Technical Report Archive and Image Library (TRAIL) - 419 Matching Results

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The behavior of thin-will monocoque cylinders under torsional vibration

Description: Curves of forced frequency against amplitude are presented for the conditions where the forced frequency is both increased and decreased into the resonant range. On the basis of these curves it is shown that the practical resonance frequency is the point where wrinkling first occurs and that the resonance frequency will be subject to considerable travel once permanent wrinkles appear in the vibrating shell. The decreasing mode of striking resonance is found to be by far the most destructive condition.
Date: August 1, 1937
Creator: Pekelsma, Robert E
Partner: UNT Libraries Government Documents Department

Bending stresses due to torsion in cantilever box beams

Description: The paper beings with a brief discussion on the origin of the bending stresses in cantilever box beams under torsion. A critical survey of existing theory is followed by a summary of design formulas; this summary is based on the most complete solution published but omits all refinements considered unnecessary at the present state of development. Strain-gage tests made by NACA to obtained some experimental verification of the formulas are described next. Finally, the formulas are applied to a series of box beams previously static-tested by the U.S. Army Air Corps; the results show that the bending stresses due to torsion are responsible to a large extent for the free-edge type of failure frequently experienced in these tests.
Date: June 1, 1935
Creator: Kuhn, Paul
Partner: UNT Libraries Government Documents Department

Bending tests of circular cylinders of corrugated aluminum-alloy sheet

Description: Bending tests were made of two circular cylinders of corrugated aluminum-alloy sheet. In each test failure occurred by bending of the corrugations in a plane normal to the skin. It was found, after analysis of the effect of short end bays, that the computed stress on the extreme fiber of a corrugated cylinder is in excess of that for a flat panel of the same basic pattern and panel length tested as a pin-ended column. It is concluded that this increased strength was due to the effects of curvature of the pitch line. It is also concluded from the tests that light bulkheads closely spaced strengthen corrugated cylinders very materially.
Date: March 1, 1937
Creator: Buckwalter, John C.; Reed, Warren D. & Niles, Alfred S.
Partner: UNT Libraries Government Documents Department

Boosted performance of a compression-ignition engine with a displaced piston

Description: Performance tests were made using a rectangular displacer arranged so that the combustion air was forced through equal passages at either end of the displacer into the vertical-disk combustion chamber of a single-cylinder, four-stroke-cycle compression-ignition test engine. After making tests to determine optimum displacer height, shape, and fuel-spray arrangement, engine-performance tests were made at 1,500 and 2,000 r.p.m. for a range of boost pressures from 0 to 20 inches of mercury and for maximum cylinder pressures up to 1,150 pounds per square inch. The engine operation for boosted conditions was very smooth, there being no combustion shock even at the highest maximum cylinder pressures. Indicated mean effective pressures of 240 pounds per square inch for fuel consumptions of 0.39 pound per horsepower-hour have been readily reproduced during routine testing at 2,000 r.p.m. at a boost pressure of 20 inches of mercury.
Date: May 1, 1936
Creator: Moore, Charles S & Foster, Hampton H
Partner: UNT Libraries Government Documents Department

The calculated effect of trailing-edge flaps on the take-off of flying boats

Description: 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. It is indicated that flaps would allow a decrease in the high angles of wing setting necessary with most seaplanes, provided that the excess thrust is not too low.
Date: November 1, 1934
Creator: Parkinson, J E & Bell, J W
Partner: UNT Libraries Government Documents Department

Calculated effect of various types of flap on take-off over obstacles

Description: In order to determine whether or not flaps could be expected to have any beneficial effect on take-off performance, the distances required to take off and climb to an altitude of 50 feet were calculated for hypothetical airplanes, corresponding to relatively high-speed types and equipped with several types of flap. The types considered are the Fowler wing, the Hall wing, the split flap, the balanced split flap, the plain flap, and the external-airfoil flap. The results indicate that substantial reductions in take-off distance are possible through the use of flaps, provided that the proper flap angle corresponding to a given set of conditions is used. The best flap angle for taking off varies inversely as power loading and, to a much smaller extent, varies inversely with wing loading. Apparently, the best take-off characteristics are provided by the type of device in which the flap forms an extension to the main wing as in the case of the Fowler wing and the external-airfoil flap.
Date: May 1, 1936
Creator: Wetmore, J W
Partner: UNT Libraries Government Documents Department

