Report presenting the results obtained in compression tests of eight stiffened panels. The radius-thickness ratio of the skin between stiffeners varied from 400 to infinity.

Report discusses the results of testing on the dynamic stability characteristics of various hydrofoil systems for seaplanes, including a flat-hydrofoil tandem system, a 20 degree V-hydrofoil tandem system, a curved-hydrofoil tandem system, a flat-hydrofoil ladder system, a Guidoni S.V.A.-type hydrofoil on a streamline spindle, and several self-propelled models, including the Tietjens hydrofoil system. The instability and spray were compared for the different systems.

Report presenting the results of tests of a model of a single-engine airplane with two different tilts of the propeller axis. The results indicate that on a typical design, a 5 degree downward tilt of the propeller axis will considerably reduce the destabilizing effects of power.

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 discusses the results of compressive testing of 24S-T aluminum-alloy sheet-stiffener panels with five ratios of stiffener thickness to sheet thickness. For each ratio, rivets of five different diameters were used to attach the stiffeners to the sheets. The compressive strengths were found to increase with an increase in the diameter of the rivets until the ratio of rivet diameter to over-all thickness reached a certain point.

Report presenting the flight tests of beveled trailing-edge ailerons on the North American XP-51 airplane which were extended to determine the aileron characteristics in high-speed dives. Standard recording instruments were used to determine airspeed, aileron position, stick force, and rate of roll. The results show that the beveled trailing-edge form of aerodynamic balance had no abnormal or unusual characteristics in high-speed flight.

Report discussing testing on a twin-engine airplane to determine which modifications would make it suitable for ground-support attack operations. Some of the suggested modifications include replacing fabric-covered elevators with metal-covered elevators with a balance tab, replacing fabric-covered ailerons with metal-covered ailerons with a balance tab, sealing the airplane, fairing the nose guns, removing the lower-periscope deflector, and fairing the bomb racks. The results of other types of configurations are included in the report.

"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 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 an investigation in the 7- by 10-foot wind tunnel of an NACA 23012 airfoil with a 15-percent-chord and a 25-percent-chord balanced split flap of Clark Y profile. The primary purpose was to determine the aerodynamic section characteristics of the airfoil as affected by the size, nose location, and deflection of the flap.

Report presenting a consideration of the general problem of stalling as affecting the safety of airplanes. The increased difficulties associated with modern efficient wings, particularly highly tapered wings and high-life devices, are discussed and means are considered for avoiding these difficulties.

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 an experimental model of a flight instrument that utilizes infrared radiations for detecting and indicating the location of clouds at night. A preliminary investigation is made of data in the scientific literature. A table and chart are developed that make it practical to determine the magnitude of the net exchange of radiation for any particular atmosphere of known composition and distribution of temperature.

Report discussing the results of testing conducted to determine the knock-limited performance of fuel blends containing 80 percent of S-2 reference fuel and 20 percent of several exploratory fuels. Butyl acetate, sec-butyl acetate, isopropyl acetate, sec-butyl alcohol, tert-butyl alcohol, isopropyl alcohol, cyclohexanol, methylcyclohexanol, isobutylcarbinol, sec-butylcarbinol, triethyl borate, and dimethylfuran were examined.

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 discusses a method developed to estimate the quantities of internal coolants required to prevent overheating of the aircraft cylinder when oxygen boost is applied. The formula and calculations related to inlet-air pressure, added oxygen, added water, added nitrogen, and total fluid weight are detailed.

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."