Complex sentence: It was on an Yak-28 that captain Boris Kapustin and lieutenant Yuri Yanov made their heroic feat: on the 6th of April 1966, when one of the engines on their aircraft stopped, they managed to divert their aircraft from a housing estate in Berlin.
Split into simpler sentences: It was on the Yak-28, that captain Boris Kapustin and lieutenant Yuri Yanov made their heroic feat. On the 6th of April 1966, when one of the engines on their aircraft stopped, they managed to divert their aircraft from a housing estate in Berlin.