Accident
Flight L3904 was operating a non-scheduled flight from Magadan to Khabarovsk with intermediate stops in Okhotsk and Nikolayevsk-on-Amur. The first leg of the flight proceeded without incident. During preparation for the flight, the airport navigator did not verify whether the crew had correctly calculated the flight, and the flight plan was not approved. Nevertheless, the airport dispatcher authorized the flight. With 4 crew members and 24 passengers (21 adults and 3 children) on board, the Il-12 departed from Okhotsk. At that time, due to adverse weather conditions, the Nikolayevsk-on-Amur Airport was closed, so the aircraft was to fly past it without landing. According to the weather forecast provided to the crew, the route from Okhotsk to Khabarovsk was expected to have continuous mid-level cloud cover, with stratiform and ragged clouds with bases at 200-300 meters above the Okhotsk airfield level, where icing, precipitation, and visibility of 2-4 kilometers were observed. Closer to the end of the route, the cloud base was expected to rise to 300-600 meters, and visibility was expected to increase to 10 kilometers. The hills were covered by clouds. In Khabarovsk itself, variable (6-9 octas) stratocumulus cloud cover with a base of 300-600 meters, rain, visibility over 10 kilometers, and a west wind of 5-8 m/s were forecasted. Later, during the investigation of the accident, testimony from crews that flew the same route before and after flight L3904 was obtained. These testimonies indicated that the route actually had dry and wet snow, moderate icing, and the wind was actually from the north-northwest at up to 19 m/s, meaning the weather forecast provided in Okhotsk was inaccurate. Moreover, due to the falling snow, the range of the NDBs was reduced to 15-20 kilometers, and two-way radio communication was degraded, while the radio compasses were working erratically. In addition, Captain Konoplev did not visit the AMSG and did not receive a synoptic consultation [1] .
While flying the Okhotsk-Nikolayevsk leg, the crew took bearings three times, ensuring that after 1 hour and 3 minutes from takeoff, they were still on course. At 11:58 [* 1] , the crew attempted to contact the Nikolayevsk airport dispatcher, but these attempts were unsuccessful. At 12:22, flight L3904 reported passing Nikolayevsk, but this was not confirmed by the Nikolayevsk dispatcher, and the exact overflight location was not determined. The Nikolayevsk airport dispatcher relayed the overflight time to the Khabarovsk district dispatching service but did not disclose that the overflight time had not been accurately determined and that no communication with the aircraft had been established. At 13:16, while cruising at 2,700 meters with a ground speed of 350 km/h, the crew reported passing Nizhnetambovskoye, adding that they were not receiving signals from the NDBs. At 13:32, flight L3904 reported visually passing Komsomolsk, although other crews claimed there were no conditions for visual flight in the Komsomolsk area. At 13:51, the crew reported passing Troitskoye, without specifying the flight conditions. At 14:14, they transmitted: "According to calculations, passed Yelabuga, 2,700 meters in clouds, the compass is not working, permission to descend and guide by radar requested." After passing Troitskoye, the district service dispatcher handed off the aircraft to the area control center (ACC). The district service dispatcher did not receive confirmation of communication establishment with the ACC and did not report the handoff to the ACC. Flight L3904 could not establish direct communication with the ACC and was relaying messages through another Il-12P aircraft (tail number USSR-L12586), receiving permission to descend to 2,400 meters. The ACC duty officer informed the district service dispatcher that communication with flight L3904 had not been established. The radio operator of flight L3904 spent a long time unsuccessfully trying to contact the ACC via VHF, while simultaneously establishing communication with the short-wave direction finder at Khabarovsk airport, from which he received a bearing: "approximately 312°". The direction-finder operator relayed this bearing along with the flight number to district service 2, operating in the western direction, but was told by phone that the aircraft was not there. This bearing was not reported to the dispatchers or the flight operations manager [1] .
At 14:20, the ACC duty officer received a phone call from an air defense officer, reporting that an unidentified aircraft was observed near Yedinka at the intersection of the Yedinka-Khabarovsk route. However, the response came from a female voice, who stated that there were no aircraft in that area. Later, the commission concluded that this voice belonged to the district service operator, although she denied it. At 14:23, the crew of flight L3904 made another unsuccessful attempt to obtain a bearing from the short-wave direction finder. Between 14:30 and 14:40, the crew reported: "Altitude 2,400 meters, 14:15 by calculation - Khabarovsk." The district service dispatcher did not know the exact location of the aircraft but nevertheless instructed them to descend to 1,800 meters and request a bearing from the military via VHF. At 14:33, the crew reported reaching 1,800 meters, and the dispatcher instructed them to descend to 1,500 meters and correct their course to compensate for wind drift. The crew reported: "Course 50, intermittently visual. Calculated to have passed Khabarovsk, turning back." The dispatcher instructed them to follow the short-wave direction finder bearing. However, this direction finder had been out of service since 27 August, three weeks prior, due to ongoing maintenance. Direction-finder operators were instructed not to determine bearings or transmit them to aircraft. Therefore, the crew received only very approximate bearings from the medium-wave direction finder. At 14:50, the crew confirmed to the district service that they had received the medium-wave bearing and set the course accordingly. Also, at 14:43, the crew reported a fuel remaining of 800 liters, and at 15:00 - only 600 liters, prompting the dispatcher to instruct them to proceed to Khabarovsk in fuel-efficient mode [1] .
