The Hughes XH-17 “Flying Crane” was a prototype heavy-lift helicopter developed during the 1950s. The design wasn’t actually an original Hughes project. Initially the project was developed by Kellett Aircraft Corporation to fulfill a 1946 US Army requirement for an extremely large helicopter capable of lifting up to 10,000 lbs (4,536 kgs), at a speed of 64 mph (105 km/h), over a range of 100 miles (160 km). However Kellett ran into financial difficulties during the preliminary development of the aircraft, and in 1948 they sold the rights and partially completed prototype to Hughes. Several members of the original design team were hired by Hughes to help make sure the project stayed on track.
The test rig was completed in 1949, and in order to speed up construction numerous elements had been poached from existing aircraft. The two-seat cockpit came from a Waco CG-15, the undercarriage was made up from North American B-25 and Douglas C-54 parts, and the fuel tank came from a Boeing B-29 bomb bay tank. The XH-17 employed an unusual gas-turbine and rotor-tip combustion combination to provide power to spin the gigantic rotors. Two General Electric gas generators – modified J35 turbojets – sent compressed air to the rotor tips where fuel was added and then burned to provide the equivalent of 3,480 horsepower.
Ground tests began towards the very end of 1949, and immediately the sheer size and complexity of the rotors, and their unusual powersource began to throw up some issues for the engineers. However the project continued to develop at a satisfactory pace until June 1950 when the test rig was badly damaged when a cyclic gear failed. It was the first major setback for the aircraft. However the Air Force had been sufficiently impressed with the XH-17’s initial tests to request that the static test rig be upgraded to a flying prototype.
Modifications included the fitting of a hydraulics system and the addition of a tail rotor, in this case one pinched from a Sikorsky H-19. It wasn’t until 1952 that the Hughes XH-17 was ready for its first flight. Piloted by Gale Moore, it took to the skies on 23 October. However just over a minute after take-off it was back on the ground. This was because Moore had experienced difficulties in directional control of the aircraft. Thankfully that particular issue proved fairly simple to rectify, and the XH-17 was soon lumbering skyward for more test flights. There were however issues which proved harder to overcome. Of primary concern was the high vibratory stresses experienced by the main rotors. Numerous modifications were made over the next three years and progress was slowly made. However it all proved to be in vain. In 1955 when the rotors came to the end of their airworthy life, and a new set were required, the military pulled the plug.
By the end of the test program the XH-17 had proved its concept, that it could fly, and that it could carry a considerable payload – exceeding the original requirement. However it fell short, well short, of the Air Force’s range requirement. Mainly due to its appalling fuel consumption, and there was little which could be done to improve it.
In the end it became a bit of an engineering cul-de-sac. One derivative, the XH-28, an even larger version, was proposed. But it never got further than a wooden mock-up. The sole XH-17 prototype was eventually scrapped, and sadly nothing remains of this unusual giant except for photos and some video footage.