Blériot SPAD S.51

Design and development

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.

Variants

S.51/1

Prototype for French evaluation, 1x 280 kW (380 hp) Gnome et Rhône 9Aa radial engine.

S.51/2

Refined version exported to Poland, 1x 310 kW (420 hp) Gnome et Rhône 9Ab radial engine.

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.

Operators

 Poland

Polish Air Force

11th (Kościuszko) Squadron

 Soviet Union

Soviet Air Force – One aircraft, used for tests and trials.

 Spain

Spanish Republican Air Force

 Turkey

Turkish Air Force

Specifications (S.51/2)

General characteristics

Crew: one pilot

Length: 6.45 m (21 ft 2 in)

Wingspan: 9.47 m (31 ft 1 in)

Height: 3.10 m (10 ft 2 in)

Wing area: 24.0 m² (258 ft²)

Empty weight: 990 kg (2,182 lb)

Gross weight: 1,360 kg (2,998 lb)

Powerplant: 1 × Gnome et Rhône 9Aa radial engine, 313 kW (420 hp)

Performance

Maximum speed: 230 km/h (143 mph)

Service ceiling: 9,000 m (29,530 ft)

Rate of climb: 7.2 m/s (1,425 ft/min)

Armament

2 × fixed, forward-firing .303 Vickers machine guns