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  • 1
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    Demonstration of an elastically coupled twist control concept for tilt rotor blade application (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The purpose of this Note is to present results from an analytic/experimental study that investigated the potential for passively changing blade twist through the use of extension-twist coupling. A set of composite model rotor blades was manufactured from existing blade molds for a low-twist metal helicopter rotor blade, with a view toward establishing a preliminary proof concept for extension-twist-coupled rotor blades. Data were obtained in hover for both a ballasted and unballasted blade configuration in sea-level atmospheric conditions. Test data were compared with results obtained from a geometrically nonlinear analysis of a detailed finite element model of the rotor blade developed in MSC/NASTRAN.
    Keywords: AERODYNAMICS
    Type: AIAA Journal (ISSN 0001-1452); 32; 7; p. 1549-1551
    Format: text
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    NASA TECHNICAL REPORTS
  • 2
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    Demonstration of an elastically coupled twist control concept for tilt rotor blade application (1994)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: This study demonstrated the feasibility of passive blade twist control for composite rotor blades. Hover testing of the set of blades produced maximum twist changes of 2.54 degrees for the unballasted blade configuration and 5.24 degrees for the ballasted blade configuration. These results compared well with those obtained from a detailed finite element analysis model of the rotor blade, which yielded maximum twists of 3.02 and 5.61 degrees for the unballasted and ballasted blade configurations, respectively.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA Journal (ISSN 0001-1452); 32; 7; p. 1549-1551
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Control load envelope shaping by live twist (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Rotor control systems experience a rapid load growth resulting from retreating blade stall during flight conditions of high blade loading or airspeeds. An investigation was undertaken to determine the effect of changing blade torsional properties over the rotor flight envelope. The results of this study show that reducing the blade stiffness to introduce more blade live twist significantly reduces the large retreating blade control loads, while expanding the flight envelope and reducing retreating blade stall loads.
    Keywords: AIRCRAFT
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 115-125
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Dynamic stall modeling and correlation with experimental data on airfoils and rotors (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Two methods for modeling dynamic stall have been developed. The alpha, A, B method generates lift and pitching moments as functions of angle of attack and its first two time derivatives. The coefficients are derived from experimental data for oscillating airfoils. The Time Delay Method generates the coefficients from steady state airfoil characteristics and an associated time delay in stall beyond the steady state stall angle. Correlation with three types of test data shows that the alpha, A, B method is somewhat better for use in predicting helicopter rotor response in forward flight. Correlation with lift and moment hysteresis loops generated for oscillating airfoils was good for both models.
    Keywords: AIRCRAFT
    Type: NASA. Ames Res. Center Rotorcraft Dyn.; p 13-23
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 5
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    A demonstration of passive blade twist control using extension-twist coupling (1992)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The feasibility of passive blade twist control using an extension-twist-coupled composite rotor blade design has been demonstrated. A set of low-twist model-scale helicopter rotor blades has been manufactured from existing molds with the objective of demonstrating this control concept. Hover testing of the set of blades demonstrated maximum twist changes of 5.24 deg for the ballasted blade configuration, and 2.54 deg for the unballasted configurations in the atmospheric test condition. These results compared well with those obtained from a detailed FEM analysis of the rotor blade. Aerodynamic-induced effects on the blade elastic twist were found to be minimal.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
    Type: AIAA PAPER 92-2468 , AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference; Apr 13, 1992 - Apr 15, 1992; Dallas, TX; United States
    Format: text
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