Results are given of drag tests of 4/9-scale model radial air-cooled engine nacelles made as a part of a general investigation of wing-nacelle-propeller interference. A small nacelle of the type commonly used with exposed engine cylinders was tested with various forms of cowling over the cylinders. The effects of cowling-ring position and of angle of ring chord to the thrust line were investigated. An N.A.C.A. cowled nacelle and a smooth body were also tested. The results are given at 50, 75, and 100 miles per hour for -5 degrees, 0 degrees, 5 degrees, 10 degrees, 15 degrees angle of pitch.
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