K-225

XHTK-1 modified with a Boeing 502 (YT50) turboshaft engine
Role	Experimental helicopter Type of aircraft
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]

Variants

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.

Specifications (K-225)

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)

References

Notes

^ "Hall of Fame/Inventor Profile: Charles Kaman"
^ Boeing Model 502 Gas Turbine Engine Archived 2011-06-22 at the Wayback Machine
^ "Turkish Kaman 225".
^ ^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.
^ Eckland, K.O. (2009-03-07). "American Airplane Ka-Ku". usa: Aerofiles.com. Retrieved 8 May 2012.
^ Kaman K-225, Smithsonian National Air and Space Museum, cit. 28. 1. 2013

Bibliography

"Hall of Fame/Inventor Profile: Charles Kaman". National Inventors Hall of Fame. Archived from the original on 2009-01-06. Retrieved 2009-01-27.

v t e Kaman aircraft
Company designations	K-16 K-17 K-20 K-125 K-190 K-225 K-240 K-600 K-700 K-1125 K-1200 K-Max KSA-100
Military designations	HOK/HTK/HUK H-22 H-43 HU2K/UH-2/HH-2/SH-2 SH-2G Q-24

United States helicopter designations, Army/Air Force and Tri-Service systems

Numerical sequence used by USAAC/USAAF/USAF 1941–present; U.S. Army 1948–1956 and 1962–present; U.S. Navy 1962–present

Army/Air Force sequence
(1941–1962)

Prefix R-, 1941–1948	R-1 R-2 R-3 R-4 R-5 R-6 R-7 R-8 R-9 R-10 R-11 R-12 R-13 R-14 R-15 R-16
Prefix H-, 1948–1962	H-5 H-6 H-9 H-10 H-11 H-12 H-13 J H-15 H-16 H-17 H-18 H-19 H-20 H-21 H-22 H-23 H-24 H-25 H-26 H-27 H-28 H-29 H-30 H-31 H-32 H-33 H-34 H-35 H-36¹ H-37 H-38¹ H-39 H-40 H-41 H-42 H-43 H-44¹ H-45¹

Tri-service sequence
(1962–present)

1962 redesignations	H-13 F J H-19 H-21 H-23 H-25 H-34 H-37 H-43
New designations	H-46 H-47 H-48 H-49 H-50 H-51 H-52 H-53 CH-53/E/K HH-53/MH-53 H-54 H-55 H-56 H-57 H-58 H-59 H-60 UH-60 SH-60 HH-60 MH-60 H-61 H-62 H-63 H-64 H-65 H-66 H-67 H-68 H-69¹ H-70 H-71 H-72 H-73
Alternate sequence	H-1 AH-1/J/T/W/Z UH-1/N/Y H-2 G H-3 CH-3/HH-3 SH-3 H-4 H-5 H-6 AH-6 MH-6 OH-6
Non-sequential	H-90 H-92 CH-92/VH-92 H-139

¹ Not assigned