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- A SIX-NODE CURVED TRIANGULAR ELEMENT AND A FOUR-NODE QUADRILATERAL ELEMENT FOR ANALYSIS OF LAMINATED COMPOSITE AEROSPACE STRUCTURES , Contractor Report
Authors: C. Wayne Martin and David M. Breiner
Report Number: NASA-CR-2004-210725
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Mathematical development and some computed results are presented for Mindlin plate and shell elements, suitable for analysis of laminated composite and sandwich structures. These elements use the conventional 3 (plate) or 5 (shell) nodal degrees of freedom, have no communicable mechanisms, have no spurious shear energy (no shear locking), have no spurious membrane energy (no membrane locking) and do not require arbitrary reduction of out-of-plane shear moduli or under-integration. Artificial out-of-plane rotational stiffnesses are added at the element level to avoid convergence problems or singularity due to flat spots in shells. This report discusses a 6-node curved triangular element and a 4-node quadrilateral element. Findings show that in regular rectangular meshes, the Martin-Breiner 6-node triangular curved shell (MB6) is approximately equivalent to the conventional 8-node quadrilateral with 2 x 2 integration. The 4-node quadrilateral (MB4)
has very good accuracy for a 4-node element, and may be preferred in vibration analysis because of narrower bandwidth. The mathematical developments used in these elements, those discussed in the seven appendices, have been applied to elements with 3, 4, 6, and 10 nodes and can be applied to other nodal configurations.
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Report Date: July 2004
No. Pages: 58
Funding Organization: 710-55-24-E8-RR-00-000
Keywords: Aerospace engineering; Composites; Curved elements; Finite element; Structural design
Notes: This work was done as partial fulfillment for contract numbers NAS4-97007, NAS4-50079, NCA2-318, and NCA2-497 ranging from 1991–1998. NASA Technical Monitor – Kajal K. Gupta, NASA Dryden Flight Research Center.
- COMBINED LOADS TEST FIXTURE FOR THERMAL-STRUCTURAL TESTING AEROSPACE VEHICLE PANEL CONCEPTS , Technical Memorandum
Authors: Roger A. Fields , W. Lance Richards and V. Michael DeAngelis
Report Number: NASA-TM-2004-212039
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A structural test requirement of the National Aero-Space Plane (NASP) program has resulted in the design, fabrication, and implementation of a combined loads test fixture. Principal requirements for the fixture are testing a 4- by 4-ft hat-stiffened panel with combined axial (either tension or compression) and shear load at temperatures ranging from room temperature to 915 •F, keeping the test panel stresses caused by the mechanical loads uniform, and thermal stresses caused by non-uniform panel temperatures minimized. The panel represents the side fuselage skin of an experimental aerospace vehicle, and was produced for the NASP program. A comprehensive mechanical loads test program using the new test fixture has been conducted on this panel from room temperature to 500 •F. Measured data have been compared with finite-element analyses predictions, verifying that uniform load distributions were achieved by the fixture. The overall
correlation of test data with analysis is excellent. The panel stress distributions and temperature distributions are very uniform and fulfill program requirements. This report provides details of an analytical and experimental validation of the combined loads test fixture. Because of its simple design, this unique test fixture can accommodate panels from a variety of aerospace vehicle designs.
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Subject Category: 39
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Report Date: February 2004
No. Pages: 63
Funding Organization: 710 55 04 E8 RR 00 000
Keywords: Metal matrix composites; Reusable launch vehicles; Strain gages; Structural analysis; Structural testing
- HEAT SHIELDING CHARACTERISTICS AND THERMOSTRUCTURAL PERFORMANCE OF A SUPERALLOY HONEYCOMB SANDWICH THERMAL PROTECTION SYSTEM (TPS) , Technical Publication
Authors: William L. Ko
Report Number: NASA-TP-2004-212024
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Heat-transfer, thermal bending, and mechanical buckling analyses have been performed on a superalloy “honeycomb” thermal protection system (TPS) for future hypersonic flight vehicles. The studies focus on the effect of honeycomb cell geometry on the TPS heat-shielding performance, honeycomb cell wall buckling characteristics, and the effect of boundary conditions on the TPS thermal bending behavior. The results of the study show that the heat-shielding performance of a TPS panel is very sensitive to change in honeycomb core depth, but insensitive to change in honeycomb cell cross-sectional shape. The thermal deformations and thermal stresses in the TPS panel are found to be very sensitive to the edge support conditions. Slight corrugation of the honeycomb cell walls can greatly increase their buckling strength.
