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  • 1
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    Dynamic response of active twist rotor blades (2001)
    Institute of Physics
    Details
    Publication Date: 2001-02-01
    Print ISSN: 0964-1726
    Electronic ISSN: 1361-665X
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Institute of Physics
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    PAPER CURRENT
  • 2
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    Reduction of blade-vortex interaction noise through higher harmonic pitch control (1990)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.
    Keywords: ACOUSTICS
    Type: American Helicopter Society, Journal (ISSN 0002-8711); 35; 86-91
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Performance and Vibratory Loads Data From a Wind-Tunnel Test of a Model Helicopter Main-Rotor Blade With a Paddle-Type Tip (1997)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation was conducted in the Langley Transonic Dynamics Tunnel to obtain data to permit evaluation of paddle-type tip technology for possible use in future U.S. advanced rotor designs. Data was obtained for both a baseline main-rotor blade and a main-rotor blade with a paddle-type tip. The baseline and paddle-type tip blades were compared with regard to rotor performance, oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Data was obtained in hover and forward flight over a nominal range of advance ratios from 0.15 to 0.425. Results indicate that the paddle-type tip offers no performance improvements in either hover or forward flight. Pitch-link oscillatory loads for the paddle-type tip are higher than for the baseline blade, whereas 4-per-rev vertical fixed-system loads are generally lower.
    Keywords: Aerodynamics
    Type: NASA-TM-4754 , L-17558 , NAS 1.15:4754 , ARL-TR-1283 , ATCOM-TR-97-A-006
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Wind-Tunnel Evaluation of the Effect of Blade Nonstructural Mass Distribution on Helicopter Fixed-System Loads (1998)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report provides data obtained during a wind-tunnel test conducted to investigate parametrically the effect of blade nonstructural mass on helicopter fixed-system vibratory loads. The data were obtained with aeroelastically scaled model rotor blades that allowed for the addition of concentrated nonstructural masses at multiple locations along the blade radius. Testing was conducted for advance ratios ranging from 0.10 to 0.35 for 10 blade-mass configurations. Three thrust levels were obtained at representative full-scale shaft angles for each blade-mass configuration. This report provides the fixed-system forces and moments measured during testing. The comprehensive database obtained is well-suited for use in correlation and development of advanced rotorcraft analyses.
    Keywords: Aircraft Design, Testing and Performance
    Type: NASA/TM-1998-206281 , NAS 1.15:206281 , ARL-TR-1401 , L-17353
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    Wind-tunnel evaluation of an advanced main-rotor blade design for a utility-class helicopter (1987)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation was conducted in the Langley Transonic Dynamics Tunnel to evaluate differences between an existing utility-class main-rotor blade and an advanced-design main-rotor blade. The two rotor blade designs were compared with regard to rotor performance oscillatory pitch-link loads, and 4-per-rev vertical fixed-system loads. Tests were conducted in hover and over a range of simulated full-scale gross weights and density altitude conditions at advance ratios from 0.15 to 0.40. Results indicate that the advanced blade design offers performance improvements over the baseline blade in both hover and forward flight. Pitch-link oscillatory loads for the baseline rotor were more sensitive to the test conditions than those of the advanced rotor. The 4-per-rev vertical fixed-system load produced by the advanced blade was larger than that produced by the baseline blade at all test conditions.
    Keywords: AERODYNAMICS
    Type: NASA-TM-89129 , L-16260 , NAS 1.15:89129 , AVSCOM-TM-87-B-8 , AD-A184574
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Vibratory Loads Data from a Wind-Tunnel Test of Structurally Tailored Model Helicopter Rotors (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental study was conducted in the Langley Transonic Dynamics Tunnel to investigate the use of a Bell Helicopter Textron (BHT) rotor structural tailoring concept, known as rotor nodalization, in conjunction with advanced blade aerodynamics as well as to evaluate rotor blade aerodynamic design methodologies. A 1/5-size, four-bladed bearingless hub, three sets of Mach-scaled model rotor blades were tested in forward flight from transition up to an advance ratio of 0.35. The data presented pertain only to the evaluation of the structural tailoring concept and consist of fixed-system and rotating system vibratory loads. These data will be useful for evaluating the effects of tailoring blade structural properties on fixed-system vibratory loads, as well as validating analyses used in the design of advanced rotor systems.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-TM-4265 , L-16873 , NAS 1.15:4265 , AVSCOM-TR-91-B-001 , AD-A239620
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    An experimental study of the sensitivity of helicopter rotor blade tracking to root pitch adjustment in hover (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The sensitivity of blade tracking in hover to variations in root pitch was examined for two rotor configurations. Tests were conducted using a four bladed articulated rotor mounted on the NASA-Army aeroelastic rotor experimental system (ARES). Two rotor configurations were tested: one consisting of a blade set with flexible fiberglass spars and one with stiffer (by a factor of five in flapwise and torsional stiffnesses) aluminum spars. Both blade sets were identical in planform and airfoil distribution and were untwisted. The two configurations were ballasted to the same Lock number so that a direct comparison of the tracking sensitivity to a gross change in blade stiffness could be made. Experimental results show no large differences between the two sets of blades in the sensitivity of the blade tracking to root pitch adjustments. However, a measurable reduction in intrack coning of the fiberglass spar blades with respect to the aluminum blades is noted at higher rotor thrust conditions.
