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  • Aircraft Stability and Control
  • Biochemistry and Biotechnology
  • Cell & Developmental Biology
  • Fisheries
  • General Chemistry
  • 2000-2004  (44)
  • 1945-1949
  • 2003  (44)
Collection
Keywords
Publisher
Years
  • 2000-2004  (44)
  • 1945-1949
Year
  • 1
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    Ecology. Freshwater eels are slip-sliding away (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-10-11
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Stone, Richard -- New York, N.Y. -- Science. 2003 Oct 10;302(5643):221-2.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/14551417" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Ecosystem ; *Eels/growth & development/physiology ; Fisheries ; Fresh Water ; Oceans and Seas ; Population Density ; Reproduction ; Seawater
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 2
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    Ocean exploration. Deep-sea mountaineering (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-08-23
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Malakoff, David -- New York, N.Y. -- Science. 2003 Aug 22;301(5636):1034-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12933987" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Anthozoa ; Atlantic Ocean ; Conservation of Natural Resources ; *Ecosystem ; Environment ; Fisheries ; *Fishes ; Geologic Sediments ; *Marine Biology ; Pacific Ocean ; *Seawater
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Modeling marine protected areas (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-07-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sanchirico, James N -- Stoffle, Richard -- Broad, Kenny -- Talaue-McManus, Liana -- New York, N.Y. -- Science. 2003 Jul 4;301(5629):47-9; author reply 47-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12843376" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; California ; *Conservation of Natural Resources ; *Ecosystem ; Fisheries ; *Fishes ; Humans ; Seawater
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 4
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    Ecology. 'Combat biology' on the Klamath (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-04-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Service, Robert F -- New York, N.Y. -- Science. 2003 Apr 4;300(5616):36-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12677035" target="_blank"〉PubMed〈/a〉
    Keywords: Agriculture ; Animals ; California ; *Conservation of Natural Resources ; *Cypriniformes/physiology ; *Ecology ; Ecosystem ; Environment ; Fisheries ; *Fresh Water ; Government Agencies ; National Academy of Sciences (U.S.) ; *Oncorhynchus kisutch/physiology ; Oregon ; United States ; Water Movements
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 5
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    Conservation biology. Rapid evolution can foil even the best-laid plans (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-05-10
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zimmer, Carl -- New York, N.Y. -- Science. 2003 May 9;300(5621):895.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12738833" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Biological Evolution ; Breeding ; *Conservation of Natural Resources ; Environment ; Fisheries ; *Fishes/genetics/growth & development/physiology ; Plant Development ; Reproduction ; *Selection, Genetic ; Sexual Maturation
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 6
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    Wildlife conservation. U.N. joins Russia's fight to save Western Pacific salmon (2003)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2003-08-30
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Webster, Paul -- New York, N.Y. -- Science. 2003 Aug 29;301(5637):1167.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12947169" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Conservation of Natural Resources/economics ; *Ecosystem ; *Environment ; Financial Support ; Fisheries ; Fresh Water ; Pacific Ocean ; Russia ; *Salmon ; United Nations/economics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 7
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    CFIT Prevention Using Synthetic Vision (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: In commercial aviation, over 30-percent of all fatal accidents worldwide are categorized as Controlled Flight Into Terrain (CFIT) accidents where a fully functioning airplane is inadvertently flown into the ground, water, or an obstacle. An experiment was conducted at NASA Langley Research Center investigating the presentation of a synthetic terrain database scene to the pilot on a Primary Flight Display (PFD). The major hypothesis for the experiment is that a synthetic vision system (SVS) will improve the pilot s ability to detect and avoid a potential CFIT compared to conventional flight instrumentation. All display conditions, including the baseline, contained a Terrain Awareness and Warning System (TAWS) and Vertical Situation Display (VSD) enhanced Navigation Display (ND). Sixteen pilots each flew 22 approach - departure maneuvers in Instrument Meteorological Conditions (IMC) to the terrain challenged Eagle County Regional Airport (EGE) in Colorado. For the final run, the flight guidance cues were altered such that the departure path went into the terrain. All pilots with a SVS enhanced PFD (12 of 16 pilots) noticed and avoided the potential CFIT situation. All of the pilots who flew the anomaly with the baseline display configuration (which included a TAWS and VSD enhanced ND) had a CFIT event.
    Keywords: Aircraft Stability and Control
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  • 8
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    An Overview of the NASA Test Platform Research (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: A methodology for improving attitude stability and control for low-speed and hovering air vehicle is under development. In addition to aerodynamically induced control forces such as vector thrusting, the new approach exploits the use of bias momenta and torque actuators, similar to a class of spacecraft system, for its guidance and control needs. This approach will be validated on a free-flying research platform under development at NASA Langley Research Center. More broadly, this platform also serves as an in-house testbed for research in new technologies aimed at improving guidance and control of a Vertical Take-Off and Landing (VTOL) vehicle.
    Keywords: Aircraft Stability and Control
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  • 9
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    Living with a Star Space Environment Testbed (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: Summary of activities: (1) FYO1 NRA - Model development and data mining. (2) FY03 NRA - Flight investigations. (3) SET carrier development. (4) Study for accommodation of SET carrier to support advanced detectors. (5) Collaboration with other programs: LWS TR&T to maximize synergy between TR&T space environment research and SET space environment effects research. LWS Data System to optimize dissemination of SET data. NASA Electronic Parts and Packaging Program to leverage ground testing of technologies. Defense Threat Reduction Agency to leverage ground testing and common interests in advanced detectors. and Air Force Research Laboratory to leverage flight opportunities. (6) Education and Public Outreach.