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Subject Category: 39
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Report Date: May 2004
No. Pages: 44
Funding Organization: 242-33-02-E8-23-00-TA1
Keywords: Heat shielding performance; Heat transfer; Honeycomb sandwich panels; Thermal buckling; Thermal protection system
- ENERGY MANAGEMENT OF MANNED BOOST-GLIDE VEHICLES: A HISTORICAL PERSPECTIVE , Technical Publication
Authors: Richard E. Day
Report Number: NASA-TP-2004-212037
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: As flight progressed from propellers to jets to rockets, the propulsive energy grew exponentially. With the development of rocket-only boosted vehicles, energy management of these boost-gliders became a distinct requirement for the unpowered return to base, alternate landing site, or water-parachute landing, starting with the X-series rocket aircraft and terminating with the present-day Shuttle. The problem presented here consists of: speed (kinetic energy)—altitude (potential energy)—steep glide angles created by low lift-to-drag ratios (L/D)— distance to landing site—and the bothersome effects of the atmospheric characteristics varying with altitude. The primary discussion regards post-boost, stabilized glides; however, the effects of centrifugal and geopotential acceleration are discussed as well. The aircraft and spacecraft discussed here are the X-1, X-2, X-15, and the Shuttle; and to a lesser, comparative extent,
Mercury, Gemini, Apollo, and lifting bodies. The footprints, landfalls, and methods developed for energy management are also described. The essential tools required for energy management—simulator planning, instrumentation, radar, telemetry, extended land or water range, Mission Control Center (with specialist controllers), and emergency alternate landing sites—were first established through development of early concepts and were then validated by research flight tests.
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Report Date: May 2004
No. Pages: 73
Funding Organization: 036-00-00-GM-T T-00-HIS
Keywords: Approach and landing; Energy management; History of rocket aircraft; Mission control center; Rocket propulsion
- DEVELOPMENT AND TESTING OF THE PHASE 0 AUTONOMOUS FORMATION FLIGHT RESEARCH SYSTEM , Technical Memorandum
Authors: Shane Petersen , Steven Krasiewski , Jay Fantini , Ken Norlin and John Theisen
Report Number: NASA-TM-2004-212040
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The Autonomous Formation Flight (AFF) project was initiated in 1995 to demonstrate at least 10-percent drag reduction by positioning a trailing aircraft in the wingtip vortex of a leading aircraft. If successful, this technology would provide increased fuel savings, reduced emissions, and extended flight duration for fleet aircraft flying in formation. To demonstrate this technology, the AFF project at NASA Dryden Flight Research Center developed a system architecture incorporating two F-18 aircraft flying in leading-trailing formation. The system architecture has been designed to allow the trailing aircraft to maintain station-keeping position relative to the leading aircraft within +/-10 ft. Development of this architecture would be directed at the design and development of a computing system to feed surface position commands into the flight control computers, thereby controlling the longitudinal and lateral position of the trailing aircraft. In
addition, modification to the instrumentation systems of both aircraft, pilot displays, and a means of broadcasting the leading aircraft inertial and global positioning system-based positional data to the trailing aircraft would be needed. This presentation focuses on the design and testing of the AFF Phase 0 research system.
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Subject Category: 31
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Report Date: January 2004
No. Pages: 24
Funding Organization: 706-35-00-E8-28-00-AFF
Keywords: Autonomous formation flight; Development and testing; NASA Dryden; System architecture; Unmanned aerial vehicle
Notes: Also presented at the AIAA First Conference on Unmanned Aerospace Vehicles, Systems, Technologies, and Operations, Portsmouth, Virginia, May 20–22, 2002.
- 2000–2001 RESEARCH ENGINEERING ANNUAL REPORT , Technical Memorandum
Authors: J. Larry Crawford and Everlyn Cruciani
Report Number: NASA-TM-2004-212025
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Selected research and technology activities at Dryden Flight Research Center are summarized. These activities exemplify the Center’s varied and productive research efforts.
