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  • 2000-2004  (8)
  • 1
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    Real-Time Unsteady Loads Measurements Using Hot-Film Sensors (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Several flight-critical aerodynamic problems such as buffet, flutter, stall, and wing rock are strongly affected or caused by abrupt changes in unsteady aerodynamic loads and moments. Advanced sensing and flow diagnostic techniques have made possible simultaneous identification and tracking, in realtime, of the critical surface, viscosity-related aerodynamic phenomena under both steady and unsteady flight conditions. The wind tunnel study reported here correlates surface hot-film measurements of leading edge stagnation point and separation point, with unsteady aerodynamic loads on a NACA 0015 airfoil. Lift predicted from the correlation model matches lift obtained from pressure sensors for an airfoil undergoing harmonic pitchup and pitchdown motions. An analytical model was developed that demonstrates expected stall trends for pitchup and pitchdown motions. This report demonstrates an ability to obtain unsteady aerodynamic loads in real time, which could lead to advances in air vehicle safety, performance, ride-quality, control, and health management.
    Keywords: Aerodynamics
    Type: NASA/TM-2004-212854 , H-2568 , AIAA Applied Aerodynamics Conference and Exhibit; Aug 16, 2004 - Aug 19, 2004; Providence, RI; United States
    Format: application/pdf
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  • 2
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    Flight Investigation of Prescribed Simultaneous Independent Surface Excitations for Real-Time Parameter Identification (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Near real-time stability and control derivative extraction is required to support flight demonstration of Intelligent Flight Control System (IFCS) concepts being developed by NASA, academia, and industry. Traditionally, flight maneuvers would be designed and flown to obtain stability and control derivative estimates using a postflight analysis technique. The goal of the IFCS concept is to be able to modify the control laws in real time for an aircraft that has been damaged in flight. In some IFCS implementations, real-time parameter identification (PID) of the stability and control derivatives of the damaged aircraft is necessary for successfully reconfiguring the control system. This report investigates the usefulness of Prescribed Simultaneous Independent Surface Excitations (PreSISE) to provide data for rapidly obtaining estimates of the stability and control derivatives. Flight test data were analyzed using both equation-error and output-error PID techniques. The equation-error PID technique is known as Fourier Transform Regression (FTR) and is a frequency-domain real-time implementation. Selected results were compared with a time-domain output-error technique. The real-time equation-error technique combined with the PreSISE maneuvers provided excellent derivative estimation in the longitudinal axis. However, the PreSISE maneuvers as presently defined were not adequate for accurate estimation of the lateral-directional derivatives.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212029 , H-2544 , NAS 1.15:212029 , AIAA Atmospheric Flight Mechanics Conference and Exhibit; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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  • 3
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    Real-Time Stability and Control Derivative Extraction From F-15 Flight Data (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A real-time, frequency-domain, equation-error parameter identification (PID) technique was used to estimate stability and control derivatives from flight data. This technique is being studied to support adaptive control system concepts currently being developed by NASA (National Aeronautics and Space Administration), academia, and industry. This report describes the basic real-time algorithm used for this study and implementation issues for onboard usage as part of an indirect-adaptive control system. A confidence measures system for automated evaluation of PID results is discussed. Results calculated using flight data from a modified F-15 aircraft are presented. Test maneuvers included pilot input doublets and automated inputs at several flight conditions. Estimated derivatives are compared to aerodynamic model predictions. Data indicate that the real-time PID used for this study performs well enough to be used for onboard parameter estimation. For suitable test inputs, the parameter estimates converged rapidly to sufficient levels of accuracy. The devised confidence measures used were moderately successful.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212027 , H-2542 , NAS 1.15:212027 , AIAA Atmospheric Flight Mechanics Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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  • 4
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    Initial Flight Tests of the NASA F-15B Propulsion Flight Test Fixture (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flights of the F-15B/Propulsion Flight Test Fixture (PFTF) with a Cone Drag Experiment (CDE) attached have been accomplished at NASA Dryden Flight Research Center. Mounted underneath the fuselage of an F-15B airplane, the PFTF provides volume for experiment systems and attachment points for propulsion experiments. A unique feature of the PFTF is the incorporation of a six-degree-of-freedom force balance. The force balance mounts between the PFTF and experiment and measures three forces and moments. The CDE has been attached to the force balance for envelope expansion flights. This experiment spatially and inertially simulates a large propulsion test article. This report briefly describes the F-15B airplane, the PFTF, and the force balance. A detailed description of the CDE is provided. Force-balance ground testing and stiffness modifications are described. Flight profiles and selected flight data from the envelope expansion flights are provided and discussed, including force-balance data, the internal PFTF thermal and vibration environment, a handling qualities assessment, and performance capabilities of the F-15B airplane with the PFTF installed.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-210736 , NAS 1.15:210736 , H-2507 , 38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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  • 5
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    Real-Time Unsteady Loads Measurements Using Hot-Film Sensors (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Several flight-critical aerodynamic problems such as buffet, flutter, stall, and wing rock are strongly affected or caused by abrupt changes in unsteady aerodynamic loads and moments. Advanced sensing and flow diagnostic techniques have made possible simultaneous identification and tracking, in real-time, of the critical surface, viscosity-related aerodynamic phenomena under both steady and unsteady flight conditions. The wind tunnel study reported here correlates surface hot-film measurements of leading edge stagnation point and separation point, with unsteady aerodynamic loads on a NACA 0015 airfoil. Lift predicted from the correlation model matches lift obtained from pressure sensors for an airfoil undergoing harmonic pitchup and pitchdown motions. An analytical model was developed that demonstrates expected stall trends for pitchup and pitchdown motions. This report demonstrates an ability to obtain unsteady aerodynamic loads in real-time, which could lead to advances in air vehicle safety, performance, ride-quality, control, and health management.
