The Kaman K-225 is an American experimental helicopter developed by Kaman Aircraft. One example was modified to become the world's first gas turbine-powered helicopter.

The K-125 was Charles Kaman's first helicopter, which utilized intermeshing rotors and Kaman's patented servo-flap stability control.^[1] The K-125 first flew on 15 January 1947.

The K-190 and K-225 were an improved versions of the K-125, which first flew in April and July 1949 respectively. The U.S. Navy bought two and the Coast Guard one for $25,000 each. The United States Air Force evaluated one K-225 with the designation YH-22.

A modified K-225 equipped with a Boeing 502 (YT50) turboshaft engine became the first gas turbine-powered helicopter in December 1951.^[2] This aircraft is now at the Smithsonian Institution in Washington, D.C.

A standard K-225 is preserved in the New England Air Museum at Windsor Locks Connecticut.

In 1953, the Turkish Army purchased one Kaman K-225 helicopter and a K-225 was the first helicopter flown in Turkey.^[3]

K-125

first two-seat prototype with 125 hp (93 kW) Lycoming O-390-3 engine and moulded plywood fuselage and bubble canopy.

K-190

improved prototype with 190 hp (140 kW) Lycoming engine, certified in April 1949

K-190A

open frame three-seat helicopter, powered by a 175 hp (130 kW) Lycoming O-435-C engine. Type certified on April 15, 1949.^[4]

K-190B

four-seat version.

K-225

improved model, powered by a 225 hp (168 kW) Lycoming O-435-A2 engine, certified on September 16, 1949.^[4]

K-5

designation for K-225 with Boeing T50-BO-2 model 502 engine.

YH-22

United States Air Force designation for one K-225 bought for evaluation.

Data from ^[5][6]

General characteristics

• Crew: two
• Length: 22 ft 5 in (6.83 m)
• Height: 11 ft 0 in (3.35 m)
• Empty weight: 1,799 lb (816 kg)
• Gross weight: 2,703 lb (1,226 kg)
• Powerplant: 1 × Lycoming O-435-2 6-cyl. air-cooled horizontally opposed piston engine, 225 hp (168 kW)
• Main rotor diameter: 2 × 38 ft 0 in (11.58 m)

Performance

• Maximum speed: 73 mph (117 km/h, 63 kn)

Related development

• Kaman HH-43 Huskie

Aircraft of comparable role, configuration, and era

• Flettner Fl 282