It is both an honour and a responsibility to deliver a lecture commemorating the names of two scientists who have made unique contributions to fluid dynamics, and whose names perhaps above all others will remain immortal in our subject. The range of topics that would be suitable for such a lecture is very wide, because there is scarcely a branch of fluid dynamics in which the work of Reynolds and Prandtl does not continue to play a significant part. In a lecture of current interest there is, therefore, no problem of relating the subject matter to the names to be commemorated; the influence of Reynolds and Prandtl remains as strong as when they were alive, and many of the problems that engaged their attention are even today only partially solved. The lecturer must, therefore, use other considerations for guidance in the selection of his subject from the limited range on which he is qualified to speak, for few could hope to work over the wide field covered by Reynolds and Prandtl. He must if possible select a, topic in which major contributions have originated from Germany and the United Kingdom, on which research is actively in progress in both countries, and for which progress has relied on the combination of theoretical and experimental work to provide acceptable simplifying assumptions that characterised many of the investigations of Reynolds and Prandtl.

It is now 13½ years since turbine engines first began airline service with the Dart in the Viscount. It is 11½ years since the de Havilland Ghost jet engine went into airline operation with the Comet. Today there are some 2468 gas-turbined aircraft operating (or on order) on commercial service and it would be interesting to look back over those 13½ years and ask the question, “How do we apply this experience towards meeting the requirements of the future?”

I can only speak with first hand knowledge of that part of the operation associated with engines produced by my Company. However, this is a sizeable sample covering over 50 per cent of the “Free-World’s” civil aircraft including propeller turbines, jet and by-pass engines.

A considerable amount of material has been produced over the past few years on the subject of heliports and therefore it is proposed to make only brief reference to general heliport requirements and the national and international activity in this field. The application of these requirements to the proposed heliport at Penzance will then be discussed.

Aerial crop spraying necessitates the lowest feasible application rates to minimise costs. The low volumes now being used in the Tropics and in this country often require very high concentrations of active ingredient. Most agricultural sprays are formulated for use in 10-100 gallons per acre. When the same weight of chemical is applied in one gallon or less per acre any one of hitherto disregarded factors, such as surface tension, rate of evaporation, density, viscosity, dynamic catch, and so on, may unexpectedly reach a critical value. An understanding of the limits of these factors is essential for the diagnosis or prevention of faulty biological performance.

In talking about trends in land tenure and ownership, I propose to confine myself, mainly, to agricultural land in England and Wales, as agriculture is by far the biggest single use to which our land is put. Let me say, at once, that there is a marked lack of co-ordinated statistics on many aspects of the subject and I have, therefore, thought it best to round-off the majority of the figures quoted. For the convenience of those who may wish to pursue the matter further, a list of the main sources of information has been included in the references.

The continuing increase in the standard of living has brought with it a marked trend towards the use of processed vegetables, especially those which are prepared and require little or no attention before serving. This has been particularly marked in frozen foods and more recently dried foods, including accelerated freeze dried products.

The customer demands products which are of a consistently high quality and the food industry is therefore concerned with the purchase of crops of a very high standard in order to produce consistent products for sale. This creates a demand for produce which is free from blemish, pest and disease effects. It also necessitates crops being harvested at the optimum time and any one crop should be as uniformly mature as is possible.

Tsetse flies are generally classed as insects of medical and veterinary importance, but qualify for consideration by this group by virtue of their indirect influence on agricultural development in Africa and their possible control by the application of insecticides from aircraft.

Tsetse flies are confined to the African continent and a few small off-shore islands. They are widely distributed between 14°N and 29°S wherever the environment is suitable; and are absent from N. Africa, the Sahara, the Red Sea Zone and the Somalias, and the highlands of Ethiopia, and from the Union of South Africa, except Zululand.

The economic losses occasioned by forest fires in Canada are serious. Although the forest lands are largely under the jurisdiction of the provincial governments the forest resources are of national interest. For this reason the federal government, through the Department of Forestry, carries out a national programme of forestry research. The research in forest fire control encompasses the use of aircraft. This paper reviews the early developments in the use of aeroplanes in Canadian forestry operations. The more recent developments of direct fire suppression techniques, such as water dropping, are discussed in detail.

This subject is one that seems to have received more consideration in agricultural, legal and insurance circles in the U.S.A., Australia and New Zealand than in England which is, perhaps, understandable in view of the differences in terrain, crops and aircraft operating facilities between the various countries.

There are a number of American legal reports touching upon crop spraying liability and several Australian and New Zealand cases, but few English cases. Certainly there have been a number of claims in this country for damage to persons and property arising from crop spraying operations, but it is seldom that these claims proceed to trial and perhaps the reasons for this will become apparent as the various aspects of liability are considered.

In every country where agricultural aviation is done as a private enterprise, some system of rules and regulations is sure to exist and the International Agricultural Aviation Centre has collected data on this subject.

To imagine, however, that a system of regulations, ideally suited to all cases, could be drawn up on a basis of these national rules is an illusion. Every country—and this holds true for many spheres—is blessed or cursed with the laws it deserves. For all these systems of laws and regulations are determined partly by internal and partly by external factors. Let us compare two countries. One is densely populated with intensive agriculture, the other sparsely populated with extensive agriculture. It is obvious that the first country will have a more comprehensive system of regulations in regard to agricultural aviation than the second country. The denser population necessitates a higher grade of protection against the dangers from both the aircraft themselves and the drift of toxic chemicals. Quality agriculture demands quality work from the aerial applicator.

Wind tunnel measurements of the auto-rotation characteristics of Lanchester’s “aerial tourbillion” are presented in the form of tip speed plotted against wind speed. Three configurations were tested, a 10.94 inch diameter model with and without a cowling, and a 7.50 inch diameter model without a cowling. All showed a minimum wind speed for auto-rotation, dependent on friction at the shaft. At each wind speed above this value, there were two equilibrium rotational speeds, an unstable one, giving the required initial rpm for auto-rotation, and a higher stable one, the auto-rotation speed, which with increasing wind speed rapidly approached proportionality to the wind speed.

Fairly good agreement with an approximate blade element theory was demonstrated, the best agreement being obtained with the measurements on the model with cowling.

The linear vibrating system of two degrees of freedom, see Fig. 1, whose mathematical solution is well known (see for example ref. 1), is nevertheless on the verge of being too awkward for manipulation in the design office. It is of considerable interest as the basis of a vibration absorber and techniques continue to be developed for investigating the effects of changing the design constants on the properties of the system and the more complicated ones derived from it.