In August and September 1965 elements of the 1st Cavalry Division (Airmobile), the first such division in the world, began to arrive at An Khe. The division’s organization radically differed from that of a standard infantry division. The 1st Cavalry contained 434 helicopters, divided into two battalions of assault helicopters, a battalion of attack helicopters, a battalion of assault support helicopters, an Aerial Rocket Artillery (ARA) battalion (the first such battalion in the Army), and an air cavalry squadron. The division’s capabilities included inserting one-third of its combat power at a time into terrain inaccessible to normal infantry vehicles. To support the large number of aircraft in the division, an Aviation Maintenance Battalion augmented normal Division Support Command. In June 1968 the 101st Airborne Division, deployed to RVN in 1965, received a change of organization and became the second airmobile division in the U. S. Army.
In September 1967 the first of a more powerful line of Hueys rolled out of Bell’s Hurst, Texas, manufacturing facility. Continually seeking to improve the UH-1’s performance in the hot, humid environment of Vietnam, Bell installed the more powerful T53-L-13 engine in the new helicopter. Unfortunately, the aircraft’s transmission limited the engine to 1,400 horsepower. The new Huey measured 57 feet, 10 inches overall, with a 48-foot rotor diameter. With a maximum gross weight of 9,500 pounds, the aircraft reached a top speed of 120 knots, a service ceiling of 12,600 feet, and a maximum range of 280 nautical miles. It was designed to carry up to ten troops in Vietnam’s density altitudes (the combination of humidity and pressure altitude), as well as two M-60 doorguns, armor for the crew, critical engine components, and a fuel system designed to prevent postcrash fires; that, however, reduced the aircraft loading (ACL) to six to eight combat loaded infantrymen. Conversely, a confirmed report stated that a single Huey lifted twenty-five troops out of a hot LZ. The Huey gained a reputation as a rugged, dependable helicopter, more than once returning to base with a hole in the rotor blades large enough for a pilot to stick his head through.
Increased power made the “H Model” a more effective medevac, or “Dustoff,” helicopter. The universal sobriquet Dustoff for medevacs came from the U. S. Army 5th Medical Detachment call sign, selected by Medal of Honor winner Major Charles L. Kelly. Kelly earned great respect for his perseverance and cool demeanor under fire. When told to leave a hot LZ because of heavy enemy fire, Kelly calmly responded over the radio, “When I have your wounded.”
The Army modified 220 UH-1H to UH-1V medevac aircraft, which included a rescue hoist and a bullet-shaped “jungle penetrator” device designed to lift casualties from the triple canopy jungle of Vietnam. Capable of carrying six litters, the medevac versions also included advanced avionics and navigation systems for night and inclement weather operations. Unarmed Dustoff helicopters experienced a loss rate of about three times that of other helicopters in Vietnam; the red crosses painted on the sides and nose of the Hueys probably made better targets for the NVA and VC gunners. The USAF also bought thirty similar HH-1Hs for short-range search and rescue (SAR).
Part of the weight problem with Hueys in Vietnam related to the manner in which Army pilots flew the aircraft. Although engine instruments indicated normal operations, they seemed to produce less and less power. Pilots routinely landed in flooded rice paddies, which allowed about 100 pounds of water and silt to seep in under the cabin floor. The water drained out, but after inspections some Hueys had as much as 300 pounds of dirt and silt trapped under the cargo deck.
The UH-1H remained in production for more than twenty years. The U. S. Army purchased a total of 3,573 UH-1Hs, with many remaining in service in 2004, mainly with Army Reserve/National Guard units. State-of-the-industry avionics, improved composite rotor blades, chaff-flare dispensers, and infrared countermeasures equipment maintained the Huey’s viability. The Army also modified three UH-1Hs as EH-1H “Quick Fix” aircraft, designed to jam or intercept enemy radio transmissions. Excluding those manufactured under foreign license, Bell produced 1,372 UH-1Hs for export sales.
