The most famous helicopter in the world is the Bell UH-1 Iroquois, commonly known as "Huey". The Huey, which first flew in 1956, served in front line service in the U.S. armed forces and the military of many nations, and will continue for many years to come.
The first helicopters such as Sikorsky R-4 and S-51, were powered by piston engines. In the 1950's, turbine engines are used in many fixed-wing aircraft and helicopter designers began to consider using them for helicopters. The turbines were lighter and provide more power than piston engines, but were more expensive. The first Bell helicopter to use a turbine engine was a modified model of 47 designated XH-13F and moved in October 1954.
In early 1955, the Army awarded Bell a contract to develop the next generation of turbine helicopter medical evacuation, designated XH-40 and then the name of the model 204. The XH-40 first flew on October 22, 1956. Two prototypes were built in 1957, and eighteen more YH-40 service test aircraft in 1958. Bell actively marketed the ship for more than close medical evacuation role, and the plane of the pre-production became so popular among the military who were accustomed to engine piston aircraft that the Army was quick to order even more the ship. The Huey was the first turbine-equipped U.S. helicopter to enter HU-1As production.Production model entered service with the 101st Airborne Division at Fort Lewis, Washington. Although they were intended for evaluation only, the Army quickly put into operational service.
