Aircraft supplied cooling baffles Low pressure area High pressure area Ram air Cowl flaps Cooling air exit Figure 6-55. Differential air cooling.  Figure 6-56. A cylinder head and fins.  Engine Cylinder Cooling Fin Inspection The cooling fins are of the utmost importance to the  cooling system, since they provide a means of transferring  the cylinder heat to the air. Their condition can mean the  difference between adequate or inadequate cylinder cooling.  The fins are inspected at each regular inspection. Fin area  is the total area (both sides of the fin) exposed to the air.  During the inspection, the fins should be examined for  cracks and breaks.  [Figure 6-56]  Small cracks are not a  reason for cylinder removal. These cracks can be filled or  even sometimes stop-drilled to prevent any further cracking.  Rough or sharp corners on fins can be smoothed out by  filing, and this action eliminates a possible source of new  cracks. However, before reprofiling cylinder cooling fins,  consult the manufacturer’s service or overhaul manual for  the allowable limits. 6-37