In 1960, Boeing bought Vertol Aircraft Co., a helicopter manufacturer in Philadelphia, Pa. The company had three tandem-rotor helicopters under production: the Chinook for the Army, the Sea Knight for the Navy and the Marines, and the commercial 107-11 for the airlines. Vertol started out as the P-V Engineering Forum, owned by Frank Piasecki, which established the "banana-shaped," two-rotor helicopter in 1945. Piasecki left the corporation in 1955, and it was renamed Vertol the following year. The first in the long line of Chinooks was the YHC-1B tandem-rotor transport helicopter that rolled out in 1961. It was designed to serve the Army and Air Force as a medium-lift helicopter and evolved into several versions. Chinooks first were used in combat in 1965 during the Vietnam conflict. By 1968, the Chinook had put in 161,000 hours of flying time, carrying 22.4 million passengers and more than 1.3 million tons of cargo. During the last days of the war, one Chinook is reported to have carried 147 refugees in a single lift. CH-47A, B and C models served with distinction for a decade until the war's end in 1975. After the war, Boeing and the Army began planning a major fleet upgrade that led to development of the CH-47D. Almost 500 early model Chinooks went through an extensive modernization process in Philadelphia that produced an essentially new CH-47 fleet. Boeing completed first D-model deliveries in 1982 and concluded the program in 1994. Only two U.S. Army CH-47Ds were built to replace aircraft losses during the Persian Gulf War. All other D models are modernized aircraft. The CH-47D remains the U.S. Army standard and features composite rotor blades, an improved electrical system, modularized hydraulics, triple cargo hooks, avionics and communication improvements, and more powerful engines that can handle a 25,000-pound useful load, nearly twice the Chinook's original lift capacity. The CH-47D Chinook was a central element in U.S. Army operations in the Persian Gulf War, where more than 160 Chinooks carried U.S. and Allied troops to outflank Iraqi forces and cut off their retreat from Kuwait. During 2002, the Chinook's high speed and large payload gave it the lowest cost-per-ton-mile of any transport helicopter available. During 2002, Boeing was developing the CH-47F, scheduled for first production in 2004, and was under contract to modernize at least 300 Chinooks to the new F-model standard, which features reduced vibration effects, an integrated cockpit control system and more powerful engines with digital fuel controls. These improvements will make the Chinook fully compatible with 21st century operational and war-fighting requirements and improve the aircraft's efficiency and effectiveness. U.S. Army Special Operations Forces operate Special Operations Chinooks, designated MH-47Ds and MH-47Es, among the most advanced rotorcraft in operation today. They have fully integrated digital cockpits; forward-looking infrared, terrain-following and terrain-avoidance radar; long-range fuel tanks; and aerial refueling capability. The MH-7E's integrated avionics system permits global communications and navigation. Using the Chinook airframe, Boeing Helicopters also built the Model 234, the commercial Chinook used for passengers, cargo, oil and gas exploration, and logging.

• published: 19 Mar 2015
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