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 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 report considers the effect on engines of the varying types of fuels now in use. Different types of fuels are examined and the influence of physical characteristics are considered.

Since the war there has been a considerable advance in knowledge on the subject of the airfoil and its behavior. The theory is now sufficiently advanced to make it possible to predict and to calculate certain results which previously could only be attained by direct experiment. The vortex theory receives special attention.

Report discussing tires, steel springs, hydraulic shock absorbers, and axle travel are all examined in relation to absorbing landing shocks.

This report is a comprehensive study of birds and how their shapes have been molded by the resistance of the air. 500 species of birds were studied and nearly 30,000 ratios calculated. The author makes a distinction between flapping and soaring flight.

"It is now well known that all nonrigid airships constructed at the present time have bow stiffeners consisting of battens curved to the form of the envelope and designed to hold the nose of the ship in its true form despite the very large pressure which exists at the extreme forward point. The effect of the stiffeners is to reduce considerably the apparent pressure which has to be maintained inside the envelope in order to prevent the nose from caving in" (p. 1).

N.A.C.A. has developed an instrument which makes a continuous record of the angular position of the control surfaces of an airplane, not only in steady flight but during acrobatics as well. It has proven useful in researches into stability and controllability, and from records obtained from it many otherwise obscure details of piloting technique have been available for the instruction of pilots, from novices to seasoned experts.

"The conventional airplane strut fails by buckling. The first signs of failure usually are compression cracks on the concave side of bending. It would therefore appear that if an initial tension could be introduced in the outside fibers, this tension would have to be relieved before the compression load could make itself felt" (p. 1).

The following article shows that the phenomena of climbing flight can be determined with sufficient accuracy and represented very clearly, for all flight positions, by means of the thrust diagrams. This method has often given good results.

Note presenting some comparative performances of new types of airplanes under the same conditions. The airplanes were compared with some that are already in use and give an accurate idea of the progress shown in the new types.

"These regulations, approved by the Under Secretary of State for Aeronautics, in a ministerial decree 1124/2a, Feb. 19, 1923, cancels the regulations of Aug. 31, 1920, and supplements the decree of Aug. 14, 1920, fixing the conditions under which certificates of airworthiness may be issued,in conformity with Article 5 of said decree" (p. 1).

This note contains photos and descriptions of airplane flight apparatus for use in conjunction with a recording galvanometer. In measuring the angle of attack a variable resistance is used, being controlled by a vane in the airstream. Thus it is only necessary to measure the change of resistance.