Report presenting testing in the full-scale tunnel of the Grumman XF6F-4 airplane to investigate the factors that affect the directional stability and trim characteristics of a typical fighter-type airplane. Eight representative flight conditions were investigated in detail.

From Summary: "A method has been developed for interpreting v-g records taken during the course of commercial transport operation. This method involves the utilization of fairly simple statistical procedures to obtain "flight envelopes," which predict that, on the average, in a stated number of flight hours, one value of airspeed will exceed the envelope, and one positive and one negative acceleration increment will exceed the envelope with equal probability of being experienced at any airspeed. Comparison with the actual data obtained from various airplanes and from various airlines indicates that these envelopes predict the occurrences of large values of acceleration and airspeed with a high degree of accuracy."

Report presenting direct-reading tables and charts for determining the drag or thrust coefficients from wake-survey measurements in the subsonic speed range. Additionally, numerical examples are provided using information from the tables.

Report presenting a study of a family of three single-stage deep inducers designed to impart solid-body, or wheel, rotation in the entering air at constant rates along the axial depth of the inducers. The cast inducers tested were 4-inch axial depth with 24 blades, 4-inch depth with 12 blades, and 2-inch depth with 24 blades. Results regarding the cast inducers of the constant-angular-acceleration family, inducer section from the conventional impeller, and estimate of the inducer effect are provided.

From Summary: "A method of quantitative analysis for individual aromatic amines or mixtures of aromatic amines in hydrocarbon fuel blends by spectrophotometric measurement of ultraviolet-light absorption is presented. The effect of the precision of the spectrophotometric measurements, the purity of the aromatic amine, photochemical decomposition of the amine, and the composition of the fuel on the accuracy of the analysis is discussed and the results of tests of the precision of the procedure are given."

Report presents the results of rupture tests conducted on nine alloys for periods of up to 400 hours duration at 1700 and 1800 degrees Fahrenheit. The nine alloys tested were 6059, Vitallium, 422-19, 61, X-40, X-50 (all of which are precision-cast), S590, S816, and Low Carbon N155 (all of which are wrought). Information about range in rupture strength, a metallographic examination, Vickers hardness surveys, and the general properties of the alloys during testing is also included.

Statistical methods were applied to acceleration and airspeed data obtained with the XC-35 airplane during flights in turbulent air within convective clouds in order to determine the characteristics of repeated or closely spaced gusts pertinent to design problems. Results indicated that, in turbulent air within convective cloud, gusts tend to be contiguous and are seldom found isolated in space. Over-all average spacing between repeated gusts was in good agreement with twice the average gust-gradient distance of 10 chords used in present design.

Report discusses the results of a study of the ultraviolet absorption spectra in the 3200 A to 2500 A region of 27 aromatic amines in iscoctane and and in water solutions. Factors that affect the absorption spectra of aromatic amines were investigated, and the spectra in the two different solvents were compared. The main variables affecting the absorption are the nature of the solvent, the purity of the aromatic amines, and photochemical decomposition of the aromatic amines.

Report presenting a theoretical and experimental investigation of the behavior of a cantilever beam in transverse motion when its root is suddenly brought to rest. The results of both types of investigations are compared.

Report presenting a determination of the effectiveness of a charged condenser for breaking oil foams and to obtain data on which to base the design of such a device for mounting at the oil-tank inlet of an airplane. Results regarding the condenser-plate area and arrangement, wet-plate design, condenser voltage, oil temperature, water in oil, and some safety considerations are provided.

Report presenting compression tests on six 24S-T aluminum alloy curved sheet-stringer panels 12 inches in length and 24 inches in width, reinforced by six Zeo stringers spaced 4 inches between centers. The increase in developed width had no significant effect on the strain for buckling of sheet between stringers, the strain for buckling of sheet between rivets, the load carried per sheet bay, or the stress at failure.

Report presenting an investigation into the importance of stick force as a criterion of longitudinal stability with special reference to transient effects for maneuvers of short duration. The analysis showed that different combinations of elevator parameters which give the same stick force per unit acceleration in turns give widely different force variations during the entries into and recoveries from steady turns and during maneuvers of short duration such as abrupt pull-ups.

