High tensile steel wire has many uses in connection with aircraft. A single wire has the advantage of a high breaking stress, greater than that of the bulk material from which it is made, because, as Goodman has pointed out, the drawing produces an elongated stricture of the steel, and the wire strength approximates to the true breaking stress of a larger specimen, which is the tension the latter resists at the moment of fracture divided by the reduced area. The British Engineering Standards Association's specification, 2wi., requires a minimum breaking stress of 80 tons per sq. in. up to 0.160in. diameter, 90 to 0.116, and 100 to 0.064. These stresses can safely be exceeded when required particularly with wire of small diameter.

The method here described has some advantages over the present standard method of designing with continuous spars. Firstly, it gives lighter spars by working as many points as possible up to the elastic limit. Secondly, it is far quicker to use owing to the necessary formulæ and processes of computation being more manageable and to the fact that practically each bay can be designed separately without affecting the others. Thirdly, the roughing out and the final checking are done with the same set of formulæ, whereas, if the usual type of spar construction is adopted, it is necessary to use different methods for the preliminary and final design. Fourthly, the accuracy of the work is not affected by the supports getting out of line when the whole structure deflects under load, a serious error in the older method being thus avoided.