Today in 1951, aerospace engineer Charles H. Kaman’s modified K-225 helicopter took its first test flight in Bloomfield, Connecticut, changing the future of helicopter aviation forever. As the first helicopter to use a jet engine to power its drive shaft, the K-225 demonstrated a way to make helicopters fly faster and higher, with less weight, than ever before.

Born in 1919, Kaman went to work in the propeller division of Hamilton Standard in Windsor Locks in 1940 after graduating with an engineering degree from Catholic University in Washington, D.C. There, Kaman worked alongside vertical aviation pioneer Igor Sikorsky, who was then on the cusp of producing the world’s first mass-manufactured helicopter, and developed his own lifelong interest in rotary-powered flight. A few years later, in 1945, the 26-year-old engineer founded Kaman Aircraft in the garage of his family’s West Hartford home with only a few thousand dollars on hand. Kaman soon moved his modest enterprise to nearby Bloomfield and began building experimental aircraft.

This image of Kaman’s K-MAX cargo helicopter showcases the design of the craft’s twin intermeshed rotors.

Kaman’s helicopter designs looked and operated much differently than Sikorsky’s, with most of them featuring two slightly-angled, intermeshing rotors that eliminated the need for a tail rotor. Within four years after hr founded Kaman Aircraft, Kaman’s first helicopter, the experimental K-125, took flight in Bloomfield. Ever the innovator, he also made a number of improvements to the K-125 and contemplated attaching the rotors to a jet (gas turbine) engine, which would vastly increase the craft’s lift power and stability while decreasing its overall weight. In 1951, Kaman retrofitted one of his model K-225 helicopters with a Boeing engine, and when it took flight above the town of Bloomfield on December 11, it became the world’s first gas turbine-powered helicopter — forever altering the future development of vertical aviation the world over.

The Kaman K-225 helicopter in flight. The Kaman HOK-1, later designated the HH-43 Huskie.

The K-225’s test flight was successful enough to capture the attention of the U.S. Navy, which had sent representatives to observe the December 11 flight at Kaman’s invitation. The K-225 became the forerunner for the closed-cockpit Kaman HH-43 Huskie helicopter, which was used widely by the U.S. Navy and Marines as a utility helicopter through the 1970s. Three years after the groundbreaking 1951 flight, another one of Kaman’s helicopters became the first helicopter to fly powered by two gas turbine engines. Since then, Kaman Aircraft — now known as the Kaman Corporation — has continued to be a major innovator in the worldwide aerospace industry, pioneering notable advances in helicopter design and aerospace parts manufacturing from its Bloomfield headquarters. The future of innovative helicopter engineering was certainly looking up on this day in Connecticut history.

Further Reading

“History of Innovation Timeline,” Kaman Corporation website

Original Kaman K-225 displays at the Smithsonian National Air and Space Museum and the New England Air Museum

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