Antonov AN-12 Cargo Crash Near Omsukchan (RA-11125)

Incident Overview and Flight Details On the day of the accident, a four-engine Antonov AN-12 departed Komsomolsk-on-Amur Airport at 1437 local time on cargo flight LN9209. The aircraft was en route to Keperveyem with an intermediate stop at Magadan. It carried 17.43 tons of various goods, two passengers, and a crew of nine, for a total of 11 occupants. ## Emergency Development and Crash At 1520 local time, while cruising at 7,500 meters approximately 430 kilometers northeast of the departure point, the crew reported a fuel leak on engine number 1 to air traffic control. They requested a descent to 6,600 meters and clearance to return to Komsomolsk-on-Amur. After engine number 1 caught fire, the crew declared an emergency and began an emergency descent. The aircraft became uncontrollable and crashed on the slope of a mountain about 82 kilometers southwest of Omsukchan. The aircraft disintegrated on impact, and debris was found the following day at an altitude of 1,006 meters. All 11 occupants were killed. ## Official Probable Cause The official investigation identified the probable causes as the loss of longitudinal (roll) control following the in-flight shutdown of engine number 1 and feathering of its propeller. This loss of control was attributed to the load-bearing properties of the left wing and possible damage to the left-hand aileron control wiring, leading to an uncontrolled excessive roll to the left and subsequent terrain impact. The fire originated in the tail section of the number 1 engine nacelle and spread forward onto the wing. It was most likely fed by fuel leaking from a fuel line connection to the low-pressure fuel pump at engine number 1, with ignition likely caused by contact with hot engine parts. Due to disintegration and fire damage, the exact location of the fuel leaks and the precise cause could not be established with certainty. Contributing factors included the fire suppression system's inability to extinguish the fire in its early stages and the absence of checklists or guidelines in the flight manual for fuel leaks inside the engine nacelle, which delayed the engine shutdown by more than two minutes. The mountainous terrain, low-level overcast cloud, and lack of time due to the continuing fire prevented the crew from selecting a suitable site for an emergency landing.