XHTK-1 modified with a Boeing 502 (YT50) turboshaft engine
Role Experimental helicopter
National origin United States
Manufacturer Kaman Aircraft
First flight 15 January 1947 (K-125)
Status Retired
Primary users United States Navy
United States Coast Guard
Number built 7

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.

Design and development

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]


The fifth K-225 to be built displayed at the New England Air Museum, Windsor Locks, Connecticut, in June 2005
first two-seat prototype with 125 hp (93 kW) Lycoming O-390-3 engine and moulded plywood fuselage and bubble canopy.
improved prototype with 190 hp (140 kW) Lycoming engine, certified in April 1949
open frame three-seat helicopter, powered by a 175 hp (130 kW) Lycoming O-435-C engine. Type certified on April 15, 1949.[4]
four-seat version.
improved model, powered by a 225 hp (168 kW) Lycoming O-435-A2 engine, certified on September 16, 1949.[4]
designation for K-225 with Boeing T50-BO-2 model 502 engine.
United States Air Force designation for one K-225 bought for evaluation.

Specifications (K-225)

3-view line drawing of the Kaman K-225
3-view line drawing of the Kaman K-225

Data from [5][6]

General characteristics


See also

Related development

Aircraft of comparable role, configuration, and era



  1. ^ "Hall of Fame/Inventor Profile: Charles Kaman"
  2. ^ Boeing Model 502 Gas Turbine Engine Archived 2011-06-22 at the Wayback Machine
  3. ^ "Turkish Kaman 225".
  4. ^ a b Federal Aviation Administration (September 26, 1950). "Helicopter Specification No. 1H1" (PDF). faa.gov. Archived (PDF) from the original on April 19, 2021. Retrieved September 2, 2022.
  5. ^ Eckland, K.O. (2009-03-07). "American Airplane Ka-Ku". usa: Aerofiles.com. Retrieved 8 May 2012.
  6. ^ Kaman K-225, Smithsonian National Air and Space Museum, cit. 28. 1. 2013