XH-17 Sky Crane

XH-17 "Flying Crane"
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Type	helicopter
Manufacturer	Hughes Helicopters
Maiden flight	23 October 1952
Retired	December 1955
Status	Scrapped
Number built	1

The XH-17 "Flying Crane" was the first helicopter project for the helicopter division of Hughes Aircraft. The XH-17, which had a two-bladed main rotor system with a diameter of 134 feet, was capable of flying at a gross weight of more than 50,000 pounds.

Design and development

The XH-17 was a heavy-lift rotorcraft that was designed to lift loads in excess of 15 metric tons. To speed construction, parts of the XH-17 were scavenged from other aircraft. The front wheels came from a B-25 Mitchell and the rear wheels from a C-54 Skymaster. The fuel tank was a bomb bay-mounted unit from a B-29 Superfortress. The cockpit was from a Waco CG-15 and the tail rotor from a Sikorsky H-19 was mounted on a tubular fuselage extension.

In the late 1940s, Hughes developed an interest in helicopters. In August 1947, helicopter manufacturer Kellett sold his design for the giant XH-17 Sky Crane to Hughes. Howard Hughes Jr. commissioned the development of the XH-17 Flying Crane research vehicle. In 1948 aviation pioneer Howard Hughes, Jr. began to turn the giant XH-17 Flying Crane into a flying reality. The giant helicopter was flight tested in Culver City, Calif. over a three-year period beginning in 1952. The XH-17 flew in 1953 flew at a gross weight in excess of 50,000 pounds. It still holds the record for flying with the world's largest rotor system. Only one unit was built, since the behemoth was too cumbersome and inefficient to warrant further development.

File:Hughes XH-17 with cars.jpg

Two cars parked under the XH-17 give some idea of just how big the helicopter really was.

The propulsion system was highly unusual. Two turbojet engines were used, sending bleed air up through the rotor hub. The blades were hollow, and the hot, compressed air traveled through the blades to burners at the tips where fuel was injected. In flight the rotors were designed to spin at a sedate 88 rpm. Since the rotor was driven at the tips rather than by the hub, little torque compensation was required. Thus, the XH-17 had a very small tail rotor compared to its main rotor. This drive system was inefficient, limiting the test aircraft to a range of only 40 miles (64 km).

The XH-28 was a derivative, with a maximum weight of 47,000 kg. The program was cancelled and none were built.

Specifications

General characteristics

• Crew: 3 (pilot, mechanic and in-flight test engineer)
• Length: 53 ft 3 in (16.25 m)
• Rotor diameter: 129 ft 11 in (39.62 m)
• Height: 30 ft 2 in (9.17 m)
• Empty weight: 28,563 lb (12956 kg)
• Loaded weight: 31,270 lb (14184 kg)
• Useful load: 10,284 lb (4665 kg)
• Max takeoff weight: 43,500 lb (19731 kg)
• Powerplant: 2× General Electric GE J35 turbojets

Performance

• Maximum speed: 90 mph (145 km/h)
• Cruise speed: 85 mph (137 km/h)
• Range: 40 mi (64 km)
• Service ceiling: 13,100 ft (3995 m)
• Rate of climb: 1650 ft/min (8.4 m/s)
• Disc loading: 2.34 lb/ft² (11.5 kg/m²)

See also

Comparable aircraft

• CH-54 Tarhe
• S-64 Skycrane

External Links

1952 experimental aircraft newsreel The XH-17 is shown at the end of the newsreel. It is also shown in flight, clearly illustrating the slow rotation speed of the rotor.

References

• http://www.1000aircraftphotos.com/Contributions/VanTilborg/3138.htm
• http://findarticles.com/p/articles/mi_qa3897/is_200104/ai_n8943768
• http://avia.russian.ee/helicopters_eng/mcdonnel_crane.php

Jim Winchester "The World's Worst Aircraft", 2005
Rene J. Francillon "McDonnell Douglas Aircraft since 1920: Volume II", 1997

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "XH-17 Sky Crane".