Report presenting an investigation in the 19-foot pressure tunnel to determine the nacelle drag, the cowling-air flow, and the propeller characteristics of a model of a high-performance military airplane. The model is fitted with NACA D(sub S)-type engine cowlings and with propellers embodying NACA 16-series airfoil sections. Results regarding the propeller characteristics, drag and cowling-air flow with the propeller removed, the effect of propeller on flow through cowling, and the influence of cooling requirements on airplane performance are provided.

From Introduction: "The purpose of this analysis was to investigate the use of function of intake-manifold temperature and pressure, exhaust back pressure, and engine speed in place of a ventri as a means of measuring engine air consumption and to determine if this function is suitable for automatic mixture control."

Report presenting a convenient technical method to evaluate changes in the airfoil characteristics resulting from an extension of the chord at the trailing edge of a propeller blade section. The method determines the change in the angle of zero lift, the ideal angle of attack, and the difference in these angles as a function of the angle and length of the trailing-edge extension.

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 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 two low-drag airfoils, the NACA 747A315 and the NACA 747A415, which are designed to have reduced pitching moments about the quarter-chord point and moderately high values of the design lift coefficient and are tested in the tow-dimensional low-turbulence pressure tunnel.

Report presenting a method for predicting from basic airplane characteristics the elevator deflection required to maintain optimum landing attitude. Charts for evaluating the components of the equation for elevator deflection and a comparison of computed and measured values for 15 airplanes are included. The computed deflection is considered the minimum value required to maintain landing attitude due to variations in piloting technique.

Report describing the behavior of the heat meter when it is used in thermal circuits which are under the influence of transient potentials. Three scenarios are considered: a heat meter suddenly placed on a hot surface, a heat meter mounted on the interior surface of the cabin wall of an uninsulated airplane climbing through air of decreasing temperature, and a heat meter mounted on the interior surface of the composite cabin wall of an airplane climbing through air of decreasing temperature.

Report presenting the effect of Reynolds number on the aerodynamic characteristics of a low-drag airfoil section tested under conditions of relatively high stream turbulence. The data are presented as curves of section angle of attack, section profile-drag coefficient, and section pitching-moment coefficient against section lift coefficient for various flap deflections.

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 some principles for designing the optimum hull for a large long-range flying boat in order to suit the requirements of minimum drag, seaworthiness, and ability to take off and land at all operational gross weights. The principles include the use of moderate gross-load coefficients, ample forebody lengths, and deep steps and the close adherence of the form to that of a streamline body of revolution with a moderate fineness ratio.

"A technical method is given for calculating the axial interference velocity of a propeller. The method involves the use of certain weight functions P, Q, and F. Numerical values for the weight functions are given for two-blade, three-blade, and six-blade propellers" (p. 53).

Report presenting a description of a short method of estimating propeller efficiency for a given operating condition. The efficiency is determined for any design condition by evaluating separately from charts the induced losses and the profile-drag losses. The report covers single-rotating propellers of two, three, four, six, and eight blades and includes charts showing the rotational-energy loss for the given operating condition.

Report presenting a study to determine the effect of several methods of increasing the knock-limited power on critical cylinder temperatures. The knock-limited indicated horsepower and cylinder temperatures were determined for a Wright R-2600-8 cylinder under specified operating conditions. The most satisfactory method of increasing knock limited power was found to be internal cooling with water and the least satisfacotry was increasing the engine speed.

Report discusses the results of an investigation into the effectiveness of water injection into the combustion end zone of a spark-ignition engine cylinder for the suppression of knock. The injection angle was found to be very important for obtaining maximum results. The results of various angles and amounts of water were examined.

Report presenting simple curves by which the basic pressure-drop characteristics of unheated tubular radiators can be corrected to operating conditions in which the radiator is heated and in which the Mach number of the tube flow is of appreciable magnitude. The only data required for the use of the curves are the radiator dimensions, the rate of heat input, the pressure and temperature ahead of the radiator, and the rate of mass flow of air through the radiator.

Report details the methods of determining the heat-transfer rate, pressure drop, and drag power of high-altitude radiators. Performance charts are provided for a wide range of design variables.

Report presenting a paper in a series about the cooling of aircraft-engine installations with special reference to the difficulties of cooling at high altitudes. This particular paper discusses the properties of NACA standard air and Army summer air, with corresponding stagnation conditions for a range of flight speed, as summarized in tables and figures.

Report presenting the heat-transfer theory for air-cooled engines and an analysis of the cooling pressure drop for the case in which the pressure drop is an appreciable fraction of the absolute pressure. A chart is given for the simple determination of the cooling pressure drop predicted on the basis of the usual type of sea-level cooling-correlation tests.

Report presenting a detailed analysis to take account of the high cooling-air velocity occurring in high-altitude radiators. Methods are developed for determining the heat-transfer rate, the pressure drop, and the drag power. Radiator performance charts based on the analysis are presented for a wide range of the design variables.

Report presenting the fatigue data obtained at the Aluminum Research Laboratories from tests of various types of 17S-T and 53S-T specimens. The specimens were large enough to represent actual service conditions, but the repetition of loading was more rapid than would occur in ordinary service.

Report discusses a method of replica creation and testing of the surface-finish variation of aircraft engine parts subject to wear. In this report, a positive replica is created, the surface is treated, the replica is tested to make sure the fidelity is high enough, and a series of ring-sticking tests are conducted on the replicas. A summary of the results of the testing is also included.

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.

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.