Aeroflot Flight 6274

The aircraft was operating flight 6274 on the route Tbilisi—Sukhumi—Krasnodar. The crew from the 241st flight squadron consisted of commander Ivan Kirillovich Lysenko, first officer Fyodor Romanovich Babichev, navigator Alexander Ivanovich Velichko, and flight engineer Vyacheslav Nikolayevich Masekin. The flight attendant in the cabin was Margarita Fyodorovna Babicheva. At 21:23 (20:23 MSK), with 33 passengers on board, the An-24 took off from Tbilisi Airport and after gaining altitude, reached a cruising level of 6,000 meters.^[1]

Along the route, the sky was covered with clouds with a lower boundary of 200–300 meters and an upper boundary of 4,000–5,000 meters, which had severe icing and intense turbulence, and it was raining heavily. The crew was aware of thunderstorms ahead along the route and saw their clusters on the onboard radar screen. They were also informed by the zone controller of RDP Sukhumi that the previous aircraft avoided thunderstorms 15 kilometers north of the route, so it was decided to avoid thunderstorms by diverting 10–15 kilometers north of the route, which was reported to the controller at 21:02. At 21:04, the aircraft made a right turn and set a course of 320°—25° off the assigned route. At 22:08, the controller contacted the crew and suggested turning left to return to the route. He also gave permission to descend to 4,200 meters. However, the crew decided to continue avoiding thunderstorms from the north while starting to descend to the specified altitude. At 22:11, the crew reported reaching 4,200 meters and then switched to the approach controller (APP). But the approach controller was replaced by the zone controller (RDP), who allowed descent to 3,000 meters.^[1]

At 22:13, the crew reported reaching 3,000 meters. The crew mistakenly believed they had passed the Gali NDB, which they reported to the controller, while in reality, they were still 8–10 kilometers away from it. The zone controller, who was not authorized to work as an approach controller, did not monitor the flight of the aircraft on the radar and radio direction finder and did not determine its true position. Upon hearing the report of passing the traverse of Gali, he allowed descent to 1,200 meters on the course to the outer marker. Misidentifying their location, the crew confirmed the instruction and began descending. At 22:14, flying at night in solid clouds 25 kilometers north of the route at a speed of 410 km/h, the An-24 at an altitude of 2,250 meters above sea level collided with the steep slope of Mount Apshara (height 2,580 meters, 15 kilometers south of the Kodori Range) 91 kilometers east (azimuth 90°) of Sukhumi Airport and 25 kilometers northeast of Gali (directly at the traverse of the NDB). All 38 people on board the airliner perished.^[1]

The primary cause was the violation of ATC rules by the dispatching personnel and the crew's error in determining the aircraft's location during descent in the mountains.

Contributing factors:

1. The minimum safe flight level on this route in the area of the Gali NDB was calculated incorrectly. The maximum altitude difference was accounted for in a strip 17 km from the route, not 25 km from the route. Thus, the minimum safe flight level was set at 2,400 meters, whereas it should have been 3,600 meters. As a result, descent on the route occurred below the actual safe altitude, creating a threat to flight safety.
2. Violations and deficiencies in the organization of meteorological support for flights.^[1]