During the early 1960s, both NATO and Warsaw Pact countries brought into production rotorcraft designed, or initially flown, in the late 1950s. The UH-1 Iroquois came about as a result of Bell Helicopter’s experimentation with turbine-powered helicopters and the U. S. Army’s search for a larger and technically advanced medical evacuation helicopter. In the late 1950s and early 1960s, Bell engineers experimented with several modified Model 47s, including the Model 201, designated the XH-1 by the U. S. military. In 1954, Bell’s engineers installed a 250-horsepower Turbomeca XT51 turbine engine in the experimental XH-1. Continental manufactured the turbine under license, and the craft became Bell’s first turbine-powered helicopter. The Model 201 paved the way for the use of the Lycoming T53 turbine engine in the HU-1.
In order to select a new, turbine-powered helicopter, the Army proposed a competition for a new aircraft to replace the OH-13 in the medical evacuation role. The HU-1, with a longer, wider fuselage, accommodated two litters in a cross-wise configuration, but many at Bell believed the aircraft would ultimately excel as a troop transport and cargo carrier.
Interservice agreements of the time dictated that the Army not conduct the fly-offs of its aircraft. The Air Force or Navy conducted the evaluations according to specifications prepared by the Army. The Air Force selected the Kaman H-43 Husky, a turbine-powered helicopter with twin, intermeshing wooden rotors as competition for the HU-1. The results of the competition evaluations were almost identical, and the Air Force decided to let the secretary of the Army make the decision as to which rotorcraft to buy. The Air Force already utilized the H-43, and increased production would lower the unit cost of each helicopter. Also, Air Force officers believed they might influence the selection politically. Secretary of the Army Wilbur Brucker, after sifting through piles of technical data, asked his staff, “Bell-aren’t they the ones who built that little bubble helicopter that saved so many of our boys in Korea?” When assured that was so, he replied, “I’m going with the company that did something for our boys in Korea,” and on February 23, 1955, he awarded the contract to Bell Helicopter (Brown 1995, 98).
On October 20, 1956, the first of three Model 204 prototypes, designated XH-40 by the military, lifted off on its initial flight. It was powered by a Lycoming XT53-L-1 700-horsepower turboshaft, and Bell engineers fitted the helicopter with a conventional two-bladed main rotor and weighted stabilizer bar. The tailboom extended to a vertical fin that supported a two-bladed tailrotor. Horizontal stabilizers extended from both sides of the tailboom and were linked to the pilot’s cyclic stick to increase controllability in forward flight. Behind the distinctive rounded nose and large windscreen sat the pilot and copilot. Aft of the cockpit, the cargo compartment widened to provide space for six passengers or up to four litters and a medical attendant. The 204 rested on skid gear designed for landings in rough terrain. Unfortunately, Larry Bell died the same day that the 204 lifted off on its maiden flight.
The preproduction YH-40 featured an upgraded T53-L-1A engine derated to 770 horsepower and a cabin lengthened by a foot. On June 30, 1959, the Army accepted the first of nine preproduction 204s, designated HU-1 Iroquois. The “HU,” in military jargon, meant “Helicopter Utility,” from which the HU-1 quickly received its legendary nickname, and the Iroquois would be forevermore known as the “Huey.” As of 2004 more than 16,000 versions of the UH-1 were produced worldwide.
In 1959, Bell pilots flew a HU-1A to Fort Campbell, Kentucky, to demonstrate the new helicopter to officers of the 101st Airborne Division. Army officers told the Bell pilots to remove the litters and see how many combat troops the helicopter would carry. Lifting off with nine troops aboard, the helicopter duly impressed the paratroopers. Following the initial success of the Huey, the Army placed an order for 183 HU-1As, including 14 configured to train pilots to fly in Instrument Meteorological Conditions (IMC). The Army employed the HU-1s in Alaska, Europe, Panama, and Korea as medical evacuation helicopters. When the Army deployed the aircraft to South Vietnam in April 1962, many crews fitted the helicopters with improvised .30-caliber Browning or M-60 doorguns on flexible mounts. The Army also modified one HU-1A and employed it as a test aircraft for future versions of armed helicopters. Bell completed deliveries of the HU-1A in 1961.
