Extraction of Aerodynamic Parameters for Aircraft at Extreme Flight Conditions,
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION EDWARDS CA DRYDEN FLIGHT RESEARCH CENTER
Pagination or Media Count:
The maximum likelihood estimator has been used to extract stability and control derivatives from flight data for many years. This paper briefly discusses the maximum likelihood estimator and the aircraft equations of motion that the estimator uses. The current strength and limitations associated with obtaining flight-determined aerodynamic coefficients in extreme flight conditions is assessed. The importance of the careful combining of wind tunnel results or calculations and flight results and the thorough evaluation of the mathematical model is emphasized. The basic concepts of minimization and estimation are examined for a simple computed aircraft example, and the cost functions that are to be minimized during estimation are defined and discussed. Graphic representations of the cost functions are given to help illustrate the minimization process.