    Keywords: Aircraft Stability and Control
    Type: NATO Advanced Research Workshop on Effects of Space Weather on Tech. Infrastructure
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  • 10
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    Visualizing Decision-making Behaviours in Agent-based Autonomous Spacecraft (2003)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: The authors will report initial progress on the PIAudit project as a Research Resident Associate Program. The objective of this research is to prototype a tool for visualizing decision-making behaviours in autonomous spacecraft. This visualization will serve as an information source for human analysts. The current visualization prototype for PIAudit combines traditional Decision Trees with Weights of Evidence.
    Keywords: Aircraft Stability and Control
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  • 11
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    Use of Soft Computing Technologies For Rocket Engine Control (2003)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The problem to be addressed in this paper is to explore how the use of Soft Computing Technologies (SCT) could be employed to further improve overall engine system reliability and performance. Specifically, this will be presented by enhancing rocket engine control and engine health management (EHM) using SCT coupled with conventional control technologies, and sound software engineering practices used in Marshall s Flight Software Group. The principle goals are to improve software management, software development time and maintenance, processor execution, fault tolerance and mitigation, and nonlinear control in power level transitions. The intent is not to discuss any shortcomings of existing engine control and EHM methodologies, but to provide alternative design choices for control, EHM, implementation, performance, and sustaining engineering. The approaches outlined in this paper will require knowledge in the fields of rocket engine propulsion, software engineering for embedded systems, and soft computing technologies (i.e., neural networks, fuzzy logic, and Bayesian belief networks), much of which is presented in this paper. The first targeted demonstration rocket engine platform is the MC-1 (formerly FASTRAC Engine) which is simulated with hardware and software in the Marshall Avionics & Software Testbed laboratory that
    Keywords: Aircraft Stability and Control
    Type: 22nd Digital Avionics Systems Conference; Oct 12, 2003 - Oct 16, 2003; Indianapolis, IN; United States
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    NASA TECHNICAL REPORTS
  • 12
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    Nonlinear Observers for Gyro Calibration Coupled with a Nonlinear Control Algorithm (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Nonlinear observers for gyro calibration are presented. The first observer estimates a constant gyro bias. The second observer estimates scale factor errors. The third observer estimates the gyro alignment for three orthogonal gyros. The observers are then combined. The convergence properties of all three observers, and the combined observers, are discussed. Additionally, all three observers are coupled with a nonlinear control algorithm. The stability of each of the resulting closed loop systems is analyzed. Simulated test results are presented for each system.
    Keywords: Aircraft Stability and Control
    Type: AAS Guidance and Control Conference; Feb 01, 2004; Breckenridge, CO; United States
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    NASA TECHNICAL REPORTS
  • 13
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    Integration of Online Parameter Identification and Neural Network for In-Flight Adaptive Control (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An indirect adaptive system has been constructed for robust control of an aircraft with uncertain aerodynamic characteristics. This system consists of a multilayer perceptron pre-trained neural network, online stability and control derivative identification, a dynamic cell structure online learning neural network, and a model following control system based on the stochastic optimal feedforward and feedback technique. The pre-trained neural network and model following control system have been flight-tested, but the online parameter identification and online learning neural network are new additions used for in-flight adaptation of the control system model. A description of the modification and integration of these two stand-alone software packages into the complete system in preparation for initial flight tests is presented. Open-loop results using both simulation and flight data, as well as closed-loop performance of the complete system in a nonlinear, six-degree-of-freedom, flight validated simulation, are analyzed. Results show that this online learning system, in contrast to the nonlearning system, has the ability to adapt to changes in aerodynamic characteristics in a real-time, closed-loop, piloted simulation, resulting in improved flying qualities.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212028 , H-2543 , AIAA Paper 2003-5700 , AIAA Atmospheric Flight Mechanics Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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  • 14
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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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  • 15
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    18-Degree-of-Freedom Controller Design for the ST7 Disturbance Reduction System (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Space Technology 7 experiment will perform an on-orbit system-level validation of a Disturbance Reduction System employing gravitational reference sensors and micronewton colloidal thrusters to maintain a spacecraft s position with respect to free-floating test masses in the gravitational reference sensors to less than 10 nm/dHz over the frequency range 1 to 30 mHz. This paper presents the design and analysis of the control system that closes the loop between the gravitational reference sensors and the micronewton thrusters while incorporating star tracker data at low frequencies. The effects of disturbances and actuation and measurement noise are evaluated in a eighteen-degree-of-freedom model.
