STARE AT A GENERAL AVIATION AIRPLANE HEAD ON-PARTICULARLY A Carbon Cub-and you'll see one or more openings in the fuselage next to and perhaps under the propeller that seem to give the airplane a face. Whimsical as they may appear, the openings serve an important role in cooling a piston-powered engine. As an airplane moves through the air, the relative wind in the opposite direction flows over the airplane, but also into the engine compartment by means of air intakes. That air is directed to the top of the engine by baffles, where it cools the cylinders, and then is directed by more baffling to the bottom of the cowling, where it exits to join the slipstream. In some airplanes, the air exits through vents in the top of the cowling. When the airplane is not moving, the air intake serves no purpose. But it is an attractive portal of entry for birds and bees and wasps, so pilots plug intakes with foam cowl plugs to prevent an invasion-or at least discourage one. Birds can be particularly determined to nest inside an airplane, and for good reason: An engine compartment provides a quiet shelter-at least until you start the preflight.
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