Khabarovsk United Air Group Flight 3949

The aircraft Tupolev Tu-154B-1, involved in the accident, was manufactured on 30 July 1976 under a serial number 76А164. Like other former Soviet aircraft, it was previously registered as USSR-85164, being operated by the flag carrier of USSR, Aeroflot. Following the Soviet Union dissolution in 1991, the aircraft was re-registered as RA-85164 and was sent to Khabarovsk United Air Group, though the livery would not be changed from the former operator.^[2]

Prior to the accident the Tupolev Tu-154 had accumulated 30,001 flight hours and undergone four repairs, the last one on 23 September 1991. During the last maintenance, two of its engines were replaced. Following said maintenance, the aircraft had a tendency to roll to the left without any command from the pilots. The issue was not rectified and pilots kept flying with the unresolved problem.^[3]

The aircraft was carrying 90 passengers and 8 crew members, including 5 children and 1 infant. The list of nationalities of those on board was not disclosed.^[4][5]

At the time of the accident, the flight crew were consisted of:

• The commander of the flight was 46-year-old Captain Viktor Konstantinovich Sumarokov. Graduated from Buguruslan Flying School, he had accrued a total flying experience of more than 12,000 hours, of which 5,054 hours were on the Tupolev Tu-154. He had never been involved in any accidents or incidents during his flights in the past.
• The second-in-command was 43-year-old First officer Stanislav Aleksandrovich Revedovich. Graduated from Omsk Aviation Academy, he had accrued a total flying experience of around 10,000 hours, of which 1,620 hours were on the Tupolev Tu-154. He had been involved in an incident during landing in Irkutsk in 1994.^[3]

The other flight crews were 32-year-old Navigator Alexander Alekseevich Martynov with a flying experience of 5,008 hours, including 1,990 hours on the Tupolev Tu-154; and 30-year-old Flight engineer Grigory Alekseevich Moroz with a flying experience of 1,816 hours, all of which were on the Tupolev Tu-154.^[3]

The flight was the second leg of a round-trip flight from Khabarovsk to Yuzhno-Sakhalinsk, back to Khabarovsk before continuing to Novosibirsk with an intermediate stop in Ulan-Ude. During the trip to Yuzhno-Sakhalinsk, the flight was initially scheduled to take off at 16:45 local time, but due to deteriorating weather conditions, the flight was delayed for several hours. The aircraft eventually took off at around 23:00 local time with no passengers. During the flight, the aircraft was progressively banking to the left, causing the crew to constantly make a right bank input to stabilise the aircraft. They managed to level the wings, and the flight proceeded to its destination without any further incident.^[6]

The aircraft landed in Yuzhno-Sakhalinsk Airport at 00:34 local time and was parked for approximately 2 hours. First Officer Revidovich would be the pilot flying, while Captain Sumarokov would be the one handling the comms. The aircraft took off at 02:43 a.m with 90 passengers. The takeoff weight was within acceptable limits, at 82,600 kilograms (182,100 lb), and the fuel weight was 15,100 kilograms (33,300 lb).^[6]

During the climb, the aircraft instantaneously began a progressive bank towards the left. The crew, who had faced similar situations on prior flights, simply rolled the aircraft's control column to the right to level the wings. However, the aircraft kept banking towards the left, causing the control column to be turned even more to the right to prevent the aircraft from rolling over. It eventually reached an angle greater than the crew could normally handle, at one point reaching an angle of 30 degrees.^[6]

Seeing the significant asymmetry, Captain Sumarokov opined that they should work with a fuel transfer from the left wing tank to the right wing tank to counteract the bank angle, which was agreed upon by all of the crew. The crew had faced the same situation on prior flights, and the same exact action, commencing a fuel transfer, had been done before. On those flights, they successfully managed to balance the aircraft. After completing the transfer, the crew continued the flight.^[6]

The autopilot, which had been engaged earlier, sensed that the aircraft began to turn towards the right instead, causing the system to deflect the control column to the left. The bank angle, however, became progressively steeper, reaching 15 degrees. Exceeding the maximum angle that the autopilot could handle, the bank angle could not be controlled any longer, and the aircraft turned further to the right. The crew was conducting the pre-landing checklist and didn't notice that the aircraft had turned to the right instead of the left.^[6][7]

As the pilots were diverting their attention to the pre-landing checklist, the bank angle continued to increase. It eventually reached an angle of more than 30 degree, prompting the aircraft's system to alert the crew on the issue by illuminating the warning lights. Both crew didn't react to the lights, but Captain Sumarokov sensed that something was wrong as the large bank angle had caused him to sense that the aircraft was excessively banking, causing him to order First Officer Revidovich to "slow down".^[6][7]

Captain Sumarokov eventually asked the autopilot to be turned off, but the aircraft kept banking. It somehow turned even faster to the right, reaching 2 degree per seconds. After reaching 45 degree, the control column was deflected to the left, but the angle kept increasing. Captain Sumarokov was perplexed by the situation and asked his fellow crew on what had happened on the aircraft. First Officer Revidovich told him that the aircraft was turning to the right, and with an angle larger than usual.^[6][7]

As the aircraft kept turning, it gained more speed. Exceeding the upper limit of the airspeed that the aircraft could handle, the overspeed alarm blared. The crew, realizing that the aircraft was in danger of crashing, tried to reduce the list by making a turn of approximately 45 degree to the left on the control column. The aircraft didn't budge, and instead it kept listing to the right.^[6]

