Russian investigators have found that a Mil Mi-8T helicopter captain’s decision to descend in limited visibility, while operating in mountainous terrain, led to a fatal collision with a ridge, with no survivors from among the 22 occupants.
The Vityaz Aero helicopter (RA-25656) had lifted off from the vicinity of the Vachkazhets volcano on a return flight to the settlement of Nikolaevka-2 – about 10nm from Petropavlovsk-Kamchatsky’s Elizovo airport – on 31 August last year.
Prior to the accident it had flown from Nikolaevka-2 to Vachkazhets with 12 passengers. During a brief 2min stop – without turning off the engines – the crew dropped off five passengers and took another 12 on board, before continuing to another nearby landing site.
Some 30min later the aircraft prepared to depart again, with the 19 passengers and three crew, for the return flight to Nikolaevka-2.
Russia’s Interstate Aviation Committee says weather observations and video recordings indicate that, along the planned flightpath, clouds had developed and were moving in the direction of the Vachkazhets volcano.
The helicopter took off at around 16:04 and headed for the advancing clouds, climbing to 1,400m (4,600ft) in a region where terrain elevation rose to 1,200m.
Despite seeing that the changing meteorological conditions were no longer compatible with visual flight rules, the crew “continued the flight”, says the inquiry – a decision which “contradicts” the requirements of Vityaz Aero.
Shortly after take-off, the captain contacted air traffic control, informing that they expected to arrive at Nikolaevka-2 in around 15min.
“Most probably, the crew was flying above the cloud tops or between cloud layers at 1,400m,” the inquiry states.
But about 1min later the captain put the helicopter into a descent at about 2m/s (390ft/min). The inquiry says it is unable to assess the reason for this decision, because there is no recording of the crew’s cockpit conversation.
At an altitude of 1,270m the descent rate increased to 5.4m/s (1,060ft/min).
Investigators state that the helicopter was heading for a ridge perpendicular to the flightpath, and descending in visibility of less than 100m.
At an altitude of 900-910m the Mi-8 was some 20-25m below the ridge summit when a sudden increase in pitch indicates that the captain attempted to avert a collision with the terrain.
The helicopter was pitched 35° nose-up, and travelling at 91kt (168km/h), when its tail boom struck the western ridge slope at 930m.
Damage to the boom structure and tail rotor caused the helicopter begin rotating uncontrollably around its vertical axis, with rolling and pitching of up to 55°. It flew over the ridge summit, before losing speed and descending, crashing onto the eastern slope at an altitude of 900m where the wreckage was consumed by fire.
Investigators point out that, during the helicopter’s flight from Nikolaevka-2 to Vachkazhets and back, only a single ‘dangerous altitude’ alert was captured by the flight-data recorder. The inquiry says the absence of alerts, even during the landings at Vachkazhets, indicates the crew had set the alert threshold for the radio altimeter outside of the proper range.
Vityaz Aero has suffered three other accidents with Mi-8 helicopters since 2015 involving crews encountering limited-visibility conditions while operating in mountainous areas. The inquiry says the Vachkazhets collision occurred despite the company’s introducing a new flight-safety manual in 2022.
