Definition
The slow, permanent deformation of a metal part that occurs when it is held under continuous load at high temperature over time. Even when the load is well below the metal's normal yield strength, prolonged heat and stress cause the material to gradually stretch or distort.
Plain English
When a metal part stays hot and under load for a long time, it slowly stretches out of shape — even if the load isn't strong enough to bend it right away.
Context Anchor
Seen during aircraft wheel and tire inspections, including the preflight walkaround and maintenance checks after heavy braking.
Derivation
From the everyday word 'creep,' meaning to move slowly and almost imperceptibly. The name fits: the metal doesn't bend or break suddenly — it slowly creeps into a new shape over hours of operation.
Why Pilots Care
Unchecked creeps can damage the valve stem, unbalance the wheel, or lead to tire failure.
Grounding Statement
Picture a turbine blade spinning at high RPM in extremely hot gas. Over many hours, the blade stretches a tiny amount in length — not from any single overload, but from the steady combination of heat and centrifugal pull.
Intuition Check
Creeps are not the tire slowly moving across the ground. In this aircraft-wheel context, they are the marks used to detect whether the tire has slipped on the wheel.
Example Sentence 1
Turbine blades are inspected for creep during overhaul, since prolonged exposure to high temperatures can stretch them beyond service limits.
Example Sentence 2
The tire was replaced because creeps had rotated the valve stem against the wheel.