The Polkarpov TIS was a heavily-armed Soviet heavy fighter designed during the early 1940s. Only two prototypes were built because its intended engines proved to be too unreliable to be placed into production and the engines' manufacturer lacked the resources to fix the problems. The second prototype crashed in September 1944 and the program was canceled after the death of Nikolai Nikolaevich Polikarpov, the chief designer of his eponymous OKB, earlier that year.