Report in two parts: one examines the boundary conditions for an open wind tunnel with special references to the effects of the closed entrance and exit sections, while the other derives solutions of four types of two-dimensional open tunnels, including one in which the pressures on the two free surfaces are not equal.

Note presenting an analysis and comparison of atmospheric turbulence as experienced by rocket-powered models and temperature lapse-rate data obtained from rawinsonde soundings in 38 cases by using an assumed temperature lapse-rate stability boundary as a basis for comparison. A limited correlation has been obtained which indicates that atmospheric conditions classified as being unstable will generally be turbulent, but a marginal or stable classification does not necessarily indicate smooth air.

From Summary: "By the use of a form of the Prandtl-Glauert method that is valid for three-dimensional flow problems, the value of the maximum incremental velocity for compressible flow about thin ellipsoids at zero angle of attack is calculated as a function of the Mach number for various aspect ratios and thickness ratios. The critical Mach numbers (within the accuracy of the Prandtl-Glauert method) of the various ellipsoids are also determined. The results indicate an increase in critical Mach number with decrease in aspect ratio which is large enough to explain experimental results on low-aspect-ratio wings at zero lift."

Report presenting a theoretical approach to determine the lateral frequency response of a fighter airplane to side gusts and rolling gusts at a Mach number of 0.7 and an altitude of 30,000 feet. Frequency response and power spectral density were determined with the controls fixed and in combination with three different basic types of attitude autopilots.

Note presenting an analysis based on simple geometry of the effect of thrust-axis inclination on propeller disk loading. Calculations are in excellent agreement with available flight measurements, so that the analysis is indicated to be adequate for predicting the primary effects of inclination. Because of the possible large effects of wing and fuselage interference, flow angles at the propeller should be determined by survey for most accurate results.

Note presenting pressure-distribution expressions and stability derivatives derived by use of linear theory for zero-end-plate triangular vertical tails with subsonic leading edges performing rolling, yawing, and constant-lateral-acceleration motions. Corresponding results for the sideslip motion, most of which have been previously reported, are also included.

Report presenting transient data from approximate step and sinusoidal disturbances of fuel flow on a turbojet engine operated at one constant simulated altitude and flight condition. Results regarding coefficients of differential equations, Fourier representation, frequency response, transient analysis, and a comparison of the various analytical methods are provided.

Note presenting the nondimensional lift derivative and the corresponding pitching-moment derivative resulting from constant vertical acceleration as evaluated for a family of thin sweptback tapered wings with streamwise tips traveling at supersonic speeds. The analysis is applicable at those speeds for which the wing leading and trailing edges are both supersonic, provided that the Mach lines from the wing apex intersect the trailing edge and that the Mach line from the leading edge of one tip does not intersect the remote half-wing.

Note presenting a flight investigation of a three-blade propeller in climb and at high speed to determine the effects of blade power loading. Increasing the blade power coefficient from 0.06 to 0.09 was found to increase the efficiency approximately 8 percent at an airplane Mach number of 0.7 and a propeller-tip Mach number of 1.13. In climb, an increase in power loading over the range of blade power coefficients investigated was shown to reduce efficiency, as a consequence of increased induced drag losses.

Report presenting an investigation of the methods of analyzing longitudinal frequency-response characteristics of aircraft. The methods considered are analysis of sinusoidal response, analysis of transient response to harmonic content through determination of the Fourier integral, and analysis of the transient through the use of least-squares solutions of the coefficients of an assume equation for the transient time or frequency response.

Note presenting fairing compositions applied to aircraft surfaces, welds and junctions of metal plates, and rivet depressions to improve the aerodynamic efficiency of the airplane at high speeds. A method is described for formulating fairing compositions which have, within limits, desired coefficients of thermal expansion. Results regarding water-immersion tests, thermal expansion and softening temperature, temperature-cycle tests, and density are provided.

