Preliminary Static Test of a Magnesium Alloy Wing

Abstract

FOR THE PAST THREE YEARS there has been increasing interest in the application of magnesium alloys to aircraft structures. In order to determine the possible weight saving and general suitability of magnesium alloys for aircraft construction, the Bureau of Aeronautics and The Dow Chemical Company have cooperated in the design, construction, and static test of a wing that was directly comparable to an aluminum alloy structure. The preliminary static tests have been recently completed and an appreciable weight saving is indicated. This paper describes the design and test of the structure and makes interesting comparisons with aluminum. Following these static tests, a period of flight testing on several sets of wings will determine the ability of the magnesium to stand up under various service conditions. Generally speaking, the material is going through the same development cycle as aluminum alloys, with similar difficulties in forming, surface protection, etc., as were experienced in the early days of aluminum airplane development. Service tests may indicate the need for modifications in detail design or improvement in the alloys. As with other experimental projects of this kind, some complications arose from the requirements imposed by fitting the new structure to an existing one. The ordinary theories of stress analysis assume known conditions at the root of a wing where it is attached to the center section or fuselage. Actually, most outer wing panels are bolted to a center section of unknown and varying rigidity which in reality is a flexible foundation wherein the actual deflections of the supporting structure under load are unknown. In order to demonstrate a new type of construction or to test a new material, it is common practice for the Government to procure experimental outer wing panels to attach to center sections of this type (see Fig. 1), and the designer is confronted with the problem of seeking to prove a new material or type of construction under extremely difficult conditions. He must make his structure as light as possible and still meet the strength requirement. At the same time, he must not cause failure in an existing center section to which reinforcements may not be