    Keywords: Aircraft Stability and Control
    Type: AAS-03-586 , AAS Astrodynamics Specialist Conference; Aug 03, 2003 - Aug 07, 2003; Big Sky, MT; United States
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  • 16
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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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  • 17
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    Piloted Evaluation of Modernized Limited Authority Control Laws in the NASA-Ames Vertical Motion Simulator (VMS) (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The UH-60 BLACK HAWK was designed in the 1970s, when the US Army primarily operated during the day in good visual conditions. Subsequently, the introduction of night-vision goggles increased the BLACK HAWK'S mission effectiveness, but the accident rate also increased. The increased accident rate is strongly tied to increased pilot workload as a result of a degradation in visual cues. Over twenty years of research in helicopter flight control and handling qualities has shown that these degraded handling qualities can be recovered by modifying the response type of the helicopter in low speed flight. Sikorsky Aircraft Corporation initiated a project under the National Rotorcraft Technology Center (NRTC) to develop modern flight control laws while utilizing the existing partial authority Stability Augmentation System (SAS) of the BLACK HAWK. This effort resulted in a set of Modernized Control Laws (MCLAWS) that incorporate rate command and attitude command response types. Sikorsky and the US Army Aeroflightdynamics Directorate (AFDD) conducted a piloted simulation on the NASA-Ames Vertical h4otion Simulator, to assess potential handling qualities and to reduce the risk of subsequent implementation and flight test of these modern control laws on AFDD's EH-60L helicopter. The simulation showed that Attitude Command Attitude Hold control laws in pitch and roll improve handling qualities in the low speed flight regime. These improvements are consistent across a range of mission task elements and for both good and degraded visual environments. The MCLAWS perform better than the baseline UH-60A control laws in the presence of wind and turbulence. Finally, while the improved handling qualities in the pitch and roll axis allow the pilot to pay more attention to the vertical axis and hence altitude performance also improves, it is clear from pilot comments and altitude excursions that the addition of an Altitude Hold function would further reduce workload and improve overall handling qualities of the aircraft.
    Keywords: Aircraft Stability and Control
    Type: American Helicopter Society Annual Forum; May 06, 2003 - May 08, 2003; Phoenix, AZ; United States
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  • 18
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    Dynamic Stall Measurements and Computations for a VR-12 Airfoil with a Variable Droop Leading Edge (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: High density-altitude operations of helicopters with advanced performance and maneuver capabilities have lead to fundamental research on active high-lift system concepts for rotor blades. The requirement for this type of system was to improve the sectional lift-to-drag ratio by alleviating dynamic stall on the retreating blade while simultaneously reducing the transonic drag rise of the advancing blade. Both measured and computational results showed that a Variable Droop Leading Edge (VDLE) airfoil is a viable concept for application to a rotor high-lift system. Results are presented for a series of 2D compressible dynamic stall wind tunnel tests with supporting CFD results for selected test cases. These measurements and computations show a dramatic decrease in the drag and pitching moment associated with severe dynamic stall when the VDLE concept is applied to the Boeing VR-12 airfoil. Test results also show an elimination of the negative pitch damping observed in the baseline moment hysteresis curves.
    Keywords: Aircraft Stability and Control
    Type: AHS International Forum 59; May 06, 2003 - May 08, 2003; Phoenix, AZ; United States
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    NASA TECHNICAL REPORTS
  • 19
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    Characterization of Aeromechanics Response and Instability in Fans, Compressors, and Turbine Blades (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This study investigated the effect of interaction between tip clearance flow, steady and unsteady upstream wakes in rotor and stator blade rows in terms of blade forced response. In a stator blade row, the interaction of steady wakes in the upstream rotor frame with the stator imply a blade forced response whose spectrum contains the Blade passing frequency (BPF) and its harmonics, with a decaying amplitude as the frequency increases. When the incoming wakes are unsteady, however, the spectrum of blade excitation exhibits unexpectedly amplified high frequencies due to the modulation of BPF with the fluctuation frequency. In a rotor blade row, a tip flow instability has been demonstrated with a frequency (TVF) equal to 0.45 times the Blade Passing frequency corresponding to a reduced frequency (F(sub c) (sup +)) of 0.7. Under uniform inlet flow conditions, the frequency and spatial content of the tip flow region have been characterized. The disturbance TVF was the dominant disturbance in the flow field and was found to imply variations of the pressure coefficient of more than 30% on the blade tip (between 35% to 90% chord) and in the rotor-generated wake (from 75% to 100% hub-to-tip position). In an attempt to better understand the origin of the instability, the structure of the tip flow has also been analyzed. The interface between the tip flow region and the core flow has been found to have periodical wave-like flow patterns which proceed downstream at a speed of approximately 0.42 times the core flow speed at a frequency corresponding to TVF. A list of conclusions derived from these interactions is presented.
