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Study of Open Jet Wind Tunnel Cones
"Tests have been made by the National Advisory Committee for Aeronautics on the air flow in an open jet wind tunnel with various sizes, shapes, and spacings of cones, and the flow studied by means of velocity and direction surveys in conjunction with flow pictures. It was found that for all combinations of cones tested the flow is essentially the same, consisting of an inner core of decreasing diameter having uniform velocity and direction, and a boundary layer of more or less turbulent air increasing in thickness with length of jet. The energy ratio of the tunnel was obtained for the different combinations of cones, and the spilling around the exit cone causing undesirable air currents in the experiment chamber was noted" (p. 1).
Wall interference in closed type wind tunnels
"A series of tests has been conducted by the National Advisory Committee for Aeronautics, in the variable density wind tunnel on several airfoils of different sizes and sections to determine the effect of tunnel wall interference and to determine a correction which can be applied to reduce the error caused thereby. The use of several empirical corrections was attempted with little success. The Prandtl theoretical correction gives the best results and its use is recommended for correcting closed wind tunnel results to conditions of free air" (p. 1).
Tension experiments on diaphragm metals
Strips of german silver, steel, copper, duralumin, nickel and brass were tested in tension in an apparatus in which the change in deflection with time was measured by means of an interferometer. This change in deflection with time caused by the application and removal of a load is defined as "drift" and "recovery," respectively. It was measured in the time interval from approximately 5 seconds to 5 hours after loading. The data are given in a series of graphs in which the drift and recovery are plotted against time. The proportional drift and recovery in five hours are given for a number of the tests, and in addition are shown graphically for nickel and steel.
The Installation and Correction of Compasses in Airplanes
"The saving of time that results from flying across country on compass headings is beginning to be widely recognized. At the same time the general use of steel tube fuselages has made a knowledge of compass correction much more necessary than was the case when wooden fuselages were the rule. This paper has been prepared primarily for the benefit of the pilot who has never studied navigation and who does not desire to go into the subject more deeply than to be able to fly compass courses with confidence" (p. 1).
A load factor formula
The ultimate test of a load factor formula is experience. The chief advantages of a semi rational formula over arbitrary factors are that it fairs in between points of experience and it differentiates according to variables within a type. Structural failure of an airplane apparently safe according to the formula would call for a specific change in the formula. The best class of airplanes with which to check a load factor formula seems to be those which have experienced structural failure. Table I comprises a list of the airplanes which have experienced failure in flight traceable to the wing structure. The load factor by formula is observed to be greater than the designed strength in each case, without a single exception. Table II comprises the load factor by formula with the designed strength of a number of well-known service types. The formula indicates that by far the majority of these have ample structural strength. One case considered here in deriving a suitable formula is that of a heavy load carrier of large size and practically no reserve power.
Pressure distribution on wing ribs of the VE-7 and TS airplanes in flight
This paper is the first of a series of notes, each of which presents the complete results of pressure distribution tests made by the National Advisory Committee for Aeronautics, on single-wing ribs of the VE-7 and TS airplanes for a particular condition of flight. The level flight results are presented here in the form of curves and show the comparison between the pressure distribution over a representative thin wing, R.A.F.-15, and a moderately thick wing, U.S.A.-27, throughout the range of angle of attack.
Mass distribution and performance of free flight models
This note deals with the mass distribution and performance of free flight models. An airplane model which is to be used in free flight tests must be balanced dynamically as well as statically, e.g., it must not only have a given weight and the proper center of gravity but also a given ellipsoid of inertia. Equations which relate the motions of an airplane and its model are given. Neglecting scale effect, these equations may be used to predict the performance of an airplane, under the action of gravity alone, from data obtained in making dropping tests of a correctly balanced model.
The Distribution of Loads Between the Wings of a Biplane Having Decalage
"It is known that in a biplane the load is not distributed equally between the wings. The presence of one wing will affect the lift characteristics of the other wings. A designer must know the total load that each wing carries in order that he may design an adequate structure. The purpose here is to determine the distribution of loads between the wings of a biplane at various angles of decalage, when the gap/chord ratio is one, and there is no stagger" (p. 1).
Technical Preparation of the Airplane "Spirit of St. Louis"
Given here is a brief history of the design and construction of the "Spirit of St. Lewis", the airplane that Charles Lindbergh flew solo across the Atlantic. Although the plan was to modify a standard model Ryan M-2, it was quickly determined that modification was less practical than redesign. Given here are the general dimensions, specifications, weight characteristics, and man hours required to build the aircraft.
A warning concerning the take-off with heavy load
"A successful take-off can be made with an airplane so heavily loaded that it cannot climb to a height greater than the span of its wings. The explanation is that the power required to maintain level flight at an altitude of the order of the wing span may be as much as 50 per cent greater than that necessary when the airplane is just clear of the ground. The failure of heavily loaded airplanes to continue climbing at the rate attained immediately after the actual take-off is a grave hazard and has resulted in great risk or catastrophe in three notable cases which are cited" (p. 1).
