You limited your search to:

  Partner: UNT Libraries Government Documents Department
 Serial/Series Title: NACA Technical Reports
 Collection: Technical Report Archive and Image Library
Charts for estimating tail-rotor contribution to helicopter directional stability and control in low-speed flight

Charts for estimating tail-rotor contribution to helicopter directional stability and control in low-speed flight

Date: January 1, 1955
Creator: Amer, Kenneth B & Gessow, Alfred
Description: Theoretically derived charts and equations are presented by which tail-rotor design studies of directional trim and control response at low forward speed can be conveniently made. The charts can also be used to obtain the main-rotor stability derivatives of thrust with respect to collective pitch and angle of attack at low forward speeds. The use of the charts and equations for tail-rotor design studies is illustrated. Comparisons between theoretical and experimental results are presented. The charts indicate, and flight tests confirm, that the region of vortex roughness which is familiar for the main rotor is also encountered by the tail rotor and that prolonged operation at the corresponding flight conditions would be difficult.
Contributing Partner: UNT Libraries Government Documents Department
Theoretical prediction of pressure distributions on nonlifting airfoils at high subsonic speeds

Theoretical prediction of pressure distributions on nonlifting airfoils at high subsonic speeds

Date: January 1, 1955
Creator: Spreiter, John R & Alksne, Alberta
Description: Theoretical pressure distributions on nonlifting circular-arc airfoils in two-dimensional flows with high subsonic free-stream velocity are found by determining approximate solutions, through an iteration process, of an integral equation for transonic flow proposed by Oswatitsch. The integral equation stems directly from the small-disturbance theory for transonic flow. This method of analysis possesses the advantage of remaining in the physical, rather than the hodograph, variable and can be applied in airfoils having curved surfaces. After discussion of the derivation of the integral equation and qualitative aspects of the solution, results of calculations carried out for circular-arc airfoils in flows with free-stream Mach numbers up to unity are described. These results indicate most of the principal phenomena observed in experimental studies.
Contributing Partner: UNT Libraries Government Documents Department
Analog study of interacting and noninteracting multiple-loop control systems for turbojet engines

Analog study of interacting and noninteracting multiple-loop control systems for turbojet engines

Date: January 1, 1955
Creator: Pack, George J & Phillips, W E , Jr
Description: The results of an analog investigation of several turbojet-engine control configurations is presented in this report. Both proportional and proportional-plus-integral controllers were studied, and compensating terms for engine interaction were added to the control system. Data were obtained on the stability limits and the transient responses of these various configurations. Analytical expressions in terms of the component transfer functions were developed for the configurations studied, and the optimum form for the compensation terms was determined. It was found that the addition of the integral term, while making the system slower and more oscillatory, was desirable in that it made the final values of the system parameters independent of source of disturbance and also eliminated droop in these parameters. Definite improvement in system characteristics resulted from the use of proper compensation terms. At comparable gain points the compensated system was faster and more stable. Complete compensation eliminated engine interaction, permitting each loop to be developed to an optimum point independently.
Contributing Partner: UNT Libraries Government Documents Department
Contributions on the mechanics of boundary-layer transition

Contributions on the mechanics of boundary-layer transition

Date: January 1, 1956
Creator: Schubauer, G B & Klebanoff, P S
Description: The manner in which flow in a boundary layer becomes turbulent was investigated on a flat plate at wind speeds generally below 100 feet per second. Hot-wire techniques were used, and many of the results are derived from oscillograms of velocity fluctuations in the transition region. Following a presentation of the more familiar aspects of transition, there are presented the very revealing facts discovered while studying the characteristics of artificially produced turbulent spots. These are: (1) oscillograms of natural transition are identical to oscillograms of spot passage; (2) transition starts from perturbations in the laminar flow as spots which then grow in accordance with the general concept proposed by Emmons. (3) Turbulence always moves downstream followed by laminar flow; (4) the following flow is in a state of calm for a period during which transition will not occur.
Contributing Partner: UNT Libraries Government Documents Department
Cooperative investigation of relationship between static and fatigue properties of wrought n-155 alloy at elevated temperatures

Cooperative investigation of relationship between static and fatigue properties of wrought n-155 alloy at elevated temperatures

Date: January 1, 1956
Creator: unknown
Description: Report presents the correlation of extensive data obtained relating properties of wrought n-155 alloy under static, combined static and dynamic, and complete reversed dynamic stress conditions. Time period for fracture ranged from 50 to 500 hours at room temperature, 1,000 degrees, 1,200 degrees, and 1,500 degrees F.
Contributing Partner: UNT Libraries Government Documents Department
Theoretical calculations of the pressure, forces, and moments at supersonic speeds due to various lateral motions acting on thin isolated vertical tails

