P-36 Hawk/Hawk 75/Mohawk

Role	Fighter
Manufacturer	Curtiss-Wright Corporation
Designed by	Donovan Berlin
First flight	May 1935
Introduced	1938
Retired	1954, Argentina
Primary users	United States Army Air Corps Finnish Air Force French Air Force Royal Air Force
Number built	215 (P-36) plus 900 export Hawk 75 variants
Unit cost	$23,000^[1]

The Curtiss P-36 Hawk, also known as the Curtiss Hawk Model 75, was an American desingned and built fighter plane of the 1930s and 40s. A contemporary of the much superior Hawker Hurricane and Messerschmitt Bf 109, it was one of the first of a new generation of combat aircraft—a sleek monoplane design making extensive use of metal in its construction and powered by a powerful piston engine. Obsolete at the onset of World War II and best known as the predecessor of the Curtiss P-40, the P-36 saw only limited combat with the United States Army Air Forces, but it was used more extensively by the French Air Force, both during the Battle of France and by the Vichy France armed forces, and also by the British Commonwealth (where it was known as the Mohawk), and Chinese air units. Several dozen also fought in the Finnish Air Force against the Soviet Red Air Force. With around 1,000 aircraft built, the P-36 was a major commercial success for Curtiss. This article also covers the YP-37 and the XP-42 prototypes based on the P-36.

Design and development

The Curtiss Model 75 was a private venture by the company, designed by former Northrop Aircraft Company engineer Donovan Berlin. The first prototype constructed in 1934 featured all-metal construction with fabric-covered control surfaces, a Wright XR-1670-5 radial engine developing 900 hp (671 kW), and typical U.S. Army Air Corps armament of one 0.3 in (7.62 mm) and one 0.5 in (12.7 mm) machine guns firing through the propeller arc. Also typical of the time was the total absence of cockpit armor or self-sealing fuel tanks. The distinctive landing gear which rotated 90° to fold the main wheels flat into the thin trailing portion of the wing was actually a Boeing-patented design for which Curtiss had to pay royalties.

P-36 Hawk

The prototype first flew on 6 May 1935, reaching 281 mph (452 km/h) at 10,000 ft (3,050 m) during early test flights. On 27 May 1935, the prototype was flown to Wright Field, Ohio, to compete in the USAAC fly-off for a new single-seat fighter but the contest was delayed because the Seversky entry crashed on the way to the contest. Curtiss took advantage of the delay to replace the unreliable engine with a Wright XR-1820-39 Cyclone producing 950 hp (709 kW) and to rework the fuselage, adding the distinctive scalloped rear windows to improve rear visibility. The new prototype was designated Model 75B with the R-1670 version retroactively designated Model 75D. The fly-off finally took place in April 1936. Unfortunately, the new engine failed to deliver its rated power and the aircraft attained only 285 mph (460 km/h).

Although its competitor, the Seversky P-35, also underperformed and was more expensive, it was still declared the winner and awarded a contract for 77 aircraft. Then, on 16 June 1936, Curtiss received an order from USAAC for three prototypes designated Y1P-36. The USAAC was concerned about political turmoil in Europe and about Seversky's ability to deliver P-35s in a timely matter, and therefore wanted a backup fighter. The Y1P-36 (Model 75E) was powered by a Pratt & Whitney R-1830-13 Twin Wasp engine producing 900 hp (671 kW) and further enlarged scalloped rear canopy. The new aircraft performed so well that it won the 1937 USAAC competition with an order for 210 P-36A fighters.

Curtiss YP-37

Curtiss YP-37

Curtiss XP-42 (USAF Photo)

In early 1937, the USAAC ordered Curtiss to adapt one P-36 to the new liquid-cooled turbo-supercharged Allison V-1710 engine with 1,150 hp (858 kW). Designated XP-37, the aircraft used the original Model 75 airframe with radiators mounted on the sides of the fuselage around the engine. The cockpit was moved far to the rear to make room for the radiators and to balance the aircraft. The aircraft flew in April 1937, reaching 340 mph (547 km/h) at 20,000 ft (6,100 m). Although the turbo-supercharger was extremely unreliable and visibility from the cockpit on takeoff and landing was virtually nonexistent, the USAAC was sufficiently intrigued by the promised performance to order 13 service test YP-37s. Featuring improved aerodynamics and a more reliable turbo-supercharger, the aircraft first flew in June 1939. However, the powerplant remained unreliable and the project was cancelled in favor of another Curtiss design, the P-40.

