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.

H-25/HUP Retriever
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]

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.[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]

Operational history
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 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]

Variants
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.

Operators
 Canada
 France
 United States

Surviving aircraft
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]

Canada
On display
UH-25B (HUP-2)
  • 128529 – Shearwater Aviation Museum in Shearwater, Nova Scotia.[20] This aircraft has been restored to the appearance of 51-16621, the first Royal Canadian Navy HUP-3.[14]
UH-25C (HUP-3)

Netherlands
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 Kingdom
On display
UH-25C (HUP-3)

United States
On display
H-25A Army Mule
HUP-1
UH-25B (HUP-2)
UH-25C (HUP-3)
HUP-3 Retriever on display at the Air Zoo
Under restoration or in storage
UH-25C (HUP-3)

Specifications (HUP-2)

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

See also

Related development

Aircraft of comparable role, configuration, and era

References
Notes
  1. Swanborough and Bowers 1976, p.461.
  2. "HUP-1 Retriever/H-25 Army Mule Helicopter". boeing.com. Boeing. Retrieved 1 November 2018.
  3. Baugher, Joe (24 August 2018). "US Navy and US Marine Corps BuNos, Third Series ((30147 to 39998))". joebaugher.com. Retrieved 1 November 2018.
  4. Devine, Vinny (10 April 2013). "S-53 (U.S.Navy (XHJS-1)". Sikorsky Product History. Igor Sikorsky Historical Archives. Retrieved 1 November 2018.
  5. 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. Baugher, Joe (26 July 2018). "US Navy and US Marine Corps BuNos, Third Series (120341 to 126256)". joebaugher.com. Retrieved 31 October 2018.
  10. Walker, R.W.R. "Royal Canadian Navy – HUP detailed list". Canadian Military Aircraft Serial Numbers. Retrieved 31 October 2018.
  11. Baugher, Joe (2 October 2018). "US Navy and US Marine Corps BuNos, Third Series (145062 to 150138)". joebaugher.com. Retrieved 31 October 2018.
  12. 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. "Piasecki HUP-3". www.shearwateraviationmuseum.ns.ca. Shearwater Aviation Museum. Retrieved 1 November 2018.
  15. Allnutt, Richard Mallory (25 December 2009). "Piasecki crash claims three lives". Aircraft Illustrated. Stamford, Lincolnshire, UK: Key Publishing Ltd. ISSN 0002-2675.
  16. "NTSB Aviation Accident Final Report WPR10LA048". National Transportation Safety Board. Retrieved 5 November 2018.
  17. Harding 1990, pp. 197–198.
  18. "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. 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. 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. https://www.pacificbattleship.com/visit-us/special-exhibits
  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/147610." aerialvisuals.ca Retrieved: 5 May 2016.
  41. Bridgman 1956, p. 345.
  42. Lednicer, David. "The Incomplete Guide to Airfoil Usage". m-selig.ae.illinois.edu. Retrieved 16 April 2019.
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..
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