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Experiments With a Counter-Propeller

Description: This note describes tests made at Stanford University on a four-blade fixed counter-propeller in combination with a two-blade rotating propeller. It is shown that the efficiency of the normal form, well-designed air propeller can be increased about two percent over the full working range by the addition of fixed counter-propeller blades.
Date: March 1933
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Tandem Air Propellers

Description: "Tests of 2-blade, adjustable-pitch, counter rotating tandem model propellers, adjusted to absorb equal power at maximum efficiency, were made at Stanford University. The characteristics, for 15 degrees, 25 degrees, 35 degrees, and 45 degrees pitch settings at 0.75 R of the forward propeller and for 8-1/2 percent, 15 percent, and 30 percent diameter spacings, were compared with those of 2-blade and 4-blade propellers of the same blade form" (p. 1).
Date: February 1939
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Tandem Air Propellers

Description: Report discussing tests of 2-blade, adjustable-pitch, counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency. The characteristics at several pitch settings and diameter spacings were compared with 2-blade and 4-blade propellers. Tandem propellers were found to have an advantage over single propellers at higher pitch settings.
Date: August 1937
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Tandem Air Propellers - 2

Description: Report presenting testing of three-blade, adjustable-pitch counterrotating tandem model propellers adjusted to absorb equal power at maximum efficiency of the combination. The aerodynamic characteristics were determined for a variety of blade-angle settings and diameter spacings. At maximum efficiency, the tandem propellers absorb about double the power of the three-blade propellers and about 8 percent more power than six-blade propellers with the pitch of the forward propeller of the tandem combination.
Date: August 1941
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Tandem Air Propellers - 2

Description: "Tests of three-blade, adjustable-pitch counterrotating tandem model propellers, adjusted to absorb equal power at maximum efficiency of the combination, were made at Stanford University. The aerodynamic characteristics, for blade-angle settings of 15, 25, 35, 45, 55, and 65 degrees at 0.75R of the forward propeller and for diameters spacings of 8-1/2, 15 and 30% were compared with those of three-blade and six-blade propellers of the same blade form. It was found that, in order to realize the condition of equal power at maximum efficiency, the blade angles for the rear propeller must be generally less than for the forward propeller, the difference increasing the blade angle" (p. 1).
Date: October 1939
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Report on Tests of Metal Model Propellers in Combination With a Model VE-7 Airplane

Description: This report, prepared at the request of the NACA, describes tests of three metal model propellers, in a free air stream and in front of a model of a VE-7 airplane. The effect of introducing the model airplane is shown to be an increase in thrust and power coefficients and efficiency at small slip, and a decrease in the same at large slip.
Date: August 1926
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Test of an Adjustable Pitch Model Propeller at Four Blade Settings

Description: "This note describes tests of an adjustable blade metal model propeller, both in a free wind stream and in combination with a model fuselage, at four settings of the blades. The model propeller is designed for a uniform nominal pitch/diameter ratio of .7 and the blade settings used correspond to nominal pitch/diameter ratios of .5, .7, .9, and 1.1 at the .6 radius. The tests show that propellers of this type may be considerably changed in setting from the designed pitch angles and yet give excellent performance" (p. 1).
Date: February 1930
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Comparison of tests on air propellers in flight with wind tunnel model tests on similar forms

Description: From Summary: "The purpose of this investigation was to determine the performance, characteristics, and coefficients of full-sized air propellers in flight and to compare these results with those derived from wind-tunnel tests on reduced scale models of similar geometrical form. The full-scale equipment comprised five propellers in combination with a VE-7 airplane and Wright E-4 engine. This part of the work was carried out at the Langley Memorial Aeronautical Laboratory, between May 1 and August 24, 1924, and was under the immediate charge of Mr. Lesley."
Date: 1926
Creator: Durand, W. F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Air propellers in yaw

Description: Report presents the results of tests conducted at Stanford University of a 3-foot model propeller at four pitch settings and at 0 degree, 10 degrees, 20 degrees, and 30 degrees yaw.
Date: 1937
Creator: Lesley, E. P.; Worley, George F. & Moy, Stanley
Partner: UNT Libraries Government Documents Department

Experimental Research on Air Propellers, 3

Description: Report presents the results of wind tunnel tests of propellers that examined the influence of the following characteristics: (1) nominal pitch ratio 1.3 combined with a certain number of the more common or standard forms and proportions; (2) driving face slightly rounded or convex; (3) change in the location of the maximum thickness ordinate of the blade section; (4) pushing forward the leading edge of the blade, thus giving a rounded convex surface on the leading side of the driving face. (5) a series of values for the constant "angle of attack" in forming propellers with radially increasing pitch. In accordance with these purposes tests were carried out on 28 propellers.
Date: 1920
Creator: Durand, W. F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Experimental Research on Air Propellers, 5

Description: In previous reports on experimental research on air propellers, by W. F. Durand and E. P. Lesley, as contained in the National Advisory Committee for Aeronautics reports nos. 14, 30, and 64, the investigations were made progressively and each without reference to results given in preceding reports and covering only information relating to forms perhaps adjacent in geometrical form and proportion. This report is a review of the entire series of results of the preceding reports with a view of examining through graphical and other appropriate means the nature of the history of the characteristics of operation as related to the systematic variations in characteristics of forms, etc., through the series of such characteristics.
Date: 1923
Creator: Durand, W. F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Experimental Research on Air Propellers, 4

