Download or read book NH 3A Vibratory Airloads and Vibratory Rotor Loads written by United Aircraft Corporation. Sikorsky Aircraft Division and published by . This book was released on 1970 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Rotorcraft Dynamics 1984 written by and published by . This book was released on 1985 with total page 518 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Reference Publication written by and published by . This book was released on 1977 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tip Aerodynamics and Acoustics Test written by Jeffrey L. Cross and published by . This book was released on 1988 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Vertica written by and published by . This book was released on 1984 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1983 with total page 1252 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book NASA Army Rotorcraft Technology Volume 1 Aerodynamics and Dynamics and Aeroelasticity written by and published by . This book was released on 1988 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Response of Helicopter Rotors to Vibratory Airload written by and published by . This book was released on 1989 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Structural response data from flight or wind tunnel tests of eight full-scale rotors were examined and compared for high-speed flight conditions and in the absence of blade stall or maneuvers. Both similarities and differences in the behavior of the rotors were observed, and these findings are useful in determining appropriate tests for development of theoretical methods. Limited use is made of airload measurements and theoretical calculation in examining these data. Major similarities observed in the rotor behavior include: 1) 3/rev vibratory flap bending moments are remarkably similar among all the rotors at high speed; 2) the root oscillatory chord bending induced by lag dampers is similar for three of the articulated rotors despite differences in the damper type; and 3) torsion moment and pitch-link loads show same positive- negative loading over the advancing side of the disk caused by the unsteady pitching moments at the blade tip. Differences that were observed include: 1) the vibratory chord bending-moment behavior appears to be dependent on rotor stiffness in part, but differences seen are not easily explained; 2) the CH-53A root oscillatory chord bending-moment data do not show the damper-induced loads that are seen on the other articulated rotors with hydraulic lag dampers; and 3) the AH-1G torsion response is very different from that of the articulated rotors. Rotor blades; Rotary wings. (edc).
Download or read book Wake Model for Helicopter Rotors in High Speed Flight written by and published by . This book was released on 1988 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tip Aerodynamics and Acoustics Test written by J. L. Cross and published by . This book was released on 1988 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Helicopter Control Loads Induced by Stall Flutter written by P. J. Arcidiacono and published by . This book was released on 1970 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: An analytical study was conducted to determine if available unsteady normal force and moment aerodynamic test data could be used in conjunction with existing helicopter rotor aeroelastic and variable inflow analyses to provide a method for predicting the stall flutter response of a helicopter rotor blade. For this purpose, incompressible unsteady aerodynamic data for an NACA 0012 airfoil executing pure sinusoidal pitching motions were employed. To apply such data under rotor blade operating conditions where multiharmonic motions and velocity variations exist, the data were expressed as functions of instantaneous section angle of attack, angular velocity, and angular acceleration. In addition, scaling procedures were developed in an attempt to account for the effects of compressibility. Limited application of the resulting analysis to define the aeroelastic characteristics of several blade designs showed that significant self-excited torsional oscillations of the stall flutter type could, in fact, be predicted for certain combinations of flight conditions and blade designs. Correlation studies, to evaluate the ability of the analysis to predict control loads, were performed with CH-53A maneuvering flight test data and with level flight test data from the NH-3A (S-61F). (Author).
Download or read book Optimizing Tuning Masses for Helicopter Rotor Blade Vibration Reduction Including Computed Airloads and Comparison with Test Data written by and published by . This book was released on 1992 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Rotor Vibratory Loads Using Higher Harmonic Pitch Control written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-06 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt: Experimental studies of isolated rotors in forward flight have indicated that higher harmonic pitch control can reduce rotor noise. These tests also show that such pitch inputs can generate substantial vibratory loads. The modification is summarized of the RotorCRAFT (Computation of Rotor Aerodynamics in Forward flighT) analysis of isolated rotors to study the vibratory loading generated by high frequency pitch inputs. The original RotorCRAFT code was developed for use in the computation of such loading, and uses a highly refined rotor wake model to facilitate this task. The extended version of RotorCRAFT incorporates a variety of new features including: arbitrary periodic root pitch control; computation of blade stresses and hub loads; improved modeling of near wake unsteady effects; and preliminary implementation of a coupled prediction of rotor airloads and noise. Correlation studies are carried out with existing blade stress and vibratory hub load data to assess the performance of the extended code. Quackenbush, Todd R. and Bliss, Donald B. and Boschitsch, Alexander H. and Wachspress, Daniel A. Unspecified Center...
Download or read book The Aeronautical Journal written by and published by . This book was released on 1997 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Journal of the American Helicopter Society written by and published by . This book was released on 1993 with total page 1112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Higher Harmonic Control Analysis for Vibration Reduction of Helicopter Rotor Systems written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-17 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: An advanced higher harmonic control (HHC) analysis has been developed and applied to investigate its effect on vibration reduction levels, blade and control system fatigue loads, rotor performance, and power requirements of servo-actuators. The analysis is based on a finite element method in space and time. A nonlinear time domain unsteady aerodynamic model, based on the indicial response formulation, is used to calculate the airloads. The rotor induced inflow is computed using a free wake model. The vehicle trim controls and blade steady responses are solved as one coupled solution using a modified Newton method. A linear frequency-domain quasi-steady transfer matrix is used to relate the harmonics of the vibratory hub loads to the harmonics of the HHC inputs. Optimal HHC is calculated from the minimization of the vibratory hub loads expressed in term of a quadratic performance index. Predicted vibratory hub shears are correlated with wind tunnel data. The fixed-gain HHC controller suppresses completely the vibratory hub shears for most of steady or quasi-steady flight conditions. HHC actuator amplitudes and power increase significantly at high forward speeds (above 100 knots). Due to the applied HHC, the blade torsional stresses and control loads are increased substantially. For flight conditions where the blades are stalled considerably, the HHC input-output model is quite nonlinear. For such cases, the adaptive-gain controller is effective in suppressing vibratory hub loads, even though HHC may actually increase stall areas on the rotor disk. The fixed-gain controller performs poorly for such flight conditions. Comparison study of different rotor systems indicates that a soft-inplane hingeless rotor requires less actuator power at high speeds (above 130 knots) than an articulated rotor, and a stiff-inplane hingeless rotor generally requires more actuator power than an articulated or a soft-inplane hingeless rotor. Parametric studies for a hingeless rotor operati...
Download or read book NASA Conference Publication written by and published by . This book was released on 1988 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt:
