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Flight Measurements of Helicopter Blade Motion With a Comparison Between Theoretical and Experimental Results

Description: Note presenting photographic records of the behavior of a blade in flight as obtained with a conventional single-rotor helicopter. The results of the measurements of flapping motion, in-plane motion, and blade distortions are presented for selected conditions of flight at tip-speed ratios ranging from 0.12 to 0.25. Plots of blade twisting and blade bending in the plane of flapping are presented for a sample case.
Date: April 1947
Creator: Myers, Garry C., Jr.
Partner: UNT Libraries Government Documents Department
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Flight Tests of a Helicopter in Autorotation, Including a Comparison With Theory

Description: Note presenting the results of glide performance tests conducted on a test helicopter with its original production blades in the autorotation condition. The data was reduced to coefficient form, and performance at standard sea-level conditions were calculated.
Date: April 1947
Creator: Gessow, Alfred & Myers, Garry C., Jr.
Partner: UNT Libraries Government Documents Department
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Airfoil Section Data From Tests of 10 Practical-Construction Sections of Helicopter Rotor Blades Submitted by the Sikorsky Aircraft Division, United Aircraft Corporation

Description: Report presenting 10 practical-construction models of sections of helicopter rotor blades tested in the NACA two-dimensional low-turbulence pressure tunnel at atmospheric pressure. Lift, drag, and pitching-moment characteristics of blades representing the present method of construction of the YR-4A helicopter were determined.
Date: September 1944
Creator: Tetervin, Neal
Partner: UNT Libraries Government Documents Department
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Response of a helicopter rotor to oscillatory pitch and throttle movements

Description: Report presenting an analysis of the measurements of drag-angle oscillation of a helicopter rotor made with the helicopter apparatus to determine both the natural frequencies and the damping required to prevent excessive drag-angle-oscillation response to various throttle and control movements. Results regarding symmetrical oscillations, unsymmetrical oscillations, blade damping, and general discussion are provided.
Date: June 1949
Creator: Carpenter, Paul J. & Peitzer, Herbert E.
Partner: UNT Libraries Government Documents Department
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An introduction to the physical aspects of helicopter stability

Description: "In order to provide engineers interested in rotating-wing aircraft but with no specialized training in stability theory some understanding of the factors that influence the flying qualities of the helicopter, an explanation is made of both the static stability and the stick-fixed oscillation in hovering and forward flight in terms of fundamental physical qualities. Three significant stability factors - static stability with angle of attack, static stability with speed, and damping due to a pit… more
Date: November 1949
Creator: Gessow, Alfred & Amer, Kenneth B.
Partner: UNT Libraries Government Documents Department
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An Analysis of the Transition of a Helicopter From Hovering to Steady Autorotative Vertical Descent

Description: "This report is the second phase of a broad program of study of the transient motions of helicopters in autorotative flight. The first phase (reference 1) dealt with the steady-state condition of autorotative vertical descent. This report is concerned with the the transition from the steady condition of hovering to the steady autorotative descent" (p. 1).
Date: June 1949
Creator: Nikolsky, A. A. & Seckel, Edward
Partner: UNT Libraries Government Documents Department
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Two-dimensional investigation of five related NACA airfoil sections designed for rotating-wing aircraft

Description: Report presenting testing of five NACA airfoil sections intended for use in rotor blades in the two-dimensional low-turbulence tunnel. The airfoils varied in thickness and theoretical design lit coefficients. Results regarding pitching moment, lift, drag, and helicopter performance calculations are provided.
Date: July 1949
Creator: Schaefer, Raymond F.; Loftin, Laurence K., Jr. & Horton, Elmer A.
Partner: UNT Libraries Government Documents Department
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Analysis of Flight-Performance Measurements on a Twisted, Plywood-Covered Helicopter Rotor in Various Flight Conditions

