Mr Chairman, Ladies and Gentlemen

It gives me great pleasure to introduce the lecturer this afternoon, particularly as I have known him for the past 16 years and, better still, we have been associated in the development of rotating wing aircraft during most of that period

MR KENNETH WATSON, who is a Founder Member of the Helicopter Association and an Associate Fellow of the Royal Aeronautical Society, is also Chief Mechanical Engineer to the Cierva Autogiro Company

MR WATSON served his apprenticeship with Messrs G & J Weir, Glasgow, and joined the Aircraft Department of that firm in 1933, which was then under my control His designing ability was quickly appreciated and he was entrusted with the design of some of the major components, such as rotor hubs, transmission systems and control organs I think I am right in saying that the Cierva Autogiro Company and their Licencees, Messrs G & J Weir, have designed more prototype rotor systems than any other firm engaged in the art, and in 1936 no less than five rotor hubs were made and tested within seven months

The knowledge of the flow through a rotor of a rotary-wing aircraft is essential for the study of many helicopter problems The behaviour of a helicopter with respect to stability, region of roughness, etc, depends in many cases on the airflow through the disc Most existing stability or performance theories fail when they concern low forward speed and vertical descent because of some simplifying assumptions

An attempt has been made to find a rather simple expression to describe the variations in axial velocity through a rotor as a function of the azimuth angle

Further, a chart is produced giving the average axial flow through the disc for all possible combinations of forward and vertical velocities, valid for all kinds of one-rotor aircraft

The results are used to improve the theory of some problems as mentioned above and are applied, where possible, to the Sikorsky S51 helicopter, to compare the theory with experimental data