Evaluation of Unmanned Aircraft Flying Qualities Using a Stitched Learjet Model

Abstract

In recent years, military UAVs have taken over missions that were too dull, dirty, or dangerous for manned aircraft. The increased demand has led to a build-fly-fix-fly development mentality, plaguing the early lifecycle with staggering mishap rates. Currently, MIL-STD-1797 lists flying qualities for UAVs as TBD, and the standards for manned fixed wing are inadequate when applied to UAVs. In an effort to expand the database of UAV flying qualities, an analysis was completed on a Simulink model of an LJ-25D developed from Calspans Variable Stability System aircraft at the United States Test Pilot School. Three maneuvers were simulated: (1) a non-precision, non-aggressive climbing spiral, (2) a precision, non-aggressive side step landing, and (3) a precision, non-aggressive aerial refueling task. These maneuvers were chosen to evaluate the performance and workload of the aircraft as four stability and control parameters were scaled. The data were utilized in identifying trends between the scaled stability and control parameters and resulting workload and performance metrics. Thumbprint plots were generated to identify Level 1, Level 2, and Level 3 flying qualities and compared to MIL-STD-1797 plots. Results point to utilizing a combination of classical aircraft literal factors, such as ςsp and CAP, with newly developed mathematical techniques, such as L2 norm and TIC, to assess the workload of the flight controller and performance during the maneuver