Piasecki PV-18
H-25 series
Retriever / Mule / Mule / HUP
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.
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The proposed aircraft was given the works designation PV-14 and two
XHJP-1 prototypes (37976 and '77) were completed for US navy evaluation.
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
accomodate 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
production models.
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 recieve the Retriever in February 1949.
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.
HUP-3
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
Contribution : Steve Jones
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