Russia Black Sea air crash: Pilot error blamed
Russian investigators say the December crash of a Tu-154 airliner in the Black Sea, which killed 92 people, was most likely a case of pilot error.
The military flight was on its way to Syria, carrying members of the Alexandrov music ensemble, when it plunged into the sea on 25 December.
Analysis of the flight data suggests the pilot lost his bearings and ignored his instruments, believing that the jet was climbing too sharply.
Tiredness was thought to be a factor.
The Russian defence ministry's report said the cause "could have been disruption of the flight captain's spatial and situational awareness, which led to him making errors".
The report stressed that no violations of refuelling rules were found, nor was there any evidence of an external factor in the crash. It is the end of the official inquiry.
The Tupolev plane had taken off earlier that morning from Chkalovsky military airbase near Moscow, and had refuelled at Adler airport near Sochi.
Disaster struck as the jet was climbing away from Adler, en route to Russia's Hmeimim airbase, outside Latakia in Syria.
Russia's Kommersant daily says all the evidence points to Maj Roman Volkov having suffered from "somatogravic illusion" - a condition that can affect a pilot's sense of balance during rapid acceleration or deceleration.
Experts quoted by the daily said Maj Volkov was already feeling unwell on the ground - he had had trouble getting the plane on to the correct runway for take-off.
As the plane was gaining height he started issuing incoherent instructions to the crew and pushed the control column forwards, sending the plane into a steep dive, Kommersant reported (in Russian).
The plane lost height at 6-8 metres per second (20-26 ft/sec) and the alarm went off. But then the pilot made an abrupt manoeuvre, from executing a starboard turn with a 10-degree bank to a 53-degree bank to the left.
In the 70th second of the flight, the plane had dropped to just 90m (295ft) above the water, and it was diving at a rate of 20m/sec.
It broke up on impact, hitting the surface at 540km/h (336mph), with a 50-degree bank, and all aboard were killed.
The Alexandrov Ensemble - the official choir of the Russian armed forces - was scheduled to perform a New Year's concert at Hmeimim.
Those on board also included nine journalists, eight soldiers, two civil servants and eight crew members.
Among the victims was Yelizaveta Glinka, known as Dr Liza, the executive director of the Fair Aid charity and the inaugural winner of Russia's state prize for achievements in human rights.