with Mohawk IVs in serial block AR630/694.

The name Mohawk IV was assigned to the remainder of the French Hawk 75A-4 order which was taken over by the RAF. The exact number of Mohawk IVs diverted to Britain cannot be determined from the RAF serial numbers alone, since some blocks applied to both IIIs and IVs without distinction. The total number of Mohawks appearing as IVs total 190, only six less than the total of Hawk 75A-4s built. However, some 75As other than A-4s became Mohawk IVs, including the ten A-9s originally intended for Persia and at least six of the former Chinese A-5s assembled in India. Mohawk IV RAF serials of record are AR630/694, BB918/937, BB974/979, BJ434/453, BJ531/550, BJ574/588, BK876/879, BL220/223, BS730/738, BS744/747, BS784/798, BT470/472, LA157/158 and LA163/165.

Mohawks taken on strength by the Royal Air Force were refitted with British equipment, including 0.303-calibre Browning machine guns. The French throttles were replaced by throttles which operated in the "British fashion", i.e., were pushed forward to increase the power. The RAF decided that its Mohawks were not suitable for the European theater, and sent 72 of them to the South African Air Force (where they were flown by the 3rd, 4th, 5th, 6th and 7th Squadrons which operated in East Africa), while others were flown by the 5 and 155th RAF squadrons based in India. At one time, eight Mohawks provided the sole fighter defense of North-East India, and the fighter remained operational on the Burma front until finally replaced by more modern types in December 1943.

12 Mohawks were sent to Portugal.

Hawk 75A-5 for China

The Hawk 75A-5 was the Curtiss company designation for a Cyclone-powered model which was to be assembled in China by the Central Aircraft Manufacturing Company (CAMCO). At least one complete airplane and some kits of unassembled parts were delivered to China. After assembling some aircraft in China, the CAMCO firm was reorganized as Hindustan Aircraft Ltd. in Bangalore, India. In April 1941 the Indian government placed a contract with Hindustan for the construction of 48 Cyclone 9-powered Hawk 75As, together with the necessary spares. Hindustan acquired a manufacturing license from Curtiss, and the first Indian-built machine flew on July 31, 1942. However, shortly after this flight, a change in policy resulted in the decision to abandon the construction of complete aircraft in India. After four more machines were constructed, the Hindustan program was terminated. These Indian-built machines were eventually absorbed into the RAF as Mohawk IVs.

Hawk 75A-9 for Iran
The government of Persia (now Iran) ordered ten Hawk 75A-9 versions powered by Wright R-1820-G205A engines. These reached Persia shortly before that country was occupied by British and Russian forces on August 25, 1941. The Hawk 75A-9s were discovered there still in their shipping crates. These aircraft were taken over by the British from Persia and were transferred to India as Mohawk IVs, where they were operated by the 5th Squadron of the RAF.

Hawk 75A-6/75A-8 for Norway
In the autumn of 1939, the Norwegian government ordered twelve Hawk 75A-6s with 1200 hp Pratt & Whitney R-1830-S1C3G Twin Wasp radials and four-gun armament. This order was later supplemented with an order for twelve more, to bring the total to 24.

Deliveries began in February 1940. By the time of the German invasion in April of 1940, 19 planes out of the 24 had arrived in Norway. However, none of these planes were ready for combat, and did not participate in the vain attempt to stop the German advance. 7 of the 75A-6s were assembled and were based at Kjeller Airfield close to the capital at Oslo. Not all of these planes had their guns installed, and the ones that did had guns that were not calibrated. Secondly the airplanes at Kjeller Airfield were equipped with wheels and the winter of 1940 was not quite over and the airfield was still covered with snow - enabling only ski equipped aircraft to take off. The other 12 airplanes that also had arrived in Norway were still sitting in the customs building down at the harbour. Recognizing that the planes in storage would likely soon fall into German hands, an employee decided singlehanded to crush all the instruments with a hammer and to cut all visible wires with a wire cutter. The last 5 aircraft from the first order of Hawks were underway by sea to Norway as the war broke out. They were redirected to England and were later given to France.

