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V/STOL Dynamics and Aeroelastic Rotor - Airframe Technology. Volume 2. Description and Correlation of New Methodologies

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Final rept. Feb 1971-Feb 1972

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The blade loads analysis calculates rotor blade flapwise, chordwise, and torsional deflections and loads, together with rotor performance, control system forces, and vibratory hub loads. Articulated and hingeless rotors with 2 to 9 blades and large twist may be analyzed. The analysis considers coupled flapwise-chordwise-torsion deflections of the rotor blades. Boundary conditions for either articulated or hingeless rotors are applied and the solution is obtained by expanding the variables in a 10-harmonic Fourier series. Airload calculations include the effects of airfoil section geometry, compressibility, stall, 3-dimensional flow, unsteady aerodynamics, and nonuniform inflow. In the area of rotor loads, correlation of proprotor and helicopter rotor loads test data has been made with the fully coupled rotor loads and steady in-plane hub moments for proprotors and for alternating blade loads, pitch link loads, and airloads for helicopters. An unexpected discovery of this study was the sensitivity of the rotor derivatives to blade lead-lag motion when the frequency of this mode is near 1 per rev. This result was subsequently confirmed by test. The impact of the new prediction capabilities and possible refinement or development of design criteria through use of the analysis are discussed. The methods contained in this report are intended to be used by designers to calculate with improved accuracy, the dynamic and aeroelastic response characteristics of rotor powered VSTOL aircraft. The essential new feature of these methods is that the coupled flap-pitch-lag blade deflections are taken into account. These calculations are essential if a high level of confidence is to be had in the results.

Subject Categories:

  • Aerodynamics
  • Helicopters

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