Bek Air is still pushing its theory that wake turbulence contributed to the loss of a Fokker 100 during take-off from Almaty, and is also indicating that the proximity of buildings should be examined by the inquiry.
The airline has released further flight data which, it says, has been obtained from the aircraft – including rudder and aileron positions, engine power, and wind speed information.
Little context or clarification accompanies the data, however, which appears to cover a longer time interval than the 36s previously disclosed.
It appears to show the ailerons, rudder and elevators were active during rotation, as the aircraft experienced lateral and longitudinal instability during the brief period it was fully airborne.
Some of the data – such as the airspeed – is discontinuous, suggesting it has been sourced only after the jet lifted off, while other information, like sudden changes in wind speed and direction, is likely to be unreliable because the aircraft, having descended back to the ground, subsequently travelled at an unusual attitude, barely above the terrain.
After the aircraft lost height, the data suggests thrust on both Rolls-Royce Tay engines simultaneously reduced for around 10s before increasing to a higher level than before the power dip.
Bek Air has acknowledged the surveillance video showing the de-icing of the aircraft’s horizontal stabiliser, a video which does not indicate any de-icing of the wings.
The airline has released a document on de-icing fluid hold-over times, which appears to highlight a figure of 45min for Type I fluid in frost below minus 10C. Such fluids are not particularly viscous and are intended for short-term use.
Bek Air has also published documentation detailing the threat from wake vortices and the efforts to counter the problem.
But air navigation service Kazaeronavigatsia has already insisted that the 2min interval between the Fokker 100’s departure and that of a preceding aircraft was sufficient for wake vortex separation.
Bek Air’s latest information briefing – which is not an official part of the inquiry – also features a list of 2011 regulations regarding permission for the construction of buildings in proximity to airports.
Russian and Kazakh investigators have yet to disclose any formal information of the 27 December accident sequence, which resulted in 12 fatalities.