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National advisory committee aeronautics Report no. 328. Water pressure distribution on a twin-float seaplane,
Jan., 193o.]
I~OOK R ~ V i E W S .
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supercharger capacities, obtained by driving a Roots type supercharger at 1.615, 1.957, 2.4, and 3 times engine speed, were used to m a i n t a i n sea-level pressure at the carburetor to altitudes of 7,ooo, I 1,5oo, 17,ooo, and 22,ooo feet, respectively. T h e performance of t h e airplane in climb and in level flight was determined for each of the four supercharger drive ratios and for the unsupercharged condition. The engine power was measured during these tests by means of a calibrated propeller. It was found t h a t v m y little sacrifice in sea-level performance was experienced with the larger supercharger drive ratios as compared with perfornlance obtained + h e n using the smaller drive ratios. The results indicate t h a t further increase in supercharger capacity over t h a t obtained when using the 3 : I drive ratio would give a slight increase in ceiling and in high altitude performance, but would considerably impair the performance for an appreciable distance below the critical altitude. As the supercharger capacity was increased, the height at which sea-level high speeds could be equaled or improved became a larger percentage of the maximunl height of operation of the airplane. Report No. 328. Water Pressure Distribution on a Twin-Float Seaplane, by F. L. Thompson. 18 pages, illustrations, quarto. Washington, Government Printing Office, I929. Price ten cents. The investigation reported herein was conducted by the National Advisory Committee for Aeronautics a t t h e request of the Bureau of Aeronautics, Navy Department. This is the second of a series of investigations to determine water pressure distribution on various types of seaplane floats and hulls, and was conducted on a twin-float seaplane. It consisted of measuring water pressures and accelerations on a TS-I seaplane during numerous landing and taxying maneuvers at various speeds and angles. The results of this investigation show t h a t water pressures as great as Io lb. per sq. in. may occur at the step in various maneuvers and t h a t pressures of approximately the same magnitude occur at the stern and near the bow in hard pancake landings with the stern well down. At other parts of the float the pressures are less and are usually zero or slightly negative for sonm distance abaft the step. A maximnm negative pressure of 0.87 lb. per sq. in. was measured immediately abaft the step. The maximum positive pressures have a duration of approximately one-twentieth to one one-hundredth second at a n y given location and are distributed over a very limited area at any particular instant. The greatest accelerations measured normal to the t h r u s t line at the C.G. occurred in pancake landings, and a nlaximum of 4.3 g. was recorded. Approximate load distribution curves for the worst landing conditions are derived from the data obtained to serve as a guide in static tests.
PUBLICATIONS RECEIVED. A Source Book in Mathematics, by David Eugene Smith. First edition. 7oi pages, illustrations, portraits, 8vo. New York, McGraw-Hill Book Company, 1929. Price $5.oo.
I~OOK R ~ V i E W S .
x47
supercharger capacities, obtained by driving a Roots type supercharger at 1.615, 1.957, 2.4, and 3 times engine speed, were used to m a i n t a i n sea-level pressure at the carburetor to altitudes of 7,ooo, I 1,5oo, 17,ooo, and 22,ooo feet, respectively. T h e performance of t h e airplane in climb and in level flight was determined for each of the four supercharger drive ratios and for the unsupercharged condition. The engine power was measured during these tests by means of a calibrated propeller. It was found t h a t v m y little sacrifice in sea-level performance was experienced with the larger supercharger drive ratios as compared with perfornlance obtained + h e n using the smaller drive ratios. The results indicate t h a t further increase in supercharger capacity over t h a t obtained when using the 3 : I drive ratio would give a slight increase in ceiling and in high altitude performance, but would considerably impair the performance for an appreciable distance below the critical altitude. As the supercharger capacity was increased, the height at which sea-level high speeds could be equaled or improved became a larger percentage of the maximunl height of operation of the airplane. Report No. 328. Water Pressure Distribution on a Twin-Float Seaplane, by F. L. Thompson. 18 pages, illustrations, quarto. Washington, Government Printing Office, I929. Price ten cents. The investigation reported herein was conducted by the National Advisory Committee for Aeronautics a t t h e request of the Bureau of Aeronautics, Navy Department. This is the second of a series of investigations to determine water pressure distribution on various types of seaplane floats and hulls, and was conducted on a twin-float seaplane. It consisted of measuring water pressures and accelerations on a TS-I seaplane during numerous landing and taxying maneuvers at various speeds and angles. The results of this investigation show t h a t water pressures as great as Io lb. per sq. in. may occur at the step in various maneuvers and t h a t pressures of approximately the same magnitude occur at the stern and near the bow in hard pancake landings with the stern well down. At other parts of the float the pressures are less and are usually zero or slightly negative for sonm distance abaft the step. A maximnm negative pressure of 0.87 lb. per sq. in. was measured immediately abaft the step. The maximum positive pressures have a duration of approximately one-twentieth to one one-hundredth second at a n y given location and are distributed over a very limited area at any particular instant. The greatest accelerations measured normal to the t h r u s t line at the C.G. occurred in pancake landings, and a nlaximum of 4.3 g. was recorded. Approximate load distribution curves for the worst landing conditions are derived from the data obtained to serve as a guide in static tests.
PUBLICATIONS RECEIVED. A Source Book in Mathematics, by David Eugene Smith. First edition. 7oi pages, illustrations, portraits, 8vo. New York, McGraw-Hill Book Company, 1929. Price $5.oo.