The radial motor made its first appearance in 1903, when Charles Matthews Manly built a water cooled five cylinder model he installed in Langley's Aerodrome A aircraft.
That thru decades of engineering morphed into the 14 cylinder, twin row Pratt & Whitney R-1830 Twin Wasp.
Four of the later 18 cylinder Twin Wasp radial engines, as well as the supercharged 18 cylinder Wright R-3350 Duplex-Cyclone, powered the Lockheed Constellation that is still the largest piston powered aircraft ever. Wiki.