Curtiss XP-42

In an attempt to improve the aerodynamics of the air-cooled piston engines, the fourth production P-36A (serial 38-004), designated the XP-42, was equipped with a long streamlined cowling resembling that of a liquid-cooled engine. Twelve different designs were tried with little success - although the aircraft was faster than a standard P-36A, engine cooling problems were never resolved. Since the new P-40 was faster, the project was cancelled. Late in its service life, the sole XP-42 was fitted with an all-moving tailplane (an all moving tailplane", combines the functions of an elevator and a horizontal stabilizer in to a single moveable surface) and used to study that control configuration.

Operational history

Argentina

Brazil

British Commonwealth

RAF Mohawk IVs in India in January 1943

China

The prototype of the Hawk 75H - a simplified version with fixed landing gear, like the 75O – was eventually sold to the Chinese Nationalist government who presented it to Claire Chennault for personal use. China also received two similar demonstrators, the Hawk 75Q. They also used a number of simplified Hawk 75Ms against the Japanese. The Hawk 75A-5 was built under license in China, but production was later moved to India, and these machines were absorbed into the RAF as the Mohawk IV.

Finland

Curtiss Hawk 75A-3

After the fall of France, Germany agreed to sell captured Curtiss Hawk fighters to Finland in October 1940. In total, 44 captured aircraft of five subtypes were sold to Finland with three deliveries from 23 June 1941 to 5 January 1944.^[8] Not all were from the French stocks, but some were initially sold to Norway and captured in their wooden crates when the Germans conquered the country. The aircraft were given serial codes CU-551 to CU-585.

In Finnish service, the Hawk was well-liked, affectionately called Sussu ("Sweetheart"). The Finnish Air Force enjoyed success with the type, credited with 190⅓ kills by 58 pilots, between 16 July 1941 and 27 July 1944, for the loss of 15 of their own.^[8] Finnish ace Kyösti Karhila scored 13¼ of his 32 victories in the Hawk, while the top Hawk ace K. Tervo scored 15¾ victories. The Hawks were flown by Lentolaivue 32 throughout their wartime operational service.

The Finnish Hawks were initially armed with either four or six 0.295 in (7.5 mm) machine guns. While sufficient during the early phase of Continuation War, the increasing speeds and armor of Soviet aircraft soon showed this armament was not powerful enough. From 1942, the State Aircraft Factory replaced the fuselage machine guns with either one or two 0.5 in (12.7 mm) Colt machine guns and installed two or four 0.303 in (7.7 mm) Browning machine guns to each wing. The 0.5 in (12.7 mm) Berezin UB or LKk/42 heavy machine guns were also used.^[8] The installation of heavier armament did not cause changes to the very good flying characteristics of the fighter, but the armament was much more powerful against Soviet planes. The Finnish Hawks were also equipped with Revi 3D or C/12D gunsight.

Surviving Finnish aircraft remained in service with the FAF aviation units HLeLv 13, HLeLv 11 and LeSK until 1948.^[8]

France

Curtiss H75C-1

United States

The first production P-36As were delivered to the 20th Pursuit Group at Barksdale Field in Louisiana in April 1938. The aircraft's service history was marred by numerous teething problems with engine exhaust, skin buckling over landing gear, and weak points in the airframe, severely restricting the performance envelope. By the time these issues were resolved, the P-36 was considered obsolete and was relegated to training units and overseas detachments at Albrook Field in the Canal Zone, Elmendorf Field in Alaska, and Wheeler Field in Hawaii. The only combat with U.S.-operated P-36s took place during the Pearl Harbor attack on 7 December 1941. Five of the 39 P-36A Mohawks at Pearl Harbor were able to take off during the attack and were credited with shooting down two Japanese Mitsubishi A6M2 fighters for the loss of one P-36, the first U.S. aerial victories of World War II.^[10]

