Plain English Meaning
A measurement of how easily a fluid flows. A fluid with a low stoke value flows easily, like water; one with a high stoke value flows slowly, like cold engine oil.
Full Definition
A unit of kinematic viscosity in the centimeter-gram-second (CGS) system, equal to one square centimeter per second (cm²/s). It expresses how readily a fluid flows under the influence of gravity, accounting for both its resistance to flow and its density.
Context Anchor
Seen in discussions of smoke, fire, and ventilation inside the airplane.
Derivation
Named after Sir George Gabriel Stokes, a 19th-century Irish mathematician and physicist whose work on fluid motion led to the equations describing how fluids flow. Knowing the unit is named after a person — not the everyday word 'stoke' meaning to feed a fire — helps avoid confusion.
Why Pilots Care
Engine oils, hydraulic fluids, and fuels are specified by their viscosity. Using a fluid with the wrong viscosity rating can affect engine lubrication, cold-weather starting, and overall system performance.
Grounding Statement
A small flame can grow quickly if it is given a fresh supply of air.
Intuition Check
Do not read stoke as simply “start a fire.” In this context, it means to feed an existing fire and make it burn stronger, often by adding air.
Example Sentence 1
The oil's viscosity, measured in stokes, increases sharply as outside temperatures drop, which is why preheating may be required before a cold-weather start.
Example Sentence 2
During the go-around, he stoked the throttle to full power for the missed approach.