You might have guessed that the client for such a fantastic machine was none other the Uncles Sam himself. Or, more accurately, the US Air Force wanted an air crane with outstanding capabilities: lifting and transporting an external payload of 8x8x20 feet (2.4x2.4x6.10 m) weighing up to 10,000 lbs. (4,536 kg) at a top speed of 56 knots (65 mph, 105 kph).
Moreover, the heavy hauler needed to hover at an altitude of 3,000 feet (915 m), have a tactical range of 87 nautical miles (100 miles / 160 km), and have 30 minutes of autonomy. The military wanted the new aircraft to move several types of payloads – from radar trucks to troops, supplies, ammo, or equipment – to and from areas where even a conventional helicopter would not be able to land. And finally, the flying lifter had to be easy to assemble and dismantle to be transported with relative ease using standard military air, land, and sea equipment.
Such unseen or unheard braveries could not have passed unnoticed by Howard Hughes, the eccentric aviator and billionaire, so in 1949 he got the contract to build the experimental helicopter. A scaffolding-like landing gear – duly borrowed from two airplanes, Douglas C-54 and a North American B-25 – provided the frame which would accommodate the cargo.
The most critical aspect of this heli-monster was, undoubtedly, its engine and rotor assembly. Twin General Electric modified J35 turbojets turned the 130-feet-long (40 meters!) dual-blade propeller. The burners would also send bleed air to the rotor hub from the compressors. This air jet traveled through the hollowed-out blades and fed the fuel’s combustion at the tips.
The jet engine duo would thrust 3,480 hp at the nominal rotor RPM of 88 (half of the typical helicopters of the day), but it was enough to meet the requirements of the Air Force. Work on the XH-17 began in 1949, but some financial difficulties of Hughes’ associate postponed the project for two years. Finally, in 1952, on October 23, the massive Frankensteinian aircraft was ready (you can admire it in the gallery).
With the newly licensed tail number 50-1842, the XH-17 made its maiden flight with pilot Gale Moore at the stick. The event occurred in Culver City, California, but lasted for a bare minute because of overwhelming directional control forces. Hughes engineers ran into more challenges while trying to fix the initial mishaps, and the project never made it past the prototype stage.
It was far less than what the Air Force required, and no technological solution managed to overcome this issue. So, in December 1955, the project was scrapped, but it did serve an essential purpose: it demonstrated that an airlift of enormous proportions was possible and practical.
At the time of its construction, the XH-17 had quite impressive specs: 53 feet long (16 m), 30 feet tall (9.2 m), and an empty weight of 28,562 lb (13 tons). Three crew (pilot, mechanic, and in-flight engineer) operated the massive flying machine.
Although never tested, the XH-17’s calculated performance was impressive: a top speed of 78 knots (90 mph, 140 kph) at 8,000 ft (2,438 m). Cruise speed was a steady 74 knots - 85 mph (137 kph), and it could climb to 13,100 ft (4,000 m) at a rate 1,650 ft/min (8.4 m/s). While it never passed the test stage, the XH-17 remains one of the most illustrious aircraft ever to honor the flying forces of the world.