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 (output), 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.
9 December 1959: At Bloomfield, Connecticut, U.S. Air Force Captain Walter J. Hodgson test pilot and Major William J. Davis flew a Kaman H-43B-KA Huskie, 58-1848, to an altitude of 9,097 meters (29,845.8 feet), setting a Fédération Aéronautique Internationale (FAI) World Record for Altitude Without Payload.¹
Davis and Hodgson were present with the Frederick L. Feinberg Award in 1960, for “demonstrating outstanding skills or achievement,” by the American Helicopter Society.
The Kaman H-43 Huskie was a single-engine helicopter using a unique arrangement of counter-rotating and intermeshing rotors. The two rotors turning in opposite directions counteracted the torque effect, eliminating the need for a anti-torque tail rotor. In helicopters using a tail rotor, as much as 30% of the total engine power is used to drive the tail rotor. By eliminating that requirement, the total engine power could be used to produce lift. The Huskie could lift more weight and climb higher than a similar size helicopter with the same engine.
The Kaman Huskie was designed by German inventor Anton Flettner. He had designed and built the Flettner Fl 282 Kolibri. He was brought to the United States at the end of World War II under Operation Paperclip, and went to work at Kaman Aircraft Corporation, Bloomfield, Connecticut.
The Huskie was used by the U.S. Air Force, U.S. Navy and Marine Corps, primarily for short range rescue operations. It was operated by two pilots and two rescue crewmen.
The fuselage of the H-43 was 25.0 feet (7.62 meters) long. Each rotor had a diameter of 47.0 feet (14.33 meters). The helicopter’s empty weight was 5,900 pounds (2,676 kilograms) and its maximum gross weight was 7,100 pounds (3,221 kilograms).
The H-43B was powered by one Lycoming T53-L-1B turboshaft engine, rated at 860 shaft horsepower at 21,510 r.p.m. The engine uses a 5-stage axial-flow, 1 stage centrifugal-flow, compressor with a single stage gas producer turbine and single-stage power turbine. A reverse-flow combustion section allows significant reduction in the the engine’s total length. The power turbine drives the output shaft through a 3.22:1 gear reduction. The T53-L-1 is 3 feet, 11.8 inches (1.214 meters) long and 1 foot, 11.0 inches (0.584 meters) in diameter. It weighs 460 pounds (209 kilograms).
The Huskie’s maximum speed was 107 miles per hour (172 kilometers per hour). Its hover ceiling in ground effect (HIGE) was 20,000 feet (6,096 meters) and it had a range of 250 miles (402 kilometers).
Kaman H-43B-KA Huskie 58-1848 was reclassified as HH-43B in 1962. It was retired to The Boneyard at Davis-Monthan Air Force Base, Tucson, Arizona, in 1972, and was scrapped in 1977.
8 December 1945: At the Bell Aircraft Corporation Wheatfield Plant, Niagara Falls, New York, the first Model 47 helicopter, NX41962, was rolled out. Designed by Arthur M. Young, the Model 47 was based on Young’s earlier Model 30. The helicopter made its first flight on the same day.
The Civil Aviation Administration (C.A.A.), predecessor of the Federal Aviation Administration, had never certified a helicopter, so Bell worked with government officials to develop civil certification standards. The Bell 47 received the C.A.A. Type Certificate H-1 on 8 March 1946 and the first helicopter’s registration was assigned changed to NC1H.
The Bell 47 series was constructed of a welded tubular steel airframe with a sheet metal cockpit and a characteristic plexiglas bubble. In the original configuration, it had a four-point wheeled landing gear, but this was soon replaced with a tubular skid arrangement. It was a two-place aircraft with dual flight controls.
The first Bell Model 47 had an overall length (with rotors turning) of 39 feet, 7½ inches (12.078 meters). The main rotor diameter was 33 feet, 7 inches (10.236 meters). The length of the fuselage, from the front of the plexiglass bubble canopy to the trailing edge of the tail rotor disc, was 29 feet, 3½ inches (8.928 meters). The tail rotor had a diameter of 5 feet, 5 inches (1.676 meters). The helicopter’s height, to the top of the main rotor mast, was 9 feet, 2-7/16 inches (2.805 meters).
NC1H had an empty weight of 1,393 pounds (632 kilograms). Its gross weight was 2,100 pounds (953 kilograms).
The Bell 47’s main rotor is a two-bladed, under-slung, semi-rigid assembly that would be a characteristic of helicopters built by Bell for decades. The blades were constructed of laminated wood, and covered with fabric. A stabilizer bar was placed below the hub and linked to the flight controls through hydraulic dampers. This made for a very stable aircraft. The main rotor turns counter-clockwise, as seen from above. (The advancing blade is on the right.) The tail rotor is positioned on the right side of the tail boom in a tractor configuration. It rotates counter-clockwise as seen from the helicopter’s left. (The advancing blade is above the axis of rotation.)
