Report presenting an investigation of a thermal ice-prevention system for a Curtiss-Wright C-46 airplane, including the equipment for the wings, empennage, and windshield. The report is the third in a series and focuses on the revisions to the components for thermal ice prevention, the temperature- and pressure-measurement equipment installed in the airplane to determine the performance of the system, and the results of static-load structural tests of a specimen of the wing outer-panel leading edge.

Report presenting an investigation of a thermal ice-prevention system for a C-46 cargo airplane, which involved flight tests in dry-air and natural-icing conditions at two different laboratories. The purpose of the investigation was to determine the effectiveness of the C-46 airplane ice-prevention system and to continue the develop of thermal ice-prevention equipment. Results regarding the wing outer panel, wing tips, wing center panel, horizontal stabilizers, vertical fin, windshields, ice-removal tests, unprotected surfaces, and heat exchangers are provided.

Report discussing the use of two types of geared spring tabs for elevator control: ordinary (or ungeared) spring tabs and geared spring tabs. Their use in airplanes of various sizes and in comparison to conventional control systems is described.

Report presenting an investigation of an exhaust-air heat exchanger, which has been designed, constructed, and flight-tested for a C-46 cargo airplane. The primary purpose of the investigation was to provide the C-46 airplane with a satisfactory source of heated air and to continue the development of the heat exchanger as a part of thermal ice-prevention equipment. Results indicated that the required thermal output and desired air-temperature rise have been achieved and that the exchanger is suitable for use in the C-46 airplane.

Report presenting an investigation in the 7- by 10-foot wind tunnel of a large-chord NACA 23021 airfoil with a 15-percent-chord and a 25-percent-chord balanced split flap of Clark Y profile, to determine the aerodynamic section characteristics of the airfoil-flap combinations as affected by the size, nose location, and deflection of the flaps.

Report presenting an iteration method for determining the longitudinal control characteristics of a flexible horizontal tail. The method permits factors such as the actual spanwise variation of elasticity and the aerodynamic induction effects due to three-dimensional flow to be accounted for to any degree of accuracy needed. An analysis is also included of the effects of horizontal-tail flexibility on the tail effectiveness, the hinge-moment characteristics, and the control-force gradients in a dive recovery for two modern fighter airplanes.

Report presenting an investigation in the 7- by 10-foot wind tunnel of an NACA 23012 airfoil equipped with a Handley Page slat and a slotted and a split flap. The purpose of the investigation was to determine the aerodynamic section characteristics of the airfoil with and without flaps as affected by the location of the Handley Page slat. A range of slat-nose locations was investigated both with and without flaps at a constant slat gap.

Report presenting an investigation of ailerons with a beveled trialing edge and a blunt-nose overhang of 35 percent aileron chord on an NACA 66(215)-26 airfoil in two-dimensional flow. Five configurations were tested with various modifications of the aileron nose and adjacent airfoil contour to determine the effect of modifications on lift and aileron hinge-moment characteristics.

Characteristics are determined for various modifications of 0.155-chord blunt-nose aileron on semispan model of tapered fighter plane wing. Ailerons with 40 percent nose balance reduced high-speed stick forces. Increased balance chord increases effectiveness and reduces high-speed stick forces. Increased balance chord increases effectiveness and reduces adverse effects of gap at aileron hose. Increase of nose radii increased negative slope of curve hinge-movement coefficient plotted against deflection. Extended deflection range decreased aileron effectiveness for small deflections but increased it at large deflections. Peak pressures at noses of ailerons are relatively high at moderate deflections.

Report re-examining known procedures for handling general resistance testing on flying-boat hull models, with particular attention paid to saving test time and improving the usefulness of the results to designers. While specific testing will likely always be needed, the procedures given in the report for condensing resistance data should make data analysis easier to apply to design.

Summary presenting information on flush-riveted joints for aircraft construction, including the strength, occurrence of defects, and effect of the angle of rivet head. The current tests covers specimens from 15 manufacturers of which 5 series have been completed and are described in this report.

Report presenting a large air scoop designed for high critical speed, which has been tested in the 8-foot high-speed tunnel on the fuselage of a scale fighter-type airplane. The effects of boundary layer on scoop characteristics were found to be important at all inlet-velocity ratios. Results regarding the boundary-layer surveys, characteristics of original scoop installation, and characteristics of scoop with boundary-layer passage are provided.

