FAA Powerplant Written Practice Test

What type of defect is likely to cause a hot spot on a reciprocating engine cylinder?

1. Excessive oil leakage

2. Broken cooling fins

3. Cracks in the cylinder wall

4. Fuel contamination

The correct answer is: Broken cooling fins

The presence of broken cooling fins on a reciprocating engine cylinder is likely to create a hot spot because the cooling fins are designed to enhance the dissipation of heat from the cylinder. When these fins are damaged or missing, the cylinder cannot effectively transfer heat away, leading to localized areas of excessive heat, known as hot spots. This can result in overheating, which may contribute to further damage or failure of the engine components. In contrast, excessive oil leakage may lead to oil accumulation and potential lubrication issues, but it does not directly affect the heat dissipation capability of the cylinder. Cracks in the cylinder wall can exacerbate issues related to compression and structural integrity, but they don't specifically indicate a failure in heat exchange like broken fins do. Fuel contamination primarily affects combustion efficiency and performance, rather than directly causing changes in temperature distribution across the cylinder. Thus, while other options may relate to engine performance and integrity, broken cooling fins specifically create conditions directly leading to hot spots.