    Keywords: Aircraft Stability and Control
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    NASA TECHNICAL REPORTS
  • 20
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    Active Control of F/A-18 Vertical Tail Buffeting using Piezoelectric Actuators (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Vertical tail buffeting is a serious multidisciplinary problem that limits the performance of twin-tail fighter aircraft. The buffet problem occurs at high angles of attack when the vortical flow breaks down ahead of the vertical tails resulting in unsteady and unbalanced pressure loads on the vertical tails. This paper describes a multidisciplinary computational investigation for buffet load alleviation of full F/A-18 aircraft using distributed piezoelectric actuators. The inboard and outboard surfaces of the vertical tail are equipped with piezoelectric actuators to control the buffet responses in the first bending and torsion modes. The electrodynamics of the smart structure are expressed with a three-dimensional finite element model. A single-input-single-output controller is designed to drive the active piezoelectric actuators. High-fidelity multidisciplinary analysis modules for the fluid dynamics, structure dynamics, electrodynamics of the piezoelectric actuators, fluid-structure interfacing, and grid motion are integrated into a multidisciplinary computing environment that controls the temporal synchronization of the analysis modules. Peak values of the power spectral density of tail tip acceleration are reduced by as much as 22% in the first bending mode and by as much as 82% in the first torsion mode. RMS values of tip acceleration are reduced by as much as 12%.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-1887 , 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics & Materials Conference; Apr 16, 2003 - Apr 19, 2003; Norfolk, VA; United States
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  • 21
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    An Adaptive Critic Approach to Reference Model Adaptation (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Neural networks have been successfully used for implementing control architectures for different applications. In this work, we examine a neural network augmented adaptive critic as a Level 2 intelligent controller for a C- 17 aircraft. This intelligent control architecture utilizes an adaptive critic to tune the parameters of a reference model, which is then used to define the angular rate command for a Level 1 intelligent controller. The present architecture is implemented on a high-fidelity non-linear model of a C-17 aircraft. The goal of this research is to improve the performance of the C-17 under degraded conditions such as control failures and battle damage. Pilot ratings using a motion based simulation facility are included in this paper. The benefits of using an adaptive critic are documented using time response comparisons for severe damage situations.
    Keywords: Aircraft Stability and Control
    Type: AIAA GNC Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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    NASA TECHNICAL REPORTS
  • 22
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    Response Surface Methods for Spatially-Resolved Optical Measurement Techniques (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Response surface methods (or methodology), RSM, have been applied to improve data quality for two vastly different spatial ly-re solved optical measurement techniques. In the first application, modern design of experiments (MDOE) methods, including RSM, are employed to map the temperature field in a direct-connect supersonic combustion test facility at NASA Langley Research Center. The laser-based measurement technique known as coherent anti-Stokes Raman spectroscopy (CARS) is used to measure temperature at various locations in the combustor. RSM is then used to develop temperature maps of the flow. Even though the temperature fluctuations at a single point in the flowfield have a standard deviation on the order of 300 K, RSM provides analytic fits to the data having 95% confidence interval half width uncertainties in the fit as low as +/-30 K. Methods of optimizing future CARS experiments are explored. The second application of RSM is to quantify the shape of a 5-meter diameter, ultra-light, inflatable space antenna at NASA Langley Research Center.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-0648 , 41st Aerospace Sciences Meeting and Exhibit; Jan 06, 2003 - Jan 09, 2003; Reno, NV; United States
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    NASA TECHNICAL REPORTS
  • 23
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    Flight Tests of a Ministick Controller in an F/A-18 Airplane (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: In March of 1999, five pilots performed flight tests to evaluate the handling qualities of an F/A-18 research airplane equipped with a small-displacement center stick (ministick) controller that had been developed for the JAS 39 Gripen airplane (a fighter/attack/ reconnaissance airplane used by the Swedish air force). For these tests, the ministick was installed in the aft cockpit (see figure) and production support flight control computers (PSFCCs) were used as interfaces between the controller hardware and the standard F/A-18 flight-control laws. The primary objective of the flight tests was to assess any changes in handling qualities of the F/A-18 airplane attributable to the mechanical characteristics of the ministick. The secondary objective was to demonstrate the capability of the PSFCCs to support flight-test experiments.
    Keywords: Aircraft Stability and Control
    Type: DRC-01-33 , NASA Tech Briefs, May 2003; 15
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    Next Generation Active Buffet Suppression System (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Buffeting is an aeroelastic phenomenon that is common to high performance aircraft, especially those with twin vertical tails like the F/A-18, at high angles of attack. These loads result in significant random stresses, which may cause fatigue damage leading to restricted capabilities and availability of the aircraft. This paper describes an international collaborative research activity among Australia, Canada and the United States involving the use of active structural control to alleviate the damaging structural response to these loads. The research program is being co-ordinated by the Air Force Research Laboratory (AFRL) and is being conducted under the auspices of The Technical Cooperative Program (TTCP). This truly unique collaborative program has been developed to enable each participating country to contribute resources toward a program that coalesces a broad range of technical knowledge and expertise into a single investigation. This collaborative program is directed toward a full-scale test of an F/A-18 empennage, which is an extension of an earlier initial test. The current program aims at applying advanced directional piezoactuators, the aircraft rudder, switch mode amplifiers and advanced control strategies on a full-scale structure to demonstrate the enhanced performance and capability of the advanced active BLA control system in preparation for a flight test demonstration.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-2905
