Aeroflot Flight 29674

Aeroflot Flight 29674

Yak-40 of Aeroflot
Accident
Date	24 January 1988 (1988-01-24)
Summary	Unexplained engine problems, collision with the ground
Site	near Nizhnevartovsk Airport (Ugra, RSFSR, USSR) 60°58′30″N 76°31′34″E
Aircraft
Aircraft type	Yakovlev Yak-40
Operator	Bugulma United Air Detachment, Privolzhsk Civil Aviation Directorate
Registration	CCCP-87549
Flight origin	Nizhnevartovsk Airport, Nizhnevartovsk
Stopover	Roshchino Airport, Tyumen
Destination	Bugulma Airport, Bugulma
Passengers	27
Crew	4
Fatalities	27
Survivors	4

Aeroflot Flight 29674 was a Yakovlev Yak-40 aircraft operated by Aeroflot that crashed near Nizhnevartovsk on Sunday, 24 January 1988 during takeoff, resulting in the deaths of 27 people.

Crash

The Yak-40, tail number CCCP-87549 (factory number 9531442, serial number 42-14, manufactured by the Saratov Aviation Plant in 1975^[1]), was operating flight 29674 from Nizhnevartovsk to Bugulma, with a first stop in Tyumen (Roshchino Airport). The aircraft was piloted by a crew consisting of Captain Nail Muradymov, First Officer S. Uvarov, and Flight Engineer N. Nagumanov. Stewardess Zemfira Mubarakshina was serving in the cabin. There were 27 passengers on board.^[2]

At 16:50 MSK and 18:50 local time, the aircraft began its takeoff from Nizhnevartovsk Airport. However, during the acceleration on the runway, at a speed of 150 km/h, the flight engineer noticed, according to the cockpit voice recorder, that the "air starter open" light illuminated. Immediately after liftoff, the high-pressure compressor (HPC) RPM of engines No. 2 and 3 (center and right, respectively) dropped, and within a second, engine No. 1 (left) also experienced an RPM drop. Engines No. 1 and 3 then shut down, while engine No. 2's RPM initially fell to 74%, but then returned to takeoff power. By this time, the Yak-40 had climbed to an altitude of 35 meters. Losing thrust from two of its three engines, the aircraft began to lose speed and roll. Ninety-one seconds after liftoff, it crashed into the slope of a ravine 1 800 meters from the runway's end and 18 meters to the right of its axis, hitting a power line and completely disintegrating.^[2]

The air temperature at the time was −31°C. Rescue operations were conducted poorly, and the crash site was only located five hours later. By that time, only four passengers were still alive. The remaining four crew members and 23 passengers had perished.^[2]

Causes

The commission was unable to determine the exact cause of why the engines' RPMs dropped below the level required for horizontal flight in the takeoff configuration. There were only two main hypotheses:^[2]

1. When the flight engineer noticed the "air starter open" warning light, he might have set the throttle levers of all engines to idle, subsequently shutting down the outer engines by setting the throttle levers to "stop," or the engines might have shut down automatically due to the abrupt change in operating parameters. Since it was not possible to abort the takeoff at that moment, the captain ordered the flight engineer to move the throttle levers to the takeoff position, or he might have done it himself.
2. An airlock might have formed in the fuel system due to air ingestion. This could have caused the engines' RPM to drop, leading to their automatic shutdown, or the crew might have moved the throttle levers after noticing the engine failure, which also led to the engines shutting down automatically.

References

1. "Yakovlev Yak-40 Tail Number: CCCP-87549". Russianplanes.net. Archived from the original on 2013-05-01. Retrieved 2013-04-25.
2. "Yak-40 Crash of the Privolzhsk Civil Aviation Directorate near Nizhnevartovsk". airdisaster.ru. Archived from the original on 2013-01-22. Retrieved 2013-04-25.