Incident
Flight SU831, operated by an II-14M aircraft, was en route from Moscow-Bykovo to Simferopol with intermediate stops in Chernigov and Kirovograd. While cruising at an altitude of 2,700 meters, the crew encountered turbulence in poor weather conditions. The crew requested permission from air traffic control to modify their altitude, but ATC denied the request due to heavy traffic in the area. Despite the denial, the captain proceeded to climb.
Collision
Shortly after the climb began, at an altitude of 2,950 meters, the II-14M collided with a Soviet Air Force AN-12BP registered CCCP-08525. The AN-12BP was en route from Kedainiai (Lithuania) to Ryazan, carrying 91 soldiers and a crew of 5 back to their base. It was the third aircraft in a formation of three. The collision occurred when the top of the AN-12's tail struck the base of the II-14's fuselage. Both aircraft went out of control, dove into the ground, and crashed in a field, coming to rest approximately 800 meters apart. All 120 occupants on both aircraft—the 91 soldiers, 5 crew on the AN-12, and the crew and passengers on the II-14—were killed.
Probable Cause
The official investigation determined that the captain of the civil aircraft (II-14) neglected elemental navigation rules by starting to climb after ATC had denied and refused permission due to traffic.