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Before detailing the value of non-destructive testing in the aircraft industry, it seems best to explain aircraft structural design philosophies as they affect NDT.Airworthiness and weight-saving are two over-riding factors in aircraft design. The important parameter from an economic standpoint is the weight. Fig. 1 shows the value of weight saving for a civil aircraft operator in £ per lb with typical values going up to £100 per lb per aircraft per year. (This figure shows the actual financial saving associated with the reduction in operating economics due to the lower weight.) But the vulnerability of an aeroplane in any failure case makes safety a paramount consideration. To save weight, design factors on aircraft are very low.

I have chosen to describe the methods employed by the Research Division of the United States Navy Bureau of Aeronautics with the hope that others engaged in a similar line of endeavour may be able to make profitable use of this information in the solution of their specific problems. The development of the material to be discussed arose directly from the need for quick, reasonably accurate and simple means for studying a broad series of aircraft designs leading toward fulfilling an overall military requirement. This process is carried out in the Bureau of Aeronautics by the Research Division prior to the issuing of a type specification with a request for proposal to the various manufacturers. Before these specifications are decided upon, many designs must be investigated and reported to those initially responsible for the issuing of military requirements. By this process intelligent compromises are arrived at and the best possible aeroplane chosen. These compromises reflect the performance, the ability of operation from carriers, and the effectiveness of the design as a military weapon.

The liquid-cooled engine is generally associated with high speed aircraft, and as I have had some experience in connection with the development of racing engines, when I received the honour of an invitation to read a paper for the Royal Aeronautical Society, I chose this title because it gave me a chance to further the cause of the liquid-cooled engine and to interest you in possible developments of engines suitable for high speed and other types of aircraft.In attempting to forecast possible developments, I am taking a grave risk, as anything connected with aeronautical engineering is doubtful owing to the rapid changes which take place in a short time, and I can only indicate where I think improvements can take place, based on present progress, and can only hope that my remarks will invite criticism and discussion.During the paper the “ hardy annual ” ‘ frontal area ’ will be raised; a slide will be shown of a liquid-cooled engine superimposed over an air-cooled radialof the same b.h.p.

SummaryAn appreciation is made of recent experimental and project work of relevance to the design of a very light weight aircraft capable of being taken off and flown by two men. The emphasis is on the aerodynamic problems involved. It is concluded that, although there are many difficulties still needing attention, all the information supports previous assertions that flight by muscular power alone is possible. The merits and de-merits of a particular projected design are studied, and its performance and stability assessed.

The electrical power demand in aircraft has shown a very marked increase in recent years consequent on the development of many new airborne electrical devices in the field of armaments, communications and the control of flight. Whereas not many years back the total demand on the largest aircraft could be supplied from a small windmill driven generator of fractional kilowatt output, designs are now in existence requiring 24 kW. generating capacity, while larger loads are projected for future types.The power distribution problem has therefore been widely modified and the increased importance of the electrical services performed has considerably raised the status of a onetime Cinderella.

The author accepted the invitation to present this paper on the rash assumption that he would be able to present something new and useful on the tilt-wing. The Hiller Company (in partnership with Vought and Ryan) was the first to have received a fully-fledged development contract for evaluation quantities of any VTOL machine. The VHR-447 which was selected as the Army, Navy and Air Force XC-142A was a culmination of almost ten years of effort spent in the investigation and promotion of the tilt-wing “propello-plane” VTOL aircraft concept.

In choosing the title, “The Development of All–Wing Aircraft,” as the subject of my lecture I run some risk of being accused of writing a company history rather than a paper of the broad scope ordinarily presented before this time–honoured institution. This is far from my intent, but being sincerely convinced that the all–wing aeroplane is a valuable step in the development of aeronautics, and desiring to contribute a maximum amount to the available data in the limited time at my disposal, my paper must be confined largely to experience gained by our company in its work on this subject.

Many “figures of merit” for the comparison of aircraft have been advanced at various times, but in those cases where the basis of comparison has been logical no consideration has been given to first cost, while in those cases where money cost is included, serious objections can be raised to the value of the comparison made.

Before assessing future developments of agricultural aircraft, it is interesting to study the trends of the industry over the past five years.In England, after a promising start, which it is now apparent was occasioned by a heavier-than-normal attack of pest and disease, it soon became evident that large scale operations could not be undertaken profitably due to low fleet utilisation and numerous operational problems which arose from the use of existing fixed-wing aircraft. The major operational problems which hampered large scale operations were shortage of acceptable landing strips, small fields and a high incidence of obstacles.