The Iroquois was originally designated HU-1, hence the Huey nickname, which has remained in common use, despite the official redesignation to UH-1 in 1962.[2] The UH-1 first saw service in combat operations during the Vietnam War, with around 7,000 helicopters deployed. The Bell 204 and 205 are Iroquois versions developed for the civil market.

In 1952, the U.S. Army identified a requirement for a new helicopter to serve as medical evacuation (MEDEVAC), instrument trainer, and general utility aircraft.

The Army determined that current helicopters were too large, underpowered, or too complex to maintain easily. In November 1953, revised military requirements were submitted to the Department of the Army.[3] Twenty companies submitted designs in their bid for the contract, including Bell Helicopter with the Model 204 and Kaman Aircraft with a turbine-powered version of the H-43. On 23 February 1955, the Army announced its decision, selecting Bell to build three copies of the Model 204 for evaluation with the designation XH-40.[4]

Photo: U.S. Army – http://www.history.army.mil/books/Vietnam/Airmobility/p267.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1111850

While earlier “short-body” Hueys were a success, the Army wanted a version that could carry more troops.

Bell’s solution was to stretch the HU-1B fuselage by 41 in (104 cm) and use the extra space to fit four seats next to the transmission, facing out. Seating capacity increased to 15, including crew.[9] The enlarged cabin could also accommodate six stretchers and a medic, two more than the earlier models.[9] In place of the earlier model’s sliding side doors with a single window, larger doors were fitted which had two windows, plus a small hinged panel with an optional window, providing enhanced access to the cabin. The doors and hinged panels were quickly removable, allowing the Huey to be flown in a “doors off” configuration.

The winner was the UH-1B, which was already in service with the Army. The helicopter was designated the UH-1E and modified to meet Marine requirements. The major changes included the use of all-aluminum construction for corrosion resistance,[N 3] radios compatible with Marine Corps ground frequencies, a rotor brake for shipboard use to stop the rotor quickly on shutdown and a roof-mounted rescue hoist.

Photo: James K. F. Dung, SFC, Photographer – This media is available in the holdings of the National Archives and Records Administration, cataloged under the National Archives Identifier (NAID) 530610. Public Domain, https://commons.wikimedia.org/w/index.php?curid=78487

The Air Force had a large inventory of these engines on hand for its fleet of HH-3 Jolly Green Giant rescue helicopters and using the same engine for both helicopters would save costs. In response, Bell proposed an upgraded version of the 204B with the T58 engine. Because the T58 output shaft is at the rear, and was thus mounted in front of the transmission on the HH-3, it had to have a separate offset gearbox (SDG or speed decreaser gearbox) at the rear, and shafting to couple to the UH-1 transmission.

Photo: Sgt. Robert W. Ingianni – This Image was released by the United States Air Force with the ID 020903-O-9999J-023.This tag does not indicate the copyright status of the attached work. A normal copyright tag is still required. Public Domain, https://commons.wikimedia.org/w/index.php?curid=32416164