An experimental investigation is being conducted to determine the effect of varying the rivet diameter and pitch on the compressive strength of 24S-T aluminum-alloy panels with longitudinal Z-section stiffeners. The average stress at failing load for each rivet diameter, depth of countersink, and pitch of rivet is provided

Bulletin presenting testing of a monocoque box with a stress-carrying door made and tested in torsion. The results indicate that if a stress-carrying door and its frame are made sufficiently heavy, the torsional stiffness of the box with the door can be made greater than the torsional stiffness of the box without the cut-out" (p. 1).

Report discusses data obtained from measuring sideslip characteristics via the continuous-record method and the steady-record method. The situations in which each recording method is preferred are presented.

Report discussing some calculations made for the effects of water in cooling the inlet air of aircraft-engine cylinders. From Summary: "The estimates indicate that the cooling effect of the water on the inlet air can be more extensive than the cooling now obtained with the intercoolers or aftercoolers in the air-induction system. In connection with water recovery from the exhaust gas, the estimates indicate that sufficient water can be recovered from 50 percent of the exhaust gas to provide an inducted water-fuel ratio of 0.5."

Report discusses the results of testing water injection on a multicylinder aircraft engine and the potential fuel savings from the procedure. The speeds at which water injection for engine cooling is beneficial are illustrated and information about the manifold pressures and average rear spark-plug-gasket temperatures are also included.

Report discusses testing performed to determine the fatigue strength of various types of riveted and spot-welded joints in the following aluminum alloys: Alclad 24S-T, 24S-RT, 758-T, 24S-T81, and 24S-T86. Details of the experiment, tensile properties, and information about failure are provided.

Report discusses some unusual velocity-acceleration records on transport airplanes, which the report defines as "records of accelerations experienced in flight that resulted from causes other than atmospheric gusts" (from Summary). The analysis of the records, which is required for determining proper classification, is described, and the sorting of the records into gust- or maneuver-related is described. The report also discusses the importance of receiving this data from flight operators in addition to the routine information they provide.

"An electronic circuit for instantaneously indicating angular velocity and acceleration, both positive and negative, of rotating masses is described; readings are taken on electrical indicating meters. The indicator is described in terms of general application. A circuit diagram, calibration curves, and a mathematical analysis of the differentiation circuit are included" (p. 1).

Report discusses the differences between the mean tangential velocity of the air leaving the blade tips of a centrifugal supercharger calculated by the conventional turbine equation and by an equation that uses the isentropic increase in total enthalpy. The velocities are compared to experimental values observed with three diffusers.

"An experimental study was made to determine the effect of artificial aging on the tensile properties of alclad 24S-T and 24S-T aluminum-alloy sheet material. The results of the tests show that certain combinations of aging time and temperature cause a marked increase in the yield strength and a small increase in the ultimate strength; these increases are accompanied by a very large decrease in elongation. A curve is presented that shows the maximum yield strengths that can be obtained by aging this material at various combinations of time and temperature" (p. 1).

Results are presented of tests of two specimens tested to study the effect of normal pressure on the critical compressive stress for thin curved sheets. These specimens are designated by their respective rib spacings of 10 inches and 30 inches. The relationship between compressive stress and normal pressure at which buckles disappeared is independent of whether the buckles were made to disappear by increase of normal pressure or decrease of compressive stress. (author).