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 Decade: 1940-1949
 Year: 1949
 Collection: National Advisory Committee for Aeronautics Collection
General Theory of Aerodynamic Instability and the Mechanism of Flutter

General Theory of Aerodynamic Instability and the Mechanism of Flutter

Date: January 1, 1949
Creator: Theodorsen, Theodore
Description: The aerodynamic forces on an oscillating airfoil or airfoil-aileron combination of three independent degrees of freedom have been determined. The problem resolves itself into the solution of certain definite integrals, which have been identified as Bessel functions of the first and second kind and of zero and first order. The theory, being based on potential flow and the Kutta condition, is fundamentally equivalent to the conventional wing-section theory relating to the steady case. The air forces being known, the mechanism of aerodynamic instability has been analyzed in detail. An exact solution, involving potential flow and the adoption of the Kutta condition, has been analyzed in detail. An exact solution, involving potential flow and the adoption of the Kutta condition, has been arrived at. The solution is of a simple form and is expressed by means of an auxiliary parameter K.
Contributing Partner: UNT Libraries Government Documents Department
Langley free-flight-tunnel investigation of the automatic lateral stability characteristics of a model equipped with a gyro stabilizing unit that provided either flicker-type or hunting control

Langley free-flight-tunnel investigation of the automatic lateral stability characteristics of a model equipped with a gyro stabilizing unit that provided either flicker-type or hunting control

Date: January 11, 1949
Creator: Schade, Robert O
Description: None
Contributing Partner: UNT Libraries Government Documents Department
The effect of air jets simulating chines or multiple steps on the hydrodynamic characteristics of a streamline fuselage

The effect of air jets simulating chines or multiple steps on the hydrodynamic characteristics of a streamline fuselage

Date: January 7, 1949
Creator: Weinflash, Bernard
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Stability and control data obtained from first flight of X-4 airplane

Stability and control data obtained from first flight of X-4 airplane

Date: February 7, 1949
Creator: Drake, Hubert M
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Study of the canard configuration with particular reference to transonic flight characteristics and low-speed characteristics at high lift

Study of the canard configuration with particular reference to transonic flight characteristics and low-speed characteristics at high lift

Date: November 16, 1949
Creator: Mathews, Charles W
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Initial experiments on flutter of unswept cantilever wings at Mach number 1.3

Initial experiments on flutter of unswept cantilever wings at Mach number 1.3

Date: January 6, 1949
Creator: Tuovila, W J; Baker, John E & Regier, Arthur A
Description: None
Contributing Partner: UNT Libraries Government Documents Department
High-speed wind-tunnel investigation of a sweptback wing with an added triangular area at the center

High-speed wind-tunnel investigation of a sweptback wing with an added triangular area at the center

Date: January 14, 1949
Creator: Henry, Beverly, Z , jr
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Present status of research on boundary-layer control.

Present status of research on boundary-layer control.

Date: January 12, 1949
Creator: Von Doenhoff, Albert E & Loftin, Laurence K , Jr
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Stability results obtained with Douglas D-558-1 airplane (BuAero No. 37971) in flight up to a Mach number of 0.89

Stability results obtained with Douglas D-558-1 airplane (BuAero No. 37971) in flight up to a Mach number of 0.89

Date: April 22, 1949
Creator: Lilly, Howard C & Barlow, William H
Description: None
Contributing Partner: UNT Libraries Government Documents Department
The effect of rate of change of angle of attack on the maximum lift coefficient of a pursuit airplane

The effect of rate of change of angle of attack on the maximum lift coefficient of a pursuit airplane

Date: January 20, 1949
Creator: Gadeberg, Burnett L
Description: None
Contributing Partner: UNT Libraries Government Documents Department
The effect of the propeller slipstream on the characteristics of submerged inlets

The effect of the propeller slipstream on the characteristics of submerged inlets

Date: September 9, 1949
Creator: Delany, Noel K
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Performance of 24-inch supersonic axial-flow compressor in air II : performance of compressor rotor at equivalent tip speeds from 800 to 1765 feet per second

Performance of 24-inch supersonic axial-flow compressor in air II : performance of compressor rotor at equivalent tip speeds from 800 to 1765 feet per second

