The development of the laminar boundary layer in a compressible fluid is considered. Formulas are given for determining the boundary-layer thickness and the ratio of the boundary-layer Reynolds number to the body Reynolds number for airfoils and bodies of revolution. It is shown that the effect of compressibility will profoundly alter the Reynolds number corresponding to the upper limit of the range of the low-drag coefficients.

Report presenting an investigation of the effects on stability and control of a pusher propeller behind conventional horizontal and vertical tail surfaces in the free-flight tunnel by tests of a scale model of a submerged-engine pusher airplane. The investigation consisted of flight and balance tests at windmilling and high-power conditions with a partial-span Zap extensible flap extended and retracted. Results regarding the longitudinal stability, longitudinal control, stalling characteristics, lateral stability, and lateral control are provided.

Report presenting an investigation in the 7- by 10-foot tunnel of various modifications of the trailing-edge portion of a 0.20-chord plain aileron on a partial-span model of a tapered low-drag wing. The modifications tested included various amounts of symmetrical and unsymmetrical thickening and beveling of the aileron trailing edge. Results regarding coefficients and corrections, characteristics with ailerons neutral, characteristics with ailerons deflected, aileron trim characteristics, and estimated aileron-control characteristics are provided.

Report presenting a thermal ice-prevention system for the B-24D airplane. The report includes a description of the design and an outline of the method of design analysis. Results of performance tests of the installation will be presented in a supplementary report.

Report presenting a method utilizing the Doppler effect on radio signals for determining the speed and distance traveled of an airplane. The method is called the NACA radio ground-speed system and uses the standard radio transmitter already found in most aircraft. Flight tests were made in which the method was used and the results were consisted with calibrated airspeed indications and stop-watch measurements.

"A method that utilizes the Doppler effect on radio signals for determining the speed of an airplane and the distance traveled by the airplane has been developed and found to operate satisfactorily. In this method, called the NACA radio ground-speed system, standard readily available radio equipment is used almost exclusively and extreme frequency stability of the transmitters is not necessary. No complicated equipment need be carried in the airplane, as the standard radio transmitter is usually adequate" (p. 1).

"Preliminary data are presented on the variation of the maximum lift coefficient with Mach number. The data were obtained from tests in the 8-foot high-speed tunnel of three NACA 16-series airfoils of 1-foot chord. Measurements consisted primarily of pressure-distribution measurements in order to illustrate the nature of the phenomena. It was found that the maximum lift coefficient of airfoils is markedly affected by compressibility even at Mach numbers as low as 0.2" (p. 1).

Report presenting an analysis of the pressure drop that is required to cool a typically baffled radial engine, which shows that a total pressure drop of 58 pounds per square foot is necessary at sea level and 112 pounds per square foot is required at an altitude of 40,000 feet.

From Summary: "Surveys of the air flow in the region of the tail surfaces of a single-engine pursuit-type airplane equipped with dual-rotating propellers are presented."

An investigation has been made to determine the motions of and the flight paths describe by a Navy dive-bombing airplane in simulated diving attacks. The data necessary to evaluate these items, with the exception of the atmospheric wind data, were obtained from automatic recording instruments installed entirely within the airplane. The atmospheric wind data were obtained from the ground by the balloon-theodolite method. The results of typical dives at various dive angles are presented in the form of time histories of the motion of the airplane as well as flight paths calculated with respect to still air and with respect to the ground.

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.

Report presenting compressibility phenomena under flight conditions on the XF2A-2 airplane, which was subjected to a series of dives and pull-outs at speeds up to 550 miles per hour corresponding to Mach numbers of 0.74. Results regarding time histories, pressure data, drag coefficient, and elevator control force are provided.

Report presenting data constituting a summary of the physical properties of 120 samples of metal alloys, representing 86 different compositions which have been investigated for their suitability as turbosupercharger wheel materials. Some of the reported data include the chemical composition, fabrication procedure, tensile-test and hardness values at room temperature, and tensile and rupture-test characteristics at 1200 degrees Fahrenheit.

Report presenting flight tests of an all-movable vertical tail of reduced area of the Fairchild XR2K-1 airplane. Results are in agreement with previously obtained data on a larger all-movable tail. Results regarding rudder effectiveness, directional stability, rudder-free lateral motion, rudder hinge moments, and areas of future research are provided.

"Hinge-moment, lift, and pressure-distribution measurements were made in the two-dimensional test section of the NACA stability tunnel on a blunt-nose balance-type aileron on an NACA 66,2-216 airfoil at speeds up to 360 miles per hour corresponding to a Mach number of 0.475. The tests were made primarily to determine the effect of speed on the action of this type of aileron. The balance-nose radii of the aileron were varied from 0 to 0.02 of the airfoil chord and the gap width was varied from 0.0005 to 0.0107 of the airfoil chord. Tests were also made with the gap sealed" (p. 1).

Report presenting hinge-moment, lift, pressure difference across the balance, and pressure-distribution measurements in the two-dimensional test section of the stability tunnel on a 0.60 aileron-chord sealed internal-balance aileron on a specified NACA airfoil. The primary test objective was to determine the effect of speed on the action of the aileron.

Report presenting an analysis of data for turbulent boundary layers along wings and bodies of various shapes in order to determine the fundamental variables that control the development of turbulent boundary layers. Results indicate that the type of velocity distribution in the boundary layer could be expressed in terms of a single parameter.

Report presenting flight tests of a three-blade thin Clark Y propeller operating at a fixed blade angle of approximately 46.8 degrees at 0.75 radius, at an advance-diameter ratio of 2.37, and at true airplane speeds of approximately 300 and 450 miles per hour. Comparisons of the results at the two different speeds indicated losses in propeller efficiency from 11 to 18 percent at high speed. Report is incomplete.

Report presenting a description of a device for indicating stream Mach number in a high-speed tunnel. It consists of a mechanism for determining the pressure ratio that Mach number is a function of. The instrument is in service in the 8-foot high-speed tunnel and its accuracy has been found adequate for wind-tunnel requirements.

Report presenting force tests in two-dimensional flow made on an NACA 66-009 airfoil with a flap having a chord 30 percent of the airfoil chord and a tab having a chord 20 percent of the flap chord. A plain flap and flaps having overhangs of 35 and 50 percent of the flap chord were tested with two gap variations: sealed and unsealed. Results regarding lift, flap hinge moments, pitching moments, drag, and tab characteristics are provided.

Report presenting tests made on an NACA 23012 airfoil fitted with a 20-percent-chord, true-contour aileron with 35-percent-chord, extreme blunt-nose balance. The primary purpose of the investigation was to determine the variation of the aerodynamic characteristics of this type of aileron with airspeed; the effect of variations of gap width and balance-nose radii was also investigated. Results regarding hinge moments, lift, and pitching-moment coefficients are provided.

Report presenting results of flight tests to determine the turning performance of a Navy F2A-3 airplane over a range of speeds for three flap deflections at two altitudes. The results are correlated with an analytical study of turning performance in which the effect of thrust on maximum lift coefficient was considered.

"The effect of variations in the type of mean line on the section characteristics of several representative NACA low-drag airfoils was investigated. The test results are compared with theoretical predictions and indicate trends that facilitate the choice of mean line in the absence of tests" (p. 1).

"The effect of two-dimensional bumps and surface waviness on the pressure distribution over airfoils is considered. It is shown that the results of the analysis may be useful in evaluating the effects of accidental or intended surface distortions on the drag and critical Mach number of airfoils" (p. 1).