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    Evaluation of Two Unique Side Stick Controllers in a Fixed-Base Flight Simulator (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A handling qualities analysis has been performed on two unique side stick controllers in a fixed-base F-18 flight simulator. Each stick, which uses a larger range of motion than is common for similar controllers, has a moving elbow cup that accommodates movement of the entire arm for control. The sticks are compared to the standard center stick in several typical fighter aircraft tasks. Several trends are visible in the time histories, pilot ratings, and pilot comments. The aggressive pilots preferred the center stick, because the side sticks are underdamped, causing overshoots and oscillations when large motions are executed. The less aggressive pilots preferred the side sticks, because of the smooth motion and low breakout forces. The aggressive pilots collectively gave the worst ratings, probably because of increased sensitivity of the simulator (compared to the actual F-18 aircraft), which can cause pilot-induced oscillations when aggressive inputs are made. Overall, the elbow cup is not a positive feature, because using the entire arm for control inhibits precision. Pilots had difficulty measuring their performance, particularly during the offset landing task, and tended to overestimate.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212042 , H-2512
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    Neural Flight Control System (2003)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The Neural Flight Control System (NFCS) was developed to address the need for control systems that can be produced and tested at lower cost, easily adapted to prototype vehicles and for flight systems that can accommodate damaged control surfaces or changes to aircraft stability and control characteristics resulting from failures or accidents. NFCS utilizes on a neural network-based flight control algorithm which automatically compensates for a broad spectrum of unanticipated damage or failures of an aircraft in flight. Pilot stick and rudder pedal inputs are fed into a reference model which produces pitch, roll and yaw rate commands. The reference model frequencies and gains can be set to provide handling quality characteristics suitable for the aircraft of interest. The rate commands are used in conjunction with estimates of the aircraft s stability and control (S&C) derivatives by a simplified Dynamic Inverse controller to produce virtual elevator, aileron and rudder commands. These virtual surface deflection commands are optimally distributed across the aircraft s available control surfaces using linear programming theory. Sensor data is compared with the reference model rate commands to produce an error signal. A Proportional/Integral (PI) error controller "winds up" on the error signal and adds an augmented command to the reference model output with the effect of zeroing the error signal. In order to provide more consistent handling qualities for the pilot, neural networks learn the behavior of the error controller and add in the augmented command before the integrator winds up. In the case of damage sufficient to affect the handling qualities of the aircraft, an Adaptive Critic is utilized to reduce the reference model frequencies and gains to stay within a flyable envelope of the aircraft.
    Keywords: Aircraft Stability and Control
    Type: NASA Symposium on Computational Methods for Stability and Control; Sep 23, 2003 - Sep 25, 2003; Hampton, VA; United States
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    Enabling CSPA Operations Through Pilot Involvement in Longitudinal Approach Spacing (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Several major airports around the United States have, or plan to have, closely-spaced parallel runways. This project complemented current and previous research by examining the pilots ability to control their position longitudinally within their approach stream.This project s results considered spacing for separation from potential positions of wake vortices from the parallel approach. This preventive function could enable CSPA operations to very closely spaced runways. This work also considered how pilot involvement in longitudinal spacing could allow for more efficient traffic flow, by allowing pilots to keep their aircraft within tighter arrival slots then air traffic control (ATC) might be able to establish, and by maintaining space within the arrival stream for corresponding departure slots. To this end, this project conducted several research studies providing an analytic and computational basis for calculating appropriate aircraft spacings, experimental results from a piloted flight simulator test, and an experimental testbed for future simulator tests. The following sections summarize the results of these three efforts.
    Keywords: Aircraft Stability and Control
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    18-Degree-of-Freedom Controller Design for the ST7 Disturbance Reduction System (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents the overall design and analysis process of the spacecraft controller being developed at NASA's Goddard Space Flight Center to close the loop between the GRS and the micro-newton colloidal thrusters. The essential dynamics of the ST7-DRS are captured in a simulation including eighteen rigid-body dynamic degrees of freedom: three translations and three rotations for the spacecraft and for each test mass. The ST7 DRS comprises three control systems: the attitude control system (ACS) to maintain a sun-pointing attitude; the drag free control (DFC) to center the spacecraft about the test masses; and the test mass suspension control. This paper summarizes the control design and analysis of the ST7-DRS 18-DOF model, and is an extension of previous analyses employing a 7-DOF planar model of ST-7.
    Keywords: Aircraft Stability and Control
    Type: AAS Astrodynamics Specialist Conference; Aug 03, 2003 - Aug 07, 2003; Big Sky, MT; United States
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    A Nonlinear, Six-Degree of Freedom Precision Formation Control Algorithm, Based on Restricted Three Body Dynamics (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Precision Formation Flying is an enabling technology for a variety of proposed space-based observatories, including the Micro-Arcsecond X-ray Imaging Mission (MAXIM), the associated MAXIM pathfinder mission, and the Stellar Imager. An essential element of the technology is the control algorithm. This paper discusses the development of a nonlinear, six-degree of freedom (6DOF) control algorithm for maintaining the relative position and attitude of a spacecraft within a formation. The translation dynamics are based on the equations of motion for the restricted three body problem. The control law guarantees the tracking error convergences to zero, based on a Lyapunov analysis. The simulation, modelled after the MAXIM Pathfinder mission, maintains the relative position and attitude of a Follower spacecraft with respect to a Leader spacecraft, stationed near the L2 libration point in the Sun-Earth system.
