Hughes XH-17 "Flying Crane"

The XH-17 began as a ground test stand for a huge tip-jet-powered rotor system. In 1949, Hughes Aircraft got a contract to turn it into a flying machine. The giant rotors promised a huge lifting capacity, so they were attached to stilt-like legs and a box-like fuselage. Cargo such as radar vans could be driven underneath and lifted away. It was proposed that tanks could be carried this way, but as an operational aircraft the XH-17 was just too bulky and cumbersome to be practical and had a range of only 64km, well below the US Army's requirement. The rotor blades were subject to vibration stresses and the XH-17 was frequently grounded. After three years of sporadic testing, the whole programme came to an end when the one set of rotors reached the end of its design life.