Piasecki HUP Retriever

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.[2] Either 2[1][3] or 3[4][5] 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.[4] The Piasecki won the competition,[4] and with the introduction of the aircraft configuration letter "U" for Utility in the 1950s,[6] the aircraft was ordered for production as the HUP-1.[1]

The design featured two three-bladed, 35-foot-diameter (11 m) 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.[2] 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 525 hp (391 kW), while later versions used the uprated R-975-42 or R-975-46A with 550 hp (410 kW).[1] To aid search and rescue (SAR) operations, the aircraft was equipped with an overhead winch capable of lifting 400 lb (181 kg), which could lower a rescue sling through an electrically-operated door available after the copilot's seat was folded forward.[2]

During a flight demonstration of its capability to withstand high g-force, the type became the first helicopter to perform a loop, albeit unintentionally.[2]

H-25A Army Mule preserved in the US Army Aviation Museum, Alabama

The aircraft first entered service in February 1949 with the delivery of the first of 32 HUP-1 aircraft to the US Navy.[1] The improved HUP-2 (Piasecki designation PV-18) 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.[1][2] The HUP-2 was the first production helicopter equipped with an autopilot.[2] 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.[7] Edo tested a HUP-2 with a fiberglass hull and outrigger floats for amphibious operations.[8]

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.[1][2][9][10][11]

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.[10][12][13][14] 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.[10][14] 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.[10][14]

The US Army H-25 designation was adopted by the US Navy in 1962[1] 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 (Aeronavale) from 1953 to 1965.[2]

A total of 339 aircraft were delivered during the 6-year production run.[2] 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.[9]

On 7 November 2009, former US Navy HUP-1, BuNo 124925,[15] civil registration number N183YP,[9] 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.[16] Operated in association with Classic Rotors, the accident aircraft was the only airworthy example in the world.[15] The National Transportation Safety Board attributed the crash to "The pilot’s failure to maintain clearance from powerlines during en route flight."[16]

XHJP-1

Prototype, powered by a 525 hp (391 kW) Continental R-975-34 piston engine, equipped with large sloping endplate fins on the horizontal stabilizers. Piasecki-Vertol designation was PV-14. 2[1][3] or 3[4][5] produced.

HUP-1

Utility transport and search and rescue helicopter for the US Navy, largely similar to XHJP-1, Piasecki designation was PV-18. 32 built.[1][2]

A U.S. Navy HUP plane guard doing its work in 1953

HUP-2

Improved version, 550 hp (410 kW) Continental R-975-42 piston engine, horizontal stabilizer endplate fins eliminated.[1][2] 165 built for the US Navy,[1] 15 for French Aeronavale. Redesignated UH-25B in 1962.

HUP-2S

Anti-submarine warfare version of HUP-2 fitted with dunking sonar. 12 built.[2]

HUP-3

Naval utility conversion of H-25A aircraft transferred from US Army: 50 to US Navy,[11] 3 to Royal Canadian Navy.[10][12] Remaining US Navy aircraft redesignated UH-25C in 1962.

H-25A Army Mule

Utility transport helicopter for US Army, similar to HUP-2 but powered by a 550 hp (410 kW) Continental R-975-46A piston engine, and fitted with large doors, power-boosted controls, and strengthened floors.[1][2] 70 were delivered from 1953, but they were unsuitable for front-line use,[17] with 53 transferred to the Royal Canadian and US Navies in 1954–1955,[10][12] and the remaining helicopters used for training, being withdrawn from army service by 1958.[17]

UH-25B

HUP-2 redesignated after 1962.

UH-25C

HUP-3 redesignated after 1962.

