Note presenting an examination of the available information on the hail phenomenon affecting aircraft in flight. Some of the components in the report include: a digest of literature on the physical properties and formation of hail, a survey of the affect of hail on aircraft in flight from 57 cases of aircraft damaged by hail, information on hail for the benefit of pilots, forecasters, and ground personnel, and an annotated bibliography of articles about hail.

Report presenting the technical reports of the National Advisory Committee for Aeronautics from 1953. The report is divided into the technical activities of NACA, the committee organization and membership, and the financial report. The technical reports are divided into a general overview of NACA, unitary wind tunnels, aerodynamic research, power plants for aircraft, aircraft construction, operating problems, and reserch publications.

"In accordance with act of Congress, approved March 3, 1915, as amended (U.S.C., title 50, .sw 151), which established the National Advisory Committee for Aeronautics, the Committee submits its Forty-fourth Annual Report for the fiscal year 1958. This is the Committee's final report to the Congress. The National Aeronautics and Space Act of 1958 (Public Law 85-568) provides in section 301 that the NACA "shall cease to exist" and "all functions, powers, duties, and obligations, and all real and personal property, personnel (other than members of the Committee), funds, and records of the NACA shall be transferred to the National Aeronautics and Space Administration" (p. ix).

Note presenting a study of the stress measurements by means of the x-ray diffraction method, which have found considerable application in solving both commercial and laboratory problems. Two problems related to x-ray diffraction are studied and a literature review is conducted.

The report gives, rather briefly, in part one an introduction to hydrodynamics which is designed to give those who have not yet been actively concerned with this science such a grasp of the theoretical underlying principles that they can follow the subsequent developments. In part two there follows a separate discussion of the different questions to be considered, in which the theory of aerofoils claims the greatest portion of the space. The last part is devoted to the application of the aerofoil theory to screw propellers. A table giving the most important quantities is at the end of the report. A short reference list of the literature on the subject and also a table of contents are added.

Report presenting a study of the literature data on the solubility of water in hydrocarbons, which includes information about the log of solubility, critical solution temperature, and ratios that may affect solubility are provided. An equation is presented and applied to a few petroleum fractions ranging from gasoline to lubricating oil, and a comparison of calculated and experimental solubilities is provided.

Discussed here are results already achieved with sonic altimeters in light of the theoretical possibilities of such instruments. From the information gained in this investigation, a procedure is outlined to determine whether or not a further development program is justified by the value of the sonic altimeter as an aircraft instrument. The information available in the literature is reviewed and condensed into a summary of sonic altimeter developments. Various methods of receiving the echo and timing the interval between the signal and the echo are considered. A theoretical discussion is given of sonic altimeter errors due to uncertainties in timing, variations in sound velocity, aircraft speed, location of the sending and receiving units, and inclinations of the flight path with respect to the ground surface. Plots are included which summarize the results in each case. An analysis is given of the effect of an inclined flight path on the frequency of the echo. A brief study of the acoustical phases of the sonic altimeter problem is carried through. The results of this analysis are used to predict approximately the maximum operating altitudes of a reasonably designed sonic altimeter under very good and very bad conditions. A final comparison is made …

From Summary: "A literature survey was conducted to determine the relation between aircraft ignition sources and inflammables. Available literature applicable to the problem of aircraft fire hazards is analyzed and discussed. Data pertaining to the effect of many variables on ignition temperatures, minimum ignition pressures, minimum spark-ignition energies of inflammables, quenching distances of electrode configurations, and size of openings through which flame will not propagate are presented and discussed. Ignition temperatures and limits of inflammability of gasoline in air in different test environments, and the minimum ignition pressures and minimum size of opening for flame propagation in gasoline-air mixtures are included; inerting of gasoline-air mixtures is discussed."

Note presenting a review of the literature on the sonic studies of the problem of the excitation of molecular vibrations by collision. The theory on which the interpretation of almost all the sonic work has been based is discussed rather qualitatively in some detail. Results concerning techniques, principal experimental programs, and an interpretation of the results are provided.

Report presenting an experimental method of measuring both the arithmetic mean velocity and the instantaneous velocity of pulsating flow and with the instruments developed for this purpose. A circuit for a hot-wire anemometer usable for fluctuating flow is described.

Note presenting tests on the use of x-ray diffraction methods for determining surface stress distributions in notched tensile bars and in the vicinity of a welded joint in aircraft steel tubing. Data on the effects of stress and degree of notching on the principal stresses and stress-concentration factors for flat notched tensile-test specimens were obtained.

"About 500 additional references pertaining to hydrodynamic design of seaplanes have been compiled, and the information is presented in the form of abstracts classified under six main headings:GENERAL INFORMATION, HYDROSTATICS, HYDRODYNAMICS, AERODYNAMICS, OPERATION, and RESEARCH. The compilation is an extension of NACA RM No. L6I13, entitled "Abstracts Pertaining to Seaplanes," by Jerold M. Bidwell and Douglas A. King. An author index and a subject index are included" (p. 1).

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.

Compendium presenting a comprehensive integration of available aerodynamic design information on axial-flow compressors. The subjects of the first volume of this investigation are objectives and scope, compressor design requirements, compressor design system, potential flow in two-dimensional cascades, and viscous flow in two-dimensional cascades.

Report presenting information that extends the range of existing fundamental friction knowledge to include sliding velocities encountered in rolling-contact bearings and reduction gears of aircraft power plants. Experiments were conducted with a kinetic-friction apparatus consisting basically of an elastically restrained spherical rider sliding on a dry or lubricated rotating disk. The results indicate that the kinetic friction decreases with sliding speed for dry and for some boundary-lubricated surfaces at high sliding speeds.

Report discussing about 400 references pertaining to the hydrodynamic design of seaplanes have been compiled, and the information is presented in the form of abstracts classified under six main headings.

Note presenting the body of knowledge that has been accumulated in the field of noise reduction in aircraft. Special attention is paid to effective soundproofing schemes.

Report presenting testing in the variable density wind tunnel on two airship models known as the NPL Standardization Models, long and short. The resistance or shape coefficients were determined for each model through a range of Reynolds numbers. Further work is found to be necessary in the standardization of wind tunnels.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, summaries of the committee's activities and research accomplished, bibliographies, and financial report.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, summaries of the committee's activities and research accomplished, bibliographies, and financial report.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, expenditures, and problems.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, and expenditures.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, summaries of the committee's activities and research accomplished, bibliographies, and financial report.

Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, bibliographies, and financial report.