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The Aachen Wind-Tunnel Balance
Report discussing a description of the balance in the Aachen wind-tunnel.
Additional Test Data on Static Longitudinal Stability
From Summary: "The purpose of this investigation was to explore the influence of weights of the controls on the stability with elevator released. The available test data were extended to stability with elevator locked. In this connection the study of the propeller effect seemed of vital importance."
An Aerodynamic Analysis of the Autogiro Rotor With a Comparison Between Calculated and Experimental Results
This report presents an extension of the autogiro theory of Glauert and Lock in which the influence of a pitch varying with the blade radius is evaluated and methods of approximating the effect of blade tip losses and the influence of reversed velocities on the retreating blades are developed. A comparison of calculated and experimental results showed that most of the rotor characteristics could be calculated with reasonable accuracy, and that the type of induced flow assumed has a secondary effect upon the net rotor forces, although the flapping motion is influenced appreciably. An approximate evaluation of the effect of parasite drag on the rotor blades established the importance of including this factor in the analysis.
The Aerodynamic Analysis of the Gyroplane Rotating-Wing System
"An aerodynamic analysis of the gyroplane rotating-wing system is presented herein. This system consists of a freely rotating rotor in which opposite blades are rigidly connected and allowed to rotate or feather freely about their span axis. Equations have been derived for the lift, the lift-drag ratio, the angle of attack, the feathering angles, and the rolling and pitching moments of a gyroplane rotor in terms of its basic parameters" (p. 1).
Aerodynamic Characteristics of Anemometer Cups
From Introduction: "The investigation was intended to cover the characteristics of individual cups and of similar cups mounted on complete cup wheals. This report treats the static tests run on the individual cups."
Aerodynamic Effects of a Split Flap on the Spinning Characteristics of a Monoplane Model
From Summary: "The investigation described in this report was made to determine the change in aerodynamic forces and moments produced by split flaps in a steady spin. The test were made with the spinning balance in the NACA 5-foot vertical wind tunnel. A low-wing monoplane model was tested with and without the split flaps in 12 spinning attitudes chosen to cover the probable spinning range. The results obtained indicate that the use of split flaps on an airplane is unlikely, in any case, to have much beneficial effect on a spin, and it might make the spin dangerous."
The aerodynamic effects of wing cut-outs
From Introduction: "The information now available concerning wing cut-outs or applicable to the analysis of their effects is plentiful (references 1 to 7) but too disconnected and unorganized to be of the greatest possible usefulness. In connection with the interference program being conducted in the N.A.C.A. varible-density wind tunnel, an analysis was therefore made of existing material to determine the qualitative effects of the different features of wing cut-outs, and to obtain means of calculating wing characteristics as affected by them."
Aerodynamic Investigation of a Cup Anemometer
Results of an investigation wherein the change of the normal force coefficient with Reynolds Number was obtained statically for a 15.5-centimeter hemispherical cup.
Aerodynamic principles of the direct lifting propeller
From Summary: "The purpose of this report is to make the complicated processes on the direct-lift propeller amenable to analysis and observation. This is accomplished by placing the physical phenomena, starting with the most elementary process, in the foreground, while limiting the mathematical treatment to the most essential in view of the fundamental defects of the theorems. Comparison with model experiments supplements and corroborates the theoretical results."
Aerodynamic Rolling and Yawing Moments Produced by Floating Wing-Tip Ailerons, as Measured by Spinning Balance
From Summary: "The investigation described in this report was made to determine the effectiveness of floating wing-tip ailerons as an airplane control in the spin. In these tests the ailerons, not being balanced, were set parallel to the axis of rotation, which is probably very nearly the attitude that balanced floating ailerons would assume in a spin. Rolling - and yawing moment coefficients are given as measured for the model with and without the ailerons, and computed values are given for the ailerons alone."
Air conditions close to the ground and the effect on airplane landings
This report presents the results of an investigation undertaken to determine the feasibility of making glide landings in gusty air. Wind velocities were measured at several stations between the ground and a height of 51 feet, and flight tests were made to determine the actual influence of gusts on an airplane gliding close to the ground.
Air flow in a separating laminar boundary layer
Report discussing the speed distribution in a laminar boundary layer on the surface of an elliptic cylinder, of major and minor axes 11.78 and 3.98 inches, respectively, has been determined by means of a hot-wire anemometer. The direction of the impinging air stream was parallel to the major axis. Special attention was given to the region of separation and to the exact location of the point of separation. An approximate method, developed by K. Pohlhausen for computing the speed distribution, the thickness of the layer, and the point of separation, is described in detail; and speed-distribution curves calculated by this method are presented for comparison with experiment.
