Comparison of Agility Metrics to Beck Agility Metrics Using Linear Error Theory

Abstract

Fighter agility metrics determined from measured or calculated data can be sensitive to the coordinate system used. Although simple and intuitive, agility metrics expressed in Cartesian coordinates are not always robust to variations in initial conditions and uncertainties in physical characteristics. This paper seeks to establish the relationship between form of agility equations and the measured non-poststall agility ofhigh performanceaircraft. Cartesian-coordinate-based agility metrics consisting of the timeto roll through bank angle metric, time-averaged integral of pitch rate metric, and power onset/loss parameter metrics are compared to the Beck metrics, which are based in the Frenet coordinate system. Each metric is evaluated with initial condition errors and parametric uncertainties, and linear error theory is used to determine how linearly the errors propagate. Results presented demonstrate that accuracy of measured agility metrics is directly ine uenced by choice of coordinate system, and recommendations on which coordinate system to use with each agility metric are provided.