Throughout his career, Lanchester’s phenomenal engineering output was directed mainly towards the automobile which proved in his day to be a more suitable vehicle than the aeroplane for the practical application of the products of his genius. Aeronautics remained always a compelling avocation “wholly individual … never backed by funds from external sources”, to quote his own words. During the First World War he did contribute to the practical solution of a serious tail flutter problem on Handley Page and de Havilland aircraft, making him probably one of the first applied aeroelasticians. However, his major contributions, cited in the 1931 award of the Guggenheim medal, were to the fundamental theory of aerodynamics. The full extent of these contributions is still being explored as Dr. J. P. Jones in the Thirteenth Lanchester Lecture points out. His contributions to automotive engineering, on the other hand, were immediately reduced to practice and it therefore seems appropriate in this Fourteenth Lanchester Lecture which it is my great privilege to present, to examine whether, as we continue the full exploitation of his discoveries in aeronautics, the aeroplane will ever be able to complement, possibly even replace to a degree, the ubiquitous automobile to whose practical realisation as a safe, comfortable and reliable transport medium he contributed so much.

The One-Eleven autopilot has been developed in parallel with the aircraft as a whole, being largely prompted by the increasingly sophisticated requirements of our customers, and I am sure you will agree it is a continuing story of achievement of which the British aviation industry in general, and BAC with their sub-contractors in particular, can be justly proud.

The One-Eleven is not one aircraft, it is a “family” of aircraft, each member of the “family” having a unique autopilot requirement and standard of fit (see Table I).

Since the end of the Second World War civil aviation has grown beyond the dreams of the early pioneers and the design, development, manufacture and after sales support of a civil aircraft has become a most complex undertaking, involving a wide range of engineering knowledge and many engineering skills. In the past the approval of an aircraft constructor by the British Civil Airworthiness Authority has rested with the Chief Designer and the Chief Inspector of the company, but as the complexity and the cost of development, production and maintenance of modern civil aircraft has grown, it has become increasingly clear that the responsibility for control of airworthiness lies throughout the whole company.

In a paper published in 1956 the senior author analysed the problem of the creep bending and buckling of a reinforced circular cylindrical shell subjected to the action of a bending moment constant in time and along the axis of the shell. With the aid of the principle of virtual displacements he found that the problem is governed by two simultaneous non-linear first-order differential equations. The equations were integrated step by step with the aid of a desk calculator and satisfactory agreement was found between theory and experiment when the results were compared with experimental data obtained in the laboratory of the Polytechnic Institute of Brooklyn. The experimental investigation and its results were described in ref. 1 as well as in a research memorandum of the National Advisory Committee for Aeronautics and the theory was presented in detail at the Symposium on Structural Problems of High-Speed Flight held at Cranfield, England, in August 1956 and published in the Journal of the Royal Aeronautical Society in 1957.

The need to establish reliable methods of predicting the response of aircraft during taxying on rough runways and the associated dynamic loads and fatigue damage has led to numerous theoretical and experimental investigations of this problem. The present paper is a development of the study reported in ref. (1) which considered the random response of a flexible aircraft to forces transmitted through thei main undercarriage. The purpose of this paper is to apply power spectral techniques to the computation of the response of a rigid aircraft in heave and pitch to runway roughness, taking account of non-linearities in damping in the main and nose undercarriage.