The Doman LZ-1A is a light experimental helicopter adapted from a Sikorsky design by Doman Helicopters of the United States of America.
The LZ-1A started life as the Sikorsky R6A Hoverfly, but was then modified by Doman into the LZ-1A. The new Doman design first took flight in 1947 after only a year of development.
The main aim of the modification was to design and test new flight performance technology. Doman simplified the rotor head in order to reduce overall flight stresses and improve the control feedback. Tests of the new control system was deemed a success in 1947.
The specific design made use of a hingeless rotor driven by a constant-velocity universal joint. The rotor was also about two feet larger in diameter compared to the Hoverfly.
This design lets the rotor tilt freely relative to the fuselage, but doesn’t put any stress on it. The rotor was so well balanced that serve-less fingertip control was possible This pioneering hingeless design was eventually adopted about 40 years later. Remarkably, during one test flight the aircraft completed 40 minutes of forward flight without the pilot touching the cyclic control.
These modifications did nothing to harm the top speed of the craft either and hovering performance was also significantly improved. Although only one LZ-1A was made, the technology that was developed lives on today.