Report discusses the results of testing on the pressure distribution at several longitudinal sections of the vertical tail surface of the Curtiss P-40K airplane at various angles of attack and angles of yaw and with the propeller removed and propeller operating. Results regarding the chordwise pressure distributions, effects of propeller operation on the spanwise distribution of normal-force coefficient, total normal-force coefficients, and effect of propeller operation on the variation of vertical-tail normal-force coefficients are presented.

Report presenting flight tests of an all-movable horizontal tail installed on a Curtiss XP-42 airplane due to its possible advantages as a longitudinal control at high Mach numbers. The elevator control was found to be unsatisfactory with the control arrangements tested.

Report presenting wind tunnel testing to investigate the possibility of reducing the hinge moments of a control surface by beveling the trailing edge. Tests were made with a 9-percent-thick airfoil with a 30-percent-chord plain flap. Results regarding the variations of lift and hinge moment, effect of shapes, and pitching moments are provided.

Report presenting tests made in the variable-density wind tunnel of airfoils of the NACA 4400 series modified by reflex at the trailing edge designed to reduce the pitching moment to the value of -0.03. The modified airfoils are designated the NACA 4400R series.

Report discussing testing on an F6F-3 with a spring-tab rudder to determine the directional stability and control characteristics. Using the spring-tab rudder was found to result in lower trim-force change with speed and lower pedal forces in sideslips than the original rudder. Pilots were found to prefer the maneuverability of this configuration.

Report presenting lift and elevator hinge-moment characteristics of a horizontal tail with various plain and balanced elevators and mounted on a typical pursuit fuselage as measured in the 7- by 10-foot wind tunnel at attitudes simulating normal-flight and spin conditions. The lift effectiveness of the elevator was practically independent of the size of the aerodynamic balance. Results regarding the fuselage alone and fuselage interference, lift characteristics of fuselage-tail combinations, lift effectiveness of the tab, elevator hinge moments, parameters, effect of yaw on elevator hinge moments, effect of tab on elevator hinge moments, drag, and comparison with two-dimensional data are provided.

Report presenting a method of graphical analysis that allows for the prediction of the thermal and aerodynamic performance of a ram-operated heater and duct system, for cabin heating or wing de-icing, at any altitude and airplane speed. Performance can be predicted from the isothermal total pressure drop across the components of the duct system at several ventilating air rates and the thermal output of the heater at various air and exhaust gas rates.

Report presenting aerodynamic testing of scale models of the Edo seaplane floats for the SB2U-3, OS2U-2, and XSB2C-2 seaplanes. Various coefficients, pitching moment, yawing moment, and drag coefficients are provided.

Report presenting performance data on a small exhaust gas and air heat exchanger. The heat transfer rates were measured using about 8000 pounds per hour of exhaust gas and 4300 pounds per hour of ventilating air. The thermal performance of heater no. 2 can be estimated to 3 to 17 percent by use of the method described in the report.

Report presenting a simplified approximate method of calculating the unit thermal conductance along an airfoil as a function of distance from the leading edge, by use of heat transfer data for smooth cylinders and smooth flat plates. Several examples are used in order to show the effectiveness of the method.

Report discusses the results of an investigation of an NACA 0009 airfoil with a 40-percent-chord flap with medium and large aerodynamic balances of elliptical and blunt nose shapes and a plain overhang. The results are presented as aerodynamic section characteristics for several flap deflections with the gap at the flap nose sealed and unsealed.

Results of subject tests indicate the difficulty of obtaining closely balanced rudder surfaces for most tail assemblies with shielded horns and maintaining a near zero rate-of-change of hinge-moment coefficient without an additional balancing device. A comparison is made between shielded and unshielded horn test results. Pressure distribution and tuft tests of flow over different shaped horns showed higher critical speed for medium-taper nosed horn. The trim tab nose shape had little effect on tab test results.

Report presenting an investigation in the 7- by 10-foot tunnel of three inset tabs and of one attached tab on the beveled aileron of a low-drag wing. The results indicated that, of the arrangements tested, an inset tab with a chord 50 percent of the aileron chord provided the most satisfactory trimming characteristics on a beveled aileron.

"Strength tests and strain measurements were made of 19 long shear panels with rectangular inspection cut-outs; that is, cut-outs obtained by removing the sheet between two adjacent stringers without cutting any stringer. The test results indicated that the stress concentration existing at low stresses tends to disappear at very high stresses and that the assumption of uniform stress distribution leads to a satisfactory correlation of the test results. Stiffening of the sheet bay containing the cut-out was found to have practically no effect on the panel strength" (p. 1).

From Introduction: "In the present paper a numerical procedure for the stress analysis of flat-sheet and stringer combinations of arbitrary construction and loading is presented and applied to axially loaded panels and to the reinforced covers of box beams."

Report presenting a method for calculating the stick-fixed neutral point of an airplane with the propeller windmilling, the flaps neutral, and landing gear retracted. The methods used in this report should be useful in estimating the stick-fixed neutral points of new designs for all flight conditions.

Report presenting a study to determine what loadings and proportions have been chosen by designers of seaplanes and flying boats and what, if any, interrelations exist between the loadings and proportions. The characteristics considered include the beam, getaway speed, forebody length, afterbody length, hull length, center of gravity, and brake horsepower necessary.

Report discusses the results of an investigation into the tightness, shear strength, tensile strength, and life under pulsating loads of hollow, hydraulically expanded rivets made of 17S-T aluminum alloy. The countersunk-head rivets with inserts had a much higher maximum load in shear than the modified-roundhead rivets, which did not have inserts.

Report presenting an investigation to determine any injurious effects of knock on engine parts. Endurance tests were run on a single-cylinder engine to compare the conditions of cylinders operated with and without knock. Results regarding the history of the tests, conditions of pistons and cylinders, absence of surface ignition, and effect of knock on cylinder temperatures are provided.

"Tests of a 1/3-scale model of an NACA E-type cowling were made in the 8-foot high-speed tunnel for the purpose of determining the effect of the gap between the skirt of the hollow spinner and the cowling proper on the pressures available for cooling. It was found that even a large gap (0.096 in. on the model) had no appreciable effect on the available cooling pressures" (p. 1).

Report discusses an investigation into the tensile strength of cast-iron piston rings, NACA microtensile specimens, and bar specimens. Photographs showing the relation between graphite-flake size and tensile strength and radiographs showing the shrinkage cavities in the piston rings are provided. Piston rings tend to be one of the first parts of an aircraft engine to fail, so discovering the ideal material composition and foundry treatment is very important.

Report discussing testing to determine the cooling effect of modified baffles and auxiliary-cooling ducts on the rear-row cylinders of a double-row radial engine. The modified baffles were found to reduce the temperatures of the exhaust-valve seats, but did not have an effect on the valve-guide temperatures. The auxiliary-cooling ducts reduced temperatures of the exhaust-valve seats and rear spark plug gaskets.

Report presenting an examination of new and used nitrided-steel piston rings by electron and X-ray diffraction in a study of the surface changes produced during engine operation. Both new and used rings, examined after degreasing, gave an electron-diffraction pattern consisting of diffuse bands: those from used rings fell at the usual positions of the bands from polished metal surfaces.

Report discussing the effects of supercharging on the take-off thrust and useful load for a typical helicopter. Performance of the engine with the supercharger and on the rotor thrust is detailed.