Report presenting an investigation of the effects of propellers and of vibration on the extent of laminar flow on the NACA 27-212 airfoil by testing the airfoil in conjunction with a tractor and a pusher propeller and with a mechanical vibrator. The results show that neither the pusher propeller nor vibration with amplitudes up to 0.094 inch and with a frequency of 1650 cycles per minute had any consequential effect on the extent of laminar flow but that the tractor propeller had a very pronounced effect.

Report presenting flight and ground-cooling tests with a Northrop A-17A attack airplane to determine the merits of a nose-blower engine cowling designed and built at the NACA laboratory. The main objective was to determine the cooling characteristics of the nose blower, especially for ground and low-speed operation. Results regarding the cooling properties, engine pressure drop, and maximum speed and drag are provided.

Report presenting tests in the full-scale wind tunnel on 11 single-engine military airplanes to investigate methods for increasing their high speed. Results regarding the power-plant installation, flow characteristics, wings, cockpit canopies, landing gear, and air leakage are provided.

Report presenting tests conducted in the 8-foot high-speed wind tunnel of a scale model pursuit-type fuselage with practicable internal duct arrangement designed to meet all of the air requirements of a 1000-horsepower radial engine submerged at the maximum section. The results showed that the required internal flow can be obtained with negligible ducting losses provided that basic principles are observed in designing the air passages.

"Additional tests as recommended in reference 1 were made in the 7- by 10-foot wind tunnel of the 1/8-scale model of the Brewster F2A airplane to determine the angle of attack of horizontal tail and the elevator angles required for trim with flaps down" (p. 1).

Report presenting a study of the aerodynamic factors upon which the ability to perform the maneuver depends in an attempt to obtain a better understanding of the conditions involved and, if possible, to evolve criterions that may be used during design.

"An investigation of cowlings for long-nose radial engines was made on the Curtiss XP-42 fighter in the NACA full-scale wind tunnel. The unsatisfactory aerodynamic characteristics of all the cowlings with scoop inlets tested led to the development of the annular high-velocity inlet cowlings. Tests showed that ratio of cooling-air velocity at cowling inlet to stream velocity should not be less than 0.5 for this type of cowling and that critical compressibility speed can be extended to more than 500 mph at 20,000 ft altitude" (p. 1).

Report presenting an investigation of the effects of hub drag, solidity, dual rotation, and number of blades on the efficiency of high-pitch propellers. Testing occurred with two, three, four, and six-blade single propellers and four and six-blade dual-rotating propellers equipped with spinners and tested at a range of blade angles from 35 to 65 degrees. Results regarding a comparison of the large and small spinners, effects of spinners, comparison of constant-speed propellers, characteristics of constant-speed propellers, effect of solidity and dual rotation, effect of number of blades, and some peculiarities of four-blade propellers are provided.

Description is given of flight tests conducted on gun fairings, designed to correct the detrimental effects of the projecting and submerged wing guns on an F4F-3 fighter. It was found that the installation of unfaired guns on a clean wing resulted in a premature stall that increased the stalling speed in the carrier-approach and landing conditions of flight by suitably fairing the guns, it was possible to reduce the stalling speeds to values approaching very nearly the clean-wing values.

Report presenting testing on elbow shapes in airplane carburetor air intake ducts with low losses and good velocity distribution without the use of turning vanes. Results regarding the flow coefficient, velocity distribution, and comparison of a variety of elbow ducts are provided.

Problem of improving thrust at low speeds is primarily one of reducing angle of attack of operation of sections to improve L/D or reducing blade helix angle. An analysis, based on recent propeller data, is presented for determining improvements in thrust or efficiency which could be obtained by increased number of blades, increased blade width, increased diameter, dual rotation, and two-speed gearing. All methods were found very effective, particularly two-speed gearing.

Report presenting a theoretical investigation of the influence of changes in vertical tail area and dihedral angle on the lateral flying characteristics of an airplane. Lateral motions were computed for nine different combinations of vertical tail area and dihedral. Results regarding the lateral motions due to applied rolling moment with different amounts of accompanying pawing moment and lateral motions due to applied yawing moment are provided.

Report presenting an investigation in the 7- by 10-foot wind tunnel of an NACA 23012 airfoil with an 18.05-percent-chord Maxwell leading-edge slat and with a slotted and a split flap. The main purpose of the investigation was to determine the optimum slot gap of the Maxwell slat for, and the aerodynamic section characteristics of, the airfoil with several deflections of both types of flap.

"The data are presented in coefficient form and include lift, drag, and pitching-moment coefficients of the airfoil-flap comoinations and the normal-force, chord-force, and hinge-moment coefficients of the upper (perforated split) flap and lower (slotted) flap" (p. 1).

Report presenting testing in the two-dimensional turbulence tunnel of a model of the tip section of the wing of the XP-63 airplane. Several alterations of the skirts and balance on the internal-balance aileron were tested to obtain various aerodynamic characteristics of the aileron.

Bulletin presenting an investigation conducted to determine the effect of countersunk depth on the tightness of two types of machine-countersunk flush rivet. The specimens tested in the study were simple lap joints made by two different riveting methods. The results indicated that roundheaded rivets inserted from the back of the joint with the countersunk heads formed int he driving of the rivets produce tighter joints over a large range of depths than ordinary flush rivets.

Report presenting data pertaining to forces and moments developed by V-bottom planing surfaces of different angles of dead rise in order to compute the effect of dead rise on the lower trim limit of stability on a seaplane. Increase of angle of dead rise in the range of 10 degrees to 30 degrees causes an important increase in the lower limit of stability.

"Data from wind-tunnel measurements of elevator hinge-moment coefficients at high angles of attack are utilized in estimating elevator stick forces in spins. The analysis indicates that elevator forces on several current airplanes will be so high that the pilot will be unable to push the stick to the neutral position. Large nose balances involve danger of the elevator locking in the full-up position" (p. 1).

Report presenting flight tests to determine whether a towed body that was designed to meet certain specifications met the stability specification, which required that angular deviations in flight should be less than 1 degree. The requirement was met in flight in smooth air, but not in rough air, where the rolling motions were considerably larger.

Report presenting an investigation of rudder trim force change with speed and power, rudder force reversals in sideslips, and rudder positions in sideslips and straight flight of a P-40E airplane. Quantitative measurements of the items were made on three other vertical arrangements.

Report presenting a report regarding the basic factors of heat transfer applied specifically to aircraft heating and to guide the experimenter in planning experiments to obtain further data.

Report presenting the properties of some exhaust gases and air that are pertinent to airplane heat transfer calculations, including air, hydrogen, nitrogen, oxygen, carbon dioxide, and carbon monoxide. A bibliography related to gas properties is also provided.

Report presenting a study of two double tube cylindrical heat exchangers, in which hot exhaust gases pass through the annular space and ventilating air passes through the center tube, to determine heat transfer performance and pressure drop. Tests were performed in order to establish a simple, accurate method of predicting the performance of the double tube heat exchanger, to compare the performance of the straight and dimpled tubes, and to determine the pressure drop across the units.

Report presenting a study of two double tube, cylindrical, longitudinally finned heat exchangers in which hot exhaust gases pass through the annular space and ventilating air passes through the center tube in order to determine heat transfer and pressure drop performance.