From Summary: "At the end of 1940 an investigation of a guide-vane lattice for the compressor of a TL unit [NACA comment: Turbojet] was requested. The greatest possible Mach number had to be attained. The investigation was conducted with an annular lattice subjected to axial flow. A direct-current shunt motor with a useful output of 235 horsepower at an engine speed of 1800 qm was available for driving the necessary blower."

From Summary: "The results of altitude-wind-tunnel tests conducted to determine the performance of an axial-flow-type 4000-pound-thrust turbojet engine for a range of pressure altitudes from 5000 to 40,000 feet and ram pressure ratios from 1.02 to 1.86 are presented and the experimental and analytical methods employed are discussed. By means of suitable generalizing factors applied to the measured performance data, curves were obtained from which the engine performance at any altitude for a given ram pressure ratio can be estimated. The data presented include the windmilling drag characteristics of the turbojet engine for the ranges of altitudes and ram pressure ratios covered by the performance data."

"An investigation is being conducted to determine the altitude performance characteristics of the Nene II engine and its components. The present paper presents the preliminary results obtained using jet nozzle 18.00 inches in diameter, with an area equal to 92.2 percent of the area of the standard jet nozzle for this engine. The experimental results presented are for conditions simulating altitudes from 20,000 to 60,000 feet and ram-pressure ratios from 1.1 to 3.5" (p. 1).

Compressor operation at low air flows for a given speed is limited by unstable flow conditions, commonly called surge. An investigation of surge in centrifugal compressors (reference 1) showed that the pulsation of pressures and velocities occurred when the slope of the compressor characteristic curve was positive and that the magnitude and frequency, as well as the incidence of surge, depended on the capacity and resistance of the total system. Although the theory presented in reference 1 is applicable to axial-floe compressors, little experimental information is available on the surge characteristics of the individual stages of axial-flow compressors, or on the variation of the surge characteristics with operating conditions.

Memorandum presenting low-speed wind-tunnel test conducted of a triangular wing of aspect ratio 2.0 with a symmetrical double-wedge section with a maximum thickness of 5 percent of the chord at 20 percent of the chord. The wing was also tested in the presence of a ground plane. Results regarding isolated wing and wing-body combinations, split-flap effectiveness, and ground effect are provided.

Memorandum presenting low-speed wind-tunnel tests made of flat-plate wings with an aspect ratio of 2.0 and their leading edges swept back 63.4 degrees. Both plain and split flaps of several plan forms were investigated to provide qualitative information as to the relative merits of these flaps. The constant-chord flap was found to be the most effective and a skewed wing-tip flap the least effective.

Note presenting results of mechanical tests of several laminated plastics, including canvas laminate molded at low pressure, grade-C canvas laminate, rayon laminate, paper laminate, and glass-fabric laminate. The following tests were performed: static tension, compression, and torsion tests; long-time creep tests at different stresses on specimens loaded in tension; fatigue tests of unnotched specimens in bending; fatigue tests of notched specimens in bending; fatigue tests in bending at temperatures of -75, 77, and 160 degrees Fahrenheit; and fatigue tests in torsion.

Note presenting the development of fundamental equations for the plastic buckling of a rectangular plate under edge thrusts on the basis of a new set of stress-strain relations for the behavior of a metal in the plastic range. The relations are derived for buckling from a state of uniform compression.

"A tabulation is presented of functions of the Mach number which are frequently used in high-speed aerodynamics. The tables include values of Mach number from 0 to 10.0 in increments of 0.01 and the functions are based on the assumption that air is a perfect gas having a specific-heat ratio of 1.400" (p. 1).

From Summary: "Tests were made to determine bearing yield and ultimate strengths of bare and Alclad 15S-W(exp 1) and 14S-T(exp 1) sheet and plate in thicknesses of 0.064 inch, 0.250 inch, and 0.750 inch. From the results of these tests it was concluded that the ratios of bearing to tensile properties from the with-grain direction were essentially the same as proposed in NACA TN Nos. 901, 920, 974, and 981 for other high-strength aluminum-alloy sheet and plate."

Report presenting bearing tests made of aluminum-alloy sand casings of 195-T4, 195-T6, and 356-T6 to evaluate the bearing strength and tensile properties of the alloys. Comparisons with individually cast bars and specimens machined from slabs indicate that size and form of casing may have a significant effect on mechanical properties. Results of the tensile, compressive, and shear tests are provided in charts and include specified minimum and typical properties for comparison.

