Hughes XH-17

https://en.wikipedia.org/wiki/Hughes_XH-17

The Hughes XH-17 "Flying Crane" was the first helicopter project for the
helicopter division of Hughes Aircraft Company. The XH-17, which had a
two-bladed main rotor system with a diameter of 134 feet (41 m), still holds the
world record for flying with the largest rotor system. It was capable of flying
at a gross weight of more than 50,000 pounds (23,000 kg), but proved too
inefficient and cumbersome to be mass-produced beyond the prototype unit.


Role
Helicopter

Manufacturer
Hughes Helicopters

First flight
23 October 1952

Retired
December 1955

Status
Scrapped

Number built
1

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 North American B-25 Mitchell and
the rear wheels from a Douglas C-54 Skymaster. The fuel tank was a bomb
bay-mounted unit from a Boeing B-29 Superfortress. The cockpit was from a Waco
CG-15 military glider and the tail rotor from a Sikorsky H-19 Chickasaw was used
for yaw control.

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, who commissioned the development of the XH-17 Flying Crane research
vehicle. In 1948, the XH-17 began to take shape. The giant helicopter was tested
in Culver City, California over a three-year period beginning in 1952. The XH-17
flew in 1953 at a gross weight in excess of 50,000 pounds (23,000 kg). It still
holds the record for flying with the world's largest rotor system. Only one unit
was built, since the aircraft was too cumbersome and inefficient to warrant
further development.

The propulsion system was unusual. Two General Electric J35 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 tip jets where fuel
was injected. In flight, the main rotor spun at a sedate 88 revolutions per
minute, less than half the speed of typical helicopter rotors. Since the rotor
was driven at the tips rather than the hub, little torque compensation was
required, mostly due to friction in the main rotor bearing. 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 104,000 pounds (47,000 kg).
Though a wooden mockup of the design was made, the program was canceled 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 (12,956 kg)
Useful load: 10,284 lb (4,665 kg)
Loaded weight: 31,270 lb (14,184 kg)
Max. takeoff weight: 43,500 lb (19,731 kg)
Powerplant: 2 × General Electric 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 (3,995 m)
Rate of climb: 1650 ft/min (8.4 m/s)
Disc loading: 2.34 lb/ft² (11.5 kg/m²)



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