The Sikorsky S-20 (named after its designer) or RBVZ S-XX (named after its manufacturer) was a Russian single-bay unequal span two-seat biplane designed by Igor Sikorsky in 1916. Displaying some Nieuport influence, it saw very little service during World War I.

Five S-XX aircraft were built in September 1916, with the first two powered by the 100 hp Gnome rotary engine which had powered its predecessor, the RBVZ S-XVI. However, the other three were powered with the 120 hp Le Rhone engine, with which they were allegedly faster than the French Nieuport 17.

The S-XX saw little service because it was viewed as inferior to newer enemy aircraft, and no series production was undertaken. As such, only five aircraft were ever produced.

 Russian Empire

• Imperial Russian Air Service

General characteristics

• Length: 6.5 m (21 ft 4 in)
• Wingspan: 8.6 m (28 ft 3 in)
• Height: 2.6 m (8 ft 6 in)
• Wing area: 17 m² (180 sq ft)
• Empty weight: 395 kg (871 lb)
• Gross weight: 570 kg (1,257 lb)
• Powerplant: 1 × Le Rhône Type 9Jb 9-cylinder air-cooled rotary piston engine, 89 kW (120 hp)
• Propellers: 2-bladed fixed-pitch propeller

Performance

• Maximum speed: 180 km/h (110 mph, 97 kn)
• Range: 390 km (240 mi, 210 nmi)
• Service ceiling: 5,600 m (18,400 ft)
• Time to altitude: 2,000 m (6,600 ft) in 6 minutes 20 seconds
• Wing loading: 33.0 kg/m² (6.8 lb/sq ft)
• Power/mass: 0.21 hp/kg

Armament

• Guns: 1 x 7.7 mm Lavrov machine gun