The Yak-18A is the third major serial modification, qualitatively improved due to a much more powerful engine. The first prototype was obtained by installing an AI-14R engine with a capacity of 220 (later 260) hp with a new screw on the serial Yak-18U. Work began in 1956. The aircraft was first called the "modified Yak-18U", then the Yak-20 (not to be confused with the experimental Yak-20 of 1949), and since 1957 the Yak-18A. The design of the Yak-18U had to be significantly redesigned for a heavier 9-cylinder engine. Many changes have been made to the airframe, control system, and cockpit. Navigation and radio equipment has been completely replaced. The aerobatic properties of the aircraft have improved dramatically compared to the Yak-18U, despite a significant increase in flight weight. Factory tests of the first sample were held in October 1956, state — in February-March 1957. The second, modified sample passed state tests in August-October 1957. The first production aircraft was built at the end of 1957. Production continued until 1960.