Propeller Performance Tests of Wright Brothers' "Bent-End" Propellers

Abstract

A pair of Wright brothers bent-end wooden propeller reproductions were tested in the Langley Full Scale Wind Tunnel to document the Wright brothers’ pioneering propeller design contributions, achieved during the e rst decade of powered human e ight. Measurements have cone rmed the effectiveness of their ingenious use of Wilbur Wright’ s blade element theory, exploiting large-diameter propellers, turning at low rotational speeds. Their optimized propeller designs utilized rearward blade sweep and incorporated a type of composite e ber tip covering (over their laminated spruce propeller blades ) to produce propellers with maximum efe ciencies above 85% at nominal advance ratios slightly above one. Not only did their circa 1905 propeller designs approach modern wooden propeller efe ciency levels, but their lightweight, laminated wood construction and manufacturing techniques produced propellers that were structurally strong, which enabled the Wright brothers to retain their basic propeller designs for the entire life of the Wright Company. The Wright brothers’ intuitive approach to airplane design, coupled with their desire to commercialize their e yers, interfered with technical dissemination of the theory behind their propeller designs; thus, the work of others became the basis for the evolving methodology for propeller design. The Wright brothers’ achievements are discussed in the context of the published propeller research of their time.