Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/427

Rh Owing to the spin of the disc this will be angular momentum of aspect, and the successive positions of the disc are as represented in the figure; as a secondary consequence the flight path is diverted from its original direction, owing to the lateral component of the pressure reaction. Thus if we throw a disc in the manner illustrated so that the direction of the spin viewed from above is counter-clock, it will first tilt to the right and then undergo a change of course in like direction.

Fig. 190 (1/3 full size).

Let us now examine, under similar conditions, the behaviour of a boomerang. Instead of the simple disc, a boomerang., Fig. 192, is projected horizontally with a counter-clock spin about a vertical axis. It is evident that the centre of pressure may still be in advance of the centre of gravity, but in addition to this the centre of pressure is displaced laterally. If we adopt the treatment of