The distribution of stress in an I-beam in torsion is investigated by a method of successive approximation, and the regions of initial yielding are determined for several values of the angle of twist. Formulas are given for elaborating the methods of Southwell and of Shortley and Weller in order to facilitate this determination.

The value of the stress-concentration factor in the fillets is found to agree well with results obtained by soap-film tests, and regions of plastic flow approximate closely those observed by MacGregor and Hrones by the use of the etching method.

When the all-metal cantilever monoplane brought to a close the era of wood, tubes and fabric for aeroplane structures, the new development opened up broad fields for the improvement of aerodynamic efficiency, with resulting great increases in all-around performance, military effectiveness, and economy of operation.

The all-metal fuselage represented a new type of construction in that the skin formed a shell to replace trusses in carrying the bending loads imposed at the tail in flight and on the ground.The scheme of using a shell to give–at once–structural strength and aerodynamic fairing, previously accomplished by two elements, appears to be economical and sound. If the labour now needed for the fabrication and assembly of the multiplicity of internal members is to be eliminated the stresses must be taken in the skin and the principle should, if practical considerations permit, be extended to include the wing and fixed tail units.

Rubber is an indispensable material for the German industry. The yearly consumption is at present about 100,000 tons. For thirty years the German chemical industry has studied the problem of synthetic rubber for engineering purposes, but it has only been in the last few years that the difficulties have been successfully overcome.

The following remarks refer to the fundamental conditions which have to be considered for the use of rubber for the mounting of engines. It is thought essential that aircraft firms should ask for information with regard to rubber components they intend to use at an early stage of the design so that faulty applications of such parts can be prevented. Figures for the permissible loads and hints for the design of rubber components are given, with special reference to the use of Buna. Some constructional features are discussed as an explanation of the advice tendered to the designer.