Variants

Model 75A - company-owned demonstrator aircraft flown with several engine fits
Model 75B - prototype with Wright R-1820 engine
Model 75D - first prototype, Wright Whirlwind R-1670 engine
Model 75H - internal company designation for a simplified export version with fixed landing gear, two slightly differing aircraft built, first sold to China, second to Argentina
Model 75J - company-owned 75A temporarily fitted with an external supercharger
Model 75K - Unbuilt version, it was going to be powered by a Pratt & Whitney R-02180 Twin Hornet engine.
Model 75P - production P-36A (serial 38-010) fitted with Allison V-1710 liquid-cooled engine, prototype for Curtiss P-40
Model 75R - company-owned 75A temporarily fitted with R-1830-SC2-G engine with turbosupercharger, attained 330 mph (530 km/h) but proved complex and unreliable
Y1P-36 (Model 75E) - USAAC prototype, Pratt & Whitney R-1830 engine
P-36A (Model 75L) - USAAC version, P-26A-3 mounted four 0.30 in (7.62 mm) machine guns in the wings in addition to fuselage armament
P-36B - production P-36A fitted with an R-1830-25 engine producing 1,100 hp (820 kW), reached 313 mph (504 km/h), returned to original P-36A configuration
P-36C - an additional 0.30 in (7.62 mm) machine gun installed in each wing with external ammunition boxes under the wings, R-1830-17 engine with 1,200 hp (895 kW), last 30 production aircraft were completed as P-36Cs
XP-36D - production P-36A modified with 2 × 0.50 in (12.7 mm) machine guns in the nose and 4 0.30 in (7.62 mm) machine guns in the wings
XP-36E - production P-36A armed with 4 × 0.30 in (7.62 mm) machine guns in the wings, retained standard fuselage guns
XP-36F - production P-36A fitted with 2 × 23 mm (0.9 in) Madsen cannons under the wings, reverted to P-36A because guns imposed an unacceptable performance penalty with top speed of only 265 mph (427 km/h)
P-36G - Hawk 75A-8 used by Norway for training in Canada, later to Peru. Wright R-1820-G205A engine with 1,200 hp (895 kW).
Hawk 75A-1 - First production batch for France, 4 × 7.5 mm (.295 in) machine guns, R-1830-SC-G engine with 900 hp (671 kW), 100 built
Hawk 75A-2 - Second production batch for France, either R-1830-SC-G engine or 1,050 hp (783 kW) R-1830-SC3-G engine, 6 × 7.5 mm (0.295 in) machine guns, 100 built
Hawk 75A-3 - Third production batch for France, similar with Hawk 75A-2^[9], 135 built
Hawk 75A-4 - Last production batch for France, Hawk 75A-2 with Wright R-1820-G205A Cyclone engine with 1,200 hp (895 kW). 285 built, 81 delivered to France, others to Great Britain as Mohawk IV
Hawk 75A-5 - built under license in China (production was later moved to India), absorbed into RAF as Mohawk IV
Hawk 75A-6 - version for Norway, captured aircraft sent to Finland
Hawk 75A-7 - version for Netherlands East Indies: 1,200 hp (895 kW) Cyclone, 4 × 0.303 in (7.7 mm) (two in nose, one in each wing) and 2 × 100 lb (45 kg) bombs.
Hawk 75A-8 - Export version for Norway. Later redesignated P-36G.
Hawk 75A-9 - 10 aircraft delivered to Persia, captured still in crates and used by RAF in India as Mohawk IVs
Hawk 75M - simplified version with fixed landing gear and Wright R-1820 Cyclone engine for China, built by both Curtiss and Central Aircraft Manufacturing Company in China
Hawk 75N - simplified version for Siam (Thailand)
Hawk 75O - simplified version for Argentine, 30 built and delivered by Curtiss with additional 200 to be built under license locally by Fabrica Militar de Aviones, however only 20 were completed.^[2]
Hawk 75Q - two additional simplified demonstrators for China
XP-37 - Allison V-1710 liquid-cooled engine, cockpit moved to the rear of the fuselage
YP-37 - service test version of XP-37, 13 built
XP-42 (Model 75S) - testbed for streamlining cowlings around air-cooled engines

Survivors

P-36A (s/n 38-001) is on display at the National Museum of the United States Air Force in Dayton, Ohio. This aircraft was the first P-36 to be delivered to the Air Corps. It was donated by Edward S. Perkins of Anniston, Alabama in April 1959. For many years the aircraft was displayed in the markings of the "desert sand and spinach" camouflage markings of the 27th Pursuit Squadron.^[11] The aircraft is now displayed in the markings of the P-36A flown by Lt. Philip Rasmussen during the Japanese attack on Pearl Harbor, 7 December 1941. It is displayed in the Museum's Air Power gallery.^[1]

A complete and restored Hawk 75N survives in the Royal Air Force Museum of Thailand. This was the simplified Hawk 75 with non-retractable landing gear and wheel pants. The serial number is unknown, apparently even to the Thais.

A French H75C-1, photograph shown in the France section above, has been restored to flying condition and is owned by The Fighter Collection at Duxford, England. It has been flown and is shown in French camouflage with markings for the same example (n°82) at two different periods in its career on either side.

A Hawk 75A-6, a Finnish aircraft, was being restored in New Zealand but that effort purportedly went bust so new news on the aircraft is needed. One photograph at the Preserved Axis Aircraft website shows a swastika on the tail.

