NOTAR™ (NO TAIL ROTOR) HOVER TESTING USING A SCALE MODEL IN WATER

A 9.49 percent geometrically scaled rotor and fuselage model of the NOTAR™ (No Tail Rotor) demonstrator (OH–6A) was tested in the Hover Test Facility (HTF) at the McDonnell Douglas Research Laboratories. The HTF is a 1000-gallon plexiglass water tank with a flow visualization laser, Laser Doppler Velocimeter, and dye injection system. The purpose of the test was to study the flow interaction at the circulation control tail boom/aft fuselage juncture. Flow control fences had to be installed on the flight demonstrator to control this flow. Direct measurements of the rotor downwash velocity profiles were made using the Laser Doppler Velocimeter. Laser light sheets and white light were used with various combinations of dye and tracer particles to visualize the flow; also, the aft fuselage and tail boom were tufted. Still photography, movies, and video tape were used to record the data. The flow behavior correlated with the full scale flow patterns observed during the flight and whirlstand tests. Several modifications to the baseline OH-6A demonstrator configuration were tested. The addition of a second slot to the tailboom resulted in attached flow without fences.