Boeing CH-47 Chinook

The Boeing CH-47 Chinook is an American twin-engine, tandem rotor heavy-lift helicopter. Its top speed of 170 knots (196 mph, 315 km/h) is 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 Hercules and the UH-1 Iroquois, that is still in production and front line service with over 1,179 built to date. 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.

The Chinook was designed and initially produced by Boeing Vertol in the early 1960s. The helicopter is now produced by Boeing Rotorcraft Systems. Chinooks have been sold to 16 nations with the US Army and the Royal Air Force (see Boeing Chinook (UK variants)) being the largest users. The CH-47 is among the heaviest lifting Western helicopters.

Design and Development

Early development

In late 1956, the United States 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 squad). 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 have enough internal space to carry the new MGM-31 "Pershing" Missile System. 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 21 September 1961. In 1962 the HC-1B was redesignated the CH-47A under the 1962 United States Tri-Service aircraft designation system. he name "Chinook" alludes to the Chinook people of the Pacific Northwest. The CH-47 is powered by two turboshaft engines, mounted on each 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 air mobility effort.

Improved and later versions

Improved and more powerful versions of the CH-47 have been developed since the helicopter entered service. The US 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. The latest 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 Honeywell engines. A commercial model of the Chinook, the Boeing-Vertol Model 234, is used worldwide for logging, construction, fighting forest fires, and supporting petroleum extraction operations. On 15 December 2006, the Columbia Helicopters company of the Salem, Oregon, metropolitan area, purchased the Type Certificate of the Model 234 from Boeing. The Chinook has also been licensed to be built by companies outside of the United States, such as Elicotteri Meridionali (now AgustaWestland) in Italy, Kawasaki in Japan.

Varians

HC-1B

The pre-1962 designation for Model 114 development aircraft that would be re-designated CH-47 Chinook.

CH-47A

The all-weather, medium-lift CH-47A Chinook was powered initially by Lycoming T55-L-5 engines rated at 2,200 horsepower (1,640 kW) but then replaced by the T55-L-7 rated at 2,650 hp (1,980 kW) engines or T55-L-7C engines rated at 2,850 hp (2,130 kW). The CH-47A had a maximum gross weight of 33,000 pounds (15,000 kg). Initial delivery of the CH-47A Chinook to the US Army was in August 1962. A total of 349 were built.

ACH-47A

The ACH-47A was originally known as the Armed/Armored CH-47A (or A/ACH-47A). It was officially designated ACH-47A by US Army Attack Cargo Helicopter and unofficially Guns A Go-Go. Four CH-47A helicopters were converted to gunships by Boeing Vertol in late 1965. Three were assigned to the 53rd Aviation Detachment in South Vietnam for testing, with the remaining one retained in the US for weapons testing. By 1966, the 53rd was redesignated the 1st Aviation Detachment (Provisional) and attached to the 228th Assault Support Helicopter Battalion of the 1st Cavalry Division (Airmobile). By 1968, only one gunship remained, and logistical concerns prevented more conversions. It was returned to the United States, and the program stopped. The ACH-47A carried five M60D 7.62x51 mm machine guns or M2HB .50 caliber machine guns, provided by the XM32 and XM33 armament subsystems, two M24A1 20 mm cannons, two XM159B/XM159C 19-Tube 2.75 in rocket launchers or sometimes two M18/M18A1 7.62×51 mm gun pods, and a single M75 40 mm grenade launcher in the XM5/M5 armament subsystem (more commonly seen on the UH-1 series of helicopters). The surviving aircraft, Easy Money, has been restored and is on display at Redstone Arsenal, Alabama.

CH-47B

The CH-47B was an interim solution while Boeing worked on a more substantially improved CH-47C. CH-47B was powered by two Lycoming T55-L-7C 2,850 shp (2,130 kW) engines. It featured a blunted rear rotor pylon, redesigned asymmetrical rotor blades, and strakes along the rear ramp and fuselage to improve flying characteristics. It could be equipped with two door-mounted M60D 7.62 mm NATO machine guns on the M24 armament subsystem and a ramp-mounted M60D using the M41 armament subsystem. Some CH-47 "bombers" were equipped to drop tear gas or napalm from the rear cargo ramp onto NLF (aka Việt Cộng) bunkers. The CH-47 could be equipped with a hoist and cargo hook. The Chinook proved especially valuable in "Pipe Smoke" aircraft recovery missions. The "Hook" recovered about 12,000 aircraft valued at over $3.6 billion during the war. 108 built.

