"An analysis shows that the scattering of unpolarized plane light waves which penetrate turbulent, transparent gases provides a measure of the average integral scale and intensity of the turbulent density fluctuations. The analysis is based upon the scattering coefficient deduced by Booker and Gordon and, thus, assumes isotropic fluctuations having an exponentially decaying (Markoffian) correlation function. Photometric data taken through turbulent boundary layers in air are found to conform functionally with the analytical prediction" (p. 1).

Note presenting an evaluation of the existing theories of linearized tire motion and wheel shimmy. A series of systematic approximations to the summary theory is developed for the treatment of problems too simple to merit the use of the complete summary theory. Procedures are discussed for applying the summary theory and its systematic approximations to the shimmy of more complex landing-gear structures than have previously been considered.

Report presenting surveys made through a turbulent boundary layer on a flat plate by means of a pitot probe, an X-ray densitometer, and hot-wire and cold-wire probes. Results were analyzed to determine the reliability of basic data and how well the distributions of properties in the boundary layer compare with those assumed in theoretical analyses.

"Experimental results of lifts and moments about the quarter chord of a two-dimensional wing at subsonic Mach numbers are presented. A comparison of the experimental magnitude of the lift vector with the theory as given by Dietze showed good agreement. Comparisons of the moments and the quadrature component of lift with theory indicated that some refinements in the testing technique are necessary for the experimental determination of these quantities in the transonic range" (p. 1).

Report presenting fatigue testing in rotating bending on severely notched bars machined from 2024-T4 aluminum-alloy extruded round rods. Two sizes of specimens were studied.

Note presenting an investigation using rocket-powered models to provide an experimental comparison with linearized theoretical calculations for zero-lift drag of sweptback tapered wings with thin, symmetrical, double-wedge airfoil sections. The linearized theory compared very favorably with the experimental results over most of the test range.

"Tests utilizing the schileren method of flow photography have been conducted to provide a comparison of the complete flow fields past an unswept- and a swept-wing-body combination and the flow fields past their equivalent bodies of revolution at Mach numbers around 1.0. The results indicated that the shock growth and positions on the wing-body combinations were closely reproduced in the flow past the equivalent body" (p. 1).

Report presenting the results of an investigation on the flutter of propeller blades with three different plan forms. The propellers tested included one with highly twisted 2-percent-thick blades, 6-percent-thick blades, and two sets of 3-percent-thick blades with different internal damping. Results regarding the effect of various parameters on the stall flutter boundaries and blade stresses near the flutter boundary are provided.

Results are presented from an investigation of the variation with Reynolds number and Mach number of the total, base, and skin-friction drag of seven boattail bodies of revolution designed for minimum wave drag according to the theory of NACA-TN-2550. The tests covered a Reynolds number range from approximately 1.0 x 10(6) to 10.0 x 10(6) at Mach numbers of 1.62, 1.93, and 2.41 respectively.

Report presenting an investigation in the 300 mph 7- by 10-foot tunnel and gust tunnel to determine the static longitudinal aerodynamic characteristics an the gust-alleviation capabilities of forward-located fixed spoilers, deflectors, or a spoiler-deflector combination on a simulated transport airplane model with an unswept wing. Results regarding the static/force test, dynamic/gust-tunnel test, and short-period frequency and damping are provided.

Note presenting some analytical means by which designers may estimate the elevator deflection required to trim in steady longitudinal flight and to demonstrate in a quantitative manner the effects on longitudinal trim of changes in some of the more important design parameters. The procedures can result in a design in which the maximum up-elevator deflection can be maintained within the highest value that will result in satisfactory damping in roll and reliable lateral control under all flight conditions, while, at the same time, adequate longitudinal control is available.

Report presenting the results of flight tests with several typical light aircraft. Flight tests were made with one airplane with two different horizontal tail configurations in an attempt to provide an arrangement that would give optimum conditions with regard to the effect of power change on longitudinal trim near the stall. The results are intended to provide quantitative flight-test information which may be useful to designers in attempting to provide for adequate low-speed control and which may be correlated with analytical analyses.