    Keywords: Aircraft Stability and Control
    Type: AAS 03-007 , AAS Guidance and Control Conference; Feb 05, 2003 - Feb 09, 2003; Breckenridge, CO; United States
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    LPV Antiwindup Compensation for Enhanced Flight Control Performance (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: In this paper, we propose a saturation control scheme for linear parameter-varying (LPV) systems from an antiwindup control perspective. The proposed control approach is advantageous because it can be thought of as an augmented control algorithm from the existing control system. Moreover, the synthesis condition for an antiwindup compensator is formulated as a linear matrix inequality (LMI) optimization problem and can be solved efficiently. We have applied the LPV antiwindup controller to an F-16 longitudinal autopilot control system design to enhance aircraft safety and improve flight quality in a high angle of attack region.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-5495 , AIAA Guidance, Navigation and Control Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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    Nonlinear Flutter Aspects of the Flexible HSCT Semispan Model (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The nonlinear aspects that lead to the flutter of an High-Speed Civil Transport (HSCT) Flexible Semispan Model are analyzed. A hierarchy of spectral moments was used to determine the characteristics of the aerodynamic loading and structural strains and motions. The results show that the frequency of the bending motion of the wing varied significantly as the Mach number was increased between 0.90 and 0.97. Examination of the pressure coefficients in terms of mean value and fluctuations showed that the flow characteristics over the wing changed significantly around a Mach number of 0.97. A strong shock was identified near the trailing edge. Nonlinear analysis of the pressure fluctuations, under these conditions, showed nonlinear coupling involving low-frequency components at pressure locations where the mean value was at a local minimum. This shows that the aerodynamic forces acting on the model had nonlinearly coupled frequency components. The results presented here show how nonlinear analysis tools can be used to identify nonlinear aspects of the flutter phenomenon which are needed in the validation of nonlinear computational methodologies. Keywords: Nonlinear aeroelasticity, Flutter, Bispectrum.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-1515 , 44th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 07, 2003 - Apr 10, 2003; Norfolk, VA; United States
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    UAV Flight Control Using Distributed Actuation and Sensing (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An array of effectors and sensors has been designed, tested and implemented on a Blended Wing Body Uninhabited Aerial Vehicle (UAV). This UAV is modified to serve as a flying, controls research, testbed. This effectorhensor array provides for the dynamic vehicle testing of controller designs and the study of decentralized control techniques. Each wing of the UAV is equipped with 12 distributed effectors that comprise a segmented array of independently actuated, contoured control surfaces. A single pressure sensor is installed near the base of each effector to provide a measure of deflections of the effectors. The UAV wings were tested in the North Carolina State University Subsonic Wind Tunnel and the pressure distribution that result from the deflections of the effectors are characterized. The results of the experiments are used to develop a simple, but accurate, prediction method, such that for any arrangement of the effector array the corresponding pressure distribution can be determined. Numerical analysis using the panel code CMARC verifies this prediction method.
    Keywords: Aircraft Stability and Control
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    Neural Network Based Modeling and Analysis of LP Control Surface Allocation (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents an approach to interpretive modeling of LP based control allocation in intelligent flight control. The emphasis is placed on a nonlinear interpretation of the LP allocation process as a static map to support analytical study of the resulting closed loop system, albeit in approximate form. The approach makes use of a bi-layer neural network to capture the essential functioning of the LP allocation process. It is further shown via Lyapunov based analysis that under certain relatively mild conditions the resulting closed loop system is stable. Some preliminary conclusions from a study at Ames are stated and directions for further research are given at the conclusion of the paper.
    Keywords: Aircraft Stability and Control
    Type: AIAA GNC Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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    Aeroservoelastic Model Validation and Test Data Analysis of the F/A-18 Active Aeroelastic Wing (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Model validation and flight test data analysis require careful consideration of the effects of uncertainty, noise, and nonlinearity. Uncertainty prevails in the data analysis techniques and results in a composite model uncertainty from unmodeled dynamics, assumptions and mechanics of the estimation procedures, noise, and nonlinearity. A fundamental requirement for reliable and robust model development is an attempt to account for each of these sources of error, in particular, for model validation, robust stability prediction, and flight control system development. This paper is concerned with data processing procedures for uncertainty reduction in model validation for stability estimation and nonlinear identification. F/A-18 Active Aeroelastic Wing (AAW) aircraft data is used to demonstrate signal representation effects on uncertain model development, stability estimation, and nonlinear identification. Data is decomposed using adaptive orthonormal best-basis and wavelet-basis signal decompositions for signal denoising into linear and nonlinear identification algorithms. Nonlinear identification from a wavelet-based Volterra kernel procedure is used to extract nonlinear dynamics from aeroelastic responses, and to assist model development and uncertainty reduction for model validation and stability prediction by removing a class of nonlinearity from the uncertainty.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212021 , H-2526 , NAS 1.15:212021 , CEAS/AIAA/NVvL International Forum on Aeroelasticity and Structural Dynamics; Jun 04, 2003 - Jun 06, 2003; Amsterdam; Netherlands
