Instruments on board the crashed Dagestan Airlines Tupolev Tu-154 had indicated fluctuations in the supply of fuel to the engines before two of them shut down in flight.

Initial information from the flight-data recorder shows that the instability showed up around eight minutes after the aircraft departed Moscow Vnukovo for Makhachkala, as the aircraft passed an altitude of 6,500m (21,300ft).

Russia's Interstate Aviation Committee says the fuel supply to all three engines was affected.

The aircraft continued to climb but, on reaching 9,000m, the left- and right-hand Soloviev D-30KU powerplants shut down leaving only the central engine available.

After the loss of power to the two engines, the crew put the tri-jet into a descent in order to carry out an emergency landing at Moscow Domodedovo.

While the central engine underwent a "period of instability" its operational status was "restored and maintained" until the aircraft landed at 14:36, some 35min after the engines were started.

The aircraft had been carrying 19.5t of fuel. Vnukovo Airport's operator has already checked the fuel supply and confirmed it meets required regulatory standards.

"The investigating commission is examining possible causes of the de-activation of the [left and right] engines during flight, and its impact on the performance of other aircraft systems," says MAK.

Both the primary flight-data recorder and a secondary data recorder contain a record of the incident. MAK says it is focused on retrieving the cockpit-voice recorder from the aircraft.

Source: Air Transport Intelligence news