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Flying Crane Helicopter

Helicopters have been found useful in both military and civil applications. Among the many uses that helicopters may serve, the helicopter due to its hovering capability has been found particularly suitable for use as a crane for lifting various types of structures both on land and offshore. In other applications, because of its maneuverability, the helicopter has been utilized and lift and transport cargo from one location to another.

The need for vertically lifting heavy or bulky loads and transporting them over long distances has far outgrown conventional devices whereby these loads may be raised from the ground, placed on vehicles, and moved to new sites. This is particularly true where lack of roads makes such operations very difficult or very expensive; for example, removing trees from forests to bring them to a logging site or to a sawmill. Other important uses include hauling cargo between ship and shore, moving large structures such as bridge segments, and transporting houses and other buildings, manufactured in factories, to specific sites.

In order to utilize a helicopter as a flying crane or a cargo transporting vehicle, a cargo hook has been provided on the underside of the helicopter's fuselage for engaging a loop at the end of a cable connected to the load to be transported by the helicopter. To minimize the impact of the cargo hook installation on the structural design of the helicopter, the cargo hook is usually mounted rigidly to the underside of the helicopter. Thus, a load that is lifted by a helicopter at the end of a line that is connected to a helicopter by a rigidly mounted cargo hook will impose forces on the helicopter that pass through the point of attachment at the bottom of the fuselage.

A flying crane was generally visualized in the 1950s as a sort of heavy cargo unloader consisting of a skeleton fuselage, lift and power systems, and a pilot cab containing the flight and power controls. The flying crane's use would be to transport heavy pieces of materiel, rolling stock, engineer equipment, or large tonnages of bulk supplies.

Initially, the first Marine Corps requirement for a flying crane helicopter was submitted to the CNO on 21 November 1950. The primary mission envisioned was to transfer aircraft from replenishment class 55 or 105 carriers to the Midway class CVLs and smaller Independence class CVBs. Soon thereafter, on 27 December 1950, the CNO published a letter to all his departments setting up a requirement for the flying crane helicopter with the specification that it be capable of lifting a payload of 25,000 pounds over a radius of 10 miles.

Later in 1954, a Marine Corps Development Center study on helicopter requirements saw a need for a 20,000-pound payload XHCH-1 (Cargo Unloader Helicopter) to land the ONTOS (anti-tank weapon system) and 2-ton cargo trucks. The XHCH was then an experimental helicopter being built by McDonnell Aircraft Corporation in accordance with the CNO 's 1950 requirement, but it was never produced.

In 1956 the Marine Corps Equipment Development Policy and Guide also saw a requirement for a cargo unloader helicopter, again with a 25,000-pound payload capability. In 1959, the Director, Marine Corps Development Center stated a requirement for a crane helicopter. He specified in a letter to the Commandant : "One of the most serious deficiencies in our vertical assault capability that exists today is the inability to lift heavy equipment essential to the landing force . . . It is considered that the number of pieces of equipment requiring heavy lift in support of a landing force would not be great . . . It now appears that developmental advances in rotor design and gas turbine engines is such that with proper direction, support and guidance, a helicopter capable of lifts up to 25,000 pounds could be obtained in a few years. It is, therefore, recommended that Headquarters, US Marine Corps : a. State an operational requirement for a crane type helicopter capable of carrying a payload of 12,000 pounds with a minimum combat radius of 50 nautical miles. Encourage and support the aircraft industry to develop on an expeditious basis a crane type helicopter to meet this requirement. b. Program continued development of a crane type helicopter capable of carrying a payload of 20,000 pounds with a minimum combat radius of 50 nautical miles but with a greater combat radius if it can be achieved. c. Procure at an early date at least two prototypes of the most promising " Flying Crane" type helicopter for user test."

In March 1960, the Coordinator, MCLFDA submitted to CMC a "Proposed Operational Requirement for Landing Force VTOL Aircraft." Included therein was a "VTOL Cargo Unloader Aircraft (Flying Crane) " with a lift capability of 25,000 pounds. One significant fact concerning these views was that they were an expression of the "All helicopter concept" philosophy of LFB-17.

Why not a flying crane helicopter before 1960? Basically, the manufacturers could not produce one capable of lifting the desired weight. The first model of Piasecki's XH-16 was truly a flying crane as it was designed to carry its load in detachable "pods." Piasecki's second XH-16 had a large cabin and was the type which had interested the Marine Corps as an assault transport. Both aircraft failed primarily because the state of power plant and transmission development had not advanced sufficiently to match the demand . Also the Navy-funded McDonnell's XHCH-1 failed due to the same shortcomings.

During 1956-1958, the US Army Transportation Research and Engineering Command (TRECOM) actively studied the technical aspects of flying crane helicopters. Research contracts to conduct design and cost analysis were let to leading aircraft manufacturers. TRECOM examined the flying crane concept and evaluated the conclusions reached by the several manufacturers. The flying crane had singular requirements and design considerations which were not inherent in helicopters then in operation, and was very sensitive to changes in design, operating radius, and payload. For each payload and range combination there was an optimum power plant (shaft drive/tip-jet drive) and rotor (single, tandem, quad) combination. Flying cranes were very large, very heavy aircraft. Rotor diameters on the order of 120 feet and empty weights in excess of 30,000 pounds were representative of flying cranes designed for payloads of 12 tons and operating radii of 50 nautical miles. A pure flying crane helicopter would have been of little value to the Marine Corps as there was only a limited opportunity for its useful employment in combat and, because of its size, it was difficult to load in amphibious shipping.

To satisfy the requirement for heavy lifts without a true flying crane, it was envisioned that a heavy cargo helicopter could be stripped of its auxiliary power unit, communications/navigation equipment, and other removable equipment and operate with a reduced fuel load and minimum crew. It then could become a flying crane, of sorts, capable of lifting five or six tons of external cargo for a tactically significant distance. Handicapped by not having a flying crane, the Marine Corps' course of action would be to continue to make up light loads, and sectionalize heavy items of equipment, and employ the future CH-53 8,000-pound payload helicopters in a limited flying crane role until technology could produce a smaller, more versatile, and efficient crane helicopter.



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Page last modified: 07-07-2011 02:32:13 ZULU