The Curtiss P-1 Hawk was the first in a family of taper-winged biplane fighters that served with the USAAC and the US Navy and that was exported in significant numbers, remaining in service for over a decade.
The P-1 was developed from the earlier Curtiss PW-8, which had itself been developed from a series of Curtiss racers of the early 1920s. The production version of the PW-8 was of mixed construction, with a welded metal framework for the fuselage and a wooden frame for the wings, all fabric covered. The wings had a thin cross-section which required two sets of struts and were straight edged. The PW-8 used a surface radiator, which consisted of thin tubes mounted on the surface of the upper wing. This reduced drag, and had been used with success on the racers, but the long pipes were prone to leak, and the entire radiator was vulnerable to battle damage.
The third PW-8 prototype underwent two stages of further develop. First it was given thicker straight wings, with one set of struts, turning it into the single-bay biplane XPW-8A. The surface radiator was replaced by a radiator built into the centre section of the upper wing. This was then replaced by tunnel radiator mounted below the engine. Finally the wings were replaced, this time with tapered wings similar to those of the Boeing PW-9. The modified aircraft, with the designation XPW-8B, was delivered in March 1925, and on 7 March Curtiss received an order for fifteen production versions of the aircraft, to be delivered as the P-1. The P-1 was of the same mixed construction as the PW-8, with a welded metal tube fuselage and wooden wings, all covered in fabric.
The initial production contract was for fifteen aircraft, ten of which were completed as the P-1, powered by the Curtiss D-12 engine. The last five were completed as the P-2, using the unsuccessful Curtiss V-1400 engine. Three further production versions were ordered between 1925 and 1928. The P-1A had a slightly longer fuselage. The P-1B had a number of minor changes. The P-1C had wheel brakes and larger main wheels. Curtiss then moved on to the P-6, which used a more powerful Curtiss Conqueror engine.
The P-1 entered service with the 27th and 94th Pursuit Squadrons of the 1st Pursuit Group at Selfridge Field in 1925, replacing the PW-8. Later in 1925 the 95th Pursuit Squadron received the type, followed by the 17th in 1926. All four of these squadrons had earlier used the PW-8. The 95th only used the P-1 until 1927, but the other three squadrons retained it to 1930-31.
The P-1 was also used by the Headquarters Squadron, Bolling Field in the late 1920s, the Air Corps Detachment, Bolling Field, from 1928-30, the 36th Pursuit Squadron from 1930-32 and the 43rd School Squadron (later 43rd Fighter Squadron) from 1928-35.
Although the P-1 never saw combat in American colours it did play a part in the slow expansion of the Air Corps during the late 1920s and early 1930s and helped raise the Corps' public profile. It took part in the 1927 Air Corps manoeuvres. In 1927 twenty-five P-1s were part of a larger force that took part in operations with Army service schools. In 1930 eighteen P-1s made an experimental winter move to Spokane, Washington, to see if fighter aircraft could quickly move long distances in the winter. Sixteen of the aircraft returned safely, and the move was considered to have been a partial success. It took longer than expected but was quick enough to prove that the Air Corps didn't need strong fighter forces in every corner of the United States, but could move a strong central force to a threatened area at any time of year. The P-1's last major public appearance came during the 1931 air exercises. An Air Division was formed, containing 58 P-1s, 17 P-6s (and 130 Boeing P-12s), and travelled around the country in an attempt to give the general public an idea of what the Air Corps was doing. After 1931 the P-1 was largely withdrawn from frontline service.
A small number of P-1 Hawks were exported using their original USAAC designations. Bolivia purchased four P-1s, Japan one P-1A (joining its single PW-8) and Chile was the biggest customer, with eight P-1As and eight P-1Bs.
The P-1 was the first production version, and was virtually identical to the XPW-8B. It was designed to take either the D-12 engine or the larger Curtiss V-1400. Ten of the original fifteen aircraft were completed as P-1s with the D-12 and five as the P-2, with the V-1400. Deliveries began in August 1925.
This designation was given to the first of the P-1s after it became an experimental test-bed. It was given a modified Liberty engine for the 1926 National Air Races, and later got a Curtiss V-1460 engine and became the XP-17.
Twenty-five P-1As were ordered in September 1925, with deliveries beginning in April 1926. The P1-1A had a D-12C engine, a 3in longer fuselage, a new fuel system and a better bomb release system. Twenty three of the twenty five aircraft were completed as P-1As. One was completed as the XAT-4 advanced trainer prototype and the final one (26-300) as the first XP-3A.
Another three P-1As were later produced by fitting D-12 engines in three of the unsuccessful P-2 aircraft.
Twenty-five P-1Bs were ordered on 27 August 1926. They were similar to the P-1A but with larger wheels, a modified radiator and engine cowling and carried flares for use during night landings. The P-1B was powered by the 435hp V-1150-3 engine.
Designation given to two P-1Bs when used as a test machine
The P-1C was the last production version of the P-1. It was given wheel brakes and new 30in by 5in wheels. Thirty-three were ordered on 3 October 1928 and the last were delivered in April 1929. One of the P-1Cs (29-259) was given a Conqueror engine to become an XP-6B. This aircraft was used for a New York to Alaska flight in July 1929.
Designation given to one of the P-1Cs when used for test work.
The P-1D was the designation given to thirty-five AT-4 advanced trainers after they were given V-1150-3 engines to convert them back into standard fighter aircraft.
The P-1E was the designation given to the five AT-5 trainers that were re-engined to become standard P-1 fighters.
The P-1F was the designation given to the thirty-one AT-5A trainers that were re-engined to become standard fighters. The designation was also given to the second XP-3A/ XP-21 when it was given a D-12 engine.
Engine: Curtiss V-1150-3 12 cylinder water-cooled engine
Span: 31ft 7in
Length: 22ft 8in
Height: 8ft 11in
Empty weight: 2,105lb
Loaded weight: 2,932lb
Maximum take-off weight:
Max speed: 160mph at sea level
Cruising speed: 157mph at 5,000ft
Climb Rate: 1,540ft/ second
Range: 600 miles
Armament: Two .30in machine guns
Engine: Curtiss D-12C liquid cooled engine
Span: 31ft 6in
Height: 8ft 9in
Empty weight: 2,195lb
Maximum weight: 2,973lb
Max speed: 154.4mph
Climb Rate: 1,460ft/ min
Service ceiling: 20,800ft
Range: 300 miles
Armament: Two .30in machine guns