Date: January 21, 1949
Creator: Johnsen, Irving A; Wright, Linwood C & Hartmann, Melvin J
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Effect of screens in wide-angle diffusers

Effect of screens in wide-angle diffusers

Date: January 1, 1949
Creator: Schubauer, G B & Spangenberg, W G
Description: An experimental investigation at low airspeeds was made of the filling effect observed when a screen or similar resistance is placed across a diffuser. The filling effect is found to be real in that screens can prevent separation or restore separated flow in diffusers even of extreme divergence and to depend principally on screen location and pressure-drop coefficient of the screen. Results are given for three different diffusers of circular cross section with a variety of screen arrangements. Effects of single screens and multiple screens are shown. The mechanics of the filling effect is explained, and possible efficiencies are discussed. Results of arrangements of multiple screens in wide-angle diffusers are given to show a possible application to damping screens as used in wind tunnels to reduce turbulence. (author).
Contributing Partner: UNT Libraries Government Documents Department
Investigations on the stability, oscillation, and stress conditions of airplanes with tab control.  Second partial report : application of the solutions  obtained in the first partial report to tab-controlled airplanes.

Investigations on the stability, oscillation, and stress conditions of airplanes with tab control. Second partial report : application of the solutions obtained in the first partial report to tab-controlled airplanes.

Date: September 1, 1949
Creator: Filzek, B
Description: The first partial report, FB 2000, contained a discussion of the derivation of the equations of motion and their solutions for a tab-controlled airplane; the results obtained there are now to be applied to the longitudinal motion of tab-controlled airplanes. In view of the abundance of structural factors and aerodynamic parameters, a general discussion of the problems is unfeasible. Thus it is demonstrated on the basis of examples what stability, oscillation, and stress conditions are to be expected for tab-controlled airplanes. (author).
Contributing Partner: UNT Libraries Government Documents Department
Aerodynamic characteristics at subsonic and transonic speeds of a 42.7 degree sweptback wing model having an aileron with finite trailing-edge thickness

Aerodynamic characteristics at subsonic and transonic speeds of a 42.7 degree sweptback wing model having an aileron with finite trailing-edge thickness

Date: January 12, 1949
Creator: Lockwood, Vernard E; Vogler, Raymond D & Turner, Thomas R
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Airfoil measurements in the DVL high-speed wind tunnel (2.7-meter diameter)

Airfoil measurements in the DVL high-speed wind tunnel (2.7-meter diameter)

Date: June 1, 1949
Creator: Gothert, B
Description: Report is a brief summary of investigations on symmetrical and cambered airfoils in the DVL high-speed tunnel. Some information on the effects of low aspect ratio are also included.
Contributing Partner: UNT Libraries Government Documents Department
Aerodynamic study of a wing-fuselage combination employing a wing swept back 63 degrees : characteristics at a Mach number of 1.53 including effect of small variations of sweep

Aerodynamic study of a wing-fuselage combination employing a wing swept back 63 degrees : characteristics at a Mach number of 1.53 including effect of small variations of sweep

Date: January 26, 1949
Creator: Madden, Robert T
Description: Measured values of lift, drag, and pitching moment at a Mach number of 1.53 and Reynolds numbers of 0.31, 0.62, and 0.84 million are presented for a wing-fuselage combination having a wing leading-edge sweep angle of 63 degrees, an aspect ratio of 3.42, a taper ratio of 0.25, and an NACA 64A006 section in the stream direction. Data are also presented for sweep angles of 57.0 degrees, 60.4 degrees, 67.0 degrees, and 69.9 degrees. The experimentally determined characteristics were less favorable than indicated by the linear theory but the experimental and theoretical trends with sweep were in good agreement. Boundary-layer-flow tests showed that laminar boundary-layer separation was the primary cause of the differences between experiment and theory.
Contributing Partner: UNT Libraries Government Documents Department
Aerodynamic study of a wing-fuselage combination employing a wing swept back 63 degrees : investigation of a large-scale model at low speed

Aerodynamic study of a wing-fuselage combination employing a wing swept back 63 degrees : investigation of a large-scale model at low speed

Date: January 21, 1949
Creator: Mccormack, Gerald M & Walling, Walter C
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Vibration survey of blades in 10-stage axial-flow compressor I : static investigation

