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  Partner: UNT Libraries Government Documents Department
 Decade: 1930-1939
 Collection: Technical Report Archive and Image Library
Tests of Airfoils Designed to Delay the Compressibility Burble

Tests of Airfoils Designed to Delay the Compressibility Burble

Date: June 1, 1939
Creator: Stack, John
Description: Development of airfoil sections suitable for high-speed applications has generally been difficult because little was known of the flow phenomenon that occurs at high speeds. A definite critical speed has been found at which serious detrimental flow changes occur that lead to serious losses in lift and large increases in drag. This flow phenomenon, called the compressibility burble, was originally a propeller problem, but with the development of higher speed aircraft serious consideration must be given to other parts of the airplane. Fundamental investigations of high-speed airflow phenomenon have provided new information. An important conclusion of this work has been the determination of the critical speed, that is, the speed at which the compressibility burble occurs. The critical speed was shown to be the translational velocity at which the sum of the translational velocity and the maximum local induced velocity at the surface of the airfoil or other body equals the local speed of sound. Obviously then higher critical speeds can be attained through the development of airfoils that have minimum induced velocity for any given value of the lift coefficient. Presumably, the highest critical speed will be attained by an airfoil that has uniform chordwise distribution of induced velocity ...
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Tests of an N.A.C.A. 23012 Airfoil with a slotted deflector flap

Tests of an N.A.C.A. 23012 Airfoil with a slotted deflector flap

Date: April 1, 1939
Creator: House, R O
Description: Section aerodynamic characteristics of a large-chord N.A.C.A. 23012 airfoil with a slotted deflector flap were obtained in the N.A.C.A. 7- by 10-foot wind tunnel. The characteristics of an N.A.C.A. slotted flap and of a simple split flap are included for comparison. The slotted deflector flap was found to have a somewhat lower maximum lift coefficient and somewhat higher drag at high lift coefficients than the N.A.C.A. slotted flap. The high drag of the open slot with the deflector flap neutral indicates that the slot should be closed for this condition.
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Tests of five full-scale propellers in the presence of a radial and a liquid-cooled engine nacelle, including tests of two spinners

Tests of five full-scale propellers in the presence of a radial and a liquid-cooled engine nacelle, including tests of two spinners

Date: January 1, 1938
Creator: Biermann, David
Description: Wind-tunnel tests are reported of five 3-blade 10-foot propellers operating in front of a radial and a liquid-cooled engine nacelle. The range of blade angles investigated extended from 15 degrees to 45 degrees. Two spinners were tested in conjunction with the liquid-cooled engine nacelle. Comparisons are made between propellers having different blade-shank shapes, blades of different thickness, and different airfoil sections. The results show that propellers operating in front of the liquid-cooled engine nacelle had higher take-off efficiencies than when operating in front of the radial engine nacelle; the peak efficiency was higher only when spinners were employed. One spinner increased the propulsive efficiency of the liquid-cooled unit 6 percent for the highest blade-angle setting investigated and less for lower blade angles. The propeller having airfoil sections extending into the hub was superior to one having round blade shanks. The thick propeller having a Clark y section had a higher take-off efficiency than the thinner one, but its maximum efficiency was possibly lower. Of the three blade sections tested, Clark y, R.A.F. 6, and NACA 2400-34, the Clark y was superior for the high-speed condition, but the R.A.F. 6 excelled for the take-off condition.
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Tests of five metal model propellers with various pitch distributions in a free wind stream and in combination with model VE-7 fuselage

Tests of five metal model propellers with various pitch distributions in a free wind stream and in combination with model VE-7 fuselage

Date: January 1, 1930
Creator: Lesley, E P
Description: This report describes the tests of five adjustable blade metal model propellers both in a free wind stream and in combination with a model fuselage with stub wings. The propellers are of the same form and cross section but have variations in radial distributions of pitch. By making a survey of the radial distribution of air velocity through the propeller plane of the model fuselage it was found that this velocity varies from zero at the hub center to approximately free stream velocity at the blade tip. The tests show that the efficiency of a propeller when operating in the presence of the airplane is, over the working range, generally less than when operating in a free wind stream, but that a propeller with a radial distribution of pitch of the same nature as the radial distribution of air velocity through the propeller plane suffers the smallest loss in efficiency.
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Tests of large airfoils in the propeller research tunnel, including two with corrugated surfaces

Tests of large airfoils in the propeller research tunnel, including two with corrugated surfaces

