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  • 1
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    Experimental hingeless rotor characteristics at low advance ratio with thrust (1973)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An experimental investigation to determine the dynamic characteristics of a hingeless rotor operating at moderate to high lift was conducted on a small scale, 7.5-foot diameter, four-bladed hingeless rotor model in a 7 x 10-foot wind tunnel. The primary objective of this research program was the empirical determination of the rotor steady-state and frequency responses to swashplate and body excitations. Collective pitch was set from 0 to 20 degrees, with the setting at a particular advance ratio limited by the cyclic pitch available for hub moment trim. Advance ratio varied from 0.00 to 0.36 for blades with nondimensional first-flap frequencies at 1.15, 1.28 and 1.33 times the rotor rotation frequency. Several conditions were run with the rotor operating in the transition regime. Rotor response at high lift is shown to be generally nonlinear in this region. As a secondary objective an experimental investigation of the rotor response to 4/revolution swashplate excitations at advance ratios of 0.2 to 0.85 and at a nondimensional, first-flap modal frequency of 1.34 was also conducted, using the 7 x 10-foot wind tunnel. It is shown that 4/revolution swashplate inputs are a method for substantially reducing rotor-induced, shafttransmitted vibratory forces.
    Keywords: AIRCRAFT
    Type: NASA-CR-114684
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Vibration and loads in hingeless rotors. Volume 1: Theoretical analyses (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Analytic methods are developed for calculating blade loads and shaft-transmitted vibratory forces in stiff bladed hingeless rotors operating at advance ratios from mu = .3 to mu = 2.0. Calculated shaft harmonic moments compared well with experimental values when the blade first flap frequency was in the region of two-per-revolution harmonic excitation. Calculated blade bending moment azimuthal distributions due to changes in cyclic pitch agreed well with experiment at radial stations near the blade root at values of the ratio of first flap frequency to rotor rotation rate from 1.5 to 5.0. At stations near the blade tip good agreement was only obtained at the higher values of frequency ratio.
    Keywords: AIRCRAFT
    Type: NASA-CR-114562
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Vibration and loads in hingeless rotors. Volume 2: Experimental data (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Descriptions, geometry, and technical data covering three rotor systems are presented. Tables of experimental data gathered during wind tunnel testing of two of the systems are included. Both analyzed experimental data, ready for comparison with theory, and the basic reduced data from which they were obtained are reported.
    Keywords: AIRCRAFT
    Type: NASA-CR-114568
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Hingeless rotor vibration and loads at high advance ratio (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Experimental values of mean and oscillatory shaft force aeroelastic derivatives with respect to cyclic pitch are presented in dimensionless coefficient form for stiff-bladed hingeless rotors operating at high advance ratio. Good agreement with theory is obtained for the 2P components, in rotating axes, of the oscillatory hub moment derivatives. Trends were predicted for the mean components. Experimental plots of the azimuthal distribution of blade flap bending moment due to cyclic pitch are compared with theoretical for high values of flap frequency ratio and advance ratio. Good agreement is found near the blade root. The similarity parameters that should be preserved in the scale model testing of stiff-bladed hingeless rotors at high advance ratio are reviewed, and some aspects of hingeless rotor wind tunnel testing are considered.
    Keywords: AIRCRAFT
    Type: Mideast Region Symposium; Oct 26, 1972 - Oct 28, 1972; Essington, PA
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Dynamics of a rigid-rotor controlled by a high- speed gyro as it slows/stops at high forward speed. (1969)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Gyro controlled rigid rotor dynamic stability studied for stoppable rotor operation, developing analytical expressions for determining stability boundary of constant and rotor speed gyros
    Keywords: AIRCRAFT
    Type: AHS PAPER 343 , AMERICAN HELICOPTER SOCIETY, ANNUAL NATIONAL FORUM; May 14, 1969 - May 16, 1969; WASHINGTON, DC
    Format: text
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  • 6
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    Horizontal stoppable rotor conversion (1971)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Stiffened horizontal stoppable hingeless rotor conversion from helicopter to airplane flight speeds
    Keywords: AIRCRAFT
    Type: AHS PREPRINT 502 , ANNUAL NATIONAL V/STOL FORUM; May 19, 1971 - May 21, 1971; WASHINGTON, DC
    Format: text
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    NASA TECHNICAL REPORTS
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