A meeting of the Royal Aeronautical Society was held in the Library of the Society at 4 Hamilton Place, London, W.l, on Tuesday 25th September 1945, at which M. L. Malavard, of the Laboratoire des Analogies Electriques, Paris, lectured on “The Use of Rheo-electrical Analogies for the solution of Aerodynamical Problems.” In the chair, Mr. E. F. Relf, C.B.E, F.R.S., F.R.Ae.S. (at that time Superintendent of the Aeronautics Division, National Physical Laboratory).

The title of this paper is the result of practical experience in the maintenance of aircraft, combined with a view to trying to improve the design standard in future aircraft. In the past, engineers, especially aircraft engineers, have put up with a considerable amount of poor maintenance design and have gone on improvising time and time again as the only solution to their problems. As a result of this improvisation it is probable that those concerned with the actual design do not realise many of the difficulties experienced in the maintenance of their aerodynamically efficient aircraft.

This note draws attention to the poisonous properties of certain chemicals which have previously been used for transition indication in wind tunnels, indicates which alternatives are safe, and suggests general precautions.

Part 5 continues the theory given in Parts 1–4 in the February 1947 issue of the Journal (pp. 199–269). The present paper deals with the stresses and deformations of conical and cylindrical tubes under arbitrary loading, thus completing the analysis given in Part 4 which dealt only with pure torque.

A remarkable unification of the theory of bending and torsion is achieved. It is shown that the axial constraint stresses, i.e. the corrections to the engineers' stresses, may in general be calculated as if caused by torque about axes different in each mode. The analysis proves that it is in no circumstances correct to calculate the axial constraint stresses from the torque about the flexural axis.

Functions giving the cross-wise distribution of stress are fully worked out for the n-boom tube of arbitrary cross-section and for the singly symmetrical trapezoidal tube with continuous direct stress-carrying covers. The analysis is a considerable extension of the results given for the four-boom tube in Part 4.