Report presenting an investigation in the two-dimensional low-turbulence tunnels for the purpose of developing an optimum flap configuration for maximum lift on an airfoil section for the Republic XF-12 airplane equipped with a double slotted flap. Lift and flap loads were obtained at several flap deflections for two flap paths. Results regarding lift, drag, and flap loads are provided.

Report discussing a motion picture of the development of knock in a spark-ignition engine, which consists of 20 photographs taken at intervals of 5 microseconds, or at a rate of 200,000 photographs per second, with an equivalent wide-open exposure time of 6.4 microseconds for each photograph.

From Introduction: "The purpose of this report is to gather together in one place information on the skipping characteristics of number of flying boats. A graph showing the influence of the hull form on the skipping characteristics is given which should be useful in laying out the proportions of the hull in preliminary design to insure good landing behavior."

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, summaries of the committee's activities and research accomplished, bibliographies, and financial report.

Report presenting tests of two wings, one stubbed and one regular-sized, in the propeller-research tunnel to determine the increase in lift obtainable by boundary-layer control and to determine the power required for the blower. Lift coefficients of about 3.2 were obtainable for both wings, but the pressure method required several times more power than the suction method.

"Because the tensile strength and tensile yield strength of alloy 75S-T are appreciably higher than those of the materials used in the tests leading to the use of the straight-line column curve, it appeared advisable to establish the curve of column strength by test rather than by extrapolation of relations determined empirically in the earlier tests. The object of this investigation was to determine the curve of column strength for extruded aluminum alloy 75S-T. In addition to three extruded shapes, a rolled-and-drawn round rod was included" (p. 1).

Measurements of the longitudinal stability and control of a pursuit-type airplane were made in flight up to a Mach number of 0.78. The data are presented in the form of curves showing the variation, with center-of-gravity position, dynamic pressure, and Mach number, of the stick-fixed and stick-free stability, control, and balance of the airplane.

"A relatively simple equation has been found to express with fair accuracy, variation in manifold-charge temperature with charge in engine operating conditions. This equation and associated curves have been checked by multi cylinder-engine data, both test stand and flight, over a wide range of operating conditions. Average mixture temperatures, predicted by the equations of this report, agree reasonably well with results within the same range of carburetor-air temperatures from laboratories and test stands other than the NACA" (p. 1).

Behaviors of both model and full-scale airplanes were ascertained by making visual observations, by recording time histories of decelerations, and by taking motion picture records of ditchings. Results are presented in form of sequence photographs and time-history curves for attitudes, vertical and horizontal displacements, and longitudinal decelerations. Time-history curves for attitudes and horizontal and vertical displacements for model and full-scale tests were in agreement; maximum longitudinal decelerations for both ditchings did not occur at same part of run; full-scale maximum deceleration was 50 percent greater.

Report of a study to develop a method of obtaining gas temperatures from the frequency of knock-induced gas vibrations in an internal-combustion engine cylinder. Temperatures calculated from frequency data were in agreement with temperatures measured by the spectral line-reversal method in previous investigations and were about 700 degrees Fahrenheit lower than temperatures obtained from thermodynamic charts.

"A spoiler-type lateral-control system has been developed for use on the Northrop P-61 airplane. The lateral-control system is to be used with large-span flaps and consists of a thin circular arc spoiler, linked with a short-span plain aileron located just outboard of the spoiler. This unconventional lateral-control system has been accepted with enthusiasm by the pilots who have flown the airplane" (p. 1).

Report presenting testing to determine the best way to land the SB2C-1 airplane in calm and rough water and to determine its probable ditching performance. The behavior of the model was determined by making visual observations and by recording the maximum longitudinal decelerations and by taking motion pictures of the ditchings. Results regarding the effect of flaps, attitude, weight, a wing-low landing, effect of simulated damage, effect of tail wheel, ditching aids, and seaway are provided.

"An investigation has been conducted in the Langley rectangular high-speed tunnel to determine the effect of compressibility on the pressure distribution for a modified NACA 65,3-019 airfoil having a 0.20-chord flap. The investigation was made for an angle-of-attack range extending from -2 to 12 deg at .20 flap deflections from 0 to -12 deg. Test data were obtained for Mach numbers from 0.28 to approximately 0.74" (p. 1).

