Report presenting 10 practical-construction models of sections of helicopter rotor blades tested in the NACA two-dimensional low-turbulence pressure tunnel at atmospheric pressure. Lift, drag, and pitching-moment characteristics of blades representing the present method of construction of the YR-4A helicopter were determined.

Report presenting results of compression tests of six paper-base plastic panels with outward-acting normal pressure. All panels failed by separation of the skin, either from the rib or from the stiffeners. Results regarding the introduction of air pressure and types of failures encountered are provided.

Report presenting an investigation conducted to determine the effect of water injection on the knock-limited performance of a V-type 12-cylinder liquid-cooled engine. The knock-limited performance tests were made at an engine speed of 3000 rpm with carburetor-air temperatures of 158, 101, and 50 degrees Fahrenheit at water-fuel ratios of 0, 0.2, 0.4, and 0.6.

From Summary: "Tests on the B-34 fin-rudder-tab assembly were performed in the NACA 8-foot high-speed tunnel. Two cases of tab flutter were studied. It was shown conclusively that the frequency of the original or heavy tab was too low and caused coupling with one of the lower bending frequencies. A general conclusion was made that the tab frequency should be considerably higher than the lower modes of the fin-rudder assembly because there is generally a weaker coupling between the tab and the higher mode responses."

Report presenting wind-tunnel tests of a 0.175-scale model of a midwing airplane in order to determine the high-speed longitudinal characteristics, to test devices for improving longitudinal control at high Mach numbers, and to determine the aileron effectiveness at high Mach numbers. Force and moment coefficients are computed from test data. Control forces, elevator angle, and aileron angle for several flight conditions are predicted.

Flight tests were conducted on the OS2U-2 seaplane with simple circular-arc-type ailerons directly connected to the actuating torque tube. Two aileron test installations were made, differing only in the inclination of the projecting surface with the wing's upper surface. The lateral-control characteristics of the airplane were determined from data obtained in stalls and rudder-fixed aileron rolls. The revised ailerons were deficient in maximum rolling effectiveness, but were capable of controlling the rolling tendencies of the airplane near the stall.

Report presenting a study of the effect of aftercooling on the brake horsepower, weight, and weight-power ratio of a power plant consisting of a 2000-horsepower air-cooled engine, an intercooler, and two stages of supercharging. Three cases are considered: inadequate supercharging, supercharging to constant manifold pressure, and supercharging to detonation-limited manifold pressure.

Report presenting testing in the 19-foot pressure tunnel of a scale semispan model of the XTB2D-1 airplane wing and fuselage combination. The purpose of the investigation was to determine the optimum position of the double-slotted flap, the characteristics of the full-span flaps at various deflections in their fully extended position, the effectiveness of deflecting the full-span flaps to small positive angles as a camber changing feature, the stalling characteristics of the wing, and the effectiveness of the flap as a brake when deflected to negative angles.

Report presenting testing of a scale semispan model of the Douglas XTB2D-1 airplane wing and fuselage combination equipped with full-span double-slotted flaps conducted in the 19-foot pressure tunnel. This paper describes the development of the outboard flap, or roll flap, including the determination of optimum relative position of various parts of the airplane, determination of the roll-flap loads and hinge moments for design information, and an estimation of the lateral-control forces of the airplane. The results indicate that adequate rolling effectiveness and high maximum lift coefficient may be obtained with the use of full-span double-slotted flaps.