Analysis of 2-Spar Cantilever Wings With Special Reference to Torsion and Load Transference
"This paper deals with the analysis of 2-spar cantilever wings in torsion, taking cognizance of the fact that the spars are not independent, but are interconnected by ribs and other structural members. The principles of interaction are briefly explained, showing that the mutual relief action occurring depends on the "pure torsional stiffness" of the wing cross section. Various practical methods of analysis are outlined" (p. 45).
An Analysis of Longitudinal Stability in Power-Off Flight With Charts for Use in Design
"This report presents a discussion of longitudinal stability in gliding flight together with a series of charts with which the stability characteristics of any airplane may be readily estimated. The relationships governing stability characteristics are derived from equations of equilibrium referred to moving axes that are tangent and perpendicular to the instantaneous flight path. It is shown that instability of the motion can arise only through an increase of linear and angular momentum in the system during one complete cycle" (p. 289).
Analysis of Spinning in a Monoplane Wing by the Induction Method as Compared With the Strip Method
The problem of autorotation has been attacked by various authors, in particular Fuchs and Schmidt who applied the so-called strip method which is based upon the assumption that the forces and moments per unit length acting in each section of the wing are equal to those on an infinite cylindrical wing of equal section in an air flow of intensity and direction resulting from the apparent relative motion of this section with respect to the surrounding air. In other words they disregarded the induced velocities, which, however, are of such importance that their omission is bound to result in appreciable errors, as we attempt to prove in this report.
Annual Report of the National Advisory Committee for Aeronautics (19th). Administrative Report Including Technical Report Nos. 441 to 474
Report includes the National Advisory Committee for Aeronautics letter of submittal to the President, Congressional report, summaries of the committee's activities and research accomplished, bibliographies, and financial report.
The Avia 51 Commercial Airplane (Czechoslovakian): A Cantilever High-Wing Monoplane
Circular describing the Avia 51 commercial airplane, which is a Czechoslovakian cantilever high-wing monoplane with a fairly orthodox design. Details of the performance, construction, wing, ailerons, fuselage, landing gear, engines, characteristics, drawings, and photographs are provided.
Avro 642 Commercial Airplane (British): A High-Wing Cantilever Monoplane
Circular describing the Avro 642, which is a mixed construction high-wing cantilever monoplane. Details of the engines, controls, interior, wings, cockpit, ailerons, landing gear, characteristics, performance, drawings, and photographs are provided.
Avro C.30 Direct-Control Autogiro (British)
Circular describing the Avro C.30 direct-control autogiro. Details of the construction, fuselage, engine mounting, tail, cockpits, rotor system, characteristics, performance, drawings, and photographs are provided.
The Avro "Commodore" Touring Airplane (British): A Cabin Biplane
Circular describing the Avro Commodore, which is a cabin biplane of metal construction that is designed for comfort rather than performance. Details regarding the fuselage, wings, landing gear, controls, characteristics, drawings, and photographs are provided.
The Behavior Under Shearing Stress of Duralumin Strip With Round, Flanged Holes
"This report presents the results of an investigation to determine the behavior of dural strip with flanged holes in the center when subjected to shear stresses. They buckle under a certain load just as a flat sheet. There is one optimum hole spacing and a corresponding buckling load in shear for each sheet width, sheet thickness, and flange form. Comparison with non-flanged sheets revealed a marked increase of buckling load in shear due to the flanging and a slightly greater displacement" (p. 1).
The Bernard 82 Military Airplane (French): A Long-Range Monoplane
Circular presenting a description of the Bernard 82, which is a scaled-up version of the 80 G.R.; they have similar designs but the 82 has greater span and wing area, deeper chord, higher fuselage, and a thicker wing for the bombs. A description of some flight tests and characteristics is also provided.
The British Klemm "Eagle" Commercial Airplane: A Low-Wing Cantilever Monoplane
Circular presenting a description of the British Klemm "Eagle", which is a low-wing commercial cantilever monoplane. Details of the components, flying qualities, design characteristics, weights and loadings, drawings, and photographs are provided.
