Wind tunnels have afforded the best potential for studying regions of aerodynamic uniqueness of V/STOL aircraft, but they have been of limited value because of the magnitude of the flow interference they introduce. A new wind tunnel concept is described for covering the spectrum of transition testing from hover throughout wing sustained flight. The wall interference corrections are physically produced by the structure of the wall. A small scale tunnel was designed, constructed, and tested employing this concept. Data from a small rotor model were obtained in the new tunnel and a large conventional one as a basis for comparative evaluation. (Author).