Definition
A filtering device installed at the lowest point of the fuel system that traps water, dirt, and other contaminants before fuel reaches the engine. It includes a drain valve that allows the pilot to sample the trapped fuel and contaminants during preflight inspection.
Plain English
A small filter at a low point in the fuel system that catches water and dirt so they don't reach the engine. The pilot opens a drain on it during preflight to check for and remove any contamination.
Context Anchor
Seen during preflight fuel checks and in aircraft fuel system descriptions, especially where the pilot drains fuel samples to look for water or debris.
Derivation
Strainer' comes from the Latin 'stringere,' meaning to draw tight or squeeze. In everyday use, a strainer separates solids from liquids -- the same idea applies here, with the added job of catching water that has settled out of the fuel.
Why Pilots Care
Contaminated fuel can cause engine failure; draining the strainer is a required daily safety step.
Analogy
It works somewhat like a kitchen strainer: liquid passes through, while unwanted material is held back. In an aircraft, the goal is not cooking convenience—it is keeping the engine supplied with clean fuel.
Intuition Check
Do not think of a fuel strainer as just a drain point. The drain lets you check what has collected there, but the strainer’s job is to catch unwanted water or particles as fuel flows through the system.
Example Sentence 1
During preflight, the pilot drained a sample from the fuel strainer and checked it for water and sediment.
Example Sentence 2
After refueling, the student pilot drained the fuel strainer on both wing tanks as part of the preflight inspection.