Boeing Vertol XCH-62

The Boeing Vertol XCH-62 (Model 301) was a triple-turbine, heavy-lift helicopter project designed for the United States Army by Boeing Vertol. Approved in 1971, only one aircraft was built before it was canceled in 1974. An attempt by NASA to resurrect the program was aborted in 1983.

XCH-62 HLH
Role Heavy-lift helicopter
Manufacturer Boeing Vertol
Status Program terminated
Primary user United States Army
Number built 1 (never completed)

Development

While the CH-47 Chinook is a large helicopter by American standards, its payload of 28,000 lb is dwarfed by the huge Soviet-Russian heavy-lift helicopters such as the Mil Mi-26 (44,000 lb) and the experimental Mil Mi-12 (55,000–88,000 lb), and for a long time Boeing and the US military had an urge to match or top the Mil heavy lifters.[1] In the late 1960s, Boeing came up with designs for machines with broad similarities to the Sea Knight and Chinook, but about twice the size of the Chinook in terms of linear dimensions. Proposed machines included the "Model 227" transport and the "Model 237" flying crane.[1]

The U.S. Department of Defense (DoD) issued a request for proposal (RFP) for a Heavy Lift Helicopter (HLH) in November 1970. On May 7, 1971, the DoD announced the selection of Boeing Vertol to perform the first phase of HLH development.[2] Following award of an Army contract for an HLH prototype in 1973, Boeing did move forward on building an oversized flying crane machine, the "XCH-62". The XCH-62 prototype was in an advanced state of assembly in 1975, being readied for a planned initial flight in 1976.[3] The XT701 engine had passed its 30-hour Prototype Preliminary Flight Rating Test (PPFRT) on March 12, 1975, and then passed a 60-hour Safety Demonstration Test (SDT) on August 4.[4] Failures in the spiral bevel gearing of the main transmission were experienced in tests because the method of analysis employed had not considered the effect of rim bending. Consequently, new gears with strengthened rims were designed and fabricated. For a more accurate prediction of the load capacity of the gears, an extensive Finite Element Method (FEM) system was developed. The U.S. Army's XCH-62 HLH aft rotor transmission was finally successfully tested at full design torque and speed, but the US Congress cut funding for the program in August 1975.[5] The designers of the Mil Mi-26 avoided similar problems by using a split-torque design in the main rotor transmission.[6]

The incomplete XCH-62 prototype (73-22012) was to be pulled out of storage in the mid-1980s when the Army, the US National Aeronautics & Space Administration (NASA), and the Defense Advanced Research Projects Agency (DARPA) collaborated on a scheme to finish the XCH-62 for experimental flights. However, Congress declined funding, and the craft remained incomplete.[1] The prototype was moved from a warehouse storage site in Philadelphia, Pennsylvania, floated by barge to Panama City, Florida,[7] and then lifted by a Chinook CH-47D helicopter to the US Army Aviation Museum at Fort Rucker, Alabama on December 8, 1987.[8] The XCH-62 prototype, the largest helicopter ever built in the western countries, was displayed at the US Army Aviation Museum until it was later scrapped in 2005.[9] In 2008, several parts were sent to the Helicopter Museum at Weston-super-Mare (United Kingdom), to be exhibited there.[10]

Design

Rotor diameter was to be 28 meters (92 ft), fuselage length 27.2 meters (89 feet 3 inches), and footprint length 49.5 meters (162 feet 3 inches). Its widely spaced landing gear would allow it to straddle heavy cargoes such as armored vehicles, and still carry twelve troops in its slender fuselage. Boeing also considered selling a commercial version, the "Model 301".[1] The helicopter was powered by three Allison XT701-700 turboshafts, each rated at 8,079 shp, which fed into a combining gearbox capable of absorbing 17,700 shp.[11]

Specifications (XCH-62A)

Data from America's heavy lift helicopter[12]

General characteristics

  • Crew: 5 (pilot, copilot, flight engineer, load controlling crewman, and crew chief)[13]
  • Capacity: 12 troops[14]
  • Length: 87 ft 3 in (26.59 m) (overall fuselage length)
  • Height: 32 ft 3 in (9.83 m) (to top of pylon)
  • Empty weight: 59,580 lb (27,025 kg)
  • Gross weight: 118,000 lb (53,524 kg)
  • Powerplant: 3 × Allison T701-AD-700 turboshaft, 8,080 hp (6,030 kW) each
  • Main rotor diameter: 2× 92 ft 0 in (28.04 m)
  • Main rotor area: 13,260 sq ft (1,232 m2)

Performance

  • Maximum speed: 145 kn (167 mph, 269 km/h) with external load
  • Combat range: 150 nmi (170 mi, 280 km)
  • Ferry range: 1,500 nmi (1,700 mi, 2,800 km)
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See also

Related development

Aircraft of comparable role, configuration and era

Related lists

  • List of helicopters

References

Citations
  1. Greg Goebel's Vectorsite Archived August 7, 2007, at the Wayback Machine
  2. Woodley, David R.; Castle, William S. (October 16–18, 1973). Heavy lift helicopter main engines. National Aerospace Engineering and Manufacturing Meeting. Los Angeles, California, U.S.A.: Society of Automotive Engineers (SAE) (published February 1973). doi:10.4271/730920. ISSN 0148-7191.
  3. "Army revises HLH program, sets competitive prototype tests". R&D News. Army Research and Development. Vol. 16 no. 2. March–April 1975. pp. 4–5. hdl:2027/osu.32435062846985. ISSN 0004-2560.
  4. Stinger, D.H.; Redmond, W.A. (August 7–10, 1978). Advanced gas turbine for marine propulsion model 570-K. SAE West Coast Meeting, Town & Country. San Diego, California, U.S.A.: Society of Automotive Engineers (SAE) (published February 1978). doi:10.4271/780702. ISSN 0148-7191.
  5. XCH-62 page on Globalsecurity.org
  6. Smirnov, G. "Multiple-Power-Path Nonplanetary Main Gearbox of the Mi-26 Heavy-Lift Transport Helicopter", Vertiflite March/April 1990, pp. 20-23
  7. "From drawing board to museum". The nation. Orlando Sentinel. December 9, 1987. p. A-10. ISSN 0744-6055 – via Newspapers.com.
  8. "Copter carry". National dateline. Pensacola News Journal. December 9, 1987. p. 4A. OCLC 54453673 – via Newspapers.com.
  9. "XCH-62 destruction pictures cause a stir". Aero-News Network. November 20, 2005. Retrieved August 9, 2020.
  10. "Arrival of landing gear from Boeing Vertol XCH-62 (HLH)". Friends of The Helicopter Museum. Retrieved August 9, 2020.
  11. Taylor, John W.R. Jane's All The World's Aircraft 1974-75, Jane's All The World's Aircraft Publishing Co. Ltd.
  12. Wilson Flight International 13 July 1972, p.47.
  13. "H.L.H. 1975 flight test projected: Component technology program meeting development goal". Army Research and Development. Vol. 15 no. 1. January–February 1974. pp. 10–11. hdl:2027/msu.31293012265199. ISSN 0004-2560.
  14. US Senate 1974, p. 2709.

Bibliography

The initial version of this article was based on a public domain article from Greg Goebel's Vectorsite.

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