Il-12 crash on Mount Sivukha

The Il-12 crash on Mount Sivukha was an aviation accident involving an Il-12P passenger aircraft of Aeroflot that occurred on Thursday, 28 October 1954 in Krasnoyarsk Krai on the slope of Mount Sivukha, killing 19 people (according to unofficial data — 20 people).

Crash

On 27 October, while operating a passenger flight from Moscow, aircraft L1789 arrived in Novosibirsk, where there was a crew change. The new crew was to operate passenger flights 135/136 from Novosibirsk to Irkutsk and back. These flights were considered international, as they connected with flights 03/04 on the Irkutsk — Ulan Bator — Beijing — Ulan Bator — Irkutsk route, which were operated by the Soviet-Chinese airline SKOGA (Sino-Soviet Joint Stock Company). At 14:28 flight 135 took off from Novosibirsk and at 18:52 landed safely in Irkutsk. Next came the return flight 136 to Novosibirsk, but because of unfavourable weather conditions it was closed, and so, as changed, flight 136 was to be operated to Krasnoyarsk at flight level 2700 metres. The crew received the weather forecast only for the route to Krasnoyarsk. According to this forecast, variable (6-9 oktas) stratocumulus and fractonimbus cloud was expected on the route with a base of 600 to 1000 metres, and on the Tayshet-Kansk section with a base of 300 to 600 metres, middle, upper, precipitation, visibility from 4 to 10 kilometres, icing was observed in the clouds, and the mountains were obscured by cloud. In Krasnoyarsk itself variable upper stratocumulus cloud was expected with a base of 600 to 1000 metres, snow at times, north-westerly wind 6-9 m/s, gusting to 12 m/s, visibility from 4 to 10 kilometres. At flight level 1000 metres a wind of 200° 40 km/h was expected, at 1500 metres 240° 40 km/h, at 2000 metres 250° 50 km/h, and at 3000 metres 260° 60 km/h. At 21:09, with 13 passengers (9 foreigners from the connecting flight and 4 Soviet citizens from Irkutsk) and 6 crew members on board, the Il-12 took off from Irkutsk.

At 22:55 Nizhneudinsk was passed at a ground speed of 275 km/h. Up to this point the flight had proceeded above the clouds and without deviations. But from then on the aircraft was flying in cloud, in which light to moderate icing was observed. Probably relying on the weather forecast received in Irkutsk, the crew assumed that further on to Krasnoyarsk the wind was south-westerly at 40 km/h. However, already at 23:50 the aviation meteorological station (AMSG) in Krasnoyarsk received data that the wind was from the north-west, and at a height of 2000 metres its speed reached 130 km/h, that is, the aircraft was being drifted not to the north but to the south. However, these data were not passed on to the flight director at Krasnoyarsk airport, nor to the aircraft's crew. At 23:26 the crew received bearing data — a reciprocal bearing of 282° from Krasnoyarsk airport and a true bearing of 147° from Yeniseysk airport. These data indicated that since passing Nizhneudinsk, that is, in 31 minutes, the airliner had covered a distance of 132 kilometres and was 18–20 kilometres south of the airway. At 23:43 the aircraft reported passing Kansk, although, owing to the sluggishness of the senior controller of the Krasnoyarsk area control service, the radio beacon of Kansk airport was switched off at that moment. But at 23:54 the crew received new bearings — a reciprocal bearing of "about 280°" from Krasnoyarsk airport and a true bearing of 158° from Yeniseysk airport, that is, at that moment the aircraft was actually 73 kilometres from Krasnoyarsk, and based on the previously received bearings its ground speed was 435 km/h. On this basis it is clear that the crew reported passing Tayshet and Kansk relying only on calculations. The "approximate" reciprocal bearing of 280° passed to the crew was incorrect, which the radio operator reported to the ground. This error was caused by the fact that the radio direction finders in Krasnoyarsk were manned by trainees, since the regular staff, numbering 11 people, had been sent to serve in the Soviet Army.

The controllers should have understood that the data from the crew on their ground speed contradicted the data obtained from the bearings, but nevertheless they did not determine the aircraft's position precisely and gave the crew no instructions. The flight director and the senior controller of the area control service in fact made no calculations and did not direct the flight. In general, after 23:26 neither the crew, nor the flight director, nor the senior controller knew exactly where aircraft L1789 was. The fact that two previous Il-12s, operating flights from Irkutsk to Krasnoyarsk, had strayed south of the airway and arrived late, also bothered no one. Although according to the instructions entry into the zone of Krasnoyarsk airport was to be made at a height of 2100 metres, the controller instructed flight 136 to descend to a height of 1500 metres. However, the crew, …