In March 1961 the Army accepted the first improved HU-1B helicopter. A lengthened fuselage accommodated seven combat troops, or four stretchers, two sitting casualties, and a medical attendant. A T53-L-5 960-horsepower turboshaft and redesigned 44-foot rotor blades increased cargo capacity to 3,000 pounds. A T53-L-11 1,100- horsepower turboshaft replaced the L-5 in later HU-1Bs. The U. S. Navy borrowed a few of these Hueys from the Army and modified them for anti-submarine warfare (ASW) experimentation, including slinging depth charges under the fuselage. On April 4, 1963, Bell’s commercial 204B received Federal Aviation Administration (FAA) certification, and foreign sales of both military and commercial models commenced. Bell produced at least 1,033 of all versions.
In Japan, Fuji Heavy Industries, which had been producing Bell Model 47s, including its own version the KH-4 since 1952, acquired a contract to produce ninety UH-1B helicopters for the Japanese Ground Self Defense Force (JGSDF). Fuji went on to manufacture fifty-five 204Bs for commercial sales. The Fuji model differed only in that the tailrotor was mounted on the right side instead of the left. In 1973, Fuji introduced the 204B-2 with a Kawasaki- Lycoming KT53-13B 1,400-horsepower engine and larger tailrotor that increased high-altitude performance. Subsequently Fuji also produced 145 UH-1H Hueys for the JGSDF with the Kawasaki- Lycoming KT53-13B 1,400-horsepower turboshaft.
General Hamilton H. Howze, recognized as the intellectual pioneer of U. S. Army aviation in the 1950s and 1960s, altered the employment of helicopters internationally. While director of Army aviation from 1955 to 1958, he initiated new principles of tactical doctrine and organizational structure of aviation units. In 1961, as chairman of the Tactical Mobility Requirements Board, Howze confirmed the necessity for developing airmobile theory and doctrine for Army aviation. The “Howze Board” revolutionized concepts of mobile warfare based on employing organic aviation assets. In 1963, as a result of the Howze Board recommendations, the Army formed the 11th Air Assault Division to test and validate airmobility concepts. The 11th Air Assault Division became the 1st Cavalry Division (Airmobile) prior to deployment overseas; in the next few years, it aptly demonstrated the requisite combined arms structure fundamental to airmobile operations on the modern battlefield.
During the early 1960s the United States began deploying helicopters to the Republic of Vietnam to support that country’s efforts to combat the communist insurrection sponsored by the People’s Republic of North Vietnam. On December 11, 1961, two companies of Piasecki H-21 Shawnees arrived by carrier in South Vietnam. Twelve days after their arrival the helicopters lifted more than 1,000 Army of the Republic of Vietnam (ARVN) paratroopers in the first helicopter combat assault in Vietnam. In April 1962, during Operation Shoofly, the first Marine CH-34Ds flew into South Vietnam. From late 1961 to early 1965, U. S. helicopter crews, expanding their knowledge by trial and error, instructed ARVN commanders in the tactical employment of helicopters. U. S. Army H-21, HU-1A, and Marine Sikorsky H-34 Choctaws, which Marine “grunts” lovingly called “Ugly Angels,” evacuated casualties, supplied isolated garrisons, and provided rapid deployment of units to meet enemy threats. During its service in the RVN, in addition to military missions, U. S. Marine CH-34s also rescued more than 1,500 Vietnamese civilians from flood waters. By the end of 1964 the United States had over 250 helicopters in Vietnam. The success of these helicopter units forced North Vietnam to supply insurgent forces in South Vietnam with modern weapons and to escalate the movement of regular North Vietnamese Army (NVA) troops and supplies into the RVN by the Ho Chi Minh Trail network.
In 1963 the United States began supplying the Vietnamese Air Force (VNAF) with H-34s and upgraded utility and transport helicopters as newer types became available. VNAF pilots received training by U. S. advisors on the same tactics and procedures implemented by U. S. forces. U. S. requirements for helicopters precluded VNAF units from acquiring enough aircraft to institute independent airmobile operations to any large degree.
In September 1962 a triservice agreement by the U. S. military standardized the designations of all U. S. military helicopters. The HU-1 became UH-1 meaning “utility helicopter.” “CH” defined cargo helicopters, “OH” observation, and “AH” designated attack helicopters.
