The comparison of model tests in flight can be based on the result of such measurements. They are very important from the aerodynamical point of view, as they lead to useful conclusions regarding the behavior of the wing, its best shape and the conformity of theoretical and actual flow. Although there still remains a certain prejudice against such measurements, I have still attempted to make these comparative tests in order to inspire confidence in their reliability.

The author's first experiments with a glider on flight characteristics demonstrated that an accurate flight-path measurement would enable determination of the polar diagram from a gliding flight. Since then he has endeavored to obtain accurate flight measurements by means of kinetograph (motion-picture camera). Different methods of accomplishing this are presented.

Different types of coatings to protect duralumin from corrosion are discussed. Plating, etching, brushing, coloring, painting and varnishing are all investigated.

Different methods for increasing the efficiency of diesel engines are presented and some new designs are given.

Memorandum presenting a review of some of the German gliders produced from 1920-1923. The designs, flight characteristics, and descriptions of successful flights are provided.

The building and flying of a glider is possible for anyone who can use a few basic tools. This report presents some plans and techniques for building your own glider.

Aileron calculations have hitherto given greatly differing results according to different authors. It seems to be the general opinion that it is only necessary to give the ailerons such dimensions that the airplane can maneuver well, that the stresses they must undergo are relatively small, and that they are strong enough if their framework is of the order of strength as the wings to which they are attached. This article will show that the problem is really quite complex and that it should receive more attention.

The structural details such as wings, fuselage, landing gear, and steering organs of German gliders are detailed in this report.

In the closer investigation of the results obtained from a wing model with a rotary cylinder mounted in its leading edge (NACA TM's 307 and 354), the velocity distribution in the vicinity of the surface of the model was determined by a hot-wire anemometer. The results confirmed the belief that the rotary cylinder had considerable effect on the air flow, but demonstrated the fact that the direct influence of the cylinder is confined to a very thin layer in immediate proximity to the surface.

The calculations in this paper afford an approximate solution of the static stability. A derivation of the formulas for moment coefficient of a wing, moment coefficient of elevator, and the total moment of the combined wing and elevator and the moment coefficient with reference to the center of gravity are provided.

Report presenting some information and potential areas of study of turbulent flow and turbulence.

This report concerns, first, the determination of the lift of a wing which is situated in a curvilinear flow; and second, to calculate the curvature which one wing of a biplane produces in the vicinity of the other.

In order to clear up the matter ( In the Spanish report it was stated that the reference surface for the calculation of the coefficients c(sub a) and c(sub w) was the area of all four wings, instead of a single wing), the model of a windwill airplane was tested in the Gottingen wind tunnel.

Report investigating some characteristics of aircraft stall, including the following: Is the danger of stalling necessarily inherent in the airplane in its present form and structure, or can it be diminished or eliminated by suitable means? Do we possess such means or devices and how must they operate?

When certain light aluminum alloys are heat-treated, quenched and aged, there is considerable improvement in their tensile properties. This paper presents different methods of accomplishing these heat treatments.

Recent accidents, which were the result of structural failure in flight, revealed the necessity of a closer examination of the conditions under which the resistance of airplane structures may be calculated.

Memorandum presenting a description of the structural details of airplanes presented at the 1926 Paris Aero Salon.

Ackeret began systematic polar measurements on Joukowsky wing sections, which were occasionally conducted in the wind tunnel. Under these conditions a considerable number of wing sections were tested during the last four years and the tests are now more or less concluded.

"Further progress toward the satisfactory solution of the difficult problem of the distribution and atomization of the injected fuel was made by extensive experimentation with various fuel valves, nozzles, and atomizing devices. Valuable information was also obtained through numerous experimental researches on the combustion of oils and the manner of introducing the combustion air into the cylinder, as well as on the physical processes of atomization, the determination of the size of drops, etc. These researches led to the conclusion that it is possible, even without producing great turbulence in the combustion chamber and at moderate pump pressure, if the degree of atomization and the penetrative power of the fuel jet are adapted to the shape of the combustion chamber and to the dimensions of the cylinder" (p. 1).

Ignition-chamber engines and their fuel injection systems are investigated. Specific details are provided for fuel-injection nozzles and fuel pumps are provided.

Different methods of determining the size of fuel droplets in the atomization process are presented. The distribution of those drops is also presented in graphic form.

Different engines are tested to determine their efficiencies in burning fuel. Fuel injection and ignition chamber engines are also discussed.

Gas and electric welding of duralumin are discussed. Some of the elements that go into determining a successful weld and inspecting for faults are also described.

"At the suggestion of Professor Von Karman, I have made a few theoretical investigations of the mutual reaction of the wings and body of an airplane. There was assumed as the basis of my calculations, a strongly idealized body shape, namely, a cylinder extended to infinity at both ends and having its axis parallel to the direction of motion of the airplane. The results are to be regarded as rough approximations for a long airplane body and also for an airship with fins. In my calculations, I have considered only a monoplane in which the axis of the wing is rectilinear" (p. 1).