    Keywords: AERONAUTICS (GENERAL)
    Type: NASA-TM-4313 , L-16939 , NAS 1.15:4313 , AVSCOM-TR-91-B-017 , AD-A243679
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 8
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    Reduction of blade-vortex interaction noise using higher harmonic pitch control (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An acoustics test using an aeroelastically scaled rotor was conducted to examine the effectiveness of higher harmonic blade pitch control for the reduction of impulsive blade-vortex interaction (BVI) noise. A four-bladed, 110 in. diameter, articulated rotor model was tested in a heavy gas (Freon-12) medium in Langley's Transonic Dynamics Tunnel. Noise and vibration measurements were made for a range of matched flight conditions, where prescribed (open-loop) higher harmonic pitch was superimposed on the normal (baseline) collective and cyclic trim pitch. For the inflow-microphone noise measurements, advantage was taken of the reverberance in the hard walled tunnel by using a sound power determination approach. Initial findings from on-line data processing for three of the test microphones are reported for a 4/rev (4P) collective pitch control for a range of input amplitudes and phases. By comparing these results to corresponding baseline (no control) conditions, significant noise reductions (4 to 5 dB) were found for low-speed descent conditions, where helicopter BVI noise is most intense. For other rotor flight conditions, the overall noise was found to increase. All cases show increased vibration levels.
    Keywords: ACOUSTICS
    Type: NASA-TM-101624 , AVSCOM-TM-89-B-005 , NAS 1.15:101624 , AD-A233833
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Performance Data from a Wind-Tunnel Test of Two Main-rotor Blade Designs for a Utility-Class Helicopter (1990)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An investigation was conducted in the NASA Langley Transonic Dynamics Tunnel to evaluate an advanced main rotor designed for use on a utility class helicopter, specifically the U.S. Army UH-60A Blackhawk. This rotor design incorporated advanced twist, airfoil cross sections, and geometric planform. For evaluation purposes, the current UH-60A main rotor was also tested and is referred to as the baseline blade set. A total of four blade sets were tested. One set of both the baseline and the advanced rotors were dynamically scaled to represent a full scale helicopter rotor blade design. The remaining advanced and baseline blade sets were not dynamically scaled so as to isolate the effects of structural elasticity. The investigation was conducted in hover and at rotor advance ratios ranging from 0.15 to 0.4 at a range of nominal test medium densities from 0.00238 to 0.009 slugs/cu ft. This range of densities, coupled with varying rotor lift and propulsive force, allowed for the simulation of several vehicle gross weight and density altitude combinations. Performance data are presented for all blade sets without analysis; however, cross referencing of data with flight condition may be useful to the analyst for validating aeroelastic theories and design methodologies as well as for evaluating advanced design parameters.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: NASA-TM-4183 , L-16736 , NAS 1.15:4183 , AVSCOM-TM-90-B-004
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Application of a PC based, real-time, data-aquisition system in rotorcraft wind-tunnel testing (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Data has been acquired for a rotocraft test in the NASA Langley Transonic Dynamics Tunnel using a desktop data acquisition system. The system, which consists of an IBM Personal Computer AT (PC-AT) and an Omega Engineering OM-900 Stand-Alone Interface System, is well suited for acquiring high speed data on a limited number of channels. The data acquisition system and the interrupt driven software which provides the capability for near real-time cyclic data acquisition as well as data storage and display are described.
    Keywords: COMPUTER SYSTEMS
    Type: NASA-TM-4119 , L-16565 , NAS 1.15:4119 , AVSCOM-TM-89-B-003 , AD-A213083
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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