Initially, tactical heliborne transportation received little artillery or tactical air support, and U. S. advisors in South Vietnam soon realized that they needed additional firepower to conduct airmobile operations. In September 1962 fifteen Bell UH-1B Iroquois (“Hueys”), fitted with the XM-6E3 armament system, arrived at Tan Son Nhut, South Vietnam. The armament system included four M- 60 machine guns mounted in pairs on outriggers outboard of the cargo doors, and a 7-round 2.75-inch (70-mm) Folding Fin Aerial Rocket (FFAR) rocket pod affixed to each side of the aircraft. The pilot aimed the machine guns with a sight connected to a hydraulic actuator that flexed the guns 70 degrees to the left and right. The U. S. Navy also flew a few UH-1B gunships, nicknamed “Sea Wolves,” in support of riverine operations. The gunships scouted ahead of river patrol boats (PBRs) searching for ambushes and provided fire support for the PBRs in the event of an attack. Helicopters, nevertheless, remained vulnerable to enemy ground fire. During the battle at Ap Bac near Saigon in January 1963, Viet Cong gunners downed four H-21s and one armed Huey. Regardless of losses, however, by experimentation in actual combat, and applying lessons learned by the French in Algeria, U. S. pilots wrote the book on tactical employment of armed helicopters.
The UH-1B, nonetheless, lacked sufficient power to carry a large load of ordinance and stay abreast of the troop transport helicopters. In September 1965, to overcome those limitations, Bell introduced the UH-1C, designed for the gunship role. The “C” model featured an uprated T-53-L-11 engine, larger fuel tanks, and a new rotor system. The “540” rotor system eliminated Bell’s usual stabilizer bar and replaced it with an electro-mechanical system called Stability Control Augmentation System, or SCAS. Bell engineers also lightened the rotor blades and increased their cord to 27 inches, providing more lift, speed, and maneuverability. The military designated a 1969 version of this Huey, modified with a more powerful T-53-L-13 turboshaft derated to 1,400 horsepower, the UH-1M. Bell manufactured about 750 “C” models, most later converted to the “M” version. Eighteen countries bought “B” and “C” models for their military services. The technology utilized in the “C” model became a database for the AH-1 Cobra, a helicopter designed specifically as a heavily armed attack helicopter.
The Army equipped at least three UH-1Ms with the Hughes Corporation’s INFANT (Iroquois Night Fighter and Night Tracker) system, which made use of a low-light-level television (LLLTV) and infrared searchlight to aim the M21 armament subsystem. These “Mike Model” gunships carried the AN/AAQ-5 Forward Looking Infrared (FLIR) fire control system, a component developed for use on the AH-1G SMASH Cobra (Southeast Asia Multi-Sensor Armament Subsystem for Huey Cobra). The AN/AAQ-5 produced a televised thermal image, enabling the crew to detect, identify, and fire on ground targets during day or night operations. The 1st Cavalry Division (Airmobile) evaluated the aircraft from December 1969 to February 1970, but the Air Force AC-130 Specter gunship proved more effective for night operations.
The “B” and “C” Huey gunships came equipped with a variety of armament systems. The XM-3 consisted of two rectangular 24-tube rocket pods and no guns. The XM-16 used the new cylindrical XM- 158 7-tube rocket pods along with the quad M-60 machine guns. The M-5 added a nose turret mounting an M-75 40-mm automatic grenade launcher with a rate of fire of 220 rounds per minute. The XM-21 replaced the XM-16, retaining the XM-158 rocket pods, but included two GE-134 six-barreled 7.62-mm miniguns, each with a rate of fire of 2,000 rounds per minute, instead of the M-60s. Army aviators called a Huey gunship equipped with the XM-3, carrying a total of forty-eight 2.75-inch FFARs, a “Hog,” and a Huey gunship equipped with the M-5 as well, a “Heavy Hog.”
