Boeing Vertol XCH-62
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The Boeing Vertol XCH-62 (Model 301) was a triple-
turbine A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...
, heavy-lift
helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...
project designed for the
United States Army The United States Army (USA) is the land service branch of the United States Armed Forces. It is one of the eight U.S. uniformed services, and is designated as the Army of the United States in the U.S. Constitution.Article II, section 2, cla ...
by
Boeing Vertol Boeing Rotorcraft Systems (formerly Boeing Helicopters and before that Boeing Vertol) is the former name of an American aircraft manufacturer, now known as Vertical Lift division of Boeing Defense, Space & Security. The headquarters and main r ...
. 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 The Boeing CH-47 Chinook is a tandem rotor helicopter developed by American rotorcraft company Vertol and manufactured by Boeing Vertol. The Chinook is a heavy-lift helicopter that is among the heaviest lifting Western helicopters. Its name, C ...
is a large helicopter by American standards, its payload of is dwarfed by the huge Soviet-Russian heavy-lift helicopters such as the
Mil Mi-26 The Mil Mi-26 (russian: link=no, Миль Ми-26, NATO reporting name: Halo) is a Soviet/Russian heavy transport helicopter. Its product code is ''Izdeliye 90''. Operated by both military and civilian operators, it is the largest and most po ...
, with payload, and the experimental
Mil Mi-12 The Mil V-12 (NATO reporting name: Homer), given the project number ''Izdeliye 65'' ("Item 65"), is the largest helicopter ever built. The designation "Mi-12" would have been the name for the production helicopter and was not applied to the V-12 ...
, with 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. The
U.S. Department of Defense The United States Department of Defense (DoD, USDOD or DOD) is an executive branch department of the federal government charged with coordinating and supervising all agencies and functions of the government directly related to national secur ...
(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. 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. 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. 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 Flight testing is a branch of aeronautical engineering that develops specialist equipment required for testing aircraft behaviour and systems. Instrumentation systems are developed using proprietary transducers and data acquisition systems. D ...
. 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. The designers of the
Mil Mi-26 The Mil Mi-26 (russian: link=no, Миль Ми-26, NATO reporting name: Halo) is a Soviet/Russian heavy transport helicopter. Its product code is ''Izdeliye 90''. Operated by both military and civilian operators, it is the largest and most po ...
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 The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research. NASA was established in 1958, succeeding t ...
(NASA), and the
Defense Advanced Research Projects Agency The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...
(DARPA) collaborated on a scheme to finish the XCH-62 for experimental flights, requesting a combined USD$71 million in funding through fiscal year 1989. However, Congress declined funding, and the craft remained incomplete. The prototype was moved from a warehouse storage site in
Philadelphia, Pennsylvania Philadelphia, often called Philly, is the largest city in the Commonwealth of Pennsylvania, the sixth-largest city in the U.S., the second-largest city in both the Northeast megalopolis and Mid-Atlantic regions after New York City. Sinc ...
, floated by barge to
Panama City, Florida Panama City is a city in and the county seat of Bay County, Florida, United States. Located along U.S. Highway 98 (US 98), it is the largest city between Tallahassee and Pensacola. It is the more populated city of the Panama City–Lynn ...
, and then lifted by a Chinook CH-47D helicopter to the
US Army Aviation Museum The United States Army Aviation Museum is an aviation museum located on Fort Rucker near Daleville, Alabama. It has the largest collection of helicopters held by a museum in the world.Phillips 1992, p. 37.Purner 2004, p. 204. The museum feature ...
at
Fort Rucker, Alabama Fort Rucker is a U.S. Army post located primarily in Dale County, Alabama, United States. It was named for a Civil War officer, Confederate General Edmund Rucker. The post is the primary flight training installation for U.S. Army Aviators and ...
on December 8, 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. In 2008, several parts were sent to the Helicopter Museum at
Weston-super-Mare Weston-super-Mare, also known simply as Weston, is a seaside town in North Somerset, England. It lies by the Bristol Channel south-west of Bristol between Worlebury Hill and Bleadon Hill. It includes the suburbs of Mead Vale, Milton, Oldmixon ...
(United Kingdom), to be exhibited there.


Design

The XCH-62 is a
tandem rotor Tandem, or in tandem, is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction. The original use of the term in English was in ''tandem harness'', which is used for two ...
helicopter, with four blades on each rotor. Its rotor diameter was to be , fuselage length , and footprint length . The maximum width with blades folded was . The rotor blade had a length was , a chord of , and a weight of . The fuselage was mounted high to provide 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 of ground clearance, which would lower the overall height and reduce the amount of modifications required for the helicopter to fit into hangars. The rotorcraft was designed to lift a standard
Department of Defense Department of Defence or Department of Defense may refer to: Current departments of defence * Department of Defence (Australia) * Department of National Defence (Canada) * Department of Defence (Ireland) * Department of National Defense (Philipp ...
, MILVAN container weighing up to . 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 static sea-level power to rotate a shaft at 11,485
rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or with the notation min−1) is a unit of rotational speed or rotational frequency for rotating machines. Standards ISO 80000-3:2019 defines a unit of rotation as the dimensionl ...
. 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 at 155.7 rpm. The XCH-62 was designed to be the first helicopter with a
fly-by-wire Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. The movements of flight controls are converted to electronic signals transmitted by wires, and flight control ...
flight control system A conventional fixed-wing aircraft flight control system consists of flight control surfaces, the respective cockpit controls, connecting linkages, and the necessary operating mechanisms to control an aircraft's direction in flight. Aircraft ...
without a mechanical backup.


Specifications (XCH-62A)


See also


References


Citations


Bibliography

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External links


XCH-62 Boeing Vertol HLH
{{USAF helicopters H-062 Boeing XCH-62 1970s United States helicopters Tandem rotor helicopters Cancelled military aircraft projects of the United States Three-turbine helicopters