Theoretical calculations of the pressure, forces, and moments at supersonic speeds due to various lateral motions acting on thin isolated vertical tails

Date: January 1, 1956
Creator: Margolis, Kenneth & Bobbitt, Percy J
Description: Velocity potentials, pressure, distributions, and stability derivatives are derived by use of supersonic linearized theory for families of thin isolated vertical tails performing steady rolling, steady yawing, and constant-lateral-acceleration motions. Vertical-tail families (half-delta and rectangular plan forms) are considered for a broad Mach number range. Also considered are the vertical tail with arbitrary sweepback and taper ratio at Mach numbers for which both the leading edge and trailing edge of the tail are supersonic and the triangular vertical tail with a subsonic leading edge and a supersonic trailing edge. Expressions for potentials, pressures, and stability derivatives are tabulated.
Contributing Partner: UNT Libraries Government Documents Department
The proper combination of lift loadings for least drag on a supersonic wing

The proper combination of lift loadings for least drag on a supersonic wing

Date: January 1, 1956
Creator: Grant, Frederick C
Description: Lagrange's method of undetermined multipliers is applied to the problem of properly combining lift loadings for the least drag at a given lift on supersonic wings. The method shows the interference drag between the optimum loading and any loading at the same lift coefficient to be constant. This is an integral form of the criterion established by Robert T. Jones for optimum loadings. The best combination of four loadings on a delta wing with subsonic leading edges is calculated as a numerical example. The loadings considered have finite pressures everywhere on the plan form. Through the sweepback range the optimum combination of the four nonsingular loadings has about the same drag coefficient as a flat plate with leading-edge thrust.
Contributing Partner: UNT Libraries Government Documents Department
A study of the zero-lift drag-rise characteristics of wing-body combinations near the speed of sound

A study of the zero-lift drag-rise characteristics of wing-body combinations near the speed of sound

Date: January 1, 1956
Creator: Whitcomb, Richard T
Description: Comparisons have been made of the shock phenomena and drag-rise increments for representative wing and central-body combinations with those for bodies of revolution having the same axial developments of cross-sectional areas normal to the airstream. On the basis of these comparisons, it is concluded that near the speed of sound the zero-lift drag rise of a low-aspect-ratio thin-wing and body combination is primarily dependent on the axial development of the cross-sectional areas normal to the airstream. It follows that the drag rise for any such configuration is approximately the same as that for any other with the same development of cross-sectional areas. Investigations have also been made of representative wing-body combinations with the body so indented that the axial developments of cross-sectional areas for the combinations were the same as that for the original body alone. Such indentations greatly reduced or eliminated the zero-lift drag-rise increments associated with the wings near the speed of sound.
Contributing Partner: UNT Libraries Government Documents Department
Wind-tunnel and flight investigations of the use of leading-edge area suction for the purpose of increasing the maximum lift coefficient of a 35 degree swept-wing airplane

Wind-tunnel and flight investigations of the use of leading-edge area suction for the purpose of increasing the maximum lift coefficient of a 35 degree swept-wing airplane

Date: January 1, 1956
Creator: Holzhauser, Curt A & Bray, Richard S
Description: An investigation was undertaken to determine the increase in maximum lift coefficient that could be obtained by applying area suction near the leading edge of a wing. This investigation was performed first with a 35 degree swept-wing model in the wind tunnel, and then with an operational 35 degree swept-wing airplane which was modified in accord with the wind-tunnel results. The wind-tunnel and flight tests indicated that the maximum lift coefficient was increased more than 50 percent by the use of area suction. Good agreement was obtained in the comparison of the wind-tunnel results with those measured in flight.
Contributing Partner: UNT Libraries Government Documents Department
Second-order subsonic airfoil theory including edge effects

Second-order subsonic airfoil theory including edge effects

Date: January 1, 1956
Creator: Van Dyke, Milton D
Description: Several recent advances in plane subsonic flow theory are combined into a unified second-order theory for airfoil sections of arbitrary shape. The solution is reached in three steps: the incompressible result is found by integration, it is converted into the corresponding subsonic compressible result by means of the second-order compressibility rule, and it is rendered uniformly valid near stagnation points by further rules. Solutions for a number of airfoils are given and are compared with the results of other theories and of experiment. A straight-forward computing scheme is outlined for calculating the surface velocities and pressures on any airfoil at any angle of attack.
Contributing Partner: UNT Libraries Government Documents Department