Changing Structures

As high speeds became sought after, an aircraft’s shape became more important. Parts that stuck out into the air flowing around an aircraft had to be removed or smoothed out to reduce air resistance. The wooden struts and bracing wires between biplane wings had to go. Wood and fabric biplanes were replaced by all­metal monoplanes.

By the 1930s, nearly all new aircraft were monoplanes made from duralumin or similar aluminum alloys. Lots of new alloys with different properties were invented for building different parts of aircraft and spacecraft.

О The Boeing P-26A, nicknamed the "peashooter," was the first U. S. Army low-wing monoplane fighter constructed entirely of metal. This full-size peashooter was mounted for testing in a wind tunnel in 1934.

At first metal airplanes were built in exactly the same way as wooden planes. The structure was the same, and only the materials that were used were changed. The new materials made aircraft heavier, however, and a new type of structure was soon devised. Instead of building an airplane’s body from a strong, heavy, metal frame cov­ered with sheets of metal, a lot of the frame was removed. The thin metal skin itself provided some of the plane’s strength. This is called a stressed-skin structure. To make sure the thin skin did not bend or buckle, it had to be fastened securely to the frame with thousands of metal fasteners called rivets.