Project 636 Varshavyanka (Black Hole) is a more advanced version of Project 877 Paltus (Kilo-class submarine in the West). roject 636 boats are equipped with improved MGK-400EM, with MG-519 Arfa also upgraded to MG-519EM. The improved sonar systems have reduced the number of operators needed by sharing the same console via automation. The version Kilo 636MV (exported to Vietnam) contains a GE2-01 radar and an improved MGK 400E sonar. In this version, the submarine is also able to operate in more weather conditions than the original Kilo-class submarines.