Aero Products Propeller, Contra-Rotating, Variable-Pitch, Six-Blade, Metal

What became the Aeroproducts Propeller Company began in 1935 as Engineering Projects, Inc. of Vandalia, Ohio. It was founded by two brilliant engineers, Werner J. Blanchard, who spent several years with the Curtiss Electric Propeller Company, and Charles. J. MacNeil.

Engineering Projects was bought by General Motors in 1940 for a speculated price in the $500,000 range and renamed the Aeroproducts Division of GM. The company delivered only 73 of the novel "Unimatic" Aeroprop propellers in December 1941, rising to 12,500 props in February 1944. Aeroproducts evolved to become a Division of Allison in 1952, and eventually the propeller business was sold to Hamilton-Standard in 1990.

This Aeroproducts contra-rotating propeller with three blades for each of its two stages was used on the Allison T-40 turbo-prop engine in the post-World War II Convair "Tradewind" flying boat and the Douglas "Sky Shark" Navy fighter. Both aircraft were unsuccessful in practice for reasons including engine unreliability problems.