American Institute of Aeronautics and Astronautics 092407 1 An Application of Equation Error Method to Aerodynamic Model Identification and Parameter Estimation of a Gliding Flight Vehicle Ümit Kutluay 1 and Dr. Gökmen Mahmutyazıcıoğlu 2 TÜBĐTAK-SAGE, Ankara, 06261, TURKEY and Prof. Dr. Bülent E. Platin 3 Middle East Technical University, Ankara, 06531, TURKEY This paper describes the application of the equation error method to aerodynamic parameter estimation of a gliding flight vehicle. The flight test data used is not originally designed for estimation, causing data collinearity. A strategy is devised to deal with this situation so that the model identification and parameter estimation can be performed. A computer tool is developed in Matlab ® environment for the flight test data processing and aerodynamic identification/estimation. The results of the study show that, although the stepwise regression and equation error method have some potential to be used for flight vehicles other than aircraft, the quality of the flight test data and input design is crucial for aerodynamic parameter identification. Nomenclature AFCS = automatic flight control system b = span C D = drag coefficient C L = lift coefficient C l = rolling moment coefficient C m = pitching moment coefficient Cm q = pitch rate damping stability derivative C n = yawing moment coefficient C X = axial force coefficient C Y = side force coefficient C Z = normal force coefficient d = reference length e = fit error F = F-statistics FTD = flight test data Fv = flight vehicle GFS = global Fourier smoother I = mass moment of inertia J = cost function LS = least squares p = body angular rate about x axis (roll rate) PE = parameter estimation PSD = power spectral density (estimate) 1 Chief Research Engineer, Flight Mechanics Division, ukutluay@sage.tubitak.gov.tr . 2 Assistant Director, Head of Design Engineering Department, gmahmut@sage.tubitak.gov.tr . 3 Faculty Member, Mechanical Engineering Department, platin@metu.edu.tr . AIAA Atmospheric Flight Mechanics Conference 10 - 13 August 2009, Chicago, Illinois AIAA 2009-5724 Copyright © 2009 by TUBITAK-SAGE. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.