Report presenting a wind-tunnel investigation to provide data for the study of the effects of operating propellers on the longitudinal characteristics of a four-engine tractor airplane configuration with a wing of 40 degrees of sweepback and an aspect ratio of 10. Coefficients of lift, longitudinal force, pitching moment, propeller thrust, and propeller power are presented in tabular form for various values of advance ratio at constant angles of attack.

Linear-theory values of the supersonic pressure field and wave drag of nonlifting bumped and indented bodies of revolution are presented and compared with the corresponding properties of a smooth body. The comparisons indicate that relatively small surface irregularities cause large pressure disturbances and changes in wave drag. The interference drag produced by bumps and indentations is discussed and a correction for the curvature of the characteristics is applied.

Results are presented of an investigation made to determine the internal friction and fatigue strength of commercially pure 1100 aluminum under repeated stressing in torsion at various temperatures and stress levels in an effort to find if there exists any correlation between internal friction and fatigue characteristics.

Laminar-like and brush-like propane-air flames were obtained when wire grids were used as turbulence generators in a 1/2-inch nozzle burner. The laminar-like flames for grid-disturbed flow had a slightly higher burning velocity than "true" laminar flames (no grid used). The brush-like flames were similar to those obtained with pipe turbulent flow. Their burning-velocity dependence on a "flow disturbance" Reynolds number compared favorably with that obtained for pipe turbulent flames. Hot-wire-anemometer equipment was used to measure the flow disturbance intensity in the cold flow with and without the grids in place.

Report presenting the use of wall perforations on supersonic diffusers to avoid the internal contraction-ratio limitation. Experimental results on a preliminary model of a perforated diffuser at Mach number 1.85 are provided. A theoretical discussion of the flow coefficients and the size and spacing of the perforations are included.

Report presenting an investigation at speeds of up to Mach number 0.90 to determine the effects of operating propellers on the longitudinal characteristics of a four-engine tractor airplane configuration with a 40 degree swept wing with an aspect ratio of 10. Results regarding low-speed conditions, high-speed conditions, components of lift, effect of configuration changes, longitudinal stability, and the reduction of adverse effects of propellers on stability are provided.

Note presenting a semiempirical method for the calculation of the sound field about a source over ground considering the effects of vertical temperature and wind gradients as well as scattering of sound by turbulence into shadow zones. The two adjustable parameters in the formula were obtained from measurements suing a relatively small source height.

"By means of examples, a new method is illustrated for optimizing, over a finite interval of time, time-varying systems with stationary or nonstationary statistical inputs. The method depends on the correlation functions being of a certain type, which, fortunately, is the type found in a large number of practical problems of importance" (p. 1).

Report presenting theoretical design charts based on Neuber's equations for symmetrically located notches in order to estimate the approximate rupture strengths of blade roots made from brittle materials. The ideal proportions for overall root width, neck width, notch radius, and notch depth are determined from the design charts. Results regarding notch specimens, blade-root specimens, the blade-root design procedure, practical limit of the design charts, effect of included angle on dovetail root, and effect of additional load-carrying lands are provided.

Report discussing an aerodynamic investigation of a slender pointed parabolic body of revolution was conducted at Mach number of 1.92 with and without the effects of an annular supersonic jet exhausting from the base.

"From measurements of turbulent shear spectra together with previously reported longitudinal turbulent energy spectra, the concept of local isotropy in a low-speed boundary layer was examined. Results of these measurements and measurements of the time derivatives of turbulent velocities in the x- and y- directions for various frequency bands showed no evidence of local isotropy in the boundary layer. Several methods (based on isotropy) of evaluating the turbulent dissipation term failed to give consistent answers, further emphasizing a lack of local isotropy" (p. 1).

Report presenting a study of clouds of liquid and solid spheres accelerating in airstreams over a range of airstream pressure, temperature, and velocity conditions. Diameter and velocity data for individual droplets and solid spheres in the clouds were obtained with a high-speed camera developed at the NACA Lewis laboratory.

Report presenting an investigation of the wing-body interference of NACA TN 2677 applied to symmetric wings in combination with quasi-cylindrical bodies, which permits the direct calculation of pressure-distribution changes produced by body shape changes. The theory is used to determine the relative magnitude of wave-drag reduction produced by changes in cylinder cross-sectional area and shape.

Pressure cross correlations were obtained over a range of jet velocities both longitudinally and laterally for the overall sound pressure and for several frequency bands. The region of positive correlation was found to increase with distance downstream of the nozzle exit and was greater for lateral than for longitudinal correlations. In general, little change in the correlation curves was found as a function of jet velocity or frequency band width. Measurements made with a fixed and a movable microphone in a plate showed correlations similar to the free-field results. The results are interpreted in terms of pressure loads on surfaces.

An investigation of the stability and control of a low-wing four-engine transport vertical-take-off airplane during the transition from hovering to normal forward flight has been conducted with a remotely controlled free-flight model. The model had four propellers distributed along the wing with the thrust axes in the wing-chord plane. The wing could be rotated to 90 degrees incidence so that the propeller thrust axes were vertical for hovering flight.

"The aerodynamic stability derivatives due to pitching velocity and vertical acceleration are derived for circular cones traveling at supersonic speeds. Both first-order and a combination of first and second order potential solutions are obtained, and in calculations for the forces, no approximations are made to the tangency condition or the isentropic pressure relation. In addition, expressions for the forces, moments, and stability derivatives of arbitrary bodies of revolution are derived from Newtonian impact theory" (p. 1).

Results are given of an analysis of wing and horizontal-tail spar strains measured on a twin-engine light transport airplane which was modified for the installation of a control system to alleviate airplane motions in turbulent air and thus improve passenger comfort. From a sample of the measurements obtained in flight through clear-air turbulence, normal acceleration at the airplane center of gravity was reduced 43 percent, wing main-spar bending strains were reduced, and wing-spar shear strains were increased. Horizontal-tail shear and bending strains were increased. Measurements of aerodynamic loads obtained in a pull-up with the gust-alleviation system in operation are also presented.

Structural efficiency curves are presented for high-strength, stainless-steel, cellular-core sandwich plates of various proportions subjected to compressive end loads for temperatures of 80 F and 600 F. Optimum proportions of sandwich plates for any value of the compressive loading intensity can be determined from the curves. The efficiency of steel sandwich plates of optimum proportions is compared with the efficiency of solid plates of high-strength steel and aluminum and titanium alloys at the two temperatures.

Note presenting a study using grids mounted in the path of traveling shock waves in a shock tube. A description of the behavior of the shock waves is provided.