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Subject Category: 99
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Report Date: January 2004
No. Pages: 90
Funding Organization: SAEX22004D
Keywords: Aerodynamics; Flight; Flight controls; Flight systems; Flight test; Instrumentation; Propulsion; Structures; Structural dynamics
- THERMAL BUCKLING ANALYSIS OF RECTANGULAR PANELS SUBJECTED TO HUMPED TEMPERATURE PROFILE HEATING , Technical Publication
Authors: William L. Ko
Report Number: NASA-TP-2004-212041
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: This research investigates thermal buckling characteristics of rectangular panels subjected to different types of humped temperature profile heating. Minimum potential energy and finite-element methods are used to calculate the panel buckling temperatures. The two methods give fairly close thermal buckling solutions. “Buckling temperature magnification factor of the first kind, eta” is established for the fixed panel edges to scale up the buckling solution of uniform temperature loading case to give the buckling solution of the humped temperature profile loading cases. Also, “buckling temperature magnification factor of the second kind, xi” is established for the free panel edges to scale up the buckling solution of humped temperature profile loading cases with unheated boundary heat sinks to give the buckling solutions when the boundary heat sinks are heated up.
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Subject Category: 39
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Report Date: January 2004
No. Pages: 55
Funding Organization: 090-50-00-SE-RR-00-000
Keywords: Buckling temperature magnification factors; Finite-element method; Humped temperature profile heating; Minimum potential energy method; Thermal buckling
- MANUAL MANIPULATION OF ENGINE THROTTLES FOR EMERGENCY FLIGHT CONTROL , Technical Memorandum
Authors: Frank W. Burcham, Jr. , C. Gordon Fullerton and Trindel A. Maine
Report Number: NASA-TM-2004-212045
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: If normal aircraft flight controls are lost, emergency flight control may be attempted using only engines thrust. Collective thrust is used to control flightpath, and differential thrust is used to control bank angle. Flight test and simulation results on many airplanes have shown that pilot manipulation of throttles is usually adequate to maintain up-and-away flight, but is most often not capable of providing safe landings. There are techniques that will improve control and increase the chances of a survivable landing. This paper reviews the principles of throttles-only control (TOC), a history of accidents or incidents in which some or all flight controls were lost, manual TOC results for a wide range of airplanes from simulation and flight, and suggested techniques for flying with throttles only and making a survivable landing.
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Report Date: January 2004
No. Pages: 78
Funding Organization: 090-50-00-SE-RR-00-000
Keywords: B-747; C-17; Emergency flight control; MD-11; Propulsive control; Throttles-only control
- DEBONDING STRESS CONCENTRATIONS IN A PRESSURIZED LOBED SANDWICH-WALLED GENERIC CRYOGENIC TANK , Technical Publication
Authors: William L. Ko
Report Number: NASA-TP-2004-212849
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A finite-element stress analysis has been conducted on a lobed composite sandwich tank subjected to internal pressure and cryogenic cooling. The lobed geometry consists of two obtuse circular walls joined together with a common flat wall. Under internal pressure and cryogenic cooling, this type of lobed tank wall will experience open-mode (a process in which the “honeycomb” is stretched in the depth direction) and shear stress concentrations at the junctures where curved wall changes into flat wall (known as a curve-flat juncture). Open-mode and shear stress concentrations occur in the honeycomb core at the curve-flat junctures and could cause debonding failure. The levels of contributions from internal pressure and temperature loading to the open-mode and shear debonding failure are compared. The lobed fuel tank with honeycomb sandwich walls has been found to be a structurally unsound geometry because of very low debonding failure
strengths. The debonding failure problem could be eliminated if the honeycomb core at the curve-flat juncture is replaced with a solid core.
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Subject Category: 39
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Report Date: May 2004
No. Pages: 34
Funding Organization: 090-50-00-SE-RR-00-000
Keywords: Composite honeycomb sandwich wall; Lobed cryogenic tank; Open-mode debonding; Stress concentrations; Thermocryogenic stress analysis
- CALCULATED DRAG OF AN AERIAL REFUELING ASSEMBLY THROUGH AIRPLANE PERFORMANCE ANALYSIS , Technical Memorandum
Authors: Michael Jacob Vachon , Ronald J. Ray and Carl Calianno
Report Number: NASA-TM-2004-212043
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The aerodynamic drag of an aerial refueling assembly was calculated during the Automated Aerial Refueling project at the NASA Dryden Flight Research Center. An F/A-18A airplane was specially instrumented to obtain accurate fuel flow measurements and to determine engine thrust. A standard Navy air refueling store with a retractable refueling hose and paradrogue was mounted to the centerline pylon of the F/A-18A airplane. As the paradrogue assembly was deployed and stowed, changes in the calculated thrust of the airplane occurred and were equated to changes in vehicle drag. These drag changes were attributable to the drag of the paradrogue assembly. The drag of the paradrogue assembly was determined to range from 200 to 450 lbf at airspeeds from 170 to 250 knots indicated airspeed. Analysis of the drag data resulted in a single drag coefficient of 0.0056 for the paradrogue assembly that adequately matched the calculated drag for all flight conditions.
