In the late 1950s, Vertol Aircraft began developing two tandem-rotor helicopters, the Model 107/YHC-1A and Model 114/YHC-1B. The smaller -1A became the US Marine Corps' CH-46 Sea Knight assault transport the larger -1B was selected by the US Army and became the CH-47 Chinook heavylift helicopter.

 CHinook CH-47D
 ©US Army

Boeing acquired Vertol in 1960, and builds the Chinook at its plant near Philadelphia. The CH-47F is the fourth major model to be produced since the prototype YHC-1B flew in September 1961. Each introduced more powerful engines, improved systems and increased performance.

Deliveries of the original CH-47A began in 1962, and it made its combat debut in Vietnam in 1965. The CH-47B followed in 1967 and the CH-47C in 1968. In the 1970s, the US Army began to remanufacture almost 500 A, B and C models to CH-47D standard. Deliveries began in 1982.

With its composite rotor blades, upgraded systems and uprated engines, the CH-47D and its derivatives make up the bulk of today's Chinook fleet. Almost 400 US Army D models are to be remanufactured to the CH-47F standard, and Boeing expects production of new and "renew" Chinooks to keep the line rolling into its seventh decade.

Source: Flight International