Page:Aerial Flight - Volume 2 - Aerodonetics - Frederick Lanchester - 1908.djvu/219

Rh '''§ 108. On the Aerodromic Radius.'''—The aerodromic radius could evidently be determined experimentally on the lines proposed for the aerodynamic radius in § 106, the axis or pivot on which the aerofoil is mounted being arranged vertically instead of horizontally; the forces to be measured are, however, comparatively small (commonly from one-sixth to one-eighth of the vertical reaction), and the apparatus would require to be appropriately sensitive.

From the theoretical point of view, if the form of the aerofoil were that discussed in § 120 of Vol. I, the problem would be greatly simplified, for the aerodynamic and aerodromic radii would be equal. We know, however, from §§ 190, 192, that such a form does not comply with all the conditions, and that the aerofoil extremities have to be formed to give rise to motion of the discontinuous type. In nature we know that the wing terminations are given much diversity of form to this end, and that in general the sectional form should be flattened so as to become virtually an aeroplane at each extremity.

Under these conditions the value of the aerodromic radius is a quantity that, from a theoretical standpoint, we are unable to estimate with any great degree of accuracy in the existing state of knowledge.