Boeing Vertol XCH-62
{{Short description|Cancelled American heavy-lift helicopter}}
{{Infobox aircraft
|name = XCH-62 HLH
|image = File:Boeing XCH-62.jpg{{!}}border
|caption =
|type = Heavy-lift helicopter
|manufacturer = Boeing Vertol
|designer =
|first_flight =
|introduction =
|retired =
|status = Program terminated
|primary_user = United States Army
|more_users =
|produced =
|number_built = 1 (never completed)
|unit cost =
|developed_from =
|variants =
}}
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, one prototype reached 95% completion before it was canceled in 1975. The prototype was scrapped in 2005.
Development
While the CH-47 Chinook is a large helicopter by American standards, its payload of {{convert|28000|lb|kg|abbr=on}} is dwarfed by the huge Soviet-Russian heavy-lift helicopters such as the Mil Mi-26, with {{convert|44000|lb|kg|abbr=on}} payload, and the experimental Mil V-12, with {{convert|55000|to|88000|lb|kg|abbr=on}} payload. For a long time Boeing and the US military had an urge to match or top the Mil heavy lifters. 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.{{cite web |url=http://www.vectorsite.net/avcobra_1.html#m4 |title=Greg Goebel's Vectorsite |archive-date=August 7, 2007 |url-status=usurped |archive-url=https://web.archive.org/web/20070807001809/http://www.vectorsite.net/avcobra_1.html#m4}}
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.{{cite conference |issn=0148-7191 |title=Heavy lift helicopter main engines |date=October 16–18, 1973 |publication-date=February 1973 |given1=David R. |surname1=Woodley |given2=William S. |surname2=Castle |journal=SAE Technical Papers |series=SAE Technical Paper Series |volume=1 |publisher=Society of Automotive Engineers (SAE) |location=Los Angeles, California, U.S.A. |conference=National Aerospace Engineering and Manufacturing Meeting |doi=10.4271/730920}} 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.{{cite magazine |title=Army revises HLH program, sets competitive prototype tests |issn=0004-2560 |magazine=Army Research and Development |hdl=2027/osu.32435062846985 |url=https://hdl.handle.net/2027/osu.32435062846985?urlappend=%3Bseq=6 |pages=4–5 |department=R&D News |publication-date=March–April 1975 |volume=16 |number=2}} 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.{{cite conference |issn=0148-7191 |title=Advanced gas turbine for marine propulsion model 570-K |publication-date=February 1978 |given1=D.H. |surname1=Stinger |given2=W.A. |surname2=Redmond |journal=SAE Technical Papers |series=SAE Technical Paper Series |publisher=Society of Automotive Engineers (SAE) |conference=SAE West Coast Meeting, Town & Country |location=San Diego, California, U.S.A. |date=August 7–10, 1978 |volume=1 |doi=10.4271/780702}} However, the program was officially canceled on August 1. At the time of cancellation, the prototype was at 95% completion, and it needed about three months of final assembly and checkouts before rollout and installation for pre-flight testing.{{R|"BVFinalReport1980"|p=[https://archive.org/details/DTIC_ADA085290/page/n4 3]}}
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.[http://www.globalsecurity.org/military/systems/aircraft/h-62.htm XCH-62 page on Globalsecurity.org] The designers of the Mil Mi-26 avoided similar problems by using a split-torque design in the main rotor transmission.Smirnov, G. "Multiple-Power-Path Nonplanetary Main Gearbox of the Mi-26 Heavy-Lift Transport Helicopter", Vertiflite March/April 1990, pp. 20-23
