This investigation was carried out at the request of the National Advisory Committee for Aeronautics and comprises an outline of historical developments and theoretical principles, together with a discussion of expedients for making the most effective use of existing diaphragms actuated by the hydrostatic pressure form an essential element of a great variety instruments for aeronautic and other technical purposes. The various physical data needed as a foundation for rational methods of diaphragm design have not, however, been available hitherto except in the most fragmentary form.

This lecture deals with four main subjects: methods of studying air resistance, experimental aerodynamics, propellers and stability of airplanes.

In soaring flight, ascending air currents are utilized and the interesting question is raised whether there are such currents which extend to any considerable distance and which can be utilized practically.

The plans for the wind tunnel at Issey-les-Moulineaux are discussed in relation to concerns about the Law of Similitude and propeller speed.

Memorandum presenting the rules and regulations of the Endurance Contest of Aviation Engines, which was put on by the Aero Club of France. A description of the rules regarding the aircraft in competition, the characteristics of the tests that were conducted, and information regarding classification of the aircraft is provided.

Corresponding to practical requirements, this carburetor (especially the smaller sizes) may be regarded as the smallest form of a float carburetor and is adapted for use with all small engines, including auxiliary bicycle and similar engines.

Memorandum describing the rules and regulations of the 1923 Rhön Soaring-Flight Contest. The requirements of the aircraft, pilot and competitor requirements, and prizes are provided.

The volatile fuel of the high-speed internal combustion engine has, in the past, consisted almost exclusively of the lighter distillates from crude petroleum. Alternative and supplementary fuels are discussed such as: tetraline, dekalin, alcohol, cyclo-hexenes.

Memorandum presenting the rules and regulations of the Fokker Soaring Flight Contest, which occurred over the water and over level land.

An historical sketch of the laboratories of the Technical Section is provided. A breakdown of the different departments and their specialties is also listed.

A flexible metal joint used for connecting fuel lines is investigated and methods for assembly are included.

The aim of this article is to present, in broad outline, a scientific method for solving the problem, "Wood or Metal." It will be shown that structural methods have by no means reached their final perfection. The strength of the different materials is discussed as well as different construction methods.

This report endeavors to show the possibility of determining the rate of acceleration and the advantage of having such an accelerometer in addition to other aviation instruments. Most of the discussions concern balloons.

"It is proposed to analyze the advantages and disadvantages of large fixed air-cooled radial engines and to explain how the problems have been solved by the Bristol Aeroplane Company" (p. 1).

The causes of error in experiments conducted in wind tunnel tests are given and the value of in-flight tests are promoted. The four main causes explored include neglect of the laws of dynamic similitude, interference between the support and the model, nature of the air stream, and the influence of the walls of the tunnel.

Report discussing a demonstration was given within the last few days at the British Museum by Mr. J. W. Gordon, author of "Generalized Linear Perspective" (Constable and Co.), a work describing a newly-worked-out system by which photographs can be made available for the purpose of exactly recording the dimensions of the objects photographed even when the objects themselves are presented foreshortened in the photograph.

The "AM" cock was designed specially for gasoline pipes on vehicles using internal combustion engines (airplanes, airships, automobiles, tractors, battle "tanks", boats, etc.). The report descirbes the functioning and construction of the device.

Static soaring flight has hitherto been accomplished by means of two sources of energy: ascending air currents in the vicinity of obstacles and those produced by unequal heating. The latter has not yet been practically tested in soaring flight.

The physical resistance of passengers in establishing an upper limit to the strength of airplane cells is examined and arguments and experiments are discussed.

During a flight with a Van Berkel W. B. seaplane it was observed that the wing could perform violent oscillations. A theoretical and experimental investigation led to the conclusion, that in some cases an unstable oscillation of the wing-aileron system under the influence of the elastic and aerodynamic forces is possible without further external causes.

This report presents a recapitulation of air traffic in France and her colonies as well as a discussion of the subsidies provided by the government.

The resistance of water, even at low speeds, may be such as to render it impossible to take off. For this type of aircraft, it is therefore especially important to determine the take-off characteristics. A new and simple graphical method is given and appears to be the only one for the complete solution of the problem.

This report tries to solve the problem of supplying the engine cylinders with a mixture of fuel and air in the right ratio to obtain the greatest power from the engine with the least consumption of fuel.

The "Turkey Buzzard" is a semi-internally braced monoplane (Fig. 1). The wing is placed above the fuselage for two important aerodynamical reasons: first, because this position minimizes the mutual interference between the wing and the fuselage, and, second, useful lifting surface is utilized with the wing passing over the fuselage instead of through it.