The author's experience in flying dates from before the war and includes a good many years as a naval test pilot, over 5,000 hours of actual flying time in the air in some 360 different types of aeroplanes, ranging from purely experimental to large modern passenger transports and the latest single-seater fighters, and the interest created by some of his experiences has prompted him to attempt some consideration of the complex problem of spinning.

The phrase “tail spin” was probably adopted by reason of the fact that when an aeroplane is in this manoeuvre, it appears, from the ground, as though the nose were pointed straight down and the tail was describing a circle, whereas a spin is a complicated manoeuvre and the nose is actually travelling in a helical flight path, the radius of this helix being relatively small.

Recent contributions to the theory of structures with particular reference to the design of aeroplanes have dealt with the theory of frames in which the members are rigidly connected together at the joints; the object being to ascertain the degree of increase in strength of the individual members due to the restraint at their ends supplied by the contiguous members.

Briefly, when a member forms part of a rigid-jointed structure it acquires a rigidity arising from the rest of the structure. The amount of rigidity given by the rest of the structure may vary from zero end fixation to full encastreing.