Test pilot William R. Murray at the control of Kaman K-225, Bu. No. 125477, with a Boeing 502-2 gas turbine engine installed. (U.S. Navy)
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.
Kaman K-225, Bu. No. 125477, the first gas turbine-powered helicopter, at the Vertical Flight Gallery, Steven F. Udvar-Hazy Center, Smithsonian Institution National Air and Space Museum, Chantilly, Virginia. (NASM)
Captain Chester R. Radcliffe, Jr., United States Air Force (FAI)
5 July 1962: Captain Chester R. Radcliffe, Jr., United States Air Force, flew Kaman HH-43B-KA Huskie 60-0263 from Hill Air Force Base, Utah, to Springfield, Minnesota, a distance of 1,429.80 kilometers (888.44 miles). This established a new Fédération Aéronautique Internationale (FAI) World Record for Distance Without Landing.¹
Captain Chet Radcliffe (right of center, wearing L-2B flight jacket) is congratulated on completion of the flight. The man in the white shirt is Kaman Aircraft Company Chief Test Pilot Francis Andrew Foster. (U.S. Air Force)
This same helicopter, flown by Captain Walter G. McMeen, set an FAI World Record for Altitude with a 1000 kilogram Payload to an altitude of 8,037 meters (26,368 feet) over the Kaman plant at Bloomfield, Connecticut, 25 May 1961.² On 18 October 1961, again at Bloomfield, Lieutenant Colonel Francis M. Carney set a World Record for Altitude Without Payload when he flew 60-0263 to 10,010 meters (32,841 feet).³ The following week, on 24 October 1961, Colonel Carney set six more world records, flying the HH-43B to 3,000 meters (9,853 feet) in 2 minutes, 41.5 seconds;⁴ 6,000 meters (19,685 feet) in 6 minutes 49.3 seconds;⁵ and to 9,000 meters (29,528 feet) in 14 minutes, 31 seconds.⁶ The following summer, Captain Richard H. Coan set an FAI World Record for Distance Over a Closed Circuit Without Landing when he flew 1,055.16 kilometers (655.65 miles) at Mono Lake, California, 13 June 1962.⁷
Kaman HH-43B Huskie 60-263. (FAI)
A turboshaft engine drove a unique system of counter-rotating and intermeshing rotors to provide lift, thrust and directional control. The counter-rotation cancelled the torque effect so no anti-torque, or tail, rotor was necessary. This allowed all of the engine’s power to drive the main rotor system.
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-43B was 25 feet, 2 inches (7.671 meters) long. Each rotor had a diameter of 47 feet, 0 inches (14.326 meters). It’s height was 15 feet, 6½ inches (4.737 meters). The helicopter’s empty weight was 4,470 pounds (2,028 kilograms) and its maximum gross weight was 8,800 pounds (3,992 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 economical cruise speed was 98 miles per hour (158 kilometers per hour), and the maximum speed was 120 miles per hour (193 kilometers per hour). Its hover ceiling out of ground effect (HOGE) was 18,000 feet (5,486 meters), and in ground effect (HIGE) was 20,000 feet (6,096 meters) and it had a range of 235 miles (378 kilometers).
With the call sign Pedro, the HH-43 was a rescue helicopter that served in combat during the Vietnam War.
The record-setting Kaman HH-43B Huskie 60-0263 was last assigned to Detachment 3, 42nd Aerospace Rescue and Recovery Squadron, Kirtland Air Force Base, New Mexico. It is in the collection of the National Museum of the United States Air Force, Wright-Patterson Air Force Base, Ohio. Its distance record still stands.
Kaman HH-43B-KA Huskie 60-0263 at the National Museum of the United States Air Force. (U.S. Air Force)