Doubting the accuracy of the bearings received, the crew continued to request bearings until 15:19. In response, the dispatcher stated: "The bearing is correct, take a course of 290°, maintain altitude at 3,300 meters." It is worth noting that the aircraft had already been gradually climbed first to 1,800 meters and then to 2,700 meters. At 15:19, the crew reported that their ground speed was 190 km/h and requested the distance to Khabarovsk. The dispatcher informed them that the distance was 210 kilometers, and at 15:36, they transmitted: "Distance 210 kilometers, heading 110°." Five minutes later, at 15:41, the crew reported: "Remaining fuel 450 liters, ground speed 200 km/h, altitude 3,300 meters in clouds." To this, the dispatcher replied at 15:43: "Distance 190 km, you are moving slowly," and at 15:47 instructed them to descend to 2,700 meters and set a course of 300°. At 15:52, the crew reported that they were following a course of 300° and had 300 liters of fuel remaining. At 15:57, they reported a remaining fuel of 210 liters, indicating that they should prepare for a forced landing by selecting a suitable area. The dispatcher informed them that they were 150 kilometers from Khabarovsk and instructed them to descend to 2,100 meters. At 16:05, the crew reported a remaining fuel of 200 liters, and at 16:07: "Descending to visual on lights." At 16:11, the crew reported that they were at 1,500 meters and the ground was barely visible, and a minute later, they reported flying at 1,200 meters in variable cloud cover and beginning the search for a landing site. The district service dispatcher instructed: "Do not land until fuel is exhausted." At 16:14, flight L3904 transmitted its last message: "Altitude 1,000 meters, ground not visible, flying in clouds, seeing nothing." One minute later, at 16:15 (23:15 local time), the Il-12 entered a nearly vertical descent and crashed into the ground [1] .
The accident occurred in the Lazo District (Khabarovsk Krai) at an altitude of 850 meters on the slope of a mountain with a height of 1,050 meters, 145 kilometers southeast (bearing 137°) of Khabarovsk and 35 kilometers east-northeast (bearing 74°) of the village of Khody. All 28 people on board perished [1] .
Causes
The forecast of a fresh west wind turned out to be incorrect. Meanwhile, unaware of this, the crews, in an attempt to prevent drift, effectively began to move the aircraft west of the route. According to data provided by the air defense, the Nikolayevsk-on-Amur airport was overflown to the west by up to 55 kilometers. Based on this data, it was established that the Nikolayevsk airport dispatching service did not manage or control the flights. Flight L3904 passed the airport zone 24 kilometers west of Nikolayevsk, while the snowstorm reduced the range of the NDBs to no more than 20 kilometers, and the range of two-way radio communication was even less, which is why the crew could not establish contact with the airport. Although the dispatchers had functional and operational radio equipment, they did not use it for monitoring and managing flights, leading aircraft to follow routes to Khabarovsk 30-40 kilometers left of the course. Additionally, the district service dispatcher did not control the transition of crews to communication with the ACC. Meanwhile, flight L3904 significantly deviated to the left and overflew Khabarovsk [1] .
When the aircraft did not land in Khabarovsk at the scheduled time of 14:15, the dispatching service did not raise any concerns and only noticed it 15 minutes later. The air defense report of an unidentified aircraft in the Yedinka area also did not raise concerns. Furthermore, when the crew managed to contact the short-wave direction finder and received a bearing, the district service did not relay this information to the flight operations manager or the dispatching staff. Flying at night in difficult weather conditions, the crew became disoriented. From 14:16 to 15:19, when attempts were made to obtain bearings from the short-wave direction finder, the Il-12 effectively began to circle in one area. Only at 15:20 was the actual location of flight L3904 determined, but by then, it was too late, as the remaining fuel supply, considering the strong headwind from the north, did not allow them to reach Khabarovsk. There was a backup airfield at Yedinka, but the flight operations manager and air traffic controllers were unaware that it had a ground radar transponder and did not take the necessary measures to prepare the airfield for receiving the aircraft. The Yedinka airfield dispatcher heard the radio communications of flight L3904 with the ground but did not intervene, even though he could have saved the aircraft. Not knowing the exact location of the aircraft, the dispatchers, in violation of instructions, began to descend it over a mountainous area [1] .
