The CH-47 Chinook traces its roots back to the late 1950s, when the Vertol Aircraft Corporation began developing a new tandem-rotor helicopter known as the Model 107 (V-107). Around the same time, the U.S. Army sought to replace its piston-powered Sikorsky CH-37 Mojave with a more powerful turbine-driven design. In 1958, Vertol received an Army contract for a few V-107 helicopters under the YHC-1A designation. Although testing proved the aircraft reliable, the Army concluded that it was too heav