An Elementary Study of the Spin: A Review of Existing Knowledge on a Problem of Ever‐Present Difficulty

Abstract

In this paper a comprehensive survey of spinning phenomena is attempted. The presentation is elementary in character, starting with the simple geometry of the spin, then dealing with autorotation, including wing‐dropping tendencies, passing on then to a consideration of aerodynamic pitching and yawing moments, and finally some attention is given in turn to the incipient spin, the steady spin and recovery. The arguments are in the main qualitative so that a student of the subject may first familiarise himself with the fundamental principles. A bibliography is given which includes all the important papers published on the subject within the last few years, together with a few which are now more of historical interest. Most of these reports emanate from the A.R.C. and N.A.C.A. and due acknowledgment is made of the source of some of the experiments which have been taken in illustration of the points made. Although not the urgent problem that it once was, the subject of the spinning of aeroplanes continues to occupy a prominent place in the programmes of various research establishments, both here and abroad. Because both of the complexity of the phenomena involved and of the great importance that an ultimate solution should be found it has continued to be since the war one of the most difficult and protracted problems in aeronautics. Owing to the body of experimental data which has been gradually built up, model and full scale, designers now know what peculiar properties in an aeroplane are liable to prove dangerous as far as recovery is concerned. There is unfortunately no mathematical precision about this process and the fact that machines can still be built which, unless they are tested in the spinning tunnel and the necessary modifications made, might become uncontrollable in a spin should be sufficient to indicate that a final solution is far front having been achieved. It seems exceedingly unlikely that there will ever be sufficient experimental evidence to enable a designer to predict confidently that his machine, if it be perfectly orthodox, will not have some vicious spinning tendency. On the other hand, any designer could build a perfectly safe aeroplane from the point of view of spinning if due regard had not to be paid to other items of performance and safety. The necessity for compromise in design becomes a major problem when spinning is one of the factors that have to be taken into account. There is ample evidence that this problem is being resolutely tackled by designers. All the same, the present position cannot be regarded as satisfactory and, unless some new device is produced which will remove autorotation from the possible regimes of an aeroplane, we must continue to progress along already well‐tried lines.

Citation

Crowe, J.H. (1939), "An Elementary Study of the Spin: A Review of Existing Knowledge on a Problem of Ever‐Present Difficulty", Aircraft Engineering and Aerospace Technology, Vol. 11 No. 2, pp. 39-54. https://doi.org/10.1108/eb030434