    Keywords: Aerodynamics
    Type: AIAA Applied Aero Conference; Aug 16, 2004 - Aug 19, 2004; Providence, RI; United States
    Format: application/pdf
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  • 6
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    Results From F-18B Stability and Control Parameter Estimation Flight Tests at High Dynamic Pressures (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A maximum-likelihood output-error parameter estimation technique has been used to obtain stability and control derivatives for the NASA F-18B Systems Research Aircraft. This work has been performed to support flight testing of the active aeroelastic wing (AAW) F-18A project. The goal of this research is to obtain baseline F-18 stability and control derivatives that will form the foundation of the aerodynamic model for the AAW aircraft configuration. Flight data have been obtained at Mach numbers between 0.85 and 1.30 and at dynamic pressures ranging between 600 and 1500 lbf/sq ft. At each test condition, longitudinal and lateral-directional doublets have been performed using an automated onboard excitation system. The doublet maneuver consists of a series of single-surface inputs so that individual control-surface motions cannot be correlated with other control-surface motions. Flight test results have shown that several stability and control derivatives are significantly different than prescribed by the F-18B aerodynamic model. This report defines the parameter estimation technique used, presents stability and control derivative results, compares the results with predictions based on the current F-18B aerodynamic model, and shows improvements to the nonlinear simulation using updated derivatives from this research.
    Keywords: Aircraft Stability and Control
    Type: NASA/TP-2000-209033 , H-2424 , NAS 1.60:209033
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  • 7
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    Stability and Control Estimation Flight Test Results for the SR-71 Aircraft With Externally Mounted Experiments (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A maximum-likelihood output-error parameter estimation technique is used to obtain stability and control derivatives for the NASA Dryden Flight Research Center SR-71A airplane and for configurations that include experiments externally mounted to the top of the fuselage. This research is being done as part of the envelope clearance for the new experiment configurations. Flight data are obtained at speeds ranging from Mach 0.4 to Mach 3.0, with an extensive amount of test points at approximately Mach 1.0. Pilot-input pitch and yaw-roll doublets are used to obtain the data. This report defines the parameter estimation technique used, presents stability and control derivative results, and compares the derivatives for the three configurations tested. The experimental configurations studied generally show acceptable stability, control, trim, and handling qualities throughout the Mach regimes tested. The reduction of directional stability for the experimental configurations is the most significant aerodynamic effect measured and identified as a design constraint for future experimental configurations. This report also shows the significant effects of aircraft flexibility on the stability and control derivatives.
    Keywords: Aircraft Stability and Control
    Type: NASA/TP-2002-210718 , H-2465 , NAS 1.60:210718
    Format: application/pdf
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  • 8
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    The SR-71 Test Bed Aircraft: A Facility for High-Speed Flight Research (2000)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The SR-71 test bed aircraft is shown to be a unique platform to flight-test large experiments to supersonic Mach numbers. The test bed hardware mounted on the SR-71 upper fuselage is described. This test bed hardware is composed of a fairing structure called the "canoe" and a large "reflection plane" flat plate for mounting experiments. Total experiment weights, including the canoe and reflection plane, as heavy as 14,500 lb can be mounted on the aircraft and flight-tested to speeds as fast as Mach 3.2 and altitudes as high as 80,000 ft. A brief description of the SR-71 aircraft is given, including details of the structural modifications to the fuselage, modifications to the J58 engines to provide increased thrust, and the addition of a research instrumentation system. Information is presented based on flight data that describes the SR-71 test bed aerodynamics, stability and control, structural and thermal loads, the canoe internal environment, and reflection plane flow quality. Guidelines for designing SR-71 test bed experiments are also provided.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/TP-2000-209023 , NAS 1.60:209023 , H-2405
    Format: application/pdf
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