The Calculated Effect of Trailing-Edge Flaps on the Take-Off of Flying Boats
"The results of take-off calculations are given for an application of simple trailing-edge flaps to two hypothetical flying boats, one having medium wing and power loading and consequently considerable excess of thrust over total resistance during the take-off run, the other having high wing and power loading and a very low excess thrust. For these seaplanes the effect of downward flap settings was: (1) to increase the total resistance below the stalling speed, (2) to decrease the get-away speed, (3) to improve the take-off performance of the seaplane having considerable excess thrust, and (4) to hinder the take-off of the seaplane having low excess thrust" (p. 1).
The Calculation of Lateral Stability With Free Controls
The discussion of the structural methods for obtaining lateral stability discloses the remarkable influence of the constant fuselage and wing proportions to the yawing moments. For the effectiveness of modifications in vertical tail surfaces and tail length, these quotas - little observed heretofore, in this connection - are decisive. This also applies to the amount of dihedral of the wing with regard to the roll stability of the complete wing already existing without angle of the dihedral.
The calculation of take-off run
From Summary: "A comparatively simple method of calculating length of take-off run is developed from the assumption of a linear variation in net accelerating force with air speed and it is shown that the error involved is negligible. Detailed instructions are given for application of the formula and for the calculation of all factors involved."
A comparison of fuel sprays from several types of injection nozzles
This report presents the tests results of a series of tests made of the sprays from 14 fuel injection nozzles of 9 different types, the sprays being injected into air at atmospheric density and at 6 and 14 times atmospheric density. High-speed spark photographs of the sprays from each nozzle at each air density were taken at the rate of 2,000 per second, and from them were obtained the dimensions of the sprays and the rates of spray-tip penetration. The sprays were also injected against plasticine targets placed at different distances from the nozzles, and the impressions made in the plasticine were used as an indication of the distribution of the fuel within the spray. Cross-sectional sketches of the different types of sprays are given showing the relative sizes of the spray cores and envelopes. The characteristics of the sprays are compared and discussed with respect to their application to various types of engines.
A comparison of several methods of measuring ignition lag in a compression-ignition engine
"The ignition lag of a fuel oil in the combustion chamber of a high speed compression-ignition engine was measured by three different methods. The start of injection of the fuel as observed with a Stoborama was taken as the start of the period of ignition lag in all cases. The end of the period of ignition lag was determined by observation of the appearance of incandescence in the combustion chamber, by inspection of a pressure-time card for evidence of pressure rise, and by analysis of the indicator card for evidence of the combustion of a small but definite quantity of fuel" (p. 1).
The Comper "Streak" Single Seat Airplane (British): A Low-Wing Cantilever Monoplane
Circular describing the Comper Streak single-seat low-wing cantilever monoplane. Details of the fuselage, construction, wing, stabilizer, engine, landing gear, characteristics, drawings, and photographs are provided.
A complete tank test of a flying-boat hull with a pointed step - N.A.C.A. Model No. 22
"The results of a complete tank test of a model of a flying-boat hull of unconventional form, having a deep pointed step, are presented in this note. The advantage of the pointed-step type over the usual forms of flying-boat hulls with respect to resistance at high speeds is pointed out. A take-off example using the data from these tests is worked out, and the results are compared with those of an example in which the test data for a hull of the type in general use in the United States are applied to a flying boat having the same design specifications. A definite saving in take-off run is shown by the pointed-step type" (p. 1).
A complete tank test of the hull of the Sikorsky S-40 flying boat - American Clipper Class
The results of a complete test in the N.A.C.A. tank on a model of the hull of Sikorsky S-40 flying boat ('American Clipper') are reported. The test data are given in tables and curves. From these data non-dimensional coefficients are derived for use in take-off calculations and the take-off time and run for the S-40 are computed. The computed take-off time was obtained by the Sikorsky Aviation Corporation in performance tests of the actual craft.
Complete tank tests of two flying-boat hulls with pointed steps - N.A.C.A. Models 22-A and 35
"This note presents the results of complete tank test of N.A.C.A. Models 22-A and 35, two flying-boat hulls of the deep pointed-step type with low dead rise. Model 22-A is a form derived by modification of Model 22, the test results of which are given in N.A.C.A. Technical Note No. 488. Model 35 is a form of the same type but has a higher length-beam ratio than either Model 22 or 22-A. Take-off examples are worked out using data from these tests and a previous test of a conventional model applied to an arbitrary set of design specifications for a 15,000-pound flying boat" (p. 1).
Computation of the two-dimensional flow in a laminar boundary layer
A comparison is made of the boundary-layer flow computed by the approximate method developed by K. Pohlhausen with the exact solutions which have been published for several special cases. A modification of Pohlhausen's method has been developed which extends the range of application at the expense of some decrease in the accuracy of the approximations.
