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Wings of the Future

Description: This film discusses helicopters and looks at how inventors and innovators like Igor Sikorsky, Juan de la Cierva and Arthur Young helped to make helicopter flight possible.
Date: unknown
Partner: UNT Media Library

Experimental investigation on the Langley helicopter test tower of compressibility effects on a rotor having NACA 63(sub 2)-015 airfoil sections

Description: Report presenting an investigation in the helicopter test tower to determine experimentally the effects of compressibility on the hovering performance and blade pitching moments of a helicopter rotor with NACA 63(sub 2)-015 airfoil sections. The results indicated that two-dimensional airfoil-section data provide a reasonable basis for predicting the onset of compressibility losses and that the differences in Mach number for drag divergence between airfoils shown by two-dimensional data are realized in rotor tests.
Date: December 1956
Creator: Shivers, James P. & Carpenter, Paul J.
Partner: UNT Libraries Government Documents Department

Analysis of a Pressure-Jet Power Plant for Helicopter

Description: From Introduction: "In comparison with the shaft-driven rotor, the jet rotor is shown in references 1 and 2 to provide direct reductions in helicopter empty weight and to increase the pay-load capacity by (1) eliminating the gear-reduction train between the rotor shaft and the power plant, (2) eliminating the antitorque tail rotor, and (3) using a power plant of low specific weight."
Date: March 28, 1955
Creator: Krebs, Richard P. & Miller, William S., Jr.
Partner: UNT Libraries Government Documents Department

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

Full-scale investigation of aerodynamic characteristics of a typical single-rotor helicopter in forward flight

Description: From Summary: "As part of the general helicopter research program being undertaken by the National Advisory Committee for Aeronautics to provide designers with fundamental rotor information, the forward-flight performance characteristics of a typical single-rotor helicopter, which is equipped with main and tail rotors, have been investigated in the Langley full-scale tunnel. The test conditions included operation of tip-speed ratios from 0.10 to 0.27 and at thrust coefficients from 0.0030 to 0.0060. Results obtained with production rotor were compared with those for an alternate set of blades having closer rib spacing and a smoother and more accurately contoured surface in order to evaluate the performance gains that are available by the use of rotor blades having an improved surface condition."
Date: 1948
Creator: Dingeldein, Richard C. & Schaefer, Raymond F.
Partner: UNT Libraries Government Documents Department

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

Some Static Longitudinal Stability Characteristics of an Overlapped-Type Tandem-Rotor Helicopter at Low Airspeeds

Description: Note presenting flight measurements of some longitudinal static stability characteristics with an overlapped-type tandem-rotor helicopter at low airspeeds. the data show that a critical amount of longitudinal control is required to maintain trimmed flight at certain combinations of airspeed and rate of descent.
Date: September 1958
Creator: Tapscott, Robert J.
Partner: UNT Libraries Government Documents Department

Investigation of vertical drag and periodic airloads acting on flat panels in a rotor slipstream

Description: Tests have been conducted on the Langley helicopter test tower to determine the vertical drag and pressure distributions on flat panels mounted below a helicopter rotor. Calculations of the vertical drag by use of a strip-analysis procedure outlined in the paper and the assumption of a fully contracted wake agreed well with the experimental results over the range from 0.2 to 0.64 rotor radius beneath the plane of zero flapping. The pressure increase caused by the passage of the blade over the panel is a maximum at about the 0.8 radius spanwise station. At this station, the pressure decreases from 10 times the disk loading per blade at 0.05 radius beneath the rotor plane of zero flapping to one-half of the disk loading per blade at 0.64 radius beneath the plane of zero flapping.
Date: December 1956
Creator: Makofski, Robert A. & Menkick, George F.
Partner: UNT Libraries Government Documents Department

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

Analysis of ground effect on the lifting airscrew

Description: From Summary: "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."
Date: December 1941
Creator: Knight, Montgomery & Hegner, Ralph A
Partner: UNT Libraries Government Documents Department

The effect of control stiffness and forward speed on the flutter of a 1/10-scale dynamic model of a two-blade jet-driven helicopter rotor

Description: Report presenting testing of several configurations of rotor blades in order to evaluate the effect of variations in the blade-pitch-control stiffness and forward speed on the flutter speed.
Date: April 1955
Creator: Brooks, George W. & Sylvester, Maurice A.
Partner: UNT Libraries Government Documents Department

