New R.A.F. Types

Solution. The gliding ratio required is 70/6 × 22/15 = 17·1. At present, with an all‐up weight of 500 lb., this is generated at 62 m.p.h.: we require it to be generated at 70 m.p.h. The dividers are therefore set with their points at 62 and 70 on the Forward Speed scale and transferred to the Weight Scale, whence it is seen that the necessary all‐up weight is 640 lb. The ballast required is therefore 140 lb. Application of the dividers to the various scales shows the new performance figures to be: