Report discussing the aerodynamic characteristics of a twin-fuselage pursuit airplane model, especially at high speeds. Information about the force data and critical Mach numbers for parts of the model is provided. Suggestions for increasing the Mach number of divergence by making modifications to the wing-fuselage fillets and external shape of the radiator are also included.

Critical Mach number as function of lift coefficient is determined for certain moderately thick NACA low-drag airfoils. Results, given graphically, included calculations on same airfoil sections with plain flaps for small flap deflections. Curves indicate optimum critical conditions for airfoils with flaps in such form that they can be compared with corresponding results for zero flap deflections. Plain flaps increase life-coefficient range for which critical Mach number is in region of high values characteristic of low-drag airfoils.

A theoretical investigation was conducted on jet-induced flow deviation. Analysis is given of flow inclination induced outside cold and hot jets and jet deflection caused by angle of attack. Applications to computation of effects of jet on longitudinal stability and trim are explained. Effect of jet temperature on flow inclination was found small when thrust coefficient is used as criterion for similitude. The average jet-induced downwash over tail plane was obtained geometrically.

Report presenting a method for calculating the lift, moment, and pressure drag of slender open-nose bodies of revolution at supersonic speeds. An application of the method to a typical ramjet fuselage is shown to give excellent agreement with available experimental data.

"A machined mixed-flow centrifugal impeller of a relatively complex passage shape was used as a pattern to cast a number of aluminum-alloy impellers from two aluminum-base alloys (designated alloys 1 and 2) by the 'lost wax' process. An investigation was conducted to determine whether these cast impellers, could be considered satisfactory for use in compressors. The investigation included preliminary examination, physical tests, metallurgical examination, and performance tests" (p. 1).

"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).

Report discussing tests to determine the effect of 2-percent additions of six aromatic amines on the knock-limited performance of 28-R fuel. All of the aromatic amine blends increased the performance and power of the base fuel. Different blends performed better at different fuel-air ratios.

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).

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.

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.

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 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.