Date: January 1, 1930
Creator: Wood, Donald H
Description: This report gives the results of the tests of seven 2 by 12 foot airfoils (Clark Y, smooth and corrugated, Gottingen 398, N.A.C.A. M-6, and N.A.C.A. 84). The tests were made in the propeller research tunnel of the National Advisory Committee for Aeronautics at Reynolds numbers up to 2,000,000. The Clark Y airfoil was tested with three degrees of surface smoothness. Corrugating the surface causes a flattening of the lift curve at the burble point and an increase in drag at small flying angles.
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Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 24

Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 24

Date: January 1, 1932
Creator: Jacobs, Eastman N
Description: This note is the fifth of a series covering an investigation of a number of related airfoils. It presents the results obtained from tests of a group of six low-cambered airfoils in the variable-density wind tunnel. The mean camber lines are identical for the six airfoils and are of such a form that the maximum mean camber is 2 per cent of the chord and is at a position 0.4 of the chord behind the loading edge. The airfoils differ in thickness only, the maximum-thickness/chord ratios being 0.06, 0.09, 0.12, 0.15, 0.18, and 0.21. The results have been presented in the form of both infinite and finite aspect-ratio characteristics. The values of C(sub L) max/C(sub d) degrees min for this group of airfoils are among the highest thus far obtained, the minimum profile drags being approximately equal to those for the symmetrical series of corresponding thickness, while the maximum lift coefficients are considerably higher.
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Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 43 and 63

Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 43 and 63

Date: September 1, 1931
Creator: Jacobs, Eastman N
Description: This note is one of a series covering an investigation of a family of related airfoils. It gives in preliminary form the results obtained from tests in the N.A.C.A. Variable-Density Wind Tunnel of two groups of six airfoils each. One group, the 43 series, has a maximum mean camber of 4 per cent of the chord at a position 0.3 of the chord from the leading edge; the other group, the 63 series, has a maximum mean camber of 6 per cent of the chord at the same position. The members within each group differ only in maximum thickness, the maximum thickness/chord ratios being:0.06, 0.09, 0.12, 0.15, 0.18, and 0.21. The results are analyzed with a view to indicating the variation of the aerodynamic characteristics with profile thickness for airfoils having a certain mean camber line.
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Tests of N.A.C.A. airfoils in the variable density wind tunnel Series 44 and 64

Tests of N.A.C.A. airfoils in the variable density wind tunnel Series 44 and 64

Date: December 1, 1931
Creator: Jacobs, Eastman N
Description: This note is one of a series covering an investigation of a number of related airfoils. It presents the results obtained from tests in the N.A.C.A. Variable Density Wind Tunnel of two groups of six airfoils each. One group, the 44 series, has a maximum mean camber of 4 percent of the chord at a position 0.4 of the chord behind the leading edge and the other group, the 64 series, has a maximum mean camber of 6 percent of the chord at the same position. The members within each group differ only in maximum thickness, the maximum thickness/chord ratios being: 0.06, 0.09, 0.12, 0.15, 0.18, and 0.21. The results are analyzed with a view to indicating the variation of the aerodynamic characteristics with profile thickness for airfoils having a certain mean camber line form.
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Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 45 and 65

Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 45 and 65

Date: September 1, 1931
Creator: Jacobs, Eastman N
Description: This note is one of a series covering an investigation of a number of related airfoils. It presents the results obtained from tests in N.A.C.A. Variable-Density Wind Tunnel of two groups of six airfoils each. One group, the 45 series, has a maximum mean camber of 4 per cent of the chord at a position 0.5 of the chord behind the leading edge, and the other group, the 65 series, has a maximum mean camber of 6 per cent of the chord at the same position. The members within each group differ only in maximum thickness, the maximum thickness/chord ratios being: 0.06, 0.09, 0.12, 0.15, 0.18, and 0.21. The results are analyzed with a view to indicating the variation of the aerodynamic characteristics with profile thickness for airfoils having a certain mean camber line form.
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Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 230.

Tests of N.A.C.A. airfoils in the variable-density wind tunnel Series 230.

Date: May 1, 1936
Creator: Jacobs, Eastman N
Description: The results of tests of six airfoils having the N.A.C.A. 230 mean line and varying in thickness from 0.06c to 0.21c are presented. These results agree with previous findings in showing that aerodynamically the best section is one of moderate thickness. The data are of value mainly in connection with the design of tapered wings having sections based on the N.A.C.A. 230 mean line.
Contributing Partner: UNT Libraries Government Documents Department