| XCH-62 HLH | |
|---|---|
 | |
| Role | Heavy-lift helicopter |
| Manufacturer | Boeing Vertol |
| Status | Program terminated |
| Primary user | United States Army |
| Number built | 1 (never completed) |
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.
While the CH-47 Chinook is a large helicopter by American standards, its payload of 28,000 lb (13,000 kg) is dwarfed by the huge Soviet-Russian heavy-lift helicopters such as the Mil Mi-26, with 44,000 lb (20,000 kg) payload, and the experimental Mil V-12, with 55,000 to 88,000 lb (25,000 to 40,000 kg) 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. [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] 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. [5] : 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. [6] The designers of the Mil Mi-26 avoided similar problems by using a split-torque design in the main rotor transmission. [7]
Subsequent attempts were made to finish the incomplete XCH-62 prototype, [8] [9] which had a serial number of 73-22012. [10] 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. [11] 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, [12] and then lifted by a CH-47D Chinook helicopter to the US Army Aviation Museum at Fort Rucker, Alabama on December 8, 1987. [13] 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. [10] In 2008, several parts were sent to the Helicopter Museum at Weston-super-Mare (United Kingdom), to be exhibited there. [14]
The XCH-62 is a tandem rotor helicopter, with four blades on each rotor. Its rotor diameter was to be 92 ft (28 m), fuselage length 89 ft 3 in (27.20 m), and footprint length 162 ft 3 in (49.45 m). The maximum width with blades folded was 29 ft 10 in (9.09 m). [15] The rotor blade had a length was 42 ft (13 m), a chord of 40 in (1,000 mm), and a weight of 750 lb (340 kg). [16] : 2699 The fuselage was mounted high to provide 14 ft (4.3 m) 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 8 ft 8 in (2.64 m) of ground clearance, which would lower the overall height and reduce the amount of modifications required for the helicopter to fit into hangars. [16] : 2695
The rotorcraft was designed to lift a standard Department of Defense, 8 ft × 8 ft × 20 ft (2.4 m × 2.4 m × 6.1 m) MILVAN container weighing up to 22.4 short tons (20,300 kg). [15] 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-AD-700 turboshafts, developed from Allison's 501-M62B engines, which each produced 8,079 shp (6,025 kW) static sea-level power [15] 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 10,620 shp (7,920 kW) at 155.7 rpm. [17] The XCH-62 was designed to be the first helicopter with a fly-by-wire flight control system without a mechanical backup. [15]
Data from America's heavy lift helicopter [18]
General characteristics
Performance
Related development
Aircraft of comparable role, configuration, and era
Related lists
The Boeing Vertol CH-46 Sea Knight is a medium-lift tandem-rotor transport helicopter powered by twin turboshaft engines. It was designed by Vertol and manufactured by Boeing Vertol following Vertol's acquisition by Boeing.
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, Chinook, is from the Native American Chinook people of Oregon and Washington state.
The Sikorsky CH-53E Super Stallion is a heavy-lift helicopter operated by the United States military. As the Sikorsky S-80, it was developed from the CH-53 Sea Stallion, mainly by adding a third engine, adding a seventh blade to the main rotor, and canting the tail rotor 20°. It was built by Sikorsky Aircraft for the United States Marine Corps. The less common MH-53E Sea Dragon fills the United States Navy's need for long-range minesweeping or airborne mine countermeasures missions, and performs heavy-lift duties for the Navy. The Sikorsky CH-53K King Stallion, which has new engines, new composite rotor blades, and a wider aircraft cabin, is set to replace the CH-53E.
The Bell XV-15 is an American tiltrotor VTOL aircraft. It was the second successful experimental tiltrotor aircraft and the first to demonstrate the concept's high speed performance relative to conventional helicopters.
The Sikorsky CH-54 Tarhe is an American twin-engine heavy-lift helicopter designed by Sikorsky Aircraft for the United States Army. It is named after Tarhe, an 18th-century chief of the Wyandot Indian tribe whose nickname was "The Crane". The civil version is the Sikorsky S-64 Skycrane.
The Yakovlev Yak-24 is a Soviet twin-engine, tandem rotor, transport helicopter developed by Yakovlev in the 1950s. The Yak-24 saw limited use in the Soviet Air Force, and the exact number produced and duration of service are unknown due to inconsistencies in data.
