It is reasonable to date the prehistory of the Helicopter Association from the arrival in this country of Juan de la Cierva in 1925, at the invitation of lames Weir and his Associates.

The helicopter idea had intrigued designers from the earliest days of aeronautical experiment but, so far, often to their detriment and the derision of their contemporaries. Cierva had been first in translating the theory of auto-rotation into practical terms and had proved that both stability and control in flight could be achieved regardless of forward air speed. The freely rotating rotor system of the Cierva Autogiro and other early gyroplanes, such as those of Kay and Hafner, provided the missing link which all had been seeking and from this point development proceeded by logical rapid sequence to the flight of the first potentially safe and controllable helicopter in Germany in 1937.

Downward deflection of a propulsive jet may be employed to augment aerodynamic lift in an advantageous manner. In each situation there occurs a simple optimisation when the losses due to reduced propulsive efficiency are contrasted with the gains which accrue from jet lifting. Typical cases will be considered here for wing dominant configurations, i.e. cases where the lifting surfaces contribute most of the drag, with the body contributing but a minor effect. Variable geometry of both airframe and engine is implicitly assumed so that results may be applied to preliminary design studies which will determine the relative propulsion system size and wing area.

This note derives an approximate, theoretical formula for the tension rivet loads transmitted by a shear-buckled skin to the supporting stringers. Allowance is made for the influence of the in-plane stiffness of the stringers and frames in reducing the magnitude of the shear buckles. The formula will be most reliable in the range 1·5 <τ/τcr< 3. When τ/τcr<1·5 the effect of initial irregularities is important, though the rivet loads are not high. When τ/τcr>3 the effect of change of buckle pattern, neglected in this simplified treatment, becomes important. The analysis could however be extended to deal with varying buckle pattern.

When a circular plate of constant thickness is simply supported on a concentric ring and is subjected to a uniform normal pressure, there is a radius for the supporting ring giving optimum bending stress conditions in the plate. Assuming the plate deflections are small, it is concluded that the required supporting ring radius varies between 70·1 and 73·0 per cent of the outside radius of the plate, depending on the value of Poisson's Ratio for the plate material.

For the past 150 years man's ingenuity has been exercised in producing machines to transport himself faster and faster until today he is talking of aircraft which can travel faster than the rotating speed of the earth at the equator, and such that any point on the earth's surface is within ten hours flight time from any other point. But such is the contrariness of the situation that these speeds involve the use of extensive runways away from the crowded city centres and, what with the crowded roads and trains, the journey from the airport to the city centre can be long, tedious and uncomfortable.

The helicopter enthusiast suggests that this problem can be overcome by using a machine that can take off vertically from the city centre and carry the passenger rapidly in comfort to the airport. He also suggests that for journeys up to 200 miles or more, the helicopter is the quickest form of transport from city centre to city centre.

When one considers future developments in Agricultural Aviation there are two questions which need explaining from the past and present and they are difficult to reconcile with one another. One is “Why did not agricultural aviation come into fairly general use 40 years ago in, say, 1920?” The other is “Why has it begun to come into general use now?”

The rate of error in the performance of any task increases rapidly after a certain degree of complexity or rate of operation is exceeded. As aircraft speeds increase, therefore, the safety and efficiency of the operation will depend largely on the extent to which the job of the crew can be simplified and on the work-load being kept within tolerable limits. In recent years the problem has been tackled by the addition of specialist crew members and by the use of automatic and semi-automatic equipment. Distribution of the total load over an increased number of people is no longer a satisfactory solution, however, since it imposes an additional burden on the Captain in his capacity as overall monitor and the time available for this vital task is all too little. While the pilot by tradition tends to reserve judgment on automatic devices generally, where a high standard of reliability is proved the system will receive acceptance in due course and there is little doubt that it is in this field where the greatest contribution to operating efficiency will be found.

The application of automatic data processing techniques to air traffic control has been espoused by both operational and research and development groups dealing in air traffic control throughout the world. As far back as 1947, in the U.S.A., the Special Study Group, SC-31 of the Radio Technical Commission for Aeronautics suggested that a high degree of automation be applied—including rigid control of all flights and their times of arrival.