What happened
On March 2, 20 and 2017, a Mil Mi-8MTV-1, registration RA-25129, operated by ALROSA SA, was performing a scheduled transport mission (flight YM-9935) under a request from Almaz Anabara. The flight plan involved a multi-stop route starting from Verkhneye Molodo, passing over the Saloli River, visiting Drilling Sites No. 3 and No. 4, continuing to Prilensk, then to Zhigansk airfield, and finally returning to Verkhneye Molodo. The primary purpose of the flight was to transport shift workers between these locations.
The flight crew received flight permission from the Yakutsk Air Traffic Control Center on March 1, 2017. Before departure, the pilot-in-command conducted the required medical examinations for the crew, as per regulations allowing the commander to authorize flight readiness in locations lacking medical personnel. The crew also reviewed weather forecasts, including the GAMET zonal forecast for the Yakutsk area.
The flight operations began at 01:36 with a takeoff from Verkhneye Molodo. The aircraft proceeded through the route, performing landings at the drilling sites without shutting down the engines to facilitate the rotation of personnel. The aircraft landed at Prilensk at 03:48. Following this, the crew departed Prilensk at 04:58, heading toward Zhigansk airfield. The aircraft arrived at Zhigansk at 07:16, where it underwent refueling with TS-1 fuel. The final leg of the flight, departing Zhigansk for Verkhneye Molodo, commenced at 07:57 under visual flight rules.