This note investigates the effect of high altitude or low atmospheric pressure upon the operation of an engine and the effect of the low pressure and lack of oxygen and of the very low temperatures upon the pilot and upon the performance of the airplane itself.

This report is the second of a series of four on propeller design, and describes the method used to extend the data obtained from tests on a family of thirteen model propellers to include all propellers of the same form likely to be met in practice. This necessitates the development of a method of propeller analysis which when used to calculate the powers and efficiencies gives results which check the tests throughout their range.

"The employment of steam power plants in aircraft has been frequently proposed. Arguments pro and con have appeared in many journals. It is the purpose of this paper to make a brief analysis of the proposal from the broad general viewpoint of aircraft power plants. Any such analysis may be general or detailed" (p. 1).

This report records observations and recommendations resulting from an inspection trip to representative aircraft manufacturing establishments and repair stations. This inspection was made for the Navy Department and was specifically in reference to gluing practice at the various places visited. The period of the visits was between November 23, 1926 and February 16, 1927.

Several improvements that have been made on commercially available carbon-monoxide indicators to make them more suitable for aircraft use are described. These improvements include an automatic flow regulator, which permits the use of a simplified instrument on aircraft where a source of suction is available, and a more reliable alarm attachment. A field method for testing instruments on standard samples of carbon monoxide is described. Performance data and instructions in operation and maintenance are given.

From Introduction: "The possibilities of the jump take-off have been established by some full-scale experiments. It is the purpose of this paper to study the factors that govern the jump take-off in its simplest form and to present the results of model tests in which the effect of differences in the rotor parameters was determined."

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 …

The gyroscopic instruments commonly used in instrument flying in the United States are the turn indicator, the directional gyro, the gyromagnetic compass, the gyroscopic horizon, and the automatic pilot. These instruments are described. Performance data and the method of testing in the laboratory are given for the turn indicator, the directional gyro, and the gyroscopic horizon. Apparatus for driving the instruments is discussed.

"The effect of restraint in pitching introduced by an automatic pilot upon the longitudinal stability of an airplane has been studied. Customary simplifying assumptions have been made in setting down the equations of motion, and the results of computations based on the simplified equations are presented to show the effect of an automatic pilot installed in an airplane of known dimensions and characteristics. The equations developed have been applied by making calculations for a Clark biplane and a Fairchild 22 monoplane" (p. 1).

"An investigation of three methods for the prevention and the removal of ice on an airplane windshield has been completed. The methods were: electric heating; hot-air heating; and an alcohol-dispensing, rotating wiper blade. The results showed that vision through the airplane windshield could be maintained during severe icing conditions by the use of heat" (p. 1).

Note presenting testing of a simplified type of all-metal wing construction of 18-8, spot-welded except for skin attachment, by means of hydrostatic loading, the wing being proportioned to permit close representation of typical conditions by means of the waterhead. The results showed the possibility of eliminating almost all of the stiffeners from a stressed-skin wing, the possible reduction of weight in a lightly loaded wing and of substantial cost in the construction of any all-metal wing.

"The arrangement of the parts and the installation and control problems of the two-stage mechanically driven superchargers for aircraft engines are discussed. Unless an entirely new form of supercharging is developed, there will be a definite need for a two-stage centrifugal supercharger. It is shown that the two-stage mechanically driven supercharger itself is a comparatively simple device; the complications arise from the addition of inter-coolers and controls" (p. 1).

Investigations of strengths of hot wires at high velocities were conducted with platinum, nickel, and tungsten at approximately 200 Degrees Celcius hot-wire temperature. The results appear to disqualify platinum for velocities approaching the sonic range; whereas nickel withstands sound velocity, and tungsten may be used for supersonic velocities under standard atmospheric conditions. Hot wires must be supported by rigid prolongs at high velocities to avoid wire breakage. Resting current measurements for constant temperature show agreement with King's relation.

From Summary: "A unit oil system and oil-weighing device designed for laboratory engine tests to permit the remote measurement of oil-flow rate and oil consumption is described. The system regulates the oil pressure and temperature and is closed to make possible the accurate measurement of blow-by gas. The oil is weighed by a self-contained diaphragm and pilot-valve assembly, which uses compressed air as the transmitting medium. Several of those unit systems have given satisfactory service for more than a year."

Report presenting a survey of the technical information contained in the literature on the subject of lubrication, friction, and wear of aircraft engine piston rings.

Note presenting an instrument that measures small absolute humidity changes by photoelectric examination of the 9440 angstrom units absorption band of water vapor. The instrument consists of a small source of light which sends its radiation over an air path of less than 1.5 meters to a dispersing system.

Report presenting an investigation regarding the strengths of bonds between different chemical types of adhesives and adherends. Some of the topics explored include the theoretical aspects of adhesion and properties of adhesively bonded structures.

A summary is given of information on atmospheric electrical discharges to aircraft and associated meteorological conditions. Information is given that is designed to give a fairly comprehensive view of the underlying principles of meteorology and atmospheric electricity. Of special interest to pilots are lists of procedures of flight conduct and aircraft maintenance recommended foe avoiding or minimizing the hazards of disruptive electrical discharges and other severe conditions near thunderstorms.

From Introduction: "The present paper has been prepared to give the results of the analysis of the V-G records obtained from three Boeing S-307 airplanes operating in Caribbean region and the northern part of South America during the period from 1940 to 1944."

From Introduction: "The present report is the second prepared to give the results of an analysis of V-G data from commercial transport airplanes. The present report is concerned with an analysis of data obtained with Douglas DC-3 airplanes flying over three transcontinental routes in the United States."

The infrared spectra of spiropentane, methylenecyclobutane, and 2-methyl-1-butene were measured in the region from 3 to 14 microns with a rock salt prism spectrometer of medium dispersion. The pure samples were prepared at the NACA Cleveland Laboratory. The vapors of these three C5 hydrocarbons were investigated at room temperature and at pressures in the range from 80 to 300 millimeters of mercury absolute in a 10-centimeter cell. The spectra were compared with each other and with Ramon spectra for the same compounds.

Note presenting the development of a continuous-indicating dew-point meter that automatically maintains a mirror surface at the dew point. The instrument was found to have an average accuracy of 1 degrees Fahrenheit over the range of 75 to -45 degrees. The accuracy of the instrument is uncertain at temperatures below 32 degrees Fahrenheit by the difference in vapor-solid and vapor-liquid equilibrium temperatures.

Note presenting an investigation conducted on a full-scale air-cooled cylinder in order to establish an effective means of maintaining maximum-economy spark timing with varying engine operating conditions. Variable fuel-air ratio runs were conducted in which relations were determined between the spark timing and basic factors in engine operation, flame-front travel, and cylinder pressure rise. An instrument for controlling spark timing was developed that automatically maintained maximum-economy spark timing with varying engine operating conditions.

Note presenting an investigation of the icing characteristics and means of ice protection of a typical radial-engine cooling-fan installation. The investigation was made at various icing and performance conditions in the icing research tunnel of the NACA Cleveland laboratory. The icing of the unprotected cooling-fan installation was found to present a serious operation problem.