In 1965, Bell, utilizing company funds, experimented with a twin-engine Model 208 “Twin Delta” prototype, which was a UH-1D fitted with a Continental XT67-T-1 module. In this modification two T72-T-2 turboshafts drove a single transmission, turning Bell’s standard semirigid, two-bladed main rotor system. In 1968, Bell, the Canadian government, and Pratt & Whitney Canada (PWC) opened negotiations that led to an agreement in 1969 to build a twin-engine version of the Model 205. In 1969, Bell modified a UH-1D with a new PWC “Twin Pac” containing two PWC PT6 turbines linked to a common reduction transmission. This prototype led to the production of the Model 212, or UH-1N “Twin Huey,” essentially a UH-1H modified with the PWC T400-CP-400 Twin Pac, producing 1,530 horsepower. Each PT6T-3 was capable of 900 horsepower, but the combined 1,800 horsepower overwhelmed the 48-foot, 2-inch rotor system. In the event of an engine failure, however, the transmission allowed the remaining operational engine to deliver its full 900 horsepower to the rotor system. The second engine also increased the machine’s maximum gross weight to 10,000 pounds and increased airspeed by about 10 knots. In 1970, Bell delivered the first of seventy-nine UH-1Ns to the USAF, which used the helicopters for special operations and SAR. By 1978 the U. S. Navy and Marine Corps accepted 221 UH-1Ns, which particularly suited both services’ mission requirements because of the greater overwater flight safety provided by the twin-engine configuration. The Marine Corps converted two standard UH-1Ns to “VH-1N” VIP transports and then ordered six more production models of this version.
On May 3, 1971, the Canadian Armed Forces, which had funded much of the development of the 212/UH-1N, received the initial shipment of fifty aircraft ordered. Within a year Bell completed the contract. The CAF originally designated the helicopter the CUH-1N but later changed the designation to CH-135. The enhanced safety provided by the twin-engined 212 proved to be an excellent selling point for commercial operators working in offshore gas and oil exploration, resulting in sales to several commercial operators, in addition to foreign military services. Bell and its licensees produced more than 1,000 models of the 212.
In 1952 the Hughes Tool Company began experimenting with rotorcraft. Following the tradition of Howard Hughes’s “Spruce Goose,” the XH-17 “Flying Crane” was powered by two GE turbines that turned a huge two-bladed main rotor system measuring 133 feet, 10 inches in diameter. The aircraft stood 30 feet tall on four long legs designed to straddle large cargo. Company records indicated that the large machine could lift off at a gross weight of 40,900 pounds, but, like the Spruce Goose, the company built only one of the aircraft; it flew only once, in October 1952. The company continued experimentation with helicopters, and in 1956 it concluded Hughes’s first contract to provide the U. S. military with a helicopter. The Army designated the Model 200/300, the TH-55 Osage, and bought a total of 792 of the small two-place machines as a primary helicopter trainer. Much smaller than the company’s previous endeavors, this craft had a rotor diameter of 26 feet, 10 inches and a total length of 30 feet, 10 inches. A single Lycoming HIO-360 190-horsepower piston engine drove the transmission and tailrotor through a series of four belts. With a maximum gross weight of 2,050 pounds the machine reached a top speed of only 80 mph, but it laid the groundwork for the very successful Hughes 369.
Hughes continued to produce the Model 269/300 for several years, but in November 1983 it subcontracted all Model 300 production to Schweizer Aircraft Company in Elmira, New York, and the company purchased all rights to the 269/300 series in November 1986. Schweizer produced several specialized variants of the little helicopter, including agricultural versions, and the “Sky Knight,” with a 420-horsepower Allison 250-C20 turboshaft for police duties, and the TH 300C dual-control version for foreign military services. Turkey, New Zealand, Norway, Liberia, Hungary, Japan, and Argentina all utilized variants of the Model 269/300. In 1990, Schweizer Aircraft also proposed a turbine-powered Model 300 to replace the Army’s TH-55.
In the early 1960s, the U. S. Army began a search for a turbinepowered Light Observation Helicopter (LOH) to replace the pistonengined Bell OH-13s. Several companies provided bids for the prototype, but Hughes Aircraft won the contract with the Model 369, which became the OH-6 Cayuse. First flown on February 27, 1963, the agile little aircraft with the three-finned tail was soon being called the “Loach” by U. S. soldiers. The unique teardrop-shaped fuselage earned the OH-6 the sobriquet “Flying Egg,” but the shape and internal bulkheads provided an exceptionally crashworthy aircraft, especially after Hughes installed self-sealing, crash-resistant fuel tanks to prevent postcrash fires.
