The purpose of this paper is to present the case that can be made for the tailless aircraft on the grounds of improved performance and operational suitability.

The whole field of possible investigation is not treated here with uniform thoroughness and the main reason for this is that I have only quoted detailed results for those cases which I have actually considered myself, so that in some instances the general qualitative arguments can be backed up by actual figures, whereas in others the argument has had to be confined to generalities.

From the earliest days of flying, gusts have been a problem for aircraft. In the very early flights aircraft were flown only when it was nearly dead calm and few gusts were met. Later on and, in fact, almost up to the Second World War, flying was greatly restricted by the ground and air conditions at the aerodrome. This meant that there had to be fairly good visibility and that the grass aerodrome must not be unduly softened by water. Since the war, aircraft have been flown with much greater regularity.

In the development of Italian aeronautics four periods can be distinguished :

A first period, covering the 15th, 16th and 17th centuries, in which the first idea of the technical possibility of human flight, both on the heavier and on lighter than air principles, was conceived in Italy and the physico–mechanical conditions of animal flight explained. In thfs period are to be met the names of Leonardo da Vinci, Francesco Lana and Alfonso Borelli working on independent lines.

A second period, in which Italy produced a number of distinguished aeronauts, among whom Vincenzo Lunardi and Francesco Zambeccari became well known in England for having carried out in London the first balloon ascents in 1784-85. In this period, which, starting with the discovery of the brothers Montgolfier, does not go farther than the first decades of the 19th century, Italy did not combine with an interest in practical air navigation any actual scientific contribution to its development.

Knowledge of the motions of aircraft control surfaces due to oscillating hinge moments is of great importance for flutter investigations. While the impedance of the power control unit may play a large part in determining these motions, it is not their only cause. The elasticity of the power unit mounting and the effect on the input of distortion of the aircraft structure, an effect which may depend on air speed, may also be important. Nevertheless the influence of the power unit itself is of major importance. No very satisfactory methods appear to have been devised yet, however, for making such tests. The difficulty lies chiefly in applying the large oscillatory loads to the output of the power control unit, which are necessary if the test is to be realistic. The facts that the oscillating loads must be applied to the jack while it is moving, and that a non-oscillatory opposing load is also desirable, add to the difficulties. For convenience in assessing the characteristics of the unit, it is desirable that the oscillating load should be superimposed on a constant opposing load and that the basic jack motion should be of constant velocity.

The work described below deals, in detail, with the methods whereby the motion of an airship can be calculated. The possible motions of an airship are affected by such factors as its stability, motion of controls, release of hydrogen, dropping of ballast, engine power available, and gustiness of the air. The methods to be described are capable of dealing with these effects either separately or combined in any arbitrary proportions.

The pioneer rarely receives that meed of praise which is his due, until those days arrive when his pioneering has become a page or so of history. What meed of praise he may then receive is too often made savourless by critics unable to disassociate themselves from the knowledge of their own technical era. The halting speed of pioneering aerodynamic research cannot be judged by the supersonic speed of secret splittings of the atom.

It was R. L. Stevenson who said that to travel hopefully is a better thing than to arrive. In aviation we have arrived at that streamline flow of technical jargon which deludes so many they have at last reached the boundary layer of aeronautical knowledge, so that they find experiments with plates always a little flat, although their curiosity may still be aroused by flying saucers.

This paper describes some work, mainly of a theoretical nature, done at the Royal Aircraft Establishment, Farnborough, during the years 1946-1947. The immediate object of this work was to establish some general principles for the guidance of the Ministry of Civil Aviation Airfield Lighting Committee, which is the body charged with the task of deciding what visual aids shall be installed on the civil airports of this country. The work is far from completion and from the scientific point of view, this account of it must necessarily leave some loose ends, but it is felt that the method of attack and the underlying ideas may prove useful to other workers in this field. If this should prove to be the case, then international standardisation will have been brought a little nearer, and as will be made clear in this paper, this is almost as necessary for the visual aids as for the radio aids.