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DURING the past 40‐odd years or so, a number of experimental aeroplane types have been invented, visualized, designed, constructed and even flown which, in a quite unorthodox manner, had neither behind the wing nor in front of it any sort of stabilizing and/or controlling surfaces.

WITH tailless aeroplanes, all known aerodynamic control devices possess the peculiarity of not only producing moments about one axis, but of also causing secondary moments about one or both of the other axes. Horizontal controllers forming part of the wing near the tips in wings having sweep‐back or sweep‐forward, for instance, do not produce rolling moments alone, when differ‐entially deflected; they also cause yawing and pitching moments. Similarly, wing‐tip disk rudders operated on such wings not only produce yawing moments, but may cause rolling and even pitching moments.

THE complexity of the problems which are associated with the lateral stability and directional control of tailless aeroplanes was not realized until rather late.

IN a series of articles entitled “Tailless Aircraft and Flying Wings”, concluded last month, the evolution of the tailless aeroplane and the flying wing was treated. The different trends of the development were classified, and a short discussion of the difficulties which had been experienced during experimental work given.

THERE is little doubt at the present time as to the great advance in safety which the invention of the automatic slot has brought to the aeroplane. It has been the means of overcoming one of its chief failings, the loss of stability and control at the stall. Automatic slots at the wing tips are themselves capable of converting an aeroplane which is unstable in roll at incidences beyond the stall into one which is definitely stable; at the same time the aileron control is increased and improved in that its application is not accompanied by so great an adverse yawing moment as for ailerons working on an unslotted wing. Further, if some form of interconnection between ailerons and slots is adopted, or some device (e.g. the “interceptor”), by means of which the action of the slot can be spoiled, a further big addition to the control at the stall can be made as well as further improvement in the shape of a reversal of the usual yawing moment. Whether such addition is desirable for all types of machine remains to bo seen; it may be that in certain types the automatic slots alone, without interconnection, will provide all the increase in stability and control at the stall which is required.

THE following list of contracts placed by the Air Ministry during March is extracted from the April issue of The Ministry of Labour Gazette:—

A PROBLEM which has attracted some attention since the advent of the tricycle undercarriage is that of the tendency to oscillate or “shimmy ” sometimes shown by the nose‐wheel, which is normally free to rotate about the vertical or castoring axis, subject to the restraint imposed by frictional or hydraulic dampers. Various attempts have been made to predict the amount of damping required to prevent the building‐up of a dangerous wobble; in the simplified investigation which follows it is believed that all the essential variables have been retained, and the basic character of the motion correctly reproduced.

Even in these days of long development periods of conventional metal structures and of huge production orders for orthodox aeroplanes the interest in the Flying Wing type and in tailless designs is by no means asleep.

IF we trace the history of design in engineering, we can, in nearly every case we like to consider, point to a continuous development, a casting away of schemes which no longer meet new design requirements, and a continuous process of adaptation to extend the range of usefulness of the equipment in the field we survey.

THE study of the flight of birds has provided and will still provide much valuable information for tiie progress of human flight. Many suggestions for the improvements of wings by the use of special wing tips owe their existence to the observation of nature. In spite of such suggestions, free‐flight experimentation—as far as published work goes—is still rather rare and restricted in scope. This reluctance may be due to practical design considerations (handling) as well as to the necessity of making the conventional aileron as efficient as possible; it may also be caused by the impression that experiment in this direction is not worth the effort.