The Sikorsky S-11 '' Polukroogly '' (Half Round) was a Russian single engine prototype reconnaissance aircraft completed in July 1913 by the Russian Baltic Railroad Car Works while

Igor Sikorsky Igor Ivanovich Sikorsky (russian: И́горь Ива́нович Сико́рский, p=ˈiɡərʲ ɪˈvanəvitʃ sʲɪˈkorskʲɪj, a=Ru-Igor Sikorsky.ogg, tr. ''Ígor' Ivánovich Sikórskiy''; May 25, 1889 – October 26, 1972)Fortie ...

was the chief engineer of the aircraft manufacturing division.

Design and development

The S-11 was a two seat mid-wing

monoplane A monoplane is a fixed-wing aircraft configuration with a single mainplane, in contrast to a biplane or other types of multiplanes, which have multiple planes. A monoplane has inherently the highest efficiency and lowest drag of any wing con ...

with wire-braced wings powered by a

Gnome Monosoupape The ''Monosoupape'' (French for single-valve), was a rotary engine design first introduced in 1913 by Gnome Engine Company (renamed Gnome et Rhône in 1915). It used a clever arrangement of internal transfer ports and a single pushrod-operated e ...

air-cooled

rotary engine The rotary engine is an early type of internal combustion engine, usually designed with an odd number of cylinders per row in a radial configuration. The engine's crankshaft remained stationary in operation, while the entire crankcase and its ...

rated at . It was smaller and lighter than the S-7 on which it was based, and had a conventional wooden fuselage. The cockpit featured

side-by-side seating Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction. The original use of the term in English was in ''tandem harness'', which is used for two ...

with controls for the pilot only on the left. Originally built with

ailerons An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement around ...

controlled by steel tubes inside the wings, it was later redesigned using

wing warping Wing warping was an early system for lateral (roll) control of a fixed-wing aircraft. The technique, used and patented by the Wright brothers, consisted of a system of pulleys and cables to twist the trailing edges of the wings in opposite direc ...

for

roll Roll or Rolls may refer to: Movement about the longitudinal axis * Roll angle (or roll rotation), one of the 3 angular degrees of freedom of any stiff body (for example a vehicle), describing motion about the longitudinal axis ** Roll (aviation) ...

control.

Operational history

Initial flight tests showed good performance from the wing design with a short take-off run of and low stall speed. Further tests revealed limited roll authority leading to the change from ailerons to wing warping. The S-11 won second place in a reconnaissance aircraft competition hosted by the Russian military in 1913, but no orders were ever placed for additional examples.

Specifications

References

{{Sikorsky Aircraft S-11 Single-engined tractor aircraft Mid-wing aircraft Aircraft first flown in 1913 Rotary-engined aircraft