共轴直升机空气动力学(英文版)

AERODYNAMIC FEATURES OF COAXIAL CONFIGURATION HELICOPTER 共轴直升机空气动力学(英文版)

AERODYNAMIC FEATURES OF COAXIAL CONFIGURATION HELICOPTER

Eduard PETROSYAN,

Deputy Chief Designer of Kamov Company

Nowadays, the world helicopter industry employs two configurations - single-rotor and coaxial-rotor helicopters with most helicopters featuring the single-rotor configuration.

The pioneers of helicopter-building were aware full well of the fundamental advantages presented by the coaxial configuration. Plenty of projects and attempts of building coaxial helicopters at various times are known. However, it was only single-rotor helicopter featuring the tail rotor that western designers managed to put in extensive operation. Single-rotor helicopters were developed and widely used in the Soviet Union and Russia too. In developing the national helicopter industry, considerable funds and efforts were employed by this country into the further development of the single-rotor configuration, which, however, failed to deal with certain fundamental flaws inherent to this configuration. In 1947, Soviet designer N.I. Kamov commenced his work on actual development of coaxial-rotor helicopters. Over the 50 years, the 'Kamov company has developed and put into series production many a coaxial helicopter: Ka-10, Ka-15, Ka-18, Ka-25, Ka-26, Ka-27, Ka-29 as well as world-renowned Ka-32 and Ka-50 Black Shark.

Due to their small dimension, high thrust-to-weight ratio, superb manoeuvrability and aerodynamic symmetry, coaxial helicopters were widely used as shipborne rotary-wing aircraft operated by the Soviet Navy. The civil aviation began extensive operation of coaxial Ka-26s and Ka-32s.

By the late '70s - early '80s, all necessary prerequisites had appeared for the development of a combat coaxial-rotor helicopter later designated Ka-50. The stiff and above-the-board competition between the Ka-50 and Mil Mi-28, with the latter featuring the classic single-rotor configuration, resulted in the Ka-50's impressive victory and was fielded with the Russian Army.

The coaxial configuration helicopter is so special due to the fact that it embodies a principle of the reactive moment compensation fundamentally different from that of the single-rotor configuration. To compensate for the reactive moment of the single-rotor helicopter's main rotor, there should be developed the tail rotor's side force applied to the airframe, while the coaxial-rotor helicopter has its rotors' reactive moments compensating each other directly in their axis of rotation. This removes the need for any additional forces. Rotors' reactive moments are compensated automatically throughout the flight, thus

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