It cannot fail to be a subject for remark that in spite of the very large amount of work which has been done in this country on the subject of formal stability calculations, these calculations do not form a part of routine design of the majority of aircraft firms, nor are they used by the Air Ministry as a standard process of checking the aerodynamical qualities of an aeroplane. I use the term “ formal ” stability calculations to cover the solutions of the equations of motion of an aeroplane in rectilinear flight developed from Bryan's work.

Airscrews are generally made of wood and owing to the relatively low Young's modulus of timber the blades of an airscrew have a large measure of flexibility. This flexibility is reflected in the comparatively low frequency of vibration of the blades with consequent undesirable effects. Firstly, there is a tendency for the blades to heat resulting in the laminations becoming unstuck, and secondly, there is considerable danger from resonance between the frequency of the blades and the firing impulses of the engine driving the airscrew. The result of this is heating and burning of the boss and ultimately failure of the airscrew. It may even result in failure of the airscrew shaft by shearing.

The storage of aircraft is sometimes regarded as a matter of secondary importance, but to maintain good efficiency and reliability considerable attention must be devoted to the aircraft during the time when it is not actually in flying condition. Storage in an indiscriminate manner leads to a rapid deterioration, with a consequent financial loss and the introduction of other elements which may be exceedingly dangerous when the aircraft is afterwards flown.

A complete aeroplane or seaplane, or any of its components, calls for separate and distinct methods of treatment and these methods have now been formulated, being based chiefly on experience gained by operations of trial and error.

Not only the aircraft, but also the buildings in which it is proposed to store aircraft, must carefully comply with certain conditions, as however much care is taken with the aircraft, a badly constructed or unsuitable building may counteract all efforts to maintain the aircraft in a serviceable condition and be the cause of scrapping valuable machines.

For some time it has been recognised that the aerodynamical theory of the screw propeller, as at present presented, leaves considerable room for improvement. The leading specialists in this branch of aerodynamics, such as Mr. Fage, Mr. McKinnon-Wood and Dr. Watts, have given recognition to the all-important fact that a velocity of inflow can only, be produced by the mutual interfering action of the propeller blades upon each other. Dr. H. C. Watts was, I believe, the first person to point this out clearly, and to show that the hitherto accepted theories of inflow rested upon a highly empirical basis. By “ velocity of inflow ” is meant the additional velocity required to modify the method of propeller analysis, known as the blade element theory, originally enunciated by S. Drzewiecki in 1892. The accepted and standard inflow theory of the airscrew, as, for example, given in Professor L. Bairstow's “ Applied Aerodynamics,” rests upon the empirical assumption that the ratio (velocity of inflow)/(velocity of impressed slip) is a constant for all propellers and for all radii along the propeller blade length.

You all know those jolly words from “ Alice's Adventures through the Looking Glass,” and in a measure we are about to push our way through the melting mirror of hearsay to the strange world of wonderful facts, where boats fly, and men think nothing of the sort of ascent that blew the breath out of the poor White King when he received his first dusting in the air. We will talk, you and I, of shoes for aircraft—ships that fly and sealing wax that guards the secrets that have made the British seaplane the greatest example of its kind in all the wide world.

First of all you would like to find out, I know, how aircraft manage to fly at all.

You can find that out easily. Take a large box lid or other flat surface, hold it up vertically before you and run across the room with it.

“ The time has come, ” the Walrus said,
“ To talk of many things ;
Of shoes and ships and sealing wax,
Of cabbages and kings. ”
Lewis Carroll

The power plant of an aeroplane is usually designed by a different person situated in a different works from the aeroplane designer, yet it is essential that both should understand something of each other's work, if the best result is to be attained. It is of the first importance that the engine designer should have a clear idea of the value to the aeroplane designer attaching to low weight per b.h.p. and low fuel consumption per b.h.p., when considering a new design or comparing the merits of existing ones.

The greatest deterrent to the growth of air travel is the fear of fire in the minds of potential passengers. It is not a groundless fear, for there must be few members of this Society who have not lost friends and acquaintances from this cause. Unfortunately, the fuel at present in use in all aircraft is of a highly inflammable nature, as is the hydrogen with which airships are filled. So long, however, as oxygen can be kept from mixing with the gas or fuel a fire cannot occur. The problem of abolishing the risk of fire in the air resolves itself into finding the best method of excluding the oxygen from the combustible material. The means adopted must be light, otherwise the aircraft could not use them, cheap and capable of application in any part of the world.