Designed by André Herbemont, the S.51 shared its basic configuration with his other aircraft of the period, being a biplane with a swept upper wing and unswept lower wing, joined by I-shaped interplane struts. Unlike earlier designs, the S.51 used metal construction for the wings.
The prototype S.51 was rejected by the French authorities, but revised versions found export customers in the Polish Air Force, which bought 50 of them, and the Turkish and Soviet air forces which each bought a single example. Another development, the S.51/3, was experimentally fitted with the first controllable-pitch propeller developed in France, also designed by Herbemont.[2]
Variants
S.51
Prototype for French evaluation, 1x 280 kW (380 hp) Gnome et Rhône 9Aa radial engine.[3]
S.51/2
Refined version exported to Poland, 1x 310 kW (420 hp) Gnome et Rhône 9Ab radial engine.[4]
S.51/3
Prototype with variable-pitch propeller.
S.51/4
Export version for Turkey and the USSR with two extra machine guns in the wings.
^Grey, C.G., ed. (1928). Jane's all the World's Aircraft 1928. London: Sampson Low, Marston & company, ltd. p. 86c.
Bibliography
Bruner, Georges (1977). "Fighters a la Francaise, Part One". Air Enthusiast (3): 85–95. ISSN0143-5450.
Kotelnikov, V.; Kulikov, V. & Cony, C. (November 2001). "Les avions français en URSS, 1921–1941" [French Aircraft in the USSR, 1921–1941]. Avions: Toute l'Aéronautique et son histoire (in French) (104): 37–43. ISSN1243-8650.