Incident
While cruising at an altitude of 10,000 meters over the Voronezh region, the aircraft entered a cumulonimbus cloud area. It first encountered updrafts, causing it to climb to 10,700 meters. Subsequently, it encountered downdrafts and descended to 7,000 meters. During further downdrafts, the propellers on engines number one and four were automatically feathered. The descent continued to 2,800 meters, at which point the crew regained control of the aircraft.
The crew contacted air traffic control and received permission to return to Vnukovo for an emergency landing. The landing was uneventful.
Aftermath
All 56 occupants were evacuated. Some occupants sustained injuries. The aircraft was later declared damaged beyond economical repair due to heavy structural damage.
Additionally, it was reported that chemical liquid stored in the toilet compartment leaked and came into contact with several electrical systems, causing short-circuits. Several connectors failed, as did the VHF communication system.