Aeroflot Flight 6515

Aeroflot

Company type	Airline
Industry	Aviation
Headquarters	Moscow , Soviet Union
Products	Air transport services

Template:Infobox aircraft occurrence Aeroflot Flight 6515 was a scheduled service operated by Aeroflot that tragically ended in a fatal crash on October 23, 1978, over Sivash Bay. The accident was attributed to engine failure resulting from icing conditions and pilot mistakes, leading to the loss of all 26 individuals aboard.

Accident

On October 23, 1978, an Antonov An-24B operated by Aeroflot crashed in the waters of Sivash Bay. This aviation disaster claimed the lives of all 26 occupants on board.

Aircraft

The involved An-24B, bearing tail number CCCP-46327 and factory serial number 97305504 (serial 055-04), was manufactured by the Antonov Serial Production Plant on August 26, 1969. Prior to the incident, the aircraft had accumulated a total flight duration of 15,851 hours and completed 13,457 landings.

Crew

The flight crew belonged to the 83rd flight squadron and consisted of:

• Captain — Vladimir Mikhailovich Dubinin;
• First Officer — Vladimir Vladimirovich Yunkin;
• Navigator — Vladimir Borisovich Latalin;
• Flight Engineer — Vladimir Alexandrovich Lisitsyn;
• Flight Attendant — Nina Rudolfovna Vorobyova.

Accident Details

Earlier on the day of the crash, the crew had flown the Stavropol—Grozny—Stavropol route. Subsequently, they were assigned to operate Flight 6515 from Stavropol to Simferopol, continuing to Chișinău and terminating at Lviv. The aircraft carried 21 passengers alongside five crew members. Departure from Stavropol Airport occurred at 18:14 Moscow time. After reaching cruising altitude, the plane maintained a flight level of approximately 2,400 meters while navigating an alternate route designated as 29B (Gelendzhik—Tobechik Lake—Lenino, Crimea—Yemelyanovka, Crimea—Simferopol).

Weather conditions over Stavropol featured partial cloud cover with visibility surpassing 10 kilometers. However, as the flight progressed near Kerch and onward toward Simferopol, continuous cloud layers were encountered with bases between 600 and 800 meters and tops reaching between 3,000 and 3,500 meters. Winds at cruising altitude were strong westerly gusts ranging from 40 to 50 km/h. Notably, icing conditions intensified as the aircraft neared Simferopol.

At approximately 19:39, while flying within clouds at an altitude near 2,450 meters for roughly fifteen minutes, the crew received communication from Simferopol Airport’s air traffic controller. In response to inquiries about their status, the pilots reported being enveloped in clouds with significant ice accumulation on the aircraft surfaces. Shortly afterward, they notified that the left engine had ceased functioning. Within fourteen seconds, they updated that both engines were no longer operational and initiated a descent toward land. No further transmissions were received following this exchange.

At precisely 19:40—one hour twenty-five minutes and thirty-one seconds after departing Stavropol—both engines failed nearly simultaneously with a brief interval of about three and a half seconds between failures. The propellers automatically feathered as designed. The crew executed an abrupt left turn aiming for land but experienced a reduction in speed to approximately 250 km/h. Attempts to restart the left engine were unsuccessful; instead, this action generated reverse thrust which further decreased velocity to around 186 km/h and caused a left bank angle of about forty-five degrees. The aircraft reached a critical angle of attack leading into a steep spiral descent accompanied by increasing forward velocity. A pitching moment prompted the pilots to pull back fully on the control columns, which accelerated angular rotation rates. At an altitude near five hundred meters, the plane completed a full rotation (360°) along its longitudinal axis. Approximately ninety seconds after engine failure, at about 19:41, the airplane impacted Sivash Bay’s surface traveling forward at roughly 490 km/h with a vertical descent speed near ninety meters per second at an estimated angle of fifty degrees involving both nose and left wingtip contact. All twenty-six passengers and crew perished.

The wreckage was located on the following day submerged beneath roughly two and a half meters of water approximately twenty-four kilometers southeast of Yemelyanovka village. Beneath this shallow water lay an additional layer of soft silt measuring four and a half to five meters deep. Recovery efforts commenced immediately upon discovery and continued under minimal visibility conditions until November eighteenth when the left engine was retrieved. Major components of the wreckage along with flight data recorders were successfully recovered from underwater.

Causes

Analysis of the MSRP-12-96 flight recorder data revealed that, except for the initial 7 minutes, the crew did not engage the wing and tail anti-icing system (AIS) for a duration of 79 minutes. Activation of the engine AIS occurred only during the final 3 minutes prior to the aircraft's impact with the water. It remains unclear whether the system was switched on during the last 1.5 minutes before engine shutdown. Upon recovery from the water, the air bleed valve responsible for warming the inlet guide vanes and air intakes on the left engine was found in an open state; however, this event was not recorded by the flight data, suggesting that it may have been opened either within the first 7 minutes or between 3 and 1.5 minutes before recording ended.

To identify contributing factors, investigators carried out both airborne and ground-based engine tests simulating icing conditions. In flight trials, ice accumulation measuring 40 mm in thickness detached from the engine over a minute after heating activation, without triggering automatic propeller feathering. Conversely, on a test rig, ice shedding resulted in automatic feathering approximately 40 to 45 seconds following AIS activation. A separate flight test involving 65 mm thick ice caused immediate engine shutdown accompanied by automatic propeller feathering. Notably, no visible damage or deformation was observed on either the inlet guide vane blades or the first-stage compressor blades after ice ingestion.

Drawing from these observations, the commission determined that the crash was most likely caused by simultaneous engine failure due to icing of air intakes and inlet guide vanes, followed by ice detachment entering the engines' gas-air pathways as a result of delayed heating system activation by the crew. Furthermore, it was highlighted that the Aircraft Flight Manual (AFM) did not provide guidance for handling dual-engine failure scenarios during flight. Additionally, there was an absence of crew training focused on managing emergencies under conditions of night flying, cloud cover, and icing, all of which contributed to escalation of this incident into a fatal accident.