First developed in 1904 for aircraft use, the radial engine became one of the most reliable means of power for aircraft from the First World War through the 2nd, and is still in use around the world today. An array of air-cooled cylinders – always an odd number from as few as 3 up to as many as 9 – operated the crankshaft that turned the propeller. Charles Lindbergh used a radial engine in the Spirit of St. Louis for his historic flight from New York to Paris in 1927. Because their power to weight ratio was better than most inline engines, radial engines became popular not only for aircraft but also for vehicles such as tanks, and later, helicopters. Our POWERPLANT ENGINE CLOCK is representative of the type of radial engine found in US Aircraft from the 1920’s through the 1940’s.