"Ground tests were conducted on a twin-engine fighter airplane to study icing of an induction system incorporating an exhaust-driven turbosupercharger. The ground tests were made to determine the disposition of free water in the induction system of the airplane, to determine the charge-air heat rise available from the turbosupercharger, and to correlate actual airplane-test results with those of laboratory tests" (p. 1).

From Introduction: "The purpose of this investigation was to develop a method for determining directly the friction force between the piston and cylinder of an internal combustion engine. The method consists in elastically mounting the cylinder barrel so that it can have a small motion parallel to its axis, and providing suitable means for recording its instantaneous displacement."

Report presenting an investigation of the properties of a 20-inch diameter by 3.25 inch disc of 19-9 DL alloy in the as-forged and stress-relieved condition. Results regarding the hardness survey, short-time tensile properties, rupture test characteristics, time for deformation characteristics under stress, creep strengths, and stability characteristics are provided.

Report presenting the results of a study of the rupture-test characteristics of 13 wrought and 4 cast alloys which were considered to have promise for service in exhaust gas turbines. The results are given in the forms of a table of information and data, a page of curves, and a page of photomicrographs.

Report presenting elementary basic solutions of the equations of motion of a compressible fluid in the hodograph variables are developed and used to provide a basis for comparison in the form of velocity correction formulas, of corresponding compressible and incompressible flows.

Report discussing testing to determine the cooling effect of modified baffles and auxiliary-cooling ducts on the rear-row cylinders of a double-row radial engine. The modified baffles were found to reduce the temperatures of the exhaust-valve seats, but did not have an effect on the valve-guide temperatures. The auxiliary-cooling ducts reduced temperatures of the exhaust-valve seats and rear spark plug gaskets.

Report presenting an examination of new and used nitrided-steel piston rings by electron and X-ray diffraction in a study of the surface changes produced during engine operation. Both new and used rings, examined after degreasing, gave an electron-diffraction pattern consisting of diffuse bands: those from used rings fell at the usual positions of the bands from polished metal surfaces.

Report discusses the thrust and power characteristics of several single- and dual-rotating propellers with differing blade width and number of blades for negative-thrust operation from -45 degrees to 145 degrees blade angle. From Summary: "The tests indicate that it is possible to predict for a given propeller design characteristics in the negative-thrust range from known characteristics at a different activity factor. Adequate negative thrusts were indicated for extremely high positive as well as negative blade angles."

Report presenting charts showing the variation in dynamic stability with the rudder hinge-moment characteristics. A stabilizing rudder floating tendency combined with a high degree of aerodynamic balance is shown to lead to oscillations of increasing amplitude.

"Results of performance measurements made in level fight with the HNS-1 (Army YR-4B) helicopter are presented. These data include torquemeter measurements of shaft power for both the main rotor and the tail rotor. The power data, in conjunction with full-scale-tunnel date on the lift and drag of the fuselage, are used to calculate the drag-lift ratio for the main rotor" (p. 1).

Report presenting a study of several sample helicopters in order to evaluate the effect of rotor-tip speed on hovering performance and limiting forward speed. The main purpose of the study was to determine whether hovering performance could be increased by the use of lower tip speeds without undue sacrifice in maximum forward speed. Results regarding typical helicopters, low-solidity helicopters, and high-speed helicopters are provided.

Report presenting an electric torquemeter that was used to measure the power of an Allison V-1710-93 engine installed in a Bell P-63A-1 airplane. Results of maximum-available-power tests in flight at a range of density altitudes showed good agreement between the measured maximum power output and the maximum power shown on the engine manufacturer's calibration chart.

Report presenting an investigation in the 7- by 10-foot wind tunnel of three plain ailerons on an NACA 23012 wing with full-span combinations of Fowler and split-type flaps. Static rolling, yawing, and hinge moments were determined and are presented for several angles of attack and flap deflection. The results indicated that a plain sealed aileron with internal balance will provide lateral control for airplanes equipped with full-span combinations of slotted and split-type flaps.

Report presenting an investigation of thirteen exhaust-gas-to-air heat exchangers to determine the practicability of the use of such heat exchangers in the thermal ice-prevention systems on aircraft. The results show that the exchangers constitute an excellent source of heated air for aircraft ice prevention and can be constructed to resist thermal and vibrational stresses.

Report presenting tests of wing-fuselage combinations employing an airfoil-type fuselage in the variable-density wind tunnel as part of a wing-fuselage program. The models were designed to simulate an existing moderate-size transport airplane of that type. Results regarding some general comparisons, lift distribution and induced drag, and drag in high-speed flight are provided.

Report presenting knock-limited tests using F-4, F-3, and 17.6 small-scale engines and a full-scale cylinder on blends containing four different types of hydrocarbons. Each of the hydrocarbons was individually blended in various concentrations with three base fuels.

Report presenting knock-limited performance tests of leaded blends of four pure aromatic hydrocarbons and six pure ethers with a base fuel in a full-scale aircraft-engine cylinder at two operating conditions to determine the antiknock effectiveness of additions of pure compounds to aviation fuels.

Report presenting wind tunnel testing to investigate the possibility of reducing the hinge moments of a control surface by beveling the trailing edge. Tests were made with a 9-percent-thick airfoil with a 30-percent-chord plain flap. Results regarding the variations of lift and hinge moment, effect of shapes, and pitching moments are provided.

Report discusses the results of an investigation to determine the effect of extreme changes in mass distribution along each of the three body axes. The effects of individual inertia moment parameters upon spin and recovery characteristics were examined.

Report presenting tests of spin-recovery parachutes on six models of typical fighter and trainer airplanes conducted in the 20-foot free-spinning tunnel to obtain data for correlating model and full-scale results. Parachutes attached to the tail of the models, to the outer wing tip, to the inner wing tip, and to both wing tips were tested. Results regarding parachute construction, loading variations, effect of test altitude, and action of spin-recovery parachutes are provided.

Tests in Langley pressure tunnel of model XA-26 bomber were compared with those of A-26B (twin-engine attack bomber) and showed that static longitudinal stability, indicated by elevator-fixed neutral points, and variation of elevator deflection in straight and turning flight were good. Airplane possessed improved stability at low speeds which was attributed to pronounced stalling at root of production wing. At rudder-force reversal at speeds higher than those in flight tests, agreement in rudder-fixed and rudder-free static directional stability was good. Hinge moment obtained at zero sideslip was satisfactory for determining aileron forces in sideslip.

Report explores the periodic forces that helicopter rotors are subjected to, both horizontal and vertical, and several configurations and material combinations of blades are described. The vibrations and exciting forces are demonstrated through calculations and explored with combinations of one, two, three, and four blades.

From Introduction: "In the present paper a numerical procedure for the stress analysis of flat-sheet and stringer combinations of arbitrary construction and loading is presented and applied to axially loaded panels and to the reinforced covers of box beams."

Report presenting flight tests of an all-movable horizontal tail installed on a Curtiss XP-42 airplane due to its possible advantages as a longitudinal control at high Mach numbers. The elevator control was found to be unsatisfactory with the control arrangements tested.