EFFECT OF LIFT-TO-DRAG RATIO IN PILOT RATING OF THE HL-20 LANDING TASK

A man-in-the-loop simulation study of the handling qualities of the HL -20 lifting-body vehicle was made in a fixed-base simulation cockpit a t NASA Langley Research Center. The purpose of the study was to identi fy and substantiate opportunities for improving the original design of the vehicle from a handling qualities and landing performance perspec tive. Using preliminary wind-tunnel data, a subsonic aerodynamic model of the HL-20 was developed. This model was adequate to simulate the l ast 75-90 s of the approach and landing. A simple flight-control syste m was designed and implemented. Using this aerodynamic model as a base line, visual approaches and landings were made at several vehicle lift -to-drag ratios. Pilots rated the handling characteristics of each con figuration using a conventional numerical pilot-rating scale. Results from the study showed a high degree of correlation between the lift-to -drag ratio and pilot rating. Level 1 pilot ratings were obtained when the L/D ratio was approximately 3.8 or higher.