Report presenting a consideration of the development of the laminar boundary layer in a compressible fluid. Formulas are given for determining the boundary-layer thickness and the boundary-layer Reynolds number, which is a measure of the boundary-layer stability, for airfoils and bodies of revolution.

Four models with longitudinal steps on the forebody were developed by modification of a model of a conventional hull and were tested in the National Advisory Committee for Aeronautics (NACA) tank. Models with longitudinal steps were found to have smaller resistance at high speed and greater resistance at low speed than the parent model that had the same afterbody but a conventional V-section forebody. The models with a single longitudinal step had better performance at hump speed and as low high-speed resistance except at very light loads. Spray strips at angles from 0 degrees to 45 degrees to the horizontal were fitted at the longitudinal steps and at the chine on one of the two step models having two longitudinal steps. The resistance and the height of the spray were less with each of the spray strips than without; the most favorable angle was found to lie between 15 degrees and 30 degrees.

"A method is presented for the computation and graphic representation of a series of possible turbine designs for any specific application. The use of a preliminary design chart is suggested for determining the number of stages and the effects of exit whirl and annular-area divergence on possible configurations. A specific design chart can then be made to aid in the study of the relations between turbine radius ratio, diameter, and significant design parameters such as Mach numbers, turning angles, and blade root stresses" (p. 1).

Note presenting a consideration of a wing-selection problem sometimes encountered in the preliminary design of supersonic airplanes and missiles. The problem is to determine the span, section thickness ratio, and skin thickness or hollowness ratio of the wing of least drag when the plan form, section shape, wing lift requirement, and flight conditions are assumed known. An example of the application of the method to a diamond wing at Mach number 2.0 for a range of specified flight conditions is presented.

The charts presented give the compressive buckling coefficients for a single-truss-core and a double-truss-core sandwich plate. These charts cover a wide range of sandwich proportions and may be used for sandwiches with unequal faces. They apply to inplane compressive loads acting parallel or perpendicular to the core direction or for various combinations of these loads. (author).

"Charts giving the compressive-buckling stress coefficients for sheet panels of a shape occurring in swept-wing plan forms are presented. The panels are assumed to be a part of a continuous flat sheet divided by nondeflecting supports into parallelogram-shaped areas. The stability analysis was performed by the energy method and the results show that, over a wide range of panel aspect ratio, such panels are decidedly more stable than equivalent rectangular panels of the same area" (p. 1).

Note presenting an investigation of the effects of tip dihedral on lateral stability and control characteristics by flight tests of models in the free-flight tunnel. The results indicate that at high lift coefficients, tip dihedral may cause a lightly damped lateral oscillation, which does not occur with full-span dihedral at similar values of effective dihedral and directional stability.

From Summary: "The problem of developing a windshield for aircraft which will withstand the effect of bird impacts during flight is a difficult one, as an estimate of the striking energy will indicate. If the average speed of the airplane is considered to be about 200 miles per hour and that of the bird about 70 miles per hour, the speed of the bird relative to the airplane may be as great as 400 feet per second. If a 4-pound bird is involved, a maximum impact energy of approximately 10,000 foot-pounds must be dissipated. To obtain this energy in a drop test in the Washington Monument, it would be necessary to drop a 20-pound weight down the 500-foot shaft. For both theoretical and practical reasons, it is necessary to keep the mass and speed more nearly like those to be encountered. However, to get an impact of about 10,000 foot-pounds with a 4-pound falling body, it would be necessary to drop it from a height of approximately one-half mile, neglecting air resistance. These facts will indicate some of the experimental obstacles in the way of simulating bird impacts against aircraft windshields."

Report presenting a note in two parts regarding simplified truss stability criteria. The first part covers the development of simplified criteria for the stability of planar pin-jointed trusses against buckling in the plane of the truss. The second part constitutes a report on tests carried out to verify the validity of the criteria developed in part one.

"An experimental determination of the critical bending moment of a box beam stiffened by posts is described and discussed. The experimental buckling load is in good agreement with that given by theory. Since appreciable distortion of the beam cross section occurred before the buckling load was reached, modification of post construction by the use of several ribs may be necessary for maintenance of the rectangular shape of the cross section" (p. 1).

Note presenting testing of twenty-seven structural joint specimens of 2024-T3 and 2024-T4 aluminum alloy consisting of a T-stringer riveted to a 10- by 10-inch skin surface under simulated aerodynamic heating with no external loading applied. Rivet size and pitch were found to influence the conductance but the rivet materials tested had no observable effect.