The large Plexiglas windscreen offered the pilot excellent visibility, and the four-bladed fully articulated rotor system provided much more maneuverability than the semirigid rotor of the OH-13. The Allison T63-A-5A 250 turbine produced 317 horsepower, giving the OH-6 more speed, 130 knots, and allowed the aircraft to carry up to five passengers, or 1,000 pounds of internal cargo. In 1966 the OH- 6 set the first of its twenty-three international records by covering 1,923 nautical miles in a single straight-line flight. In 1967 the Loach first appeared in Vietnam performing such duties as command and control, liaison, fire direction, light utility, and reconnaissance. In the air cavalry role, the crew usually consisted of a pilot and observer; the helicopter was fitted with an M-27 7.62-mm minigun system, and the observer was armed with an M-60 machine gun. The Army eventually ordered 1,420 OH-6s, which were delivered between 1966 and 1970.
The OH-6 proved so effective that the Japanese Self-Defense Force let a contract with Kawasaki Heavy Industries to produce a version of the helicopter. KHI built the export version of the OH-6, the Hughes 500M Defender, designated the OH-6J in Japan. KHI produced a later version with a larger five-bladed rotor system designated the OH-6D. The Japanese military purchased 120 OH-6Js and 62 OH-6Ds. Kawasaki also marketed the 369HS and 369D for EMS, police, and agricultural services.
In 1964, to provide battlefield commanders with a fast, heavily armed, technologically advanced, and less vulnerable attack and reconnaissance helicopter, as well as to support airmobile tactics and air cavalry operations in Vietnam, the U. S. Army initiated the Advanced Aerial Fire Support System (AAFSS) Program. Lockheed Aircraft won the competition with the AH-56A Cheyenne, but an immediate conflict erupted between Army procurement and operational officers. Army planners believed the AAFSS, which lay in the future, to be the ultimate solution to all attack helicopter concerns. Operational officers, however, demanded an advanced gunship to deploy to Vietnam immediately. When Colonel George P. Seneff, chief of Army aviation, told General Harold K. Johnson, Army chief of staff, that our “troops are dying in Vietnam now, not in the future,” Johnson decided to purchase an intermediate attack helicopter.
Bell Helicopter’s recent developments placed the company in an ideal position to fill the Army contract for an intermediate attack helicopter. In 1963, Bell produced a prototype Model 207 Sioux attack helicopter, which combined a Model 47J tail assembly with a tandem-seat Plexiglas cockpit. The helicopter incorporated short shoulder-mounted wings and a chin-mounted turret with two machine guns. A single Lycoming 260-horsepower piston engine turned the typical Bell semirigid rotor system. For the new attack design, Bell engineers incorporated the lessons learned with the Model 207, the airframe of the OH-4 Sioux Scout, which had lost the LOH competition to the Hughes OH-6, and the Lycoming T53- L-13 1,400-horsepower engine to produce a new prototype attack helicopter. To the airframe and engine, the engineers added the transmission, “540” rotor system, and weapons technology of the UH-1C gunship to create the Bell Model 209, a helicopter engineered specifically as an attack helicopter. On its maiden flight in September 1965, the 209 demonstrated an airspeed of 170 knots, almost twice that of the UH-1B and Cs.
In March 1966 the Department of Defense (DoD) contracted to buy 1,100 of the new helicopters, designated the AH-1 Cobra by the U. S. military. The Cobra differed radically in appearance from previous Bell designs. The pilot and copilot/gunner sat in an armored step-seating tandem cockpit, the gunner in front and the pilot in the rear. The thin 38-inch-wide fuselage and jet fighter-type canopy offered the crew excellent visibility and reduced the aircraft’s frontal silhouette to enemy gunners. Stub wings and a nose-mounted chin turret provided hard points for a variety of weapons systems. Fixed skids replaced the retractable landing gear of the first Model 209.
