To the Editor SIR, In the January issue of AIRCRAFT ENGINEERING (Vol. XIV, No. 158) there is an extremely interesting article by Payne on “Torsion in Box Beams”. Unfortunately, as with most rigid analyses, a considerable amount of work is necessary before arriving at the final distribution of the applied torque. The scope is also extremely limited. In order to overcome this a simplifying assumption has been made, namely that the proportion of the applied torque taken as differential bending in the top and bottom panels is small compared with that taken as torsional shear and differential bending of the spars, and can be neglected. As a result the analysis is simplified, the numerical computation is made easier and the scope considerably widened. This assumption is perfectly justifiable since:—