Piasecki HUP Retriever


The Piasecki HUP Retriever/H-25 Army Mule is 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 be produced with an autopilot and also the first to perform a loop.

H-25/HUP Retriever
HUP-2 from USS FD Roosevelt (CVA-42) in flight 1959.jpg
A U.S. Navy HUP-2 from USS Franklin D. Roosevelt
Role Utility helicopter
Manufacturer Piasecki Helicopter
First flight March 1948
Introduction February 1949[1]
Retired 1958 US Army
January 1964 RCN
1964 USN
1965 French Navy
Primary users United States Navy
United States Army
Royal Canadian Navy
French Navy
Produced 1949–1954[2]
Number built 339[2][disputed ]

Design and developmentEdit

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][disputed ] 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]

Operational historyEdit

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 radio navigation 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 (1.5 m) 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 three 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 search and rescue 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 two were struck off strength on 18 January 1964, one aircraft was donated to a technical school and the other two 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.[citation needed] It also served with French Naval Aviation (Aeronavale) from 1953[citation needed] to 1965.[2]

A total of 339 aircraft were delivered during the 6-year production run.[2][disputed ] A large number of surplus US Navy aircraft later appeared on the US civil registry, and at least seven 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]


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.[disputed ]
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
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][disputed ] 15 for French Aeronavale.[citation needed] Redesignated UH-25B in 1962.
Anti-submarine warfare version of HUP-2 fitted with dunking sonar. 12 built.[2]
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]
HUP-2 redesignated after 1962.
HUP-3 redesignated after 1962.


  United States

Surviving aircraftEdit

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]


On display


  • UH-25B (HUP-2), 130076 – Baris Business Park roadway roundabout in Rotterdam. This aircraft was originally used by the US Navy and was later transferred to the French Navy.[23]

United KingdomEdit

United StatesEdit

On display
H-25A Army Mule
UH-25B (HUP-2)
UH-25C (HUP-3)
HUP-3 Retriever on display at the Air Zoo
Under restoration or in storage
UH-25B (HUP-2)
UH-25C (HUP-3)

Specifications (HUP-2)Edit


Data from Jane's All The World's Aircraft 1956–57.[42]

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[43]


  • 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)
  • Power/mass: 0.09 hp/lb (0.15 kW/kg)

