National Advisory Committee for Aeronautics (NACA) - 1,298 Matching Results

Search Results

Vortices and the Related Principles of Hydrodynamics
Here, conceptions concerning vortices are illustrated by the simplest possible examples. Mathematical formulas and similar means of presentation, which, for the most part, do not help the understanding of persons not versed therein, have been avoided as much as possible. Instead, the author has endeavored to demonstrate the phenomena by means of simple geometrical and mechanical illustrations. For the sake of clarity, the author chiefly considers currents in one plane only, a situation that can be readily represented by diagrams. Some of the peculiarities of vortices in three dimensional flow are briefly discussed.
Dependence of Propeller Efficiency on Angle of Attack of Propeller Blade
In order to determine the maximum and the most favorable pitch for a propeller, it was found desirable to investigate the dependence of propeller efficiency on the angle of attack of the propeller blade. The results of a few experiments are given to show that propeller blades conduct themselves just like airplane wings with reference to the dependence of their efficiency on their angle of attack.
Effects of Varying the Relative Vertical Position of Wing and Fuselage
"The object of this series of experiments was to determine the influence of the relative vertical position of wing and fuselage on the efficiency of the wing. Since the longitudinal position of the wing can be varied but slightly with reference to the center of gravity in a normal airplane, it was kept constant in the experiments to be described and only the vertical position of the wing with reference to the fuselage was varied" (p. 1).
Ground Influence on Aerofoils
The question of ground influence on airplanes has recently attracted some attention in view of the claims made by certain designers that the landing speed of their airplanes is much decreased by an increase in lift coefficient due to the proximity of the ground in landing. The results of wind tunnel tests indicate that ground effect is not entirely beneficial. It decreases the landing speed and cushions the landing shock somewhat. However, it does so at the expense of an increased length of preliminary skimming over the ground.
A Mechanical Device for Illustrating Airplane Stability
An instrument is described which will illustrate completely in a qualitative sense the longitudinal stability characteristics of an airplane. The instrument is primarily of use for the lecture room, but it is hoped that ultimately it will be possible to obtain quantitative results from it.
Mutual Influence of Wings and Propeller
Report presenting an experiment consisting of an aerofoil and propeller in order to discover the mutual influence between the two components and variations in moment due to the propeller influence.
Aerial navigation : on the problem of guiding aircraft in a fog or by night when there is no visibility
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.
Aeronautic Instruments Section 8: Recent Developments and Outstanding Problems
This report is section VIII of a series of reports on aeronautic instruments. The preceding reports in this series have discussed in detail the various types of aeronautic instruments which have reached a state of practical development such that they have already found extensive use. It is the purpose of this paper to discuss briefly some of the more recent developments in the field of aeronautic instrument design and to suggest some of the outstanding problems awaiting solution.
Air forces, moments and damping on model of fleet airship Shenandoah
From Introduction: "To furnish data for the design of the fleet airship Shenandoah, a model was made and tested in the 8 by 8 foot wind tunnel for wind forces, moments, and damping, under conditions described in this report. The results are given for air of standard density. P=0.00237 slugs per cubic foot with vl/v correction, and with but a brief discussion of the aerodynamic design features of the airship."
Analysis of stresses in German airplanes
This report contains an account of the origin of the views and fundamental principles underlying the construction of German airplanes during the war. The report contains a detailed discussion of the aerodynamic principles and their use in determining the strength of airplanes, the analysis of the strength qualities of materials and in the construction, the calculated strength of air flows and a description of tests made in determining the strength of airplanes.
Behavior of Aviation Engines at Different Air Densities
The author expresses his views that engine performance would be affected only at very low temperatures is presented in this report.
The Dead Weight of the Airship and the Number of Passengers That Can Be Carried
In order to determine an approximate formula giving the weight of a dead load as a function of the volume (V) of the envelope and of the maximum velocity (v), we will take the relative weight of the various parts of the airship (P(sub v), M, V, A, T(sup 34)), adopting a mean value of the coefficients determined. This formula may be adopted both for semi-rigid airships with suspended nacelle and non-rigid envelope, with or without internal suspensions. It may also be adapted to airships with rigid longitudinal beam, with power units on external supports or in nacelles, and with non-rigid envelopes, with or without internal bracing cables.
Effect of aerofoil aspect ratio on the slope of the lift curve
On of the most important characteristics of an airfoil is the rate of change of lift with angle of attack, (sup dC)L/d alpha. This factor determines the effectiveness of a tail plane in securing static longitudinal stability. The application of the Gottingen formulas given here for calculating the variation of (sup Dc)L/d alpha with aspect ratio should be of interest to many aeronautical engineers. For the convenience of the engineer, a set of curves calculated by the method set forth here are given in graphical form. Also, the observed values of (sup dC)L/d alpha for the same airfoil at various aspect ratios follow the calculated curves closely.