"The results of a theoretical and experimental investigation of wall interference for an airfoil spanning a closed-throat circular wind tunnel are presented. Analytical equations are derived which relate the characteristics of an airfoil in the tunnel at subsonic speeds with the characteristics in free air. The analysis takes into consideration the effect of fluid compressibility and is based upon the assumption that the chord of the airfoil is small as compared with the diameter of the tunnel" (p. 225).

Tables I and II of this report summarize the gust and draft velocity data for thunderstorm flights 25 and 26 of August 21, 1946 and August 22, 1946, respectively. These dta were evaluated from records of NACA instruments installed in P-61C airplanes and are of the type presented in reference 1 for previous flights. Table III summarizes the readings of a milliammeter which was used in conjunction with other equipment to indicate ambient air temperature during thunderstorm surveys. These data were read from motion-picture records of the instrument and include all cases in which variations in the instrument indications were noted during the present flights.

Experiments have been conducted to determine the conditions that cause surging in compressors and to determine the effect of various installations and operating conditions on the character of the velocity and pressure variations occurring during surging. These investigations were made on three compressor units and the variation of static, total, and velocity pressure with time was recorded. In addition to the experimental studies, a simplified analysis was made to determine how instability of flow may occur in a compressor. Based on this analysis, an examination was made of several possible methods of inhibiting the occurrence of surging.

Report presenting the effects of negative dihedral on lateral stability and control characteristics at high lift coefficients determined by flight tests with a model. As the effective dihedral was decreased, the model became increasingly difficult to fly. Results regarding the effect of directional stability and lift coefficient on flight behavior are also provided.

"A flight test was conducted at the Flight Test Station of the Pilotless Aircraft Research Division at Wallops Island, Va., to determine the longitudinal control and stability characteristics of a 0.5-scale model of the Fairchild Lerk Pilotless aircraft with the horizontal wing flaps deflected 15 degrees. The data were obtained by the use of a telemeter and also by radar tracking. The results show an increase of effectiveness of the longitudinal control in producing normal accelerations up to a Mach number of 0.75 where this effectiveness gradually decreased becoming negative at a Mach number of 0.89" (p. 1).

Report discussing testing on the spin and recovery characteristics, longitudinal-trimming characteristics at extreme angles of attack, and tumbling characteristics of a model of the Cornelius XFG-1 glider. The effects of loading, mass distribution, and center-of-gravity position were determined. They also explored the inverted spin characteristics and spin-recovery parachute requirements.

Report discussing an investigation of the cooling characteristics of an R-2600-22 engine installed in a PBM-3D nacelle. The investigation explored the general cooling characteristics by the NACA cooling-correlation method and an investigation of specific points on the engine cylinder where cooling was critical, including the exhaust-valve-crown and number 3 cylinder.

Several previously published reports on a comprehensive investigation of a thermal ice-prevention system for a typical twin-engine transport airplane are correlated with some unpublished data to present the entire investigation in one publication. Several previously published reports on a comprehensive investigation of a thermal ice-prevention system for a typical twin-engine transport airplane are correlated with some unpublished data to present the entire investigation in one publication. The thermal system investigated was based upon the transfer of heat from the engine exhaust gas to air, which is then caused to flow along the inner surface of any portion of the airplane for which protection is desired.

Report discussing an investigation into cowl-flap and cowl-outlet designs for the B-29 in order to determine the effects of cowling performance of different types of flaps and elements of flaps. Details of the available pressure drop and cooling-air pressure-drop distribution are also provided.

Report investigating five cowl-inlet configurations for the B-29 to obtain design information for improving the cowl performance. The effects of propeller spinners and increased inlet diameters on the cooling-air pressures at the cowl inlet and face of the engine and on the drag and critical speed of the cowl are described.

"In order to eliminate the formation of ice on the carburetor throttle plates of an aircraft-engine induction system, two modifications of the throttle design and a variation in the method of throttle operation of the twin-barrel injection carburetor were tested" (p. 1). The modifications were investigated under severe icing conditions at normal power, maximum cruising power, and 60-percent normal power. The only modification that appeared to provide deicing assistance were the electrically heated throttle plates.