Helicopter designed by Dutch engineer Albert Gillis von Baumhauer. A short first flight was made on 5 September 1925 and a more substantial one on 10 February 1926. The vehicle featured a tail rotor, powered by its own engine, but lacking pitch control. Slow progress was made until the helicopter crashed on 29 August 1930. By then working for the Dutch CAA, Von Baumhauer was killed in the crash of Boeing Stratoliner NX19901 on 18 March 1939. Photo from: Nederlands Instituut voor Militaire Historie