The Glider of the College Aviation Group of the Technical High School, Hanover
This report presents the results of testing on a glider designed and built by the College Aviation Group. The design and construction were based on the following principles: 1) the glider will be made to descend as slowly as possible; 2) rigidity and resistance were arranged to meet the conditions of varied loads; 3) construction is as simple as possible; 4) and great ease in assembling and dismounting have been sought.
Langley Field wind tunnel apparatus
This report is broken up into two sections: one about the regulators for speed of wind tunnel drive motor and one about a vernier manometer with adjustable sensitivity.
Notes on the construction and testing of model airplanes
Here, it is shown that the construction of an airplane model can and should be simplified in order to obtain the most reliable test data. General requirements for model construction are given, keeping in mind that the general purpose of wind tunnel tests on a model airplane is to obtain the aerodynamic characteristics, the static balance, and the efficiency of controls for the particular combination of wings, tail surfaces, fuselage, and landing gear employed in the design. These parts must be exact scale reproductions. Any appreciable variation from scale reproduction must be in the remaining parts of the model, i.e., struts, wires, fittings, control horns, radiators, engines, and the various attachments found exposed to the wind in special airplanes. Interplane bracing is discussed in some detail.
Performance of B. M. W. 185-Horsepower Airplane Engine
"This report deals with the results of a test made upon a B. M. W. Engine in the altitude chamber of the Bureau of Standards, where controlled conditions of temperature and pressure can be made to simulate those of the desired altitude. A remarkably low value of fuel consumption - 041 per B. H. P. hour - is obtained at 1,200 revolutions per minute at an air density of 0.064 pound per cubic foot and a brake thermal efficiency of 33 per cent and an indicated efficiency of 37 per cent at the above speed and density. In spite of the fact that the carburetor adjustment does not permit the air-fuel ratio of maximum economy to be obtained at air densities lower than 0.064, the economy is superior to most engines tested thus far, even at a density lower than 0.064, the economies superior to most engines tested thus far, even at a density (0.03) corresponding to an altitude of 25,000 feet" (p. 1).
A Preliminary Investigation of a New Method for Testing Aerofoils in Free Flight
"This report is a description of a new method of testing aerofoils in free flight devised by the National Advisory Committee for Aeronautics. The method consists in lowering below a flying airplane a large inverted aerofoil on three small steel wires in such a way that the lift on the aerofoil always keeps the wires tight. The resultant force is measured by the tension in the wires, and the direction of the resultant by the amount the wing trails backwards" (p. 1).
Recent Progress in the Theory of Air Flow as Applied to Aeronautics
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.
Vibrations of Aviation Engines
Different causes of airplane engine vibration are given as well as devices to measure vibration.
Aerial Transportation
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.
The Aerodynamical Laboratory of the Vienna Technical High School
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.
Air force and three moments for F-5-L Seaplane
From Introduction: "A model of the F-5-L seaplane was made, verified, and tested at 40 miles an hour in the 8' x 8' tunnel for lift and drag, also for pitching, yawing and rolling moments. Subsequently, the yawing moment test was repeated with a modified fin. The results are reported without VL scale correction."
Deterioration of Airplane Fabrics
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.
The Efficiency of a Wind Tunnel
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.
Impact Tests for Woods
Although it is well known that the strength of wood depends greatly upon the time the wood is under the load, little consideration has been given to this fact in testing materials for airplanes. Here, results are given of impact tests on clear, straight grained spruce. Transverse tests were conducted for comparison. Both Izod and Charpy impact tests were conducted. Results are given primarily in tabular and graphical form.
Manometer for Recording Air Speed
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.
Marking Airdromes
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.
Surface area coefficients for airship envelopes
"In naval architecture, it is customary to determine the wetted surface of a ship by means of some formula which involves the principal dimensions of the design and suitable constants. These formulas of naval architecture may be extended and applied to the calculation of the surface area of airship envelopes by the use of new values of the constants determined for this purpose. Surface area coefficients were calculated from the actual dimensions, surfaces, and volumes of 52 streamline bodies, which form a series covering the entire range of shapes used in the present aeronautical practice" (p. 1).
The Theory of the Screw Propeller
Given here is a brief review of the fundamental principles of the propeller slip-stream theory and its further development through later researches, which demonstrate the connection between the propeller slip-stream theory and Frounde's so-called 'propeller blade theory.' The propeller slip-stream theory, especially in its improved form, now gives us the basis for determining the mutual influence of the parts of the blade, so that, in calculating the shape of the blade, we can get along with certain section characteristics, which have been determined once and for all. It is argued that new theories present the possibility of investigating the phenomena in the vicinity of the propeller, allowing us to calculate its action on the basis of fewer experimental values.
Aeronautic Insurance
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.
