Rotary-Wing Aircraft

Rotary-Wing Aircraft 

a vertical takeoff and landing aircraft in which the lift is created by a combined system of one or two main rotors and the wings. (The Russian term vintokryl is formed from the words vint [propeller or rotor] and krylo [wing], according to the lifting systems used.)

The vertical takeoff and landing of the rotary-wing aircraft, like that of the helicopter, is achieved by using the main rotors, but acceleration is achieved through both the main rotors and the engines, which have tractor or pusher propellers. After reaching the speed at which the aerodynamic control surfaces begin to operate efficiently (maneuvering speed) and up to the maximum flying speed (more than 500 km/hr), the rotary-wing aircraft flies like a conventional aircraft, using the lift of the wing, which increases proportional to the square of the speed and reaches 75-90 percent of the flying weight at maximum flight speed. In the takeoff and landing modes the control system of the rotary-wing aircraft is similar to that of the helicopter, but in the translational mode it may be similar to either the aircraft or the helicopter control system, which is peculiar to each type of rotary-wing aircraft.

In the late 1950’s the English firm Ferry built the Rotodyne rotary-wing aircraft with one jet main rotor and two tractor propellers. Its flight weight is 17,700 kg, and its flying speed is up to 312 km/hr. At the same time, the Ka-22 lateral-system rotary-wing aircraft (designed by N. I. Kamov), with two main rotors and two turboprop engines (designed by A. G. Ivchenko) of 4,300 kilowatts (kW)—or 5,900 horsepower (hp)—apiece was built in the USSR. Its flight weight is 37 tons. In 1961 eight world records were set in this rotary-wing aircraft, including speed in a straight line (356 km/hr), speed on a closed 100-km course (336 km/hr), and lifting a commercial payload (16,485 kg lifted to an altitude of 2,588 m). A speed of 375 km/hr was achieved in isolated flights. Later the American firm Lockheed built the experimental XN-51A rotary-wing aircraft in which the record flight speed of 486 km/hr was achieved. In 1965, on the basis of the XN-51A, the firm built the AN-56A Cheyenne combat rotary-wing aircraft with a four-vane semirigid main rotor, a pusher propeller, and a compensating tail rotor, as on a helicopter. The turboprop engine (from the General Electric company) with a power of 2,500 kW (3,400 hp) made it possible to achieve a maximum flying speed of 408 km/hr near the ground, with a maximum flying weight of 7,700 kg. Further refinement of the rotary-wing aircraft will make it possible to reach cruising speeds of 600 km/hr and cargo capacity of up to 20 tons.

N. I. KAMOV