Report presenting an analysis of the effects of heat and compressibility in the flow through the internal systems of aircraft. Equations and charts are developed whereby the flow characteristics at key stations in a typical internal system may be readily obtained.

Tests were conducted on hydrofoil assemblies approximating an arrangement for use under seaplanes or surface boats. A series of hydrofoils, each supported by two struts, was towed at various depths ranging from partial submersions to a depth of 5-chord lengths. At depths greater than 4 or 5 chords, the influence of the surface of the water is small; hydrofoils operating at low speed will have characteristics similar to those of airfoils of the same section.

Report presenting tests of 10-foot diameter, single- and dual-rotating tractor propellers with two to eight blades conducted in the 20-foot propeller-research tunnel. The blades were 50 percent wider than those used in previous investigations. Results regarding the effect of dual rotation and effect of solidity are provided.

Report presenting flight tests conducted to measure the lateral-control characteristics of an airplane, equipped with a lateral-control system, in which as the flaps are lowered the ailerons droop and a gradual transition of lateral control from ailerons to spoilers takes place. The variation of maximum rolling velocity with lateral stick movement as obtained in abrupt rudder-locked rolls was satisfactorily smooth except when control was by spoiler alone.

"Three widely different nose shapes were tested on a fuselage alone and on a complete model in the UACA stability tunnel to investigate the effect of cowling shape on stability characteristics. The results are presented in the form of charts which show the variation in the aerodynamic characteristics with the three nose shapes for the propeller-removed condition over a wide range of angles of attack and yaw. The results of the investigation indicated that large changes in the cowling shape produced relatively small changes in the aerodynamic characteristics" (p. 1).

"Tests of a second representative bomber nacelle on a low-drag wing at a large value of the Reynolds number were made in the NACA two-dimensional low-turbulence pressure tunnel. Results show the drag and interference of the nacelle on the low-drag wing to be small" (p. 1).

Report presenting a theoretical study of the effects of aileron adverse yawing moment on lateral maneuverability at a high lift coefficient. The study included the effects of changes in effective dihedral angle, vertical-tail area, and tail length.

Report presenting an analysis of experimental and theoretical data, which indicates that critical evaluation of fuel performance, especially economy, must be made in the engine. Data show that heating value is, from the aspect of fuel economy, not so important an aviation-fuel specification as believed. The knock ratings of fuels are affected by spark advance.

Bulletin presenting the results of bending tests on a monocoque box with the door on the compression side. The results indicate that the effectiveness of a stress-carrying door depends on the intended function of the door.

Report presenting an investigation to determine whether the use of a 78 degree countersinking tool instead of a 82 degree countersinking tool for riveting would substantially alter the conclusion reached in a previous paper regarding the placement of rivets for maximum strength.

"Fatigue-tests were conducted on six specimens made from 3/4-inch-diameter 17S-T rolled-and-drawn rod for the purpose of obtaining additional data on the fatigue life of the material at stresses up to the static strength. The specimens were tested in direct tension using a stress range from zero to a maximum in tension. A static testing machine was used to apply repeated loads in the case of the first three specimens; the other three specimens were tested in a direct tension-compression fatigue machine" (p. 1).

Report presenting force-test measurements in two-dimensional flow in the 4- by 6-foot vertical tunnel to determine the characteristics of an NACA 0015 airfoil equipped with a straight-contour plain flap with a chord 30 percent of the airfoil chord. Results regarding the lift, hinge moment of flap, pitching moment, and drag are provided.

"This report covers tests of a 5-foot model of the NACA 66,2-420 low-drag airfoil at high speeds including the critical compressibility speed. Section coefficients of lift, drag, and pitching moment, and extensive pressure-distribution data are presented. The section drag coefficient at the design lift coefficient of 0.4 increased from 0.0042 at low speeds to 0.0052 at a Mach number of 0.56 (390 mph at 25,000 ft altitude). The critical Mach number was about 0.60. The results cover a Reynold number range from 4 millions to 17 millions" (p. 1).

