The cantilever in fixed-wing aircraft design, pioneered by Hugo Junkers in 1915. Early aircraft wings typically bore their loads by using two (or more) wings in a biplane configuration braced with wires. They were similar to truss bridges , having been developed by Octave Chanute, a railroad bridge engineer. The wings were braced with crossed wires so they would stay parallel, as well as front-to-back to resist twisting. The cables generated considerable drag, and there was constant experimentation on ways to eliminate them.
It was also desirable to build a monoplane aircraft, as the airflow around one wing negatively affects the other. Early monoplanes used either struts (as do some current light aircraft), or cables (as do some modern home-built aircraft). The advantage in using struts or cables is a reduction in weight for a given strength, but with the penalty of additional drag. This reduces maximum speed, and increases fuel consumption.
The most common current wing design is the cantilever. A single large beam, called the spar, runs through the wing, typically nearer the leading edge. In flight, the wings are generate lift, and the wing spars are designed to carry this load through the fuselage to the other wing. To resist fore and aft movement, the wing will usually be fitted with a second smaller drag-spar nearer the trailing edge.
Cantilever wings require a much heavier spar than would otherwise be needed in cable-stayed designs. However as the size of an aircraft increases, the additional weight penalty decreases. Eventually a line was crossed in the 1920s, and designs increasingly turned to the cantilever design. By the 1940s almost all larger aircraft used the cantilever exclusively, even on smaller surfaces such as the horizontal

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