Stability Characteristics for Transport Aircraft Response to Clear-Air Turbulence

Abstract

The clear-air turbulence is difficult to detect and predict and yet affects the flight safety the most. A transport aircraft in encountering a severe turbulence frequently develops a sudden plunging motion with the abrupt change in altitude. The aerodynamic forces and moments involved are dynamic and nonlinear and are not well known. The main objective in the present paper is to present the dynamic and nonlinear aerodynamics estimated with the flight data recorder data of a transport aircraft through a fuzzy-logic algorithm. The algorithm is utilized to establish a thrust model and aerodynamic models for all aerodynamic coefficients including the effects of turbulence. The static and dynamic stability derivatives for the subject transport aircraft are demonstrated to be highly nonlinear and unsteady in response to a severe clear-air turbulence in transonic flight.