The drag relief provided to the tanker airplane when a receiver airplane engaged the paradrogue is also documented from 35 to 270 lbf at the various flight conditions tested. The results support the development of accurate aerodynamic models to be used in refueling simulations and control laws for fully autonomous refueling.
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Report Date: February 2004
No. Pages: 25
Funding Organization: WU 090-50-00-SE-RR-00-000
Keywords: Aerial refueling; Aircraft performance; Drag measurement; Thrust measurement; UAV
Notes: Also presented at the 42nd AIAA Aerospace Sciences Meeting & Exhibit, Reno, NV, Jan. 5–8, 2004, AIAA-2004-0381. Carl Calianno, United States Naval Air Systems Command, Patuxent River, Maryland.
- DEVELOPMENT AND TESTING OF A DROGUE PARACHUTE SYSTEM FOR X-37 ALTV/B-52H SEPARATION , Technical Memorandum
Authors: Stephen A. Whitmore , Brent R. Cobleigh , Steven R. Jacobson , Steven C. Jensen and Elsa J. Hennings
Report Number: NASA-TM-2004-212044
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Multiple scenarios were identified in which the X-37 approach and landing test vehicle (ALTV) catastrophically recontacts the B-52H carrier aircraft after separation. The most cost-effective recontact risk mitigation is the prelaunch deployment of a drogue parachute that is released after the X-37 ALTV has safely cleared the B-52H. After release, a fully-inflated drogue parachute takes 30 min to reach ground and results in a large footprint that excessively restricts the days available for flight. To reduce the footprint, a passive collapse mechanism consisting of an elastic reefing line attached to the parachute skirt was developed. At flight loads the elastic is stretched, allowing full parachute inflation. After release, drag loads drop dramatically and the elastic line contracts, reducing the frontal drag area. A 50-percent drag reduction results in an approximately 75-percent ground footprint reduction. Eleven individual parachute designs were
evaluated at flight load dynamic pressures in the High Velocity Airflow System (HIVAS) at the Naval Air Warfare Center (NAWC), China Lake, California. Various options for the elastic reefing system were also evaluated at HIVAS. Two best parachute designs were selected from HIVAS to be carried forward to flight test. Detailed HIVAS test results are presented in this report.
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Report Date: May 2004
No. Pages: 42
Funding Organization: 760-90-00-SE-53-00-37A
Keywords: Aerodynamic flight test; Low temperature elastomer; Orbital transfer vehicle; Parachute design; Stores separation
Notes: Also presented at the 42nd AIAA Aerospace Sciences Meeting and Exhibit, Reno, Nevada, January 5–8, 2004, AIAA-2004-0873.
- HYPOTHETICAL REENTRY THERMOSTRUCTURAL PERFORMANCE OF SPACE SHUTTLE ORBITER WITH MISSING OR ERODED THERMAL PROTECTION TILES , Technical Memorandum
Authors: William L. Ko , Leslie Gong and Robert D. Quinn
Report Number: NASA-TM-2004-212850
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: This report deals with hypothetical reentry thermostructural performance of the Space Shuttle orbiter with missing or eroded thermal protection system (TPS) tiles. The original STS-5 heating (normal transition at 1100 sec) and the modified STS-5 heating (premature transition at 800 sec) were used as reentry heat inputs. The TPS missing or eroded site is assumed to be located at the center or corner (spar- rib juncture) of the lower surface of wing midspan bay 3. For cases of missing TPS tiles, under the original STS-5 heating, the orbiter can afford to lose only one TPS tile at the center or two TPS tiles at the corner (spar-rib juncture) of the lower surface of wing midspan bay 3. Under modified STS-5 heating, the orbiter cannot afford to lose even one TPS tile at the center or at the corner of the lower surface of wing midspan bay 3. For cases of eroded TPS tiles, the aluminum skin temperature rises relatively slowly with the decreasing thickness
of the eroded central or corner TPS tile until most of the TPS tile is eroded away, and then increases exponentially toward the missing tile case.
