Bulletin presenting an investigation of the effects of various camouflage paints and painting procedures on the drag characteristics of a 60-inch-chord low-drag airfoil in the NACA two-dimensional low-turbulence pressure tunnel.

Report presenting a series of tests on the Brewster XSBA-1 airplane to determine the effects of various tail modifications. Some of the modifications include variations of the chord of the elevator and rudder while the span and total area of the surfaces are kept constant and variations of the total area of the vertical tail surface. Results regarding the longitudinal stability and control and lateral stability and control are provided.

Report presenting an analysis of the probable aerodynamic section characteristics of a plain flap with various arrangements of internal balance. The results of the calculations previously obtained were found to be in agreement with the experiment. Some possible applications of the data to balancing tabs are also provided.

Report presenting force-test measurements in two-dimensional flow made in the 4- by 6-foot vertical tunnel of the characteristics of an NACA 0015 airfoil with a balanced flap with a chord 30 percent of the airfoil chord and a flap-nose overhang 35 percent of the flap chord. Results regarding lift, hinge moment of flap, pitching moment, drag, and tab characteristics are provided.

Report presenting an investigation of the aerodynamic characteristics of a rectangular NACA 23012 airfoil with single and double perforated split flaps in the NACA 7- by 10-foot wind tunnel. A large range of flap spans and deflections and a large range of spanwise and chordwise locations of the flaps were investigated. Results regarding the double split flaps, single split flaps, diving speed, and aileron control are provided.

Pressure distribution measurements were made over an airfoil with slotted Frise aileron up to 0.76 Mach at various angles of attack and aileron defections. Section characteristics were determined from these pressure data. Results indicated loss of aileron rolling power for deflections ranging from -12 Degrees to -19 Degrees.

Report presenting a comparison of two flight-test procedures for the determination of the aileron control capabilities of an airplane. The procedures consist of performing rudder-fixed aileron rolls from straight unbanked flight and from steady turning flight. Results regarding rate of roll comparison and sideslip-angle comparison are provided.

Report describes the standard procedure that NACA used for evaluating the aileron characteristics of airplanes. The variables measured in the testing are rolling velocity, aileron positions, aileron stick forces or tangential wheel force, indicated airspeed, altitude, free-air temperature, and rudder position. The step-by-step flight procedure is described and information regarding evaluation of the control data and general suggestions is included.

Report presenting force tests in two-dimensional flow in the 4- by 6-foot vertical tunnel of the characteristics of an NACA 0015 airfoil with a balanced flap having a chord of 30 percent of the airfoil chord, a flap-nose overhang 50 percent of the flap chord, and a tab having a chord 20 percent of the flap chord. Results regarding the precision and presentation of data, lift, hinge moment of flap, pitching moments, drag, tab characteristics, and balancing effectiveness of various overhangs are provided.

Report discusses the maximum load, time to reach maximum load, and variation of load with time for prismatic floats in order to improve understanding of hydrodynamic theory for the landing impact of seaplane floats. Comparison of theoretical and experimental results and their applicability to flight impact are provided.

Report presenting wind tunnel testing of four full-scale seaplane floats to determine the aerodynamic characteristics of the floats and to evaluate several drag-reducing refinements. Four floats were investigated; two differed only in external details like flush rivets, while one was the type used on twin-float installations. The variation of lift, drag, and pitching moment with pitch angle are presented for each float.

"In connection with recent tests of a 1/4-scale model pursuit airplane in the NACA 8-foot high-speed tunnel, gun openings having low drag were developed for installation in the nose of the fuselage. The increase in the fuselage-drag coefficient for the final form of openings was 0.0132 at a Mach number of 0.69 and at an angle of attack of 0 degrees. The corresponding drag coefficient based on the wing area was about 0.0005. The critical speed of the airplane was not affected by the gun openings" (p. 1).

Report presenting an investigation in two-dimensional flow to determine the effect of leakage past the aileron nose on the aerodynamic characteristics of ailerons. The effects of amount and type of leakage, aileron contour, and Mach and Reynolds number are investigated.

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 an investigation in the two-dimensional low-turbulence pressure tunnel of three different types of NACA airfoil sections equipped with split flaps with chords 20 percent of the airfoil chord. The main purpose was to determine the maximum-lift characteristics of these low-drag airfoil sections with split flaps.

Report presenting information about airfoils in cascade, including the angle through which the air is turned and where the cascade losses are located.

Report presenting an investigation in the 7- by 10-foot wind tunnel to determine the aerodynamic section characteristics of several arrangements of an NACA full-span high-lift lateral-control combination. The combination consists of a full-span flap of airfoil profile that retracts ahead of a narrow-chord full-span aileron. Results regarding coefficients, precision, plain airfoil, determination of optimum aileron-flap arrangement, section aerodynamic characteristics, and lateral-control characteristics are provided.

"A comparison is made of the structural efficiencies of truss webs of 24S-T aluminum alloy with previously published values of the structural efficiencies of diagonal-tension webs of 24S-T aluminum alloy on the basis of identical allowable stresses. It is concluded that the diagonal-tension beam (web and flanges) can usually be built to be a more efficient beam than the truss beam, even though over a small range the web of a Warren truss beam is slightly more efficient than the web of a diagonal-tension beam" (p. 1).

Report presenting equations relating the various dimensions, air weight flow, and performance of a cross-flow tubular intercooler in which the charge flows through and the cooling air across the tubes. A method of determining and presenting the performance of a given intercooler at various operating conditions is indicated. Results regarding the cooling effectiveness equation, effect of primary intercooler variables, design charts, effect of tube arrangement on intercooler characteristics, and performance charts are provided.

"A unit injector was operated under various test conditions with a cam outline giving a high rate of plunger displacement. The rate of discharge of the unit injector followed the plunger displacement for the outwardly opening injection valve (open nozzle) except under conditions of high fuel pressures when the effect of fuel compressibility decreased the rate of discharge as the pressure increased. The rate of discharge for the inwardly opening injection valve (closed nozzle) did not directly follow the plunger displacement" (p. 1).

Report presenting a study of oil coolers, especially in regards to three factors: the congealing tendency of the cooler, the power cost chargeable to the installation, and the performance characteristics of the oil cooler in operation at altitude.

Report presenting tests conducted with an air-cooled aircraft-engine cylinder to determine the effect on the knocking tendency of cutting out one spark plug when the engine is operating at or near the knock point with two spark plugs firing. The results indicate that cutting out one spark plug will not lead to knock but will actually stop or decrease knock that is occurring with both spark plugs firing.

Report presenting an investigation of the performance of a mixed-flow impeller and vaned diffuser unit with several modifications in a variable-component supercharger test rig. The investigation covered impeller tip speeds from 800 to 1200 feet per second over the range of air flows from wide-open throttle to incipient surge. The results showed the supercharger to have a peak efficiency of 0.77 and a peak pressure coefficient of 0.61 with the impeller frontal clearance at 0.035 inch.

Report presenting a preliminary investigation to determine the suitability of ejectors actuated by the exhaust of a radial air-cooled aircraft engine for providing engine cooling air at the ground condition. Various length and diameter ejectors were tested for varying engine power for nine ejectors actuated by the exhaust of individual cylinders and three ejectors actuated by the exhaust of groups of three cylinders.