The Norwegian Hawk 75A-6s were captured by the Germans and were delivered to Finland. These were later supplemented by 36 partially-completed Hawk 75As that had been seized by German forces from France at the time of the Armistice and assembled in Germany. These participated in the war on the Axis side when Finland entered the war against the Soviet Union on June 25, 1941. These gave a good account of themselves, and some Hawks remained in service in Finland until 1948.

Norway had ordered an additional 36 Hawk 75A-8s with 1200 hp Wright R-1820-G205A Cyclone engines just before the German occupation. The German occupation caused the A-8s to be impounded by the US government before delivery. . A Norwegian financed training base known as "Little Norway" had been established at Toronto in Canada, and the airplanes were sent here. Here, they were used as advanced trainers for the coming Norwegian fighter pilots after their initial training on Cornells and Harvards. The advanced training on the A-8s was stopped in early 1943 and the surviving 30 aircraft were sold in May of 1943. 18 went back to Curtiss and 12 went to the US government. They were redesignated P-36G and were assigned USAAF serials 42-36305/36322 and 42-108995/109006.

Hawk 75A-7 for Netherlands
Twenty Hawk 75A-7s with Cyclone engines were ordered by the Netherlands, but the German occupation of Holland caused all of the A-7s built to be diverted to the Netherlands East Indies starting in May 1940. They served with the 1st Squadron of the Royal Netherlands East Indies Army Air Corps, where they were caught up in the Japanese advance from December 8, 1941. They were outnumbered and outperformed by the nimble Japanese Zero fighter. By February 1, 1942, they had all been destroyed by the enemy.

Simplified Hawk

Early in 1937, Curtiss began the development of a simplified version of the Y1P-36 intended specifically for export. Curtiss was aware that some potential customers whose air arms operated under relatively primitive conditions would look askance at a sophisticated feature such as a retractable undercarriage which promised to afford difficult maintenance problems. The "simplified Hawk" project was given the company designation of Model 75H.

The construction of the Model 75H was similar to the Y1P-36, but a lower-powered engine was provided and a fixed, single-strut undercarriage with streamlined fairings was fitted. These modifications were first applied to a demonstrator aircraft which was re-engined with a Wright Cyclone GR-1820-GE rated at 875 hp for takeoff. This airplane was given the civil registration of NR1276, and publicized in Curtiss sales brochures as "Hawk 75". Emphasis was placed on ease of maintenance, rough field performance, and the amenability of the aircraft to accommodate different brands of engines and different types of armament in order to suit the customer's individual requirements.

A second and more definitive demonstrator aircraft was built which differed from its predecessor in some respects, including the adoption of the more deeply-scalloped decking immediately aft of the cockpit and revised windshield arch and canopy framing. Armament was supplemented by an additional pair of 0.30-cal machine guns in the wings, firing outside the propeller arc. Provision was made for the attachment of underwing bomb racks capable of carrying ten 30-lb or six 50-lb bombs, plus a centerline rack for a single 500-lb bomb. This aircraft was given the civil registration of N1277.

The first 75H carried the US civil registration of NR-1276. It was sold to China. The Chinese government presented this airplane to General Claire L. Chennault for his own personal use. The second one was registered as NR-1277 and was sold to Argentina.

Hawk 75M for China

The first overseas customer for the Hawk 75 was the Chinese Nationalist government, which ordered a total of 112 Hawk 75 non-retractable undercarriage models with R-1820 Cyclone engines and four 0.30-in guns (two in the fuselage and two in the wings). These planes were to be built by Curtiss and delivered as major components to the Central Aircraft Manufacturing Company at Loi-Wing, where they would be assembled and delivered to Chinese units. These airplanes were retroactively assigned the designation Hawk 75M by the Curtiss company. Aside from the additional wing guns and some minor revisions to the undercarriage fairings, these planes were identical to the second "simplified Hawk" demonstrator.

The Hawk 75M was powered by an export-approved 875 hp Wright GR-1820-G3 Cyclone radial. Wingspan was 37 feet 0 inches, length was 28 feet 7 inches, and wing area was 236 square feet. Empty weight was 3975 lbs, and gross weight was 5305 lbs. Maximum speed was 280 mph at 10,000 feet, service ceiling was 31,800 feet, and range was 1210 miles with fuel overload. Armament was four 0.30-in machine guns--two in the nose and two in the wings.

