Throughout the 1960s, Stanley Hiller continued to produce the OH-23 Raven and experimented with new designs. The U. S. Army used the OH-23 in Vietnam as a light utility scout and as a training aircraft, as did the British Royal Navy and Royal Canadian Air Force. Several commercial operators utilized the helicopters as crop sprayers.
In 1960, Hiller Helicopter merged with Eltra Corporation (Electric Autolite Company) and introduced an improved Model 360, also known as the UH-12E and OH-23E Raven. The new model included an enlarged cockpit layout that placed a single pilot seat in front of a standard three-place passenger bench seat. The company offered retrofits of this modification to existing Hiller aircraft, and several operators took advantage of the opportunity to have their helicopters modified. Hiller also introduced a prototype Model 1099, a square-fuselage utility helicopter offering seating for six or an unobstructed cargo area accessed through a rear-opening door.
In 1961, Hiller submitted the Model 1100 as a contender in the LOH competition. The company delivered five aircraft to be evaluated as the OH-5A. Although Hughes won the contract, Hiller regarded the Model 1100 as too important to abandon and placed it into production for civilian and international military customers.
On May 5, 1964, Fairchild Aircraft acquired Hiller Aircraft and in September changed the corporate name to Fairchild Hiller. The new corporation phased out production of the UH-12 in favor of the new FH-1100. Between 1966 and 1974, Fairchild Hiller produced almost 250 of the machines.
In 1973, Hiller Aviation of Porterville, California, bought the rights to produce the UH-12 and resumed production of the UH- 1E. Soloy Corporation devised a popular secondary market retrofit for the UH-12, the first of which flew on August 9, 1973. The modification included installing a 400-horsepower Allison 250-C20B turboshaft engine in the UH-12 airframe. Soloy converted 180 UH- 12s, as well as some 220 Bell 47s.
Hiller Aviation also acquired the rights to the FH-1100 and prepared to manufacture that helicopter as well, but changes in ownership of the company delayed any significant production. In April 1984, Rogerson Aircraft Corporation acquired the company and, under the name Hiller Helicopters, then Rogerson Hiller, produced five RH-1100B Pegasus between 1983 and 1986. In 1990 the company resumed production of the UH-12E.
In 1959, Rudolph J. Enstrom established the RJ Enstrom Corporation at Menominee County Airport, Michigan, and developed a light, three-seat civilian helicopter. In 1960 a prototype F-28 performed well enough for the company to seek certification of the little helicopter. Enstrom designed the F-28 with a fiberglass-enclosed fuselage and engine compartment that housed a 180-horsepower engine that powered a three-bladed main rotor. Despite some setbacks the F-28 received its FAA certification on April 15, 1965, and customer deliveries began the next January. Enstrom modified the drive ratio of the F-28A to provide more power to the rotor, resulting in several sales to Brazil and the Philippines. Developmental costs precluded Enstrom from fitting a turbine engine to his little helicopter, but he continued to modify and upgrade the F-28A for several years.
In 1989 the U. S. Army announced the Single Contractor Aviation Training (SCAT) program, intended to contract a single provider for Army flight training. Enstrom joined with Link Flight Simulation to construct a turbine-powered helicopter to compete for the fleet of trainers to be supplied by the contract winner. In December 1988, Enstrom had installed an Allison 250B turbine in a 280FX airframe. The resultant helicopter, designated Model 480/TH-28, embodied a reshaped, wider forward fuselage that provided greater headroom and an additional two seats. Bell Helicopter’s TH-58 won the SCAT project, and the TH-28 went without a buyer.
Enstrom, however, placed the civilian Model 480 into production, where it gained a steady flow of orders. The company offered the 480 in a variety of seating arrangements for up to four passengers and a pilot. An unusual staggered seat arrangement provided maximum legroom in the small cabin. Over the years Enstrom changed ownership several times, but the latest partnership continued to market the F-28F, 280FX, and the turbine-powered Model 480.
