Piasecki HUP Retriever


The Piasecki HUP Retriever/H-25 Army Mule was a compact single radial engine, twin overlapping tandem rotor utility helicopter developed by the Piasecki Helicopter Corporation of Morton, Pennsylvania. Designed to a United States Navy specification, the helicopter was produced from 1949 to 1954, and was also used by the United States Army and foreign navies. The HUP/H-25 was the first helicopter to perform a loop and to be produced with an autopilot.

Design and development

The design was a product of a competition by the U.S. Navy in 1945 for a compact utility/rescue helicopter to operate from ships including aircraft carriers, battleships, and cruisers. Either 2 or 3 prototypes—designated PV-14 by the factory and XHJP-1 by the Navy—were built and subjected to a side-by-side flight evaluation against the 3 prototypes of the Sikorsky XHJS-1; however, the XHJS was fundamentally a scaled-up version of the Sikorsky H-5, and the increased weight and size magnified the design's problems with maintaining proper weight and balance under varying loading conditions. The Piasecki won the competition, and with the introduction of the aircraft configuration letter "U" for Utility in the 1950s, the aircraft was ordered for production as the HUP-1.
The design featured two three-bladed, rotors in tandem in which blades could be folded for storage; the relatively small rotor diameter allowed the aircraft to use aircraft carrier elevators with its blades fully extended. The tandem overlapping rotor configuration was a development by Piasecki and was used in future helicopter designs by the company and successors including the H-21, HRB-1/CH-46, and CH-47. The original HUP-1 was powered by a single Continental R-975-34 radial engine, with a take-off rating of, while later versions used the uprated R-975-42 or R-975-46A with. To aid search and rescue operations, the aircraft was equipped with an overhead winch capable of lifting 400 lb, which could lower a rescue sling through an electrically-operated door available after the copilot's seat was folded forward.
During a flight demonstration of its capability to withstand high g-force, the type became the first helicopter to perform a loop, albeit unintentionally.

Operational history

The aircraft first entered service in February 1949 with the delivery of the first of 32 HUP-1 aircraft to the US Navy. The improved HUP-2 was soon introduced with a more powerful engine, deletion of the inward-canted horizontal stabilizer endplate fins, and various minor changes in equipment; a sub-variant equipped with dunking sonar for anti-submarine warfare was given the designation HUP-2S. The HUP-2 was the first production helicopter equipped with an autopilot. The US Navy also tested a system called Raydist that allowed an unmanned HUP-2 to be directed from a ground station and by radio ordered to hover within five feet of the desired point. Edo tested a HUP-2 with a fiberglass hull and outrigger floats for amphibious operations.
An upgraded version of the HUP-2 was built for the US Army and designated as the H-25A Army Mule, but most were quickly withdrawn from Army service and converted for naval use under the designation HUP-3.
In 1954, the Royal Canadian Navy received 3 former US Army H-25A aircraft, which were modified and redesignated on delivery to conform to US Navy HUP-3 standards. The aircraft were used aboard HMCS Labrador for SAR and varied utility duties, and were later used to support construction at Distant Early Warning Line radar sites. The helicopters were subsequently posted to NAF Patricia Bay and naval air station HMCS Shearwater; after the last 2 were struck off strength on 18 January 1964, 1 aircraft was donated to a technical school and the other 2 were sold as surplus.
The US Army H-25 designation was adopted by the US Navy in 1962 on introduction of the 1962 United States Tri-Service aircraft designation system. The final units were withdrawn from US service in 1964. It also served with French Naval Aviation from 1953 to 1965.
A total of 339 aircraft were delivered during the 6-year production run. A large number of surplus US Navy aircraft later appeared on the US civil registry, and at least 7 were transferred to the French Navy.
On 7 November 2009, former US Navy HUP-1, BuNo 124925, civil registration number N183YP, collided with high-voltage power lines in Adelanto, California; the subsequent crash and post-crash fire killed all 3 occupants and substantially damaged the aircraft. Operated in association with Classic Rotors, the accident aircraft was the only airworthy example in the world. The National Transportation Safety Board attributed the crash to "The pilot’s failure to maintain clearance from powerlines during en route flight."

Variants

;XHJP-1
;HUP-1
;HUP-2
;HUP-2S
;HUP-3
;H-25A Army Mule
;UH-25B
;UH-25C

Operators

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; :
For surviving aircraft, hyphenated numbers are original US Army Serial Numbers; six-digit numbers are original US Navy Bureau of Aeronautics Bureau Numbers. All 50 H-25A/HUP-3 aircraft transferred from the US Army to the US Navy were given new bureau numbers; 3 aircraft transferred to the Royal Canadian Navy were redesignated, but retained their original US Army serial numbers.

Canada

;On display
;;UH-25B
;;UH-25C
;On display
;;UH-25B
;On display
;;UH-25C
;On display
;;H-25A Army Mule
;;HUP-1
;;UH-25B
;;UH-25C
;Under restoration or in storage
;;UH-25C