McDonnell HRH

The McDonnell HRH, company designation Model 78, was a 1950s transport helicopter proposal for the United States Marine Corps (USMC) by the McDonnell Corporation, designed to operate from Commencement Bay-class escort carriers.

XHRH
Role Cargo helicopter
National origin United States
Manufacturer McDonnell Aircraft
Status Cancelled; mockup phase only
Primary user United States Marine Corps

Development

The HRH was developed in March 1951 in response to a USMC requirement for a 30 seat assault transport helicopter. The HRH's competitor was the Sikorsky HR2S. Three prototypes (BuNos 133736/13338) were ordered, and although the Bureau of Aeronautics expected the XHRH-1 to fly in December 1955, the design was cancelled in 1953 in favor in of the Mojave, the first prototype remaining un-completed.[1][2]

Specifications (Model 78 / XHRH-1 estimated)

Data from McDonnell Douglas aircraft since 1920. Volume II.[2]

General characteristics

  • Crew: 2
  • Capacity: 30 troops or 24 stretchers or 2x Jeeps
  • Length: 65 ft 11 in (20.09 m) 16.33 m (53.6 ft) folded
  • Wingspan: 45 ft (14 m) foldable for carrier stowage
  • Height: 16 ft 8 in (5.09 m)
  • Wing area: 332 sq ft (30.8 m2)
  • Empty weight: 19,169 lb (8,695 kg)
  • Gross weight: 30,412 lb (13,795 kg)
  • Max takeoff weight: 36,000 lb (16,329 kg)
  • Powerplant: 2 × Allison XT56-A-4 turboprop / gas generators, 3,507 shp (2,615 kW) each
  • Powerplant: 3 × McDonnell 12JP20 cold pressure jets, 1,600 lbf (7.1 kN) thrust each
  • Main rotor diameter: 65 ft (20 m)
  • Main rotor area: 3,320 sq ft (308 m2) 3-bladed with tip-jets
  • Propellers: 3-bladed constant speed fully-feathering propellers

Performance

  • Maximum speed: 276 mph (444 km/h, 240 kn) at sea level
  • Combat range: 116 mi (186 km, 100 nmi) out and return radius
  • Service ceiling: 10,000 ft (3,000 m) hovering ceiling out of ground effect
  • Rate of climb: 2,300 ft/min (12 m/s)

References
  1. Pike, John. "HRH". www.globalsecurity.org. Retrieved 8 November 2018.
  2. Francillon, Rene J. McDonnell Douglas aircraft since 1920. Volume II (2nd ed.). London: Putnam Aeronautical. pp. 412–414. ISBN 0851778283.
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