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.

The following report records the study of albino rats subjected to beta rays and analyzes the skin reactions and metabolic patterns.

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.

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 issued by the U.S. Bureau of Mines on the motor fuels sold during the winter of 1945-46. The characteristics of the fuels sold, and the regions they were sold in are listed. This report includes tables, and maps.

Technical report describing a procedure for the determination of lead in pitchblende. The procedure was determined as needed in the course of an investigation of the processing of pitchblende for the production of uranium. Summary: The volumetric dichromate method for the determination of lead was selected from among several methods investigated as being best suited for a rapid determination of lead in pitchblende. The method as described is accurate to within 1% and it does not require the application of an empirical factor as suggested by Willard and Diehl for this determination.

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.

Problems in extrapolation of the rate of tumor formation by strontium 89 from animal to man are addressed. Focus of this paper is on variability of latency period between different animals.

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 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.

From Abstract: "The use of the oxalic acid method for the separation of uranium from mixed thorium-uranium peroxides has been investigated, and appears to be the most satisfactory of the obvious methods of separation. One oxalic acid leach removes nearly all of the uranium from the thorium with approximately one mg Th/L remaining in the uranium solution phase."

"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).

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 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.

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.

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 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.

"The investigation of the flow in a centrifugal pump indicated that the flow patterns in frictional fluid are fundamentally different from those in frictionless fluid. In particular, the dead air space adhering to the section side undoubtedly causes a reduction of the theoretically possible delivery head. The velocity distribution over a parallel circle is also subjected to a noticeable change as a result of the incomplete filling of the passages" (p. 1).

Report presenting flight measurements made to determine the characteristics of a pair of experimental ailerons designed to provide a close degree of balance and maintain a linear variation of aileron effectiveness with aileron angle through a large deflection range. Results regarding the small-deflection tests, large-deflection tests, effect of stretch on stick forces, and analysis of extended-span ailerons are provided.

"The object of the present work is first to investigate accurately the processes during stress corrosion, in particular, for light metal alloys and, as the first part of the investigation, to determine its laws; and secondly to explain its causes for various alloys and thereby find means for its partial or complete elimination and thus make possible the production of light metal alloys free from any stress corrosion. In the present paper some of the results of the investigation are given and the fundamental problems of stress corrosion discussed" (p. 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.

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.

"Flight tests of an A-26B airplane have been conducted to determine the changes in maximum speed, as affected by changes in carburetor ram and aerodynamic refinement of the nacelles, resulting from the addition of sealed spinners and modification of the charge air system, cowling, and nacelle afterbodies. The changes in nacelle drag resulting from these modifications were measured independently by means of a revolving wake survey rake behind the nacelle and boundary layer rakes on the cowling, and provide a quantitative check of the speed measurements as well as a means of analyzing the components of nacelle drag" (p. 1).

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