A 2000-horsepower propeller dynamometer has been used in the Langley 16—foot high—speed tunnel to make tests of a full—scale two—blade NACA 10-(3)(08)-03 propeller for a range of blade angles from 20° to 55° at airspeeds up to 500 miles per hour. The ability of the test equipment to measure propeller characteristics accurately is confirmed by the good agreement of the results of these tests with results obtained from a theoretical analysis and from previous tests made in other wind tunnels.nThe two-blade NACA 10-(3)(08)-03 propeller is very efficient at speeds where the adverse effects of compressibility are small. The maxi¬mum efficiency of 0.93, which was attained over a range of advance ratio from 1.3 to 2.0 for a constant rotational speed of 1350 revolutions per minute, reflects the importance of designing for a minimum induced—energy-loss loading and the use of efficient airfoil sections from the spinner surface to the propeller tip. When the helical—tip Mach number is increased from 0.90 to 1.15, the corresponding loss in propeller efficiency is about 21 percent at a blade angle of 450.
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