The Curtiss PW-8 was the first in a long series of Curtiss biplane fighters to be produced for the US Army and Navy between the two World Wars.
The PW-8 was based on a series of earlier Curtiss racers. Its immediate predecessor was the Navy's R3C racing plane, which took first and second place in the 1925 Pulitzer race. This was a small aircraft, with a wingspan of 22ft, a length of 20ft and a height of only 6ft 9.5in. The R3C has a gross weight of 2,150lb, was powered by a 565hp Curtiss V-1400 engine and had thin wings with a Curtiss C-80 aerofoil. The upper wing was on the same level as the top of the fuselage.
The PW-8 was a bigger aircraft, with a wing span of 32ft, a length of 22ft 6in and a gross weight of 3,151lb. It used the Curtiss C-62 aerofoil, a thin wing also used on the R2C racer, and one that required two sets of struts. The upper wing was raised above the fuselage. The PW-8 used a 440hp Curtiss D-12 engine, and the combination of an increase in weight and decrease in power meant that the top speed of the PW-8 was only 168mph, nearly 100mph slower than the R3C.
The PW-8 had a fabric covered welded steel tube fuselage and tail and a wooden wing. The wings had a thin cross-section, forcing the use of a second set of struts, making the PW-8 the only twin-bay single seat fighter used by the US Army after the First World War. The radiators were built onto the skin of the upper wing inboard of the ailerons. This system was used on the 1920s racers, and was efficient and produced less drag than other methods, but it was soon clear that it was too vulnerable to battle damage and the PW-8 was the only American production fighter to use this system. The PW-8 also introduced a divided-axle undercarriage, replacing the single axle system used on the racers.
The PW-8 began live as a private venture, developed by Curtiss in the belief that it would be a big enough improvement on the First World War era fighters then in use to force the US Army to take an interest. The first prototype made its maiden flight in January 1923, and in April the gamble paid off. On 27 April the Army bought the original prototype and ordered two more. These aircraft were delivered with the PW-8 designation and only became the XPW-8 on 14 May 1924 after the introduction of the X for experimental prefix.
On 25 September 1923 the army ordered twenty-five production aircraft based on the second prototype, which featured a number of aerodynamic improvements. These aircraft were delivered between June and August 1924 and entered service over the next year (although some were held back for tests and experiments).
The third prototype was eventually developed into the XPW-8B, with tapered wings based on the wings of the Boeing PW-9. In this form it became the prototype for the Curtiss P-1 Hawk and the entire family of Army and Navy Hawk biplanes that followed.
The first prototype made its maiden flight in January 1923 and was bought by the US Army on 27 April. On 9 July it was used on an unsuccessful attempt to cross the United States from east to west between dawn and dusk. Later in the year a second cockpit was added by Air Service engineers at McCook Field. The modified aircraft was given the designation Corps Observation Experimental (CO-X) and was entered for the 1923 Liberty Engine Builders Trophy for military two seaters. The aircraft was withdrawn after other entrants complained that it wasn't a genuine two-seat aircraft.
The second prototype had a revised undercarriage and aerodynamic improvemenets and became the basis for the production aircraft.
Twenty-five production PW-8s were ordered on 25 September 1923 and delivered from June 1924.
The third Army prototype became the basis for the P-1 Hawk. It was completed with revised wings that attempted to solve two of the problems with the PW-8. The wings were made thicker, eliminating one set of struts and thus reducing drag. The surface radiators were replaced with a radiator built into the centre section of the upper wing. This aircraft was delivered in September 1924, and underwent tests at McCook Field. The XPW-8A was delivered on 4 September 1924 and later that year took third place in the 1924 Pulitzer Trophy Race. It was then further modified to become the XPW-8B.
After competing in the air races the XPW-8A was returned to Curtiss to get another set of new wings, this time tapered wings with a Clark Y aerofoil. The new wing was based on the wings of the Boeing PW-9 and had been developed by George Page, a Curtiss engineer, after examining photographs of the Boeing aircraft. The modified aircraft was delivered in March 1925 and was a significant improvement on the standard PW-8. The new design was ordered into production as the Curtiss P-1.
The PW-8 replaced the Boeing MB-3A in the 17th, 27th, 94th and 95th Pursuit Squadrons in 1924, all part of the 1st Pursuit Group based at Selfridge Field, and remained in use until 1926. All for squadrons then moved on to the P-1 and most later used the P-6, although often not for long.
The PW-8 really came to the public's attention on 23 June 1924 when Lt Russell L. Maughan successfully completed the dawn-to-dusk crossing of the United States in PW-8 24-204. He achieved this with one minute to spare, having averaged 160mph on the 2,670 mile journey. Because he was travelling from east to west he was moving with the sun, and had 16.7 hours to make the flight.
The PW-8 was also used for an attempt to fly from Selfridge Field to Miami in a single day during 1925, a distance of 1,300 miles. The attempt failed but it did prove that the idea was practical.
The PW-8 also had a racing career. The XPW-8A came third in the 1924 Pulitzer Air Race where it came third behind a Curtiss R-6 and a Verville-Sperry R-3. The wings of the XPW-8A were later matched with the fuselage of a P-1 to make the XP-6A racer which took part in the 1927 pursuit ship race at the National Air Races.
Engine: Curtiss D-12 inline engine
Span: 32ft 0in
Length: 23ft 1in
Height: 9ft 1in
Empty weight: 2191lb
Gross weight: 3,151lb
Max speed: 171mph
Cruising speed: 160mph at 10,000ft
Climb Rate: 9 minutes to 10,000ft
Service ceiling: 20,350ft
Range: 544 miles in part work
Armament: Two .3in fixed forward firing machine guns