What happened
During flight SU831, an II-14M was traveling from Moscow-Bykovo toward Simferopol, with scheduled stops in Chernigov and Kirovograd. While cruising at 2,700 meters through difficult weather conditions, the crew encountered turbulence and requested permission from Air Traffic Control to change their altitude. This request was rejected by controllers due to high traffic density in the area.
Despite not receiving clearance, the captain initiated a climb. Shortly after reaching an altitude of 2,950 meters, the II-14M collided with a Soviet Air Force AN-12BP, registration CCCP-08525. The second aircraft was operating as the third plane in a three-aircraft formation, transporting 91 soldiers and a crew of 5 from Kedainiai, Lithuania, to Ryazan.
The impact occurred when the upper portion of the AN-12BP's tail struck the lower fuselage of the II-14M. Following the collision, both aircraft lost control and descended into a field, crashing approximately 800 meters apart. The accident resulted in 120 fatalities, leaving no survivors from either flight.
Findings
Investigations concluded that the primary factor was the pilot of the civil aircraft violating air traffic instructions by climbing without authorization after his request for an altitude change had been denied.