Plain English Meaning
An engine where the cylinders sit in one straight line, one after the other, instead of being spread out in other patterns.
Full Definition
A piston engine in which all cylinders are arranged in a single straight row along the crankshaft, rather than being opposed, in a V-configuration, or radial.
Context Anchor
Seen when comparing aircraft engine types, aircraft descriptions, or basic aircraft systems in ground training.
Derivation
From 'in line,' meaning arranged along a single line. The name simply describes the layout: cylinders sitting in a row along the crankshaft.
Why Pilots Care
Inline engines create a narrow nose profile that reduces drag but can complicate engine cooling in .