Curtiss-Wright X-100

The X-100 was built primarily to flight test Curtiss-Wright's concept of using propeller "radial force" instead of wing lift for conventional flight. This phenomenon produces a large force at right angles to the airflow as the propeller angle of attack is increased. The X-100 used a 860 bhp fuselage-mounted Lycoming YT53-L-1 driving cross-shafts for the 10 ft diameter tilting fiberglass propellers at the wingtips. At the rear of its 24 ft fuselage, engine exhaust was used for pitch and yaw control in hover; roll control was provided by differential propeller pitch. Wingspan was 16 ft and gross weight was 3,500 lb. The X-100 first hovered in free flight in September 1959, and made its first short take-off and landing flight on March 1960. Its first (and only) transition from vertical to horizontal was performed in April 1960. Control in hover was weak due to the low exhaust gas velocity. Testing continued until October 1961, sufficiently proving the Tilt Prop concept to the extent necessary to proceed with what would become the X-19.

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