Sikorsky S-9

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Sikorsky S-9 aircraft side view circa 1913.jpg
Sikorsky S-9 circa 1913
Role Experimental Monoplane
National origin Russian Empire
Manufacturer Russian Baltic Railroad Car Works
Designer Igor Sikorsky
First flight 1913
Number built 1

The Sikorsky S-9 Kruglyj (Rounded One) was a Russian single engine prototype aircraft completed in the spring of 1913 by the Russian Baltic Railroad Car Works while Igor Sikorsky was the chief engineer of the aircraft manufacturing division.

Design and development[edit]

The S-9 was a three-seat mid-wing monoplane with constant-chord wire-braced wings originally powered by a Gnome air-cooled rotary engine rated at 100 hp (75 kW). It was the first monocoque monoplane built in Russia and the cylindrical tapered fuselage was constructed of plywood 5 mm thick in the forward section and 3mm thick aft. Construction was completed in the spring of 1913.[1][2]

Operational history[edit]

Upon completion the S-9 was found to be substantially heavier than anticipated and the engine only delivered 80% of its rated horsepower. Initial flight tests revealed very poor performance. The engine was replaced by a 100 hp (75 kW) Gnome Monosoupape and further flights showed only a nominal increase in speed. The machine was eventually scrapped.[1][3]


Data from Russian Aviation Museum[2]

S-9 nose detail

General characteristics

  • Crew: One
  • Capacity: Two passenger
  • Upper wingspan: 39 ft 4 in (12 m)
  • Wing area: 320 sq ft (30 m2)
  • Empty weight: 1,521 lb (690 kg)
  • Gross weight: 2,183 lb (990 kg)
  • Powerplant: 1 × Gnome Monosoupape 7-cylinder air-cooled rotary piston engine, 100 hp (75 kW)
  • Propellers: 2-bladed


  • Maximum speed: 56 mph; 49 kn (90 km/h)
  • Wing loading: 6.8 lb/sq ft (33 kg/m2) max load


  1. ^ a b Sikorsky, Igor (1944). The Story of the Winged-S. New York: Dodd, Mead & Company. p. 43. ISBN 9781258163556.
  2. ^ a b "S-9". 4 September 1997. Retrieved 2 April 2017.
  3. ^ "Sikorsky S-9 1911". Retrieved 5 April 2017.