Derived Angle of Attack and Sideslip Angle Characterization for General Aviation

Abstract

Proper exploitation of derived angle of attack (AOA) and sideslip angle from low-cost attitude heading reference system sensors found in general aviation aircraft is a candidate solution for improving flight safety. This approach uses equations for AOA and sideslip angle that are solved on board in real-time, using state data and information provided by sensors. These equations are a function of vehicle parameters and stability and control derivatives, in addition to the angular displacement and angular rate sensor outputs. This paper characterizes and evaluates the feasibility of derived AOA and sideslip angle for part 23 use cases of pilot displays, envelope protection, and fly-by-wire flight control systems. Standard AOA and sideslip angle equations and sensor models are implemented in a nonlinear six-degree-of-freedom simulation model of the Cessna 172. Piloted simulation inputs are used in a non-real-time Monte Carlo simulation to evaluate the effect of modeling uncertainties and sensor noise on derived AOA and sideslip angle. Results presented in the paper show the allowable bounds on aircraft model parametric uncertainties such as stability and control derivatives, in addition to sensor noise levels, that produce usable derived AOA and sideslip angle values.