Report presenting wind-tunnel testing in two-dimensional flow to investigate the aerodynamic characteristics of a flap balanced by a large overhang linked to deflect more slowly than the flap. Three lengths of blunt-nose overhang were tested linked to a 0.30-airfoil-chord straight-contour flap on an NACA 66-009 airfoil. Results regarding lift, hinge moment, drag, pitching moment, and practical considerations are provided.

Report presenting measurements in the full-scale tunnel of the pressure distribution over the horizontal tail surface of a typical pursuit airplane in order to determine the effects of propeller operation and angle of yaw on the tail load distribution. Most of the tests were made with the propeller operating to simulate climb conditions, high-speed dives, and pull-ups to various normal accelerations for a range of angles of yaw. Results regarding chordwise pressure distributions, spanwise distributions of normal-force coefficient, airflow measurements, and tail-load asymmetry are provided.

"The purpose of the present work is to extend the previous investigation and to derive additional airfoil sections designed to minimize the undesirable characteristics of the previously tested airfoils. The tests of these additional airfoils were made in the Langley two-dimensional low-turbulence tunnel (LTT)" (p. 2).

"The relation between the elevator hinge-moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance" (p. 1). Factors affecting stability positively and negatively are presented and potential modifications to the elevator control system are provided. The amount of solid friction present was found to be one of the greatest predictors of instability.

Report discusses the shear and normal stresses caused by a load applied until failure on the tension side of an open box beam with a flat stiffened cover. The maximum strain was found to be much less than in solid tensile specimens of the same material. Special attention is paid to the variation in strains at various parts on the beam and the potential effects of rivet holes and riveting, which requires further testing.

Report presenting compression testing on several series of flat panels with Z-section stiffeners with varying relative dimensions. The data presented show the effect of dimension ratio on the buckling stress for the sheet and on average stress at maximum load.

Force and flight tests were performance on an all-wing model with windmilling propellers. Tests were conducted with deflected and retracted flaps, with and without auxiliary vertical tail surfaces, and with different centers of gravity and trim coefficients. Results indicate serious reduction of stick-fixed longitudinal stability because of wing-tip stalling at high lift coefficient. Directional stability without vertical tail is undesirably low. Low effective dihedral should be maintained. Elevator and rudder control system is satisfactory.

Report discusses an investigation that was conducted to compare the strength and tightness of machine-countersunk flush-riveted joints assembled with NACA flush rivets and a type of commercial flush rivet. A comparison was also generated between the strength and tightness of counterpunched flush-riveted joints assembled with the same types of rivet. NACA's flush-riveted joints tended to be stronger and tighter than the commercial joints.

"The measurement of pressure distribution may be accomplished rapidly for any number of locations deemed necessary in model or full-scale investigations by use of the 'belt' method. Reasonable accuracy may be obtained by careful use of this method" (p. 1).

Report presenting the results of tests to determine the extent to which the knocking tendency of an air-cooled engine cylinder is increased when the cylinder head is poorly cooled and when the cylinder temperature exceeds the maximum specified by the engine manufacturer. The tests showed that, when the cylinder-head temperature was increase from 400 to 600 degrees Fahrenheit, the knock-limited indicated mean effective pressure was reduced 3 percent at a fuel-air ratio of 0.097 and 39 percent at a fuel-air ratio of 0.065.

Report presenting an investigation to find a means of obtaining undiluted exhaust-gas samples from a Wright R-2600-B aircraft engine equipped with short individual stacks. Preliminary tests to aid in determining the best design, location, and orientation of orifices ranging in size. Results regarding the Briggs & Stratton engine tests and Wright aircraft engine tests are provided.

Report presenting testing made on a Wright 1820-G single-cylinder engine to determine the effect of operating variables and the effect of shape and size of the exhaust stack on the visibility of exhaust gases for individual-stack installations. Flame damping was improved by decrease in nozzle-exit area, increase in stack length, and reduction in hydraulic diameter of the exhaust jets. Results regarding the characteristics of exhaust flames and damping of exhaust flames are provided.