Report presenting an investigation of propellers designed specifically for pusher operation behind fixed contravanes on a large-scale model of a four-engine airplane. In the test, the wing trailing edge was twisted to serve as a contravane and to produce the rotating inflow required for optimum propulsive efficiency. Results indicated that gains in efficiency of about 3.5 percent at a blade angle of 40 degrees can be obtained by the use of contravanes with specifically designed pusher propellers.

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 a method and apparatus for making quantitative tests of the spray characteristics of flying-boat-hull models. The method is applied to three related models of flying-boat hulls which differed in one major characteristic of shape: the overall dead rise.

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.

Report presenting a description of the development of thermal ice-prevention equipment by the application of a heated-air ice-prevention system to a Lockheed 12A airplane. Test data indicated that thermal ice-prevention equipment is practical and that the method of utilizing the exhaust gases as a source of heat is satisfactory.

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 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.

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.

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 presenting a consideration of some problems related to longitudinal stability in power-on flight. The results indicated that the destabilizing effects of power are more pronounced when the horizontal tail is required to carry a down load to maintain flight equilibrium.

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.

"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 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.

From Summary: "Interdependence of intercooler parameters and performance for a pursuit-type airplane using a 1675-horsepower engine is shown at altitudes of 25,000, 36,000, 47,000, and 60,000 feet by means of perspective drawings. Qualitatively, the drawings have general application. Intercooling between stages of supercharging at high altitudes results in no saving in the power to supercharge and cool the engine air."

Data taken from tests at constant speed to establish trim limits of stability, tests at accelerated speeds to determine stable limits of center of gravity shift, and tests at decelerated speeds to obtain landing characteristics of several model hull forms were used to establish hull design effect on longitudinal stability of porpoising. Results show a reduction of dead rise angle as being the only investigated factor reducing low trim limit. Various methods of reducing afterbody interference increased upper trim limit.

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 presents tables of stiffness and carry-over factor for infinitely long flat plates subjected to a uniformly distributed longitudinal compressive load. The tables can be used to help solve problems in the stability of structures made out of plates under compression.

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.

Tests of 10-ft. diameter, eight-blade, single - and dual - rotating propellers were conducted in 20-ft propeller research tunnel. Propellers were mounted at front end of a streamline body in spinners that covered hubs and parts of shanks. Effect of a symmetrical wing mounted in slipstream was investigated. Blade-angle settings ranged from 20 Degrees to 65 Degrees. Results indicated that dual rotation resulted in gains of from 1 to 8 percent in efficiency over single rotation for eight-blade propellers, but presence of a wing reduced gain about one-half. Greater power absorption caused by dual rotation over flight range and higher efficiency or thrust for range of take-off and climb was indicated.

Principles of the cross method of moment distribution, which have previously been applied to the stability of structures composed of bars under axial load, are applied to the stability of structures composed of long plates under longitudinal load.

Report presenting testing of dynamic models that has been helpful in the determination of the longitudinal stability characteristics on the water of a number of specific flying boats. Results regarding the constant-speed tests, accelerated runs, effect of variations in moment of inertia, effect of variations in mass moving vertically, effect of variations of depth of step, and effect of variations of gross load coefficient are provided.