Report presenting an investigation using tight-fitting baffles on the cooling fins of several modern air-cooled engine cylinders in order to maintain a constant free-flow area from the front to the rear of each interfin air passage. Results regarding the effect of restriction in cooling-air flow paths on cylinder temperature and effect of restrictions in cooling-air flow paths on cooling-air mass flow are provided.

From Summary: "Compression tests were made of two groups of panel specimens with hat-section stiffeners. The groups were identical except that the flat sheet of one group was Alclad 24S-T81 and of the other Alclad 24S-T86. Results of the tests are given in tables or charts which show the average stress at which the sheet buckles and the average stress at the maximum load."

Report presenting testing in the pressure tunnel to determine the yaw characteristics of a scale model of a single-engine, fighter-type airplane with six-blade single-rotating and dual-rotating propellers. Force and moment characteristics are presented for several model and power conditions.

Report presenting a series of 25-hour accelerated high-output tests run on a single-cylinder aircraft-type spark-ignition engine to determine the effect of coaxial lapping of piston rings prior to engine operation. Standard cast-iron rings were used and tested with all rings lapped and with only the oil-control rings lapped. The results indicated that coaxial lapping with loose abrasive reduced both wear and scuffing.

Report presenting flight measurements of the pressures on the horizontal tail surfaces of a typical propeller-driven pursuit airplane during stalled pull-outs at high Mach number. Unit loads measured on the stabilizer at safe maneuvering limits were not only considerably in excess of the design unit loads, but also occurred in a direction opposite to the design loads. Revision of the tail-load design requirements and manner of specifying safe maneuverability limits to pilots appears necessary.

Report presenting flight testing of seven exhaust-gas-to-air heat exchangers on a B-17F airplane to determine their performance characteristics and to investigate their flame-suppression qualities. Testing was conducted to secure performance data of heat exchangers which might be suitable for use in the thermal ice-prevention and cabin-heating system of the heavy bomber-type airplanes.

Report presenting an analysis of the power losses in airplane flight of cross-flow plate and tubular intercoolers to determine the cooling-air weight flow and pressure drop that give minimum total power loss for any given cooling effectiveness. The investigation covers a range of flight conditions of altitude, airspeed, lift-drag ratio, supercharger-pressure ratio, and adiabatic efficiency.

"F-3 and F-4 knock data are presented for blends of 0, 20, 40, 60, and 80 percent by volume of triptane in 28-R reference fuel plus approximately 4.6 ml TEL per gallon in the final blends. For comparison of knock-limited performance, 28-R reference fuel containing 2.7 percent by volume of xylidines and leaded to 6 ml TEL per gallon is included. In order to provide information on temperature sensitivities, two sets of modified conditions were used in addition to the standard F-4 engine conditions" (p. 1).

Report presenting tests to investigate the effect of 2-percent additions of 11 aromatic amines on the knock-limited performance of AN-F-28 fuel. A total of 48 aromatic amines are being prepared for knock tests. Results regarding the knock-limited performance data, antiknock effectiveness, and knock-limited powers are provided.

Report presenting a combination oil sump and scavenge pump constructed to eliminate some of the oil-system difficulties in an aircraft engine that result from the aeration of the scavenged engine oil and air-lock of the scavenge pump. Information regarding test results and design recommendations are provided.

"A method for the estimation of the maximum stresses around a small rectangular cut-out in a sheet-stringer panel loaded in pure shear is presented; this method is based on a simplified application of the shear-lag theory. Comparisons indicate that the experimental maximum stringer and shear stresses agree reasonably well with the predictions, provided that neither the length nor the width of the cut-out is greater than the half-width of the panel" (p. 1).

"Following a brief history of the NACA investigation of jet-propulsion, a discussion is given of the general investigation and analyses leading to the construction of the jet-propulsion ground-test mock-up. The results of burning experiments and of test measurements designed to allow quantitative flight-performance predictions of the system are presented and correlated with calculations. These calculations are then used to determine the performance of the system on the ground and in the air at various speeds and altitudes under various burning conditions. The application of the system to an experimental airplane is described and some performance predictions for this airplane are made" (p. 1).

