"When thin-walled columns formed from flanged sheet, such as used in airplane construction, are subjected to axial load, their behavior at failure varies according to the slenderness ratio. On long columns the axis deflects laterally while the cross section form is maintained; buckling results. The respective breaking load in the elastic range is computed by Euler's formula and for the plastic range by the Engesser- Karman formula. Its magnitude is essentially dependent upon the length" (p. 1).

Report discusses the results of bench testing on a German BMW 301D2 to determine the relation between the control parameters and any special methods by which the control principles are adapted to the control of the engine. Characteristics are presented for a variety of simulated manifold pressures, charge-air temperatures, engine speeds, and altitudes. Special attention is paid to the pressure characteristics of the servo-oil system and the potential effects of its failure on the operation of the automatic engine-control system.

Sectional characteristics of airfoil having retractable slotted flap with plain, slot-lip, or retractable ailerons are presented for a large range of aileron deflections. The analysis indicated that pitching moments produced by spoilers were less positive than those produced by plain flaps of equal effectiveness, also that pitching moments created by the spoiler increased less with the Mach number than similar moments produced by plain flaps. Positive values of pitching moment decreased as devices were located nearer airfoil leading edge.

Report presents a comparison of predicted qualities of the A-26B airplane with actual flying qualities determined in testing. From Summary: "The results indicate that the control-fixed, power-off stability and control characteristics of a conventional airplane can be predicted from the dimensions of the airplane and from general wind-tunnel data now available with sufficient accuracy for design purposes. No estimate of control forces, of effects of power on stability, or of adverse aileron yaw has been made."

Bulletin presenting a study of data from various wind-tunnel tests of horizontal tail surfaces to determine the accuracy with which section data can be used to estimate the hinge-moment characteristics of control surfaces of finite span. The study consisted of a comparison between the variations of elevator hinge moments with elevator deflection and with airplane pitching moment, as estimated from data obtained in two-dimensional flow, and that variation measured experimentally on 16 different horizontal tails mounted on wind-tunnel models of complete airplanes.

Report discussing a cooling-correlation equation based on the average temperature of exhaust-valve seats of a large double-row radial engine. From the equation, predicts can be made about the cooling-air pressure drop required to cool the critical region of engine cylinders. Using a modified carburetor to improve the fuel-air-ratio distribution to the cylinders increased the accuracy of the equation's predictions.

"The longitudinal-stability and -control characteristics of a twin-engine patrol airplane as predicted from the results of wind-tunnel tests of a powered model and as measured in flight are compared in this report. The accuracy of the wind-tunnel predictions and the reasons for discrepancies are analyzed and discussed" (p. 1).

From introduction: "This article gives an account of the determination of the complete crystal structures of the normal orthophosphates of barium and strontium."

Report presenting tests with dynamically similar models made to study the behavior of the Army B-17F and B-17G when ditched and to determine the best way to land them in calm and rough water. Various landing attitudes, speeds, and conditions of damage were simulated. The ideal landing condition was found to be in a three-point landing attitude and with the flaps 45 degrees at the slowest possible speed.

Testing conducted to determine the best way to ditch the Army B-24 airplane in calm and rough water and to determine its probable ditching performance. A dynamically similar model was ditched in calm water in tank no. 2 and calm and rough water from an outdoor catapult. Results regarding the effect of attitude and speed, effect of flap setting, effect of vertical velocity, effect of location of center of gravity, effect of simulated damage, effect of ditching aids, effect of fuselage length, effect of landing gear, effect of load, and effect of seaway are provided.

Note presenting an analysis of a procedure for artificially aging assemblies and subassemblies to improve the strength properties of the wrought aluminum alloys comprising their principal structure. Information is given on the magnesium alloys which may be present. The forms in which magnesium alloys may be encountered are casings, extrusions, forgings, and sheet.

Report discussing an investigation to determine the effect of fuel volatility on the relation between mixture temperature and knock-limited performance on a liquid-cooled single-cylinder test engine. The mixture temperature at which the curve of indicated mean effective pressure plotted against mixture temperature becomes nonlinear was found to be independent of fuel volatility. The effects of vaporization on the knock-limited power output are also described.

"The NACA has conducted a flight investigation to improve the cooling characteristics of the installation of a double-row radial engine. The tests reported herein concern the use of the NACA injection impeller and ducted head baffles in various combinations on both the port inboard and the port outboard engines. The performance of the modified installation was evaluated by comparing it with that of the standard engines" (p. 1).

Abstract. Measurements were made to determine the effect of thermal cycling on heat transfer from slug to jack using a slug with a sand blasted surface. The value of the transfer coefficient h decreased from initial values ranging from 10 to [formula], to values and [formula] after 1700 cycles, and to a range of 0.15 to 0.45 [formula] after 3200 cycles. Comparisons are made with the results found for slugs with different surfaces.

Report discussing the effect of valve clearance on valve-lift diagrams, knock-limited performance, and engine cooling. The performance of single-cylinder and multicylinder engines was also compared across these variables.

Report discusses the effects of compressibility and angle of yaw on the pressure measured by a round-nose and a flat-nose total-pressure tube. The error incurred in the pressure measurements and factors affecting the total-pressure area are described.

Report presenting efficiency tests on a single-stage impulse turbine with an 11.0-inch pitch-line diameter wheel and a fabricated nozzle diaphragm with air at moderate temperature as the driving fluid. Results regarding the variation of turbine efficiency with blade-to-jet speed ratio over a range of turbine pressure ratios and maximum efficiency are provided.

Report presenting a boundary-layer-transition and profile-drag investigation conducted on an experimental low-drag wing installed on a P-47 airplane designated the XP-47F. Measurements were made at a section outside the propeller slipstream with smooth and with standard camouflage surfaces and on the upper surface of a section in the propeller slipstream with the surface smoothed. Results regarding the right wing section outside the slipstream and left wing section in the propeller slipstream are provided.

Report presenting a boundary-layer transition and profile-drag investigation on an experimental low-drag wing installed on a P-47 airplane designated the XP-47F and supplied by the Army Air Forces. Measurements were made at a section outside the propeller slipstream with smooth and with standard camouflage surfaces and on the upper surface of a section in the propeller slipstream with the surface smoothed.

Report discussing tests on three sets of elevators with various combinations of section contour, balancing tabs, bobweights, and control-system mechanical advantage on an SB2C-1C airplane. Effects on maneuvering stability, a comparison of production elevators and recommended arrangement, and internal elevator pressures are described.

Tests were made to determine whether spring-tab ailerons tended to oscillate or flutter in speed ranges up to 400 mph. Flight tests showed spring-tab ailerons had desirable light stick forces and no tendency to overbalance. No flutter tendencies were indicated up to 400 mph, and any oscillations following abrupt control deflections were heavily damped.

Report discussing testing of an HNS-1 (Army YR-4B) helicopter to determine the hovering data in the ground-effect region and at altitude with an original set of rotor blades and an alternate set with different aerodynamic design and surface condition.

Report discussing basic performance data obtained on the PV-2 helicopter rotor. Blade motion, rotor forces, and power were measured for static-thrust condition and a limited range of forward-flight conditions. Recommendations are provided for further testing to obtain blade-motion data and force-test data in order to develop a more detailed analysis.

Report presenting a method for showing, by means of three curves, the locations of points of tangency to the envelope of the main-spray blisters generated by flying boat hull models obtained from general testing. Three equations are applied to data from general spray testing on seven models.