This tandem rotor
design was evolved by Piasecki Helicopter Corp. to meet a Bureau of
Aeronautics requirement, issued in 1945, for a utility helicopter to be
based aboard aircraft carriers and other large warships of the US Navy
for search and rescue, plane guard, and general transportation duties.
The proposed aircraft was given the works designation PV-14 and two
XHJP-1 prototypes (37976 and '77) were completed for US navy
In 1948 work began on thirty-two PV-18's, or HUP-1 Retrievers, as the
production version was known. They differed little from the original
XHJP-1, the major apparent change being the addition of inward sloping
endplate fins to the horizontal stabilizers below the rear rotor head.
Both sets of three-bladed rotors could be folded for shipboard stowage
and the HUP-1, powered by a single 525hp Continental R-975-34 piston
engine, could accommodate four/five passengers or three casualty
litters in addition to the two-man crew.
Successful tests with a Sperry autopilot in the XHJP-1 enabled the next
model, the HUP-2 , to be built without tail surfaces and the more
powerful Continental R-975-42 was installed in this and all subsequent
Another feature of the Retriever was a large rectangular rescue hatch
offset to starboard in the floor of the front fuselage, through which a
winch inside the cabin could lift weights of up to 400 lbs. at a time.
One-hundred and sixty-five HUP-2's were built for the US Navy; fifteen
were supplied to the France's Aeronavale, and the US Navy also operated
about a dozen HUP-2S submarine hunting aircraft with dunking sonar
equipment. Another HUP-2 was given a sealed, watertight hull and
outrigged twin floats for waterborne tests. US Navy units, which
included HU-1 and HU-2, began to receive the Retriever in February
In 1951, the US Air Force, on behalf of the US Army, ordered a version
of the HUP-2 with a reinforced cabin floor and hydraulically boosted
controls, for general support and evacuation work. Seventy of these
were delivered as H-25A Army Mules from 1953, as were fifty similar
Naval HUP-3's (including three for the Royal Canadian Navy) for
ambulance and light cargo duties. Production of the last aircraft was
completed in July 1954.
A proposal to boost the speed, range, and payload of all H-25/HUP
aircraft still in service by refitting them with 700hp Wright R-1300-3
engines did not take place, and by the time the new tri-service
designation system was introduced in July 1962 only the HUP-2 and HUP-3
remained in service; these became the UH-25B and UH-25C respectively.
Engines: 1 * 550 hp Continental R-975-42
Speed: Max: 170 km/h
Range: Max 550 km
Weight: Empty: 1780 kg -- Max: 2770
Rotor Span: 10.67 m
Length: 17 m
Height: 3.80 m
Disc Area: 179 m2