Power was supplied by an air-cooled, normally-aspirated, 333.99-cubic-inch-displacement (5.473 liter) Franklin Engine Company 6V4-175-B3 vertically-opposed six cylinder engine, serial number 17008, rated at 178 horsepower at 3,000 r.p.m. Power was sent through a centrifugal clutch to a gear reduction transmission which turned the main rotor through a two-stage planetary gear system. The transmission also drove the tail rotor drive shaft, and through a vee-belt/pulley system, a large fan to provide cooling air for the engine.
The new helicopter had a cruise speed of 75 miles per hour (121 kilometers per hour) and a maximum speed (Vne) of 80 miles per hour (129 kilometers per hour). NC1H had a service ceiling of 11,400 feet (3,475 meters).
The Bell 47 was produced at the plant in New York, and later at Fort Worth, Texas. It was steadily improved and remained in production until 1974. In military service the Model 47 was designated H-13 Sioux, (Army and Air Force), HTL (Navy) and HUG (Coast Guard). The helicopter was produced under license by Agusta, Kawasaki and Westland. More than 7,000 were built worldwide and it is believed that about 10% of thoe remain in service.
In 2010, the type certificates for all Bell 47 models was transferred to Scott’s Helicopter Service, Le Sueur, Minnesota, which continues to manufacture parts and complete helicopters.
After certification testing and demonstrations, NC1H was one of two Bell 47s used for flight training. The first Bell 47, s/n 1, crashed at Niagara Falls Airport, 3 April 1946.
While hovering out of ground effect, a student inadvertently oversped the main rotor. The main rotor hub separated and the helicopter dropped to the ground. Both the student and instructor were injured. Damage to NC1H was extensive and the helicopter was scrapped. The registration, NC1H, was reassigned to Bell 47 s/n 11.
The President of the United States of America, authorized by Act of Congress, March 3, 1863, has awarded in the name of The Congress the Medal of Honor to
MAJOR BRUCE P. CRANDALL UNITED STATES ARMY for conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty:
Rank and Organization: Major, U.S. Army, Company A, 229th Assault Helicopter Battalion, 1st Cavalry Division (Airmobile).
Place and dates: Landing Zone X-Ray, Ia Drang Valley, Republic of Vietnam, 14 November 1965.
Place and date of birth: Olympia, Washington, 1933.
For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty: Major Bruce P. Crandall distinguished himself by extraordinary heroism as a Flight Commander in the Republic of Vietnam, while serving with Company A, 229th Assault Helicopter Battalion, 1st Cavalry Division (Airmobile). On 14 November 1965, his flight of sixteen helicopters was lifting troops for a search and destroy mission from Plei Me, Vietnam, to Landing Zone X-Ray in the Ia Drang Valley. On the fourth troop lift, the airlift began to take enemy fire, and by the time the aircraft had refueled and returned for the next troop lift, the enemy had Landing Zone X-Ray targeted. As Major Crandall and the first eight helicopters landed to discharge troops on his fifth troop lift, his unarmed helicopter came under such intense enemy fire that the ground commander ordered the second flight of eight aircraft to abort their mission. As Major Crandall flew back to Plei Me, his base of operations, he determined that the ground commander of the besieged infantry battalion desperately needed more ammunition. Major Crandall then decided to adjust his base of operations to Artillery Firebase Falcon in order to shorten the flight distance to deliver ammunition and evacuate wounded soldiers. While medical evacuation was not his mission, he immediately sought volunteers and with complete disregard for his own personal safety, led the two aircraft to Landing Zone X-Ray. Despite the fact that the landing zone was still under relentless enemy fire, Major Crandall landed and proceeded to supervise the loading of seriously wounded soldiers aboard his aircraft. Major Crandall’s voluntary decision to land under the most extreme fire instilled in the other pilots the will and spirit to continue to land their own aircraft, and in the ground forces the realization that they would be resupplied and that friendly wounded would be promptly evacuated. This greatly enhanced morale and the will to fight at a critical time. After his first medical evacuation, Major Crandall continued to fly into and out of the landing zone throughout the day and into the evening. That day he completed a total of 22 flights, most under intense enemy fire, retiring from the battlefield only after all possible service had been rendered to the Infantry battalion. His actions provided critical resupply of ammunition and evacuation of the wounded. Major Crandall’s daring acts of bravery and courage in the face of an overwhelming and determined enemy are in keeping with the highest traditions of the military service and reflect great credit upon himself, his unit, and the United States Army.
