What is the result if the fuel filter is completely clogged?

If the fuel filter is completely clogged, the most likely result is that the engine will flame out. A fuel filter's primary function is to remove impurities and debris from the fuel before it reaches the engine. When this filter becomes completely blocked, it can prevent fuel from reaching the engine altogether. An engine requires a constant supply of fuel to maintain combustion; if this supply is interrupted, the engine will lose power and may completely shut down, leading to a flameout.

This situation can critically impact the engine's performance, especially in flight. In a T‑6B or similar aircraft, a flameout emphasizes the importance of maintaining fuel system integrity and monitoring fuel filters regularly to ensure they are not clogged. Other options depict scenarios that are either unlikely or not correct; for example, an overflowing fuel situation would occur if there’s an issue upstream that overpressurizes the fuel system, and bypassing the filter would not happen as a result of total blockage. Continuing to operate normally contradicts the very purpose of fuel delivery; if fuel is blocked, combustion cannot be sustained.