The problems of static and dynamic longitudinal stability both at high speeds and at low speeds are discussed and data are presented which indicate recent progress made in the solution of these problems.

This report contains a selected list of Government sponsored research projects on related aircraft materials in effect during the calendar year 1947. Information is contained on titles, description, sponsoring and conducting agencies.

The effects on dynamic lateral stability and controllability of some of the important aerodynamic and mass characteristics are discussed and methods are presented for estimating the various stability parameters to be used in the calculation of the dynamic lateral stability of airplanes with swept and low-aspect-ratio wings.

Report presenting an investigation to study cowling-spinner combinations based on the NACA 1-series nose inlets and to obtain systemic data for one family of approximately ellipsoidal spinners. 11 of the spinners were also tested in various combinations with 9 NACA open-nose cowlings, which were also tested without spinners. Results regarding flow over spinners, internal flow, external flow over cowling, critical Mach number characteristics, envelope values, and cowling section are provided.

Report presenting a wind-tunnel investigation to explore the merits of split and chord-extension flaps on a 45 degree sweptback wing. Testing occurred at low speed on a semispan model equipped with split flaps of 60 and 90-percent span and a full-span chord-extension flap. Results regarding split flaps, chord-extension flap, and resultant lift coefficients after balancing pitching-moment coefficients are provided.

Aerodynamic and icing investigations of internal water-inertia separation inlets designed to prevent automatically entrance of large quantities of water into a turbojet engine in icing conditions was conducted on a one-half scale model. A simplified analytical approach to the design of internal water-inertia separation inlets is included. Results show that in order to be effective in preventing screen and guide-vane icing for an inlet of this type, a ram-pressure recovery of 75 percent was attained at design inlet-velocity ratio in an icing condition. For nonicing operation, ram-pressure recovery is comparable to direct-ram inlet.

Report presenting an investigation of the rolling effectiveness of a wing-spoiler arrangement using a rocket-propelled test vehicle in free flight. The configuration investigated in the report is likely not optimum and indicates a need for further exploration.

Report presenting measurements of downwash angles at points at two vertical positions at the probable tail location behind a high-aspect-ratio wing with an NACA 65-210 section with no sweep and 30 degrees and 45 degrees of sweepback and sweepforward in conjunction with a fuselage.

Report presenting an investigation of the problems of static and dynamic longitudinal stability both at high speeds and low speeds as well as information about progress that has been made to solve these problems. The incorporation of large amounts of sweepback on both the wing and horizontal tail can improve the rate of trim changes and stability. Longitudinal stability has been attained for configurations with a sweep angle of 45 degrees with stall-control devices, but experimental proof is needed for these devices.

From Summary: "Theoretical performance data including nozzle-exit temperature, specific impulse, volume specific impulse and composition, temperature, and mean molecular weight of reaction products based on frozen equilibrium and isentropic expansion are presented for 13 propellant combinations at reaction pressure of 300 pounds per square inch absolute and expansion ratio of 20.4. On basis of maximum specific impulse alone, five fuels had the following order for any given oxidant: liquid hydrogen, hydrazine, liquid ammonia, and either hydrazine hydrate or hydroxylamine. Three oxidants with a given fuel had the following order: liquid ozone, liquid oxygen, and 100-percent hydrogen peroxide."

"This report presents the results of pilot observations and photographs of the compression shock wave on the wing of an airplane in flight. A detailed description of the test conditions necessary and the procedure to be following in producing the visible shock are presented. The pilot's observations of the occurrence of an oscillating shock wave and its possible relationship with the airplane buffeting are also presented" (p. 1).

Report presenting testing of a 42.7 degree sweptback tapered wing with three types of ailerons tested at a Mach number of 1.9 and a Reynolds number of 2,200,000; the wing geometry was similar to that of an XS-2 airplane. The purpose of the investigation was to determine the effectiveness of ailerons at these specified flight characteristics. Results regarding the aerodynamic characteristics of the wing are also provided.

Memorandum presenting a review of information relating to aircraft fires to determine what new or further research might lead to a substantial reduction of the aircraft fire hazard in flight and following crashes. An examination of fuels, lubricants, and hydraulic fluids as inflammable liquids is presented, together with possible sources of ignition under the general categories of hot surfaces, electric sparks and arcs, flames, and hot gases.

