Standard Steel Ground-Adjustable Pitch Propeller

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

Charles Lindbergh's Spirit of St. Louis is suspended from the ceiling in the National Air and Space Museum's Milestones of Flight gallery.