A mechanic is troubleshooting a turbine engine's main fuel filter, which is equipped with a differential pressure bypass indicator. During ground run, the mechanic observes that the indicator's button has popped out. What does this indicate?
- AThe filter is becoming clogged, and the pressure drop across it is approaching the point where the bypass valve will open
- BThe fuel-oil heat exchanger is overheating the fuel
- CThe fuel control unit has lost calibration
- DThe fuel boost pump has failed completely
Show answer & explanationAnswer & explanation
Correct answer: A. The filter is becoming clogged, and the pressure drop across it is approaching the point where the bypass valve will open
A popped differential pressure indicator signals that the pressure drop across the fuel filter element has increased due to contaminant buildup, nearing the point at which the bypass valve would open and allow unfiltered fuel to pass. This warns the mechanic to inspect or replace the filter element before contamination reaches the fuel control unit and nozzles.
Why the other options are wrong
- B. A fuel-oil heat exchanger issue would affect fuel temperature, not directly trigger the filter bypass indicator.
- C. FCU calibration issues affect fuel scheduling, not the filter's differential pressure indicator.
- D. A failed boost pump would typically cause low fuel pressure, not a filter bypass indication.
Fuel Filter Differential Pressure Indicator
A device on a turbine engine's main fuel filter that pops out when the pressure drop across the filter element rises, warning of a nearly clogged filter approaching bypass.
- Located on turbine engine main fuel filter
- Pops out when differential pressure increases
- Warns before unfiltered fuel bypasses the element
- Prompts filter inspection/replacement
Memory trick: Button pops = filter's clogged, don't let dirty fuel through