Bagnulo Heavy Fuel Internal Combustion Engine and Its Employment in Aviation
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 Choice of the Speed of an Airship
The favorable speed of an airship is chiefly determined by the condition of the consumption of the least amount of fuel per unit of traveled distance, although other conditions come into play. The resulting rules depend on the character of the wind and on the variability of the efficiency of the engine propeller units. This investigation resulted in the following rules. 1) Always keep the absolute course and steer at such an angle with reference to it as to neutralize the side wind. 2) In a strong contrary wind, take a speed one and one half times the velocity of the wind. 3) As a general rule, take the velocity of the wind and the velocity of the course component of the wind. Add them together if the wind has a contrary component, but subtract them from each other if the wind has a favorable component.
Communications and Beacons on Air Routes
Different systems of navigations beacons are discussed with an emphasis on radiotelegraphy and radiotelephony.
Differential Equations in Airplane Mechanics
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.
Hydrostatic Test of an Airship Model
An airship model made by the Goodyear Rubber Company was filled with water and suspended from a beam. The deformations of the envelope were studied under the following conditions: 1) both ballonets empty; 2) forward ballonets filled with air; 3) rear ballonets filled with air; and 4) both ballonets filled with air. Photographs were taken to record the deflections under each of these conditions, and a study was made to determine the minimum head of water necessary to maintain the longitudinal axis of the envelope under these conditions. It was concluded that any pressure sufficient to keep the airship full may be used. It appears that a pressure of one inch of water would provide a suitable factor of safety, and therefore it is the pressure that is recommended.
Maps and Navigation Methods
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.
New Data on the Laws of Fluid Resistance
Thus far, all attempts at the quantitative determination of drag, on the basis of the theory of viscous fluids, have met with but slight success. For this reason, whenever a more accurate knowledge of the drag is desirable, it must be determined by experiment. Here, a few experimental results are given on the drag of a cylinder exposed to a stream of air at right angles to its axis. It is shown that the drag depends on the absolute dimensions of the body and the velocity and viscosity of the fluid in a much more complex manner than has heretofore been supposed.
Notes on Landing Places for Sea Planes Along the Atlantic Coast
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.
Publicity by Airplane
The future of aerial photography is examined with special reference to corporate uses.
Some Principles Governing the Establishment of Meteorological Stations Along Air Routes
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.
The "Universal Propeller": Built by Paragon Engineers, Inc., Baltimore, MD.
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.
Spontaneous Combustion of Hydrogen
It is shown by the author's experiments that hydrogen which escapes to the atmosphere through openings in the system may burn spontaneously if it contains dust. Purely thermal reasoning can not account for the combustion. It seems to be rather an electrical ignition. In order to determine whether the cause of the spontaneous ignition was thermo-chemical, thermo-mechanical, or thermo-electrical, the experiments in this paper were performed.
Jet Propulsion for Airplanes
This report is a description of a method of propelling airplanes by the reaction of jet propulsion. Air is compressed and mixed with fuel in a combustion chamber, where the mixture burns at constant pressure. The combustion products issue through a nozzle, and the reaction of that of the motor-driven air screw. The computations are outlined and the results given by tables and curves.
Applying the results of experiments on small models in the wind tunnel to the calculation of full-sized aircraft
This report presents the attempt to develop a law which will permit the use of results obtained on small models in a tunnel for the calculation of full-sized airplanes, or if it exists, a law of similitude relating air forces on a full-sized plane to those on a reduced scale model.
The Background of Detonation
Note presenting a determination of the relative merits of various fuels for use in high compress engines. The main purpose is to discuss a phase that has not been given much attention in previous studies; specifically, the standpoint of the influence of charge temperatures and pressures on the temperatures and pressures after combustion.
Center of pressure coefficients for airfoils at high speeds
"It has been customary to calculate the strength of the rear wing beam for the 'high speed' condition on the assumption that the center of pressure was at 0.50 of the wing chord. It can be shown that this assumption is not justified, regardless of the utility of a 'high speed' condition in strength calculations" (p. 1).
Commercial Airplanes and Seaplanes
This report considers as the dominating characteristic, either the load carried, the speed, the radius of action, the fuel consumption, the activity of transport, or, lastly, the qualities of comfort and safety. The first four factors determine the theoretical efficiency, while the others determine its practical efficiency.
Distribution of Pressure on Fuselage of Airplane Model: Communication From Rijks-Studiedienst Voor De Luchtvaart of Amsterdam
In order to study the distribution of the pressure on the surfaces of a fuselage and the influence of the wing on the air flow along these surfaces, we have made tests pertaining to the bottom and one side. In this particular case, the wing causes an increase in pressure along the sides of the fuselage.
Evolution of Modern Aviation and Experimental and Technical Researches in Aerodynamic Laboratories
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.
Back to Top of Screen