Contribution to the Mutual Interference of Wing and Propeller
"The change of induced wing drag due to the field of flow of the propeller was analyzed quantitatively. The field of flow of the propeller is represented by a uniform distribution of sinks over the propeller disk area, whose strength is determined by the increase in speed in the slipstream. The superposition of this sink flow on the basic flow reproduces the actual field of flow outside of the slipstream with close approximation" (p. 1).
Conversion of Energy in Cross-Sectional Divergences Under Different Conditions of Inflow
"This investigation treats the conversion of energy in conically divergent channels with constant opening ratio and half included angle of from 2.6 to 90 degrees, the velocity distribution in the entrance section being varied from rectangular distribution to fully developed turbulence by changing the length of the approach. The energy conversion is not completed in the exit section of the diffuser; complete conversion requires a discharge length which depends upon the included angle and the velocity distribution in the entrance section. Lastly, a spiral fan was mounted in the extreme length and the effect of the spiral flow on the energy conversion in the cross-sectional divergence explored" (p. 1).
Cooling characteristics of a 2-row radial engine
This report presents the results of cooling tests conducted on a calibrated GR-1535 Pratt and Whitney Wasp, Jr. Engine installed in a Vought X04U-2 airplane. The tests were made in the NACA full-scale tunnel at air speeds from 70 to 120 miles per hour, at engine speeds from 1,500 to 2,600 r.p.m., and at manifold pressures from 19 to 33 inches of mercury absolute. A Smith controllable propeller was used to facilitate obtaining the different combinations of engine speed, power, and manifold pressure.
The De Havilland "Comet" Long-Range Airplane (British): A Low-Wing Cantilever Monoplane
Circular describing the De Havilland Comet, which is a long-range airplane that has been designed for the England-Australia race and was constructed using a stressed-skin construction. Details of the fuselage, landing gear, design, drawings, and photographs are provided.
A description and test results of a spark-ignition and a compression-ignition 2-stroke-cycle engine
This report presents performance results of air cooled and water-cooled engines. The results obtained were sufficiently promising to warrant further investigation with fuel injection and spark ignition, with the same arrangement of inlet ports and exhaust valves at the bottom of the cylinder and the exhaust gases discharged through two poppet valves in the cylinder head. The displacement of the engine was 118 cubic inches. Optimum performance was obtained with the inlet air directed into the cylinder at an angle of 20 degrees to the radial.
The Development of Floats and Equipment for Research in Promoting It
Providing information that will make possible a favorable compromise between landing impact and planing resistance is the immediate problem in experimental float development. A description of equipment to perform dropping tests are included as well as how to determine the landing impact.
The drag of airplane wheels, wheel fairings, and landing gears - 1
This report presents the results of tests made in the 7-by 10-foot wind tunnel and in the 20-foot tunnel of the National Advisory Committee for Aeronautics to determine the drag of a number of airplane wheels, wheel fairings, and landing gears designed or selected for an airplane of 3,000 pounds gross weight. All tests were made on full-size models; those in the 7-by 10-foot tunnel were made at air speeds up to 80 miles per hour and those in the 20-foot tunnel were made at air speeds up to 100 miles per hour. Although most of the landing-gear tests were made in conjunction with a fuselage and at 0 degree pitch angle, some of the tests were made in conjunction with fuselage plus wings and a radial air-cooled engine and at pitch angles from -5 degrees to 6 degrees to obtain an indication of the general effect of these various items on landing-gear drag.
The drag of airplane wheels, wheel fairings, and landing gears 2: nonretractable and partly retractable landing gears
This is the second report giving the results obtained in the NACA 20-foot wind tunnel on the drag due to landing gears. The present report gives the results of tests of nonretractable and partly retractable landing gears intended for heavier low-wing monoplanes of the transport and bomber type.
The drag of airplane wheels, wheel fairings, and landing gears - 3
The tests reported in this report conclude the investigation of landing-gear drag that has been carried out in the NACA 20-foot wind tunnel. They supplement earlier tests (reported in Technical Report No. 485) made with full-scale dummy wheels, wheel fairings, and landing gears intended for airplanes of 3,000 pounds gross weight and include tests of tail wheels and tail skids.
