FAA Aviation Mechanic Powerplant (AMP)Fuel, Induction and LubricationEasy
During a preflight inspection, a technician drains fuel from the aircraft's fuel strainer sump into a clear sample cup. Why is this check performed?
- ATo check for water contamination and sediment, which settle at the low point of the fuel system
- BTo verify the fuel filter element is not clogged with debris
- CTo verify that the fuel selector valve is properly indexed to the correct tank
- DTo measure the specific gravity of the fuel and confirm it meets grade requirements
Show answer & explanationAnswer & explanation
Correct answer: A. To check for water contamination and sediment, which settle at the low point of the fuel system
Water and sediment are heavier than gasoline and settle at the lowest point in the fuel system. Draining the strainer sump allows visual inspection for water droplets and contaminants before flight.
Why the other options are wrong
- B. Checking the filter element condition requires disassembly, not a sump drain.
- C. Fuel selector position is verified separately, not by draining the strainer.
- D. Specific gravity testing requires a hydrometer, not a simple sample cup check.
Fuel Strainer Sump Drain Check
A preflight procedure where fuel is drained from the lowest point of the fuel system to check for water and sediment contamination.
- Water is denser than avgas and settles at the bottom
- Sediment and water appear as distinct droplets in the sample
- Performed before each flight and after refueling
Memory trick: Sump drain sinks out the sinkers (water/sediment)