Boeing CH-47 Chinook - Wikipedia

 

Initial development

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During late 1956, the U.S. Department of the Army announced its intention to replace the Sikorsky CH-37 Mojave, which was powered by piston engines, with a new, gas turbine-powered helicopter.[2] 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-built medium-transport helicopter. Funding for full-scale development was not then available, though, and the Army vacillated on its design requirements. Some officials in Army Aviation thought that the new helicopter should be operated as a light tactical transport aimed at taking over the missions of the old piston-engined Piasecki H-21 and Sikorsky H-34 helicopters, and be consequently capable of carrying about 15 troops (one squad). Another faction in Army Aviation thought that the new helicopter should be much larger, enabling it to airlift large artillery pieces and possess enough internal space to carry the new MGM-31 "Pershing" missile system.[2]

 

During 1957, Vertol commenced work upon a new tandem-rotor helicopter, designated as the Vertol Model 107 or V-107.[3][4] During June 1958, the U.S. Army awarded a contract to Vertol for the acquisition of a small number of the rotorcraft, giving it the YHC-1A designation.[5] As ordered, the YHC-1A possessed the capacity to carry a maximum of 20 troops.[2] Three underwent testing by the Army for deriving engineering and operational data. However, the YHC-1A was considered by many figures within the Army users to be too heavy for the assault role, while too light for the more general transport role.[2] Accordingly, a decision was made to procure a heavier transport helicopter, and at the same time, upgrade the UH-1 "Huey" to serve as the needed tactical troop transport. The YHC-1A would be improved and adopted by the Marines as the CH-46 Sea Knight in 1962.[6] As a result, the Army issued a new order to Vertol for an enlarged derivative of the V-107, known by internal company designation as the Model 114, which it gave the designation of HC-1B.[7] On 21 September 1961, the preproduction Boeing Vertol YCH-1B made its initial hovering flight. During 1962, the HC-1B was redesignated the CH-47A under the 1962 United States Tri-Service aircraft designation system; it was also named "Chinook" after the Chinook people of the Pacific Northwest.[8]

 

Chinook helicopter flying overhead in Greenwich, London The distinctive sound of the Chinook helicopter, recorded May 2016. Problems playing this file? See media help.

The CH-47 is powered by two turboshaft engines, mounted on each side of the helicopter's rear pylon and connected to the rotors by drive shafts. Initial models were fitted with Lycoming T55 engines rated at 2,200 hp (1,600 kW) each. The counter-rotating rotors eliminate the need for an antitorque 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 and dropping. While hovering over a specific location, a twin-rotor helicopter has increased stability over a single rotor when weight is added or removed, for example, when troops drop from or begin climbing up ropes to the aircraft, or when other cargo is dropped. If one engine fails, the other can drive both rotors.[9] 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 air mobility effort.[2]

Improved and later versions

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Improved and more powerful versions of the CH-47 have been developed since the helicopter entered service. Often, the same airframe was upgraded to later standards, or sometimes the airframes were built to the newer upgrade. The U.S. Army's first major design leap was the now-common CH-47D, which entered service in 1982. Improvements from the CH-47C included upgraded engines, composite rotor blades, a redesigned cockpit to reduce pilot workload, improved and redundant electrical systems, an advanced flight control system, and improved avionics.[10] The latest (2009) mainstream generation is the CH-47F, which features several major upgrades to reduce maintenance, digitized flight controls, and is powered by two 4,733-horsepower (3,529 kW) Honeywell engines.[11]

 

An example of a British upgraded version is the HC.4, which first flew on 9 December 2010.[12]

A commercial model of the Chinook, the Boeing-Vertol Model 234, is used worldwide for logging, construction, forest fire suppression, and petroleum-extraction operations. In December 2006, Columbia Helicopters Inc. purchased the type certificate of the Model 234 from Boeing.[13] The Chinook has also been licensed to be built by companies outside the United States, such as Agusta (later AgustaWestland, now Leonardo) in Italy and Kawasaki in Japan.[14][15]

CH-47F orders

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In February 2007, the Royal Netherlands Air Force became the first international customer of the CH-47F model, expanding their Chinook fleet to 17.[16] On 10 August 2009, Canada signed a contract for 15 extensively modified and upgraded CH-47Fs for the Canadian Forces, later delivered in 2013–2014 with the Canadian designation CH-147F.[11][17] On 15 December 2009, Britain announced its Future Helicopter Strategy, including the purchase of 24 new CH-47Fs to be delivered from 2012.[18] Australia ordered seven CH-47Fs in March 2010 to replace its six CH-47Ds between 2014 and 2017.[19][20] In September 2015, India approved purchase of 15 CH-47F Chinooks.[21] On 7 November 2016, Singapore announced that the CH-47F would replace its older Chinooks, which had been in service since 1994, enabling the Republic of Singapore Air Force to meet its requirements for various operations, including search-and-rescue, aeromedical evacuation, and humanitarian assistance and disaster relief operations.[22] The German government announced in June 2022 that the CH-47F Block 2 was selected as the winner of its heavy helicopter program to replace its Sikorsky CH-53G Sea Stallion fleet.[23][24] Germany is planning to buy sixty airframes to boost heavy lift capability.[25]

Spain had 17 CH-47s, which it is planning to upgrade to CH-47F standards.[26] By 2023, 13 CH-47Ds were upgraded to CH-47Fs, and additionally, four newly built CH-47Fs were acquired.[27]