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Piasecki H-25

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H-25/HUP Retriever
US Army H-25 Army Mule
Type Utility helicopter
Manufacturer Piasecki Helicopter
Maiden flight March 1948
Introduced 1949
Retired 1964
Primary users United States Navy
United States Army

The Piasecki H-25 Army Mule/HUP Retriever was a compact single radial engine, twin overlapping tandem rotor utility helicopter developed by the Piasecki Helicopter Corporation of Morton, Pennsylvania during the late 1940s and produced during the early 1950s. The company changed its name in the 1956 to Vertol Aircraft Corporation and subsequently was bought by Boeing Aircraft Company in 1960, and became Boeing-Vertol.


The design was a product of a competition by the U.S. Navy in 1945 for a compact utility/rescue helicopter to operate from Navy ships including aircraft carriers, battleships, and cruisers. The prototype was designated by the Navy as the XHJP-1, and first flew in March 1948. It was selected by the Navy for production, as the HUP-1 in a side-by-side flight evaluation against the Sikorsky XHJS-1. It entered service with the Navy and USMC from 1949.

Versions of the HUP built for the U.S. Army were designated H-25 Army Mule. 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 design featured two three bladed 35 foot diameter rotors in tandem in which blades could be folded for storage in ships’ hangars. The HUPs were powered by a single Continental R975-46 radial engine, with a take-off rating of 550 hp. To provide rescue without crew assistance, an electrically operated door, available after folding the copilot’s seat forward, opened through which a rescue sling could be lowered from an overhead winch.

The HUP was produced for the Navy in four versions: HUP-1, -2, -3, and -4. The HUP-2 was the first production helicopter equipped with an auto-pilot. In addition to those delivered to the U.S. Navy and Army the HUP/H-25 helicopter was also delivered to the Canadian and French Navies. A total of 339 aircraft were delivered over the 20 year life of the aircraft.

The US Army H-25 designation was adopted by the other services in 1962. The final units were withdrawn from US service in 1964. It also served with the French Navy from 1953 to 1965.

Military Operators



General characteristics

  • Crew: 2
  • Passengers: 4
  • Length Fuselage: 32 ft (9.8 m)
  • Wingspan (rotor): 35 ft (10.7 m )
  • Height: 12 ft 6 in (3.8 m)
  • Empty: 4,100 lb (1,864 kg)
  • Useful Load: 1,650 lb (341 kg)
  • Powerplant: one, Continental R975-42 radial engine, 550 hp, (737 kW)


  • Maximum speed: 108 mph (174 km/h)
  • Range: 360 statute miles (580 km)
  • Service ceiling: 10,200 ft (3,110 m)
  • Rate of climb: m/min ( ft/min)




General characteristics

  • Crew: two pilots
  • Capacity: 4 passengers
  • Length: 56 ft 11 in (17.35 m)
  • Main rotor diameter: 35 ft 0 in (10.67 m)
  • Height: 12 ft 6 in (3.81 m)
  • Main rotor area: 1,924 ft² (179 m²)
  • Empty: 3,928 lb (1,782 kg)
  • Loaded: 5,750 lb (2,608 kg)
  • Maximum takeoff: 6,100 lb (2,767 kg)
  • Powerplant:Continental R-975-46A radial, 550 hp (410 kW)


  • Maximum speed: 105 mph (169 km/h)
  • Range: 340 miles (547 km)
  • Service ceiling: 10,000 ft (3,048 m)
  • Rate of climb: 100 ft/min (305 m/min)
  • Main rotor loading: 3 lb/ft² (15 kg/m²)
  • Power/mass: 0.09 hp/lb (0.16 kW/kg)

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Designation sequence