This NACA 64-215 modified airfoil was used in the Quiet Flow Facility at NASA Langley Research Center for a series of risk reduction experiments. The experiments enlightened researchers on techniques for flow visualization and acoustic measurements using conventional microphones. The model contained surface static pressure ports in order that preliminary flow field tests could be performed. Several flow trips strips were applied (as indicated in the photograph by the yellow serrated strip) to the wing and flap elements. The trip strips allowed for attached flow on the model surface. As a result oil flow techniques were developed. The series of risk reduction experiments proved vital to later airfoil testing in the QFF. Three models (model #1, model #2, Model #3) were designed as a direct result of lessons learned from the Risk Reduction Model. Model #3 is currently being tested in the laboratory in an attempt to provide researchers with information about a key noise source during approach as identified by Boeing.
