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"
A CH-47F practicing the Pinnacle manoeuvre whereby soldiers are deposited without
the helicopter ever landing.
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 re designated 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 drive shafts. 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.
A CH-47 in a training exercise with US Navy Special Warfare, in July 2008 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, digitised 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, and a company in the United Kingdom.
2x Lycoming T55-GA-712 turboshaft, 3,750 hp (2,796 kW) each
Length: 98 ft 10 in (30.1 m), Rotor diameter: 60 ft 0 in (18.3 m), Height: 18 ft
11 in (5.7 m), Disc area: 5,600 ft2 (2,800 ft2 per rotor disc) (260 m2)
Empty weight: 23,400 lb (10,185 kg) Loaded weight: 26,680 lb (12,100 kg), Max takeoff
weight: 50,000 lb (22,680 kg)
Maximum speed: 170 knots (196 mph, 315 km/h), Service ceiling: 18,500 ft (5,640 m)
Up to 3 pintle mounted, medium machine guns (1 on loading ramp and 2 at shoulder
windows), generally 7.62 mm (0.308 in) M240/FN MAG machine guns.
Operators: Australia, Canada, Egypt, Greece, Iran, Italy, Japan, Libya, Morocco,
Netherlands, Republic of China (Taiwan), Singapore, South Korea, Spain, Thailand,
United Kingdom, United Arab Emirates, United States, Vietnam