Parameter Estimation from Flight Data of Hansa-3 Aircraft Using Quasi-Steady Stall Modeling

Nonlinear longitudinal aerodynamics of planar fins and aircraft at high angles of attack near stall have been modeled using Kirchhoff’s formulation. Both the steady-stall and quasi-steady stall models have been applied on the longitudinal aerodynamic data at high angles of attack pertaining to planar fins and Hansa-3 aircraft, respectively. The National Wind Tunnel Facility (NWTF) in the department of Aerospace Engineering at the Indian Institute of Technology, Kanpur was used to generate the wind tunnel data for planar fins with rectangular and NACA-0012 airfoil cross-sections whereas flight test data near stall for Hansa-3 aircraft were generated by executing a quasi-steady stall maneuver (QSSM). The Kirchhoff’s steady-state stall model was applied to wind tunnel data for modeling the flow-separation point and to estimate the parameters characterizing stall. The Kirchhoff’s quasi-steady stall model was applied to the compatible real flight test data to model the nonlinear longitudinal aerodynamics and estimate the aerodynamic parameters. An approach of fixing the parameters to their reasonably accurate values was followed during the estimation of quasi-steady stall characteristics and the longitudinal aerodynamic parameters using the maximum likelihood (ML) method from the nonlinear flight data pertaining to QSSM. The results obtained using both models were found to be encouraging and are presented in graphical as well as in tabular form. The estimated parameters using both models have been compared with the reference results. A well-matched comparison of the model’s estimated and real flight data hysteresis loop is also presented.