Specifications (P-36A)

Data from Curtiss Fighter Aircraft: A Photographic History 1917-1948^[12]

General characteristics

Crew: One
Length: 28 ft 6 in (8.7 m)
Wingspan: 37 ft 4 in (11.4 m)
Height: 8 ft 5 in (2.6 m)
Loaded weight: 5,650 lb (2,560 kg)
Max takeoff weight: lb (kg)
Powerplant: 1× Pratt & Whitney R-1830-17 Twin Wasp air-cooled radial piston engine, 1,050 hp (783 kW)

Performance

Maximum speed: 313 mph at 8,500 ft (500 km/h at 2,960 m)
Cruise speed: 270 mph (432 km/h)
Range: 625 mi at 270 mph, (860 mi at 200 mph) ()
Service ceiling: 32,700 ft (9,967 m)
Rate of climb: 3,400 ft/min (17 m/s)

Armament

1 × 0.30 in (7.62 mm) M1919 Browning machine gun
1 × 0.50 in (12.7 mm) M2 Browning machine gun

References

Notes

↑ ^1.0 ^1.1 "Curtiss P-36 Hawk fact sheet." National Museum of the United States Air Force. Retrieved: 7 March 2009.
↑ ^2.0 ^2.1 Padin 1999, pp. 9, 15.
↑ ^3.0 ^3.1 March 1995, p.68.
↑ Shores Air Enthusiast 1983, p.2.
↑ Shores Air Enthusiast 1983, pp. 2–9.
↑ Thomas 2003, pp.67-69.
↑ Thomas 2003, p.69.
↑ ^8.0 ^8.1 ^8.2 ^8.3 Curtiss Hawk 75A Backwoods landing strip - Finnish Air Force aircraft
↑ ^9.0 ^9.1 Persyn 2007^{[page
needed]}
↑ "Aircraft at Pearl Harbor." www.ww2pacific.com, World War II in the Pacific. Retrieved: 7 March 2009.
↑ United States Air Force Museum 1975, p. 23.
↑ Dean and Hagedorn 2007, p. 201.

Bibliography

Bowers, Peter M. Curtiss Aircraft, 1907-1947. Annapolis, Maryland: Naval Institute Press, 1979. ISBN 0-87021-152-8.
Bowers, Peter M. The Curtiss Hawk 75: Aircraft in Profile No. 80. London: Profile Publications, 1966.
Bridgwater, H.C. Combat Colours Number 3: The Curtiss P-36 and P-40 in USAAC/ USAAF Service 1939-1945. Bletchley, Buckinghamshire, UK: Guideline Publications Ltd., 2001. ISBN 0-9539040-5-9.
Dean, Francis H. and Dan Hagedorn. Curtiss Fighter Aircraft: A Photographic History 1917-1948. Atglen, PA: Schiffer Publishing, 2007. ISBN 0-76432-580-9.
Fleischer, Seweryn and Jiri Chodil. Curtiss P-36 Hawk, Cz.3 (Monograpfie Lotnicze 63) (in Polish). Gdańsk, Poland: AJ-Press, 2000. ISBN 83-72370-38-9.
Green, William. War Planes of the Second World War, Volume Four: Fighters. London: MacDonald & Co. (Publishers) Ltd., 1961 (Sixth impression 1969). ISBN 0-356-01448-7.
Green, William and Gordon Swanborough. WW2 Aircraft Fact Files: US Army Air Force Fighters, Part 1. London: Macdonald and Jane's Publishers Ltd., 1977. ISBN 0-356-08218-0.
March, Daniel J. (editor). British Warplanes of World War II. London:Aerospace Publishing, 1998. ISBN 1 874023 92 1.
Padin, Jorge Nuñez, ed. Curtiss Hawk (Serie Fuerza Aérea Argentina: No. 5) (in Spanish). Bahia Blanca, Argentina: Fuerzas Aeronavales, 1999.
Persyn, Lionel. Les Curtiss H-75 de l'armée de l'Air (in French). Outreau, France: Éditions Lela Presse, 2007. ISBN 2-914017-46-4.
Rys, Marek. Curtiss P-36 Hawk, Cz.1 (Monograpfie Lotnicze 61) (in Polish). Gdańsk, Poland: AJ-Press, 2000. ISBN 83-72370-36-2.
Rys, Marek and Seweryn Fleischer. Curtiss P-36 Hawk, Cz.2 (Monograpfie Lotnicze 62) (in Polish). Gdańsk, Poland: AJ-Press, 2000. ISBN 83-72370-37-0.
Shores, Chris. "The RAF's Little Indians". Air Enthusiast, Twenty-three, December 1983-March 1984. Bromley, UK:Fine Scroll. ISSN 0143-5450. pp. 1–9.
Swanborough, Gordon and Peter M. Bowers. United States Military Aircraft Since 1909. Washington, DC: Smithsonian, 1989. ISBN 0-87474-880-1.
Thomas, Andrew. "Indians Over Africa:Curtiss Mohawks in SAAF Service". Air Enthusiast, No. 107, September/October 2003. pp.66-69.
United States Air Force Museum Guidebook. Wright-Patterson AFB, Ohio: Air Force Museum Foundation, 1975.

External links

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