I am very appreciative of the honour that has been accorded me in being invited to deliver the Second Lanchester Memorial Lecture: appreciative, but all too conscious of my own inadequacy. This is especially true, since in the first Lecture we heard a tribute to a very great man from another such: and the prospect of following von Karman to this lectern is one to deter perhaps all but the most foolhardy. Since von Karman’s address discussed very fully the contributions of Lanchester to aeronautics, little is left for subsequent lecturers on this subject, and I have therefore chosen to speak of a problem which has been my special interest and concern throughout my professional life, namely, aeroelasticity—a field in which, as in so many others, Lanchester was a pioneer.

I would thank you for the honour you have done me by the invitation to give this lecture.

The admiration I have always had for the engineer founder of this famous Derby firm, and the affection for the firm itself from many contacts over the years, both as an itinerant fuel development engineer and, later, as an official in a Government Department, makes this a very pleasant occasion for me.

Aircraft operate within a domain of altitude and Mach number, the limitations to which are prescribed by the present state of technical knowledge. With the perfection of the aircraft gas turbine we have witnessed the boundaries of flight recede beyond the sonic barrier and are now approaching the stage where the vastly improved propulsiorl technique will permit cruising supersonic flight. Several excellent papers referring to this subject have been given.

A surface-to-air guided weapon system is the result of many years work by a large and diverse team and includes radars and fire control equipment as well as the actual missile. In the time available it is impossible to cover the whole weapon system and therefore no apology is made for concentrating on the development history of the missile itself. It must be remembered, however, that there are many parts of the Bloodhound weapon system, a major contribution to the whole, which will not be mentioned.

The last occasion on which a lecture was given to the Society on the subject of digital computing was in 1954, when Dr. Goodwin, of the Mathematics Division, N.P.L., spoke on “ The uses of the ACE Pilot Model Computer.” At that time there were very few electronic digital computers in regular operation in this country and only one was primarily engaged on aeronautical work.

In a recent note, Fessler has suggested that some of the practical problems of strut testing can be overcome by using a “tensile strut-testing machine”. As Fessler points out, slender struts are frequently tested with pinned ends, either in the form of knife-edges or ball-ends.

Liaison between the engineering and computing sections of an aircraft company suffers when the engineer feels he is “losing control” of his own problems. This situation is typically due, not to distrust of the calculating engine, but to variance in the numerical methods favoured by the engineer and the engine programmer.