Ladies and Gentlemen

The subject of the opening paper for our 1948/49 Lecture Session is, I am sure you will agree, of prime importance to all of us in the helicopter industry To my mind there is no point in spending time, money and energy designing and constructing helicopters unless they can be operated economically, although for any specialized application economy may not be so important

MR WIGDORTCHIK has put a great deal of work in the preparation of this paper, and although he will only have time to read a summary this afternoon, examination of the full paper, which will be published in the Association’s Journal, will be well worth while

MR WIGDORTCHIK is an A F R Ae S, and was a Wakefield Scholar to the College of Aeronautical Engineering in London He was commissioned in the Technical Branch of the R A F in 1940, and from 1943 was engaged in Research and Development in connection with aircraft, and subsequently helicopters, holding an appointment in the Ministry of Supply in this respect

Ladies and Gentlemen

The Paper we are about to hear this afternoon is obviously of very great importance to manufacturers and potential operators, and no less to all of us who have the interest of helicopters at heart It is quite reasonable to suppose that the more we know of the problems of operation, the more likely we are to produce the right type of helicopter for the job

It would be difficult to think of anyone better qualified to give this paper than our lecturer to-day, and we are very much honoured that so eminent a gentleman should do so MR ROWE is a Fellow and a Vice President of the Royal Aeronautical Society, has had a varied and distinguished aeronautical scientific career, and was Director General of Technical Development at the Ministry of Aircraft Production in 1945 His present appointment is that of Controller of Long Term Research and Development with British European Airways Corporation, in which capacity he is intimately concerned with the problems of helicopter operation, both present and future

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

From the very beginning of helicopter development the designer has had two major problems, one associated with the balancing of the torque reaction on a mechanically driven rotating system, and the other one that of mechanical difficulties associated with the transmissions ISACCO for instance realized right at the beginning that what he wanted was some jet reaction device on his blade tips, but there was no jet reaction device which was efficient, and he had to have recourse to individual engines, each driving its own propeller on to his blade tips Other designers, such as BRENNAN, in this country, and BLEEKER in America, had recourse to a single engine rotating, with the system This was only half the solution, because they still had to face all the mechanical difficulties From then onwards, many people have tried jet propulsion You will realise that because we have tip speed limitations as we go on to bigger sizes our torque reaction problem becomes worse and worse

From the very beginnings of aviation, France has always been right in the forefront, and that is very true of the helicopter. As a matter of fact, the very first helicopter in the western hemisphere was shown in 1784 before the Academie des Sciences by Launoy and Bienvenue. That was so interesting that it inspired Sir George Caley, the father of British aviation, to do some work on helicopters. Then in 1904, for the first time, Col. Renard read papers, also before the Academie, in which he gave the correct design relationships for a lifting screw system, and he was the first man to describe the articulated blade system, which is today so common. In 1907, two Frenchmen built the first helicopters which lifted themselves off the ground, Paul Cornu and Louis Breguet, both in the same year, but Breguet is always looked on as being the first of the two, because his helicopter was the first in the world to lift itself and its pilot.

This afternoon we are about to hear a lecture entitled ‘Some Speculations on the Aeroelastic Problems of Rotary Wing Systems’ This sounds a terrifying title—rather like the sub-titles of Victorian novels—but I suggest the short title, ‘Collar on Blade Flutter’ I have the pleasant task of introducing to you the lecturer In view of Professor COLLAR’S reputation, I am really not sure whether I should introduce the lecturer to the Association or the Association to the lecturer I shall therefore do both without, I hope, imposing upon your patience

Professor COLLAR is easily introduced, because he is one of those people who hold their jobs After taking his degree in Cambridge, he served for 12 years on the staff of the N P L, and for 4 years at the R A E, before being invited to become the Sir George White Professor of Aeronautical Engineering in the University of Bristol

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