10 November 1949: At Bloomfield, Connecticut, Dimitry D. (“Jimmy”) Viner, a nephew of Igor Sikorsky and chief test pilot for the Sikorsky Aircraft Corporation, made the first flight of the prototype Sikorsky S-55 helicopter, serial number 55-001, which the U.S. Air Force had designated YH-19 and assigned serial number 49-2012.
Five YH-19 service test aircraft were built. Two were sent to Korea for evaluation in combat. As a result, the United States Air Force placed an initial order for 50 H-19A Chickasaw helicopters. (It is customary for U.S. Air Force and U.S. Army helicopters to be named after Native American individuals or tribes, though there are exceptions.) This was quickly followed by orders for 264 H-19B helicopters.
The United States Navy ordered 118 S-55s which were designated HO4S-1 and HO4S-3. The U.S. Coast Guard bought 30 HO4S-1G and HO4S-3Gs configured for rescue operations. The U.S. Marine Corps purchased 244 HRS-1, HRS-2 and HRS-3 helicopters. The U.S. Army ordered 353 H-19C and H-19D Chickasaw utility transports. The remaining 216 Sikorsky-built helicopters were S-55, S-55C and S-55D commercial models.
The S-55 was flown by two pilots in a cockpit placed above the passenger/cargo compartment. The most significant design feature was moving the engine from directly under the main rotor mast to a position at the front of the helicopter. Installed at an angle, the engine turned a drive shaft to the main transmission. The engine placement provided space for a large passenger/cargo compartment. The aircraft was constructed primarily of aluminum and magnesium, with all-metal main and tail rotor blades.
The main rotor consisted of three fully-articulated blades built of hollow aluminum spars, with aluminum ribs. Spaces within the blade were filled with an aluminum honeycomb. The blades were covered with aluminum sheet. The hollow spars were filled with nitrogen pressurized to 10 p.s.i. An indicator at the blade root would change color if nitrogen was released, giving pilots and mechanics an indication that the spar had developed a crack or was otherwise compromised. The main rotor turned counter-clockwise as seen from above. (The advancing blade is on the helicopter’s right.) Flapping hinges were offset from the main rotor axis, giving greater control response and effectiveness. The tail rotor was mounted on the helicopter’s left side in a pusher configuration. It turned clockwise as seen from the helicopter’s left.
The helicopter’s fuselage was 42 feet, 2 inches (12.852 meters). The main rotor had a diameter of 53 feet (16.154 meters) and tail rotor diameter was 8 feet, 8 inches (2.642 meters), giving the helicopter an overall length with all blades turning of 62 feet, 2 inches (18.948 meters). It was 13 feet, 4 inches (4.064 meters) high. The landing gear tread was 11 feet (3.353 meters). The S-55 had an empty weight of 4,785 pounds (2,173 kilograms) and maximum takeoff weight of 7,200 pounds (3,271 kilograms). Fuel capacity was 185 gallons (698 liters).
The YH-19 was powered by an air-cooled, supercharged 1,343.804-cubic-inch-displacement (22.021 liter) Pratt & Whitney R-1340-57 (Wasp S1H2) 9-cylinder radial engine mounted at a 35° angle in the fuselage forward of the crew compartment. This was a direct-drive engine which had a Normal Power rating of 550 horsepower at 2,200 r.p.m. to 8,000 feet (2,438 meters), and 600 horsepower at 2,250 r.p.m. for Take Off. Later production S-55 commercial and H-19/HO4S and HRS military helicopters used an air-cooled, supercharged 1,301.868-cubic-inch (21.334 liter) Wright Aeronautical Division 871C7BA1 Cyclone 7 (R-1300-3) 7-cylinder radial engine with a compression ratio of 6.2:1. The R-1300-3 was also a direct-drive engine, but was rated at 700 horsepower at 2,400 r.p.m., Normal Power, and 800 horsepower at 2,600 r.p.m. for Take-Off. Both engines incorporated a large cooling fan to circulate air around the cylinders. The R-1300-3 was 49.68 inches (1.261 meters) long, 50.45 inches (1.281 meters) in diameter, and weighed 1,080 pounds (490 kilograms).
The S-55 had a maximum speed of 95 knots (109 miles per hour, 176 kilometers per hour). The helicopter’s hover ceiling in ground effect (HIGE) was 7,875 feet (2,400 meters) and out of ground effect (HOGE) is 4,430 feet (1,350 meters). The service ceiling was 11,400 feet (3,475 meters) and range was 405 miles (652 kilometers).
Sikorsky Aircraft Corporation built 1,281 S-55-series helicopters. Another 477 were built under license by Westland Aircraft Ltd., Société Nationale des Constructions Aéronautiques du Sud-Est (SNCASE) and Mitsubishi Heavy Industries.
49-1012 is in the collection of the Smithsonian Institution National Air and Space Museum.