IN AIRCRAFT ENGINEERING for June, 1935, and in R. & M. 1715, the present writer and others described some experiments on a wing cellule model of a new form of biplane, the special advantage of which was stability in roll up to angles of incidence as high as about 40deg.; and it was suggested that if the results of the model experiments were borne out on the full scale such a type of biplane might with advantage be adopted for a light sporting machine with a view to minimising the risks due to the inadvertent stall.