FAA Powerplant Written Practice Test

What is a typical indicator of an operating engine in a low humidity environment?

1. Wet spark plugs

2. Clean fuel lines

3. Blue dehydrator plugs

4. Fluctuating oil pressure

The correct answer is: Blue dehydrator plugs

In a low humidity environment, blue dehydrator plugs are a typical indicator of an operating engine. Dehydrator plugs are designed to change color based on moisture content in the surrounding air. In low humidity conditions, the absence of moisture decreases the likelihood of condensation forming in the engine components, which is essential for preventing corrosion and ensuring optimal operation. When the dehydrator plugs are blue, it indicates that the system is effectively removing moisture, which is crucial for the health of the engine and its components. This is particularly important during operation, as moisture can lead to issues such as rust and degradation of lubricants and fuel. Wet spark plugs would typically indicate a fueling issue or other problems, while clean fuel lines do not specifically relate to the humidity level. Fluctuating oil pressure, on the other hand, can signal mechanical issues or abnormalities in the oil system, but does not directly correlate to the operational status of an engine in a low humidity environment, making blue dehydrator plugs the most relevant and indicative solution in this context.