Description: This report states the results of investigations made upon numerous propeller models at the request of the Subcommittee on Aerodynamics, and contains valuable data for those interested in the design of air propellers.
Date: 1921
Creator: Durand, W. F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Tests on Air Propellers in Yaw

Description: This report contains the results of tests to determine the thrust (pull) and torque characteristics of air propellers in movement relative to the air in a line oblique to the line of the shaft, and specifically when such angle of obliquity is large, as in the case of helicopter flight with the propeller serving for both sustentation and traction.
Date: 1923
Creator: Durand, W. F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Tests of Five Metal Model Propellers With Various Pitch Distributions in a Free Wind Stream and in Combination With Model VE-7 Fuselage

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" (p. 501).
Date: 1930
Creator: Lesley, E. P. & Reid, Elliott G.
Partner: UNT Libraries Government Documents Department

The Effect of Slipstream Obstructions on Air Propellers

Description: "The screw propeller on airplanes is usually placed near other objects, and hence its performance may be modified by them. Results of tests on propellers free from slip stream obstructions, both fore and aft, are therefore subject to correction, for the effect of such obstructions and the purpose of the investigation was to determine the effect upon the thrust and torque coefficients and efficiency, for previously tested air propellers, of obstructions placed in the slip stream, it being realized that such previous tests had been conducted under somewhat ideal conditions that are impracticable of realization in flight" (p. 313).
Date: 1924
Creator: Lesley, E. P. & Woods, B. M.
Partner: UNT Libraries Government Documents Department

A New Method for the Prediction of Airplane Performance

Description: A new method for the prediction of airplane performance in level and climbing flight, together with complete information regarding propeller speeds, is described in this report. Developed from Bairstow's system and making use of American absolute coefficients, this method has advantages of simplicity and brevity.
Date: February 1929
Creator: Lesley, E. P. & Reid, E. G.
Partner: UNT Libraries Government Documents Department

Propeller Tests to Determine the Effect of Number of Blades at Two Typical Solidities

Description: "Propellers with equal total blade area, but with different numbers, were tested at Stanford University. The tests show generally that, for equal total blade area, propellers with the larger number of blades absorb the greater power and, provided hubs have equal drag, develop the higher efficiency. It is shown that the differences found are in agreement, qualitatively, with what might be predicted from simple blade-element theory" (p. 1).
Date: April 1939
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Experimental Research on Air Propellers, 2

Description: This report is a continuation of NACA Technical Report 14. It presents the results of an experimental investigation on the performance of air propellers which was divided into five parts, as follows: (1) Tests under conditions of flight on 16 model propellers of different forms, sections, or pitch ratios from those of Technical Report 14; (2) Tests under conditions of flight on one model propeller of variable pitch; (3) Tests under conditions of flight on three sets of right and left hand model propellers in series; (4) Tests on 12 model propellers to determine brake effect or negative thrust at negative slip; (5) Standing thrust and power tests of 67 model propellers.
Date: 1919
Creator: Durand, William F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Test of a Model Propeller With Symmetrical Blade Sections

Description: "This report, prepared at the request of NACA, gives the results of tests on a model propeller having blade sections with form of Gottingen airfoil no. 409. The model is shown to have a dynamic pitch practically equal to the nominal or geometrical pitch, and a somewhat higher efficiency but lower coefficient than would be expected of a propeller of more conventional sections" (p. 1).
Date: September 1926
Creator: Lesley, E. P.
Partner: UNT Libraries Government Documents Department

Comparison of Model Propeller Tests With Airfoil Theory

Description: "The purpose of the investigation covered by this report was the examination of the degree of approach which may be anticipated between laboratory tests on model airplane propellers and results computed by the airfoil theory, based on tests of airfoils representative of successive blade sections. It is known that the corrections of angles of attack and for aspect ratio, speed, and interference rest either on experimental data or on somewhat uncertain theoretical assumptions. The general situation as regards these four sets of corrections is far from satisfactory, and while it is recognized that occasion exists for the consideration of such corrections, their determination in any given case is a matter of considerable uncertainty" (p. 237).
Date: 1925
Creator: Durand, William F. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department

The Reduction of Airplane Flight Test Data to Standard Atmosphere Conditions

Description: This report was prepared for the National Advisory Committee for Aeronautics in order to supply the need of practical methods of reducing observed performance to standard conditions with a minimum of labor. The first part gives a very simple approximate method of reducing performance in climb, and is particularly adapted to work not requiring extreme accuracy. The second part gives a somewhat more elaborate and more accurate method which is well suited to general flight test reduction. The third part gives the conventional method of calibrating air-speed indicators and reducing the indicated speeds to true air speeds. An appendix gives working tables and charts for the standard atmosphere. (author).
Date: 1925
Creator: Diehl, Walter S. & Lesley, E. P.
Partner: UNT Libraries Government Documents Department