Controlling forebody asymmetries in flight - Experience with boundary layer transition strips

LSB The NASA Dryden Flight Research Center has an on-going program to investigate aircraft flight characteristicsat high angles of attack. As part of this investigation, lon-gitudinal boundary layer transition strips were installed onRthe F-18 HARV forebody, a preproduction F/A-18 radomewith a nose-slice tendency, and the X-31 aircraft forebody Redand noseboom to reduce asymmetric yawing moments athigh angles of attack. The transition strips were effectiveon the F-18 HARV at angles of attack above 60 °. On the rpreproduction F/A-18 radome at an angle of attack near50 ° the strips were not effective. When the transition stripswere installed on the X-31 noseboom, a favorable effectwas observed on the yawing moment dynamics but themagnitude of the yawing moments was not decreased. Nomenclature C n Cn o Cno.yawing moment coefficientyawing moment coefficient at zero sideslipyawing moment coefficient due to forebodyat zero sideslipCp pressure coefficientCy side-force coefficientF.S. fuselage stationHARV High Alpha Research VehicleLEX leading-edge extension