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    Historical Review of Uncommanded Lateral-Directional Motions at Transonic Conditions (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents the results of a survey of past experiences with uncommanded lateral-directional motions at transonic speeds during specific military aircraft programs. The effort was undertaken to provide qualitative and quantitative information on past airplane programs that might be of use to the participants in the joint NASA/Navy/Air Force Abrupt Wing Stall (AWS) Program. The AWS Program was initiated because of the experiences of the F/A-l8E/F development program, during which unexpected, severe wing-drop motions were encountered by preproduction aircraft at transonic conditions. These motions were judged to be significantly degrading to the primary mission requirements of the aircraft. Although the problem was subsequently solved for the production version of the F/A-l8E/F, a high-level review panel emphasized the poor understanding of such phenomena and issued a strong recommendation to: "Initiate a national research effort to thoroughly and systematically study the wing drop phenomena." A comprehensive, cooperative NASA/Navy/Air Force AWS Program was designed to respond to provide the required technology requirements. As part of the AWS Program, a work element was directed at a historical review of wing-drop experiences in past aircraft development programs at high subsonic and transonic speeds. In particular, information was requested regarding: specific aircraft configurations that exhibited uncommanded motions and the nature of the motions; geometric characteristics of the air- planes; flight conditions involved in occurrences; relevant data, including wind-tunnel, computational, and flight sources; figures of merit used for analyses; and approaches used to alleviate the problem. An attempt was also made to summarize some of the more important lessons learned from past experiences, and to recommend specific research efforts. In addition to providing technical information to assist the AWS research objectives, the study produced fundamental information regarding the historical challenge of uncommanded lateral-directional motions at transonic conditions and the associated aerodynamic phenomena.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-0590 , 41st Aerospace Sciences Meeting and Exhibit; Jan 06, 2003 - Jan 09, 2003; Reno, NV; United States
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    Free-To-Roll Analysis of Abrupt Wing Stall on Military Aircraft at Transonic Speeds (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Transonic free-to-roll and static wind tunnel tests for four military aircraft - the AV-8B, the F/A-18C, the preproduction F/A-18E, and the F-16C - have been analyzed. These tests were conducted in the NASA Langley 16-Foot Transonic Tunnel as a part of the NASA/Navy/Air Force Abrupt Wing Stall Program. The objectives were to evaluate the utility of the free-to-roll test technique as a tool for predicting areas of significant uncommanded lateral motions and for gaining insight into the wing-drop and wing-rock behavior of military aircraft at transonic conditions. The analysis indicated that the free-to-roll results had good agreement with flight data on all four models. A wide range of motions - limit cycle wing rock, occasional and frequent damped wing drop/rock and wing rock divergence - were observed. The analysis shows the effects that the static and dynamic lateral stability can have on the wing drop/rock behavior. In addition, a free-to-roll figure of merit was developed to assist in the interpretation of results and assessment of the severity of the motions.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-0750 , 41st Aerospace Sciences Meeting and Exhibit; Jan 06, 2003 - Jan 09, 2003; Reno, NV; United States
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    Multiplicative Versus Additive Filtering for Spacecraft Attitude Determination (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The absence of a globally nonsingular three-parameter representation of rotations forces attitude Kalman filters to estimate either a singular or a redundant attitude representation. We compare two filtering strategies using simplified kinematics and measurement models. Our favored strategy estimates a three-parameter representation of attitude deviations from a reference attitude specified by a higher- dimensional nonsingular parameterization. The deviations from the reference are assumed to be small enough to avoid any singularity or discontinuity of the three-dimensional parameterization. We point out some disadvantages of the other strategy, which directly estimates the four-parameter quaternion representation.
    Keywords: Aircraft Stability and Control
    Type: 6th International Conference on Control of Systems and Structures in Space; Jul 18, 2004 - Jul 22, 2004; Riomaggiore; Italy
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    Integration of Online Parameter Identification and Neural Network for In-Flight Adaptive Control (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An indirect adaptive system has been constructed for robust control of an aircraft with uncertain aerodynamic characteristics. This system consists of a multilayer perceptron pre-trained neural network, online stability and control derivative identification, a dynamic cell structure online learning neural network, and a model following control system based on the stochastic optimal feedforward and feedback technique. The pre-trained neural network and model following control system have been flight-tested, but the online parameter identification and online learning neural network are new additions used for in-flight adaptation of the control system model. A description of the modification and integration of these two stand-alone software packages into the complete system in preparation for initial flight tests is presented. Open-loop results using both simulation and flight data, as well as closed-loop performance of the complete system in a nonlinear, six-degree-of-freedom, flight validated simulation, are analyzed. Results show that this online learning system, in contrast to the nonlearning system, has the ability to adapt to changes in aerodynamic characteristics in a real-time, closed-loop, piloted simulation, resulting in improved flying qualities.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-5700 , AIAA Atmospheric Flight Mechanics Conference and Exhibit; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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    Closed-Loop Performance Measures for Flight Controllers Subject to Neutron-Induced Upsets (2003)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: It has been observed that atmospheric neutrons can produce single event upsets in digital flight control hardware. The phenomenon has been studied extensively at the chip level, and now system level experiments are underway. In this paper analytical closed-loop performance measures for the tracking error are developed for a plant that is stabilized by a recoverable computer system subject to neutron induced upsets. The underlying model is a Markov jump-linear system with process noise. The steady-state tracking error is expressed in terms of a generalized observability Gramian.
    Keywords: Aircraft Stability and Control
    Type: WeM14-3 , Proceedings of the 42nd IEEE Conference on Decision and Control; 3; 2465-2470|42nd IEEE Conference on Decision and Control; Dec 01, 2003; Maui, HI; United States
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    Synthetic Jets (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Current investigation of synthetic jets and synthetic jets in cross-flow examined the effects of orifice geometry and dimensions, momentum-flux ratio, cluster of orifices, pitch and yaw angles as well as streamwise development of the flow field. This comprehensive study provided much needed experimental information related to the various control strategies. The results of the current investigation on isolated and clustered synthetic jets with and without cross-flow will be further analyzed and documented in detail. Presentations at national conferences and publication of peer- reviewed journal articles are also expected. Projected publications will present both the mean and turbulent properties of the flow field, comparisons made with the data available in an open literature, as well as recommendations for the future work.
