An interesting item in the above essay, published in the Journal for December, 1931, is the solution, given in Appendix II, of the determinantal equation

ΔN=0,

But before this equation is discussed a dynamical problem will be formulated in the solution of which a similar determinantal equation arises.

Until recently it was believed that Sir George Cayley's note-books had been lost. In 1927 Mr. J. E. Hodgson, the Honorary Librarian of the Society, learnt that a quantity of miscellaneous manuscript papers were in existence in the home of the Cayley family, and permission was obtained to sort out from such papers matter bearing on Cayley's aeronautical and other engineering or technical labours. Among them was the Note-book, which will shortly be published in full by the Newcomen Society, by kind permission of Sir Kenelm Cayley.

March 18th is the 50th anniversary of a free flight of some 40 ft. made at Montesson, near Paris, by Traian Vuia credited by L'Aérophile (September 1906) with being “ the first person in France to have really attempted, with a machine able to carry a man, the direct take-off of an aeroplane having a wheeled undercarriage.”

Vuia, a Rumanian, submitted a paper to the Academy of Sciences in February 1903 which included a description of what he called an “ aeroplane-automobile ” which was a light weight monoplane with wheels and an engine driving a single tractor propeller; it was to be controlled by a rudder and by altering the incidence of the wing.

In 1915, when dealing with various problems connected with Lifting Screws, the author desired to obtain a general idea as to the performance of a propeller when it was moved at various speeds forwards and backwards along its axis of rotation, and to express this information in some simple way, so that the approximate performance of any similar propeller working in a fluid medium of any density might readily be deduced.

If, when comparing the performance of similar propellers working at the same slip ratio, the resistances due to skin friction and viscosity are assumed to follow the velocity squared law, and change of density in the neighbourhood of the propeller is neglected, there are six main factors to be considered.

Measurements were made of the pressure in a blunt-nosed pitot tube, in an air stream at Reynolds numbers from about 15 to 1,000. The results are expressed in terms of a pressure coefficient , where P is the pressure in the pitot tube, ρ is the density of the fluid, and p and V are the static pressure and velocity in the undisturbed stream. As found in previous investigations, Cp becomes greater than 1 at low Reynolds numbers, the increase being about per cent, at a Reynolds number of 50 (based on external tube radius). In disagreement with the work of Hurd, Chesky, and Shapiro, no decrease of Cp below 1 was found at any Reynolds number.

The 820th Lecture to be read before the Royal Aeronautical Society, “Progress Towards Electrical Serviceability,” was given by R. H. Woodall, M.I.E.E., A.F.R.Ae.S., and V. A. Higgs, B.Sc., A.M.I.E.E., A.F.R.Ae.S., on 1st March 1951 at the Institution of Civil Engineers, Great George Street, S.W.I. Major G. P. Bulman, C.B.E., F.R.Ae.S., President of the Society, presided at the meeting and introduced the lecturers. Mr. Woodall is a Director and Chief Engineer of Rotax Ltd., and Mr. Higgs is Head of Technical Sales and Aeroplane and Automobile Sales of the British Thomson-Houston Co. Ltd.

It is evident from remarks made in previous papers or in discussion on those papers, that the Aircraft Industry is not entirely satisfied with the electrical accessories available for use in aircraft.

There may be some grounds for this dissatisfaction, but it is hoped to make it clear that the electrical equipment suppliers are very much alive to their responsibilities and that development on an ever-increasing scale is taking place in order to give the aircraft constructors the most reliable equipment possible.

Aerodynamic theory may be used with reasonable confidence to estimate the low-speed value of the stability derivative I p for wings of most plan forms under quasi-steady conditions so long as viscous effects are unimportant. Wind tunnels tests are made to cover other cases such as the partially stalled swept wing, but the writer has heard of a difficulty encountered by a firm when using the free-rolling method. A variant of that technique in which this difficulty is avoided and which has been used at Imperial College for some years may be of interest.