Definition
A radial engine arrangement in which two rows of cylinders are mounted around a common crankshaft, one row behind the other, with the cylinders of the rear row staggered between those of the front row. This configuration allows more cylinders, and therefore more power, without increasing the engine's frontal diameter.
Plain English
A radial engine with two circles of cylinders, one behind the other, instead of just one. Staggering the back cylinders between the front ones lets cooling air reach all of them while keeping the engine the same width.
Context Anchor
Seen in descriptions of older radial-powered aircraft, engine manuals, maintenance discussions, and aircraft specifications.
Derivation
Radial comes from the Latin radius, meaning ray or spoke, because the cylinders are arranged like spokes around a hub. Twin-row simply means two such rings of cylinders stacked along the crankshaft.
Why Pilots Care
Delivers substantial horsepower in a relatively short length, making it suitable for high-performance propeller aircraft.
Analogy
Picture a wheel with spokes pointing out from the hub. A single-row radial is like one layer of spokes; a twin-row radial is like two layers of spokes, one behind the other.
Intuition Check
Twin-row does not mean two separate engines. It means one radial engine with two circular rows of cylinders.
Example Sentence 1
The Pratt & Whitney R-2800 is a twin-row radial engine with eighteen cylinders arranged in two rows of nine.
Example Sentence 2
Twin-row radial engines powered many classic transport aircraft due to their reliability and power output.