The effect of baffles on the temperature distribution and heat-transfer coefficients of finned cylinders
This report presents the results of an investigation to determine the effect of baffles on the temperature distribution and the heat-transfer coefficient of finned cylinders. The tests were conducted in a 30-inch wind tunnel on electrically heated cylinders with fins of 0.25 and 0.31 inch pitch. The results of these tests showed that the use of integral baffles gave a reduction of 31.9 percent in the rear wall temperatures and an increase of 54.2 percent in the heat transfer coefficient as compared with a cylinder without baffles.
Effect of Combustion-Chamber Shape on the Performance of a Prechamber Compression-Ignition Engine
"The effect on engine performance of variations in the shape of the prechamber, the shape and direction of the connecting passage, the chamber volume using a tangential passage, the injection system, and the direction of the fuel spray in the chamber was investigated using a 5 by 7 inch single-cylinder compression-ignition engine. The results show that the performance of this engine can be considerably improved by selecting the best combination of variables and incorporating them in a single design. The best combination as determined from these tests consisted of a disk-shaped chamber connected to the cylinder by means of a flared tangential passage" (p. 1).
Effect of Fuselage and Engine Nacelles on Some Aerodynamic Properties of an Airplane Wing
"With the aid of the method of J. Lotz, the writer undertook to solve theoretically the lift distribution along the span of an airplane wing, when the outline of the wing is uneven. This problem arises in the case of a mid-wing monoplane with embedded engine nacelles. The fuselage and the nacelles were considered as aerodynamically profiled, that is, as lift-producing parts. The task was therefore to determine not only the disturbance caused by the fuselage and nacelles, but also their share in the total lift of the wing" (p. 1).
Effect of moderate air flow on the distribution of fuel sprays after injection cut-off
"High-speed motion pictures were taken of fuel sprays with the NACA spray-photographic apparatus to study the distribution of the liquid fuel from the instant of injection cut-off until about 0.05 second later. The fuel was injected into a glass-walled chamber in which the air density was varied from 1 to 13 times atmospheric air density (0.0765 to 0.99 pound per cubic foot) and in which the air was at room temperature. The air in the chamber was set in motion by means of a fan, and was directed counter to the spray at velocities up to 27 feet per second" (p. 163).
Effect of Retractable-Spoiler Location on Rolling- and Yawing-Moment Coefficients
"In this report are presented the results of wind-tunnel tests of retractable spoilers on the upper surface of a Clark Y wing, which have been made as part of an investigation of lateral control devices being conducted by the National Advisory Committee for Aeronautics. Spoilers with chords up to 15.0 percent of the wing chord were tested in several locations on a plain rectangular wing and in two locations on the same wing equipped with a 20.0 percent chord split flap down 60 degrees. Charts are given for four representative angles of attack from which values of rolling- and yawing-moment coefficients may be obtained for spoilers up to 15.0 percent chord located on the upper surface of a Clark Y wing" (p. 1).
The Effect of Spray Strips on the Take-Off Performance of a Model of a Flying-Boat Hull
"The effect on the take-off performance of a model of the hull of a typical flying boat, Navy PH-1, of fitting spray strips of four different widths, each at three different angles, was determined by model tests in the NACA Tank. Spray strips of widths up to 3 percent of the beam improve the general performance at speeds near the hump and reduce the spray thrown. A downward angle of 30 degrees to 45 degrees in the neighborhood of the step seems most favorable for the reduction of the spray" (p. 523).
Effect of the Surface Condition of a Wing on the Aerodynamic Characteristics of an Airplane
"In order to determine the effect of the surface conditions of a wing on the aerodynamic characteristics of an airplane, tests were conducted in the N.A.C.A. full-scale wind tunnel on the Fairchild F-22 airplane first with normal commercial finish of wing surface and later with the same wing polished. Comparison of the characteristics of the airplane with the two surface conditions shows that the polish caused a negligible change in the lift curve, but reduced the minimum drag coefficient by 0.001. This reduction in drag if applied to an airplane with a given speed of 200 miles per hour and a minimum drag coefficient of 0.025 would increase the speed only 2.9 miles per hour, but if the speed remained the same, the power would be reduced 4 percent" (p. 1).
The effect of trim angle on the take-off performance of a flying boat
From Summary: "Data obtained at the N.A.C.A. tank from tests on the models of three flying-boat hulls - N.A.C.A. models 11-A, 16, and 22 - are used to demonstrate the effect of trim angle on water resistance. A specific example is taken, and data from Model 11-A are used to show that the trim angle giving the minimum water resistance will give minimum total air-plus-water resistance. Total-resistance curves for best trimmed angles and other angles are compared for the same example."
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