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Author :
Publisher :
ISBN 13 :
Total Pages : 54 pages
Book Rating : 4.:/5 (317 download)
Download or read book An Experimental Investigation of Hingeless Helicopter Rotor-body Stability in Hover written by and published by . This book was released on 1978 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of the Aeromechanical Stability of a Hingeless Rotor in Hover and Forward Flight written by and published by . This book was released on 1987 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :
Publisher :
ISBN 13 :
Total Pages : 24 pages
Book Rating : 4.:/5 (317 download)
Download or read book An Experimental Investigation of the Aeromechanical Stability of a Hingeless Rotor in Hover and Forward Flight written by and published by . This book was released on 1987 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analysis and testing were conducted in the Langley Transonic Dynamics Tunnel to investigate the aeromechanical stability of a soft inplane hingeless rotor model. Rotor stability data were obtained in hover and in forward flight up to an advanced ratio of 0.35. Model rotor parameters evaluated were blade sweep and droop, pre-cone of the blade feathering axis, and blade pitch-flap coupling. Data obtained during these tests are presented without analysis. Keywords: Hovering; Hingeless helicopter rotor dynamics; Helicopter rotor blades; Ground resonance.
Author : David L. Sharpe
Publisher :
ISBN 13 :
Total Pages : 92 pages
Book Rating : 4.:/5 (317 download)
Download or read book An Experimental Investigation of the Flap-lag-torsion Aeroelastic Stability of a Small-scale Hingeless Helicopter Rotor in Hover written by David L. Sharpe and published by . This book was released on 1986 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: A small scale, 1.92 m diam torsionally soft, hingeless helicopter rotor was investigated in hover to determine isolated rotor stability characteristics. The two-bladed, untwisted rotor was tested on a rigid test stand at tip speeds up to 101 m/sec. The rotor mode of interest in this investigation was the lightly damped lead-lag mode. The dimensionless lead-lag frequency of the mode is approximately 1.5 at the highest tip speed. The hub was designed to allow variation in precone, blade droop, pitch control stiffness, and blade pitch angle. Measurements of modal frequency and damping were obtained for several combinations of these hub parameters at several values of rotor speed. Steady blade bending moments were also measured. The lead-lag damping measurements were found to agree well with theoretical predictions for low values of blade pitch angle. The test data confirmed the predicted effects of precone, droop, and pitch control stiffness parameters on lead-lag damping. The correlation between theory and experiment was found to be poor for the mid-to-high range of pitch angles where the theory substantially overpredicted the experimental lead-lag damping. The poor correlation in the mid-to-high blade pitch angle range is attributed to low Reynolds number nonlinear aerodynamics effects not included in the theory. The experimental results also revealed an asymmetry in lead-lag damping between positive and negative thrust conditions. Investigations of the rotor induced velocity field suggest that the asymmetry in lead-lag damping is not caused by the aerodynamic inflow but more likely from the influence of blade weight on the equilibrium blade deflection.
Author : H. C. Curtiss
Publisher :
ISBN 13 :
Total Pages : 26 pages
Book Rating : 4.:/5 (641 download)
Download or read book An Experimental Investigation of the Flap-lag Stability of a Hingeless Rotor with Comparable Levels of Hub and Blade Stiffness in Hovering Flight written by H. C. Curtiss and published by . This book was released on 1976 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : William T. Yeager
Publisher :
ISBN 13 :
Total Pages : 16 pages
Book Rating : 4.:/5 (977 download)
Download or read book An Experimental Investigation of the Aeromechanical Stability of a Hingeless Rotor in Hover and Forward Flight written by William T. Yeager and published by . This book was released on 1987 with total page 16 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Robert A. Ormiston
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (227 download)
Download or read book A Theoretical and Experimental Investigation of Flap-Lag Stability of Hingeless Helicopter Rotor Blades written by Robert A. Ormiston and published by . This book was released on 1972 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: A substantial insight into the fundamental stability characteristics of the hingeless rotor may be obtained by considering only the flap and lead-lag degrees of freedom of a single blade. Although portions of this problem have been examined in previous research, the effects of may basic rotor parameters are poorly understood. The present study was undertaken to provide a rigorous formulation of the problem, and to systematically investigate the important parameters which characterize actual hingeless rotor blade configurations. In the absence of available experimental data a model rotor was designed and tested to validate the theoretical analysis. (Author).
Author : Thomas C. Suermann
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (81 download)
Download or read book An Experimental Investigation of Structural Characteristics of Hingeless Helicopter Rotors with Respect to Flap-lag Stability written by Thomas C. Suermann and published by . This book was released on 1975 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : James L. Tangler
Publisher :
ISBN 13 :
Total Pages : 92 pages
Book Rating : 4.:/5 (31 download)
Download or read book An Experimental Investigation of Vortex Stability, Tip Shapes, Compressibility, and Noise for Hovering Model Rotors written by James L. Tangler and published by . This book was released on 1973 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Charles Arthur Vehlow
Publisher :
ISBN 13 :
Total Pages : 105 pages
Book Rating : 4.:/5 (227 download)
Download or read book Experimental Investigation of Gust Response of Hingeless Helicopter Rotors written by Charles Arthur Vehlow and published by . This book was released on 1977 with total page 105 pages. Available in PDF, EPUB and Kindle. Book excerpt: The response to wind gusts of a 1/10-scale hingeless helicopter rotor model in hovering and forward flight is studied experimentally through wind tunnel testing. The experimental program involving design, construction, and testing of a five-foot-diameter rotor utilizing either three NACA 0012 planform blades or one operable blade with two dummy blades is described. The rotor design is such that the the torsional stiffness of the blade assembly as well as the blade chordwise center-of-gravity location can be varied during the various phases of the test. Wind tunnel testing incorporates the variation of wind tunnel speed and the application of variable frequency, sinusoidal waveform gusts. The flap, lag, and torsional response of the rotor in its various configurations was measured and compared with theoretical predictions. (Author).
