From Summary: "The second part of a series of tests made in Langley tank no. 2 to determine the effect of varying design parameters of planing-tail hulls is presented. Results are given to show the effects on resistance characteristics of varying angle of afterbody keel, depth of step, and length of afterbody chine. The effect of varying the gross load is shown for one configuration. The resistance characteristics of planing-tail hulls are compared with those of a conventional flying-boat hull. The forces on the forebody and afterbody of one configuration are compared with the forces on a conventional hull."

Note presenting tests under combined axial load and normal pressure on 29 24S-T aluminum alloy sheet-stringer panels. Empirical formulas were derived for predicting the effect of normal pressure on the strain for buckling of sheet between stringers. Results of buckling, sheet load, strains, buckling, and failure are provided.

Report presenting an investigation of the influences of shank form and pitch distribution on the characteristics of constant-speed propellers as determine from the wakes of eight model propellers. The experiments show that an improvement in efficiency occurs from the substitution of faired shanks for round ones, which is caused by disproportionate local augmentations of thrust and torque. Results regarding a comparison with force tests, method of comparing performance characteristics, effects of shank form, effects of pitch distribution, independence of blade elements, and section lift characteristics are provided.

Report presenting general tank tests of a scale model of the hull of the Boeing XPBB-1 flying boat in tank no. 1. Testing occurred on the forebody alone, the forebody with the afterbody, and the forebody with the afterbody and tail extension, which represented the complete hull. Results regarding the resistance, trimming moment, and length of the planing bottom wetted by the water are provided.

"In order to determine the crystal structure of some currently used heat-resisting alloys, a preliminary investigation of eight leading forged alloys - S816, S590, Gamma Columbium, Hastelloy B, 16-25-6, 19-9 DL, Nimonic 80, and N155 (low carbon) - was conducted by X-ray diffraction methods. The predominant phase in each alloy was found to be a solid solution of the chief alloying elements. The crystal structure of the solid solution was the face-centered cubic type" (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 Introduction: "Because of the importance of spray height, it is the purpose of the work considered in this report to attempt to determine a correlation for the main spray height in relatively smooth water."

Note presenting a determination of the effects of large variations of the directional-stability derivative and the rotary-damping-in-yaw derivative on the lateral stability and control characteristics of a free-flying model via flight tests. The effects of each parameter were investigated for three values of the lateral-force derivative.

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.

Report presenting the effects of wide variations of dihedral, vertical-tail area, and lift coefficient on lateral stability and control and on general flying characteristics as determined by flight tests in the free-flight tunnel. The geometric dihedral angle and vertical-tail angle were varied in order to vary the effective dihedral angle and directional stability of the model. Results regarding spiral stability, oscillatory stability, lateral control, and general flight behavior are provided.

From Summary: "Bending-stress and bending-moment coefficients are presented for application to design of circular shell-supported fuselage frames of variable cross section for applied radial load, applied moment, and applied tangential load. A ring which is properly reinforced in the region of maximum bending moment is shown to have a structural efficiency higher than that of a similar ring of uniform cross section. The structural efficiency is given in terms of the relative weights of the reinforced and nonreinforced rings."

Report presenting a two-dimensional wind-tunnel investigation made of two interchangeable sealed 0.22-airfoil-chord internally balanced ailerons on an NACA 65(sub 112)-213 airfoil. One aileron tested was of true airfoil contour and the other was modified by partly eliminating the cusp near the trialing edge. Results regarding aileron effectiveness, aileron hinge moments, lift, drag, and airfoil pressure distribution and critical Mach number are provided.

Note presenting performance parameters for jet-propulsion engines developed from the concepts of flow similarity, inertia forces, elastic forces, viscous forces, and thermal expansions of the working fluid. The analysis relates performance to the geometry of the boundaries, Mach number, Reynolds number, and total-temperature ratio.

Note presenting an application of the theory of Lagrangian multipliers to the problem of finding both upper and lower limits to the true compressive buckling stress of a clamped rectangular plate.

Report presenting aerodynamic testing of 12.208-foot-diameter two-blade hollow steel propellers before and after alteration for thermal de-icing in the 16-foot high-speed tunnel to determine the effect of the alterations on propeller efficiency. The propeller had Clark Y blade sections tested on a 2000-horsepower dynamometer at a range of blade angles and airspeeds. Results regarding accuracy, the effect of the alteration, effect of internal air flow, effect of compressibility, and coefficient of mass flow of de-icing air are provided.

From Introduction: "The results of the tests made with unheated internal flow are reported in reference 1. It is the purpose of this paper to attempt to express simply the efficiency loss as a function of the parameters which govern propeller operation and the internal air flow. The derived equations are correlated with the data presented in reference 1."

Report presenting flight testing at altitudes of 5000 and 20,000 feet to investigate the cooling-air pressure recovery and distribution for a two-row radial engine enclosed in a low-inlet-velocity cowling for a twin-engined airplane. The effect of flight variables on average recovery and circumferential, radial, and longitudinal distribution are presented for level flight; also included is a comparison of pressure-drop measurements across the engine, as indicated by nine different combinations of pressure tubes.

"The effect of several parameters on the drag characteristics of practical-construction wing sections have been considered and evaluated. The effects considered were those of surface roughness, surface waviness, compressive load, and de-icers. The data were obtained from a number of tests in the Langley two-dimensional low-turbulence tunnels" (p. 359).

From Summary: "The development and the use of a chart for estimating the pressure losses in jet-engine combustion chambers are described. By means of the chart, the pressure losses due to fluid friction and to momentum changes in the air flow accompanying combustion can be separately evaluated. The over-all pressure losses computed from the pressure-loss chart are within 7 percent of the experimental values for the three types of combustion chambers considered herein."

Symbols and definition of various airspeed terms that have been adopted as standard by the NACA subcommittee on aircraft structural design are presented. The equations, charts, and tables required in the evaluation of true airspeed, calibrated airspeed, equivalent airspeed, impact and dynamic pressures, and Mach and Reynolds numbers have been compiled. Tables of the standard atmosphere to an altitude of 65,000 feet and a tentative extension to an altitude of 100,000 feet are given along with the basic equations and constants on which both the standard atmosphere and the tentative extension are based.

"A preliminary analysis has been made of the conditions of stability of free oscillations of a hinged rotor in hovering flight. The case analyzed is a rotor with hinges allowing freedom in flapping and lagging and having a completely reversible cyclic pitch-control system, so that a twisting moment on a blade moves the control stick without hindrance from spring or friction constraint. The principal results of this study are presented in the form of a stability chart" (p. 1).

Report discussing the effects of various inlet pressures, inlet temperatures, wheel speeds, pressure ratios, and cooling-air flows on the performance of a radial-flow exhaust-gas turbosupercharger turbine with a 12.75-inch tip diameter. Information about efficiency is provided for a given blade-to-jet speed ratio.

Results of flight tests of a control-feel aid presented. This device consisted of a spring and dashpot connected in series between the control stick and airplane structure. The device was tested in combination with an experimental elevator and bobweight which had given unsatisfactory dynamic stability and control-feel characteristics in previous tests. The control-feel aid effected marked improvement in both the control-feel characteristics and the control-feel dynamic longitudinal stability of the airplane.

Report discussing the icing characteristics of a rectangular-throat pressure-type carburetor. Serious ice was not found to form under the conditions of this particular test, although visible ice and frost formed in certain areas.