When a non-uniform stream flows through a cascade of compressor blades a three-dimensional secondary motion is generated in the outlet stream. This motion, which consists of a spanwise re-orientation of the Bernoulli planes, together with the effects of vorticity components in the stream direction, may be predicted theoretically. In this paper experimental results obtained on a 6 in. chord cascade are reported. The experimental and computed outlet angles are compared and the discrepancies are explained qualitatively. Additional particle track and visualisation experiments were designed to investigate the local blade flows and the effects of the nose vortices.

Modern turbine blades are generally twisted about their axes, the shape resembling that of a helicoid. This makes the determination of their overtone frequencies much more difficult. The equations governing the flexural vibrations may be obtained from the Clebsch-Kirchhoff theory for rods which are naturally twisted. By using these equations, this paper considers a first-order approximation for the effect of uniform twist.

The Chairman, in introducing the Author, said that Wing Commander Williams joined the Royal Air Force in 1936 and, after serving m Bomber Command at the beginning of the war he was unfortunate enough to be shot down in a Halifax bomber and taken prisoner After the war he spent some time on instructional duties, and in 1952 he attended the Royal Air Force Staff College In 1953 he was sent to Malaya to form and to command the Helicopter Wing, which also included a Naval Squadron He had, therefore, been very closely associated with helicopter operations for two and a half years Wing Commander Williams was now serving at the Air Ministry, in the Directorate of Air Transport Operations He is a Member of the Association

In this work the co-ordinates of three-dimensional nozzles of several types have been obtained as explicit functions, and some shapes have been plotted. It is hoped that some of these might be of use in cases where smooth uniform fluid flow is desired. The design of a particular nozzle shape in the presence of a plane boundary is given: previously any equations obtained have been toointractable to use.

In a short time from now the civil licenced helicopter will be required to include among its capabilities the ability to operate in Instrument Flight conditions to lower limits than those currently laid down for fixed-wing aircraft operations

At the moment I estimate that the problem is roughly half solved and, if there is a helicopter suitable for city centre operations by 1961, the aids and equipment under development should be able to give safe flight conditions in 150 feet ceilings and 150 yard visibilities

The Chairman, in opening the meeting, said it was a matter of major importance to all concerned not only to have suitable helicopters to use, but also to ensure that when the operators got them they were capable of being used in such a way as to make nonsense of the frequently heard comment that there was no economic future in scheduled operations It was, of course, a fact that unless helicopters could be operated round the clock, in foul weather as well as fair, by night as well as day, like normal means of transport, then they would not take their rightful place in the general transportation set-up

The Chairman, in introducing the Author, said that the occasion was a very auspicious one, in that a paper was being presented by one of the founder members of the Association at a Joint Meeting with the Royal Aeronautical Society, with which the Association maintained the closest of links On behalf of the Association he welcomed the fact that a joint meeting was being held, and he welcomed those members of the Society who were present to hear a paper and discussion on a specialised helicopter subject In particular he welcomed the President of the Royal Aeronautical Society, Mr E T Jones

The drag in two-dimensional flow is expressed in terms of the distributions of static and stagnation pressures along a traverse line downstream of the aerofoil. Sources of error are discussed with regard to their effect on the accuracy of drag measurement in small tunnels at medium Mach numbers.