Neil A. Armstrong Flight Research Center

About: Neil A. Armstrong Flight Research Center is a facility organization based out in Rosamond, California, United States. It is known for research contribution in the topics: Flight test & Flight simulator. The organization has 940 authors who have published 1547 publications receiving 17669 citations.

Active Aeroelastic Wing Flight Research Program: Technical Program and Model Analytical Development

Abstract: The Active Aeroelastic Wing (AAW) Flight Research Program's (Pendleton, E., Griffin, K., Kehoe, M., and Perry, B., A Flight Research Program for Active Aeroelastic Wing Technology, AIAA Paper 96-1574, April 1996 and Pendleton, E., Bessette, D., Field, P., Miller, G., and Griffin, K., The Active Aeroelastic Wing Flight Research Program, AIAA Paper 98-1972, April 1998) technical content is presented and analytical model development is summarized. Goals of the AAW flight research program are to demonstrate, in full scale, key AAW parameters and to measure the aerodynamic, structural, and flight control characteristics associated with AAW. Design guidance, derived from the results of this benchmark flight program, will be provided for implementation on future aircraft designs.

Two Reconfigurable Flight-Control Design Methods: Robust Servomechanism and Control Allocation

Abstract: Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method feasible. These methods have been applied to reconfigurable entry flight control design for the X-33 vehicle. Examples presented demonstrate simultaneous tracking of angle-of-attack and roll angle commands during failures of the fight body flap actuator. Although simulations demonstrate success of the first method in most cases, the control-allocation method appears to provide uniformly better performance in all cases.

Application of parameter estimation to aircraft stability and control: The output-error approach

Abstract: The practical application of parameter estimation methodology to the problem of estimating aircraft stability and control derivatives from flight test data is examined. The primary purpose of the document is to present a comprehensive and unified picture of the entire parameter estimation process and its integration into a flight test program. The document concentrates on the output-error method to provide a focus for detailed examination and to allow us to give specific examples of situations that have arisen. The document first derives the aircraft equations of motion in a form suitable for application to estimation of stability and control derivatives. It then discusses the issues that arise in adapting the equations to the limitations of analysis programs, using a specific program for an example. The roles and issues relating to mass distribution data, preflight predictions, maneuver design, flight scheduling, instrumentation sensors, data acquisition systems, and data processing are then addressed. Finally, the document discusses evaluation and the use of the analysis results.

Unsteady aerodynamic modeling for arbitrary motions

Abstract: A study is presented on the unsteady aerodynamic loads due to arbitrary motions of a thin wing and their adaptation for the calculation of response and true stability of aeroelastic modes. In an Appendix, the use of Laplace transform techniques and the generalized Theodorsen function for two-dimensional incompressible flow is reviewed. New applications of the same approach are shown also to yield airloads valid for quite general small motions. Numerical results are given for the two-dimensional supersonic case. Previously proposed approximate methods, starting from simple harmonic unsteady theory, are evaluated by comparison with exact results obtained by the present approach. The Laplace inversion integral is employed to separate the loads into 'rational' and 'nonrational' parts, of which only the former are involved in aeroelastic stability of the wing. Among other suggestions for further work, it is explained how existing aerodynamic computer programs may be adapted in a fairly straightforward fashion to deal with arbitrary transients.