Note presenting tables of thermal properties of stream that have been prepared in an NBS-NACA series. They include, for real gas, the compressibility factor, the density, the specific heat at constant pressure, the enthalpy, the entropy, the free-energy function, the viscosity, and the thermal conductivity.

Report presenting a theoretical investigation of the contribution of horizontal tails to the lift and pitching moment due to angle of attack, a constant rate of pitch, and a constant vertical acceleration. Methods for calculating the flow fields behind wings with constant vertical acceleration are developed.

Report presenting an analysis of the time-dependent downwash behind a wing in a supersonic stream when the angle of attack varies linearly with time. The result is applied to the calculation of the contribution of the horizontal tail to the pitching moment and lift due to normal acceleration of the airplane. Results regarding downwash charts and some limitations on the results are provided.

Note presenting a method for determining the time-dependent flow over a rectangular wing moving with a supersonic forward speed and undergoing small vertical distortions expressible as polynominals involving spanwise and chordwise distances. The solution for the velocity potential is presented in a form analogous to that for steady supersonic flow with the familiar "reflected area" concept.

Report presenting the analysis of the stability derivatives of low-aspect-ratio triangular wings at subsonic and supersonic speeds, which is extended to apply to triangular wings having large vertex angles and traveling at supersonic speeds.

Although the corrosion resistance of sheet duralumin can be greatly improved by suitable heat treatment, protection of the surface is still necessary if long life under varied service conditions is to be insured. The coatings used for this purpose may be grouped into three classes: the varnish type of coating, the oxide type produced by a chemical treatment of the surface, and metallic coatings, of which aluminum appears to be the most promising. Since the necessary weather exposure tests are not complete, some of the conclusions regarding the value of various surface coatings are necessarily tentative.

"A convenient method has been developed for determining the scavenging efficiency or the charging efficiency of two-stroke-cycle engines. The method consists of introducing a suitable tracer gas into the inlet air of the running engine and measuring chemically its concentration both in the inlet and exhaust gas. Monomethylamine CH(sub 3)NH(sub 2) was found suitable for the purpose as it burns almost completely during combustion, whereas the "short-circuited" portion does not burn at all and can be determined quantitatively in the exhaust" (p. 1).

"A study of the subsonic flow past an infinitely long corrugated circular cylinder is presented to show the relation between two-dimensional and axisymmetrical flow. In fact, a solution is obtained which contains as limiting cases both the Prandtl-Glauert correction for two-dimensional flow and the Göthert correction for flow past slender bodies of revolution. Included in the paper are velocity-correction formulas for a cylinder with a single bump and for a corrugated cylinder in the presence of walls" (p. 1).

From Introduction: "The design of turbojet-engine control systems is intimately related to the dynamic characteristics of the engine and has advanced to the stage where theoretically correct control constants can be determined for fixed dynamic properties (references 1 and 2). The use of the thermodynamic equations presupposes that the engine processes are quansi-static. Such an assumption is shown to be valid for a turbojet engine in references 3 and 4.

Note presenting wind-tunnel calibrations of three types of angle-of-attack sensing devices - the pivoted vane, the differential pressure tube, and the null-seeking pressure tube. Flight data on the position errors for three sensor locations - ahead of the fuselage nose, ahead of the wing tip, and on the forebody of the fuselage - are also presented. Various methods for calibrating angle-of-attack installations in flight are briefly described.

From Introduction: "It is the purpose of this paper to describe the physical properties that are necessary to specify mixture quality in a system containing fuel and dry air and to evaluate the theoretical rolation between these properties and the physical properties of the mixture."

Note presenting a summary of the effects of plan form and thickness on the lift and drag characteristics of wings at transonic speeds. The data were obtained in the high-speed 7- by 10-foot tunnel by the transonic-bump method over a range of Mach numbers. Results regarding lift, drag at zero lift, and drag due to lift are provided.

Report presenting an investigation of the use of the transonic similarity law for two-dimensional flow by an iteration procedure. The results indicated that potential can be expressed as a power series in a single parameter that depends on Mach number, thickness ratio, and ratio of specific heats.