During World War I, Frank W. Caldwell became the Chief Engineer in the Propeller Research Department of the Engineering Division, a predecessor to the Aerospace Systems Directorate, based at McCook Field. While at McCook and Wright Field he was responsible for all aircraft propeller development. Caldwell designed the whirl test by mounting propellers on a stand to measure their thrust, endurance, speed, efficiency, and structural strength. Caldwell eventually developed the variable-pitch propeller allowing for in-flight adjustments for maximum performance. In 1933, he and his group at Hamilton Standard were awarded the coveted Collier Trophy.