"A L C L A D": A New Corrosion Resistant Aluminum Product
Described here is a new corrosion resistant aluminum product which is markedly superior to the present strong alloys. Alclad is a heat-treated aluminum, copper, manganese, magnesium alloy that has the corrosion resistance of pure metal at the surface and the strength of the strong alloy underneath. Of particular importance is the thorough character of the union between the alloy and the pure aluminum.
Airfoil lift with changing angle of attack
From Summary: "Tests have been made in the atmospheric wind tunnel of the National Advisory Committee for Aeronautics to determine the effects of pitching oscillations upon the lift of an airfoil. It has been found that the lift of an airfoil, while pitching, is usually less than that which would exist at the same angle of attack in the stationary condition, although exceptions may occur when the lift is small or if the angle of attack is being rapidly reduced. It is also shown that the behavior of a pitching airfoil may be qualitatively explained on the basis of accepted aerodynamic theory."
Method of correcting wind tunnel data for omitted parts of airplane models
Wind tunnel models do not have complete similarity to the full scale airplane. Part of the dissimilarity is due to the difference between the stationary model in the artificial wind stream of the tunnel and the moving airplane in still air. There are a number of other reasons for departing from exact geometrical similitude. For reasons of accuracy and economy, all minor parts of the full scale airplane, such as struts, wires, fittings, control horns and other parts whose scale corrections are large are removed from wind tunnel models.
Junkers Commercial Airplane G 31
The three engine Junkers commercial Airplane, type G 31 is a further development of the earlier G 24. It is an all metal low wing monoplane with a total engine output of 1100-1200 HP.
Measurement of the Moments of Inertia of Full Scale Airplanes
"This paper contains a description of the method of measuring the moments of inertia of full scale airplanes as practiced by the National Advisory Committee for Aeronautics at the Langley Memorial Aeronautical Laboratory. The method, while not at all new, is published for the information and guidance of others who may desire to make similar measurements. The paper includes as an appendix the computations for the moments of inertia of 0-2 airplane" (p. 1).
Precision of Wing Sections and Consequent Aerodynamic Effects
Note presenting an investigation to determine the precision of wing sections of wood fabric construction used on a number of airplanes. All of the wing sections were found to deviate more or less from their respective prototypes. The aerodynamic effects resulting from consideration of thickness variation are then estimated from existing empirical information.
The Characteristics of the N.A.C.A 97, Clark Y, and N.A.C.A. M6 Airfoils with Particular Reference to the Angle of Attack
Report examining the aerodynamic characteristics of three airfoil sections as determined in the variable density wind tunnel. Particular attention is given to the relation of the characteristics to the angle of attack and their use in airplane design.
Tests of the N.P.L. airship models in the variable density wind tunnel
Report presenting testing in the variable density wind tunnel on two airship models known as the NPL Standardization Models, long and short. The resistance or shape coefficients were determined for each model through a range of Reynolds numbers. Further work is found to be necessary in the standardization of wind tunnels.
The "Dornier Mercury" Commercial Airplane With B.M.W. VI 600 HP. Engine
The Dornier Mercury (Merkur) is an outgrowth of the Dornier Komet. It is designed as a passenger aircraft with the Alpine routes in mind. Its fuselage is made of steel for high stressed parts and duraluminum for all others. It can also be outfitted as a seaplane.
Dornier "Superwal" Commercial Seaplane: Two Rolls-Royce "Condor" 650 HP. Engines
In November 1926, an exhibition flight of the Dornier giant flying boat was made for 3/4 of an hour. It was a larger version of the Dornier Wal, with a stepped hull, and wing stubs for lateral stability. It has a range of 1200 miles and is outfitted for baggage and 8 passengers.
Macchi M.39 Seaplane: Single-Seat Racer With an 800 Hp. Fiat "A-S2" Engine
The M. 39 was designed by Castoldi to compete in the Schneider Cup Race of 1926 (Norfolk, VA). It is a monoplane with engine mounted in the fuselage, resting on two wing and hull mounted floats.
The Rohrbach "Robbe" Ro VII Seaplane: Military or Commercial
The RO VII is a monoplane with two 230 BMW engines mounted on top of the wing. It seats 4 passengers with room for a pilot and a mechanic in the cockpit. A description of the components, dimensions, performances, drawings, and photographs are provided.
Heinkel H.E. 50 Commercial Seaplane: Winner of the 1926 German Seaplane Contest at Warnemünde
Circular presenting a description of the Heinkel H.E.5 commercial seaplane. Its primary important characteristics are a short start, agreeable flying qualities, and long radius of action. Details of the design and flying characteristics are provided.
The Rohrbach "Rocco" Seaplane: New German Commercial Seaplane With Two Rolls-Royce "Condor" Engines
The Rocco is a has a monoplane wing surmounted by two engines. Its flat sided narrow beam hull is steadied when on the water by 2 outboard wing floats. Details of the design, hull accommodation, power plant, drawings, and photographs are provided. The report is incomplete.