    Keywords: Aircraft Stability and Control
    Type: NASA-OAI Collaborative Aerospace Research and Fellowship Program at NASA Glenn Research Center at Lewis Field; 21-25
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    A Fuzzy Technique for Performing Lateral-Axis Formation Flight Navigation Using Wingtip Vortices (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Close formation flight involving aerodynamic coupling through wingtip vortices shows significant promise to improve the efficiency of cooperative aircraft operations. Impediments to the application of this technology include internship communication required to establish precise relative positioning. This report proposes a method for estimating the lateral relative position between two aircraft in close formation flight through real-time estimates of the aerodynamic effects imparted by the leading airplane on the trailing airplane. A fuzzy algorithm is developed to map combinations of vortex-induced drag and roll effects to relative lateral spacing. The algorithm is refined using self-tuning techniques to provide lateral relative position estimates accurate to 14 in., well within the requirement to maintain significant levels of drag reduction. The fuzzy navigation algorithm is integrated with a leader-follower formation flight autopilot in a two-ship F/A-18 simulation with no intership communication modeled. It is shown that in the absence of measurements from the leading airplane the algorithm provides sufficient estimation of lateral formation spacing for the autopilot to maintain stable formation flight within the vortex. Formation autopilot trim commands are used to estimate vortex effects for the algorithm. The fuzzy algorithm is shown to operate satisfactorily with anticipated levels of input uncertainties.
    Keywords: Aircraft Stability and Control
    Type: NASA/TM-2003-212033 , H-2523 , NAS 1.15:212033
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    Control Reallocation Strategies for Damage Adaptation in Transport Class Aircraft (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This paper examines the feasibility, potential benefits and implementation issues associated with retrofitting a neural-adaptive flight control system (NFCS) to existing transport aircraft, including both cable/hydraulic and fly-by-wire configurations. NFCS uses a neural network based direct adaptive control approach for applying alternate sources of control authority in the presence of damage or failures in order to achieve desired flight control performance. Neural networks are used to provide consistent handling qualities across flight conditions, adapt to changes in aircraft dynamics and to make the controller easy to apply when implemented on different aircraft. Full-motion piloted simulation studies were performed on two different transport models: the Boeing 747-400 and the Boeing C-17. Subjects included NASA, Air Force and commercial airline pilots. Results demonstrate the potential for improving handing qualities and significantly increased survivability rates under various simulated failure conditions.
    Keywords: Aircraft Stability and Control
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    Integrated Approach to the Dynamics and Control of Maneuvering Flexible Aircraft (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This work uses a fundamental approach to the problem of simulating the flight of flexible aircraft. To this end, it integrates into a single formulation the pertinent disciplines, namely, analytical dynamics, structural dynamics, aerodynamics, and controls. It considers both the rigid body motions of the aircraft, three translations (forward motion, sideslip and plunge) and three rotations (roll, pitch and yaw), and the elastic deformations of every point of the aircraft, as well as the aerodynamic, propulsion, gravity and control forces. The equations of motion are expressed in a form ideally suited for computer processing. A perturbation approach yields a flight dynamics problem for the motions of a quasi-rigid aircraft and an 'extended aeroelasticity' problem for the elastic deformations and perturbations in the rigid body motions, with the solution of the first problem entering as an input into the second problem. The control forces for the flight dynamics problem are obtained by an 'inverse' process and the feedback controls for the extended aeroservoelasticity problem are determined by the LQG theory. A numerical example presents time simulations of rigid body perturbations and elastic deformations about 1) a steady level flight and 2) a level steady turn maneuver.
    Keywords: Aircraft Stability and Control
    Type: NASA/CR-2003-211748 , NAS 1.26:211748
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    Analysis of ETMS Data Quality for Traffic Flow Management Decisions (2003)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The data needed for air traffic flow management decision support tools is provided by the Enhanced Traffic Management System (ETMS). This includes both the tools that are in current use and the ones being developed for future deployment. Since the quality of decision support provided by all these tools will be influenced by the quality of the input ETMS data, an assessment of ETMS data quality is needed. Motivated by this desire, ETMS data quality is examined in this paper in terms of the unavailability of flight plans, deviation from the filed flight plans, departure delays, altitude errors and track data drops. Although many of these data quality issues are not new, little is known about their extent. A goal of this paper is to document the magnitude of data quality issues supported by numerical analysis of ETMS data. Guided by this goal, ETMS data for a 24-hour period were processed to determine the number of aircraft with missing flight plan messages at any given instant of time. Results are presented for aircraft above 18,000 feet altitude and also at all altitudes. Since deviation from filed flight plan is also a major cause of trajectory-modeling errors, statistics of deviations are presented. Errors in proposed departure times and ETMS-generated vertical profiles are also shown. A method for conditioning the vertical profiles for improving demand prediction accuracy is described. Graphs of actual sector counts obtained using these vertical profiles are compared with those obtained using the Host data for sectors in the Fort Worth Center to demonstrate the benefit of preprocessing. Finally, results are presented to quantify the extent of data drops. A method for propagating track positions during ETMS data drops is also described.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2003-5626 , AIAA Guidance, Navigation, and Control Conference; Aug 11, 2003 - Aug 14, 2003; Austin, TX; United States
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