The first variable-pitch propeller developed in the United States was invented by Seth Hart and Robert I. Eustis of Los Angeles, California, and demonstrated in 1917. Possibly the second variable-pitch propeller in the United States, this 1920 controllable and reversible propeller is the product of the first government sponsored variable-pitch propeller development program. It was completed following a two year development at the Engineering Division, McCook Field, Dayton, Ohio, and is an improved version of a design submitted to the Army for evaluation in 1918 by Hart and Eustis. This propeller had a faulty blade retention system, and was unable to keep wooden or Micarta blades connected to the hub.
This object is not on display at the National Air and Space Museum. It is either on loan or in storage.