CH-47C

The CH-47C featured more powerful engines and transmissions. Three versions of the "C model" were built. The first had Lycoming T55-L-7C engines delivering 2,850 shp (2,130 kW). The "Super C" included Lycoming T55-L-11 engines delivering 3,750 shp (2,800 kW), an upgraded maximum gross weight of 46,000 lb (21,000 kg) and a pitch stability augmentation system (PSAS). Due to difficulties with the T55-L-11 engines, which were hurriedly brought to war to increase payload, they were temporarily removed from the "Super C" prior to 1970 and the very reliable Lycoming T55-L-7C's were installed until the L-11 engine difficulties could be quantified and corrected. This L-7C engine configuration was affectionately referred to as the "baby C" although it was still a Super C. It distinguished itself from the "C" in that it had PSAS and an uprated maximum gross weight. The CH-47 A, B, and all variants of the C were not able to receive certification from the FAA for civil use due to the non-redundant hydraulic flight boost system drive. A redesign of the hydraulic boost system drive was incorporated in the CH-47D which allowed that model to achieve FAA certification as the Boeing Model 234. 233 CH-47Cs were built.

The CH-47A, B, and all versions of the C saw wide use during the Vietnam war. They replaced the H-21 Shawnee in the combat assault support role.

CH-47D

The CH-47D model was originally powered by two T55-L-712 engines, but most are now fitted with the T55-GA-714A. Models CH-47A, CH-47B, and CH-47C, all used the same airframe, but later models featured upgraded engines. With its triple-hook cargo system, the CH-47D can carry heavy payloads internally and up to 26,000 pounds (for example, bulldozers and 40-foot / 12 m containers) externally, at speeds over 155 mph (250 km/h). The aircraft's top cruising speed is 163 mph (142 knots). The D-model was first introduced into service in 1979. In air assault operations, it often serves as the principal mover of the 155 mm M198 howitzer, 30 rounds of ammunition, and an 11-man crew. Like most US Army helicopters, the Chinook has advanced avionics and electronics, including the Global Positioning System. Nearly all of the Army production CH-47D models were conversions from previous US Army A, B, and C models with a total of 472 converted into D-models. The last US Army D-model built was delivered to the US Army Reserve, located at Fort Hood, Texas, in early 2002. In 2008, Canada purchased 6 CH-47Ds for use with the Canadian Helicopter Force Afghanistan from the United States for $252 million. The helicopters were transferred to the Canadian Forces on 30 December 2008.

MH-47D

The MH-47D variant was developed for special forces operations and has in-flight refueling capability, a fast-rope rappelling system and other upgrades. The MH-47D was used by US Army 160th Special Operations Aviation Regiment. 12 MH-47D helicopters were produced. 6 were conversions from CH-47A models and 6 were conversions from CH-47C models.

MH-47E

The current model used by US Army Special Operations is the MH-47E. Beginning with the E model prototype manufactured in 1991, there were a total of 26 Special Operations Aircraft produced. All aircraft were assigned to 2–160th SOAR(A) "Nightstalkers", home based at Fort Campbell Kentucky. E models were conversions from existing CH-47C model airframes. The MH-47E has similar capabilities as the MH-47D, but includes an increased fuel capacity similar to the CH-47SD and terrain following/terrain avoidance radar. In 1995, the Royal Air Force ordered eight Chinook HC3s, effectively a low cost version of the MH-47E for the special forces operations role. They were delivered in 2001 but never entered operational service due to technical issues with their avionics fit, unique to the HC3. In 2008, work started to downgrade the HC3s to HC2 standard, to enable them to enter service.

CH-47F

The CH-47F, an upgraded D model, first flew in 2001. The first production model was rolled out on 15 June 2006 at the Boeing facility in Ridley Park, Pennsylvania, and had its maiden flight on October 23, 2006. The CH-47F was designed to extend the service life of the Chinook class beyond 2030. Among its upgrades are new 4,868 shaft horsepower Honeywell engines, improved avionics, and an upgraded airframe with larger single-piece sections to reduce part count and need for fasteners. The new milled construction will reduce vibrations, eliminate points of joint flexing, and reduce the need for inspections and repairs, and reduce maintenance costs. It is also expected to increase service life. The CH-47F can fly at speeds of over 175 mph (282 km/h) with a payload of more than 21,000 lb (9,530 kg). The improved avionics include a Rockwell Collins Common Avionics Architecture System (CAAS) cockpit, and BAE Systems' Digital Advanced Flight Control System (DAFCS).

Boeing has delivered 48 F-model helicopters to the United States Army; on 26 August 2008, Boeing announced that the Army has signed a five-year contract, worth over $4.8 billion for 191 more, plus 24 options. In February 2007, the Netherlands were the first international customer to order the F model; six helicopters were ordered to expand their current fleet to 17. These helicopters will be equipped with an upgraded version of the Honeywell Avionics Control Management System (ACMS) cockpit. The Netherland also plans to upgrade its current 11 CH-47Ds to the CH-47F configuration. On 10 August 2009, Canada signed a contract to purchase 15 CH-47Fs for delivery in 2013–14, entering service with the Royal Canadian Air Force, after its planned withdrawal from combat operations in Afghanistan, at Canadian Forces Base Petawawa. On 15 December 2009, the British government announced its Future Helicopter Strategy including the purchase of 24 new CH-47F Chinooks to be delivered from 2012. Australia ordered seven CH-47Fs in March 2010. These aircraft are to replace the Australian Army's six CH-47Ds between 2014 and 2017.

