Tu-154 havariet i fjor - Merkelig sak - FlightGlobal

Erratic control preceded military Tu-154's fatal descent

05 JUNE, 2018 - SOURCE: FLIGHTGLOBAL PRO - BY: DAVID KAMINSKI-MORROW - LONDON

Documents apparently extracted from the Russian investigation into the military Tupolev Tu-154B crash in the Black Sea have given a more detailed insight into the circumstances of the accident.

Investigators have signalled that spatial disorientation contributed to the fatal crash, which occurred just 1min 13s after departure from Sochi on 25 December last year.

The document extract – which carries no official markings but appears consistent with the format of Russian government inquiries – has not been independently authenticated by FlightGlobal.

But it states that the aircraft (RA-85572), arriving from Chkalovsky airfield near Moscow, had been parked at Sochi for nearly 4h for refuelling before departing for Latakia in Syria.

The captain of the aircraft, while taxiing out, had experienced "difficulty" in determining location on the airport, the document adds, owing to the "complex" taxiway system and the two intersecting runways at Sochi.

Take-off commenced from runway 24 at 05:24 with a heading of 238°.

But just 7s into the roll, with the Tu-154 travelling at 38kt (70km/h), the captain started remarking – with a degree of stress – about the take-off heading.

Use of "abnormal vocabulary" and heightened "emotional tension" in this early phase resulted in the captain's reduced control of take-off parameters and the "diversion" of the crew from its functional duties, says the document.

After a 34s run, the Tu-154 lifted off with a pitch of 4° at a speed of 162kt (300km/h). The captain increased the pitch to 15° after retracting the undercarriage, then pushed the control column forward.

The captain ordered the flaps retracted at a height of 157m, which was a "departure" from the 500m agreed before flight, the document states.

While the flaps were being retracted and the stabiliser adjusted, the captain continued to push the control column forward. The aircraft reached 231m and started descending.

As it passed 218m – just 1min 3s into the flight – it was flying at 201kt, pitched 1.5° nose-down, and the descent rate of 1,180-1,575ft/min triggered the aircraft's hazardous approach warning system, designed to prevent a collision with terrain.

The document says the activation of the warning coincided with "erratic" movement by the captain of the control wheel, which was rolled 10.7° to the right then 53.5° left, while the left foot pedal was pressed and the control column was pulled. It states that the Tu-154 started banking sharply to the left, adding that the captain was experiencing spatial disorientation.

Crew members informed the captain about the hazardous approach warning and the loss of altitude. But by the time the aircraft was just 90m above the surface of the sea, it was descending at over 3,900ft/min at 250kt, with a 27° left bank, and unable to avoid impact with the sea.

The bank increased to 35° at 67m and the crew received a left-bank angle warning which prompted, at 34m, a hard maximum deflection of the control wheel to the right. But the Tu-154 struck the water with a bank of 50°, on a north-easterly heading, at nearly 6,000ft/min.

None of the 92 occupants survived the impact, some 1,270m from the coast and 340m to the left of the extended runway 24 centreline. The document says the "absence of an adequate reaction" from the captain to the crew's remarks, as well as audio and visual signals, as well as the lack of flight control to correct the descent led to the crash.