XCH-62 Heavy Lift Helicopter [HLH]
The XCH-62 is a tandem-rotor, shaft-driven, heavy-lift helicopter. The XCH-62, an HLH under development at the time, was viewed strictly as a "flying truck" to be used only over friendly territory. This big "flying crane" -- the XCH-62 -- would be capable of carrying 20 tons over a distance of nearly 40km. The U.S. Army Heavy Lift Helicopter (HLH) represents a large rotorcraft which was developed by an American aerospace company.
The US Army Heavy Lift Helicopter [HLH] specification was approved in May 1971 for a 22-ton payload class helicopter. The only XCH-62 built (Serial number 73-22012) was put into storage at the US Army Aviation Museum at Fort Rucker Alabama prior to completion when the program was cancelled in October 1974. The Sikorsky S-73, not built, was the Sikorsky entry for the HLH program.
The HLH was intended to be a multi-service helicopter amd as such would be available for lifting most of the heavier items of Navy and Marine Corps equipment during operations on shore which me beyond the capability of the CH-53E There were also some items of essential Army tactical equipment which were heavier than the defined lift capability of the CH-53E. The Army anticipated that with fuel and range trade-offs these, too, could be lifted by the HLH.
The Army was using the CH-54 helicopter, which was generelly capable of lifting in the neighborhood of 9.5 to 11.5 tons at sea level, depending on differing operating conditions. It also used the CH-47C, the latest version of which could lift approximately 10 to 12 tons as governed by existing operating conditions.
The primary mission of the HLH would be the unloading of containerized cargo. Its 22.5 ton design point was based on the need to lift 20-foot containers having a 22.4~ton gross weight capacity. In fiscal year 1972, about 80 percent of these containers used in overseas military shipments carried cargo weighing less than 16 tons. There were only three items shipped that could gross a 20-foot container, one being ammunition. However, restrictions on the transportation of ammunition had for reasons of security and safety up to that time the, limited the use of containers for this purpose. The Army expected the magnitude of containerized ammunition shipments to increase, having obtained the approval from the regulatory agency in February 1973 to ship ammuniition in its Government-owned MILVAN containers for a period of one year. The Army was also working on resolving remaining difficulties in order that it till also be able to ship smmunition in commercial containers which it uses extensively. The average gross weight of cargo shipped overseas im 20-foot containers whould increase once the Army began to use them for this purpose on a regular basis.
The lift capability of a helicopter must be understood in terms of the environmental conditions and load factors in which it operates. Altitude and temperature, for example, are two factors which influence lift capability. Generally, the lift capability is greatest at sea level with low temperatures and diminishes at higher elevations and higher temperatures.
Qn June 25, 1971, the Amry awarded a contract to the Boeing Vertol Compan for the critical components phase of the Heavy Lift Helicopter development program. It provided for the design, construction and test of critical components of a 22.5~tom payload helicopter. The critical components comprise such items as the rotor drive system, cargo handling system, ada flight control system. From this phase the Army expecte to gain increased technical knowledge to reduce the risk of developing a 22.5 ton helicopter, and a cost data base to assure that cost estimates for such a helicopter were credible.
The HLH would be used by the Army for both logistical and tactical missions. The logistical mission involves the off-loading frm ship to shore of containerized cargo. The HLH is needed in situations where it alone could provfde this lift capability -- situations such as arise pat unimproved ports where cranes were not available on shore to perform this service. The tactical mission involves lifting heavy tactical equipment such as vehicles, artillery pieces snd construction equiment for onshore operations.
The HLH still left the Army without the capability of lifting some of its heavy tactical equipment at higher elevations unless fuel and range were reduced. This is because the lift capability diminishes as elevation increases. At 4,000 feet above sea level, 95°F, for example (the Army's prime operatbg condition for tactical missions), the lift capability of the HLH was estimated to be 19.2 tons.
One experimental machine -- the Model 347 -- was initiated in January 1969. Vertol began a cooperative program with the Army to develop the Model 347 advanced-technology helicopter. This involved a rebuild of an existing CH-47A, #65-7992, featuring a fuselage stretch of 110"; four-bladed rotors; an aft pylon extended upward 30" to increase the distance between rotor planes (thus reducing noise levels); retractable landing gear; and elements borrowed from the Soviet Mil organization's heavy lift helicopters, including hydraulically actuated detachable wings permitting incidence control throughout the aircraft's flight envelope to improve range and payload; and a "booth" that could be extended from under the nose to house a pilot for control of crane loads.
The initial flight was on 27 May 1970 at the Vertol Division's Center 3 Flight Test Facility at Eddystone, Pennsylvania. The machine was later fitted with a fly-by-wire flight control system, and was run through evaluations for several years in the early 1970s.
Some of the Model 347's features were used to help design the XCH-62 HLH and CH-47D, including reliability improvements, flying qualities, flight control systems, external handling systems, and new hydraulic systems. Regardless, the Army could not economically justify the four-bladed rotor system or fuselage modifications in future Chinook Models. Following completion of it's test program, the Model 347 was retired from service and donated to the Army Aviation Museum.
In the early 1970's with the HLH Advanced Technology Components (ATC) program, the development of large rotorcraft transmission and drive systems was started. Failures in the spiral bevel gearing were experienced in tests because the employed method of analysis 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.
In 1983, NASA and DARPA ( Defence Advanced Research Projects Agency) plans were initiated to resume a Heavy Lift Research Vehicle [HLRV] test program, with a possible first flight in 1985, but was cancelled again.
The helicopter sat in storage until 1987 when it was decided that it should be placed in to the US Army Aviation Museum at Ft Rucker AL. In December 2005 the XCH-62 Boeing HLH helicopter at the US Army Aviation Museum, Fort Rucker, was intentionally destroyed and removed The following answer was provided by Steve Maxham, Director, US Army Aviation Museum: "The operative reason for this item being de-accessioned is that it was never an aircraft. It never flew. It was essentially an incomplete concept model, the shell of an idea. The contract for production was halted mid-way through the project. It was never structurally completed. It was never mechanically completed. It was never electrically harnessed. There was only one rotor head produced, the second was not. There were only blades made for the one head. There were no drive train components. The upper structures both fore and aft were never manufactured. The interior was never completed. In no way, shape, or form did it qualify as an aircraft, historic or otherwise."
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