Induced Aerodynamics of Helicopters: Part IV Available to Purchase

ALL the theories relating to the nature of the airflow through a helicopter rotor which have been reviewed in the first three parts of this paper relate to vertical velocities only; that is, to the downwards acceleration of the air whereby rotor thrust is generated. But since a practical rotor blade also experiences in‐plane forces it is evident that in‐plane movements of the air in the slipstream must also occur. In point of fact the slipstream rotation behind the propeller of a single engined aeroplane of conventional design is an important factor in its design, particularly when considering take‐off conditions.