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  • AIRCRAFT
  • Aerodynamics
  • Aircraft Stability and Control
  • GENERAL
  • 2000-2004  (18)
  • 1955-1959
  • 1925-1929
  • 2002  (18)
Collection
Keywords
Years
  • 2000-2004  (18)
  • 1955-1959
  • 1925-1929
Year
  • 1
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    Opportunities for Breakthroughs in Large-Scale Computational Simulation and Design (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Opportunities for breakthroughs in the large-scale computational simulation and design of aerospace vehicles are presented. Computational fluid dynamics tools to be used within multidisciplinary analysis and design methods are emphasized. The opportunities stem from speedups and robustness improvements in the underlying unit operations associated with simulation (geometry modeling, grid generation, physical modeling, analysis, etc.). Further, an improved programming environment can synergistically integrate these unit operations to leverage the gains. The speedups result from reducing the problem setup time through geometry modeling and grid generation operations, and reducing the solution time through the operation counts associated with solving the discretized equations to a sufficient accuracy. The opportunities are addressed only at a general level here, but an extensive list of references containing further details is included. The opportunities discussed are being addressed through the Fast Adaptive Aerospace Tools (FAAST) element of the Advanced Systems Concept to Test (ASCoT) and the third Generation Reusable Launch Vehicles (RLV) projects at NASA Langley Research Center. The overall goal is to enable greater inroads into the design process with large-scale simulations.
    Keywords: Aerodynamics
    Type: NASA/TM-2002-211747 , L-18196 , NAS 1.15:211747
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Nonlinear Analysis of Airfoil High-Intensity Gust Response Using a High-Order Prefactored Compact Code (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The nonlinear response of symmetric and loaded airfoils to an impinging vortical gust is investigated in the parametric space of gust dimension, intensity, and frequency. The study, which was designed to investigate the validity limits for a linear analysis, is implemented by applying a nonlinear high-order prefactored compact code and comparing results with linear solutions from the GUST3D frequency-domain solver. Both the unsteady aerodynamic and acoustic gust responses are examined.
    Keywords: Aircraft Stability and Control
    Type: AIAA Paper 2002-2535 , 8th AIAA/CEAS Aeroacoustics Conference and Exhibit; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Effect of Variable Chord Length on Transonic Axial Rotor Performance Investigated (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: During the life of any gas turbine, blade erosion is present, especially for those units that are exposed to unfiltered air, such as aviation turbofan engines. The effect of this erosion is to reduce the blade chord progressively from the midspan to the tip region and to roughen and distort the blade surface. The effects of roughness on rotor performance have been documented by Suder et al. and Roberts. These papers indicate that the penalty for leading-edge roughness and erosion can be significant. Turbofan operators, therefore, restore chord length at routine maintenance intervals to regain performance before deterioration is too severe to salvage blades. As the rotor blades erode, the leading edge becomes rough - blunt and distorted from the nominal shape - and the aerodynamic performance suffers. Nominal performance can be recovered by recontouring the leading edges. This process, which inherently shortens the blade chord, can be used until the blade chord erodes to the stall limit. Below this chord length, which varies among engine-compressor types, a decrease of stall margin is likely. After compressor blade rework that includes leading edge recontouring, the blades have different chord lengths, ranging from blades that are near nominal chord length down to those near the stall chord limit. Furthermore, as blades erode below the stall limit, they must be replaced with new blades that have the full nominal chord length. Consequently, a set of compressor blades with varying chord lengths will be installed into each turbofan engine that goes through a complete maintenance cycle. The question arises, "Does fan or compressor performance depend on the order in which mixed-chord blades are installed into a fan or compressor disk?"
