During World War 1 (1914-1918), the advantage in the air war over Europe had changed hands several times, driven by a combination of evolving tactics, experienced pilots and advancing technologies of the period. Aircraft could now fly farther, higher and faster than ever before and carried increasingly potent armament. Towards the end of the war, French engineer Andre Herbemont headed another entry in the storied S.P.A.D. ("Societe Pour L'Aviation et ses Derives") fighter line with the introduction of the S.P.A.D. S.XX (S.20) fighter.
First flying on August 7th, 1918, the aircraft was still in development by the time of cessation of hostilities in November. The S.XX was not officially introduced, therefore, until 1920 and this limited production to approximately 100 units due to the world-wide military draw-down. Manufacture of S.P.A.D. S.XX aircraft was handled by Bleriot while the primary operator of the series became the French Air Force. The aircraft series also saw limited, post-war numbers and service under the flags of Bolivia and Paraguay.
The S.XX was born from the preceding single-seat SPAD S.XVII, itself derived from the single-seat S.XIII fighter. The S.XX differed primarily in its two-seat configuration with the pilot and gunner/observer seated inline across two individual, open-air cockpits. The stout fuselage was of a conventional shape, well-contoured and rounded, with the engine compartment at the front and a single rudder fin at the rear (with applicable horizontal tailplanes). The wings were of equal span with parallel and v-shaped struts joining an upper and lower wing assembly. The upper wing assembly was given considerable sweep while the lower wing was of a conventional straight design. The undercarriage was fixed with two landing wheels while a simple skid aided the tail when the aircraft was at rest. The pilot was afforded 2 x fixed, forward-firing .303 Vickers machine guns over the engine cowl as primary armament while the rear gunner managed a single .303 Lewis gun atop a trainable mount.
Dimensionally, the S.XX sported a wingspan of 32 feet with a fuselage length of 24 feet and height of 9 feet. Empty listed weight was 1,900lbs with a gross weight of 2,880lbs. Power was served through a Hispano-Suiza 8Fb inline piston engine developing 300 horsepower and driving a two-bladed wooden propeller. Performance included a maximum speed of 135 miles per hour, a range out to 250 miles, a service ceiling of 26,240 feet and a rate-of-climb of 1,100 feet per minute.
While the French government originally envisioned a staggering production total during peak war months, its order was severely cut short with the Armistice of November 1918. The Armistice interrupted all manner of programs to date and this included the S.XX which had not yet entered quantitative production by war's end. A bulk of the completed aircraft (95) were of the standard S.XX model while only two of the "improved" S.XX bis were seen - these with larger wing surface areas for better control. One of these was then sold off to Japan's Mitsubishi. From there emerged a line of "one-off" racer platforms that began with the S.20 bis-1 and ended with the S.20 bis-6. Several of these airframes claimed speed records during their time aloft. S.XX/S.20 aircraft served during the 1920s before being given up for more modern types heading into the 1930s.