509 Matching Results
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An introduction to the physical aspects of helicopter stability
"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 pitching or rolling velocity - are explained in detail" (p. 1).
Date:
November 1949
Creator:
Gessow, Alfred & Amer, Kenneth B.
System:
The UNT Digital Library
Determination of plate compressive strengths at elevated temperatures
From Summary: "The results of local-instability tests of H-section plate assemblies and compressive stress-strain tests of extruded 75S-T6 aluminum alloy, obtained to determine flat-plate compressive strengths under stabilized elevated-temperature conditions, are given for temperatures up to 600 degrees Fahrenheit. The results show that methods available for calculating the critical compressive stress at room temperature can also be used at elevated temperatures if the applicable compressive stress-strain curve for the material is given."
Date:
February 1949
Creator:
Heimerl, George J. & Roberts, William M.
System:
The UNT Digital Library
Theoretical analysis of oscillations of a towed cable
Report presenting a theoretical study of the oscillations of a towed cable, which indicated that oscillations traveling downwind along the cable are amplified by aerodynamic forces when the airspeed is greater than the speed of propagation of waves along the cable. The theory provides a possible explanation for the violent motions of towed airspeed heads which appear above a certain speed.
Date:
1949
Creator:
Phillips, William H.
System:
The UNT Digital Library
The effects of aerodynamic brakes upon the speed characteristics of airplanes
Report presenting a study of the factors influencing the performance of aerodynamic brakes. The increases in drag coefficient that are characteristics of several types of wing and fuselage aerodynamic brakes, which have been tested in wind tunnels or in flight, are summarized in the report.
Date:
September 1949
Creator:
Stephenson, Jack D.
System:
The UNT Digital Library
Aerodynamic characteristics of 15 NACA airfoil sections at seven Reynolds numbers from 0.7 x 10(exp 6) to 9.0 x 10(exp 6)
Report presenting an investigation of the two-dimensional aerodynamic characteristics of 15 NACA airfoils at four Reynolds numbers. The results indicate that the drag coefficient at the design lift coefficient and the maximum lift coefficient are the most important aerodynamic characteristics and are most affected by Reynolds number changes.
Date:
October 1949
Creator:
Loftin, Laurence K., Jr. & Smith, Hamilton A.
System:
The UNT Digital Library
Two matrix methods for calculating forcing functions from known responses
Report presenting an analysis of two matrix methods for calculating responses of linear systems for given forcing functions and indicial responses in order to find a method suitable for solving the inverse problem of calculating forcing functions from known responses. The results of both methods are compared with exact solutions for both the direct and the inverse problems.
Date:
October 1949
Creator:
Mazelsky, Bernard & Diederich, Franklin W.
System:
The UNT Digital Library
Experimental Investigation of Flutter of a Propeller With Clark Y Section Operating at Zero Forward Velocity at Positive and Negative Blade-Angle Settings
Report presenting an investigation of the flutter of a small one-blade wooden propeller with a Clark Y section. The highest flutter speeds were found in the vicinity of the angle of zero aerodynamic moment, with flutter speed increasing in this region with decreasing pressure.
Date:
December 1949
Creator:
Baker, John E. & Paulnock, Russell S.
System:
The UNT Digital Library
A Comparison of Wing Loads Measured in Flight on a Fighter-Type Airplane by Strain-Gage and Pressure Distribution Methods
Note presenting pressure distribution measurements made on the wing of a fighter-type airplane to determine the span loading and to compare center-of-pressure results with those obtained by strain-gage measurements on the same airplane during a previous flight investigation. Flight tests were all made at a pressure altitude of about 30,000 feet and covered a Mach number range from approximately 0.35 to 0.81. Results regarding additional air load, spanwise center of pressure of additional air load, basic air load distribution, and span loading during a stall and buffeting are provided.
Date:
November 1949
Creator:
Aiken, William S., Jr. & Howard, Donald A.
System:
The UNT Digital Library
Investigation of flow coefficient of circular, square, and elliptical orifices at high pressure ratios
Report presenting an experimental investigation to determine the orifice coefficient of a jet direct perpendicularly to an air stream as a function of pressure ratio and jet Reynolds number for circular, square, and elliptical orifices. The effect of air-stream velocity on the jet flow was also determined for three tunnel-air velocities.
Date:
September 1949
Creator:
Callaghan, Edmund E. & Bowden, Dean T.
System:
The UNT Digital Library
Annular-jet ejectors
From Summary: "Included in the report are the results of total-pressure surveys made at downstream ends of the mixing tubes."
Date:
November 1949
Creator:
Reid, Elliott G.
System:
The UNT Digital Library
Method of determining conditions of maximum efficiency of an independent turbine-propeller combination
Report presenting an investigation of a turbine and propeller to determine the conditions of maximum-efficiency operation when utilized as an independent turbine-propeller combination. The procedure used to determine the conditions of maximum efficiency and speed ratio between the turbine and propeller is described.
Date:
September 1949
Creator:
Heidmann, Marcus F.
System:
The UNT Digital Library
Plastic buckling of extruded composite sections in compression
From Summary: "The theory of plastic buckling, originally derived for individual plates, has been extended to apply to combinations of plates such as H- and Z-sections. The theory has been applied specifically to extruded H-sections of 75S-T6 aluminum alloy; the calculated buckling stresses agree satisfactorily with the stresses obtained experimentally."
Date:
October 1949
Creator:
Stowell, Elbridge Z. & Pride, Richard A.