Calculations of the effect of wing twist on the air forces acting on a monoplane wing

Description: A method is presented for calculating the aerodynamic forces on a moncylane wing, taking into account the elastic twisting of the wing due to these forces. The lift distribution along the span is calculated by the formulas of Amstutz as a function of the geometrical characteristics of the wing and of the twist at stations 60 and 90 percent of the semispan. The twist for a given lift distribution is calculated by means of influence lines. As a numerical example, the forces on a Swiss military D.2V airplane are calculated. Comparisons with the strip method and with the ordinary stress-analysis method are also given.
Date: January 1, 1935
Creator: Datwyler, G
Partner: UNT Libraries Government Documents Department

Calibration and lag of a Friez type cup anemometer

Description: Tests on a Friez type cup anemometer have been made in the variable density wind tunnel of the Langley Memorial Aeronautical Laboratory to calibrate the instrument and to determine its suitability for velocity measurements of wind gusts. The instrument was calibrated against a Pitot-static tube placed directly above the anemometer at air densities corresponding to sea level, and to an altitude of approximately 6000 feet. Air-speed acceleration tests were made to determine the lag in the instrument reading. The calibration results indicate that there should be an altitude correction. It is concluded that the cup anemometer is too sluggish for velocity measurements of wind gusts.
Date: June 1, 1930
Creator: Pinkerton, Robert M
Partner: UNT Libraries Government Documents Department

Carbon-monoxide indicators for aircraft

Description: Several improvements that have been made on commercially available carbon-monoxide indicators to make them more suitable for aircraft use are described. These improvements include an automatic flow regulator, which permits the use of a simplified instrument on aircraft where a source of suction is available, and a more reliable alarm attachment. A field method for testing instruments on standard samples of carbon monoxide is described. Performance data and instructions in operation and maintenance are given.
Date: July 1, 1936
Creator: Womack, S H J & Peterson, J B
Partner: UNT Libraries Government Documents Department

Characteristics of an airfoil as affected by fabric sag

Description: This report presents the results of tests made at a high value of the Reynolds Number in the N.A.C.A. variable-density wind tunnel to determine the aerodynamic characteristics of an airfoil as affected by fabric sag. Tests were made of two Gottingen 387 airfoils, one having the usual smooth surface and the other having a surface modified to simulate two types of fabric sag. The results of these tests indicate that the usual sagging of the wind covering between ribs has a very small effect on the aerodynamic characteristics of an airfoil.
Date: August 1, 1932
Creator: Ward, Kenneth E
Partner: UNT Libraries Government Documents Department

Characteristics of two sharp-nosed airfoils having reduced spinning tendencies

Description: According to Mr. L.D. Bell, of the Consolidated Aircraft Corporation, certain undesirable spinning characteristics of a commercial airplane were eliminated by the addition of a filler to the forward part of the wing to give it a sharp leading edge. To ascertain what aerodynamic effects result from such a change of section, two airfoils having sharp leading edges were tested in the variable-density wind tunnel. Both sections were derived by modifying the Gott. 398. The tests, which were made at a large value of the Reynolds Number, were carried to very large angles of attack to provide data for application to flight at angles of attack well beyond the stall. The characteristics of the sharp-nosed airfoils are compared with those of the normal Gott. 398 airfoil. Both of the sharp-nosed airfoils, which differ in the angle between the upper and lower surfaces at the leading edge, have about the same characteristics. As compared with the normal airfoil, the maximum lift is reduced by approximately 26 per cent, but the objectionable rapidly decreasing lift with angle of attack beyond the stall is eliminated; the profile drag of the section is slightly reduced in the range of the lift coefficient between 0.2 and 0.85, but at higher and lower lift coefficients the drag is increased.
Date: April 1, 1932
Creator: Jacobs, Eastman N.
Partner: UNT Libraries Government Documents Department