Subsequent attempts were made to finish the incomplete XCH-62 prototype, which had a serial number of 73-22012. In the mid-1980s, 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, requesting a combined US$71 million in funding through fiscal year 1989.{{cite news |issn=1070-8626 |work=Citizens' Voice |title=Army seeks to test canceled helicopter |url=https://www.newspapers.com/newspage/437894339/ |given=George C. |surname=Wilson |publication-date=December 13, 1984 |location=Washington, D.C., U.S.A. |agency=The Washington Post |via=Newspapers.com}} However, Congress declined funding, and the craft remained incomplete. The prototype was moved from a warehouse storage site in Philadelphia, Pennsylvania, floated by barge to Panama City, Florida,{{cite news |via=Newspapers.com |issn=0744-6055 |work=Orlando Sentinel |title=From drawing board to museum |url=https://www.newspapers.com/clip/41006178/xch-62/ |department=The nation |page=A-10 |publication-date=December 9, 1987}} and then lifted by a CH-47D Chinook helicopter to the US Army Aviation Museum at Fort Rucker, Alabama on December 8, 1987.{{cite news |via=Newspapers.com |oclc=54453673 |work=Pensacola News Journal |title=Copter carry |url=https://www.newspapers.com/clip/41006254/xch-62-pg-2/ |department=National dateline |page=4A |publication-date=December 9, 1987}} 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.{{cite news |title=XCH-62 destruction pictures cause a stir |url=http://www.aero-news.net/index.cfm?do=main.textpost&id=d07b9f97-11df-4fae-be11-93e7f7b4c58f |date=November 20, 2005 |website=Aero-News Network |access-date=August 9, 2020}} In 2008, several parts were sent to the Helicopter Museum at Weston-super-Mare (United Kingdom), to be exhibited there.{{cite web |url=http://www.hmfriends.org.uk/xch-62_hlh.htm |title=Arrival of landing gear from Boeing Vertol XCH-62 (HLH) |website=Friends of The Helicopter Museum |access-date=August 9, 2020}}
Design
The XCH-62 is a tandem rotor helicopter, with four blades on each rotor. Its rotor diameter was to be {{cvt|92|ft}}, fuselage length {{cvt|89|ft|3|in}}, and footprint length {{cvt|162|ft|3|in}}. The maximum width with blades folded was {{cvt|29|ft|10|in}}. The rotor blade had a length was {{cvt|42|ft}}, a chord of {{cvt|40|in}}, and a weight of {{cvt|750|lb}}.{{R|"USSenate1974"|p=[https://hdl.handle.net/2027/umn.31951d03440242r?urlappend=%3Bseq=705 2699]}} The fuselage was mounted high to provide {{cvt|14|ft}} of ground clearance, which let the helicopter taxi over a container for lifting. However, the taxiing requirement was later eliminated because of the helicopter's ability to hover and lift a load, so a second prototype would probably have had only {{cvt|8|ft|8|in}} of ground clearance, which would lower the overall height and reduce the amount of modifications required for the helicopter to fit into hangars.{{R|"USSenate1974"|p=[https://hdl.handle.net/2027/umn.31951d03440242r?urlappend=%3Bseq=701 2695]}}
The rotorcraft was designed to lift a standard Department of Defense, {{cvt|8|x|8|x|20|ft}} MILVAN container weighing up to {{cvt|22.4|ST|kg}}. 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". The helicopter was powered by three Allison XT701-AD-700 turboshafts, developed from Allison's 501-M62B engines, which each produced {{cvt|8,079|shp}} static sea-level power to rotate a shaft at 11,485 rpm. A combiner gearbox converted the power of the three shafts into two transmission shafts turning at 7,976 rpm, leading into forward and aft rotor transmissions that produced {{cvt|10,620|shp}} at 155.7 rpm. The XCH-62 was designed to be the first helicopter with a fly-by-wire flight control system without a mechanical backup.
Specifications (XCH-62A)
{{Aircraft specs
|ref=America's heavy lift helicopterWilson Flight International 13 July 1972, p.47.
