“Potential” leads are used to put strain gauge switches and leads in series with high resistance ratio arms in a modified Wheat-stone Bridge. Thus the effects of switch contact resistance change and temperature-resistance change in leads can be minimised to any desired values. The high resistance ratio arms allow coarse resistance changes at the measuring bridge to measure the small resistance change at the gauge due to strain.

High potentials are applied to the bridge to minimise the effects of thermal e.m.f.

Active gauges and the temperature compensating gauges are in circuit for only a few seconds while the measurement is made.

In this paper an attempt has been made to trace the influence of gross weight, as the accepted measure of size, upon the dimensions of hulls and fuselages and from this, to evaluate the probable trend of the weights of these components with increasing gross weight.

During the past few years the size andgross weight of aircraft have rapidly increased and there appears at the moment little, if any, structural limit upon the size and gross weights attainable, since it can be shown that the percentage weights of hulls and fuselages tend to decrease as size increases.

In 3.2.1 it was indicated that ξ i, η i may be found from the appropriate co-factors of the secular equation and appear directly as functions of the geometric and elastic properties of the root cross-section. The method will be applied in 5.6.2 for the four-boom tube, in 5.7.3 for the n-boom tube, and in 5.8 for the trapezoidal tube with direct stress carrying top and bottom panels. This procedure is advantageous when it is desired to study the effect on ξ, η of varying particular parameters of the cross-section.

However, when in any case the h-functions have to be obtained, it is often more expedient to determine ξ, η by one of the following procedures.