Flight Dynamic Analysis of a Turboprop Transport Airplane in Icing Accident

Abstract

Data from the Flight Data Recorder of a turboprop transport airplane involved in an icing mishap are analyzed by modeling the aerodynamic characteristics along the flight path. The analysis results in the prediction of stability and control derivatives along the flight trajectory. Based on these predicted derivatives, the roll excursion that precedes the accident is interpreted as being caused by divergent wing rock mechanisms, having nonlinear unstable dihedral effect and nonlinear unstable roll damping. To monitor the icing accretion conditions, the aerodynamic normal force and pitching moment coefficients in suspected icing conditions are compared with those in normal flight conditions. For this purpose, the typical aerodynamic models for the normal force and pitching moment coefficients in flight conditions without significant icing are established. The aerodynamic coefficients in flight with suspected icing are obtained through compatibility analysis of recorded flight variables, such as the angle of attack and normal acceleration. By comparing these aerodynamic coefficients with the typical model-predicted aerodynamic coefficients based on the flight variables in suspected icing, it is possible to predict approximately when significant icing may start on the wing and/or the horizontal tail. Therefore, the scheme is capable of timely detection of significant ice built-up.