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 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.

Report presenting tests made in the 4- by 6-foot vertical wind tunnel of an NACA 0009 airfoil with a 30-percent-chord flap with a medium amount of aerodynamic overhanging balance. In this investigation, the effects of the shape of the flap-nose overhang and the gap at the nose of the flap have been determined. The results indicate that, generally, the lift effectiveness of the aerodynamically balanced flap was increased slightly over that of a plain flap when a blunt or medium flap nose was used on the balanced flap.

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.

"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 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 a theoretical study of the effects of aileron adverse yawing moment on lateral maneuverability at a high lift coefficient. The study included the effects of changes in effective dihedral angle, vertical-tail area, and tail length.

Report presenting force-test measurements in two-dimensional flow in the 4- by 6-foot vertical tunnel to determine the characteristics of an NACA 0015 airfoil equipped with a straight-contour plain flap with a chord 30 percent of the airfoil chord. Results regarding the lift, hinge moment of flap, pitching moment, and drag are provided.

Report presenting tests of 10-foot diameter, single- and dual-rotating tractor propellers with two to eight blades conducted in the 20-foot propeller-research tunnel. The blades were 50 percent wider than those used in previous investigations. Results regarding the effect of dual rotation and effect of solidity are provided.

Report presenting a series of related flying-boat hull forms with various combinations of aerodynamic and hydrodynamic requirements that were tested in an NACA tank and high-speed tunnel. Effects explored included varying the height of the bow, varying the height of the stern, increasing the angle of dead rise at the bow, decreasing the angle of dead rise on the afterbody, increasing the depth of step, increasing the angle of afterbody keel, adding chine flare, adding a third planing surface, and rounded chines at the bow.

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 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 presents the results of tests of full-scale propellers made in the 20-foot propeller-research tunnel (PRT) at the Langley Memorial Aeronautical Laboratory. The power coefficients of all dual-rotating propellers in the report represent the sum of the power coefficients of the front and rear propellers and are for the test conditions in which blade angles of the front and rear propellers were set to absorb approximately equal power at peak efficiency only.

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 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.

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 vibration tests of six- and eight-blade tractor and seven- and eight-blade pusher dual-rotating propellers conducted in the 16-foot high-speed tunnel to determine the severity of vibrations excited by blade passages. Measurements of vibratory stresses were made for engine-speed ranges at low, intermediate, and high engine powers. Few vibrations caused by blade passages were detected, and those vibrations were not serious.

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."

From Introduction: "The lift increments of different flap arrangements were determined by the method of reference 1 with a simple chord correction factor being applied. This procedure is somewhat similar in basic principles to the method of reference 2. The accuracy of the present method was determined by calculating by means of this method the lift and moment increments of flaps on 10 different finite wing-flap combinations for which wind-tunnel data were available."

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.

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 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 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 presenting a flight investigation made on a wing section of a P-47D airplane to determine the effect of roughness on wing profile drag with transition fixed far forward. Surveys of the wake were made for two surface conditions with transition fixed by a thread at 5 percent chord back of the leading edge on the upper and lower surfaces. Below the Mach number at which shock occurred, variations in Mach number of as much as 0.16 appeared to have no appreciable effect on the section profile-drag coefficients of either the smooth or roughened surfaces with transition fixed.