Date & Time: Oct 18, 1977 at 1156 LT
Type of aircraft:
Scheduled Revenue Flight
Srednekolymsk – Nalimsk
1123 473 05
Crew on board:
Pax on board:
After takeoff from Srednekolymsk Airport, while climbing to a height of 150 meters, the engine started to misfire. Power dropped and fire sprayed out from the right side of the engine. The crew elected to make an emergency landing but inadvertently switched off the battery so he was unable to lower the flaps. The airplane crash landed at high speed, lost its undercarriage and lower wings and came to a halt, broken in two. All five occupants were quickly rescued while the aircraft was destroyed.
The accident was the consequence of the engine misfiring as a result of a failure of the rear spark plug on cylinder n°2, which occurred as a result of the central electrode falling out of the candle with subsequent burning of its body in the cylindrical part near the turnkey hexagon. The falling out of the central electrode of the rear spark plug of cylinder n°2 was caused by the destruction of the insulator due to the formation of a microcrack and internal stresses in the insulator in the process of making candles. According to the conclusions of the State Research Institute of Civil Aviation, this defect was the consequence of a faulty design and manufacture.