Date & Time:
Mar 2, 1986 at 0304 LT
Type of aircraft:
Antonov AN-24
Operator:
Registration:
CCCP-46423
Flight Phase:
Landing (descent or approach)
Flight Type:
Scheduled Revenue Flight
Survivors:
No
Schedule:
Moscow - Cheboksary - Bugulma
MSN:
0 73 041 08
YOM:
1970
Flight number:
SU77F
Country:
Russia
Region:
Asia
Crew on board:
4
Crew fatalities:
4
Pax on board:
34
Pax fatalities:
34
Other fatalities:
0
Total fatalities:
38
Aircraft flight hours:
31570
Aircraft flight cycles:
23765
Circumstances:
On approach to Bugulma Airport by night, the left propeller autofeathered. The aircraft speed dropped and the aircraft started to veer to the left. The crew elected to maintain directional control but the speed continued to drop. At a speed of 140 km/h, the aircraft banked left to an angle of 110° then stalled and crashed in a field located 8 km from the runway threshold and 500 meters from its extended centerline. The aircraft was totally destroyed and all 38 occupants were killed.
Probable cause:
The left propeller autofeathered one second after the flaps were deployed in an angle of 38° because an electrical switch connected to the automatic feathering system failed. This situation affected the aircraft stability and controllability and the crew was unable to correct abnormal yaw and roll following several errors.
