14 January 1942: Chief Test Pilot Charles Lester (“Les”) Morris (1908–1991) made the first flight of the Vought-Sikorsky VS-316A at Stratford, Connecticut. The first flight lasted approximately 3 minutes, and by the end of the day, Morris had made 6 flights totaling 25 minutes duration.
The VS-316A (which was designated XR-4 by the U.S. Army Air Corps and assigned serial number 41-18874), established the single main rotor/anti-torque tail rotor configuration. It was a two-place helicopter with side-by-side seating and dual flight controls.
The fabric-covered three-blade main rotor was 38 feet (11.582 meters) in diameter and turned counter-clockwise as seen from above. (The advancing blade is on the helicopter’s right.) The tail rotor was mounted to the aft end of the tail boom in a tractor configuration, and rotated counter-clockwise when seen from the helicopter’s right side.
The VS-316A was 33 feet, 11.5 inches (10.351 meters) long and 12 feet, 5 inches (3.785 meters) high. It weighed 2,010 pounds (911.7 kilograms) empty and the maximum gross weight was 2,540 pounds (1,152.1 kilograms).
The original engine installed in the VS-316A was an air-cooled, normally-aspirated, 499.805-cubic-inch-displacement (8.190 liter) Warner Aircraft Corporation Scarab SS-50 seven-cylinder radial engine with a compression ratio of 5.55:1. The SS-50 was a direct-drive engine, with a maximum continuous power rating of 109 horsepower at 1,865 r.p.m., and 145 horsepower at 2,050 r.p.m. at Sea Level for takeoff. 73-octane gasoline was required. The SS50 was 2 feet, 5 inches (0.737 meters) long, 3 feet, 0-9/16 inches (0.929 meters) in diameter and weighed 306 pounds (139 kilograms).
Numerous modifications were made, including lengthening the main rotor blades, covering them with metal, and upgrading the engine to a 200 horsepower Warner R-550-1 Super Scarab. The XR-4 was redesignated XR-4C. This would be the world’s first production helicopter. It is at the Steven F. Udvar-Hazy Center of the Smithsonian National Air and Space Museum.
12 January 1962: The first helicopter assault, Operation Chopper, took place when 33 United States Army CH-21C Shawnee transport helicopters of the 8th and 57th Transportation Companies airlifted 1,036 soldiers of the Army of the Republic of Vietnam (ARVN) into battle against an insurgent Việt cộng (National Liberation Front) stronghold, approximately 10 miles (16.1 kilometers) west of Saigon. The landing zone was 150 yards by 300 yards and surrounded by tall trees.
The Piasecki Helicopter Company CH-21C Shawnee was a single-engine, tandem rotor transport helicopter. It had a flight crew of three with one or two gunners, and could carry up to 20 soldiers under ideal conditions.
With rotors turning, the ship’s overall length was 86 feet, 4 inches (26.314 meters) and it was 15 feet, 9 inches (4.801 meters) high. The rotors were 44 feet (13.411 meters) in diameter and the fuselage was 52 feet, 7 inches (16.027 meters) long. The empty weight was 8,950 pounds (4,059.7 kilograms) and maximum takeoff weight was 15,200 pounds (6,894.6 kilograms).
The forward rotor turned counter-clockwise, as seen from above. (The advancing blade is on the helicopter’s right side.) The rear rotor turns the opposite direction. Normal operating speed for the main rotors was approximately 250 r.p.m. The counter-rotating rotors cancelled out engine torque, eliminating any need for a tail rotor.
The H-21 was powered by a single air-cooled, supercharged, 1,823.129-cubic-inch-displacement (29.875 liter) Wright Aeronautical Division Cyclone 9 863C9WD1 (R-1820-103) nine-cylinder radial, mounted inside the fuselage at midship, and drove the front and rear rotors in opposite directions through drive shafts and gear boxes. The Wright R-1820-103 engine was rated at 1,275 horsepower at 2,500 r.p.m., and 1,425 horsepower at 2,700 r.p.m., for takeoff. This direct-drive engine had a compression ratio of 6.80:1 and required 100/130 aviation gasoline. The engine was 4 feet, 0.50 inches (1.232 meters) long, 4 feet, 6.95 inches (1.396 meters) in diameter, and weighed 1,350 pounds (612 kilograms). Wright built 971 R-1820-103s from November 1950 through 1957.
The CH-21C had a maximum speed of 127 miles per hour (204 kilometers per hour) and a range of 265 miles (427 kilometers). It’s service ceiling was 19,200 feet (5,852.2 meters).
