CH-47 Chinook

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The Boeing CH-47 Chinook is a twin-engine, tandem rotor heavy-lift helicopter. Its top speed of 170 knots and was faster than contemporary utility and attack helicopters of the 1960s. It is one of the few aircraft of that era such as the C-130 and the UH-1 ‘Huey’ that is still in production and front line service with over 1,179 built so far. Its primary roles include troop movement, artillery emplacement and battlefield resupply. It has a wide loading ramp at the rear of the fuselage and three external-cargo hooks.

Boeing Vertol initially produced and designed the Chinook in the early 1960s. The helicopter is now produced by Boeing Integrated Defense Systems. Chinooks have been sold to 16 nations. Although some nations operate larger helicopters such as the Russian Mil Mi-26, the Chinook remains the heaviest lifting helicopter used by its largest operators, the U.S. Army and the Royal Air Force, see Boeing Chinook (UK variants).

In late 1956 the Department of the Army announced plans to replace the CH-37 Mojave, which was powered by piston engines, with a new, turbine-powered helicopter. Turbine engines were also a key design feature of the smaller UH-1 “Huey” utility helicopter. Following a design competition, in September 1958, a joint Army-Air Force source selection board recommended that the Army procure the Vertol medium transport helicopter. However, funding for full-scale development was not then available, and the Army vacillated on its design requirements. Some in the Army aviation corps thought that the new helicopter should be a light tactical transport aimed at taking over the missions of the old piston-engined H-21 and H-34 helicopters, and consequently capable of carrying about fifteen troops (one platoon). Another faction in the Army aviation corps thought that the new helicopter should be much larger to be able to airlift a large artillery piece, and to also have enough to carry the new Army MGM-31 “Pershing” Missile System.

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Vertol began work on a new tandem-rotor helicopter designated Vertol Model 107 or V-107 in 1957. In June 1958, the US Army awarded a contract to Vertol for the aircraft under the YHC-1A designation. The YHC-1A had a capacity for 20 troops. Three were tested by the Army to derive engineering and operational data. However, the YHC-1A was considered by most of the Army users to be too heavy for the assault role and too light for the transport role. The decision was made to procure a heavier transport helicopter and at the same time upgrade the UH-1 “Huey” as a tactical troop transport. The YHC-1A would be improved and adopted by the Marines as the CH-46 Sea Knight in 1962. The Army then ordered the larger Model 114 under the designation HC-1B. The pre-production Boeing Vertol YCH-1B made its initial hovering flight on September 21, 1961. In 1962 the HC-1B was redesignated the CH-47A under the 1962 United States Tri-Service aircraft designation system.

The name “Chinook” alludes to the Chinook people of the Pacific Northwest. The CH-47 is powered by two turboshaft engines, mounted on either side of the helicopter’s rear end and connected to the rotors by driveshafts. Initial models were fitted with engines of 2,200 horsepower. The counter-rotating rotors eliminate the need for an anti-torque vertical rotor, allowing all power to be used for lift and thrust. The ability to adjust lift in either rotor makes it less sensitive to changes in the center of gravity, important for the cargo lifting role. If one engine fails, the other can drive both rotors. The “sizing” of the Chinook was directly related to the growth of the Huey and the Army’s tacticians’ insistence that initial air assaults be built around the squad. The Army pushed for both the Huey and the Chinook, and this focus was responsible for the acceleration of its airmobility effort

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