Report presenting a study of the landing characteristics of various airplanes with special attention paid to problems with landing gear design. The planes ranged from 1000 to 50,000 pounds and in span from 28 to 149 feet. Results regarding the observed landing conditions, including attitude, vertical velocity, pitching velocity, rolling velocity, lateral velocity (or side drift), and landing gear loads measured during the tests are provided.

"The aileron characteristics of a Grumman F4F-3 airplane were determined in flight by means of NACA recording and indicating instruments. The results show that the ailerons met NACA minimum requirements for satisfactory control throughout a limited speed range. A helix angle of approximately 0.07 radian was produced with flaps down at speeds from 90 to 115 miles per hour indicated airspeed and with flaps up from 115 to 200 miles per hour" (p. 1).

"The results of a theoretical and experimental investigation to determine the critical compression load for a universal testing machine are presented for specimens loaded through knife edges. The critical load for the testing machine is the load at which one of the loading heads becomes laterally instable in relation to the other. For very short specimens the critical load was found to be less than the rated capacity given by the manufacturer for the machine. A load-length diagram is proposed for defining the safe limits of the test region for the machine" (p. 1).

"The Navier-Stokes stress principle is checked in the light of Maxwell's mechanism of friction and in connection herewith the possibility of another theorem is indicated. The Navier-Stokes stress principle is in general predicated upon the conception of the plastic body. Hence the process is a purely phenomenological one, which Newton himself followed with his special theorem for one-dimensional flows" (p. 1).

From Summary: "The results of 60 different tests on 2 aluminum alloy 17S-T plate girders are presented to show the influence of size and spacing of stiffeners upon the buckling characteristics of shear-resistant webs within the elastic range. It is demonstrated that stiffeners increase the stability of a web by retarding the formation subdivided panels. An empirical method of proportioning stiffeners is proposed which recognizes both of these stiffener functions, and comparisons are made with design procedures based upon theoretical considerations of the buckling problem. Also, some experimental data are provided to show the effect of stiffener size and spacing upon ultimate web strengths."

"A Wright GR-1820-G200 cylinder was tested over a wide range of fuel-air ratios at maximum permissible power output as limited by knock with three different degrees of valve cooling. The valves used were stock valves (solid inlet valve and hollow sodium-cooled exhaust valve), hollow valves with no coolant, and hollow valves with flowing water as a coolant. Curves showing the variation in maximum permissible values of inlet-air pressure, indicated mean effective pressure, cylinder charge, and indicated specific fuel consumption with change in fuel-air ratio and valve cooling are shown" (p. 1).

Report presents the results of tests of longitudinal stability characteristics of models of several flying boats conducted in the NACA Tank No. 1. These investigations were made for the purpose of (1) determining suitable methods for evaluating the stability characteristics of models of flying boats, and (2) determining the design parameters which have an important effect on the porpoising. This report is mainly concerned with the construction of suitable models, the apparatus, and methods used in the tests. The effect of changes in some design parameters is discussed.

Report presenting the flying qualities of the Supermarine Spitfire airplane. A variety of information regarding the construction, installation, longitudinal stability and control, and lateral stability and control are provided.

Report presenting ground-effect tests made in the LMAL 7- by 10-foot tunnel of a model of a low-wing, pursuit-type airplane equipped with a full-span 25-percent-chord slotted flap. Testing occurred at different heights and power conditions, and two stabilizer and elevator settings were used at each condition. Results indicated that the elevator deflection required for landing in a three-point attitude with the full-span slotted flap was considerably greater than that required with a partial-span split flap.

Report presenting a brief, nontechnical discussion of condensation trails for flying personnel. World maps showing trail-forming zones at different altitudes and seasons are presented. Means for suppression trails are given.

This technical memorandum presents a theoretical study of the processes accompanying the formation of ice on solid bodies. It discusses vapor pressure and sublimation in two air masses separated by a boundary area.