System:
The UNT Digital Library
Investigations relating to the extension of laminar flow by means of boundary-layer suction through slots
Report presenting an experimental investigation of boundary-layer suction through slots as a means of increasing the extent of laminar flow on airfoil sections. Results regarding slot geometry and arrangement, suction slots in an unfavorable pressure gradients, suction slots in a favorable pressure gradient, and a determination of the relations controlling the distribution of suction slots are provided.
Date:
October 1949
Creator:
Loftin, Laurence K., Jr. & Burrows, Dale L.
System:
The UNT Digital Library
Critical Shear Stress of a Curved Rectangular Panel With a Central Stiffener
"A theoretical solution is given for the critical shear stress of a simply supported curved rectangular plate stiffened by a central stiffener offering no torsional restraint which lies in either the axial or circumferential direction. Results are obtained by means of the Galerkin method and are presented in the form of computed curves and tables" (p. 1).
Date:
October 1949
Creator:
Stein, Manuel & Yaeger, David J.
System:
The UNT Digital Library
Theoretical spanwise lift distributions of low-aspect-ratio wings at speeds below and above the speed of sound
From Summary: "The spanwise lift distributions of wings of low aspect ratio but of arbitrary plan form and angle-of-attack distribution have been analyzed by two well-established concepts: the virtual-mass concept and the Weissinger method. Both concepts have been found to yield the same simple integral expression for the spanwise lift distribution in terms of the spanwise angle-of-attack distribution. Tables and figures of lit distributions of low-aspect-ratio wings have been presented."
Date:
October 1949
Creator:
Diederich, Franklin W. & Zlotnick, Martin
System:
The UNT Digital Library
Summary of the theoretical lift, damping-in-roll, and center-of-pressure characteristics of various wing plan forms at supersonic speeds
Report presenting information for the determination of the theoretical lift, damping-in-roll, and center-of-pressure characteristics for a group of plan forms at supersonic speeds. The information is presented in three forms: equations, figures presenting generalized curves, and figures presenting curves for representative groups of configurations. Several observations are made in regards to the effect of taper ratio, angle of sweep, and aspect ratio on the values of the derivatives.
Date:
October 1949
Creator:
Piland, Robert O.
System:
The UNT Digital Library
Data on the Compressive Strength of 75S-T6 Aluminum-Alloy Flat Panels Having Small, Thin, Widely Spaced, Longitudinal Extruded Z-Section Stiffeners
"The experimental results are presented for the second part of an investigation of the compressive strength of 75S-T6 aluminum-alloy flat panels with longitudinal extruded Z-section stiffeners. This part of the investigation is particularly concerned with panels in which the ratio of the thickness of the stiffener material to the skin material is small and the ratio of stiffener spacing to skin thickness is large" (p. 1).
Date:
November 1949
Creator:
Hickman, William A. & Dow, Norris F.
System:
The UNT Digital Library
Effect of Forebody Warp and Increase in Afterbody Length on the Hydrodynamic Qualities of a Flying-Boat Hull of High Length-Beam Ratio
Note presenting an investigation with the aim of achieving improved hydrodynamic qualities for flying boats, which involved determining the combined effect of a warped forebody and extended afterbody on the hydrodynamic characteristics of a full having a basic length-beam ratio of 15. Results regarding longitudinal stability, landing stability, spray characteristics, and landings in waves are provided.
Date:
November 1949
Creator:
Kapryan, Walter J.
System:
The UNT Digital Library
An Analytical Study of the Steady Vertical Descent in Autorotation of Single-Rotor Helicopters
"This report is the result of the first part of a broad program to analyze the transient motions of a helicopter, which occur in the various phases of flight following power failure" (p. 1).
Date:
June 1949
Creator:
Nikolsky, A. A. & Seckel, Edward
System:
The UNT Digital Library
An Analysis of the Transition of a Helicopter From Hovering to Steady Autorotative Vertical Descent
"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
System:
The UNT Digital Library
Shear Buckling of Infinitely Long Simply Supported Metalite Type Sandwich Plates
"A theoretical solution is obtained for the problem of the shear buckling of infinitely long simply supported elastic Metalite type sandwich plates. An approximate correction is suggested for the determination of the critical shear stresses of plates that buckle in the plastic range" (p. 1).
Date:
July 1949
Creator:
Seide, Paul
System:
The UNT Digital Library
Physical Properties at Elevated Temperature of Seven Hot-Pressed Ceramics
Report presenting an investigation of seven hot-pressed ceramics for possible gas-turbine application. The properties, short-time tensile strength, thermal-shock resistance, coefficient of liner expansion, and density were determined. The ceramics tested were magnesium oxide, titanium carbide, zirconium carbide, boron carbide, silicon carbide with boron carbide, zircon, and zirconia with lime.
Date:
July 1949
Creator:
Gangler, James J.; Robards, Chester F. & McNutt, James E.
System:
The UNT Digital Library
Approximate Method for Predicting Form and Location of Detached Shock Waves Ahead of Plane or Axially Symmetric Bodies
Note presenting an approximate method developed to predict the location of detached shock waves ahead of two-dimensional and axially symmetric bodies. The method is based on the continuity relation, which is applied to the air that passes the sonic line.
Date:
July 1949
Creator:
Moeckel, W. E.
System:
The UNT Digital Library
Two-dimensional investigation of five related NACA airfoil sections designed for rotating-wing aircraft
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.
System:
The UNT Digital Library