SPAD S.XIII

The SPAD S.XIII was a French biplane fighter aircraft of World War I, developed by Société Pour L'Aviation et ses Dérivés (SPAD) from the earlier highly successful SPAD S.VII. It was one of the most capable fighters of the war, and one of the most-produced, with 8,472 built and orders for around 10,000 more cancelled at the Armistice.

Design and development

The SPAD S.VII was a single-seat fighter aircraft powered by a 150 horsepower (110 kW) Hispano-Suiza 8A water cooled V-8 engine and armed with a single synchronised Vickers machine gun. It demonstrated excellent performance for the time, and entered service with the French Aéronautique Militaire in August 1916. By early 1917, however it had been surpassed by the latest German fighters, leading French flying ace Georges Guynemer to lobby for an improved version telling the SPAD designer Louis Béchereau that "The 150 hp SPAD is not a match for the Halberstadt ... More speed is needed." An initial solution was to increase the compression ratio of the Hispano-Suiza engine, increasing its power to 180 hp (130 kW), which gave significantly improved performance, allowing the SPAD S.VII to remain competitive, but Hispano-Suiza were developing a geared version of the 8A engine, which would produce greater power, and this engine was chosen by Béchereau for two new fighter aircraft. First to fly was the S.XII, armed with a 37 mm cannon firing through the propeller shaft. This saw limited use, but was followed into production by the more conventionally armed S.XIII.