External videos
In-flight recordings
Partial CVR recording of the flight on YouTube
Partial FDR recording of the flight on YouTube

The aircraft continued to plunge to the ground at a terrific speed of at least 100 meters per second. Desperate, the crew frantically moved the control column in every direction to counter the increasing right bank. They had lost all sense of spatial orientation, and all of their attempts to save the aircraft failed. The aircraft continued to spiral down and gained more speed. The flight crew had lost all control of their aircraft.^[6]

The aircraft crashed into Bo-Dzhausa Mountain with a vertical speed of about 300 m/s and a pitch angle of about 70 degrees. The aircraft disintegrated into numerous fragments. All 98 people on board were killed instantly upon impact.^[6]

The aircraft was cruising at 10,600 metres (34,800 ft) (according to the investigation report; alternatively, at 9,600 metres (31,500 ft).^[1][8]) and disappeared from radar shortly after making a routine ATC report. The last contact with ATC was made on 03:00 a.m. local time (17:00 UTC). At the time, Flight 3949 was at a distance of approximately 160 km from Khabarovsk. It eventually missed its estimated time of arrival at 03:45 local time.^[9] Nearly an hour later, the search and rescue operation commenced. An Antonov An-12 and a Russian Air Force Antonov An-26 were deployed to scour the site for the missing aircraft but were later called off by midnight as they couldn't find the crash site due to heavy snow and low visibility.^[10][11]

Radio Moscow initially reported that the wreckage, which was claimed to have been in flames, had been spotted approximately 120 km from Khabarovsk. The report was denied by the Russian Ministry of Emergency Situations.^[12]

Villagers in Koppi reported that they had heard low-flying aircraft in the vicinity, meanwhile in Grossevichi there were claims that the aircraft had crashed within the village. Multiple personnel were deployed to the area, but no traces of the aircraft could be found. The search area was eventually widened, reaching the Tatar Strait. Multiple ships were sent to scour the area for any wreckage of the aircraft.^[13][10]

On 9 December, Deputy Prime Minister of Russia Oleg Soskovets arrived in Khabarovsk to observe and supervise the search and rescue operation. A total of 22 ships were deployed to the Tatar Strait. According to authorities, a Tupolev Tu-134 aircraft equipped with metal-detecting technology would be involved in the search. The Russian Ministry of Defense also announced that they would assist the operation by using satellite imagery, in hopes of finding the wreckage.^[10][14]

Paratroopers had been deployed by the Russian Army to assist the operation. Rescuers eventually managed to find some debris before realizing that it had belonged to other airliner accidents that had happened prior to the crash of Flight 3949. A total of 14,000 square meters of areas had been scoured to search the wreckage. However, there were still no signs of the wreckage. Satellite imagery in the area suggested that some wreckages were spotted near Berezovaya, though this was later confirmed to be not true. Other reports, which stated that the wreckage had been spotted following the discovery of oil slicks in the north of the Sea of Japan and claims of smoke being seen in Sukpai, were dismissed by officials.^[15][16]

Getting desperate after days of no results in finding the crash site, authorities asked the assistance of then-famous Russian clairvoyant Juna, who told them that the search area should have been widened. She indicated that the crash site was located within an area twice as large as the area that had been searched by the rescuers, near the Samarga River. However, after an extensive search, the crew found no luck with the pinpointed site.^[15][10]

The crash site was found by chance on 18 December 1995, on the Sikhote-Alin Ridge of Bo-Dzhausa Mountain, by the crew of a Vostok Aviation Company Mil Mi-8 pilot who didn't even take part in the operation. While making an emergency landing at a taiga, he noticed that the soil on a nearby mountain had different colors than the rest and a part of the fuselage could be seen protruding from the ground.^[17][18] He later reported it to authorities, who subsequently awarded him the Nesterov medal due to the finding.^[7]

Later reports suggested that rescuers had flown over the crash site for at least four times but couldn't find it due to inclement weather and rocky terrain.^[19]

The crash left a crater 6 ft deep and 70 ft wide. The crash site suggested that the aircraft had impacted the mountain at a terrific speed, as there were barely any recognizable pieces of wreckage. The site was strewn with bits of human tissues and personal belongings that had been shredded to small pieces due to the force of the impact. More than 50 personnel were sent to recover the bodies of the victims.^[19]

Authorities stated that relatives who wished to visit the site would be assigned to a special flight.^[19][20]

The Russian aviation industry was immediately put into the spotlight following the crash, as it was the fifth air disaster in just a week and the second major air disaster in less than 22 months. The crash caused further strain on the industry as, coincidentally, the Federation of Air Traffic Controllers' Trade Union was planning to hold an indefinite worker's strike within a week after. Russian media Kommersant stated that the then-aviation surveillance system was inadequate and inefficient to handle the industry in the country, which had just been growing exponentially following the dissolution of the USSR.^[10]

About two months after the crash, Russian authorities ordered the grounding of all Tupolev Tu-154Bs throughout the country, following findings that an unknown mechanical error might have caused the crash by making the aircraft to unintentionally bank to the right without the crew noticing. All Tupolev Tu-154Bs are to be grounded until the investigation is completed.^[21]