Pratt & Whitney R-2060 Yellow Jacket

The Pratt & Whitney R-2060 Yellow Jacket was a liquid-cooled aircraft engine project that Pratt & Whitney developed for the United States Army in the early 1930s. It had twenty cylinders arranged as five banks of four in-line cylinders, a displacement of about 2,060 cubic inches, a single overhead camshaft for each bank and a rear-mounted supercharger. The design target was 1,000 horsepower, and on its final run after 35 hours of testing it produced 1,116 horsepower. Despite that result the engine was cancelled, because the company chose to continue developing its air-cooled R-1830 Twin Wasp radial engine instead. The Yellow Jacket is therefore a rare liquid-cooled design from a maker best known for air-cooled radials, and it remained a development project rather than a service engine.