It is uncertain just how many Hawk 75Ms actually ended up in Chinese service. Only 30 Hawk 75Ms are accounted for in Curtiss records, with deliveries beginning in May of 1938. Tooling and kits for an unspecified number were delivered to the Central Aircraft Manufacturing Company Wing for assembly in China, and an unspecified number were built there. Three full squadrons of Model 75Ms are known to have been operational. These fighters achieved few successes against the Japanese forces, largely owing to poor serviceability and the inadequate training of both pilots and ground crews.

Hawk 75N for Thailand
The government of Siam (Thailand) also exhibited interest in the Hawk 75, and ordered somewhere between 12 and 25 examples (the exact number is uncertain, and depends on which source you pick). These were given the designation Hawk 75N by Curtiss, and were generally similar to the Chinese Hawk 75Ms except for some minor revisions to the undercarriage mainwheel fairings and some differences in the armament. Sources also differ in the armament fitted--one claims that the armament was two nose guns (one 0.30-in and one 0.50-in nose guns and four 0.30-in guns in the wings, another claims that that there were two 23-mm Danish Madsen cannon housed in detachable underwing fairings.

Twelve Hawk 75Ns were delivered to Siam (Thailand) starting in November, 1938. They These Hawk 75N fighters were involved in the Thai invasion of Indo- China in January 1941, the first recorded combat taking place on January 11 when four 75Ns escorted nine Martin 139-Ws in an attack on the French airfield at Nakorn Wat. The formation was intercepted by four French Morane-Saulnier M.S.406s. In the resulting air battle, the Thai Hawks claimed two Morane fighters shot down (although the claim was later refuted by the French). On December 7, 1941, the Thai Hawks were in action once again, this time against invading Japanese forces. In the brief battle, one third of the serviceable Hawks were destroyed. Those not destroyed were taken over by the Japanese. One example is now in the Royal Thai Air Museum in Bangkok.

Hawk 75O for Argentina
After purchasing the NR1277 75H demonstrator (c/n 12328) from Curtiss, the Argentine government ordered twenty-nine production examples of the non-retractable undercarriage Hawk 75 with 875 hp Cyclone engines. Designated Hawk 75O by the Curtiss company, these planes had a similar undercarriage to the Thai Hawk 75N and featured a redesigned engine exhaust system with a semi-circle of electrically-operated gills at the rear of the cowling. Armament consisted of four 7.62-mm Madsen machine guns. The first Hawk 75O was completed by Curtiss in late November, 1938. The planes were serialed C-601 through C-630.

Maximum speed was 239 mph at sea level and 280 mph at 10,700 feet. Initial climb rate was 2340 ft/min. An altitude of 23,000 feet could be attained in 12.52 minutes. Service ceiling was 31,800 feet. Empty and loaded weights were 3975 lbs and 5172 lbs.

At the same time, Argentina acquired a license to manufacture the Hawk 75O at the Fabrica Militar de Aviones. The first FMA-built Hawk was delivered on September 16, 1940. A total of 20 was built, with serials being C-631 to C-650. Some of these Hawks remained in service for over a decade, the last ones operating from El Plumerillo in western Argentina until 1953, when they were transferred to training units until being withdrawn during 1954.

Model 75Q for China
Model 75Q was the designation assigned to two additional non-retractable undercarriage demonstrators with R-1820 engines. One was converted to retractable undercarriage configuration and was presented to Madame Chiang Kai-Shek. She gave the plane to General Claire Chennault who was then reorganizing the Chinese Air Force. The other was flown as a demonstrator in China by American pilots but crashed after takeoff on May 5, 1939.

Sources:

1. Curtiss Aircraft, 1907-1947, Peter M Bowers, Naval Institute Press, 1979
2. The Curtiss Hawk 75, Aircraft in Profile No. 80, Profile Publications, Ltd. 1966
3. War Planes of the Second World War, Fighters, Volume Four, William Green, Doubleday, 1961.
4. Air Enthusiast, Volume 1, William Green et al, Doubleday, 1971.
5. Hawk Dynasty: The Curtiss Hawk Monoplanes, Ken Wixey, Air Enthusiast, Vol 71, 1997.