In July 1960 the U. S. Army awarded Bell Helicopter, which became part of the Textron Corporation in mid-1960, a contract for seven prototypes of the YUH-1D, an extended version of the Huey and designated the Model 205 by Bell. The “D” model first flew on August 16, 1961, and went into limited active service in August 1963. A Lycoming T53-L-11 1,100-horsepower turboshaft drove a larger 48-foot rotor, increasing the cargo load to 4,000 pounds and passenger capacity to twelve to fourteen, or six litters and a flight medic. The UH-1D’s larger self-sealing fuel system included provisions for external auxiliary fuel tanks. Two windows in the 205’s cargo doors easily differentiated the aircraft from the single windows of the 204. A pintle-mounted M-60D machine gun in each cargo door became the standard self-defense armament of all Hueys. During the mid to late 1960s the UH-1D became the Army’s primary troop transport and medevac helicopter, while the smaller 204 variants generally performed the gunship role. The Army bought a total of 2,008 UH-1Ds.
In February 1963, Bell Helicopter test pilots flew the first UH-1E, ordered the previous year to provide the U. S. Marine Corps with an assault support helicopter. Like the “B” model, the UH-1E ordered for the Marines had an external rescue hoist, a rotor brake to quickly stop the free-wheeling rotor blades and hold them in place during shipboard stowage, and avionics particular to the Marine Corps mission. In February 1964 the USMC took delivery of the first of 250 UH-1Es. The next year all production “E” models left the Bell factory with the “540” rotor system of the Army “C” model. When the Marines armed some of their Hueys with .30-caliber machine guns and 2.75-inch rockets to escort the vulnerable CH-34s, Marine pilots began complaining about “shoddy” workmanship by Bell employees. When Bell technicians investigated the problems, they discovered that Marine pilots routinely dove in to attack targets at 165 knots, 25 knots above the maximum airspeed recommended for the helicopter, and then violently pulled up to escape ground fire. The Marine pilots simply overstressed the airframe by pulling too many “Gs.” Knowing that the Marine pilots would follow their informal axiom, “Don’t get caught low, slow, and stupid. If you do, you will be dead,” Bell representatives just recommended that maintenance personnel securely tie down the engine cowlings and “keep on doing what they were doing” (Brown 1995, 111).
In June 1963 the U. S. Air Force contracted for a helicopter to perform missile site support duties, ordering the UH-1F. Bell engineers installed a General Electric (GE) T58-GE-3 1,290-horsepower turboshaft in the fuselage of the UH-1B to drive a UH-1D rotor system. On February 20, 1964, the UH-1F lifted off on its initial flight, and deliveries began in September. The USAF purchased a total of 146 UH-1Fs, with several modified as “UH-1P” psychological warfare aircraft, which carried loudspeakers over the jungles of Vietnam in an attempt to persuade Viet Cong and NVA soldiers to surrender. The USAF also bought about twenty “TH-1Fs” to train pilots in instrument flying and rescue hoist techniques.
In Vietnam, U. S. planners divided heliborne combat assault operations, soon called air assaults, into three phases: en route, approach, and landing. Armed helicopters proved most effective during the landing phase-after a few missions, ground fire hits on transport helicopters dropped from 0.011 hits per flying hour to 0.0074 for escorted aircraft. Hits on unescorted helicopters doubled during the same period. Suppressive fire delivered by armed helicopters proved very effective in reducing the amount and effectiveness of enemy fire on transport helicopters.
As a result of initial combat experience, a platoon of five to seven armed helicopters formed an escort for twenty to twenty-five troop-carrying helicopters. As transportation helicopters approached a landing zone (LZ), gunships began racetrack, or similar patterns, on each side of the landing helicopters. The gunship pilots fired rockets and machine guns on enemy concentrations while door-gunners directed suppressive machine gun fire as the armed helicopters broke away from enemy positions.
Military Assistance Command Vietnam (MACV) instituted Eagle Flights that included an armed Huey, piloted by the U. S. aviation commander and carrying the ARVN troop commander. This command and control (C&C) aircraft flew at an altitude above the reach of small arms, while the air mission commander directed seven to ten transport helicopters, dubbed “slicks” because they lacked external gun mounts, toward the LZ. A flight of five gunships escorted the formation to provide fire support for the insertion. A medevac helicopter trailed the formation to extract any casualties. Eagle Flights provided immediate response to targets of opportunity and could easily be melded into one large airmobile operation. Eagle Flights became the basis for airmobile concepts employed by U. S. combat units arriving in Vietnam in 1965.