The Mil V-12, given the project number Izdeliye 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 prototypes.
The Mil Mi-6, given the article number izdeliye 50 and company designation V-6, is a Soviet/Russian heavy transport helicopter that was designed by the Mil design bureau. It was built in large numbers for both military and civil use and was the largest helicopter in production until the Mil Mi-26 was put in production in 1980.
The Piasecki H-21 Workhorse/Shawnee is an American helicopter, the fourth of a line of tandem rotor helicopters designed and built by Piasecki Helicopter. Commonly called "the flying banana", it was a multi-mission helicopter, using wheels, skis and floats.
The Mil Mi-26 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 powerful helicopter to have gone into serial production.
The Allison T56 is an American single-shaft, modular design military turboprop with a 14-stage axial flow compressor driven by a four-stage turbine. It was originally developed by the Allison Engine Company for the Lockheed C-130 Hercules transport entering production in 1954. It has been a Rolls-Royce product since 1995 when Allison was acquired by Rolls-Royce. The commercial version is designated 501-D. Over 18,000 engines have been produced since 1954, logging over 200 million flying hours.
The Bristol Type 192 Belvedere is a British twin-engine, tandem rotor military helicopter built by the Bristol Aeroplane Company. It was designed by Raoul Hafner for a variety of transport roles including troop transport, supply dropping and casualty evacuation. It was operated by the Royal Air Force (RAF) from 1961 to 1969. The Belvedere was Britain's only tandem rotor helicopter to enter production, and one of the few not built by Piasecki or Boeing.
The Sikorsky CH-53K King Stallion is a heavy-lift cargo helicopter designed and produced by Sikorsky Aircraft. The King Stallion is an evolution of the long running CH-53 series of helicopters which have been in continuous service since 1966, and features three uprated 7,500 shp (5,590 kW) engines, new composite rotor blades, and a wider aircraft cabin than its predecessors. It is the largest and heaviest helicopter in the U.S. military.
The Sikorsky S-72 was an experimental compound helicopter developed by helicopter manufacturer Sikorsky Aircraft.
The Boeing Vertol YUH-61 was a twin turbine-engined, medium-lift, military assault/utility helicopter. The YUH-61 was the runner-up in the United States Army Utility Tactical Transport Aircraft System (UTTAS) competition in the early 1970s to replace the Bell UH-1 Iroquois helicopter. At the end of the flyoff program, Sikorsky Aircraft was awarded a contract to develop and build its UH-60A entry.
The Boeing Model 360 is an American experimental medium-lift tandem rotor cargo helicopter developed privately by Boeing to demonstrate advanced helicopter technology. The aircraft was intended as a technology demonstrator, with no plans to put the type into production, and many of its design features were carried onto other programs including the RAH-66 Comanche and V-22 Osprey. The sole prototype has been preserved and is a static exhibit at the American Helicopter Museum in West Chester, Pennsylvania.
The Honeywell T55 is a turboshaft engine used on American helicopters and fixed-wing aircraft since the 1950s, and in unlimited hydroplanes since the 1980s. Today, there have been more than 6,000 of these engines built. It is produced by Honeywell Aerospace, a division of Honeywell based in Phoenix, Arizona, and was originally designed by the Turbine Engine Division of Lycoming Engines in Stratford, Connecticut, as a scaled-up version of the smaller Lycoming T53. The T55 serves as the engine on several major applications including the CH-47-Chinook, the Bell 309, and the Piper PA-48 Enforcer. The T55 also serves as the core of the Lycoming ALF 502 turbofan. Since the T55 was first developed, progressive increases in airflow, overall pressure ratio, and turbine inlet temperature have more than tripled the power output of the engine.
The Sikorsky S-73 was a proposed aircraft design to meet the United States Army requirement in 1970 for a Heavy Lift Helicopter (HLH) capable of carrying 45,000 lb, a lifting capacity more than twice that of Sikorsky's most powerful helicopter at that time.
The Allison T56 turboprop engine has been developed extensively throughout its production run, the many variants are described by the manufacturer as belonging to four main series groups.
The Boeing Vertol BV-347 is an experimental helicopter built by Boeing Vertol from a converted CH-47A Chinook.
The initial version of this article was based on a public domain article from Greg Goebel's Vectorsite.
