In summing up it may be said that the hydrodynamic theories are best confirmed by experimental results for bodies with small resistance or drag and can accordingly be used in place of experimental tests.

Different causes of airplane engine vibration are given as well as devices to measure vibration.

Report discussing the use of magnetic fields and wire to navigate aircraft in conditions of poor visibility is presented. This field may be considered to be derived from a double lemniscate, considered in the particular case where the origin is a double point formed from the magnetic field of the slack wire, from the field produced by the return currents and from the field due to the currents induced in the conducting mass. These fields are dephased in two ways, one in the direction of the wire, the other in a direction perpendicular to it.

Report presenting a description of the aerodynamics laboratory of the Vienna Technical High School. The main focus of this report is detailing some of the accomplishments that the laboratory has made.

Necessity of adopting for all aviation fields, civil or military, a single system of markers for giving the direction for starting and landing (with an automatic indicator of the direction of the wind) and of indicating the good part of the field.

The observation that airplane fabrics, after long use, lose their original strength, caused the German Experimental Institute for Aviation to carry out a series of experiments on the effect of weathering on the cloth covering of airplane wings and fuselages.

Report discussing the origin of air traffic dates from the war. The important development of aeronautic industries and the progress made in recent years, under the impelling force of circumstances, rendered it possible, after the close of hostilities, to consider the practical utilization of this new means of economic expansion.

If, by some means, a steady state of motion of a perfect fluid were established in an ideal wind tunnel, there would be no losses, and the motion would persist indefinitely. In the actual tunnel, the function of the motor-fan group is overcome by the total loss of head in the tube due to friction and eddies.

We see with great satisfaction that Bagnulo's studies and experiments on his high-speed, heavy-fuel engines, promise to solve not only the general problem of economical power and hence of thermal efficiency, but also all other special problems, of weight and space, and, what is still more important, range of error.

The future of aerial photography is examined with special reference to corporate uses.

The problem of insuring the emerging commercial aeronautic industry is detailed. The author also motes that a complete solution cannot be obtained until the necessary statistics are compiled.

The evolution of construction techniques and the use of metal in wings is presented. Drag is discussed along with the fuselage and tail. The interaction of these parts is also investigated.

In the present treatise, a convenient method will be indicated, which makes it possible to determine the polar curve of an airplane at short distances from the ground by a simple short calculation, when the polar curve is known for flight in unlimited space.

To sum up, Professor Joukowski's theory of supporting wings renders it possible to calculate the coefficient of lift in terms of the angle of attack, and Prandtl's coefficient of induced drag and the correction of the angle of attack in terms of the disposition and aspect ratio of the wings.

In the following report, we will first draw some conclusions of purely theoretical interest, from the general equations of motion. At the end, we will consider the motion of an airplane, with the engine dead and with the assumption that the angle of attack remains constant. Thus we arrive at a simple result, which can be rendered practically utilizable for determining the trajectory of an airplane descending at a constant steering angle.

Different maps and scales are discussed with particular emphasis on their use in aviation. The author makes the observation that current navigation methods are slow and dangerous and should be replaced by scientific methods of navigation based on loxodromy and the use of the compass.

At the request of the N.A.C.A. the "Universal Propeller" was operated and explained by the inventor, Mr. Spencer Heath, for the purpose of demonstrating the following features of design: 1) Elimination of continuously running gears, collars or bearings in the pitch control mechanism; 2) The use of engine power in place of manual labor in changing blade angle; 3) The absence of any structural limitation to the range of blade angles available and the possibility of limiting the blade travel between any two predetermined extreme positions; 4) Continuous indication on the instrument board of the blade position; 5) Automatic throttling of the engine while the propeller is passing through the position of neutral pitch.

The organization of a meteorological service for an air route involves the solution of two distinct problems: distribution and grouping of meteorological stations and communications. Experience gained in the establishment of two lines, Paris-Warsaw and Constantinople-Bucharest enables us to establish certain principles, which may be of interest to note here.

This report provides a list of landing locations for seaplanes on the Atlantic coast of the United States and the facilities and services located there.

If it is desired to record the pressure difference given a gauge, the manometer must answer the following conditions: 1) It must respond quickly so that all speed variations will be correctly recorded; 2) It must not be affected by rectilinear or curvelinear accelerations. Hence, movable parts must be counterbalanced. An instrument which met these criteria is discussed as well as details of construction.

Report presenting some topics related to safety in flight and the importance of having accurate statistics and information regarding aircraft problems and accidents. Some of the topics provided included perverted statistics, the British accident record, unregulated air traffic in America, and air mail in bad weather.

This report presents a listing of the many experiments in aerodynamics taking place at Cuatro Vientos. Some of the studies include: testing spheres, in order to determine coefficients; mechanical and chemical tests of materials; and various tests of propeller strength and flexibility.

This report presents a brief history of France's attempts to promulgate an internal air traffic law and then provides a draft of proposed national air traffic laws.

The ways in which the international and internal French air traffic accords interact with each other is outlined in this report. The principal questions covered by the present legislation are as follows: 1) Conditions of safety which must be fulfilled by aircraft; 2) Licenses for members of the crew; 3) Traffic rules to be observed by French and foreign aircraft.