A crucial step in propeller development was a new design that consisted of a steel hub joined to aluminum alloy blades. It was capable of having its pitch changed by mechanics and pilots on the ground. A new generation of pioneering aircraft, most notably Charles Lindbergh’s Ryan NYP Spirit of St. Louis and Amelia Earhart’s Vega, used the new ground-adjustable-pitch propeller. Commercial and military operators used them as aviation grew in importance during the late 1920s and early 1930s
