At the
request of the U.S. Army in 1951, the U.S. Air
Force initiated the development of a one-man,
pulsejet-driven helicopter for observation,
liaison and reconnaissance purposes. This
unarmed helicopter had to be collapsible,
capable of aerial delivery to troops in rugged
terrain, and assembled quickly with simple
tools. The American Helicopter Division
of the Fairchild Engine and Airplane Corp.
won the design competition and produced the
rugged and uncomplicated Model XA-8. Under the military
designation XH-26, the aircraft first flew in January
1952.
Constructed of aluminum, except for the aft fuselage
which was laminated fiberglass, the XH-26 did not use
any gears. Rather than having an internal engine like
other helicopters, the Jet Jeep was powered by two
6.75-inch pulsejets on the end of each rotor blade tip.
Designed by American Helicopter, each of these pulsejets
weighed 16 pounds and produced 35 pounds of thrust.
Started with an internal compressed air system, the
engines did not have to be warmed up, and the XH-26
could take off in just 30 seconds. Furthermore, since
the pulsejets produced no torque like engines on other
helicopters, the tiny, belt-driven tail rotor was not
used for anti-torque but to improve directional control.
American Helicopter chose the
name "Jet Jeep" because the XH-26 would be used like a
Jeep in the air, and it could use the same fuel as the
Jeep. When collapsed, its 5-foot-by-5-foot-by-14-foot
container fit on a trailer towed by the one-quarter ton
Jeep. If stripped for air drop, the Jet Jeep weighed
less than 300 pounds, and it could be assembled by two
men in just 20 minutes.
The
Army and USAF evaluated five prototype Jet Jeeps, and
they proved to be a rugged aircraft with a top speed of
80 mph and a ceiling of 7,000 feet. However, the
pulsejets produced so much noise that the Army found the
aircraft unsuitable, and cost considerations forced the
cancellation of the program.
TECHNICAL NOTES:
Engines:
Two American Helicopter AJ-7.5-1 pulsejets
Fuel capacity:
50 gallons
Range: 135
miles
Endurance:
Approx. 2 hours
Source: National
Museum of the United States Air Force |
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