A Course for Ground Engineers: VIII.—Hints on the Inspection and Complete Overhaul of Engines for Applicants for “D” Licence

SMALL surface cracks in some cast pistons are often present from the date of manufacture, and are due to the casting stresses in the uneven sections. Provided the piston is not subject to considerable distortion in service, these cooling cracks do not increase or lead to failure by fatigue. Actual experience of the design is necessary, however, before a decision can be given as to the safety of a cracked piston, and it must be remembered that the holder of a “C” licence may not have the facilities for so careful an examination of the piston during top overhaul.