Definition
A piston aircraft engine in which the cylinders are arranged in a circle around a central crankshaft, like spokes on a wheel. Each cylinder fires in sequence, and all connecting rods drive the same single crankshaft at the hub.
Plain English
An engine where the cylinders stick out in a circle around the middle, instead of sitting in a row.
Context Anchor
Seen in discussions of older aircraft, engine types, aircraft recognition, and examples that need a concrete aircraft part rather than an abstract idea.
Derivation
‘Radial’ comes from the Latin radius, meaning ‘ray’ or ‘spoke of a wheel.’ It describes anything arranged outward from a central point — exactly how the cylinders are laid out in this engine.
Why Pilots Care
Radial engines offer good cooling and were widely used in early aircraft for their mechanical simplicity.
Analogy
Picture a bicycle wheel laid flat: the hub is the crankshaft, and the spokes are the cylinders pointing outward.
Intuition Check
Radial engine does not mean a navigation radial or a radio line from a station. Here, radial describes the engine’s circular cylinder arrangement.
Example Sentence 1
The old DC-3 on the ramp is powered by two radial engines, each with nine cylinders arranged around a central crankshaft.
Example Sentence 2
Maintenance crews checked the radial engine's cylinders for even cooling after the flight.