 Canada

• Royal Canadian Navy [18]

 France

• French Navy [18][19]

 United States

• United States Army [18]
• United States Navy [18]

Royal Canadian Navy HUP-3 51-16621 at the Canadian Museum of Flight; this aircraft was later traded to Classic Rotors.[14]

For surviving aircraft, hyphenated numbers are original US Army Serial Numbers; six-digit numbers are original US Navy Bureau of Aeronautics (BuAer) Bureau Numbers (BuNo). 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.[10][12]

United States

On display

H-25A Army Mule

• 51-16616 – United States Army Aviation Museum in Fort Rucker, Alabama.[25]

HUP-1

• 124915 – USS Hornet Museum in Alameda, California.[26]

UH-25B (HUP-2)

• 128479 – American Helicopter Museum in West Chester, Pennsylvania.[27]
• 128517 – Wings of Freedom Aviation Museum in Horsham, Pennsylvania.[28]
• 128519 – Intrepid Sea, Air & Space Museum in New York City, New York.[29]
• 128596 – Flying Leatherneck Aviation Museum in San Diego, California.[30]
• 130059 – USS Midway Museum in San Diego, California.[31]
• 130082 – on the deck of the USS Iowa Museum in San Pedro, California.[32][33]

UH-25C (HUP-3)

HUP-3 Retriever on display at the Air Zoo

• 147595 – Pima Air & Space Museum in Tucson, Arizona.[34]
• 147600 – Air Zoo in Kalamazoo, Michigan.[35]
• 147607 – National Naval Aviation Museum in Pensacola, Florida.[36]
• 147628 – Mid-America Air Museum in Liberal, Kansas.[37]
• 51-16621 – Classic Rotors in Ramona, California.[38] As of December 2019, this is the only Piasecki Helicopter-manufactured aircraft with valid FAA aircraft registration.[39] This former Royal Canadian Navy aircraft is reportedly the last HUP/H-25 capable of being restored to airworthy condition; it was exchanged in 2000 by the Canadian Museum of Flight for unflyable HUP-2 128529, which was subsequently traded again in 2002 to the Shearwater Aviation Museum and repainted as 51-16621.[14][20]

Under restoration or in storage

UH-25C (HUP-3)

• 147610 – Yanks Air Museum in Chino, California, in storage.[40]

Data from Jane's All The World's Aircraft 1956–57[41]

General characteristics

• Crew: two
• Capacity: four passengers
• Length: 56 ft 11 in (17.35 m)
• Height: 13 ft 2 in (4.01 m)
• Empty weight: 4,132 lb (1,874 kg)
• Gross weight: 5,750 lb (2,608 kg)
• Max takeoff weight: 6,100 lb (2,767 kg)
• Powerplant: 1 × Continental R-975-46A 9-cylinder air-cooled radial piston engine, 550 hp (410 kW)
• Main rotor diameter: 2× 35 ft 0 in (10.67 m)
• Main rotor area: 1,924.5 sq ft (178.79 m²)
  
• Blade section: NACA 0012[42]

Performance

• Maximum speed: 105 mph (169 km/h, 91 kn)
• Cruise speed: 80 mph (130 km/h, 70 kn)
• Range: 340 mi (550 km, 300 nmi)
• Service ceiling: 10,000 ft (3,000 m)
• Rate of climb: 1,000 ft/min (5.1 m/s)
• Disk loading: 3 lb/sq ft (15 kg/m²)

Related development

• Piasecki H-21
• CH-46 Sea Knight

Aircraft of comparable role, configuration and era

• Bell HSL
• Bristol Belvedere
• Harbin Z-5
• Mil Mi-4
• Sikorsky H-19 Chickasaw

Notes

Bibliography

• Bridgman, Leonard. Jane's All The World's Aircraft 1956–57. New York: The McGraw-Hill Book Company, 1956.
• Harding, Stephen. U.S. Army Aircraft Since 1947. Shrewsbury, UK:Airlife, 1990. ISBN 1-85310-102-8.
• Swanborough, Gordon; Bowers, Peter M. (1976). United States Navy Aircraft since 1911 (2nd ed.). Annapolis, Maryland: Naval Institute Press. ISBN 0-87021-968-5.CS1 maint: ref=harv (link).

Wikimedia Commons has media related to Piasecki HUP Retriever.

• H-25 US Army Aviation history fact sheet