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08/31/2007. The Bö 46 two-seat high speed research helicopter was built to test the Derschmidt rotor that incorporated five glass-fibre rotor blades that were able to advance and retard 40° each side of the normal rotation, delaying the onset of compressibility effects and the possibility of tip-stalling. Three aircraft were ordered by the Bundesministerium der Verteidigung (German Federal Ministry of Defense), the airframes were constructed by SIAT at Donauwörth. The pictured first helicopter started the test program on January 30, 1964. The power plant was an 800 shp Turboméca Turmo IIIB shaft-turbine engine. One helicopter was to have been fitted with two additional 882 lb (400 kg) s.t Turboméca Marboré II turbojets, mounted on each side of the fuselage, for high speed trails. However, the program was halted by 1966, for various reasons, including the failure of the rotor under continued testing.