The appearance of expressed discontinuity layers in the free atmosphere, where a warm air mass flows over a cold mass without perceptible intermingling forms the basis of the present report. In these experiments an air stream is to be blown between a water-cooled and a vapor-heated plate. According to what preceded it is anticipated that the exchange will be enhanced.

This report presents a description, diagrams and photographs of the Charlestop remote brake system. A description of the brake system and diagrams showing the individual components are provided.

Equations are presented for two and three dimensional strut systems along with tables of equations.

This report presents test results obtained during an investigation of the performance of a single-cylinder, high-speed, compression-ignition test engine when using multiple-orifice fuel-injection valve nozzles in which the number and the direction of the orifices were varied independently.

The purpose of the study was to develop improvements in the current methods for the calculation of the loads in members of metal truss wing spars which are subjected to combined bending and compression. The theory developed here has two important practical applications. One is the calculation of the effective moment of inertia of a truss spar from the geometry of the spar and the loads to which the spar is to be subjected. The second is the determination of the most economical location of metal for stiffening a truss spar which has too much deflection.

"The effect of various injection-valve opening pressures on the spray-tip penetration was determined for several injection pressure. A common-rail fuel injection system was used. For a given injection pressure a maximum rate of penetration was obtained with an injection-valve opening pressure equal to the injection pressure" (p. 1).

"This paper is the first of a series covering an investigation of a family of airfoils all formed from a basic profile. It gives in preliminary form the results of six symmetrical airfoils, differing only in maximum thickness. The maximum thickness-to-chord ratios are 0.06, 0.09, 0.12, 0.15, 0.18, and 0.21" (p. 1).

Tests of nine symmetrical airfoils, having different leading-edge radii, were made in the variable density wind tunnel. Three symmetrical NACA airfoils having maximum thickness-to-chord ratio of 0.06, 0.012, and 0.018 were used as basic (or normal) sections; and for each of these thicknesses one thinner and one blunter nose section were developed. Although the slope of the lift curve varies with thickness, these tests show that for any given thickness the slope is independent of nose radius.

This note presents the results of flight pressure-distribution tests on the right upper wing panel of a Douglas M-3 airplane equipped with a modified elliptical tip having a slight amount of washout. The results are given in tables and curves in such form that the load distribution for any normal force coefficient within the usual range encountered in flight may be determined.

In connection with the development of a method for analyzing indicator cards taken from high-speed compression-ignition engines, this investigation was undertaken to determine the average quantity of fuel discharged during each crank degree of injection period.

Theoretical relations involved in the study are reviewed to furnish a basis upon which experimental data can be properly analyzed. The structure of the atmosphere in relation to the load-factor problem is briefly discussed, and the acceleration data obtained on a number of flights with various airplanes are presented and analyzed to the extent that the results are applicable to n=any airplane.

This paper, which is the first of a series presenting the results of such measurements, gives the momental ellipsoids of ten army and naval biplanes and one commercial monoplane. The data were obtained by the use of a pendulum method, previously described. The moments of inertia are expressed in coefficient as well as in dimensional form, so that those for airplanes of widely different weights and dimensions can be compared.

"By means of the NACA Spray Photography Equipment high speed moving pictures were taken of the formation and development of fuel sprays from an automatic injection valve. The sprays were injected normal to and counter to air at velocities from 0 to 800 feet per second. The air was at atmosphere temperature and pressure. The results show that high air velocities are an effective means of mixing the fuel spray with the air during injection" (p. 1).

A multiple manometer designed to integrate automatically the normal force over an airfoil section is described and its mathematical theory explained. The development of this instrument was conducted at the Langley Memorial Aeronautical Laboratory.

Although the strong aluminum alloys have proved themselves to be very efficient in aircraft construction there is a growing competition from the high-strength steels for certain parts, especially for tubular members. This tendency is being reflected in research work carried on at the Bureau of Standards. This study will be based largely on data given in Technical Note No. 307 of the NACA.

This note presents the results of flight pressure distribution tests on the right upper wing panel of a Douglas M-3 airplane equipped with a semicircular wing tip. The results are given in tables and curves in such form that the load distribution for any force coefficient within the usual range encountered in flight may easily be determined.

The desirability of a quantitative measure of turbulence is emphasized, and a possible method of attack on the problem is discussed. Data are presented to show that the hot-wire anemometer has possibilities as an instrument for measuring turbulence. An apparatus consisting essentially of two hot wire, one parallel to the air flow and one at right angles to it, is suggested.

"The low temperature endurance properties of materials for aircraft construction are not well known. In order to determine them, apparatus for testing endurance at -40 C has been devised. The endurance properties of monel metal, low-carbon stainless steel, "18 and *, " 3 1/2% Ni steel and chromium-molybdenum steel have been determined at -40 C and at room temperature about +20 C. Tensile, impact and hardness tests of these materials have also been made at various temperatures" (p. 1).

"This report presents the results of tests conducted at the Langley Memorial Aeronautical Laboratory, Langley Field, Va., to determine some of the characteristics of the fuel sprays obtained from an 0.008-inch and a 0.020-inch open nozzle when injection pressures from 100 to 500 pounds per square inch were used. Fuel oil and gasoline were injected into air at densities of atmospheric land 0.325 pound per cubic foot. It was found that the penetration rate at these low pressures was about the same as the rate obtained with higher pressures. Spray cone-angles were small and individual oil drops were visible in all the sprays. Gasoline and fuel oil sprays had similar characteristics" (p. 1).

The variation of the coefficient of discharge with the length-diameter ratio of the orifice was determined for nozzles having single orifice 0.008 and 0.020 inch in diameter. Ratios from 0.5 to 10 were investigated at injection pressures from 500 to 5,000 pounds per square inch. The tests showed that, within the error of the observation, the coefficients were the same whether the nozzles were assembled at the end of a constant tube or in an automatic injection valve having a plain stem.

"Static tests on paper cylinders were conducted at the Langley Memorial Aeronautical Laboratory at Langley Field, Virginia, to obtain qualitative information in connection with a study of the strength of stressed-skin fuselages. The effects of radius-thickness ratio and bulkhead spacing were investigated with the cylinders in compression, bending, combined bending and shear, and torsion" (p. 1).

This report describes test made in the Variable Density Wind Tunnel of the NACA to determine the possibility of controlling the boundary layer on the upper surface of an airfoil by use of the low pressure existing near the leading edge. The low pressure was used to induce flow through slots in the upper surface of the wing. The tests showed that the angle of attack for maximum lift was increased at the expense of a reduction in the maximum lift coefficient and an increase in the drag coefficient.

"During an investigation to determine the possibilities and limitations of a two-stroke-cycle engine and ignition, it was necessary to develop a fuel injection valve nozzle to produce a disk-shaped, well dispersed spray. Preliminary tests showed that two smooth jets impinging upon each other at an angle of 74 degrees gave a spray with the desired characteristics. Nozzles were built on this basis and, when used in fuel-injection valves, produced a spray that fulfilled the original requirements" (p. 1).

The first flights of the Oehmichen helicopter are detailed as well as various aspects of the construction.