Nonlinear Aerodynamic Model Extraction from Flight-Test Data for the S-3B Viking

Abstract

Applied procedures for nonlinear aerodynamic model development and extraction from flight data for the S-3B Viking aircraft are addressed. The entire analysis procedure, from dynamic flight-test data management to final blending and validation of the upgraded aerodynamic model, was performed within the integrated data evaluation and analysis system developed by Science Applications International Corporation. A variety of parameter identification (PID) techniques were employed to develop a global, fully nonlinear longitudinal and lateral‐directional aerodynamic model. This effort included total aerodynamic coefficient reconstruction, equation error analysis for initial model structure development, and output error analysis for final model tuning. Data available from S-3B PID flight spanned a Mach range of 0.23‐0.60 which covered an adequate range of angle of attack for both nonlinear longitudinal and lateral‐directional analyses. Regions outside the identified model envelope were described by blending with the original S-3B aerodynamic database to create a full envelope model. Aircraft configurations investigated included cruise, maneuver, takeoff, and landing flap settings as well as retracted and extended landing gear. Standard flight-test maneuvers were flown under each configuration and are described. The available data allowed for the successful extraction of component coefficients for aircraft lift, side force, pitching, rolling, and yawing moments resulting in a simulation with high aerodynamic fidelity.