08/15/2008. Remarks by Ray Watkins: "In 1959 the US Army's Transportation Research Command (TRECOM) conducted investigations into alternative rotor systems and methods of drag reduction for helicopters.
The fourth Model 204 YH-40-BF was modified with a streamlined rotor mast fairing and flush engine air intakes to become the Model 533. It was tested with 2-, 3- and 4-blade rotor systems, and later two Continental J69-T-9 turbojets and 2 small swept wings were fitted. The final modification, in 1968, was to install two Pratt & Whitney JT12A-3 turbojets on the ends of a stub wing. The picture shows the Model 533 with a 4-blade rotor, J69 engines and swept wings."
