Kaman K-225

The Kaman K‑225 was an early experimental helicopter built by the Kaman Corporation in the United States during the late 1940s and early 1950s. First flown on 15 June 1947, the machine served as a testbed for several groundbreaking technologies that would later become standard in rotary‑wing aircraft. Its most notable feature was the use of the first successful electrically powered rotor control system, employing a pair of synchronous generators and servomechanisms that eliminated the need for a complex mechanical swashplate. The K‑225 also incorporated a rigid‑blade rotor system, which provided greater responsiveness and reduced vibration compared with the flexible blades used on contemporary designs. Powered initially by a 190‑horsepower Lycoming O‑435 engine, later versions were upgraded with a more powerful Pratt and Whitney R‑985 radial engine, demonstrating the airframe’s adaptability. Although only a handful were built, the K‑225’s innovations directly influenced the development of the K‑500 and the modern K‑500/620 series, cementing Kaman’s reputation as a pioneer in helicopter technology. Its legacy endures as a seminal step toward modern fly‑by‑wire and stability‑augmented rotorcraft. The K‑225 remains a milestone that illustrated the potential of electric control in rotorcraft design.