Probably the most numerous primary trainer in USSR, Yak-18 family, with simple low-wing design, can trace ancestry back to UT-2 (Ya- 20), standard primary trainer of WWII, which first flew May 35. Yak-18 introduced full blind-flying instruments, helmeted engine, sliding transparent hoods over tandem cockpits, and pneumatically-operated retractable landing gear and flaps. 1957, Yak-18A introduced cleaned-up airframe, more powerful engine in a smooth long-chord cowl driving controllable pitch prop, and retractable tricycle landing gear. Known in Korea as "Bed Check Charlie," flew nuisance raids over Allied forced during Korean conflict. Yak-18 established international speed record for class 1951.