|prime units?=kts
|crew=5 (pilot, copilot, flight engineer, load controlling crewman, and crew chief){{cite magazine |title=H.L.H. 1975 flight test projected: Component technology program meeting development goal|issn=0004-2560 |magazine=Army Research and Development |url=https://hdl.handle.net/2027/msu.31293012265199?urlappend=%3Bseq=228 |publication-date=January–February 1974 |pages=10–11 |hdl=2027/msu.31293012265199 |volume=15 |number=1}}
|capacity=12 troops{{R|"USSenate1974"|p=2709}}
|length m=
|length ft=87
|length in=3
|length note=(overall fuselage length)
|height m=
|height ft=32
|height in=3
|height note=(to top of pylon)
|empty weight kg=
|empty weight lb=59580
|empty weight note=
|gross weight kg=
|gross weight lb=118000
|gross weight note=
|max takeoff weight kg=
|max takeoff weight lb=
|max takeoff weight note=
|more general=
|eng1 number=3
|eng1 name=Allison T701-AD-700
|eng1 type=turboshaft
|eng1 kw=
|eng1 hp=8080
|eng1 note=
|thrust original=
|more power=
|rot number=2
|rot dia m=
|rot dia ft=92
|rot dia in=0
|rot area sqm=
|rot area sqft=13260
|rot area note=
|max speed kmh=
|max speed mph=
|max speed kts=145
|max speed note=with external load
|cruise speed kmh=
|cruise speed mph=
|cruise speed kts=
|cruise speed note=
|never exceed speed kmh=
|never exceed speed mph=
|never exceed speed kts=
|never exceed speed note=
|range km=
|range miles=
|range nmi=
|range note=
|combat range km=
|combat range miles=
|combat range nmi=150
|combat range note=
|ferry range km=
|ferry range miles=
|ferry range nmi=1500
|ferry range note=
|endurance=
|ceiling m=
|ceiling ft=
|ceiling note=
|g limits=
|climb rate ms=
|climb rate ftmin=
|climb rate note=
|sink rate ms=
|sink rate ftmin=
|sink rate note=
|disk loading kg/m2=
|disk loading lb/sqft=
|disk loading note=
|more performance=
|avionics=
}}
See also
{{aircontent
|related=
|similar aircraft=
|lists=
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References
=Citations=
{{reflist|refs=
{{cite magazine |title=Champion choppers |issn=0032-4558 |magazine=Popular Mechanics |url={{GBurl|YeQDAAAAMBAJ|p=69}} |page=69 |department=Technology update |publication-date=April 1985 |volume=162 |number=4}}
{{cite magazine |title=Meantime, back at Boeing... |issn=0032-4558 |magazine=Popular Mechanics |url={{GBurl|f9kDAAAAMBAJ|p=173}} |page=173 |department=Technology update |publication-date=September 1982 |volume=158 |number=3}}
}}
=Bibliography=
{{refbegin}}
- {{cite magazine |last=Blackwell |first=Brendan P. |title=H.L.H. |issn=0004-2471 |magazine=U.S. Army Aviation Digest |url=https://hdl.handle.net/2027/msu.31293108025135?urlappend=%3Bseq=374 |publication-date=August 1973 |pages=8–16 |volume=19 |number=8 |hdl=2027/msu.31293108025135}}
- {{cite conference |issn=0148-7191 |title=HLH and beyond |given1=Gordon H. |surname1=Fries |given2=John J. |surname2=Schneider |journal=SAE Technical Papers |series=SAE Technical Paper Series |publication-date=February 1979 |doi=10.4271/791086 |location=Los Angeles, California, U.S.A. |date=December 3–6, 1979 |volume=1 |conference=SAE Aerospace Meeting |publisher=Society of Automotive Engineers (SAE) |oclc=5817968838}}
- {{cite magazine |title=Heavy Lift Helicopter |issn=1943-1147 |magazine=Military Review |url=https://hdl.handle.net/2027/uc1.31205012550834?urlappend=%3Bseq=559 |department=Military Notes |publication-date=May 1971 |page=95 |volume=51 |number=5 |hdl=2027/uc1.31205012550834 }}
- {{cite magazine |last=Wilson |first=Michael |url=http://www.flightglobal.com/pdfarchive/view/1972/1972%20-%201771.html |title=America's heavy-lift helicopter |magazine=Flight International |publication-date=13 July 1972 |pages=44c–47 |issn=0015-3710 |archive-date=5 March 2016 |archive-url=https://web.archive.org/web/20160305074039/http://www.flightglobal.com/pdfarchive/view/1972/1972%20-%201771.html}}
{{refend}}
{{vectorsite}}
External links
{{commons category|Boeing Vertol XCH-62}}
- [http://www.helis.com/70s/h_h62.php XCH-62 Boeing Vertol HLH]
{{CH-47 Chinook family}}
{{Boeing Helicopters model numbers}}
{{Boeing rotorcraft}}
{{USAF helicopters}}
Category:1970s United States helicopters
Category:Tandem rotor helicopters
Category:Cancelled military aircraft projects of the United States