Stalling of helicopter blades

Description: Theoretical studies have predicted that operation of helicopter rotor beyond certain combinations of thrust, forward speed, and rotational speed might be prevented by rapidly increasing stalling of the retreating blade. The same studies also indicate that the efficiency of the rotor will increase until these limits are reached or closely approached, so that it is desirable to design helicopter rotors for operation close to the limits imposed by blade stalling. Inasmuch as the theoretical predictions of blade stalling involve numerous approximations and assumptions, an experimental investigation was needed to determine whether, in actual practice, the stall did occur and spread as predicted and to establish the amount of stalling that could be present without severe vibration or control difficulties being introduced. This report presents the results of such an investigation.
Date: 1946
Creator: Gustafson, F. B. & Myers, G. C., Jr.
Partner: UNT Libraries Government Documents Department

Wind-Tunnel Tests of a Portion of a PV-2 Helicopter Rotor Blade

Description: From Summary: "A portion of a PV-2 helicopter rotor blade has been tested in the 6- by 6-foot test section of the Langley stability tunnel to determine if the aerodynamic characteristics were seriously affected by cross flow or fabric distortion. The outer portion of the blade was tested as a reflection plane model pivoted about the tunnel wall to obtain various angles of cross flow over the blade. Because the tunnel wall acts as a plane of symmetry, the measured aerodynamic characteristics correspond to those of an airfoil having various angles of sweepforward and sweepback. Tests were made with the vents on the lower surface open and also with the vents sealed and the internal pressure held at -20 inches of water producing an internal pressure coefficient of -1.059."
Date: March 29, 1945
Creator: Kemp, William B., Jr.
Partner: UNT Libraries Government Documents Department

Flight measurements of the vibrations encountered by a tandem helicopter and a method for measuring the coupled response in flight

Description: Report presenting a discussion of flight-test and analysis methods for some selected helicopter vibration studies. The analytical methods described are based on the determination of the power spectral density of the force and of the response due to the force through use of analog frequency-analysis technique. Results regarding the coupled response with wood blades, coupled response with metal blades, comparison between flight and ground tests, comparison of flight results with theory, suggestions for refined flight-test technique, and natural-vibration measurements are provided.
Date: December 1956
Creator: Yeates, John E., Jr.
Partner: UNT Libraries Government Documents Department

Wind-tunnel studies of the performance of multirotor configurations

Description: Report presenting the power requirements measured in static thrust and in level forward flight for two helicopter rotor configurations. One is a coaxial rotor arrangement with the rotors spaced approximately 19 percent of the rotor radius; the other is a tandem configuration in which the rotor-shaft spacing is 3 percent greater than the rotor diameter and in which the rotors lie in the same plane.
Date: August 1954
Creator: Dingeldein, Richard C.
Partner: UNT Libraries Government Documents Department

One-Dimensional, Compressible, Viscous Flow Relations Applicable to Flow in a Ducted Helicopter Blade

Description: Report presenting one-dimensional, steady-state, compressible, viscous flow relations which permit the determination of flow conditions at any radial position in a ducted helicopter blade. The relations are required for estimating the performance of proposed helicopter jet-propulsion systems which involve ducting air or gases through the blade from root to tip.
Date: December 1953
Creator: Henry, John R.
Partner: UNT Libraries Government Documents Department

An experimental investigation of the effect of various parameters including tip Mach number on the flutter of some model helicopter rotor blades

Description: Report presenting studies of some of the effects of parameters such as Mach number, blade angle, and structural damping on the flutter of model helicopter rotor blades in the hovering condition. Forward movement of the blade chordwise center-of-gravity location tended to raise the flutter speeds at low pitch angles, but had no effect at high pitch angles. The significant flutter data for the tests along with detailed descriptions of the models are included to facilitate more detailed analyses.
Date: September 1958
Creator: Brooks, George W. & Baker, John E.
Partner: UNT Libraries Government Documents Department

Flight and analytical methods for determining the coupled vibration response of tandem helicopters

Description: Chapter one presents a discussion of flight-test and analysis methods for some selected helicopter vibration studies. The use of a mechanical shaker in flight to determine the structural response is reported. A method for the analytical determination of the natural coupled frequencies and mode shapes of vibrations in the vertical plane of tandem helicopters is presented in Chapter two. The coupled mode shapes and frequencies are then used to calculate the response of the helicopter to applied oscillating forces.
Date: 1957
Creator: Yeates, John E., Jr.; Brooks, George W. & Houbolt, John C.
Partner: UNT Libraries Government Documents Department