Vibration survey of blades in 10-stage axial-flow compressor I : static investigation

Date: January 31, 1949
Creator: Meyer, Andre J , Jr & Calvert, Howard F
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Recommendations for numerical solution of reinforced-panel and fuselage-ring problems

Recommendations for numerical solution of reinforced-panel and fuselage-ring problems

Date: January 1, 1949
Creator: Hoff, N J & Libby, Paul A
Description: Procedures are recommended for solving the equations of equilibrium of reinforced panels and isolated fuselage rings as represented by the external loads and the operations table established according to Southwell's method. From the solution of these equations the stress distribution can be easily determined. The method of systematic relaxations, the matrix-calculus method, and several other methods applicable in special cases are discussed. Definite recommendations are made for obtaining the solution of reinforced-panel problems which are generally designated as shear lag problems. The procedures recommended are demonstrated in the analysis of a number of panels. In the case of fuselage rings it is not possible to make definite recommendations for the solution of the equilibrium equations for all rings and loadings. However, suggestions based on the latest experience are made and demonstrated on several rings.
Contributing Partner: UNT Libraries Government Documents Department
Plastic buckling of a rectangular plate under edge thrusts

Plastic buckling of a rectangular plate under edge thrusts

Date: January 1, 1949
Creator: Handelman, G H & Prager, W
Description: The fundamental equations for the plastic buckling of a rectangular plate under edge thrusts are developed on the basis of a new set of stress-strain relations for the behavior of a metal in the plastic range. These relations are derived for buckling from a state of uniform compression. The fundamental equation for the buckling of a simply compressed plate together with typical boundary conditions is then developed and the results are applied to calculating the buckling loads of a thin strip, a simply supported plate, and a cruciform section. Comparisons with the theories of Timoshenko and Ilyushin are made. Finally, an energy method is given which can be used for finding approximate values of the critical load.
Contributing Partner: UNT Libraries Government Documents Department
Susceptibility to Welding Cracking, Welding Sensitivity, Susceptibility to Welding Seam Cracking, and Test Methods for These Failures

Susceptibility to Welding Cracking, Welding Sensitivity, Susceptibility to Welding Seam Cracking, and Test Methods for These Failures

Date: June 1, 1949
Creator: Zeyen, K. L.
Description: In the years after the First World war a very rapid development, which even today has by no means come to an end, took place in the field of welding; here also, as in most technical innovations, failures made their appearance. Thereupon comprehensive Investigations were undertaken by steel manufacturers and consumers with cooperation of the authorities. b most cases the reasons for failure could be determined and eliminated and further occurrences avoided by the use of new test methods.
Contributing Partner: UNT Libraries Government Documents Department
On the Motions of an Oscillating System Under the Influence of Flip-Flop Controls

On the Motions of an Oscillating System Under the Influence of Flip-Flop Controls

Date: November 1, 1949
Creator: Fluegge-Lotz, I. & Klotter, K.
Description: So-called flip-flop controls (also called "on-off-course controls") are frequently preferred to continuous controls because of their simple construction. Thus they are used also for the steering control of airplanes. Such a body possesses-even if one thinks, for instance, only of the symmetric longitudinal motion - three degrees of freedom so that a study of its motions under the influence of an intermittent control is at least lengthy. Thus, it is suggested that an investigation of the basic effect of such a control first be made on a system with one degree of freedom. Furthermore, we limit ourselves in the resent report to the investigation of an "ideal" control where the control surface immediately obeys the command given by the "steering control function". Thus the oscillation properties of the control surface and the defects in linkage, sensing element, and mixing device are, at first, neglected. As long as the deviations from the "ideal" control may be neglected in practice, also the motion of the control surface takes place at the heat of the motion of the principal system. The aim of our investigation is to obtain a survey of the influence of the system and control coefficients on the damping behavior ...
Contributing Partner: UNT Libraries Government Documents Department
Two-Dimensional Wing Theory in the Supersonic Range

Two-Dimensional Wing Theory in the Supersonic Range

Date: June 1, 1949
Creator: Hoenl, H.
Description: The plane problem of the vibrating airfoil in supersonic flow is dealt with and solved within the scope of a linearized theory by the method of the acceleration potential.
Contributing Partner: UNT Libraries Government Documents Department
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