The Piasecki H-21 Workhorse was developed for the U.S. Air Force as an air base support and search and rescue helicopter in cold weather operations. A total of 707 were built for the U.S., France and Germany, as well as civil operators. 334 were built for the U.S. Army as the H-21C Shawnee, redesignated CH-21C in 1962.
Its performance in the hot and humid climate of Southeast Asia was limited, restricting the troop load to 9 soldiers. It was withdrawn from service in 1964 when the Bell HU-1A Iroquois began to replace it. All CH-21Cs were retired when the CH-47 Chinook assumed its role in 1965.
10 January 1966: The prototype Bell Model 206A JetRanger serial number 1, N8560F, made its first flight at at the Bell Helicopter Company plant at Hurst, Texas. This aircraft would be in production for almost 45 years. The final JetRanger to be built, Bell 206B-3 serial number 4690, was delivered in December 2010 and production came to an end.
During early production of the Model 206A, cabin sections were built by Beechcraft and Agusta then shipped to Bell at Fort Worth. (The vertical seam just to the rear of the fuel cap distinguished the two.) Oil pressure and temperature gauges for the engine and transmission, the loadmeter and fuel quantity indicator were provided by Cessna.
The Bell JetRanger is a 5-place, single-engine light civil helicopter based on the Bell Helicopter’s unsuccessful OH-4 entrant for the U.S. Army’s Light Observation Helicopter (LOH, or “loach”) contract. It is flown by a single pilot in the right front seat. Dual flight controls can be installed for a second pilot. The helicopter was certified for VFR flight, but could be modified for instrument flight.
The industrial design firm of Charles Wilfred Butler
“. . . was responsible for the complete redesign of the Bell OH-4A prototype army helicopter (1961) into the Bell Jet Ranger (1965). He and his designers restyled the machine inside and out in the manner of automotive design, creating in the process one of the world’s most successful and beautiful helicopters.”
The JetRanger is 38 feet, 9.5 inches (11.824 meters) long, overall. On standard skid landing gear the overall height is 9 feet, 4 inches (2.845 meters). The Bell 206A has an empty weight of approximately 1,700 pounds (771 kilograms), depending on installed equipment. The maximum gross weight is 3,200 pounds (1,451.5 kilograms). With an external load suspended from the cargo hook, the maximum gross weight is increased to 3,350 pounds (1,519.5 kilograms).
The two-bladed main rotor is semi-rigid and under-slung, a common feature of Bell’s main rotor design. It has a diameter of 33 feet, 4.0 inches (10.160 meters) and turns counter-clockwise (seen from above) at 394 r.p.m. (100% NR). (The advancing blade is on the helicopter’s right side.) The rotor blade has a chord of 1 foot, 1.0 inches (0.330 meter) and 10° negative twist. The airfoil is symmetrical. The cyclic and collective pitch controls are hydraulically-boosted.
The two-bladed tail rotor assembly is also semi-rigid and is positioned on the left side of the tail boom in a pusher configuration. It turns at 2,550 r.p.m., clockwise, as seen from the helicopter’s left. (The advancing blade is below the axis of rotation.) The tail rotor diameter is 5 feet, 6.0 inches (1.676 meters).
The turboshaft engine is mounted above the roof of the fuselage, to the rear of the main transmission. Output shafts lead forward to the transmission and aft to the tail rotor 90° gear box. The transmission and rotor mast are mounted tilting slightly forward and to the left. This assists in the helicopter’s lift off to a hover, helps to offset its translating tendency, and keeps the passenger cabin in a near-level attitude during cruise flight.
A vertical fin is attached at the aft end of the tail boom. The fin is offset 4° to the right to unload the tail rotor in cruise flight. Fixed horizontal stabilizers with an inverted asymmetric airfoil are attached to the tail boom. In cruise flight, these provide a downward force that keeps the passenger cabin in a near-level attitude.
The 206A was powered by an Allison 250-C18 turboshaft engine (T63-A-700) which produced a maximum of 317 shaft horsepower at 104% N1, 53,164 r.pm. The improved Model 206B JetRanger and 206B-2 JetRanger II used a 370 horsepower 250–C20 engine, and the Model 206B-3 JetRanger III had 250-C20B, -C20J or -C20R engines installed, rated at 420 shaft horsepower at 105% N1, (53,519 r.p.m.). Many 206As were upgraded to 206Bs and they are sometimes referred to as a “206A/B.” The Allison 250-C20B has a 7-stage compressor section with 6-stage axial-flow stages, and 1 centrifugal-flow stage. The 4-stage axial-flow turbine has a 2-stage gas producer (N1) and 2-stage power turbine (N2). These were very light weight engines, ranging from just 141 to 173 pounds (64.0 to 78.5 kilograms).