See alsoEdit

Related development

Aircraft of comparable role, configuration, and era


  1. ^ a b c d e f g h i j k l m Swanborough and Bowers 1976, p.461.
  2. ^ a b c d e f g h i j k l m n o "HUP-1 Retriever/H-25 Army Mule Helicopter". boeing.com. Boeing. Retrieved 1 November 2018.
  3. ^ a b Baugher, Joe (24 August 2018). "US Navy and US Marine Corps BuNos, Third Series ((30147 to 39998))". joebaugher.com. Retrieved 1 November 2018.
  4. ^ a b c d Devine, Vinny (10 April 2013). "S-53 (U.S.Navy (XHJS-1)". Sikorsky Product History. Igor Sikorsky Historical Archives. Retrieved 1 November 2018.
  5. ^ a b http://1000aircraftphotos.com/Contributions/WatkinsRay/8891.htm accessdate:26 January 2014
  6. ^ Swanborough and Bowers 1976, pp.8–9.
  7. ^ Hearst Magazines (May 1954). "Radio Waves Hold Helicopter In Fixed Hovering Position". Popular Mechanics. Hearst Magazines. p. 122.
  8. ^ "Picture News: Watertight hull makes helicopter amphibious". Popular Science. Vol. 172, no. 2. February 1958. p. 149.
  9. ^ a b c Baugher, Joe (26 July 2018). "US Navy and US Marine Corps BuNos, Third Series (120341 to 126256)". joebaugher.com. Retrieved 31 October 2018.
  10. ^ a b c d e f g h Walker, R.W.R. "Royal Canadian Navy – HUP detailed list". Canadian Military Aircraft Serial Numbers. Retrieved 31 October 2018.
  11. ^ a b Baugher, Joe (2 October 2018). "US Navy and US Marine Corps BuNos, Third Series (145062 to 150138)". joebaugher.com. Retrieved 31 October 2018.
  12. ^ a b c d Baugher, Joe (2 September 2018). "1951 USAF Serial Numbers". joebaugher.com. Retrieved 31 October 2018.
  13. ^ "Piasecki HUP-3". ingeniumcanada.org. Ingenium Canada - Canada Air and Space Museum. Retrieved 31 October 2018.
  14. ^ a b c d e f "Piasecki HUP-3". www.shearwateraviationmuseum.ns.ca. Shearwater Aviation Museum. Retrieved 1 November 2018.
  15. ^ a b Allnutt, Richard Mallory (25 December 2009). "Piasecki crash claims three lives". Aircraft Illustrated. Stamford, Lincolnshire, UK: Key Publishing Ltd. ISSN 0002-2675.
  16. ^ a b "NTSB Aviation Accident Final Report WPR10LA048". National Transportation Safety Board. Retrieved 5 November 2018.
  17. ^ a b Harding 1990, pp. 197–198.
  18. ^ a b c d "Piasecki H-25 History". Boeing. Archived from the original on 2012-10-29. Retrieved 2013-02-02.
  19. ^ "Piasecki PV-18 (HUP/H-25/UH-25) (Photo)". pictaero.com. Retrieved 2 February 2013.
  20. ^ a b Skaarup, Howard (2009). Canadian Warplanes. Bloomington, Indiana: iUniverse. p. 520. ISBN 978-1-4401-6758-4.
  21. ^ "Piasecki HUP Retriever/51-16623." aerialvisuals.ca Retrieved: 5 May 2016.
  22. ^ Canada Aviation and Space Museum. "Piasecki HUP-3". techno-science.ca. Retrieved 5 May 2016.
  23. ^ "De helikopter" [The helicopter]. www.baris.nl (in Dutch). Baris Groep. 11 November 2013. Retrieved 1 November 2018.
  24. ^ "Piasecki HUP Retriever/622 RCN." aerialvisuals.ca Retrieved: 5 May 2016.
  25. ^ "Piasecki HUP Retriever/51-16616." aerialvisuals.ca Retrieved: 5 May 2016.
  26. ^ "Piasecki HUP Retriever/124915." aerialvisuals.ca Retrieved: 25 April 2017.
  27. ^ "Piasecki HUP Retriever/128479." aerialvisuals.ca Retrieved: 5 May 2016.
  28. ^ "Piasecki HUP-2 "Retriever"". Wings of Freedom Aviation Museum. Retrieved 26 August 2016.
  29. ^ "Piasecki HUP Retriever/128519." aerialvisuals.ca Retrieved: 5 May 2016.
  30. ^ "Piasecki HUP Retriever/128596." aerialvisuals.ca Retrieved: 5 May 2016.
  31. ^ "Piasecki HUP Retriever/130059." aerialvisuals.ca Retrieved: 5 May 2016.
  32. ^ "Piasecki HUP Retriever/130082." Daily Breeze Retrieved: 25 April 2017.
  33. ^ Pacific Battleship Center (2019). "New Exhibits". pacificbattleship.com. Archived from the original on 24 April 2020. Retrieved 20 February 2022.
  34. ^ "Piasecki HUP Retriever/147595." aerialvisuals.ca Retrieved: 5 May 2016.
  35. ^ "Piasecki HUP Retriever/147600". www.aerialvisuals.ca. Retrieved 2016-06-08.
  36. ^ "Piasecki HUP Retriever/147607." aerialvisuals.ca Retrieved: 5 May 2016.
  37. ^ "Piasecki HUP Retriever/147628." aerialvisuals.ca Retrieved: 5 May 2016.
  38. ^ Federal Aviation Administration (1 November 2018). "N-Number Inquiry Results N7089F". Retrieved 1 November 2018.
  39. ^ Federal Aviation Administration (16 December 2019). "Manufacturer Inquiry Results Piasecki". Retrieved 16 December 2019.
  40. ^ "Piasecki HUP Retriever/130053." aerialvisuals.ca Retrieved: 15 July 2021.
  41. ^ "Piasecki HUP Retriever/147610." aerialvisuals.ca Retrieved: 5 May 2016.
  42. ^ Bridgman 1956, p. 345.
  43. ^ Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
  • 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..

External linksEdit

  • H-25 US Army Aviation history fact sheet