The Huey story traces back over four decades. A great advance in helicopter propulsion had come in the 1950s with the adaptation of the gas turbine engine to helicopter flight. The piston-drive engines used in Korea and on the Army's UH-34 utility helicopters in the 1950s and early 1960s had produced only one horsepower for each three pounds of engine weight. New gas turbine engines had a much more favorable efficiency ratio. This permitted the construction of small, low-profile aircraft. One of the most important milestones during this period was the decision to develop the XH-40 Bell Utility Helicopter and to power it with a turbine engine. Although designed as an aerial ambulance, it was recognized even then that this machine might turn out to be the most useful aerial platform ever put in production. In 1955, with an interest in a utility helicopter designed around a turboshaft engine, the Army had the Air Force develop a new helicopter for its use. At that time the Army did...