Bell UH-1 Iroquois
The Bell UH-1 Iroquois is a utility military helicopter designed and produced by the American aerospace company Bell Helicopter. It is the first member of the prolific Huey family, as well as the first turbine-powered helicopter in service with the United States military.
Development of the Iroquois started in the early 1950s, a major impetus being a requirement issued by the United States Army for a new medical evacuation and utility helicopter. The Bell 204, first flown on 20 October 1956, was warmly received, particularly for the performance of its single turboshaft engine over piston engine–powered counterparts. An initial production contract for 100 HU-1As was issued in March 1960. In response to criticisms over the rotorcraft's power, Bell quickly developed multiple models furnished with more powerful engines; in comparison to the prototype's Lycoming YT53-L-1 engine, producing, by 1966, the Lycoming T53-L-13, capable of, was being installed on some models. A stretched version of the Iroquois, first flown during August 1961, was also produced in response to Army demands for a version that could accommodate more troops. Further modifications would include the use of all-aluminium construction, the adoption of a rotor brake, and alternative powerplants.
The Iroquois was first used in combat operations during the Vietnam War, the first examples being deployed in March 1962. It was used for various purposes, including conducting general support, air assault, cargo transport, aeromedical evacuation, search and rescue, electronic warfare, and ground attack missions. Armed Iroquois gunships carried a variety of weapons, including rockets, grenade launchers, and machine guns, and were often modified in the field to suit specific operations. The United States Air Force deployed its Iroquois to Vietnam, using them to conduct reconnaissance operations, psychological warfare, and other support roles. Other nations' armed air services, such as the Royal Australian Air Force, also dispatched their own Iroquois to Vietnam. In total, around 7,000 Iroquois were deployed in the Vietnam theater, over 3,300 of which were believed to be destroyed. Various other conflicts have seen combat deployments of the Iroquois, such as the Rhodesian Bush War, Falklands War, War in Afghanistan, and the 2007 Lebanon conflict.
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. Various derivatives and developments of the Iroquois were produced. A dedicated attack helicopter, the Bell AH-1 Cobra, was derived from the UH-1, and retained a high degree of commonality. The Bell 204 and 205 are Iroquois versions developed for the civilian market. In response to demands from some customers, a twin-engined model, the UH-1N Twin Huey, was also developed during the late 1960s; a further updated four-bladed model, the Bell 412, entered service in Canada but not the US. A further updated UH-1 with twin engines and four-bladed derivative, the Bell UH-1Y Venom, was also developed during the early twenty-first century for the USMC. In US Army service, the Iroquois was gradually phased out following the introduction of the Sikorsky UH-60 Black Hawk and the Eurocopter UH-72 Lakota in the early 21st century. However, hundreds were still in use more than 50 years following the type's introduction. In excess of 16,000 Iroquois have been built since 1960. With new orders from Japan and the Czech Republic, the UH-1 remains in production. Several export customers, such as Canada, Germany, Taiwan, Japan, and Italy, opted to produce the type under license. Operators have been located across the world, including the Americas, Europe, Asia, Africa, the Middle East, and the Pacific region.
Development
In 1952, the United States Army identified a requirement for a new helicopter to serve as medical evacuation, instrument trainer, and general utility aircraft. The Army determined that current helicopters were too large, underpowered, or too complex to maintain easily. During November 1953, revised military requirements were submitted to the Department of the Army. 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.Model 204
Powered by a prototype Lycoming YT53-L-1 engine producing, the XH-40 first flew on 20 October 1956, at Fort Worth, Texas, with Bell's chief test pilot, Floyd Carlson, at the controls. Even prior to the first flight, the Army had placed an order for six YH-40 service test helicopters. During 1957, a further two prototypes were completed. In 1959, the Army awarded Bell a production contract for 182 aircraft, which was designated "HU-1A" and officially named Iroquois after the Native American nations.The helicopter quickly developed a nickname derived from its HU-1 designation, which came to be pronounced as "Huey". The reference became so popular that Bell began casting the name on the helicopter's anti-torque pedals. The official U.S. Army name was almost never used in practice. Even after September 1962, at which point the designation for all models was changed to UH-1 under a unified Department of Defense designation system, yet the nickname persisted.
While glowing in praise for the helicopter's advances over piston-engined helicopters, the Army reports from the service tests of the YH-40 found it to be underpowered with the production T53-L-1A powerplant producing a maximum continuous 770 shaft horsepower. The Army indicated the need for improved follow-on models even as the first UH-1As were being delivered. In response, Bell proposed the UH-1B, equipped with the Lycoming T53-L-5 engine producing and a longer cabin that could accommodate either seven passengers or four stretchers and a medical attendant. Army testing of the UH-1B started in November 1960, with the first production aircraft delivered in March 1961.
Bell commenced development of the UH-1C in 1960 to correct aerodynamic deficiencies of the armed UH-1B. Bell fitted the UH-1C with a T53-L-11 engine to provide the power needed to lift all weapons systems in use or under development. The Army eventually refitted all UH-1B aircraft with the same engine. A new rotor system was developed for the UH-1C to allow higher air speeds and reduce the incidence of retreating blade stall during diving engagements. The improved rotor resulted in better maneuverability and a slight speed increase. The increased power and a larger diameter rotor required Bell's engineers to design a new tail boom for the UH-1C. The longer tail boom incorporated a wider chord vertical fin on the tail rotor pylon and larger synchronized elevators.
Bell also introduced a dual hydraulic control system for redundancy as well as an improved inlet filter system for the dusty conditions found in southeast Asia. The UH-1C fuel capacity was increased to, and gross weight was raised to, giving a nominal useful load of. UH-1C production started in June 1966 with a total of 766 aircraft produced, including five for the Royal Australian Navy and five for Norway.
Model 205
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 and use the extra space to fit four seats next to the transmission, facing out. Seating capacity increased to 15, including crew. The enlarged cabin could also accommodate six stretchers and a medic, two more than the earlier models. 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 Model 205 prototype flew on 16 August 1961. Seven pre-production/prototype aircraft had been delivered for testing at Edwards AFB starting in March 1961. The 205 was initially equipped with a main rotor and a Lycoming T53-L-9 engine with 1,100 shp. The rotor was lengthened to with a chord of. The tailboom was also lengthened, to accommodate the longer rotor blades. Altogether, the modifications resulted in a gross weight capacity of. The Army ordered production of the 205 in 1963, produced with a T53-L-11 engine for its multi-fuel capability. The prototypes were designated as YUH-1D and the production aircraft was designated as the UH-1D.
During 1966, Bell installed the Lycoming T53-L-13 engine to provide more power for the helicopter. The pitot tube was relocated from the nose to the roof of the cockpit to prevent damage during landing. Production models in this configuration were designated as the UH-1H.
Marine Corps
In 1962, the United States Marine Corps held a competition to choose an assault support helicopter to replace the Cessna O-1 fixed-wing aircraft and the Kaman OH-43D helicopter. 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-aluminium construction for corrosion resistance, 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.The UH-1E was first flown on 7 October 1963, and deliveries commenced on 21 February 1964; a total of 192 Iroquois of this model were completed. Due to production line realities at Bell, the UH-1E was produced in two versions, both with the same UH-1E designation. The first 34 built were essentially UH-1B airframes with the Lycoming T53-L-11 engine producing 1,100 shp. When Bell switched production to the UH-1C, the UH-1E production benefited from the same changes. The Marine Corps later upgraded UH-1E engines to the Lycoming T53-L-13, which produced 1,400 shp, after the Army introduced the UH-1M and upgraded their UH-1C helicopters to the same engine.