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  Partner: UNT Libraries Government Documents Department
 Decade: 1940-1949
 Year: 1940
 Serial/Series Title: NACA Technical Notes
Aerodynamic heating and the deflection of drops by an obstacle in an air stream in relation to aircraft icing

Aerodynamic heating and the deflection of drops by an obstacle in an air stream in relation to aircraft icing

Date: October 1, 1940
Creator: Kantrowitz, Arthur
Description: Two topics of interest to persons attempting to apply the heat method of preventing ice formation on aircraft are considered. Surfaces moving through air at high speed are shown, both theoretically and experimentally, to be subject to important aerodynamic heating effects that will materially reduce the heat required to prevent ice. Numerical calculations of the path of water drops in an air stream around a circular cylinder are given. From these calculations, information is obtained on the percentage of the swept area cleared of drops.
Contributing Partner: UNT Libraries Government Documents Department
The aileron as an aid to recovery from the spin

The aileron as an aid to recovery from the spin

Date: September 1, 1940
Creator: Neihouse, A I
Description: As part of a general investigation by the NACA of factors that affect the spin, the use of the aileron as an aid to recovery from the spin was studied. Tests of 10 different models, covering a wide range of mass distribution, were made in the NACA free-spinning tunnel to determine the effects of a large downward deflection of the outboard aileron and of normal angular deflections of the ailerons upon recovery characteristics. The results indicate that the direction of aileron setting, with or against the spin, which will aid recovery from the spin depends upon the airplane weight distribution. For monoplanes and for biplanes with lower-wing ailerons, ailerons with the spin will be favorable when the weight is distributed chiefly along the fuselage (single-engine airplanes) and ailerons against the spin will be favorable when the weight is distributed chiefly along the wings (multi engine airplanes). Downward movement of the outboard aileron through a large angle will not always be effective in aiding recovery, the effectiveness of such a movement also being dependent upon the weight distribution of the airplane.
Contributing Partner: UNT Libraries Government Documents Department
Analysis of cylinder-pressure-indicator diagrams showing effects of mixture strength and spark timing

Analysis of cylinder-pressure-indicator diagrams showing effects of mixture strength and spark timing

Date: August 1, 1940
Creator: Gerrish, Harold C & Voss, Fred
Description: An investigation was made to determine the effect of mixture strength and of normal as well as optimum spark timing on the combustion, on the cylinder temperature, and on the performance characteristics of an engine. A single-cylinder test unit utilizing an air-cooled cylinder and a carburetor and operating with gasoline having an octane rating of 92 was used. The investigation covered a range of fuel-air ratios from 0.053 to 0.118. Indicator diagrams and engine-performance data were taken for each change in engine conditions. Examination of the indicator shows that for fuel-air ratios less than and greater than 0.082 the rate and the amount of effective fuel burned decreased. For a fuel-air ratio of 0.118 the combustion efficiency was only 58 percent. Advancing the spark timing increased the rate of pressure rise. This effect was more pronounced with leaner mixtures.
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Analysis of wind-tunnel data on directional stability and control

Analysis of wind-tunnel data on directional stability and control

Date: September 1, 1940
Creator: Pass, H R
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Chart for critical compressive stress of flat rectangular plates

Chart for critical compressive stress of flat rectangular plates

Date: August 1, 1940
Creator: Hill, H N
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Correlation of knocking characteristics of fuels in an engine having a hemispherical combustion chamber

Correlation of knocking characteristics of fuels in an engine having a hemispherical combustion chamber

Date: July 1, 1940
Creator: Rothrock, A M & Biermann, Arnold E
Description: Data are presented to show the effects of inlet-air pressure, inlet-air temperature, and compression ratio on the maximum permissible performance obtained with having a hemispherical-dome combustion chamber. The five aircraft-engine fuels used have octane numbers varying from 90 to 100 plus 2 ml of tetraethyl lead per gallon. The data were obtained on a 5 1/4-inch by 4 3/4-inch liquid-cooled engine operating at 2,500 r.p.m. The compression ratio was varied from 6.0 to 8.9. The inlet-air temperature was varied from 110 to 310 F. For each set of conditions, the inlet-air pressure was increased until audible knock occurred and then reduced 2 inches of mercury before data were recorded. The results for each fuel can be correlated by plotting the calculated end-gas density factor against the calculated end-gas temperature. Measurements of spark-plugs, cutting off the switch to one spark plug lowered the electrode temperature of that plug from a value of 1,365 F to a value of 957 F. The results indicate that the surface temperatures of combustion-chamber areas which become new sources of ignition markedly increase after ignition.
Contributing Partner: UNT Libraries Government Documents Department
Cyclic stress-strain studies of metals in torsion

Cyclic stress-strain studies of metals in torsion

Date: December 1, 1940
Creator: Paul, D A & Moore, R L
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Damping formulas and experimental values of damping in flutter models

Damping formulas and experimental values of damping in flutter models

Date: February 1, 1940
Creator: Coleman, Robert P
Description: The problem of determining values of structural damping for use in flutter calculations is discussed. The concept of equivalent viscous damping is reviewed and its relation to the structural damping coefficient g introduced in NACA Technical Report No. 685 is shown. The theory of normal modes is reviewed and a number of methods are described for separating the motions associated with different modes. Equations are developed for use in evaluating the damping parameters from experimental data. Experimental results of measurements of damping in several flutter models are presented.
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The development of electrical strain gages

The development of electrical strain gages

Date: January 1, 1940
Creator: De Forest, A V & Leaderman, H
Description: The design, construction, and properties of an electrical-resistance strain gage consisting of fine wires molded in a laminated plastic are described. The properties of such gages are discussed and also the problems of molding of wires in plastic materials, temperature compensation, and cementing and removal of the gages. Further work to be carried out on the strain gage, together with instrument problems, is discussed.
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Drag determination of the forward component of a tricycle landing gear

Drag determination of the forward component of a tricycle landing gear

Date: December 1, 1940
Creator: Harmon, Hubert N
Description: Wind-tunnel tests were performed to determine the drag of the front-wheel arrangements of several types of tricycle landing gear. One wheel was tested in arrangements to simulate both nonretracted and partially retracted types. The landing gears were tested in conjunction with a fuselage, and the effects of wheel extension and longitudinal location were determined. The drag changed very little with either longitudinal location or wheel extension for the landing gear with the lowest drag; a completely faired landing gear of the wheelspan, single-strut type. The drag of the trouser-type landing gear increased considerably, however, with an increase in the wheel extension. The wheel of the unaired retractable landing gear was at least one-half retracted into the fuselage before the drag became less than that of the best nonretracted landing gear. The drag per unit frontal area of the landing gears of the present tests was about the same as that found for similar landing gears in earlier tests.
Contributing Partner: UNT Libraries Government Documents Department
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