Flight investigation of an underwing nacelle installation of three variable-flap ejector nozzles

A modified F-106B aircraft with underwing engine nacelles was flight tested to investigate airframe installation effects on ejector nozzles. Nozzle thrust coefficients, boattail drag coefficients, and boundary layer characteristics were obtained for the three nozzles. All the nozzles were geometrically similar and had 15 deg conical boattails with juncture radii of curvature equal to 0.5 maximum nozzle diameter. The effects of boattail location relative to the wing trailing edge and the ejector to primary nozzle exit diameter ratio were investigated. Shortening the length by 0.48 nozzle diameter lowered the transonic boattail drag rise Mach number from 0.97 to 0.95. Decreasing the nozzle exit diameter, which reduced the ejector to primary nozzle exit diameter ratio from 1.30 to 1.18, increased the gross thrust coefficient 4.8 percent.