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Aviation History
1940
1940 - 1843.PDF
JUNE 27, 1940 RETURN to an OLD LOVE Sikorsky Designs and Demonstrates a Successful Helicopter By H. W. PERRY DEMONSTRATION flights of an experimental heli-copter designed by Igor I. Sikorsky and built by theVought-Sikorsky Aircraft Division of the United Aircraft Corporation, at Stratford, Conn., U.S.A., were made at the factory on May 20. Piloted by the designer, the machine rose vertically about 30ft., hovered motionless over one spot, flew approximately 200ft. across the field, and descended vertically to a landing. In several short flights the ability of the craft to move in any direction and to turn in flight under full control was fully proved. After the flights, Mr. Sikorsky said that they demon- strated a successful solution of the problems that have balked helicopter designers from the earliest days of heavier-than-air flying machine development. This is the third helicopter designed by him, the other two having been built in Russia about thirty years ago, and is the first of them to be flown successfully- It is a direct-lift, power-driven rotary-wing machine in which the power plant, rotor locations, and transmission and control systems were chosen with the purpose of testing specific basic principles. As shown by the photograph, the uncovered fuselage is of trussed tubular construction of generally conventional design, except for the tail structure and location of the power-plant behind the pilot's cockpit. There are no fixed lift and control surfaces, such as wing, ailerons, stabiliser, elevator and rudder. Instead, a 75-h.p. four-cylinder opposed Lycoming engine drives a three-blade rotor of 28ft. diameter by means of a vertical shaft at a speed of 155 r.p.m. and also drives three auxiliary 6ft. 8in. rotors at the rear end of the fuselage. Two of the latter are rotated by vertical shafts mounted at the extremities of a transverse outrigger, and the third by a horizontal shaft disposed transversely to the longitudinal axis of the craft at the extreme rear end of the fuselage. Pitch of the blades of all the rotors h variable, and the shaft of the main rotor can be tilted slightly in any desired direction from vertical. The most important feature con- tributing to successful control of the machine is the mechanical interconnection and synchronisation of the four rotors. Ascent and descent are controlled with precision by a left-hand stick that alters the blade pitch of the main and lateral auxiliary rotors. Motion in the air in any desired direction is controlled by the main control stick, which governs inclination of the main-rotor shaft, and by pedals that vary the pitch of the rearmost vertically dis- posed rotor, which acts as a rudder and also compensates torque of the main rotor. Variation of pitch of the two horizontal auxiliary rotors in the same direction produces longitudinal control, while variation in opposite directions gives lateral control. Most of the lift is provided by the main rotor, the blade- tip speed of which at the most effective pitch is from 250 to 300 m.p.h. whether the machine is hovering or moving forward. An over-running mechanism permits autorotation of the main and two auxiliary rotors in event of stoppage TESTING THE tuisiKOi.s. ivir. Igor Sikorsky makes the first ascent on hi_ i.e. helicopter,"tethered." Subsequently several free nights were made. Note that the machine is
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