I am very conscious of the privilege and honour of being asked to deliver the first R. J. Mitchell Memorial Lecture. The presence of such a distinguished audience, and the fact that I feel the subject is one to which it is difficult to do full justice, are factors which do not tend to fill me with confidence, and I hope you will forgive any inadequacies. From a mass of recollections arising as the result of fourteen years of contact with Mitchell, I hope to give you my impressions of the life and career of that great designer.

The 890th Lecture to be given before the Royal Aeronautical Society was held at the Institution of Mechanical Engineers, Storey's Gate, London, S.W.I, on 12th November 1953, and was presided over by Sir William Farren, C.B., M.B.E., M.A., F.R.S., F.R.Ae.S., President of the Society. Introducing the lecturer, Sir William said that Mr. Wimpenny had been with the de Havilland Company throughout his career in aviation and had been responsible for some years for the design and development of stability and control of the de Havilland aircraft, including the Comet, so that clearly he spoke with a wide knowledge of his subject.

It is now the usual practice in Great Britain to estimate the “ safe ” life of an aircraft wing from fatigue tests which are carried out on specimens representing the more highly stressed portions of the tension boom or booms. Such tests are designed to produce a tensile load in the boom equal to that produced in steady flight, and superimposed on this, a small fluctuating load corresponding to that which would be produced by an up gust immediately followed by a down gust of the same magnitude.

The Torsion-Bending Constant of open sections is of great importance in the calculation of buckling loads under compression of struts failing in the torsional or torsional-flexural mode. It involves computation of the warping of the cross section and misunderstandings arising out of terminology and notation often mislead the users of the formulae. The purpose of this note is to clarify the terminology without going into proofs as well as presenting the equations required using a consistent notation.

Two recent contributors to Technical Notes have expressed the view that, in rocketry, specific impulse should be defined as thrust/mass of propellants consumed per second, rather than as thrust/ weight of propellants consumed per second. The only reason given in support of this view is that the weight of a given mass varies with location. Our purpose here is to give reasons for taking the opposite view, namely that the second definition is preferable.

It would seem that Mr. Heughan (Journal, March 1954) has missed the basic design criterion of drag exerted for a given weight (and bulk) penalty. No mention is made of this fundamental point in the choice of a device for the reduction of the landing run of an aircraft. The choice of comparison of the “Wake brake” with a 7 ft. brake parachute has therefore been made somewhat arbitrarily. Brown does not state that “the usual size of a parachute used for braking an aeroplane is 7 ft.”; on page 271 of the reference concerned (“Parachutes,” Sir Isaac Pitman, 1951), a case for “a particular aircraft” was quoted as “ using a 7 ft. parachute.”