"An investigation has been made in the Langley free-flight tunnel to obtain an experimental verification of the theoretical rudder-free stability characteristics of an airplane model equipped with conventional rudders having negative floating tendencies and negligible friction. The model used in the tests was equipped with a conventional single vertical tail having rudder area 40 percent of the vertical tail area. The model was tested both in free flight and mounted on a strut that allowed freedom only in yaw" (p. 1).

Report presenting an evaluation of a number of samples of flight acceleration data under a variety of operating conditions to determine the total frequencies and the frequency distribution of atmospheric gusts. The samples include 1748 hours of operation by several airplanes of the domestic airlines of the United States, a Martin M-130 airplane, and a Boeing B-15 airplane. The results indicated that the distribution of gusts within turbulent regions of the earth's atmosphere follows a substantially fixed pattern regardless of the source of the turbine.

In open box beams subjected to torsion, secondary stresses arise owing to lateral bending of the spar caps. The present paper outlines a simple method for estimating the magnitude of these stresses and gives the results of tests of an open box beam in the neighborhood of a discontinuity where the cover changed from the top to the bottom of the box.

Report discusses an investigation into piston and ring friction as compared to total engine friction under natural operating conditions. Several test conditions were explored, including the effect of scuffing and excess cylinder-wall lubrication on friction. A device for measuring ring tensions and an apparatus for transforming pressure-crank angle indicator diagrams into pressure-volume indicator diagrams are also described.

Report presents the results of experiments on the resistance and porpoising characteristics of flying-boat hulls equipped with rectractable planing flaps. The ideal flap-hull combination would have hump-resistance characteristics at least equal to the XPB2M-1 flying boat and much better upper-limit porpoising characteristics with the flap retracted. Three ways that the flaps can be applied to a practical design are discussed.

Report presenting charts for the calculation of the critical stress for local instability of columns with I-, Z-, channel-, and rectangular-tube sections. An experimental curve is included for use in taking into account the effect of stresses above the elastic range on 24S-T aluminum alloy elasticity.

Report presenting a comparison of the results of calculations of the critical flutter speeds of nine uniform rectangular wings without ailerons by two methods: one in which the effect of the wing flutter shape is introduced indirectly by choosing mean values for the wing parameters and one that introduces an additional degree of freedom in the wing-bending flutter mode.

Report presenting a chart for the values of the coefficient in the formula for the critical shear stress at which buckling may be expected to occur in an infinitely long flat plate with parallel edges. An approximate method for the evaluation of the critical shear stress when the elastic restraints on the two parallel edges are not equal is also presented.

"A simple interaction curve is presented for evaluating the conditions of combined shear and direct stress under which an infinitely long, flat plate with equal elastic restraints against rotation along the edges will become unstable. The theoretical work that led to the interaction curve is presented in the form of appendixes" (p. 1).

Report presenting a correlation of the gross-load coefficient and the forebody length-beam ratio for a limited number of present-day multiengine long-range flying boats for which the spray characteristics are known. Results indicate that the gross-load coefficient for comparable spray characteristics varies as the square of the forebody length-beam ratio.

"Experimental results of tests made at the Langley Memorial Aeronautical Laboratory are presented to show how heat-transfer coefficients can be increased by a method utilizing the high rate of heat transfer known to exist on any heat-transfer surface in the region adjacent to the edge on which the cooling or heating fluid impinges. The results show that, for the same pressure drop, the average surface heat-transfer.coefficient can be increased 50 to 100 percent when a cooling surface having a length of four inches in the direction of fluid flow is cut to form twenty fins with a length of 0.2 inch in the direction of fluid flow and the fins are sharpened and staggered in the air stream" (p. 1).

Report presenting an investigation to determine the departure of the static pressure measured at fuselage static-pressure vents from the static pressure of the ambient air. Several locations for fuselage static-pressure vents on an XB-24F and a Lockheed 12A airplane.