Report presenting an investigation of the icing and de-icing characteristics of a Pratt & Whitney R-1830 engine induction system. The current report covers a program to determine the most effective rate and method of injection of de-icing fluid to remove a heavy ice formation from the induction system. Results regarding the flow rates, recovery times, de-icing portions of the runs, and ice formation characteristics are provided.

Report presenting the use of the Ackeret iteration process to obtain higher approximations than that of Prandtl and Glauert for the flow of a compressible fluid past a circular arc profile. The procedure is to expand the velocity potential in a power series of the camber coefficient.

Report presenting equations for calculating the stick-force characteristics obtained with a spring-tab type of elevator control. The main problems encountered in the design of the satisfactory elevator spring tab are to provide stick forces in the desired range, to maintain the force per g sufficiently constant throughout the speed range, to avoid undesirable "feel" of the control in ground handling, and to prevent flutter.

Report presenting icing tests on a Bendix-Stromberg PD-12F5 carburetor mounted on a Pratt & Whitney R-1830-C4 intermediate rear engine section. Limiting icing conditions were established for simulated cruising power and simulated rated power over a range of carburetor-air temperatures, and relative humidities are provided.

Report presenting pressure distribution tests of six NACA 16-series propeller sections with 1-foot chords in the 8-foot high-speed tunnel to determine the compressibility effects on peak section pitching-moment coefficients. Data is presented as curves of peak section pitching-moment coefficient against Mach number, thickness ratio, and camber. The peak pitching-moment coefficients were found to occur in the regions of positive and negative stall.

Report discusses an investigation to determine the aerodynamic section characteristics of an NACA 23021 airfoil with a double slotted flap with a chord 32 percent of the airfoil chord with the flaps at various positions. The maximum section lift coefficient, profile-drag coefficient, flap positioning, and effects of deflecting or removing the lower lip are described.

Correlation is established between aerodynamic characteristics of control surfaces in two-dimensional and three-dimensional flow. Slope of lift curve was affected little by overhang and balance-nose shape, but increased by sealing flap-nose gap. Effectiveness of balancing tab was same for sealed plain flap and unsealed overhang flap. Changes in hinge-moment coefficient were diminished by sealing gap. Values measured by three-dimensional flow disagreed with two-dimensional flow values until aspect ratio corrections were made.

Report discussing an investigation of the aerodynamic effects of horn balances with various plan forms and of guards on a horizontal tail surface. Rounding the adjacent horn and stabilizer edges causes negligible changes to aerodynamic effects except for the area moment of the horn. A solid horn guard mounted on the end of the stabilizer was found to increase the rate of change of lift with angle of attack and elevator deflection.

Report presenting tests of the NACA 65(sub 3)-018 airfoil section with boundary-layer control by suction in the two-dimensional low-turbulence and two-dimensional low-turbulence pressure tunnels. Results regarding the lift characteristics, flow coefficient, maximum lift, amount of air removed by boundary-layer control, pressure distributions, and boundary layer shape are provided.

Report presenting problems relating to the stability and control of tailless airplanes in consideration of contemporary experience and practice. Some observations in regards to small and large airplanes are provided.

Report presenting charts and formulas in convenient form for use in the computation of the effects of propellers on stability. Formulas are given for the contributions of the direct propeller forces to the airplane pitching moment, yawing moment, and shift in neutral point due to power.

An investigation was conducted to determine and compare the tensile strength of NACA and conventional machine-countersunk flush rivets of several rivet-head angles and varying countersunk depth. The results of the investigation are presented in the form of curves that show the variation of the tensile strength of the rivet with the ratio of the sheet thickness to the rivet diameter. For the same rivet-head angle and for a given angle of c/d, the NACA rivets developed higher tensile strength than the conventional rivets.

"The lubrication of a piston ring is treated as though the ring were a rigid slider of finite width. An expression is obtained for pressure distribution which takes into account the effect of oil leakage from the ends of the ring and which has the convenient form of an end correction to the pressure-distribution formula for an infinite slider. The important formulas are summarized for convenience and two examples are included of their use in finding the pressure pattern over wide sliders" (p. 1).

Report presenting the application of transient theory to the rational determination of dynamic loads on airplane structures during initial landing impact. Simplified procedures are described by which the distribution of the maximum attainable value of the dynamic stresses in the structure may be obtained.

Report on stability and control tests of the Bell P-63 series airplanes. Information about the spin characteristics, lateral control characteristics, longitudinal stability and control characteristics and directional stability and control characteristics is provided. A chronology of testing and detailed description of the airplane and its modifications are also provided.

Report presenting an investigation of underslung cooling-air ducts in various locations on a model of a typical single-engine tractor airplane in the full-scale tunnel. The report contains the results of tests of two forward underslung ducts. Results regarding pressure recoveries at the radiator, pressures behind the radiator, drag and duct efficiency, and critical speeds are provided.

Report presenting flight tests to determine the longitudinal stability characteristics of a pursuit airplane when flown with and without an experimental bellows-type bob weight. When the weight was installed, the stick-free static stability remained approximately constant irrespective of the shift in center of gravity resulting from a change in fuel quantity in the auxiliary fuselage fuel tank. Although the weight functioned satisfactorily, the performance could have been enhanced by the reduction of the friction in the mechanism.

Report discusses an investigation into the relation between the effects of cylinder-head temperature and inlet-mixture temperature on the knock limits of fuels. The tests were run at a constant fuel-air ratio and the decrease in cylinder-head temperature required to offset the effect of increasing the inlet-mixture temperature on knock-limited power was determined. The apparatus and testing procedure are described and the effect of changes in cylinder-head temperature on the knock limit of any fuel are plotted.

"An analysis is made to simplify pressure-drop calculations for nonadiabatic and adiabatic friction flow of air in smooth cylindrical tubes when the density changes due to heat transfer and pressure drop are appreciable. Solutions of the equation of motion are obtained by the use of Reynolds' analogy between heat transfer and skin friction. Charts of the solutions are presented for making pressure-drop calculations" (p. 1).

Report presenting testing to determine the best way to land the B-25 airplane in calm and rough water and to determine its probable ditching performance. By landing with flaps down in a tail-down attitude at as slow a speed as possible, smooth straight landing runs will probably result in calm water. Results regarding the effect of attitude, effect of flap setting, effect of simulated damage, effect of propellers, and effect of seaway are provided.

Report discusses the problem of large airplanes spinning and the fact that they should not be intentionally spun because they are not designed for the loads and speeds that may be encountered in spin and recovery. Stall and spin characteristics for large airplanes are described. Recommended piloting procedures in case of a large airplane spinning event are also provided.

Report discussing the knock-limited performance of blends of triptane and 28-R fuel in an F-4 engine at three sets of conditions and three compression ratios. The knock limits of the triptane blends were more sensitive to compression ratio than the 28-R fuel, and the sensitivities of the blends increased as the severity of other engine conditions increased.

Report presenting testing on a Chandler-Evans 1900 CPB-3 carburetor mounted on a Pratt & Whitney R-1830-C4 intermediate rear engine section to find the limiting conditions for no icing, icing that would not affect engine operation (visible icing), and icing that would affect engine operation. Results regarding classification and location of ice formations, effect of icing on fuel-air ratio, and ways to limit icing conditions are provided.

Report presenting knock-limited small-scale-engine tests of tulene, ethylbenzene, p-xylene blended individually in various concentrations with selected base fuels. Data was obtained for the aromatics to determine the blending sensitivity, the lead susceptibility, and the sensitivity of blends to inlet-air temperature.