The following report endeavors to show that aeromechanical experimentation has become an important aid to theory. Experiments can be tried with separate parts of airplanes or with models of whole airplanes, with propellers, and with anything else that comes into contact with moving air.
It has been less well understood that the induced drag (or, better said, the undesired increase in the induced drag as compared with the theoretical minimum calculated by Prandtl) plays a decisive role in the process of taking off and therefore in the requisite engine power. This paper seeks to clarify the induced drag.
The following examples do not take up the discussion of viewpoints to be heeded in determining the design of a framework for given external conditions. Rather they are methods for determining the forces in airplane fuselages and wings, though similar considerations are applied to certain simple cases of a different kind. The object of this treatise is to summarize and amplify these considerations from definite viewpoints.
This report presents an analysis of results of wind-tunnel tests conducted at the D.V.L. Values were determined for the effectiveness of all the controls at various angles of attack. The autorotation was studied by subjecting the rotating model to an air blast.
A nomogram is developed which renders it possible by drawing a few lines, to determine: the location of the center of gravity for zero wing and tail moments; the longitudinal dihedral angle; the tail coefficient F(sub h) iota/F(sub t). Moreover there is no difficulty in determining the magnitude of the restoring moment or of the unstable moment.
Report presenting an attempt to determine mathematically the buckling-strength curves of various centrally loaded light-metal tubes which exhibit conspicuous differences of behavior under compressive loads. For this purpose, Von Karman's method is used after adapting it to special conditions.
For aircraft engines the three principal operating conditions are idling speed, cruising speed, and diving with the engine stopped. In what follows, we will discuss a method which affords a good idea of the course of pressure for the above mentioned operating conditions. The pressures produced in the driving gear are of three kinds; namely, the pressure due to gases, the pressure due to the inertia of the rotating masses, and the pressure due to the inertia of the reciprocating masses.
In the foregoing remarks I have made an attempt to touch on some of the structural problems met with in cantilever wings, and dealt rather fully with a certain type of single-spar construction. The experimental test wing was a first attempt to demonstrate the principles of this departure from orthodox methods. The result was a wing both torsionally stiff and of light weight - lighter than a corresponding biplane construction.
"In an attempt to treat theoretically the effect of ailerons, difficulty arises because an aileron may begin at any point of the wing. Hence the question arises as to how the transition of the lift distribution proceeds at such a point, since the effect of the aileron (i.e., the moment generated about the longitudinal axis) depends largely on this distribution. In order to answer this question regarding the lift distribution during irregular variations in the angle of attack at first independently of other influences, especially those of the wing tips, we have taken as the basis of the following theoretical discussion a wing of infinite span and constant chord which exhibits at one point an irregular variation in the angle of attack" (p. 1).
Many treatises in regard to construction of airship sheds are lacking in data on air currents, for which reason this phase of the problem will be here thoroughly discussed in connection with the accompanying photographs of currents.
Memorandum presenting a description of the development of the mooring mast and how it contributes to the technique of landing large airships. Some of its fundamental requirements and how it can factor into safe landings are provided.
This report presents the results of tests on two-stroke-cycle Diesel engines to determine the efficiency of the crank case scavenging pump. It was determined that efficiencies were between 95 and 100%.
This report provides a description of an automatic control mechanism that consists of an automatic elevator control, aileron control, and a rudder control. Each automatic control can be independently switched on or off.
" The writer discusses the phenomena of expansion and compression which alternately take place in the cylinders of four-stroke engines during the induction process at a high mean piston speed due to the inertia and elasticity of the mixture in the intake pipe. The present paper is intended to demonstrate theoretically the existence of a most favorable pipe length for charging" (p. 1).
The ignition temperature, ignition lag, and ignition strength of simple and homogeneous fuels in combustion air of small oxygen content differ from what they are in air of greater oxygen content. In the case of small oxygen content, these fuels behave as if mixed unevenly. In the case of air with a definite oxygen content, the simple fuels have two ignition points, between which ignition takes place within a certain temperature range. The phenomena are explained by pyrogenous decomposition, comparison of the individual heat quantities, and the effect of the walls.
In practice the actual maximum stress is greater than the stress determined by the simple girder theory, which overestimates the bearing or supporting capacity of the flange. The fact is that the assumptions of the simple girder theory no longer hold true, since normal transverse and shearing stresses are engendered in the plane of the flange.
The present report deals with a series of tests made for the purpose of improving flow conditions about wings by applying the suction principle (increase of the lift coefficient and reduction of the drag about very thick wing sections). Though not conclusive, the report contains interesting results.
Various methods for preventing fires in airplanes are presented with most efforts centering around prevention of backfires, new engine and carburetor designs, as well as investigations on different types of fuels.
This part of the report presents a detailed examination of spark prevention, fire extinguishers, and fuel tank location and design. A continued program of investigations and research is also proposed.
The present article, which constitutes a continuation of the work of Von Baumhauer and Konig, will therefore be restricted to the fluttering of the tail surfaces and especially to oscillations of the horizontal empennage. This will also illustrate the characteristics of all other phenomena of fluttering.
The most essential phenomena of aircraft should be classified according to their origin and then measured. Information can thus be obtained in a quicker, cheaper, and more reliable way than otherwise would be possible.
In this report Handley Page construction techniques are shown such as: solid-drawn tubular duralumin spars are used in the stabilizer; plain channel sections are used extensively for minor components; and the manner of assembling them into a stabilizer compression strut is shown.
