In the Wilbur Wright lectures we commemorate, and pay our tribute to, that pioneer work upon which the art of flying is founded and it is only now that carrying our minds back to those early days we see how thorough were the methods which led to success. The work of Lilienthal in gliding with curved wings—brought to an untimely end through lack of control—had shown that the secret of success was to be found in free flight experiment. Then came the great contribution of the Wrights, who discarded Lilienthal's acrobatic control and carrying through the whole modern programme of wind tunnel research, detail design and construction, found out by practical flying that essential feature of control which has been used in practically every aeroplane that has been flown.

In the original Wright aeroplane, as in all its successors of fixed wing area, the only means used for varying the lift was by alteration of the angle of incidence or of the camber of the wing either by warping or by the equivalent use of ailerons.

It is proposed to confine this paper entirely to the point of view of the propeller constructor.

More than 90 per cent, of the propellers now in use are constructed by shaping from a block formed by the glueing together of hardwood laminations. This type is cheap to produce either individually or in quantity, and has been proved by experience to be satisfactory for all types of aircraft, for tip speeds up to 1,000 feet per second, diameters up to 19 feet and for engines developing over 1,000 b.h.p., without showing any signs of having reached a structural limit.

This construction was standardised for production purposes by the Air Ministry during the War, and the official Handbook of Instructions is a most complete guide to the method of manufacture.

Other forms of construction are, to a certain extent, still in the experimental stage and will be considered chiefly by comparison with the standard type.

This paper should be regarded as a continuation of the one I read before you last session and is intended, primarily, to cater for those who wish to sit for a Ground Engineer's Licence.

My previous paper dealt with the alignment and checking of fuselages. I propose in this paper to deal with the alignment of certain other components, and also with the inspection of components.