page_title: Glidden Doman
section_title: First employments
hierarchical_section_title: Glidden Doman / First employments
caption_attribution_description: English: Doman LZ-1A (Sikorsky R-6 conversion)
context_page_description: Glidden Doman was an American aeronautical engineer and pioneer in helicopters and modern wind turbines. He founded one of America's original six helicopter companies after making major contributions to the use of Sikorsky helicopters during World War II. Doman Helicopters' most prominent achievement was the Doman LZ-5/YH-31 eight-place helicopter, which received FAA certification on December 30, 1955. The unique feature of this helicopter was its hinge-less but gimbaled, tilting rotor hub that greatly reduced stress and vibration in the blades and in the whole helicopter.
  Doman was one of the first to transfer knowledge of helicopter rotor dynamics technology to wind turbines. The 1973 arab oil embargo prompted NASA Glenn Research Center in Cleveland, Ohio to lead a 7-year US wind energy program for the development of utility-scale horizontal axis wind turbines. This program featured the creation of Boeing's MOD-2 with the Doman conceived flexible rotor design, two-bladed wind turbine with a teeter hinge.
context_section_description: Doman graduated from Michigan in June 1942, just six months after the bombing of Pearl Harbor. After his graduation, he went to work for the Ranger Aircraft Engine Division of Fairchild Aviation in Long Island, New York. Doman had prior experience working with engine technologies while employed during summer vacations at the Franklin Engine Company (where his brother Carl worked). At Ranger, Doman gained experience in using strain gauges to analyze the vibratory loads on the rotating parts of engines.
  Carl Doman, who knew Igor Sikorsky due to the Franklin engine's use in the Sikorsky VS-300, invited Doman to attend a Society of Automotive Engineers meeting in New York. At this event, with Sikorsky as a featured speaker, Doman became interested in the vibratory loads in helicopter rotors. As a new and unrefined invention at that time, helicopters were suffering from rotor blades with a very short fatigue life. In fact, not long after Doman met Sikorsky, a Sikorsky YR-4 had a blade fracture during a delivery flight to the Army, which stimulated Doman's interest all the more.
  In August 1943, Doman married Joan Hamilton and they immediately moved to Stamford, Connecticut where he commuted to and from work for Sikorsky in Bridgeport, CT. Doman put strain gages all over the rotor system of a Sikorsky YR-4 to locate the weak points. He then figured out where and how to change the rotor system to achieve longer blade life. Doman's contributions were so vital that Igor Sikorsky himself appealed to Doman's Draft Board to keep him on the test program instead of sending him into the Army or Navy. Doman discovered that the design of the rotor hub was the real cause of the blade failures. For the duration of World War II, he ran a program to match and balance the blades of all the Sikorsky helicopters before they were delivered. Throughout his tenure at Sikorsky, Doman was continuously learning about rotor dynamics.
  Doman had one very harrowing experience at Sikorsky when he was flying as a test engineer on a YR-4. The pilot had slowed the helicopter to very low speed, and it got into the so-called "vortex ring state" where the blades lose lift and the helicopter thrashes around in an almost uncontrollable fashion. Fatal crashes from such an event have resulted more than once in the history of rotary wing aviation. In this case, however, the pilot somehow got the helicopter flying backwards, which enabled the blades to regain their lifting ability and prevent a crash. While at Sikorsky, Doman got to know Igor Sikorsky, and for years afterwards Doman liked to repeat his favorite quote from Igor Sikorsky, "God takes care of helicopters."
caption: Doman LZ-1A (Sikorsky R-6 conversion)
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