The charging process in a high-speed, single-cylinder, four-stroke engine

Description: Experimental measurements and theoretical calculations were made on an aircraft-type, single cylinder engine, in order to determine the physical nature of the inlet process, especially at high piston speeds. The engine was run at speeds from 1,500 to 2,600 r.p.m. (mean piston speeds of 1,370 to 2,380 feet per minute). Measurements were made of the cylinder pressure during the inlet stroke and of the power output and volumetric efficiency. Measurements were also made, with the engine not running, to determine the resistance and mass of air in the inlet valve port at various crank angles. Results of analysis indicate that mass has an appreciable effect, but friction plays the major part in restricting flow. The observed fact that the volumetric efficiency is considerably less than 100 percent is attributed to thermal effects. An estimate was made of the magnitude of these effects in the present case, and their general nature is discussed.
Date: February 1, 1939
Creator: Reynolds, Blake; Schecter, Harry & Taylor, E S
Partner: UNT Libraries Government Documents Department

Charts expressing the time, velocity, and altitude relations for an airplane diving in a standard atmosphere

Description: In this report charts are given showing the relation between time, velocities, and altitude for airplanes having various terminal velocities diving in a standard atmosphere. The range of starting altitudes is from 8,000 to 32,000 feet, and the terminal velocities vary from 150 to 550 miles per hour. A comparison is made between an experimental case and the results obtained from the charts. Examples pointing out the use of the charts are included.
Date: April 1, 1937
Creator: Pearson, H A
Partner: UNT Libraries Government Documents Department

Charts for calculating the performance of airplanes having constant-speed propellers

Description: Charts are presented for determining the performance of airplanes having variable-pitch propellers, the pitch of which is assumed to be adjusted to maintain constant speed for all rates of flight. The charts are based on the general performance equations developed by Oswald in reference 1, and are used in a similar manner. Examples applying the charts to airplanes having both supercharged and unsupercharged engines are included.
Date: September 1, 1936
Creator: White, Roland J & Martin, Victor J
Partner: UNT Libraries Government Documents Department

Charts for determining the pitching moment of tapered wings with sweepback and twist

Description: This report presents a convenient method for calculating the pitching-moment characteristics of tapered wings with sweepback and twist. The method is based on the fact that the pitching-moment characteristics of a wing may be specified by giving the value of the pitching moment at zero lift and the location of the axis about which the axis is constant. Data for calculating these characteristics are presented by curves which apply to wings having a linear distribution of twist along the span and which cover a large range of aspect ratios. The curves are given for wings having straight taper and distorted elliptical plan forms. The characteristics of wings of other shapes may be determined by interpolation.
Date: December 1, 1933
Creator: Anderson, Raymond F
Partner: UNT Libraries Government Documents Department

Circular motion of bodies of revolution

Description: The circular motion for airship-like bodies has thus far been calculated only for a prolate ellipsoid of revolution (reference 1, p.133 and reference 2). In this paper, however, the circular motion of elongated bodies of revolution more nearly resembling airships will be investigated. The results will give the effect of rotation on the pressure distribution and thus yield some information as to the stresses set up in an airship in circular flight.
Date: February 1, 1936
Creator: Kaplan, Carl
Partner: UNT Libraries Government Documents Department

Circulation measurements about the tip of an airfoil during flight through a gust

Description: Measurements were made of the circulation about the rectangular tip of a short-span airfoil passing through an artificial gust of known velocity gradient. A Clark Y airfoil of 30-centimeter chord was mounted on a whirling arm and moved at a velocity of 29 meters per second over a vertical gust with a velocity of nearly 7 meters per second. Flow angles were measured with a hot-wire apparatus. The rate at which the lift at the tips of a wing entering a gust is realized was found to be in satisfactory agreement with that predicted on the basis of the two-dimensional theory of von Karman and Sears.
Date: February 1, 1939
Creator: Kuethe, Arnold
Partner: UNT Libraries Government Documents Department