Description: From Introduction: "In references 1, 2, and 3, flight measurements of the performance of a conventional, single-rotor helicopter equipped with its production fabric-covered main rotor blades are presented."
Date: June 1948
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
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Full-scale investigation of the aerodynamic characteristics of a typical single-rotor helicopter in forward flight

Description: Report presenting an investigation of the forward-flight performance characteristics of a typical single-rotor helicopter equipped with main and tail rotors. Testing occurred over a range of tip-speed ratios and thrust coefficients. Results regarding the fuselage effects and rotor characteristics are provided.
Date: May 1947
Creator: Dingeldein, Richard C. & Schaefer, Raymond F.
Partner: UNT Libraries Government Documents Department
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Effect of blade stalling on the efficiency of a helicopter rotor as measured in flight

Description: Report presenting performance data on a helicopter rotor in flight over a range of combinations of thrust coefficient and tip-speed ratios, which included combinations intended to result in blade stalling. The study indicated that calculated angle of attack of the retreating tip should be a useful parameter for adequately defining the conditions at which stalling losses set in for a range of combinations of thrust coefficient and tip-speed ratio.
Date: April 1947
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department
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On the flying qualities of helicopters

Description: Report presenting the flying qualities problems of current helicopters, including instability with angle of attack in forward flight, control sensitivity in hovering, and control forces following control movement in maneuvers. Some possible solutions to these issues are presented.
Date: January 27, 1949
Creator: Reeder, John P. & Gustafson, F. B.
Partner: UNT Libraries Government Documents Department
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Longitudinal flying qualities of several single-rotor helicopters in forward flight

Description: Report presenting flight-test measurements and corresponding pilot's opinions of the forward-flight longitudinal flying qualities characteristics of several single-rotor helicopters. The most important consideration for satisfactory characteristics appears to be the prevention of prolonged stick-fixed divergent tendencies. Results regarding the characteristics appreciated, theoretical analysis of pull-up characteristics, and practical requirements are provided.
Date: November 1949
Creator: Gustafson, F. B.; Amer, Kenneth B.; Haig, C. R. & Reeder, J. P.
Partner: UNT Libraries Government Documents Department
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Charts Showing Relations Among Primary Aerodynamic Variables for Helicopter-Performance Estimation

Description: "In order to facilitate solutions of the general problem of helicopter selection, the aerodynamic performance of rotors is presented in the form of charts showing relations between primary design and performance variables. By the use of conventional helicopter theory, certain variables are plotted and other variables are considered fixed. Charts constructed in such a manner show typical results, trends, and limits of helicopter performance" (p. 1).
Date: February 1947
Creator: Talkin, Herbert W.
Partner: UNT Libraries Government Documents Department
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Effect of wind velocity on performance of helicopter rotors as investigated with the Langley helicopter apparatus

Description: Report presenting testing of two representative helicopter rotors with widely different characteristics to determine the effect of wind velocity on the power required for sustentation. An appreciable decrease in power required for both rotors for a given thrust as the wind velocity increased was noted. The results for the rotors were essentially the same even though the rotors had different plan forms, airfoil sections, blade twists, and solidities.
Date: October 1948
Creator: Carpenter, Paul J.
Partner: UNT Libraries Government Documents Department
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Standard Symbols for Helicopters

Description: "A list of standard symbols for rotating-wing aircraft is presented. The list of symbols is subdivided for ready reference under appropriate headings, the symbols being restricted to those most generally used in studies of helicopter aerodynamics" (p. 1).
Date: June 1948
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
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Analysis of Ground Effect on the Lifting Airscrew

Description: "A study is presented of ground effect as applied to the lifting airscrew of the type used in modern gyroplanes and helicopters. The mathematical analysis of the problem has been verified by tests made of three rotor models in the presence of a large circular "ground plane." The results of the study are presented in the form of convenient charts" (p. 1).
Date: December 1941
Creator: Knight, Montgomery & Hefner, Ralph A.
Partner: UNT Libraries Government Documents Department
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Full-Scale Investigation of the Blade Motion of the PV-2 Helicopter Rotor