MH-47G

The MH-47G Special Operations Aviation (SOA) version is currently being delivered to the US Army. It is similar to the MH-47E, but features a more sophisticated avionics including a digital Common Avionics Architecture System (CAAS). The CAAS is common glass cockpit used by different helicopters such as MH-60K/Ls, CH-53E/Ks, and ARH-70As. The MH-47G will also incorporate all of the new sections of the CH-47F. Based on operational experience in Afghanistan, the CH-47 was found to be an effective substitute for the UH-60 Black Hawk as an assault helicopter. With its larger payload, range, and higher operating speed, one Chinook can replace up to five UH-60s in this role as an air assault transport. The new modernization program will improve MH-47D and MH-47E Special Operations Chinooks to the MH-47G design specs. A total of 25 MH-47E and 11 MH-47D aircraft were upgraded by the end of 2003. In 2002 the army announced plans to expand the Special Operations Aviation Regiment. The expansion would add 12 additional MH-47G helicopters. On February 10, 2011, Leaders and employees from the H-47 program gathered for a ceremony at Boeing's helicopter facility in Ridley Township, PA., to commemorate the delivery of the final MH-47G Chinook to U.S. Army Special Operations Command.

CH-47J

The CH-47J is a medium-transport helicopter for the Japan Ground Self-Defense Force (JGSDF), and the Japan Air Self-Defense Force (JASDF). The differences between the CH-47J and the CH-47D are the engine, rotor brake and avionics. To use it by the general transportation, SAR and disaster activity like U.S. forces. The CH-47JA, introduced in 1993, is a long range version of the CH-47J, fitted with enlarged fuel tank, an AAQ-16 FLIR in a turret under the nose, and a partial glass cockpit. Both versions are built under license in Japan by Kawasaki Heavy Industries, who produced 61 aircraft by April 2001.

The Japan Defense Agency ordered 54 aircraft of which 39 were for the JGSDF and 15 were for the JASDF. Boeing supplied flyable aircraft, to which Kawasaki added full avionics, interior, and final paint. The CH-47J model Chinook (N7425H) made its first flight in January 1986, and it was sent to Kawasaki in April. Boeing began delivering five CH-47J kits in September 1985 for assembly at Kawasaki.

HH-47

On 9 November 2006, the HH-47, a new variant of the Chinook based on the MH-47G, was selected by the US Air Force as the winner of the Combat Search and Rescue (CSAR-X) competition. Four development HH-47s were to be built, with the first of 141 production aircraft planned to enter service in 2012. However, in February 2007 the contract award was protested and the GAO ordered the CSAR-X project to be re-bid. In February 2010, the US Air Force announced plans to replace aging HH-60G helicopters. The Air Force is deferring secondary combat search and rescue requirements that called for a larger helicopter.

Other export models

The Royal Air Force variant of the CH-47C is known as the Chinook HC1. The export version of the CH-47C Chinook for the Italian Army was designated "CH-47C Plus".

The HH-47D is a search and rescue version for the Republic of Korea Air Force. The CH-47DG is an upgraded version of the CH-47C for Greece.

The Royal Air Force versions of the CH-47D are known as the Chinook HC2 and HC2A. While the CH-47SD (also known as the "Super D") is a modified variant of the CH-47D, with extended range fuel tanks and higher payload carrying capacity; the CH-47SD is currently in use by the Republic of Singapore Air Force, Hellenic Army and the Republic of China Army.

Eight CH-47C Chinooks were delivered to the Canadian Forces in 1974. These Chinooks were in Canadian service until 1991, with the designation CH-147. These aircraft were subsequently sold to the Netherlands and are now operated by the Royal Netherlands Air Force as CH-47Ds. Additional orders are expected from Italy. Plans are to upgrade the current fleet of CH-47Ds to the F-model standard and eventually enlarge the fleet to 20 aircraft, pending funding.

Civilian model

Model 234LR (long range): Commercial transport helicopter. The Model 234LR can be fitted out as an all-passenger, all-cargo, or cargo/passenger transport helicopter.

Model 234ER (extended range): Commercial transport version.

Model MLR (multi-purpose long range): Commercial transport version.

Model 234UT (utility transport): Utility transport helicopter.

Model 414: The Model 414 is the international export version of the CH-47D. It is also known as the CH-47D International Chinook.

Derivatives

In 1969, work on the experimental Model 347 was begun. It was a CH-47A with a lengthened fuselage, four-blade rotors, detachable wings mounted on top of the fuselage and other changes. It first flew on 27 May 1970 and was evaluated for a few years. In 1973, the Army contracted Boeing to design a "Heavy Lift Helicopter" (HLH), designated XCH-62A. It appeared to be a scaled-up CH-47 without a conventional body, in a configuration similar to the S-64 Skycrane (CH-54 Tarhe), but the project was canceled in 1975. The program was restarted for test flights in the 1980s and was again not funded by Congress. The scaled up model of the HLH was scrapped at the end of 2005 at Fort Rucker, Alabama.

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