Check out this article at RetroMechanix.com on the Stiller helicopter project of 1928:





This was a design conceived by the Stiller brothers of Radom, Poland that was eventually evaluated by NACA, which found the vehicle to be impracticable due to the small rotors and lack of sufficient control surfaces. The accompany gallery reproduces the patent for the design and related correspondence. If any Polish aviation specialists have more information on the project or the subsequent activities of the Stiller brothers, feel free to comment here or at RetroMechanix.com.

-Jared