In 1962, MACV established a Search and Rescue headquarters near Saigon, manned by personnel of the USAF Air Rescue Service, to coordinate SAR operations in SEA. Not until 1964, however, did the first of fourteen USAF detachments flying Kaman HH-43B Husky aircraft arrive in Thailand. The Husky unit immediately began SAR operations, with orders to remain clear of the front lines. With the call sign of “Pedro,” the HH-43 proved very effective on short-radius missions, but the Kaman machines lacked the range for long-distance rescues. In many instances USAF crews resorted to carrying fuel drums aboard on outbound legs and hand pumping the fuel into the helicopter’s tanks before completing their mission. Although the HH-43B set an altitude record of 32,840 feet in October 1961, and the operator’s manual listed a service ceiling of 25,700 feet, the Husky crews experienced great difficulty operating in the mountains of Laos. Weight restrictions prevented the crews from carrying anything but a single M-14 or M-16 rifle for self-protection. Even when upgraded with the more powerful Lycoming T53- L1A 825-horsepower turbine, the HH-43 couldn’t cope with mountainous terrain. Obviously, SAR missions demanded a larger, more powerful helicopter with increased range.
In 1956 the Piasecki Helicopter Corporation became the reorganized Vertol Aircraft Company, and a design team headed by Tom Peppler began work on a new company-funded, twin-engined, tandem rotor “flying banana.” Typical of Piasecki’s earlier designs, the three-bladed main rotors and transmission were mounted atop pylons at the front and rear of the aircraft. The two pilots sat side by side in a cockpit forward of the cargo compartment. The team envisioned the craft as carrying an entire infantry platoon and associated equipment and thus installed the engines on either side of the base of the rear pylon, leaving an uncluttered internal fuselage, with a hydraulic loading ramp at the rear. Aft sponsons contained the main wheels of a fixed tricycle landing gear.
On April 22, 1958, the Model 107 prototype, powered by 877- horsepower Lycoming T53 turbines, took flight for the first time. Three months later the U. S. Army ordered ten evaluation models, with the more powerful General Electric YT58 1,065-horsepower turbine engine and a larger rotor system, designating the aircraft YHC-1A. On August 27, 1959, the YHC-1A made its initial flight. Prior to the delivery of the first YHC-1A, however, the Army had ordered five Vertol YHC-1Bs (Model 114), a larger, more powerful aircraft that better suited the Army’s requirements for a tactical medium-lift transport helicopter. Consequently the Army reduced the order for the Model 107 to only three machines. The Army utilized the aircraft for a short time to familiarize aviators with turbinepowered helicopters, then returned the aircraft to Vertol; one became the prototype for the Model 107-11 civilian version of the helicopter.
In March 1960, Boeing Aircraft Company acquired Vertol and introduced the Boeing/Vertol Model 107M. The aircraft, a modified YHC-1A, won a U. S. Navy competition for a new medium-lift transport helicopter, which resulted in an initial order for fifty of the HRB-1 helicopters. Purchased for the Marines, the first redesignated CH-46 Sea Knight commenced flight testing in October 1962. The main rotor blades folded, and provisions for emergency flotation allowed the Sea Knight to land and take off in light seas and remain afloat for up to two hours. Integral equipment included a rescue hoist, provisions for internal cargo handling, and a hoist capable of hauling 10,000 pounds of external cargo. The CH-46 entered fleet service in November 1964 and was employed as a troop transport/resupply helicopter in Vietnam, where Marine aircrews fitted 7.62-mm machine guns to fire out the cabin doors.
Between 1961 and February 1971, when production of the CH- 46 ended, the Marines ordered more than 600 Sea Knights, with an initial purchase of 160 CH-46As, followed by an additional 266 CH-46Ds with uprated T-58-GE-10 engines and improved rotor blades. The Corps later bought 174 CH-46Fs, basically a “D” model with advanced avionics and electronics. Eventually the Marine Corps converted many of the earlier models to the CH-46E, installing more robust transmissions and rotor heads, composite rotor blades, and (Night Vision Goggles) NVG-compatible cockpits, providing the Marines with an all-weather, day-night assault helicopter. The Navy purchased twenty-four CH-46As and ten CH-46Ds. The USAF ordered a few “B” models for evaluation and the Navy the RH-46E minehunter for the same purpose. The Canadian Air Force ordered eighteen of the machines, designated CH-113, while Sweden bought fourteen aircraft designated HPK-4. Beginning in 1962, New York Airways bought a total of seven of the civilian version of the Sea Knight. As of 2000 the U. S. Navy and Marine Corps operated 291 Sea Knights. In Japan, Kawasaki Heavy Industries also built both civilian and military versions of the Model 107 under license: the KV-107/11-2 commercial passenger version, operated by Kawasaki, the Thai government, and New York Airways; the KV- 107/11-3 minehunters; the KV-107/11-4 tactical transport for Japanese Ground Self-Defense Force; the KV-107/11-5 rescue version for the Japanese Air Self-Defense Force and the Swedish Navy; one KV-107/11-7 VIP transport for the Thai government; and the KV- 107/IIA, modified specifically for hot climates and high altitudes.
