Wood to Metal: The Structural Origins of the Modern Airplane

The transition from the wood-and-fabric airplane to the all-metal airplane was essentially complete by World War II. The late 1920s and early 1930s are said to have witnessed a structural revolution in aeronautics with the appearance of streamlined metal aircraft with such features as tightly cowled multiple engines, variable-pitch propellers, retracting landing gear, and stressed-skin aluminum construction. A prevalent assumption regarding this transition is that the building material acted as a primary driver of change, that engineering advance was guided by an inevitable move toward metal structures. Metal did indeed allow engineers to extend performance parameters afforded by innovative structural designs, but, interestingly, many of these key innovations were not developed to takeadvantageof metal. They emerged independent of theconstruction material, and often weree rst used in wooden airplanes. The cluster of original ideas that coalesced in the 1930s constituted one of the major watershedperiodsin aerospacetechnology.Metalcarriedthisbasicdesign revolutiontothelimitsofitsengineering andtechnicalfeasibility,butonlyafteranewfoundationwasinplace.Metaldidnotspawnthestructuralrevolution. An exploration of therootsof the structural revolution in aeronautics and thecomplexity oftechnological progress is presented.