An all-metal single-engine, single-seat, biplane fighter/trainer of 1929. The Š.31 was based on S-20J with a 450 hp 9-cyl Walter Jupiter radial. Thirty-three were built.
Variants:
Š.31A, Bristol Mercury (becomes S-231)
Š.131, 500 hp 9-cyl BMW Hornet, 3 built.
Š.331, prototype fighter, 1935 (sold to Spain), 880 hp 9-cyl Walter K-14 radial
Š.431, prototype fighter, 1936 (crashed on trials), 14-cyl AS Tiger III
Specifications:
S-131
Engine: 500 hp 9-cyl BMW Hornet
Wingspan: 9.8 m
Length: 7.15 m
Empty weight: 970 kg
Maximum speed: 292 kph
Climb to 5000m: 6 min 50 sec
Range: 450 km
Service ceiling: 10000 m
S-431
Engine: Armstrong Siddeley Tiger, 680 hp
Propeller: wooden two-blade
Wingspan: 10.06 m
Length: 7.9 m
Empty weight: 1310 kg
Top speed: 370 kph
Climb to 5000m: 6 min 58 sec
Service ceiling: 9500 m
All Aero 