Recent investigations show that “ shear lag ” has a small effect on the distribution of the bending stresses in the section ; but the effect of the stiffness variation, of the various parts of the structure, has a considerable bearing on this distribution.

Compression tests on panels of wing covering comprised 20 S.W.G. and 22 S.W.G. plating, with stringers of 18 S.W.G. to 22 S.W.G. rolled sections, show that, due to the bowing and waving of the light covering and stringers, the effective E is reduced to about 4.5 × 106 to 5 × 106 lbs. per sq. ins. for light alloy panels of these sizes. Compression tests on light alloy extruded struts show a value of E of 10 × 106 lbs. per sq. ins.

In this paper a simple approximation method is presented for rapidly computing the lift distributions of arbitrary aerofoils. The numerical results are compared with those obtained by an exact method and for many purposes show a satisfactory degree of accuracy. The latter, for all practically occurring cases, can be estimated at the start of the computation work with the aid of the comparison examples given.

The stresses in annular frames of constant flexural stiffness, as they occur in thin-walled shells are determined, assuming a finite depth of frame cross-section. The calculations are carried out for the fundamental load cases and the results presented in the form of diagrams.

It often happens that in a plane truss all joints are not transversely stiffened. If one joint of the compressed girder of a beam is free, the girder is liable to fail by buckling perpendicular to the plane of the truss, between the adjacent joints. The chart given here enables a rapid determination of the critical loading to be made. The compression and moment of inertia are assumed constant along the length of each bay, but may be different in the two bays.

The constructional elements of single-spar wing structures are main spars, torsion tubes, ribs, and auxiliary spars. The ribs, which generally extend over the entire wing section, are for the purpose of stiffening the torsion tubes and taking up the forces in the torsion tubes and in the main spar. Mounted structures in the wing, engine, and landing gear often make it necessary to build up only one-half of the wing cross section completely with flanges and webs as a flexural supporting member. The other half of section is then omitted entirely or only the flanges are retained.