The Cowling of Radial Engines: An Extended Series of Experiments by the Chance Vought and Pratt and Whitney Group

(7) Separate Openings in the Skirt.—A number of equally spaced rectangular openings were cut in the skirt. Openings of this sort could be closed by a rotating shutter. Separate openings of this type were found to be less effective in producing flow and considerably less efficient. Such openings might be closed by doors opening in the manner of flaps. This last arrangement is somewhat less effective than trailing‐edge flaps and also less efficient. Nevertheless, doors of this type may be made to produce large increases in flow. Tests with varying number and sizes of doors disclosed that, if the doors are placed too far apart, good cooling will be obtained for cylinders immediately in front of the doors, but the cooling of the other cylinders will be much less. Therefore, two or three doors are likely to be insufficient, and the use of four or more is preferable.