Report presenting testing on a series of five flat plate models of aspect ratio 2.0 with 25-percent-mean-aerodynamic-chord flaps at a range of Mach numbers in order to investigate the effect of sweepback on flap effectiveness.

Report presenting an investigation of a series of 16-inch-diameter ramjet engine in free flight in order to determine the performance of ramjet units in flight at supersonic speeds and to study methods for improving the performance. Results regarding the telemeter data recorded by ground stations, static pressures, variation of altitude with time after release, variation of flight velocities, and fuel-air ratio are provided. Partial failure of the measuring equipment prevented a complete evaluation of engine performance.

Report discussing an investigation on the effect of engine skew on the directional and lateral control characteristics of a single-engine airplane with a single-rotating propeller. The estimated and test results showed an advantage to skewing the propeller, as it assists with overcoming inadequate rudder control in power-on flight and aileron control, especially with flaps deflected.

"An investigation has been conducted to determine whether three-dimensional flows may be utilized in axial-flow fan and compressor rotors so that the spanwise load distribution may be varied to obtain high pressure rise. Two rotors, one with approximately uniform and one with solid-body downstream tangential-velocity distributions, were designed and tested at the design blade angle" (p. 1).

"It is shown how Schrenk's empirical method of estimating the lift distribution over straight wings can be adapted to swept wings by replacing the elliptical distribution by a new "ideal" distribution which varies with sweep.The application of the method is discussed in detail and several comparisons are made to show the agreement of the proposed method with more rigorous ones. It is shown how first-order compressibility corrections applicable to subcritical speeds may be included in this method" (p. 1).

"A Douglas C-74 airplane, during a test dive at about 0.525 Mach number, experienced uncontrollable longitudinal oscillations sufficient to cause shedding of the outer wing panels and the subsequent crash of the airplane. Tests of a section of the horizontal tail plane from a C-74 airplane were conducted in the Ames 16-foot high-speed wind tunnel to investigate the possibility of the tail as a contributing factor to the accident. The results of the investigations of fabric-covered elevators in various conditions of surface deformation are presented in this report" (p. 1).

Wind tunnel tests haved been made at low speed to various small-scale models of swept-back, swept-forward, and yawed wings. Tests covered changes in aspect ratio, taper ratio, and tip shape.

"A theoretical analysis of the cross-sectional temperature distribution of a water-cooled turbine blade was made using the relaxation method to solve the differential equation derived from the analysis. The analysis was applied to specific turbine blade and the studies icluded investigations of the accuracy of simple methods to determine the temperature distribution along the mean line of the rear part of the blade, of the possible effect of varying the perimetric distribution of the hot gas-to -metal heat transfer coefficient, and of the effect of changing the thermal conductivity of the blade metal for a constant cross sectional area blade with two quarter inch diameter coolant passages" (p. 1).

From Summary: "Tests of a 1/7 size model of the Grumman XJR2F-1 amphibian were made in Langley tank no.1 to examine the landing behavior in rough water and to measure the normal and angular accelerations experienced by the model during these landings. All landings were made normal to the direction of wave advance, a condition assumed to produce the greatest accelerations. Wave heights of 4.4 and 8.0 inches (2.5 and 4.7 ft, full size) were used in the tests and the wave lengths were varied between 10 and 50 feet (70 and 350 ft, full size)."

In accordance with a request of the Bureau of Aeronautics, Navy Department, tests were performed in the Langley 20-foot free-spinning tunnel to determine the spin and recovery characteristics of a 1/24 scale model of the Grumman XTB3F-1 airplane. The airplane is a two-place, midwing torpedo bomber equipped with a tractor propeller and an auxiliary jet engine. The effect of control setting and movement on the erect and inverted spin and recovery characteristics of the model were determined for the normal loading.

"An analysis has been made of the lift control effectiveness of a 20-percent-chord plain trailing-edge flap on the NACA 65-210 airfoil section from section lift-coefficient data obtained at Mach numbers from 0.3 to 0.875. In addition, the effectiveness of the plain flap as a lift-control device has been compared with the corresponding effectiveness of both a spoiler and a dive-recovery flap on the NACA 65-210 airfoil section. The analysis indicates that the plain trailing-edge flap employed on the 10-percent-thick airfoil at Mach numbers as high as 0.875 retains at least 50-percent of its low-speed lift-control effectiveness, and is sufficiently effective in lateral control application, assuming a rigid wing, to provide adequate airplane rolling characteristics" (p. 1).