The helicopter’s main transmission is limited to a maximum input of 317 shaft horsepower (100% Torque, 5-minute limit). The engine’s accessory gear unit reduces the output shaft speed to 6,016 r.p.m. N2, which is further reduced by the transmission’s planetary gears, and the tail rotor 90° gear box.
The JetRanger has a maximum speed, VNE, of 150 miles per hour (241 kilometers per hour) up to 3,000 feet (914 meters). Its best rate of climb, VY, is at 60 miles per hour (97 kilometers per hour) and best speed in autorotation (minimum rate of descent and maximum distance) is at 80 miles per hour (129 kilometers per hour), resulting in a glide ratio of about 4:1. The service ceiling is 13,500 feet (4,145 meters) with the helicopter’s gross weight above 3,000 pounds (1,361 kilograms), and 20,000 feet (6,096 meters) when below 3,000 pounds. The helicopter has a maximum range of 430 miles (692 kilometers).
After being used as a factory demonstrator and development aircraft, N8560F was retired from flight status and used as a maintenance ground training device at Bell’s training school at Hurst.
Note: The Model 206A-1 was adopted by the U.S. Army as the OH-58A Kiowa. Though very similar in appearance to the Model 206A and 206B, the OH-58A differs significantly. Few of the parts are interchangeable between the types.
During 1966–1967, author John Steinbeck was in Vietnam. He wrote a series of dispatches to Newsday which have recently been published as a book, Steinbeck In Vietnam: Dispatches From the War, edited by Thomas E. Barden. University of Virginia Press, 224 pp., $29.95.
On 7 January 1967, Steinbeck was at Pleiku, where he flew aboard a UH-1 Huey helicopter with D Troop, 1st Squadron, 10th Cavalry. He wrote the following about the helicopter pilots:
“I wish I could tell you about these pilots. They make me sick with envy. They ride their vehicles the way a man controls a fine, well-trained quarter horse. They weave along stream beds, rise like swallows to clear trees, they turn and twist and dip like swifts in the evening. I watch their hands and feet on the controls, the delicacy of the coordination reminds me of the sure and seeming slow hands of (Pablo) Casals on the cello. They are truly musicians’ hands and they play their controls like music and they dance them like ballerinas and they make me jealous because I want so much to do it. Remember your child night dream of perfect flight free and wonderful? It’s like that, and sadly I know I never can. My hands are too old and forgetful to take orders from the command center, which speaks of updrafts and side winds, of drift and shift, or ground fire indicated by a tiny puff or flash, or a hit and all these commands must be obeyed by the musicians hands instantly and automatically. I must take my longing out in admiration and the joy of seeing it. Sorry about that leak of ecstasy, Alicia, but I had to get it out or burst.”
11 December 1951: The first helicopter powered by a gas turbine engine made its first flight at the Kaman Aircraft Company plant at Bloomfield, Connecticut. Using a K-225 tandem rotor helicopter delivered to the U.S. Navy in 1949, Bureau of Aeronautics serial number (“Bu. No.”) 125477, Kaman replaced the 220 horsepower Lycoming O-435-A2 reciprocating engine with a Boeing 502-2E turboshaft engine. This engine could produce 175 continuous horsepower at 2,900 r.p.m. at Sea Level, less than the piston engine it replaced, but it also weighed considerably less.
K-225 Bu. No. 125477 was the first helicopter to perform an intentional loop, when it was delivered to the Navy at NATC Patuxent River by factory test pilot William R. Murray. It was placed in storage at Bradley Field, Windsor Locks, Connecticut until 1957. The gas turbine had been removed. When the helicopter was transferred to the Smithsonian Institution in 1957, a similar-appearing Boeing YT-50-BO-2 gas turbine engine was installed.
The K-225 was a two-place, single-engine helicopter using Kaman’s unique system of counter-rotating, intermeshing rotors (“synchropter”). Each rotor cancelled the torque reaction of the other, eliminating the need for a tail rotor. In a conventional single-rotor helicopter, up to 30% of the engine power is required to drive the tail rotor. With the counter-rotating design, the total engine power is available for lift and thrust.
K-225 Bu. No. 125477 is 22 feet, 5 inches (6.83 meters) long. Each rotor has a diameter of 38 feet (11.58 meters). It stands 11 feet, 6 inches (3.51 meters) high. The helicopter has an empty weight of 1,800 pounds (816 kilograms) and a maximum gross weight of 2,700 pounds (1,225 kilograms). It is a slow helicopter, with a never-exceed (VNE) limit of 70 miles per hour (112.7 kilometers per hour). This historic helicopter is on display at the Smithsonian Institution National Air and Space Museum, Steven F. Udvar-Hazy Center in Chantilly, Virginia.