Report presenting testing of several designs of nitrided-steel piston rings under variable conditions of output. Testing indicated the importance of good surface finish and conformity of the ring to the bore. Results regarding temperature tests, single-cylinder-engine tests, and multicylinder-engine tests are provided.

Report presenting the development of a method of evaluating the epsilon-integral occurring in the arbitrary airfoil theory of Theodorsen by retaining higher order terms in the Taylor expansion and by use of Simpson's rule. Formulas are given for routine calculation of the epsilon-integral and for the necessary computational coefficients.

Report presenting an investigation to determine the possibility of attaining or approaching critical-altitude power at altitudes considerably higher than the critical as limited by the supercharger by the use of oxygen in conjunction with internal coolants.

Report presenting preliminary tests in tank no. 1 to investigate the hydrodynamic qualities of a streamline body of revolution of a fineness ratio of 5.14 with and without a lifting hydrofoil. Results regarding interference, incidence, spray, trimming moment, comparison with a conventional float, and aerodynamic drag are provided.

Report discusses the results of strength tests of several curved-sheet 24S-T aluminum alloy specimens stiffened longitudinally and transversely and loaded in shear. Curved-web beams and cylindrical shells were both examined in the tests. Results provided include the load at which the sheet began to show shear buckles, where the buckles occurred, and whether or not the failures involved rupture of the sheet.

Report presenting testing of a model of the Northrop XB-35 airplane in the free-spinning tunnel in order to determine the spin characteristics and tumbling tendencies of the airplane. The spin tests indicated that for the normal loading condition, the model would not spin in the direction of the rudder for either the clean or the landing condition unless the wheel was set over with the rudder. Results regarding the spin tests in the clean condition, spin tests in the landing condition, tumbling tests, and consideration of control forces are provided.

Report discusses the results of an investigation into the oscillations performed by suspended bodies like trailing airspeed heads and other towed devices. The most violent types of instability observed were found to be caused by unsteady or nonuniform air flow where the cable was lowered from the airplane. No method was found for reducing cable oscillations in short cable lengths, but the degree of stability present was considered satisfactory as long as the suspended body is lowered into a uniform air stream.

Report discusses the results of testing of 10-inch 24S-T aluminum alloy shear panels with 1.5 inch holes with notched edges to determine if a notch decreases the strength of the panel and if reinforcements can overcome the negative effects of the notch. The notch did appear to increase the stress concentration around the holes, but the lack of applicability to real-world scenarios is discussed.

Report presenting wind tunnel tests of NACA 65(216)-420 and 66(218)-420 airfoils at speeds up to and slightly above the critical. Section coefficients of lift, drag, and pitching-moment and extensive pressure-distribution data are presented. The critical speed for these airfoils at their design life coefficient of 0.4 is shown to be about 460 miles per hour at seal level and about 415 miles per hour at 25,000 feet altitude.

Report presenting a wind tunnel investigation of a beveled aileron shape designed to increase the useful deflection range. The purpose of the investigation was to determine the general aerodynamic characteristics of this aileron and, in particular, to determine its useful angular range. Results regarding the effect of the hinge-gap seal, the surface condition and Reynolds number, and effect of aileron profile are provided.

Report discusses pressure-distribution tests of a plain flap with interchangeable beveled trailing edges on an NACA 0009 airfoil. The flap chord was 30 percent of the airfoil chord and the bevel chords were 15 and 20 percent of the flap chord. The purpose of these tests was to supply pressure-distribution data that may be used for structural and aerodynamic design of horizontal and vertical tail surfaces.

Report presenting force tests in two-dimensional flow in the 4- by 6-foot vertical tunnel to determine the aerodynamic characteristics of an NACA 0009 airfoil with flaps having chord at 3 locations of the airfoil chord and three degrees of the beveled trailing edges. The results indicated that, with a smooth leading edge, the increased trailing-edge angle on the flaps with sealed gaps decreased the slope of the control-fixed lift curve and the lift effectiveness.