Narrative:
Aileron oscillations coincided with flap extension. The crew misunderstood this as asymmetrical flap extension and retracted the flaps again. The airspeed had dropped to 172 knots. The aileron suddenly deflected then , causing a left roll. The aircraft undershot the runway.
The hinge moment reversal on the ailerons and subsequent loss of control was caused by icing.
Loss of control
» NTSB/AAR-96/02 (144)
| Status: | Accident investigation report completed and information captured |
| Date: | Sunday 31 January 1971 |
| Type: |  Antonov An-12B |
| Operator: | Aeroflot, Tyumen Civil Aviation Directorate |
| Registration: | CCCP-12996 |
| MSN: | 00347403 |
| First flight: | 1970 |
| Engines: | 4 Ivchenko AI-20M |
| Crew: | Fatalities: 7 / Occupants: 7 |
| Passengers: | Fatalities: 0 / Occupants: 0 |
| Total: | Fatalities: 7 / Occupants: 7 |
| Aircraft damage: | Damaged beyond repair |
| Location: | 14 km (8.8 mls) N of Surgut Airport (SGC) ( Russia)
|
| Phase: | Approach (APR) |
| Nature: | Cargo |
| Departure airport: | Tyumen-Roschino International Airport (TJM/USTR), Russia |
| Surgut Airport (SGC/USRR), Russia |
Aileron oscillations coincided with flap extension. The crew misunderstood this as asymmetrical flap extension and retracted the flaps again. The airspeed had dropped to 172 knots. The aileron suddenly deflected then , causing a left roll. The aircraft undershot the runway.
The hinge moment reversal on the ailerons and subsequent loss of control was caused by icing.
Classification:
IcingLoss of control
Sources:
» Soviet Transports» NTSB/AAR-96/02 (144)
Photos
Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Tyumen-Roschino International Airport to Surgut Airport as the crow flies is 645 km (403 miles).
Accident location: Approximate; accuracy within a few kilometers.
Distance from Tyumen-Roschino International Airport to Surgut Airport as the crow flies is 645 km (403 miles).
Accident location: Approximate; accuracy within a few kilometers.
This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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