The aircraft lost control following an electrical failure and crashed near Voronezh in the Soviet Union.

[1] The aircraft was on a domestic passenger flight between Moscow and Yerevan at flight level 260 (about 26,000 feet (7,900 m)) when an electrical failure disabled some of the aircraft instruments including the compass and the two main gyros.

It was 00:58 in the dark and according to the official version without a natural horizon due to clouds the crew became confused on the orientation of the aircraft and control was lost and the aircraft crashed killing all on board.

[1] CAP 479 - World Airline Accident Summary - Volume 2: 1976 onwards.

London: Civil Aviation Authority (United Kingdom).