Definition
The drawing of a liquid through a narrow material or along a fibrous path by capillary action, the same surface-tension effect that pulls fuel up a lamp wick or solder along a heated joint. In aviation maintenance, wicking refers to this movement of fluids — fuel, oil, hydraulic fluid, water, or solvents — along stranded wires, fabric, insulation, seams, or hairline cracks, often spreading well beyond the original point of contact.
Plain English
A liquid quietly travelling along a material, like the way a paper towel soaks up a spill or wax climbs a candle wick.
Context Anchor
Seen in aircraft maintenance discussions involving fuel, oil, water, sealants, fabric, insulation, and other materials that can absorb or carry liquid.
Derivation
From the lamp wick, which draws oil or wax up its fibres by capillary action. The verb 'to wick' was adopted to describe any liquid that travels through a material the same way. Knowing the lamp-wick image makes the aviation use immediate: the fluid is climbing or spreading on its own, without pressure pushing it.
Why Pilots Care
Uncontrolled wicking can produce fuel leaks, corrosion, or hidden moisture damage.
Analogy
A paper towel touching a small spill will draw the liquid into itself and spread it beyond the spot it first touched. That spreading is wicking.
Intuition Check
Wicking does not mean a liquid is being forced by pressure. It means the material itself is drawing the liquid along through tiny spaces.
Example Sentence 1
The mechanic noticed fuel had been wicking along the wire bundle, well past the actual source of the leak at the fitting.
Example Sentence 2
Proper dope application stops moisture wicking into the fabric on older wings.