|Manufacturer||RBVZ (Russo-Baltic Wagon Works)|
|Primary user||Imperial Russian Air Service|
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.
Operational history 
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.
List of operators 
- Crew: Two
- Length: 6.50m (21 ft 3⅞ in)
- Wingspan: 8.60m (28 ft 2½ in)
- Height: m ()
- Wing area: 17m² (182.99 ft²)
- Empty weight: 395 kg (871 lb)
- Loaded weight: 570 kg (1,257 lb)
- Powerplant: 1 × 120hp Le Rhône air-cooled rotary engine, 90 kW (120 hp)
- Maximum speed: 190 km/h (118 mph)
- Climb to 2,000 m (6,560 ft): 6.33 min
- Guns: 1 x 7.7 mm Lavrov machine gun
- William Green and Gordon Swanborough. The Complete Book of Fighters. Colour Library Direct, Godalming, UK: 1994. ISBN 1-85833-777-1.