Author : National Aeronautics and Space Administration (NASA)
Publisher : Createspace Independent Publishing Platform
ISBN 13 : 9781723454912
Total Pages : 26 pages
Book Rating : 4.4/5 (549 download)
Download or read book Hover Test of a Full-Scale Hingeless Rotor written by National Aeronautics and Space Administration (NASA) and published by Createspace Independent Publishing Platform. This book was released on 2018-07-24 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance and aeroelastic stability in hover of a 9.8-m diameter, hingeless helicopter rotor system was evaluated. Rotor performance and inplane damping data were obtained for rotor operation between 350 and 425 rpm for thrust coefficients (CT/sigma) between 0.0 and 0.12. At constant rotor thrust, a minimum in rotor inplane damping was measured at 400 rpm. Good agreement is shown between experimental performance data and predicted performance. The influence of different aerodynamic inflow models on predicting damping levels is also shown. The best correlation with experimental stability data was obtained when a dynamic inflow model was used instead of static or quasistatic inflow models. Comparison with other full scale, hingeless rotor data in hover is presented. The hingeless rotor data and data from a full scale, bearingless main rotor test performed on the same general purpose test apparatus were compared. Although the bearingless rotor was more highly damped at design tip speed and 1-g thrust operation, greater sensitivity to operating conditions is shown. At low thrust levels the bearingless main rotor is less damped than the hingeless rotor. Warmbrodt, W. and Peterson, R. L. Ames Research Center NASA-TM-85990, A-9827, NAS 1.15:85990 RTOP 532-06-11
Author :
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ISBN 13 :
Total Pages : 1460 pages
Book Rating : 4.:/5 (31 download)
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 1460 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Author : William G. Bousman
Publisher :
ISBN 13 :
Total Pages : 14 pages
Book Rating : 4.:/5 (227 download)
Download or read book An Experimental Investigation of the Effects of Aeroelastic Couplings on Aeromechanical Stability of a Hingeless Rotor Helicopter written by William G. Bousman and published by . This book was released on 1980 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: A 1.62-m diameter rotor model was used to investigate aeromechanical stability, and the results were compared to theory. Configurations tested included: (1) a nonmatched stiffness rotor as a baseline, (2) the baseline rotor with negative pitch-lag coupling, (3) the combination of negative pitch-lag and structural flap-lag coupling on the baseline rotor, (4) a matched stiffness rotor, and (5) a matched stiffness rotor with negative pitch-lag coupling. The measured lead-lag regressing mode damping of the five configurations agreed well with theory, but only the matched stiffness case with negative pitch-lag coupling was able to stabilize the air resonance mode. Comparison of theory and experiment for the damping of the body modes showed significant differences that may be related to rotor inflow dynamics. (Author).
Author : Julian L. Jenkins (Jr.)
Publisher :
ISBN 13 :
Total Pages : 44 pages
Book Rating : 4.:/5 (31 download)
Download or read book Investigation of Level-flight and Maneuvering Characteristics of a Hingeless-rotor Compound Helicopter written by Julian L. Jenkins (Jr.) and published by . This book was released on 1970 with total page 44 pages. Available in PDF, EPUB and Kindle. Book excerpt: Flight tests on hingeless rotor compound helicopter to determine level flight and maneuvering characteristics.
Author :
Publisher :
ISBN 13 :
Total Pages : 24 pages
Book Rating : 4.:/5 (317 download)
Download or read book Aeromechanical Stability of a Hingeless Rotor in Hover and Forward Flight: Analysis and Wind Tunnel Tests written by and published by . This book was released on 1983 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt: A research effort of analysis and testing has been conducted in the NASA-Langley Transonic Dynamics Tunnel to investigate the ground resonance phenomenon of a soft in-plane hingeless rotor. Experimental data were obtained using a 9 ft. (2.74 m) diameter model rotor in hover and forward flight. Eight model rotor configurations were investigated. Configuration parameters included pitch-flap coupling, blade sweep and droop, and precone of the blade feathering axis. An analysis based on a comprehensive analytical model of rotorcraft aerodynamics and dynamics was used for this study. The moving-block method was used to experimentally determine the regressing lead-lag mode damping. Good agreement has been obtained between the analysis and test. Both analysis and experiment indicated ground resonance instability in hover. The paper presents an outline of the analysis, a description of the experimental model and procedures, and comparison of the analytical and experimental data. (Author).
Author : Peretz Friedmann
Publisher :
ISBN 13 :
Total Pages : 40 pages
Book Rating : 4.:/5 (317 download)
Download or read book Investigation of Some Parameters Affecting the Stability of a Hingeless Helicopter Blade in Hover written by Peretz Friedmann and published by . This book was released on 1972 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : United States. National Aeronautics and Space Administration
Publisher :
ISBN 13 :
Total Pages : 380 pages
Book Rating : 4.3/5 (91 download)
Download or read book NASA Technical Paper written by United States. National Aeronautics and Space Administration and published by . This book was released on 1990 with total page 380 pages. Available in PDF, EPUB and Kindle. Book excerpt:
