Report presenting an application of the linearized supersonic flow theory to the calculation of the camber and twist required for various lift distributions on a triangular wing with leading edges behind the Mach cone. Several specific examples are used and plots of the cambered surfaces, corresponding lift distributions, and values of the theoretical drag coefficients are presented.

Report presenting an investigation to ascertain the validity of various theories for the plastic buckling of compressed simply supported plates by means of local-instability tests of drawn square tubes of 14S-T6 aluminum alloy. The results obtained were in excellent agreement with Stowell's unified theory for the plastic buckling of columns and plates.

Note presenting an investigation to determine the effect of automatic stabilization on the lateral oscillatory stability of a hypothetical supersonic airplane. The investigation included an autopilot sensitive to either the yawing or rolling angular velocity. The results of the investigation indicated that all the automatic pilots improved the stability of the original unstable short-period oscillation.

Note presenting a survey that has been made of the various systems of equations which have been given in the literature for the analysis of small deflections of thin elastic shell. A new system of equations has been derived for the analysis of shells, which includes the effects of transverse shear and normal stresses.

Report presenting a method for the calculation of flutter speed of a uniform wing carrying an arbitrarily placed concentrated mass. The method involves the solution of the differential equations of motion of the wing at flutter speed and does not require the assumption of specific normal modes of vibration.

Report presenting combined force and wake survey tests on three-blade model propellers in order to determine the effects of blade-width distribution on constant-speed efficiency characteristics. The most important result is the demonstration that blade-width distribution has a marked influence on the constant-speed efficiency characteristics of propellers.

Report presenting a wind-tunnel investigation conducted in rolling flow to determine the effects of aspect ratio and sweep on the rolling stability derivatives for a series of untapered wings. The results indicated that when the aspect ratio is held constant, an increase in sweepback angle causes a significant reduction in the damping in roll at low lift coefficients for only the higher aspect ratios tested.

From Summary: "A theoretical solution is given for the critical shear stress of an infinitely long, simply supported, flat plate with identical, equally spaced, transverse stiffeners of zero torsional stiffness. Results are obtained by means of the Lagrangian multiplier method and are presented in the form of design charts. Experimental results are included and are found to be in good agreement with the theoretical results."

Note presenting an attempt to design the reinforcement of a cutout in a plane sheet in such a way that it is as nearly as possible equivalent to the part of the structure which has been cut out. A perfect equivalence would mean that the stresses and displacements of the structure remain the same as those which would have appeared without the cutout.

Report presenting an investigation to determine the effects of increased afterbody length on the hydrodynamic qualities of a model of a flying boat with a hull with a length-beam ratio of 15. Results regarding longitudinal stability, spray characteristics, excess thrust for take-off, landings in waves, and a summary chart are provided.

Note presenting a method for calculating the response and lag in pressure measuring systems subjected to steady-state sinusoidally varying pressures. The pressure system is assumed to consist of an inlet restriction, tubing length, and connected instrument volume. Results of the phase-shift determination are provided.

Report presenting a method for the strength analysis of stiffened beam webs as applied to beams with ratios of applied shear to buckling shear less than 2.5. Results regarding critical shear stress, forced crippling failure in uprights, and web failures are provided.

"Several methods (references 1 and 2) based on gas-dynamic principles are available for reducing such measurements. The results obtained by these methods are subject to the limitation of the gas-dynamic theory which is that the mean free path of the molecules between impacts, is small with respect to the measuring device. Inasmuch as no information on the subject is to present known to be available, the purpose of the present paper is to present a method based on the concept of free-molecule theory for use in connection with this problem" (p. 1).

Report presenting an experimental investigation of a series of exhaust mufflers installed on a typical six-cylinder light-airplane engine mounted on a ground dynamometer sound. Several conclusions regarding muffler design are drawn from this testing. Since engine and propeller noise are about equal for this power-plant installation, both engine-exhaust and propeller noises must be reduced to obtain a sizable reduction in overall sound-pressure level.

Report presenting an analysis of the measurements of drag-angle oscillation of a helicopter rotor made with the helicopter apparatus to determine both the natural frequencies and the damping required to prevent excessive drag-angle-oscillation response to various throttle and control movements. Results regarding symmetrical oscillations, unsymmetrical oscillations, blade damping, and general discussion are provided.

Note presenting an investigation to determine the fatigue-strength values for 24S-T aluminum alloy when subjected to various ratios of biaxial stresses. The stresses considered were both tensile. The results indicated that uniaxial fatigue-strength values in the longitudinal direction cannot be used to predict the fatigue strength, and that biaxial fatigue strength may be as low as 50 percent of the uniaxial fatigue strength.

"Results are presented of calculations for the elastic buckling load of a simply supported flat rectangular plate of uniform thickness subjected to unequal compressive stresses at two opposite edges, with a linear variation of stress between the two edges. The difference between the compressive stresses at the two loaded edges is equilibrated by shear stresses along the other two edges. The results show that a plate with a linear stress gradient will buckle at an average stress that is lower, but at a maximum stress that may be appreciably higher, than the uniform compressive buckling stress of the same plate" (p. 1).

Report presenting a wind-tunnel investigation to determine the boundary-layer and stalling characteristics of the NACA 63-009 airfoil section. Pressure distributions, tuft studies, and boundary-layer measurements were obtained. A localized region of flow separation was found to develop on the upper surface of the airfoil near the leading edge.

"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).

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."

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.

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.

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.

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.