Boeing CH-47 Chinook: the tandem-rotor heavy lifter

The Boeing CH-47 Chinook is a twin-turbine, tandem-rotor helicopter built by Boeing, originally through its Vertol subsidiary and now by Boeing Defense, Space & Security. Armies use it to move troops, artillery, fuel and other cargo over distances and terrain that smaller helicopters cannot manage, and it has stayed in continuous production since the early 1960s. More than 20 countries fly it today, led by the US Army and the UK’s Royal Air Force, its two largest users¹.

Design and development

The US Army announced in late 1956 that it wanted a turbine-powered helicopter to replace the piston-engine Sikorsky CH-37 Mojave. An initial order for Vertol’s Model 107 proved too heavy for assault work and too light for transport, so the Army ordered an enlarged derivative, the Model 114. That aircraft, then designated YHC-1B, made its first flight on 21 September 1961; it was renamed CH-47A under the new tri-service designation system in 1962 and named for the Chinook people of the Pacific Northwest. Boeing had bought Vertol in 1960, so early aircraft were sold as the Boeing Vertol CH-47 Chinook; deliveries to the US Army began in August 1962¹.

The tandem-rotor layout, with two counter-rotating rotors instead of a tail rotor, lets the Chinook devote nearly all its engine power to lift rather than to cancelling torque, which is why it can carry loads that rival much larger fixed-wing transports. In Vietnam the type proved itself less as a troop carrier than as an artillery mover, placing howitzer batteries in mountain positions no other aircraft could reach and then keeping them supplied with ammunition. Early CH-47As also exposed a weakness: their transmissions could not handle both engines running at full power, and heat and humidity cut maximum lift by more than 20% in the lowlands and 30% in the mountains¹, a problem Boeing addressed with the more powerful CH-47B and CH-47C that followed.

Specifications

The current production model, the CH-47F, is 30.15 m long with its two three-blade rotors turning, each with a diameter of 18.29 m. Its maximum take-off weight is 54,000 lb, about 24,494 kg. Two Honeywell T55-GA-714A turboshaft engines, rated at 4,733 shp each, give it a cruise speed of 157 knots, about 291 km/h, and Boeing says the type can fly at over 175 mph carrying more than 21,000 lb of payload². Standard range is about 400 nautical miles, roughly 741 km, though on a combat mission the practical radius is considerably shorter. A CH-47F crew normally numbers three: pilot, co-pilot and a flight engineer or loadmaster¹.

Variants

Boeing and its partners have built a long line of models. The original CH-47A of 1962 used 2,200 hp Lycoming T55-L-5 engines, with 354 built, followed by the more powerful CH-47B and CH-47C, the latter eventually reaching 3,750 shp. A small batch of CH-47As were converted into ACH-47A gunships armed with 20 mm cannon, machine guns and rocket launchers for Vietnam; three of the four were lost in combat. The CH-47D, introduced into service in 1979, was a near-total rebuild with composite rotor blades, a glass cockpit and modern avionics, mostly converted from earlier airframes, and the MH-47D and MH-47E special-operations versions added aerial refuelling and fast-rope equipment. The current CH-47F, in production since 2006, and the special-operations MH-47G carry a digital Common Avionics Architecture System cockpit, with a Block 2 upgrade from 2020 adding about 20% more engine power. Japan builds its own CH-47J under licence by Kawasaki Heavy Industries, the UK operates a parallel line of Chinook HC marks, and a civil derivative, the Model 234, has flown commercial and offshore work¹.

Operators and service

The CH-47 is in service and in active production, with over 1,200 built as of 2012 and production continuing since. More than 20 countries currently fly the type, with the US Army and the UK Royal Air Force its two largest operators; other users include Japan, Australia, Canada, the Netherlands, Italy, Spain, Saudi Arabia and Singapore, and Germany ordered 60 airframes in June 2022. Iran has kept a sizeable fleet running despite decades of sanctions, with 20 to 45 Chinooks reported operational there as of 2015¹.

Safety record

The Chinook’s long combat history has come with losses. In Vietnam, about 200 of the nearly 750 Chinooks in US and South Vietnamese service were lost to combat or operational accidents. During the 1982 Falklands War, three British Chinooks were destroyed when the transport ship Atlantic Conveyor was hit by an Exocet missile; the one Chinook that had already been unloaded, nicknamed Bravo November, survived and is preserved at the Royal Air Force Museum Cosford. In Afghanistan, a Chinook was shot down near Kabul in June 2005, killing all aboard including a 16-member US special-operations team, and another crashed on 6 August 2011 after reportedly being hit by a rocket-propelled grenade, killing all 38 aboard in the single deadliest incident of the entire Operation Enduring Freedom campaign. Iran, which has flown the type since before its 1979 revolution, lost at least eight CH-47s during the 1980–1988 war with Iraq¹.

Similar aircraft

• Mil Mi-26: a Soviet/Russian heavy-lift helicopter with an even greater payload than the Chinook, though built around a single main rotor rather than Boeing’s tandem layout.
• Sikorsky UH-60 Black Hawk: the US Army’s smaller tactical utility helicopter, used alongside the Chinook for troop movement where the Chinook’s bulk and lift are not needed.