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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

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

Exploratory investigation of a helicopter pressure-jet system on the Langley helicopter test tower

Description: Report presenting an investigation of a helicopter pressure-jet system. The effects of tip speed, fuel-air ratio, and pressure ratio on the propulsive characteristics of the pressure-jet system have been determined for a range of tip seeds, blade-root stagnation-pressure ratios, and fuel-air ratios. Results regarding tip-burner specific propulsive horsepower, propulsive horsepower per unit mean duct area, tip-burner specific fuel consumption, ratio of propulsive horsepower to equivalent air horsepower, effect of whirling on tip-unit thrust, effect of whirling on the tip-burner inlet pressure, effect of auxiliary fuel flow, power-off drag of tip units, and overall specific fuel consumption of pressure-jet system are provided.
Date: July 27, 1956
Creator: Makofski, Robert A. & Shivers, James P.
Partner: UNT Libraries Government Documents Department

Inherent stability of helicopters

Description: The equilibrium, in still air, of a "stationary" helicopter (i.e., of one having neither vertical nor translational velocity, but a tendency to remain practically motionless within restricted limits of space) presents some difficulty in practice and justifies a theoretical investigation of its "inherent stability," i.e., independent of the pilot.
Date: October 1923
Creator: Crocco, G. Arturo
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

The problem of the helicopter

Description: Report discussing some of the issues regarding the design and operation of helicopters and the theoretical basis behind them. Some particular issues covered include propeller blade design, helicopters in forced descent, horizontal travel, and stability and control.
Date: May 1920
Creator: Warner, E. P.
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

Flight tests of the Sikorsky HNS-1 (Army YR-4B) helicopter 2: hovering and vertical-flight performance with the original and an alternate set of main-rotor blades, including a comparison with hovering performance theory

Description: Report discussing testing of an HNS-1 (Army YR-4B) helicopter to determine the hovering data in the ground-effect region and at altitude with an original set of rotor blades and an alternate set with different aerodynamic design and surface condition.
Date: April 1945
Creator: Gustafson, F. B. & Gessow, Alfred
Partner: UNT Libraries Government Documents Department

Determination of the structural damping coefficients of six full-scale helicopter rotor blades of different materials and methods of construction

Description: Results of an experimental investigation of the structural damping of six full-scale helicopter rotor blades, made to determine the variation of structural damping with materials and methods of construction, are presented. The damping of the blades was determined for the first three flapwise bending modes, first chordwise bending mode, and first torsion mode. The contribution of structural damping to the total damping of the blades is discussed for several aerodynamic conditions in order to point out situations where structural damping is significant.
Date: December 1956
Creator: Gibson, Frederick W.
Partner: UNT Libraries Government Documents Department

Drag or negative traction of geared-down supporting propellers in the downward vertical glide of a helicopter

Description: Discussed here are computations of drag or negative traction of geared down supporting propellers in the downward vertical glide of a helicopter. By means of Frounde's Theory, the maximum value of the drag of a windmill is calculated. For wooden propellers, the author finds that the difference between the drag and the weight is proportional to the number of blades and is larger for propellers of small diameter; thus it is 25 kg. for a six blade propeller with a diameter of 2 m. 50. The author notes that if we are to adopt large propellers, we must have recourse to a different method of construction, resulting in large dimension propellers much lighter than those made of wood. In discussing insufficient drag, the author notes that the question of the drag of geared down supporting propellers can only be decided by experiment.
Date: September 1920
Creator: Toussaint, A.
Partner: UNT Libraries Government Documents Department

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

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

An estimate of the effect of engine supercharging on the take-off thrust of a typical helicopter at different altitudes and temperatures

Description: Report discussing the effects of supercharging on the take-off thrust and useful load for a typical helicopter. Performance of the engine with the supercharger and on the rotor thrust is detailed.
Date: March 1945
Creator: Bailey, F. J., Jr. & Voglewede, T. J.
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