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  • 1
    Publication Date: 2011-08-19
    Description: This paper presents an application of multiple stepwise regression to the flight test data of a typical transport airplane. The flight test data was carefully preprocessed to eliminate aliasing, time skews and high frequency noise. The data consisted both of basic certification maneuvers, such as wind-up-turns and maneuvers suitable for parameter estimation, such as responses to elevator pulses and doublets. It is shown that the results of multiple stepwise regression techniques compare favorably with the results obtained from maximum likelihood estimation. Finally, it is concluded that multiple stepwise regression could be a fast economical way to estimate transport airplane aerodynamics.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
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  • 2
    Publication Date: 2019-06-27
    Description: A simple vortex system, used to model unsteady aerodynamic effects into the rigid body longitudinal equations of motion of an aircraft, is described. The equations are used in the development of a parameter extraction algorithm. Use of the two parameter-estimation modes, one including and the other omitting unsteady aerodynamic modeling, is discussed as a means of estimating some acceleration derivatives. Computer generated data and flight data, used to demonstrate the use of the parameter-extraction algorithm are studied.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1536 , L-13009
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-27
    Description: An approximate indicial lift function associated with circulation was developed for tapered, swept wings in incompressible flow. The function is derived by representing the wings with a simple vortex system. The results from the derived equations compare well with the limited available results from more rigorous and complex methods. The equations, as derived, are not very convenient for calculating the dynamic response of aircraft, parameter extraction, or for determining frequency-response curves for wings. Therefore, an expression is developed to convert the indicial response function to an exponential form which is more convenient for these purposes.
    Keywords: AERODYNAMICS
    Type: NASA-TP-1241 , L-12110
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  • 4
    Publication Date: 2019-07-13
    Description: The effect of accounting for unsteady aerodynamics on the parameters extracted from flight data is examined. Longitudinal equations of motion have been modified, and a parameter-extraction program developed to include the effects of unsteady aerodynamics. The approach used was to generate pseudo data using the unsteady-aerodynamics model and to use that data in two parameter-extraction programs, one including and the other neglecting unsteady effects to see if the parameters were significantly different. Flight data for a light airplane also was used with the two extraction programs for the same purpose. Results showed that, for the cases considered, including unsteady aerodynamics in the parameter-extraction program did affect the extracted quantities, particularly the damping in pitch. In addition, the parameter variances were lower when unsteady aerodynamics were included in the extraction program than when the effects were neglected.
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 78-1343 , Atmospheric Flight Mechanics Conference; Aug 07, 1978 - Aug 09, 1978; Palo Alto, CA
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  • 5
    Publication Date: 2019-07-13
    Description: This paper investigates the relative importance of including unsteady effects in the lift and downwash in the longitudinal dynamics and parameter extraction algorithm. A simple vortex system has been used to model unsteady aerodynamic effects into the longitudinal equations of motion of an aircraft. Computer-generated data and flight data were used to demonstrate that inclusion of unsteady aerodynamics in the parameter-extraction algorithm produced aerodynamic parameters that were different from those extracted when unsteady aerodynamics were left out of the algorithm. The differences between derivatives associated with the two extraction algorithms (with and without unsteady aerodynamics) were related to acceleration derivatives which usually cannot be extracted individually.
    Keywords: AIRCRAFT STABILITY AND CONTROL
    Type: AIAA PAPER 79-1639 , Atmospheric Flight Mechanics Conference for Future Space Systems; Aug 06, 1979 - Aug 08, 1979; Boulder, CO
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  • 6
    Publication Date: 2019-07-13
    Description: The maximum likelihood method is used for estimation of unknown initial conditions, constant bias and scale factor errors in measured flight data. The model for the system to be identified consists of the airplane six-degree-of-freedom kinematic equations, and the output equations specifying the measured variables. The estimation problem is formulated in a general way and then, for practical use, simplified by ignoring the effect of process noise. The algorithm developed is first applied to computer generated data having different levels of process noise for the demonstration of the robustness of the method. Then the real flight data are analyzed and the results compared with those obtained by the extended Kalman filter algorithm.
    Keywords: NUMERICAL ANALYSIS
    Type: AIAA PAPER 80-1602 , Atmospheric Flight Mechanics Conference; Aug 11, 1980 - Aug 13, 1980; Danvers, MA
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  • 7
    Publication Date: 2019-07-13
    Description: A simplified aerodynamic force model based on the physical principle of Prandtl's lifting line theory and trailing vortex concept has been developed to account for unsteady aerodynamic effects in aircraft dynamics. Longitudinal equations of motion have been modified to include these effects. The presence of convolution integrals in the modified equations of motion led to a frequency domain analysis utilizing Fourier transforms. This reduces the integro-differential equations to relatively simple algebraic equations, thereby reducing computation time significantly. A parameter extraction program based on the maximum likelihood estimation technique is developed in the frequency domain. The extraction algorithm contains a new scheme for obtaining sensitivity functions by using numerical differentiation. The paper concludes with examples using computer generated and real flight data
    Keywords: AERODYNAMICS
    Type: AIAA PAPER 79-0400 , American Institute of Aeronautics and Astronautics, Aerospace Sciences Meeting; Jan 15, 1979 - Jan 17, 1979; New Orleans, LA
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