"The theoretical critical stress is derived for a simply supported curved rectangular panel in axial compression having a central chordwise stiffener offering no torsional restraint. The results are presented in the form of computed curves and a table. Because a panel of moderate or large curvature buckles in compression at a stress considerably below the theoretical value, a method is suggested to aid in determining the critical stress for use in design" (p. 1).

"Theoretical buckling stresses are determined in explicit form for circular cylinders with circumferential and axial stiffening. The loadings are axial compression, radial pressure, hydrostatic pressure, and torsion. Analyses were confined to moderate-length and long cylinders" (p. 1).

"The local buckling of stiffener sections and the buckling of plates with sturdy stiffeners are reviewed, and the results are summarized in charts and tables. Numerical values of buckling coefficients are presented for longitudinally compressed stiffener sections of various shapes, for stiffened plates loaded in longitudinal compression and in shear, and for stiffened cylinders loaded in torsion. Although the data presented consist primarily of elastic-buckling coefficients, the effects of plasticity are discussed for a few special cases" (p. 1).

"The local buckling of stiffener sections and the buckling of plates with sturdy stiffeners are reviewed, and the results are summarized in charts and tables. Numerical values of buckling coefficients are presented for longitudinally compressed stiffener sections of various shapes, for stiffened plates located in longitudinal compression and in shear, and for stiffened cylinders loaded in torsion. Although the data presented consist primarily of elastic-buckling coefficients, the effects of plasticity are discussed for a few special cases" (p. 1).

"A comprehensive review of failure of stiffened curved plates and shells is presented. Panel instability in stiffened curved plates and general instability of stiffened cylinders are discussed. The loadings considered for the plates are axial, shear, and the combination of the two. For the cylinders, bending, external pressure, torsion, transverse shear, and combinations of these loads are considered" (p. 1).

Report presenting flight tests to determine the cooling characteristics of a two-row radial engine at altitude in a twin-engine airplane and to investigate the accuracy with which low-altitude cooling-correlation equations can be used for making cooling predictions at higher altitudes. Satisfactory correlation of the cooling variables was obtained at both altitudes by the NACA-cooling method.

"NACA model 11-C was tested with four different depths of step to obtain information as to the effect of the depth of step on the water performance. The depths of step were selected to cover the practicable range of depths and in each case the included angle between the forebody and afterbody keels was kept the same 6-1/2 degrees. Small depths of step were found to give lower resistance at speeds below and at the hump speed of the model and greater depths of step lower resistance at high speeds" (p. 1).

Note presenting an investigation of the instability of flow from two ducts that join into a common duct and of the influence of the various parameters on the phenomenon. A two-dimensional potential analysis was carried out under the assumption that the two ducts discharge into a region of constant pressure.

"Chaplygin introduced the hodograph method in the theory of compressible fluid flows and developed a method for constructing stream functions of such flows. This method, which has been extensively used in investigation of compressible fluid flows, is limited in certain respects. The expression for the stream function obtained in this manner can represent only certain types of flow patterns. In general, flow patterns obtained in this way cannot represent the whole flow around an obstacle, but only a part of such a flow, and therefore several expressions are needed in order to obtain the whole flow" (p. 1).

Report presenting the use of linearized theory for compressible unsteady flow to treat the problem of a partial-span rectangular control surface hinged at its leading edge and mounted on a rectangular wing, oscillating in supersonic flow. The motions of the wing-aileron configuration are assumed to consist of vertical translation, pitching, and aileron rotation. Results regarding the spanwise aerodynamic effects and application to flutter are provided.

Note presenting the results of spin-tunnel investigations compared with corresponding full-scale results for 60 different airplane designs. The purpose of the comparison was to determine the reliability of the model results in predicting full-scale spin and recovery characteristics. Results regarding the recovery characteristics, angle of attack, rate of rotation, altitude loss per revolution, angle of wing tilt, and emergency spin-recovery parachutes are provided.

"The circulatory subsonic flow around an infinite circular cylinder is computed using the linearized pressure-volume relation, by a method developed in a previous report. Formulas and graphs are given for the velocity and pressure distributions, the circulation, the lift, and the dependence of the critical Mach number upon the position of the stagnation point" (p. 1).

"Results are presented of an investigation to determine the effect of boundary-layer displacement and leading-edge bluntness on surfaces in hypersonic flow. The presence of the boundary layer and the blunt leading edge induce pressure gradients which in turn affect the skin friction and heat transfer to the surface. Methods for predicting these phenomena on two-dimensional surfaces are given and a brief review of recent three-dimensional results is presented" (p. 1).