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Subject Category: 34
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Report Date: July 2004
No. Pages: 43
Funding Organization: 090-50-00-SE-RR-00-000
Keywords: Eroded TPS; Missing TPS; Reentry heat transfer; Reentry survivability; Space Shuttle orbiter
- FLIGHT TEST RESULTS FOR THE F-16XL WITH A DIGITAL FLIGHT CONTROL SYSTEM , Technical Publication
Authors: Susan J. Stachowiak and John T. Bosworth
Report Number: NASA-TM-2004-212046
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: In the early 1980s, two F-16 airplanes were modified to extend the fuselage length and incorporate a large area delta wing planform. These two airplanes, designated the F-16XL, were designed by the General Dynamics Corporation (now Lockheed Martin Tactical Aircraft Systems) (Fort Worth, Texas) and were prototypes for a derivative fighter evaluation program conducted by the United States Air Force. Although the concept was never put into production, the F-16XL prototypes provided a unique planform for testing concepts in support of future high-speed supersonic transport aircraft. To extend the capabilities of this testbed vehicle the F- 16XL ship 1 aircraft was upgraded with a digital flight control system. The added flexibility of a digital flight control system increases the versatility of this airplane as a testbed for aerodynamic research and investigation of advanced technologies. This report presents the handling qualities flight test results
covering the envelope expansion of the F-16XL with the digital flight control system.
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Subject Category: 08
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Report Date: March 2004
No. Pages: 45
Funding Organization: 953-50-00-SE-RR-00-000
Keywords: F-16XL aircraft; Flight test; Handling qualities; Low-order equivalent systems; Neal–Smith criteria
- 2002 RESEARCH ENGINEERING ANNUAL REPORT , Technical Memorandum
Authors: J. Larry Crawford and Everlyn Cruciani�
Report Number: NASA-TM-2004-212851
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: Selected research and technology activities at Dryden Flight Research Center are summarized. These activities exemplify the Center's varied and productive research efforts.�
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Subject Category: 99
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Report Date: September 2004
No. Pages: 48
Keywords: Aerodynamics; Flight; Flight controls; Flight systems; Flight test; Instrumentation; Propulsion; Structures; Structural dynamics�
- MOBILE AERIAL TRACKING AND IMAGING SYSTEM (MATRIS) FOR AERONAUTICAL RESEARCH , Technical Memorandum
Authors: Daniel W. Banks , Robert C. Blanchard and Geoffrey M. Miller
Report Number: NASA-TM-2004-212852
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: A mobile, rapidly deployable ground-based system to track and image targets of aeronautical interest has been developed. Targets include reentering reusable launch vehicles as well as atmospheric and transatmospheric vehicles. The optics were designed to image targets in the visible and infrared wavelengths. To minimize acquisition cost and development time, the system uses commercially available hardware and software where possible. The conception and initial funding of this system originated with a study of ground-based imaging of global aerothermal characteristics of reusable launch vehicle configurations. During that study the National Aeronautics and Space Administration teamed with the Missile Defense Agency/Innovative Science and Technology Experimentation Facility to test techniques and analysis on two Space Shuttle flights.
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Subject Category: 34
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Report Date: August 2004
No. Pages: 17
Funding Organization: 090-20-00-GA-XR-00-SLE
Keywords: Aeroheating; Boundary-layer transition; Imaging system; Infrared thermography; Object tracking; Reentry vehicles; Space Shuttle Orbiter
Notes: Also presented at the 11th International Symposium on Flow Visualization, August 9–12, 2004, University of Notre Dame, Notre Dame, Indiana.
- STRAIN-GAGE LOADS CALIBRATION PARAMETRIC STUDY , Technical Memorandum
Authors: William A. Lokos
Report Number: NASA-TM-2004-212853
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: This report documents a parametric study of various aircraft wing-load test features that affect the quality of the resultant derived shear, bending-moment, and torque strain-gage load equations. The effect of the following on derived strain-gage equation accuracy are compared: single-point loading compared with distributed loading, variation in applied test load magnitude, number of applied load cases, and wing-box-only compared with control-surface loading. The subject of this study is an extensive wing-load calibration test of the Active Aeroelastic Wing F/A-18 aircraft. Selected subsets of the available test data were used to derive load equations using the linear regression method. Results show the benefit of distributed loading and the diminishing-return benefits of test load magnitudes and number of load cases. The use of independent check cases as a quality metric for the derived load equations is shown to overcome blind extrapolating beyond
the load data used to derive the load equations.