On September 21, 1961, the Boeing-Vertol Model 114 lifted off on its maiden flight. The company produced the helicopter as a result of a September 1958 U. S. Army requirement for a medium transport helicopter capable of lifting a 4,500-pound load in all weather. In March 1959 the Army adjudged the modified Boeing- Vertol Model 107 winner of the competition. The Army placed an initial order for five units and classified the helicopter as the CH-47 Chinook. The machine’s fuselage served as a large cargo compartment with the flight deck at the nose of the helicopter and a hydraulically operated ramp located at the rear. The cargo area accommodated forty-four combat-equipped infantrymen, or twenty-four litters plus two medical attendants, or large pieces of equipment or vehicles weighing up to 12,000 pounds. A hole in the forward floor of the cabin allowed items to be hoisted into or lowered from the helicopter. An external cargo hook at the center of the helicopter allowed the Chinook to carry large slingloads, up to 28,000 pounds on current models. Like its predecessors, the CH-47’s design placed the three-bladed, counter-rotating, tandem rotor hubs atop pylons at the fore and aft ends of the aircraft. Each articulated rotor system, with blades composed of steel spars, aluminum honeycomb filler, and a plastic-reinforced fiberglass skin, measured 60 feet in diameter. The 67-horsepower auxiliary power unit (APU), combining transmissions for the turbine engines and all associated driveshafts, was installed on top of the fuselage as well. Fairings along the lower exterior of the helicopter housed large fuel tanks, the battery, and other electronic equipment. The landing gear consisted of four fixed struts, the aft set of paired wheels being steerable on the ground but locked in flight.
The Army settled on the Chinook as its primary medium assault transport helicopter, accepting the first delivery in August 1962, and equipped its airmobile test division, the 11th Airborne, with the CH- 47A. When the airmobile division changed to the 1st Cavalry Division (Airmobile), it received the CH-47B with more powerful T55- L-7C engines. On October 14, 1967, the CH-47C appeared with even more powerful T55-L-11A 3,802-horsepower engines, stronger transmissions, a larger capacity fuel system, and an additional attaching point for external cargo. The next spring the U. S. Army began taking deliveries of the “Super C,” as many soldiers called the upgraded Chinook.
In late 1965, in cooperation with the Boeing Corporation, the U. S. Army commenced testing an armed version of the CH-47 Chinook. Engineers mounted an array of weapons on the aircraft, including an M-5 40-mm automatic grenade launcher in a nose turret controlled and fired by the copilot. Pylons on either side of the helicopter accepted forward-firing weapons including a 20-mm cannon and 19-round 2.75-inch rocket pods. A modified fuselage allowed two doorgunners on each side of the cargo compartment to fire a 7.62-mm or .50-caliber machine gun situated on flexible mounts. An additional gunner position located at the rear loading ramp provided protection after the aircraft had completed its “gun run.” One version of the ACH-47 even carried an experimental 105-mm gun. In addition to more than a ton of expendable ammunition, a ton of steel plating and heavily armored seats protected the aircraft crew and vital aircraft components from ground fire. The Army deployed a company of the armed Chinooks to the RVN, with the call sign of “Guns A-Go-Go,” but the USAF AC-130 proved much more effective; the Army withdrew its armed Chinooks from combat.
In May 1970 the Boeing Corporation flew a company funded experiment with a modified Model 114. For the Model 347 Experimental Advanced-Technology Helicopter prototype, Boeing engineers stretched a CH-47A fuselage with a taller aft pylon, installed four-bladed main rotors, a retractable landing gear, and mounted an unconventional lift wing above the center of the fuselage. The experiment proved unfruitful, with no forthcoming orders for the unusual aircraft.