Note presenting an investigation indicated that nominal additions of 0.1, 1.0, and 5.0 weight percent copper and magnesium to aluminum have significant effects on damping behavior. An internal-friction peak at abotu 125 degrees Celsius was observed in aluminum containing 1 percent copper and is believed to result from the interaction of dislocations and impurity particles. The internal friction during plastic deformation was sensitive to strain rate, amount of strain, alloy content, heat treatment, temperature, and the frequency at which the measurements are made.

Report presenting an investigation to determine the effect of type and location of impact damage on the fatigue strength of jet-engine compressor blades. The most serious damage was found in the nicks at the leading and trailing edges in the vicinity of the maximum-vibratory-stress section of the airfoil. Results regarding stress distribution in the blades, fatigue of the damaged blades, the fatigue test results, the correlation of reduction in strength, an analysis of the results, and testing using reworked blades are provided.

Report presenting a method for obtaining a power spectrum of gust vertical velocity over a wide range of wavelengths from simultaneous measurements in flight. It has the advantage of not involving the use of airplane transfer functions. Results regarding the measurements of velocity, including long-period and short-period measurements, and a composite spectrum over the range of frequencies are provided.

Report presenting a method for obtaining influence coefficients for thin low-aspect-ratio wings of built-up construction. Symmetric and anti-symmetric load-support conditions are considered. A simple method is given for taking account of attachment to a flexible fuselage.

Note presenting an analysis of fixed- and free-turbine engines applicable to helicopter propulsion. Generalized performance charts are presented for the engines and comparisons are made of off-design specific fuel consumption, altitude performance, power-speed characteristics, and response times. At design shaft speeds and turbine-inlet temperature ratios, the equivalent power developed by both the fixed- and free-turbine engines was about 91.4 horsepower per pound of air per second.

"A preliminary investigation was made of self-excited vibrations of single planing surfaces. A self-excited oscillation requiring freedom in rise but not in trim occurred with high aspect ratio (order of 10) of the wetted portion. This vibration could be controlled most successfully by methods (such as the use of dead rise) which limited the wetted aspect ratio" (p. 1).

Damping-in-roll coefficients for a series of triangular plan-form wings and two rectangular plan-form wings have been obtained from supersonic-tunnel tests. The wings were mounted on a body of revolution and tested at Mach numbers of 1.62 and 1.92.

Note presenting an investigation of the problem of selecting heat-exchanger configurations for optimum performance. The method of optimization is illustrated for several compact heat-exchanger configurations where a prescribed amount of heat is transferred. The results for heat-exchanger configurations for which data is reported in the literature are presented in the form of charts illustrating the method of analysis and results that can be drawn.

Report presenting an analysis of temperatures and thermal stresses in typical skin-stiffener combinations of winglike structures subjected to aerodynamic heating using an electronic differential analyzer. Variations were made in aerodynamic heat-transfer parameter, in a joint conductivity parameter, and in the ratio of skin width to skin thickness. Results regarding data obtained,an illustrative example, temperature and stress ratios, and peak stress ratios and temperature-ratio drop across joint are provided.

Note presenting general equations for the linear responses of inner- and outer-spool speed to change in turbine-inlet temperature and exhaust-nozzle area are derived and evaluated from hypothetical two-spool-engine characteristics at design speed. Experimental corroboration of analysis is also provided in the form of response to fuel flow, response to exhaust-nozzle area, and response to turbine-inlet temperature are provided.

Report presenting the results of wind-tunnel tests of three wing models with various aileron configurations to determine information about single-degree-of-freedom flutter. Results regarding the effect of density on the onset of oscillation, buzz frequency and amplitude, and formation of shock waves are provided.

Note presenting measurements of space heating rate, which can yield information that is useful in characterizing turbulent combustion. For Bunsen burner flames stabilized over a field of pipe-induced turbulence, the space heating rate decreased with increasing linear flow and burner diameter and was independent of pilot conditions. Results regarding residual heat values, space conversion rate, turbulent burning velocities, and a comparison of concepts are provided.