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Report Date: August 2004
No. Pages: 33
Funding Organization: 710-61-14-SE-14-00-AAW
Keywords: Calibration parametric study; F/A-18 AAW; Loads calibration optimization; Loads calibration test; Loads test design; Strain-gage calibration
Notes: Also presented at the 24th Congress of the International Council of the Aeronautical Sciences (ICAS), Yokohama, Japan, Aug. 29–Sept. 3, 2004, paper no. 278.
- COMPUTER-AIDED SYSTEMS ENGINEERING FOR FLIGHT RESEARCH PROJECTS USING A WORKGROUP DATABASE, Technical Memorandum
Authors: Masashi Mizukami
Report Number: NASA-TM-212860
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: An online systems engineering tool for flight research projects has been developed through the use of a workgroup database. Capabilities are implemented for typical flight research systems engineering needs in document library, configuration control, hazard analysis, hardware database, requirements management, action item tracking, project team information, and technical performance metrics. Repetitive tasks are automated to reduce workload and errors. Current data and documents are instantly available online and can be worked on collaboratively. Existing forms and conventional processes are used, rather than inventing or changing processes to fit the tool. An integrated tool set offers advantages by automatically cross-referencing data, minimizing redundant data entry, and reducing the number of programs that must be learned. With a simplified approach, significant improvements are attained over existing capabilities for minimal cost. By using a workgroup-level database platform, personnel most directly involved in the project can develop, modify, and maintain the system, thereby saving time and money. As a pilot project, the system has been used to support an in-house flight experiment. Options are proposed for developing and deploying this type of tool on a more extensive basis.
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Subject Category: 61
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Report Date: December 2004
No. Pages: 23
Funding Organization: ES4
Keywords: Computer database; Configuration control; Flight testing; Product data management; Systems engineering
- REAL-TIME UNSTEADY LOADS MEASUREMENTS USING HOT-FILM SENSORS , Technical Memorandum
Authors: Arun S. Mangalam and Timothy R. Moes
Report Number: NASA-TM-2004-212854
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: 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.
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Subject Category: 02
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Report Date: August 2004
No. Pages: 19
Funding Organization: 090-50-00-SE-RR-00-000
Keywords: Aerodynamic loads; Constant voltage anemometer; Dynamic lift; Dynamic stall; Flow separation; Hot-film; Phase reversal signature; Stagnation point; Unsteady aerodynamics
Notes: Also presented at the 22nd AIAA Applied Aerodynamics Conference and Exhibit, Providence, Rhode Island, August 16–19, 2004.
- SELECTED FLIGHT TEST RESULTS FOR ONLINE LEARNING NEURAL NETWORK-BASED FLIGHT CONTROL SYSTEM, Technical Memorandum
Authors: Peggy S. Williams-Hayes
Report Number: NASA-TM-2004-212857
Performing Organization: NASA Dryden Flight Research Center, Edwards, CA
Abstract: The NASA F-15 Intelligent Flight Control System project team developed a series of flight control concepts designed to demonstrate neural network-based adaptive controller benefits, with the objective to develop and flight-test control systems using neural network technology to optimize aircraft performance under nominal conditions and stabilize the aircraft under failure conditions. This report presents flight-test results for an adaptive controller using stability and control derivative values from an online learning neural network. A dynamic cell structure neural network is used in conjunction with a real-time parameter identification algorithm to estimate aerodynamic stability and control derivative increments to baseline aerodynamic derivatives in flight. This open-loop flight test set was performed in preparation for a future phase in which the learning neural network and parameter identification algorithm output would provide the flight controller with aerodynamic stability and control derivative updates in near real time. Two flight maneuvers are analyzed - pitch frequency sweep and automated flight-test maneuver designed to optimally excite the parameter identification algorithm in all axes. Frequency responses generated from flight data are compared to those obtained from nonlinear simulation runs. Flight data examination shows that addition of flight- identified aerodynamic derivative increments into the simulation improved aircraft pitch handling qualities.
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Subject Category: 08
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Report Date: December 2004
No. Pages: 16
Funding Organization: 711-60-00-SE-80-00-AUR
Keywords: Adaptive control; Automatic flight control; F-15 aircraft; Neural nets; Parameter identification; Real-time operation
Notes: Also presented at the AIAA 1st Intelligent Systems Technical Conference, Chicago, Illinois, September 20-23, 2004.
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