Plain English Meaning

The time it takes for an engine's spinning parts to wind up to a higher speed after the pilot adds power.

Full Definition

The process by which an engine's rotating components accelerate from a lower rotational speed to a higher one in response to a power increase. In turbine engines it refers to the compressor and turbine assemblies (the spools) accelerating to a commanded power setting; in turbocharged piston engines it refers to the turbocharger turbine accelerating until it produces useful boost.

Context Anchor

Used during engine checks, before-takeoff checks, and power changes when the pilot is watching or for the engine to build power smoothly.