"Among the numerous thermodynamic and kinetic problems that have arisen in the application of the gaseous explosive reaction as a source of power in the internal combustion engine, the problem of the mode or way by which the transformation proceeds and the rate at which the heat energy is delivered to the working fluid became very early in the engine's development a problem of prime importance. The work of Becker here given is a notable extension of earlier investigations, because it covers the entire range of the explosive reaction in gases - normal detonation and burning" (p. i).
A continuation of a previous technical memorandum regarding impact waves and detonation. This particular report focuses on the applications to detonation under several different conditions, including variations in pressure.
The information obtained from flight tests in 1927-1928 covers chiefly the effect of the structural features of an airplane on its stability, controllability, maneuverability and spinning characteristics.
Memorandum presenting the mutual action of wing and fuselage, which greatly affects the construction of airplanes. A description of systematic wind-tunnel tests that were made to answer that question is provided. Other tests deal with the transition from fuselage to wing root, which, if inadequate on low-wing monoplanes, may become dangerous by causing the air flow to separate at the wing root.
In the numerical examples, we have considered an airplane landing in calm air in a fixed direction after crossing the border (with its obstacles) at a height of 30 m. Its stopping point is at a distance D from the obstacle, comprising: a distance D(sub 1) in regular gliding flight; a distance D(sub 2) in levelling off; a distance D(sub 3) in taxying on the ground. The calculations enable us to make out the following table, which gives an idea of the improvements to be expected in the use of various possible methods of braking in the air and on the ground.
Lautal is a refinable aluminum alloy which, unlike duralumin, contains no magnesium. According to the statements of the Lauta Works, lautal contains: aluminum, 94%; copper, 4%; silicon, 2%. The use of lautal as a construction material is discussed in relation to specific weight, production methods, and riveting tests.
In order to understand the numerical relations between the air velocity, temperature of the cylinder walls, heat dissipation, cylinder dimensions and type of construction an experimental plant was installed in the Siemens and Halske laboratory. The experimental cylinder was exposed to the air stream of a wind tunnel. The compression chamber was heated by an electrically heated oil bath kept constantly in motion by a stirrer. The wall temperatures were measured by thermocouples.
"Before undertaking a detailed description of an automatic-control mechanism, I will state briefly the fundamental conditions for such devices. These are: 1) it must be sensitive at one or more reference values; 2) it must stop the angular motions of the airplane not produced by the pilot; and 3) it must be possible to switch it off and on by a simple hand lever" (p. 1).
Memorandum describing the use of wing spars in metal aircraft. An overview of different types of spurs and testing of the spurs in aircraft are provided.
The present investigation relates to a box-type fuselage with sides consisting of thin smooth sheet metal, stiffened by longitudinal members riveted to the flanged channel-section bulkheads or transverse frames and to the semicircular corrugated corner stiffenings. The results obtained in this particular case can be applied to a great number of similar structures.
Memorandum exploring the concept that if fire safety is not to be acquired at the expense of the functioning reliability of the engine, we must try to burn fuels which are less inflammable at their temperature of utilization. A definition of temperature of utilization is explored and some examples for various types of fuels are given.
"The recent trial flights and acceptance tests of the Rohrbach "Romar," the largest seaplane in the world, have yielded results fully confirming the principles followed in its development. Its take-off weight of 19,000 kg, its beating the world record for raising the greatest useful load to 2000 m by almost 2500 kg and its remarkable showing in the seaworthiness tests are the results of intelligent researches, the guiding principles of which are briefly set forth in this article" (p. 1).
Report presenting some information on the gliders that participated in the 1928 Rhön soaring flight contest. Almost all of the gliders represented an improvement over gliders used in the previous years. A great increase in the skill of the glider pilots is also noted.
The present work investigates, on the basis of Prandtl's wing theory, the form of the lift distribution when the ailerons are deflected in opposite directions. An ideal fluid and a wing with a rectangular form are assumed. The moments must not cause any rotation of the wing or any deviation from the rectilinear motion.
"The present paper treats less of the effect of the union (of spars and ribs, namely, the reduction of the bending moment at the fixed ends of the spars) than of its influence on the torsional rigidity of the wing. The calculations are carried out for a two-spar wing of constant cross section, in which the ribs are replaced by a continuous member of constant rigidity" (p. 1).
This report presents a thermodynamic basis for rating heat engines. The production of work by a heat engine rests on the operation of supplying heat, under favorable conditions, to a working fluid and then taking it away.
The experiments here described were performed for the purpose of obtaining the essential facts concerning the distribution of the air force along the span. We did not follow, however, the time-consuming method of point-to-point measurements of the pressure distribution on the wing surfaces, but determined directly the moment of mean force about an axis passing through the middle of the span parallel to the direction of flight.
This paper calls attention to the desirability of expanding airplane building regulations to include proof of safety for cases of unsymmetrical loading, at least in the structural members which are thereby specially stressed. The flight cases involve increases of the customary load assumptions through rudder deflection and aileron deflection.
"It would appear that welds in some stainless steels, heat-treated in some practicable way, will probably be found to have all the resistance to corrosion that is required for aircraft. Certainly these structures are not subjected to the severe conditions that are found in chemical plants. This article should be considered as an outline of what can be done, not necessarily as instructions, which will enable anyone to obtain satisfactory results in commercial work" (p. 1).
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