    Keywords: Aerodynamics
    Type: Research and Technology 2001; NASA/TM-2002-211333
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Piloted Evaluation of a UH-60 Mixer Equivalent Turbulence Simulation Model (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A simulation study of a recently developed hover/low speed Mixer Equivalent Turbulence Simulation (METS) model for the UH-60 Black Hawk helicopter was conducted in the NASA Ames Research Center Vertical Motion Simulator (VMS). The experiment was a continuation of previous work to develop a simple, but validated, turbulence model for hovering rotorcraft. To validate the METS model, two experienced test pilots replicated precision hover tasks that had been conducted in an instrumented UH-60 helicopter in turbulence. Objective simulation data were collected for comparison with flight test data, and subjective data were collected that included handling qualities ratings and pilot comments for increasing levels of turbulence. Analyses of the simulation results show good analytic agreement between the METS model and flight test data, with favorable pilot perception of the simulated turbulence. Precision hover tasks were also repeated using the more complex rotating-frame SORBET (Simulation Of Rotor Blade Element Turbulence) model to generate turbulence. Comparisons of the empirically derived METS model with the theoretical SORBET model show good agreement providing validation of the more complex blade element method of simulating turbulence.
    Keywords: Aircraft Stability and Control
    Type: American Helicopter Society''s 59th Annual Forum and Technology Display; May 06, 2003 - May 08, 2003; Phoenix, AZ; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Rotor Wake Vortex Definition: Initial Evaluation of 3-C PIV Results of the Hart-II Study (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An initial evaluation is made of extensive three-component (3C) particle image velocimetry (PIV) measurements within the wake across a rotor disk plane. The model is a 40 percent scale BO-105 helicopter main rotor in forward flight simulation. This study is part of the HART II test program conducted in the German-Dutch Wind Tunnel (DNW). Included are wake vortex field measurements over the advancing and retreating sides of the rotor operating at a typical descent landing condition important for impulsive blade-vortex interaction (BVI) noise. Also included are advancing side results for rotor angle variations from climb to steep descent. Using detailed PIV vector maps of the vortex fields, methods of extracting key vortex parameters are examined and a new method was developed and evaluated. An objective processing method, involving a center-of-vorticity criterion and a vorticity 'disk' integration, was used to determine vortex core size, strength, core velocity distribution characteristics, and unsteadiness. These parameters are mapped over the rotor disk and offer unique physical insight for these parameters of importance for rotor noise and vibration prediction.
    Keywords: Aerodynamics
    Type: 28th European Rotorcraft Forum; Sep 17, 2002 - Sep 20, 2002; Bristol, England; United Kingdom
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Induced Moment Effects of Formation Flight Using Two F/A-18 Aircraft (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Previous investigations into formation flight have shown the possibility for significant fuel savings through drag reduction. Using two F/A-18 aircraft, NASA Dryden Flight Research Center has investigated flying aircraft in autonomous formation. Positioning the trailing airplane for best drag reduction requires investigation of the wingtip vortex effects induced by the leading airplane. A full accounting of the vortex effect on the trailing airplane is desired to validate vortex-effect prediction methods and provide a database for the design of a formation flight autopilot. A recent flight phase has mapped the complete wingtip vortex effects at two flight conditions with the trailing airplane at varying distances behind the leading one. Force and moment data at Mach 0.56 and an altitude of 25,000 ft and Mach 0.86 and an altitude of 36,000 ft have been obtained with 20, 55, 110, and 190 ft of longitudinal distance between the aircraft. The moments induced by the vortex on the trailing airplane were well within the pilot's ability to control. This report discusses the data analysis methods and vortex-induced effects on moments and side force. An assessment of the impact of the nonlinear vortex effects on the design of a formation autopilot is offered.
    Keywords: Aerodynamics
    Type: NASA/TM-2002-210732 , NAS 1.15:210732 , H-2502 , AIAA Atmospheric Flight Mechanics Conference and Exhibit; Aug 05, 2002 - Aug 08, 2002; Monterey, CA; United States
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Experimental Test Results of Energy Efficient Transport (EET) High-Lift Airfoil in Langley Low-Turbulence Pressure Tunnel (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This report describes the results of an experimental study conducted in the Langley Low-Turbulence Pressure Tunnel to determine the effects of Reynolds number and Mach number on the two-dimensional aerodynamic performance of the Langley Energy Efficient Transport (EET) High-Lift Airfoil. The high-lift airfoil was a supercritical-type airfoil with a thickness-to- chord ratio of 0.12 and was equipped with a leading-edge slat and a double-slotted trailing-edge flap. The leading-edge slat could be deflected -30 deg, -40 deg, -50 deg, and -60 deg, and the trailing-edge flaps could be deflected to 15 deg, 30 deg, 45 deg, and 60 deg. The gaps and overlaps for the slat and flaps were fixed at each deflection resulting in 16 different configurations. All 16 configurations were tested through a Reynolds number range of 2.5 to 18 million at a Mach number of 0.20. Selected configurations were also tested through a Mach number range of 0.10 to 0.35. The plotted and tabulated force, moment, and pressure data are available on the CD-ROM supplement L-18221.
