Charles H. Kaman, an innovator in the development and manufacture of helicopter technology and, following a wholly different passion, the inventor of one of the first electrically amplified acoustic guitars, died on Monday in Bloomfield, Conn. He was 91.

Mr. Kaman, who had suffered several strokes over the last decade, died of complications of pneumonia, his daughter, Cathleen Kaman, said. He lived in Bloomfield.

Mr. Kaman (pronounced ka-MAN) was a 26-year-old aeronautical engineer when he founded the Kaman Aircraft Company in 1945 in the garage of his mother’s home in West Hartford, Conn. By the time he retired as chairman in 2001, he had built the Kaman Corporation into a billion-dollar concern that distributes motors, pumps, bearings and other products as well as making helicopters and their parts.

Within the aerospace industry, Mr. Kaman is best known for inventing dual intermeshing helicopter rotors, which move in opposite directions, and for introducing the gas turbine jet engine to helicopters. The company’s HH-43 Huskie was a workhorse in rescue missions in the Vietnam War.