The Focke-Wulf "G.L. 18" : Twin-Engine 150 HP. Commercial Airplane
A small commercial airplane, the Focke-Wulf G.L. 18 has two engines (75 HP. Junker). It is a monoplane and the engines are wing mounted. Details of the engines, power, wings, ailerons, fuselage, empennage, landing gear, characteristics, drawings, and photographs are provided.
Junkers Airplane "G 24": All-Metal Commercial Airplane
The G 24 is a commercial airplane with three engines and a monoplane wing. It is known for its all metal construction and stabilizers.
Testing a Windmill Airplane ("Autogiro")
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.
Stall-Proof Airplanes
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?
The Heat Treatment of Duralumin
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.
Permanent Commission of Aeronautical Studies Report No. 4
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.
Structural Details From 1926 Paris Aero Salon
Memorandum presenting a description of the structural details of airplanes presented at the 1926 Paris Aero Salon.
Systematic Investigation of Joukowsky Wing Sections
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.
High-Speed Oil Engines for Vehicles Part 2
"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).
High-Speed Oil Engines for Vehicles Part 3
Ignition-chamber engines and their fuel injection systems are investigated. Specific details are provided for fuel-injection nozzles and fuel pumps are provided.
Determining the Efficiency of Atomization by Its Fineness and Uniformity
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.
High-Speed Oil Engines for Vehicles Part 1: Engines With External Atomization of the Fuel, Engines With Internal Atomization of the Fuel, Hot-Bulb Engines, Diesel Engines
Different engines are tested to determine their efficiencies in burning fuel. Fuel injection and ignition chamber engines are also discussed.
Duralumin Welding
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.
On the Mutual Reaction of Wings and Body
"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).
Climbing Efficiency of Aircraft
The object of this report was to indicate that we frequently only make use of 50 percent of the maximum brake horsepower of the engine in taking off the ground, that this loss is not inevitable, and that the effort to get engines of low weight per horsepower by boosting revolutions is of very little use to bombers and commercial airplanes.
Drag measurements of two thin wing sections at different index values
It is stated that the index value 6000, as found in normal tests of wing sections with a 20 cm chord, falls in the same region where the transition of laminar to turbulent flow takes place on thin flat plates. It is to be expected that slightly cambered, thin wing sections will behave similarly. The following test of two such wing sections were made for the purpose of verifying this supposition.
Investigation of a Wing With an Auxiliary Upper Part
This report presents experiments in which two parts of the wing were arranged so as to form a biplane, which was subjected to normal three-component measurements, the two parts being placed in various relative positions with respect to the gap a and the stagger b.
Experiments With Three Horizontal Empennages
The main objective of these experiments was to determine how the air forces on the whole empennage are affected by varying the size of the elevator without changing the size of the whole empennage. The secondary objective was to determine how the magnitude of the air forces acting on the elevator (or the elevator moments) are affected by varying the angle of attack of the whole empennage, or of the elevator alone.
Effects of Roughness on Airfoils
We will here report on the effects of coarsely roughening not only the pressure side but also the suction or upper side of airfoils, as the first group of a larger series of experiments.
Experiments on airfoils with trailing edge cut away
"Airfoils with their trailing edge cut away are often found on aircraft, as the fins on the hulls of flying boats and the central section of the wings for affording better visibility. It was therefore of some interest to discover the effect of such cutaways on the lift and drag and on the position of the center of pressure. For this purpose, systematic experiments were performed on two different airfoils, a symmetrical airfoil and an airfoil of medium thickness, with successive shortenings of their chords" (p. 1).
Some Notes on Gasoline-Engine Development
Experiments were carried out using a special engine with small glass windows and a stroboscope to record various aspects of engine performance. Valve position, supercharging, and torque recoil were all investigated with this experimental apparatus.
Aero Dopes and Varnishes
Report discussing before proceeding to discuss the preparation of dope solutions, it will be necessary to consider some of the essential properties which should be possessed of a dope film, deposited in and on the surface of an aero fabric. The first is that it should tighten the material and second it should withstand weathering.
Lindbergh's Flight
Memorandum describing the flights of Charles Lindbergh and some of the calculations that go into the determination of the amount of fuel required, drag, and weight for his trip.
Discussion of the results of the boundary-layer tests of an airfoil fitted with a rotary cylinder
The results of the velocity measurements in the boundary layer described in NACA-TM 411 are here discussed in greater detail. The measurements made were of the velocity distribution in the vicinity of an airfoil model fitted with a rotary cylinder and were undertaken for the purpose of obtaining a closer insight into the phenomena observed in experimenting with this model.
Seaplanes floats and hulls. Part 1
This part of the report presents characteristics and graphic representations of water resistance. The laws of similarity are discussed as well as the theory of model tests. The test procedures and model tests of other countries are also discussed.
Seaplanes floats and hulls. Part 2
Different float designs are presented and the investigations are discussed.
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