Wind Tunnel Test on Models of V.T.O. Aircraft: A description of the wind tunnel facility for Y.T.O.L. testing at Warton airfield

A straight through wind tunnel sited outdoors was completed in 1963. A 200 h.p. diesel engine gives 75 ft./sec. in the 18‐ft. square section. Models small enough to avoid serious wall constraint are tested statically with fully simulated lift systems to measure the performance and handling characteristics of V.T.O. aircraft at low forward speeds. Intake and jet flows are induced by ejector pumps which occupy representative positions in the engine bay. Engines and airframe are mounted separately to measure loads on tailored balances, and surfaces are extensively pressure plotted. Thus aerodynamic interferences are isolated, giving the physical back‐ground for the formulation of theoretical treatments and calculation methods, involving jet mixing regions and separated flows. Meanwhile empirical data is available for early design work to develop V.T.O. aircraft with useful payload and range. Configurations which minimize the download due to ground effect tend to develop large downloads during the transition manoeuvre. The worst configurations suffer nearly complete loss of the installed vertical thrust, due to aerodynamic interferences on the airframe. Moderate overloading of a V.T.O. aircraft with poor transition performance results in a long take‐off run.