Description: Note presenting an investigation of the PV-2 helicopter rotor to determine the basic performance characteristics of a fully articulated rotor. Results are presented of the blade-motion observations at the 0.75-radius station for a limited range of flight conditions. Both the measured results and a comparison with theoretical results are provided.
Date: March 1948
Creator: Migotsky, Eugene
Partner: UNT Libraries Government Documents Department
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Effect of Rotor-Blade Twist and Plan-Form Taper on Helicopter Hovering Performance

Description: Note presenting a theoretical analysis of the hovering performance of rotors with various combinations of twist and plan-form taper in order to estimate the effects of blade twist and taper on rotor efficiency in hovering. The calculations were made with the aid of a strip-analysis procedure similar to that used in propeller analysis, the comparisons being made for rotors of equal solidity.
Date: February 1948
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
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Flight Investigation of Effects of Rotor-Blade Twist on Helicopter Performance in the High-Speed and Vertical-Autorotative-Descent Conditions

Description: Note presenting flight-performance measurements made on an untwisted, plywood-covered rotor in the high-speed and vertical-autorotative-descent conditions. The results were compared with measurements on a similar rotor with 8 degrees of linear washout and with theoretical calculations in order to determine the effects of rotor-blade twist on helicopter performance.
Date: August 1948
Creator: Gessow, Alfred
Partner: UNT Libraries Government Documents Department
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A Theoretical Study of the Dynamic Properties of Helicopter-Blade Systems

Description: Note presenting a theoretical study of the dynamic properties of lifting rotors, which includes the derivatives of the angles of attack of the inflow, blade-position variables, and aerodynamic and inertia forces, the development and solution of the equilibrium conditions of the blade system in the hovering and traveling states, and the development of the frequency, stability, and damping properties of the blades during hovering and traveling.
Date: November 1948
Creator: Reissner, H. & Morduchow, M.
Partner: UNT Libraries Government Documents Department
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Helicopter Stability

Description: Report presenting information about some of the fundamental concepts and lines of development that may be undertaken regarding helicopter stability. Some of the principles discussed include method of control, control lag, stability characteristics, control forces, and center of gravity. Some of the means for improvement discussed include use of a horizontal stabilizer, use of trim devices, use of power-operated controls, automatic controls, and choice and grouping of indicating instruments.
Date: April 12, 1948
Creator: Gustafson, F. B. & Reeder, J. P.
Partner: UNT Libraries Government Documents Department
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Comparison of Hovering Performance of Helicopters Powered by Jet-Propulsion and Reciprocating Engines

Description: Report presenting an investigation of the maximum hovering time, or the time that a helicopter can sustain itself without motion, for helicopters using a reciprocating engine, by ramjet engines at the tips of rotor blades, and by pulse-jet engines at the tips of rotor blades. Testing showed that the reciprocating engine permitted much longer hovering time than the jet-propulsion engines, but the jet-propulsion engines were much lighter and could lift greater disposable loads.
Date: June 11, 1948
Creator: Brightwell, Virginia L.; Peters, Max D. & Sanders, J. C.
Partner: UNT Libraries Government Documents Department
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A Preliminary Theoretical Study of Aerodynamic Instability of a Two-Blade Helicopter Rotor

Description: Report presenting numerical results of flutter calculations for a two-blade helicopter using a see-saw-type rotor. The stability condition for oscillatory motion is expressed in terms of a small number of composite parameters that are evaluated from moments of inertia, angle settings, and aerodynamic parameters of a blade. The analysis indicated that a see-saw rotor with a coning angle is more unstable than an airplane wing with the same parameters.
Date: March 18, 1947
Creator: Coleman, Robert P. & Stempin, Carl W.
Partner: UNT Libraries Government Documents Department
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