Great image here for the scale of the ‘flying crane’. sourceOK,
it looked ugly and strange but it worked – kind of. Made from parts
from various WWII warbirds the Hughes XH-17 “Flying Crane” was by far
,the most impressive of all rotor-craft in the early 1950s was a strange
monster designated XH-17. This was planned and taken through the design
process by Kellett, but hardware trials were transferred to Hughes
Aircraft at Culver City. Already the aircraft firm of billionaire Howard
Hughes had a reputation for being quite undeterred by the most
formidable development problems, and certainly the XH-17 made sense on
paper. In any case, it was part-funded by the USAF. It was a flying
crane, the specialized category pioneered by the German Fa 284 and
intended to lift cargo weighing up to 27,000 lb more than ten times as
much as any other rotorcraft of its day. To do so it had a radically new
form of lift power.
Howard
Hughes (second from left) standing under the blade of the XH-17, Flying
Crane with L-R: Rea Hopper, Director of the Aeronautical Division,
Hughes Aircraft Company; Hughes; Clyde Jones, Director of Engineering,
Hughes Tool Company Aeronautical Division; Warren Reed, Assistant;
Colonel Carl E. Jackson, Air Research and Development Headquarters;
Gale. J. Moore, Pilot; Chal Bowen?, Flight Engineer/Co-Pilot;
unidentified pilot. source
Scroll down for video
The
prototype was finished in 1949, ahead of schedule and one of the
reasons being that it was made from parts poached from WWII warbirds.
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-15and the tail rotor from a Sikorsky H-19 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.
Engines: two GE J35 turbojets Weight fully loaded: 52,000 lb Cruising speed: 60 mph Range: 40 miles Number of seats: 2. sourceThe
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 rotors spun
at a sedate 88 rpm. Since the rotor was driven at the tips rather than
the hub, little torque compensation was required.
The XH-17 employed an unusual gas-turbine and rotor-tip combustion combination to provide power to spin the gigantic rotors.
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. Finally, having received the Air Force serial
50-1842, the XH-17 was first flown by Gale Moore at Culver City on 23
October, 1952. That flight, however, had to be cut short after the XH-17
had been airborne for barely a minute as directional control forces
were excessive. While correction of this deficiency could be made
quickly, difficulties uncovered later in the trials required more time.
In particular, high vibratory stresses in the main rotor blades were
difficult to correct and the XH-17 was repeatedly grounded while
modifications were incorporated. The off and on test programme ended
when the rotor blades reached their design life in December 1955
writes aviastar.org
Hughes experimental helicopters XH-17 at the front XH-28 mock up at the rear. sourceBy
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.
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. source
The giant rotors promised a huge lifting capacity, so they were attached to stilt-like legs and a box-like fuselage. source
Entry to the cockpit required a pair of tall ladders attached to the forward landing gear legs. source
The XH-17 employed an unusual gas-turbine and rotor-tip combustion combination to provide power to spin the gigantic rotors.
