Piasecki PV-18 / H-25 : Retriever / 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.

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.

HUP Helicopter

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.

Did you Know? : while most helicopters have their pilot/commander situated on the right in two-seat aircraft, which is the reverse of fixed-wing planes with side-by-side seating, where the aircraft commander is in the left seat. However, on the HUP-2, the command pilot is situated on the left side of the aircraft because the rescue hoist that is dropped down to recover rescues is located on the right forward side, and drops down through the the co-pilot's station. The co-pilot's seat folds down and slides back out of the way, so that the rescue hoist hook can drop down through the hatch on the right forward bottom of the fuselage.

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

See Also: Preserved BuNo 128596 on our Database

Contribution : Steve Jones & Ron Lewis

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