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.

S-9
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

Design and development

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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

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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]

Specifications

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S-9 nose detail

Data from Russian Aviation Museum[2]

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

Performance

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

References

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  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". ram-home.com. 4 September 1997. Archived from the original on 12 October 2006. Retrieved 2 April 2017.