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  Partner: UNT Libraries Government Documents Department
 Collection: Technical Report Archive and Image Library
Tandem Air Propellers

Tandem Air Propellers

Date: August 1, 1937
Creator: Lesley, E.P.
Description: Tests of 2-blade, adjustable-pitch, counterrotating 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%, 15% and 30% diameter spacings, were compared with those of 2-blade and 4-blade propellers of the same blade form. The tests showed that the efficiency of the tandem propellers was from 0.5% to 4% greater than that of a 4-blade propeller and, at the high pitch settings, not appreciable inferior to that of a 2-blade propeller. It was found that the rear tandem propeller should be set at a pitch angle slightly less than that of the forward propeller to realize the condition of equal power at maximum efficiency. Under this condition the total power absorbed by the tandem propellers was from 3% to 9% more than that absorbed by the 4-blade propeller and about twice that absorbed by a 2-blade propeller.
Contributing Partner: UNT Libraries Government Documents Department
Tandem Air Propellers - II

Tandem Air Propellers - II

Date: August 1, 1941
Creator: Lesley, E P
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Tandem Air Propellers - II

Tandem Air Propellers - II

Date: October 1, 1939
Creator: Lesley, E. P.
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. The tests showed that, at maximum efficiency, the tandem propellers absorb about double the power of three-blade propellers and about 8% more power than six-blade propellers having the pitch of the forward propeller of the tandem combination. The maximum efficiency of the tandem propellers was found to be from 2-15% greater than for six-blade propellers, the difference varying directly with blade angle. It was also found that the maximum efficiency of the tandem propellers was greater than that of a three-blade propeller for blade angles at 0.75R of 25 degrees or more. The difference ...
Contributing Partner: UNT Libraries Government Documents Department
Tank investigation of a powered dynamic model of a large long-range flying boat

Tank investigation of a powered dynamic model of a large long-range flying boat

Date: January 1, 1947
Creator: Parkinson, John B; Olson, Roland E & Harr, Marvin I
Description: Principles for designing the optimum hull for a large long-range flying boat to meet the requirements of seaworthiness, minimum drag, and ability to take off and land at all operational gross loads were incorporated in a 1/12-size powered dynamic model of a four-engine transport flying boat having a design gross load of 165,000 pounds. These design principles included the selection of a moderate beam loading, ample forebody length, sufficient depth of step, and close adherence to the form of a streamline body. The aerodynamic and hydrodynamic characteristics of the model were investigated in Langley tank no. 1. Tests were made to determine the minimum allowable depth of step for adequate landing stability, the suitability of the fore-and-aft location of the step, the take-off performance, the spray characteristics, and the effects of simple spray-control devices. The application of the design criterions used and test results should be useful in the preliminary design of similar large flying boats.
Contributing Partner: UNT Libraries Government Documents Department
Tank investigation of a powered dynamic model of a large long-range flying boat - Langley tank model 180

Tank investigation of a powered dynamic model of a large long-range flying boat - Langley tank model 180

Date: March 1, 1947
Creator: Parkinson, John B; Olson, Roland E & Haar, Marvin I
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Tank investigation of a series of related hydro-skis as load-alleviation devices for landing a seaplane in waves

Tank investigation of a series of related hydro-skis as load-alleviation devices for landing a seaplane in waves

Date: December 19, 1956
Creator: Carter, Arthur W; Morse, Archibald E , Jr & Woodward, David R
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Tank Investigation of the EDO Model 142 Hydro-Ski Research Airplane

Tank Investigation of the EDO Model 142 Hydro-Ski Research Airplane

Date: January 1, 1951
Creator: Ramsen, John A.; Wadlin, Kenneth L. & Gray, George R.
Description: A tank investigation has been conducted of a 1/10-size powered-dynamic model of the Edo model 142 hydra-ski research airplane. The results of tests of two configurations are presented: One included a large ski and a ski well; the other, a small ski without a well. Water take-offs would be possible with the available thrust for either configuration: however, the configuration with the large ski emerged sooner and had less resistance from ski emergence until take-off. Longitudinal stability and landing behavior in smooth water were satisfactory for both configurations. Some alteration to the design of the tail would be desirable in order to reduce the spray loads.
Contributing Partner: UNT Libraries Government Documents Department
Tank Investigation of the Grumman JRF-5 Airplane Equipped with Twin Hydro-Skis TED No. NACA DE 357

Tank Investigation of the Grumman JRF-5 Airplane Equipped with Twin Hydro-Skis TED No. NACA DE 357

Date: January 1, 1951
Creator: Ramsen, John A. & Gray, George R.
Description: A tank investigation has been conducted on a 1/8-size powered dynamic model of the Grumman JRF-5 airplane equipped with twin hydro-skis. The results of tests using two types of skis are presented: one had vertical sides joining the top surface to the chine; the other had the top surface faired to the chine to eliminate the vertical sides. Both configurations had satisfactory longitudinal stability although the model had a slightly greater stable elevator range available when the skis without the vertical sides were attached. Free model tests indicated no instability present when one ski emerged before the other. Considerable excess thrust was available at all speeds with either type of skis. A hump gross load-resistance ratio of 3.37 was obtained with the skis with the vertical sides and 3.53 with the other skis. Landing behavior in smooth water with yaw up to 15deg and roll up to 15deg in opposite directions was satisfactory with either type of skis.
Contributing Partner: UNT Libraries Government Documents Department
Tank investigation of the Grumman JRF-5 airplane fitted with hydro-skis suitable for operation on water, snow, and ice

Tank investigation of the Grumman JRF-5 airplane fitted with hydro-skis suitable for operation on water, snow, and ice

Date: June 12, 1950
Creator: Wadlin, Kenneth L & Ramsen, John A
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Tank investigation of the Grumman JRF-5 airplane with a single hydro-ski and an extended afterbody

Tank investigation of the Grumman JRF-5 airplane with a single hydro-ski and an extended afterbody

Date: August 7, 1951
Creator: Ramsen, John A & Gray, George R
Description: None
Contributing Partner: UNT Libraries Government Documents Department