    Keywords: Aerodynamics
    Type: NASA/TM-2002-211780 , NAS 1.15:211780 , L-18221
    Format: application/pdf
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  • 8
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    Simulation Study of Impact of Aeroelastic Characteristics on Flying Qualities of a High Speed Civil Transport (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A piloted simulation study conducted in NASA Langley Visual Motion Simulator addressed the impact of dynamic aero- servoelastic effects on flying qualities of a High Speed Civil Transport. The intent was to determine effectiveness of measures to reduce the impact of aircraft flexibility on piloting tasks. Potential solutions examined were increasing frequency of elastic modes through structural stiffening, increasing damping of elastic modes through active control, elimination of control effector excitation of the lowest frequency elastic modes, and elimination of visual cues associated with elastic modes. Six test pilots evaluated and performed simulated maneuver tasks, encountering incidents wherein cockpit vibrations due to elastic modes fed back into the control stick through involuntary vibrations of the pilots upper body and arm. Structural stiffening and compensation of the visual display were of little benefit in alleviating this impact, while increased damping and elimination of control effector excitation of the elastic modes both offered great improvements when applied in sufficient degree.
    Keywords: Aircraft Stability and Control
    Type: NASA/TP-2002-211943 , L-18157 , NAS 1.60:211943
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Experimental Test Results of the Energy Efficient Transport (EET) Flap-Edge Vortex Model in the Langley Low-Turbulence Pressure Tunnel (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This report presents the results of a test conducted in the Langley Low-Turbulence Pressure Tunnel to measure the flow field properties of a flap-edge vortex. The model was the EET (Energy Efficient Transport) Flap-Edge Vortex Model, which consists of a main element and a part-span, single-slotted trailing-edge flap. The model surface was instrumented with several chordwise and spanwise rows of pressure taps on each element. The off-body flow field velocities were to be measured in several planes perpendicular to the flap edge with a laser velocimetry system capable of measuring all three components in coincidence. However, due to seeding difficulties, the preliminary laser data did not have sufficient accuracy to be suitable for presentation; therefore, this report presents only the tabulated and plotted surface pressure data. In addition, the report contains a detail description of the model which can be used to generate accurate CFD grid structures.
    Keywords: Aerodynamics
    Type: NASA/TM-2002-211928 , L-18230 , NAS 1.15:211928
    Format: application/pdf
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  • 10
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    Piloted Simulation Assessment of a High-Speed Civil Transport Configuration (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: An assessment of a proposed configuration of a high-speed civil transport was conducted by using NASA and industry research pilots. The assessment was conducted to evaluate operational aspects of the configuration from a pilot's perspective, with the primary goal being to identify potential deficiencies in the configuration. The configuration was evaluated within and at the limits of the design operating envelope to determine the suitability of the configuration to maneuver in a typical mission as well as in emergency or envelope-limit conditions. The Cooper-Harper rating scale was used to evaluate the flying qualities of the configuration. A summary flying qualities metric was also calculated. The assessment was performed in the Langley six-degree-of-freedom Visual Motion Simulator. The effect of a restricted cockpit field-of-view due to obstruction by the vehicle nose was not included in this study. Tasks include landings, takeoffs, climbs, descents, overspeeds, coordinated turns, and recoveries from envelope limit excursions. Emergencies included engine failures, loss of stability augmentation, engine inlet unstarts, and emergency descents. Minimum control speeds and takeoff decision, rotation, and safety speeds were also determined.
    Keywords: Aircraft Stability and Control
    Type: NASA/TP-2002-211441 , L-17587 , NAS 1.60:211441
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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