Combined beam-column stresses of aluminum-alloy channel sections

Description: The results of a research program to obtain design data on the strength of open-channel aluminum-alloy sections subjected to combined column and beam action. The results of the tests of about 70 specimens were graphed for stresses due to axial load and stresses due to bending loading as functions of length to radius of gyration of the specimens. From these graphs a design chart was derived that is suitable for ready use.
Date: September 1, 1939
Creator: Gottlieb, R; Thompson, T M & Witt, E C
Partner: UNT Libraries Government Documents Department

Combustion-engine temperatures by the sodium line-reversal method

Description: The sodium line-reversal method has been used in some preliminary measurements of flame temperature. Improvements in the method involving a photographic recorder and a means of correcting for the dirtiness of the windows are described. The temperatures so obtained are compared with those calculated from pressure diagrams.
Date: March 1, 1936
Creator: Brevoort, Maurice J.
Partner: UNT Libraries Government Documents Department

Comparative performance obtained with XF7C-1 airplane using several different engine cowlings

Description: Discussed here are problems with the use of cowlings with radial air cooled engines. An XF7C-1 airplane, equipped with service cowling and with narrow ring, wide ring, and exhaust collector ring cowlings over the service cowling, was used. For these four cowling conditions, the rate of climb and high speed performance were determined, the cylinder conditions were measured, and pictures to show visibility were taken. The level flight performance obtained with an engine speed of 1900 r.p.m. for the service type, the narrow ring, the wide ring, and the exhaust collector ring was 144.4, 146.6, 152.8, and 155 mph, respectively. The rate of climb was practically the same for each type tested. The visibility was not materially impaired by the use of the wide or the narrow cowlings. With the narrow ring and exhaust collector ring cowlings there was an increase in cylinder temperature. However, this increase was not enough to affect the performance of the engine. The use of an exhaust collector ring incorporated into the cowling is practical where the problem of visibility does not enter.
Date: February 1, 1930
Creator: Schey, Oscar W.; Johnson, Ernest & Gough, Melvin N.
Partner: UNT Libraries Government Documents Department

Comparative performance of a Powerplus vane-type supercharger and an N.A.C.A. Roots-type supercharger

Description: This report presents the results of tests of a Power plus supercharger and a comparison of its performance with the performance previously obtained with an N.A.C.A. Roots-type supercharger. The Powerplus supercharger is a positive displacement blower of the vane type having mechanically operated vanes, the movement of which is controlled by slots and eccentrics. The supercharger was tested at a range of pressure differences from 0 to 15 inches of mercury and at speeds from 500 to 2,500 r.p.m. The pressure difference across the supercharger was obtained by throttling the intake of a depression tank which was interposed in the air duct between the supercharger and the Durley orifice box used for measuring the air. The results of these tests show that at low pressure differences and at all speeds the power required by the Powerplus supercharger to compress a definite quantity of air per second is considerably higher than that required by the Roots. At pressure differences from 10 to 14 inches of mercury and at speeds over 2,000 r.p.m. the power requirements of the two superchargers are practically the same. At a pressure difference of 15 inches of mercury or greater and at a speed of 2,500 r.p.m. or greater the performance of the Powerplus supercharger is slightly better than that of the Roots. Because the Powerplus supercharger cannot be operated at a speed greater than 3,000 r.p.m. as compared with 7,000 r.p.m. for the Roots, its capacity is approximately one-half that of the Roots for the same bulk. The Powerplus supercharger is more complicated and less reliable than the Roots supercharger.
Date: July 1, 1932
Creator: Schey, Oscar W. & Ellerbrock, Herman H., Jr.
Partner: UNT Libraries Government Documents Department