In order to determine the efficiency of a propeller as accurately as possible, its revolution speed, thrust and power absorbed must be measured during flight. Unfortunately, these measurements can only be made with very complicated equipment. To surmount this problem the testers contented themselves with approximate results obtainable in two or three hours of flight.

The author discusses the safety record of airships in light of the accidents with the Roma and the ZR2.

Where, in the following report, mention is made of fatigue, it always refers to the weakening of the material produced by rapidly changing stresses below the point of elasticity. The alternating stress was obtained by a test bar which was held at one end and subjected to rotation. Most of the tests were conducted on connecting rods.

Any one endeavoring to solve the problem of soaring flight is confronted not only by structural difficulties, but also by the often far more difficult aerodynamic problem of flight properties and efficiency, which can only be determined by experimenting with the finished glider. The report primarily considers open-air experiments with glider models and some specific elements of gliders that have been studied using these experiments.

A design for a wind vane is presented and various applications are discussed. The equations that can be used to calculate effects on the aircraft using the vane and control assistance that can be provided using the wind vane are provided.

It is hardly possible for the most imaginative aeronautical enthusiast to look forward to a time when the airplane will have reached the dimensions commensurate with those already attained by the airship.

This article discusses two areas of international air travel, namely, passports and customs, as well as smuggling.

From Introduction: "In the following discussion, a knowledge of the theoretical principles of airplane construction is assumed, as presented in detail by Vogt and Lippisch in Nos. 7 and 10-19 of the 1919 volume of this publication. A few quantities will however be otherwise designated, in accordance with the Gottingen symbols."

The difference between aircraft for commercial and wartime uses is delineated, but the interchangability between the two is also discussed. Airships in both roles are also presented.

The development of the parachute is presented as well as the future possibilities. The primary topics covered include allowing for wind in design, the parachutes used at balloon exhibitions, parachute use in the war, the delayed-opening type of parachute, and the use of parachutes on commercial airplanes.

This report presents a study of an instrument that can warn the pilot of the turning of his airplane. This instrument must satisfy three conditions: 1) It must give useful indication immediately from take-off; 2) The indications must be instantaneous and require no exertion by the pilot; 3) The indicator must be sensitive only to changes of orientation in the horizontal plane. Different solutions are presented such as a gyroscope driven by the suction of a Venturi tube.

"A transverse test was made of the wood sample using a 5,000 pound Olsen testing machine, the deflection under load being measured by means of a Wissler dial. The results of the transverse test are given and the stress-strain curve is attached" (p. 1).

Different aspects of aircraft regulation are discussed such as: protecting the public; the restriction of flights over crowds; regulations of wing-walkers.

This report presents examples of different methods of comparing aircraft mathematically. In the example given a biplane and monoplane are compared as to what speed one type of airplane is better at than another.

"The Coutinho-Sacadura course corrector is an instrument with which, knowing the angles of drift of two different courses, we may determine by simple readings: a) direction and velocity of wind; b) correction to be made in course followed by compass, in order to fly in a given direction; c) ground-speed of aircraft, the resultant of its air speed and the velocity of the wind" (p. 1).

Unfortunately the problem of laying out an air route has been approached by all who give it consideration as one of the hardest tasks in the world. Whereas, as a matter of fact, a very serviceable air route can be laid out with an absolute minimum of ground work.

Different illumination systems for landing fields are presented which include fixed beacons, signal guns, and light patterns such as T's and crosses. Some of the advantages and disadvantages for each of the lighting patterns are provided.

The wing strain meter enables a pilot to know the strain on lifting surfaces and to warn him of the safe limits which may not be exceeded. In wing strain the most important factors are the force of gravity and the force of lift which gives the measure of the sustaining force, and their components which are perpendicular to the lifting surfaces. This reports methods for using the wing strain meter.

The present report will treat only the smallest airplanes equipped with engines. The two types discussed are those airplanes with the smallest dimensions, and those that have the smallest power requirements.

"The end of the war saw every belligerent with vast stocks of aircraft and aircraft supplies in all stages of usefulness, much of the material being absolutely new. The question of the best method of getting rid of this accumulation is one which has been agitating those responsible for its disposal for more than three years now, but no wholly satisfactory solution has yet been reached" (p. 1).

The decrease in air traffic on the London-Paris route is examined and possible solutions are presented.

On an airplane, the safeguards adopted may be divided into three classes, those intended to prevent a fire from getting started, those intended to put it out if it does get under way, and, finally, those designed to limit the damage which a fire can do. Some of the fire-related elements discussed include protecting the gasoline, fire extinguishers, a flame-tight bulkhead, and airship hazards.

"The forces acting on the blades of a propeller proceed from the mass of the propeller and the resistance of the surrounding medium. The magnitude, direction and point of application of the resultant to the propeller blade is of prime importance for the strength calculation. Since it was obviously impracticable to bring any kind of testing device near the revolving propeller, not so much on account of the element of danger as on account of the resulting considerable disturbance of the air flow, the deflection in both cases was photographically recorded and subsequently measured at leisure" (p. 1).

In airplane construction generally one finds an almost exclusive use of wing tips that are practically square end but occasionally those with large rounded tips. For use as a cantilever wing, however, a wing with pointed tips may contain valuable aerodynamic advantages.