Report discussing an investigation of cooling ducts at various positions on a model of a typical pursuit airplane in the NACA full-scale tunnel. Results in the report are given for a duct located on the bottom of the fuselage with the inlet behind the leading edge of the wing. Due to the thick boundary layers at the inlets of the rear underslung fuselage duct and the serious pressure losses that resulted, a special vane was also installed to avoid boundary-layer separation.

Report presenting a series of calculations made to determine the probable dynamic wing stress of two large airplanes in atmospheric gusts. The results indicate that in both isolated and repeated gusts of probable occurrence, the dynamic overstress is about 10 percent when referred to the present static design standard.

"Three widely different nose shapes were tested on a fuselage alone and on a complete model in the UACA stability tunnel to investigate the effect of cowling shape on stability characteristics. The results are presented in the form of charts which show the variation in the aerodynamic characteristics with the three nose shapes for the propeller-removed condition over a wide range of angles of attack and yaw. The results of the investigation indicated that large changes in the cowling shape produced relatively small changes in the aerodynamic characteristics" (p. 1).

Report presenting calculations of numerical values of the jet-boundary corrections to the angle of attack and the induced-drag, rolling-moment, and yawing-moment coefficients for complete airplane or wing models in 7- by 10-foot closed rectangular wind tunnels. The results showed that the wing area was the most important variable, as has usually been assumed in previous calculations. When the corrections were based on wing area, the effect of most of the other variables was negligible.

Report presenting ground-effect tests made in the LMAL 7- by 10-foot tunnel of a model of a low-wing, pursuit-type airplane equipped with a full-span 25-percent-chord slotted flap. Testing occurred at different heights and power conditions, and two stabilizer and elevator settings were used at each condition. Results indicated that the elevator deflection required for landing in a three-point attitude with the full-span slotted flap was considerably greater than that required with a partial-span split flap.

Report presenting the results of an investigation to determine the impact properties of flush-riveted joints manufactured by different riveting methods. Testing occurred on a pendulum impact machine at temperatures of 70, -50, and -70 degrees Fahrenheit using rivets made of aluminum alloy A17S-T and plates of aluminum alloy 24S-T.

Report presenting testing of models of three flying-boat hulls with a length-beam ratio of 10.5. Testing occurred at two depths of step and two angles of dead rise. Results regarding resistance, trimming-moment, and wetted-length data for general fixed-trim and free-to-trim tests at load coefficients up to 4.0 are provided.

Report discusses the results of analyses and test results of the porpoising characteristics of flying boats. Equations for calculating stability limits with given hull forms under various combinations of loading and aerodynamic conditions and for modifications of the afterbody are provided.

Report presenting an investigation of a thermal ice-prevention system for a Curtiss-Wright C-46 airplane, which included a determination of the change in stress at various locations in the wing outer panel caused by operation of the thermal system. Curves are presented showing the chordwise variation of stress and temperature for two wing stations.

Report presenting an investigation that was conducted to determine the effect of carburetor dry-air temperature on the cooling characteristics of a typical full-scale air-cooled engine cylinder mounted on a single-cylinder crankcase.

"The variation of intercooling requirements with altitude is discussed and the corresponding effects on intercooler design are shown. A discussion is also given of the relations among the various design parameters and of the ranges of choice in design. The important effects of the various factors on intercooler proportions are illustrated with charts for the Harrison copper cross-flow intercooler" (p. 1).

Report presenting a discussion of the variations with altitude of the air-volume requirements of the carburetor and various cooling elements, and the effects of the variations on duct design for high-altitude airplanes.

Report discusses the results of tests on single-cylinder engines to determine the worth of several changes in exhaust-valve and port design to extend the useful life of the valves used in air-cooled engines. Changes explored included the valve-head diameter, the valve-stem diameter, the valve coolant-flow area, the valve-head material, and the size of the exhaust-valve guide boss. In the normal range of temperatures encountered in engine operation, valve material was found to be the most important factor.

Report presenting the theory, design, and effect on cooling of the constant-velocity axial-flow fan as related to the problem of high-altitude aircraft engine cooling. The existing theory of the axial-flow fan, including a discussion of the fan losses, is summarized.

Report presenting an investigation of the knock-limited performance of leaded blends of 12 pure aromatic hydrocarbons in a full-scale aircraft-engine cylinder at CRC simulated cruise and take-off conditions to determine the antiknock effectiveness of additions of pure compounds to aviation fuels. Results indicated that all of the hydrocarbons increased the knock limit of the base fuel except for 2 of them.

Report presenting evidence in support of the propriety of substituting a general porpoising test of flying boat hull models in place of the usual specific test. The results of a general test are presented and compared with the results of a specific test of the same model.

Report discusses an investigation into the mechanical stability of a rotor with two vertically hinged blades mounted on symmetrical supports of equal stiffness and mass. Information about the instability regions and effect of damping is included. The two-blade rotor was found to have two shaft-critical speeds at which instability can occur as well as a second region at which self-excited vibrations occur.

Finite trigonometric series is fitted by harmonic analysis as an approximation function to the psi function of the Theodorsen arbitrary-airfoil potential theory. By harmonic synthesis, the corresponding conjugate trigonometric series is used as an approximation to the epsilon function. A set of coefficients of particularly simple form is obtained algebraically for direct calculation of the epsilon values from the corresponding set of psi values.

Report presenting a method for calculating the temperature of a surface wetted either by a pure liquid, such as water, or by a mixture, such as alcohol and water. The method is applied to the problem of protecting, by alcohol, propellers and the induction system of the engine against ice. The psychrometric equation, used in wet-bulb hygrometry, is deduced in its general form.

Report presenting a preliminary way to give a logical and consistent analysis of the problem of providing adequate protection to the personnel, contents, and structure of nonmetallic aircraft against the effects of electric shock, mechanical damage, and fire which are almost certain to occur if an unprotected aircraft is struck by lightning. The analysis should bring out clearly the questions on which further experimental work is needed and the assumptions that must be present to bridge the gaps regarding the phenomena associated with lightning.

Report presenting an investigation to determine the effect of fuel volatility on engine power and economy as influenced by mixture distribution. Tests of four fuels of different volatility were conducted on a Wright R-2600-8 engine at desired cruising power, maximum cruising power, normal rated power, and takeoff power.

Report discusses the variation of surface-ignition temperature with charge density, fuel-air ratio, and surface-ignition advance. Tests on several fuels were conducted on a supercharged CFR engine to determine surface-ignition temperature as a function of the three variables. It was concluded that surface-ignition temperature is not a satisfactory criterion for differentiating between preignition characteristics of different fuels.

Report presenting the section critical speeds and profile drags of the shank and hub sections of a propeller used on a current liquid-cooled-engine pursuit type of airplane. Results indicated that serious adverse compressibility effects can be expected at speeds of about 400 miles per hour. Suitable fairings for shank and hub sections were found to be necessary for maximum propulsive efficiency.

Report presenting an analysis of experimental and theoretical data, which indicates that critical evaluation of fuel performance, especially economy, must be made in the engine. Data show that heating value is, from the aspect of fuel economy, not so important an aviation-fuel specification as believed. The knock ratings of fuels are affected by spark advance.