Note presenting experiments to study the characteristics of low-aspect-ratio wings at supercritical Mach numbers. The experiments consisted of tests of wings of aspect ratios ranging from infinity to 2. The results indicate that the detrimental effects of compressibility in the supercritical speed range on the stability and performance of aircraft are alleviated to a great degree by the use of low-aspect-ratio lifting surfaces.

Note presenting flight-performance measurements made on an untwisted, plywood-covered rotor in the high-speed and vertical-autorotative-descent conditions. The results were compared with measurements on a similar rotor with 8 degrees of linear washout and with theoretical calculations in order to determine the effects of rotor-blade twist on helicopter performance.

Report presenting a low-scale wind-tunnel investigation in both straight and yawing flow to determine the effects of aspect ratio and sweep on the static and yawing stability derivatives for a series of untapered wings. The effects of sweep on the static stability characteristics, including lift-curve slope, drag, and effective-dihedral parameter, generally became smaller as the aspect ratio decreased.

"Direct-reading design charts are presented for 75S-T aluminum-alloy flat compression panels having longitudinal straight-web Y-section stiffeners. These charts make possible the direct determination of the stress and all panel proportions required to carry a given intensity of loading with a given skin thickness and effective length of panel" (p. 1).

Report presenting a graphical method for calculating the linearized lift distribution on thin wings at supersonic speeds. It can be applied to all wing regions except those influenced by interacting flow fields off the wing-plan boundaries.

Note presenting an approximate linearized solution for the wave drag and lift of an airfoil generated by rotating a thin supersonic profile about an axis parallel, or nearly parallel, to its chord. The aerodynamic coefficients are obtained from a surface distribution of sources, of strengths proportional to the local airfoil slopes, about a cylinder whose radius and chord equal those of the original ring airfoil.

Report presenting flight measurements at low speeds to determine the static longitudinal stability, stalling, and lift characteristics of an airplane with a wing sweptback 35 degrees at the quarter-chord line. The airplane was tested without slots on the wing and with slots extending from 40 to 80 percent of the semispan of the sweptback-wing panels measured from the inboard end. Results regarding the static longitudinal stability, stalling characteristics, and lift characteristics are provided.

Report presenting an analysis of the divergence of swept untapered and tapered wings with stiffnesses varying as the fourth power of the chord. The results are presented in a set of charts and approximate formulas that allow for quick estimates of the divergence dynamic pressure and divergence speed.

From Summary: "The plasticity reduction factor in the formula for the buckling stress of a long plate under uniform shear has been computed from the properties of the stress-strain curve for the material. Some limited tests on the shear buckling of 24S-0 aluminum-alloy plates in the plastic region tend to confirm the value of the reduction factor predicted by the theory. Restraint against rotation along the edges of the plate has little or no effect upon the value of the reduction factor according to theoretical calculation."

Report presenting a method to calculate the surface temperatures of bodies in steady flight at any speed in a rarefied gas. Results regarding the incident translational energy, skin temperatures in the absence of solar radiation, internal cooling, the effect of solar radiation on skin temperature, the effect of emissivity on skin temperature, and the effect of accommodation coefficient on skin temperature are provided.

Report presenting an NACA 63(sub 1)-012 airofil section equipped with a single suction slot near the leading edge to determine whether the maximum lift coefficient could be increased by delaying the separation of flow at the leading edge characteristics of the basic section. Maximum lift increased with increasing flow through the slot, rapidly at first, and then at a diminishing rate. Results regarding the effect of boundary layer section and the optimum slot are provided.

From Introduction: "The magnitude of hydrodynamic loads experienced by seaplanes during a landing impact has been investigated experimentally and theoretically by the National Advisory Committee for Aeronautics. The results as reported in references 1 and 2 provide a rational means of determining loads on conventional V-bottom hulls in a step landing."

Report presenting an investigation of a jet diffuser designed to utilize the kinetic energy of the jet from a turbojet engine to reduce discharge pressure at the exhaust nozzle and therefore provide simulated ram-pressure ratios across the engines and altitudes. Curves of performance data for a turbojet engine at several ram-pressure ratios show the range of engine operating conditions obtainable with the jet diffuser.