Report presenting the results of tests of a model of a single-engine airplane with two different tilts of the propeller axis. The results indicate that on a typical design, a 5 degree downward tilt of the propeller axis will considerably reduce the destabilizing effects of power.

Report presenting an instrument for warning the pilot of the approach of the airplane to critical speed conditions. The device closes a contact that completes the electrical circuit of a suitable warning indicators when a predetermined limiting Mach number is approached. It can be used to operate any electrical apparatus through the use of suitable relays.

Rough conventional, smooth conventional, and laminar-flow or low-drag sections were tested. The items covered are rotor thrust for fixed power in hovering, range and endurance at cruising speed, and power required at high-forward speed. Calculations indicated that a smooth conventional section gives marked performance gains. Smaller gains are obtainable by using a low-drag section. At high speeds or loads the low-drag section is inferior to the smooth conventional section.

Report presenting an investigation of the effects of 0.20-aileron-chord tabs on an NACA 66,2-216 airfoil equipped with a 0.20-airfoil-chord plain sealed aileron. Basic data are presented from which the effect of tabs can be calculated for specific cases. The data are sufficient for the solution of problems of fixed tabs with a differential linkage, as well as simple and spring-linked balancing tabs.

Report presenting a cascade investigation in two-dimensional flow in the 5-inch cascade tunnel and the 1-inch turbine-element testing apparatus to obtain a satisfactory bucket design for use in a modern aircraft turbosupercharger. Results regarding the root sections, pitch sections, and tip sections are provided.

Report presenting the utilization of the differential equation of Chaplygin's jet problem to give a systematic development of particular solutions of the hodograph flow equations, which extends the treatment of Chaplygin into the supersonic range and completes the set of particular solutions. The solutions serve to place on a reasonable basis the use of velocity correction formulas for the comparison of incompressible and compressible flows.

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 presenting an investigation to determine the design-performance characteristics of the eight-stage axial-flow compressor and the effect of altitude on the performance. The design pressure ratio of 5:1 was obtained at an adiabatic temperature-rise efficiency of 83 percent, a simulated altitude of 36,000 feet, and a compressor Mach number of 0.95.

Report presenting cast-iron piston rings that were run in nitrided-steel cylinder barrels under scuffing conditions and showed a coating material on the scuffed areas. Only a few of the 14 etching reagents that were tried attacked the coating chemically, indicating good corrosion resistance. Results regarding the occurrence of coating, metallurgical characteristics, and chemical characteristics are provided.

Report presenting testing of 0.15-wing-chord, internally balanced ailerons on a low-drag tapered wing at Mach numbers up to 0.75. Both a normal-profile and beveled trailing-edge aileron were tested without a seal and with a partial seal. Results regarding variation of lift, static characteristics of the ailerons, aileron control characteristics, pitching moment induced by ailerons, balance pressures, and pressure distributions are provided.

Report presenting wind-tunnel tests in two-dimensional flow to investigate the aerodynamic characteristics of a double flap with an internal and overhang balance. Three sizes of each type of balance were tested with three relative rates of deflection of the two flaps. Results regarding lift, hinge moment, drag, and pitching moment are provided.

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.

Results of subject tests indicate the difficulty of obtaining closely balanced rudder surfaces for most tail assemblies with shielded horns and maintaining a near zero rate-of-change of hinge-moment coefficient without an additional balancing device. A comparison is made between shielded and unshielded horn test results. Pressure distribution and tuft tests of flow over different shaped horns showed higher critical speed for medium-taper nosed horn. The trim tab nose shape had little effect on tab test results.

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.

From Summary: "The results of an analytical investigation to determine the qualitative effects of elevator-fabric distortion on the stick-force characteristics of an airplane are presented. These results indicate that serious alteration of intended stick-force characteristics can be produced by elevator-fabric distortion."

Report presenting an investigation in the 19-foot pressure tunnel to determine the nacelle drag, the cowling-air flow, and the propeller characteristics of a model of a high-performance military airplane. The model is fitted with NACA D(sub S)-type engine cowlings and with propellers embodying NACA 16-series airfoil sections. Results regarding the propeller characteristics, drag and cowling-air flow with the propeller removed, the effect of propeller on flow through cowling, and the influence of cooling requirements on airplane performance are provided.

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.

In this report a method is presented for the calculation of the profile drag of airfoil sections. The method requlres only a knowledge of the theoretical velocity distribution and can be applied readily once this dlstribution is ascertained. Comparison of calculated and experimental drag characteristics for several airfoils shows a satisfactory agreement. Sample calculatlons are included.

"A series of charts are presented by which the wing torsional stiffness required to meet a given standard of rolling effectiveness may be quickly determined. The charts may also be used to obtain quickly the aileron reversal speed and the variation of the loss in rolling effectiveness with airspeed. The charts apply to linearly tapered wings and elliptical wings of tubular-shell construction having various aspect ratios with aileron span and location of ailerons as variables" (p. 457).

"A study was made of the performance of a jet-propulsion system composed of an engine-driven blower, a combustion chamber, and a discharge nozzle. A simplified analysis is made of this system for the purpose of showing in concise form the effect of the important design variables and operating conditions on jet thrust, thrust horsepower, and fuel consumption. Curves are presented that permit a rapid evaluation of the performance of this system for a range of operating conditions" (p. 1).

From Introduction: "The present paper deals with control surfaces having plain-overhang and Frise balances."

Report presenting flight data, which shows that the absolute minimum or limit pressure coefficient on an airfoil is a function mainly of the Mach number for Mach numbers above about 0.3 and for usual flight values of the Reynolds number. The curve of limit pressure coefficient as a function of Mach number is established.

Report presenting the use of current methods that include interference and compressibility effects to estimate pressures over and near turrets located on a wing in regions of high interference velocities. The agreement between measured and estimated pressures indicated that present methods are adequate for predicting approximate critical speeds and for estimating loads at subcritical speeds with sufficient accuracy for design purposes.

"Test data of balanced ailerons have been collected from NACA and British sources. These data, which are presented in the form of charts, are grouped as A - ailerons with Frise balances, B - ailerons with blunt-nose balances, C - ailerons with internal balances, D - ailerons with contour modifications, and E - ailerons with tabs. Results of flight tests and of wind-tunnel tests in both two- and three-dimensional flow are presented but no correlation nor resume of the data has been included" (p. 1).