The Morane-Saulnier M.S. 121 was the first fighter aircraft developed by the company after the First World War, and was designed in response to an official requirement for a light fighter. This programme, for a chasseurs legers, or light fighter, soon became known as the 'Jockey' programme. The aim was to reduce the cost of fighter aircraft by producing a lightweight, lightly armed aircraft with a medium sized engine. The aircraft was to function as an interceptor, so rate of climb was considered of great importance. The new aircraft was to be armed with two 7.7mm machine guns with 300 rounds each, have a ceiling of 26,245ft, a good rate of climb and an endurance of 1hr 30mins at full throttle.
Morane-Saulnier responded with the MoS 121, redesignated the M.S. 121 soon after the prototype was completed. The M.S. 121 was a typical Morane-Saulnier parasol wing fighter, powered by a 400hp Hispano-Suiza 12Jb V-12 engine. The swept back wing had rounded tips and was supported by a pair of struts. The landing gear was a simple cross-axle type.
The M.S. 121 was one of seven prototypes developed for the 'Jockey' programme. It had lower wing loading figures than all but the M.S. 221, giving it good manoeuvrability. The M.S.121 made its maiden flight in 1927, and was somewhat disappointing. Its top speed of 154-160mph was lower than expected, and it failed to achieve the required rate of climb. Work on the M.S.121 was thus abandoned, and Morane-Saulnier focused on the M.S. 221, a similar aircraft but with a more powerful engine.
Engine: Hispano-Suiza 12Jb V-12 engine
Wing span: 32ft 1 4/5in
Length: 22ft 0 1/2 in
Height: 9ft 5 2/3in
Empty Weight: 2,2229lb
Loaded Weight: 2,813lb
Max Speed: 160mph at 4,920ft
Time to 4,920ft: 3.37 minutes
Armament: Two synchronised fuselage mounted 7.7mm machine guns