FAA Powerplant Written Practice Test

During visual inspection while overhauling an engine, if the piston heads are depressed, this indicates what?

1. Engine misalignment

2. Wear and tear

3. Detonation had occurred

4. Contaminated fuel

The correct answer is: Detonation had occurred

When piston heads are found to be depressed during a visual inspection of an engine overhaul, this condition is indicative of detonation having occurred. Detonation refers to an uncontrolled explosion in the combustion chamber, which can result from various factors including excessive engine temperatures, incorrect fuel octane ratings, or improper ignition timing. This explosive combustion can create shock waves that damage the piston, leading to visible deformation such as depressed piston heads. In the context of engine reliability and safety, recognizing the signs of detonation is crucial because it reflects not just upon the current state of the piston but also upon the overall performance and health of the engine. Understanding this helps technicians to identify potentially severe issues that may have led to the abnormal combustion process and addresses the need for corrective measures in engine maintenance or operation. The other options do relate to engine wear or performance issues but do not specifically address the visual indication of depressed piston heads as a symptom of detonation.