A Qantas 747-400 leaving Sydney airport.

The Australian air safety investigator the ATSB is sparing in its use of the term ‘serious incident’ which it has applied to the apparent control and turbulence issues that coincided with minor injuries to 15 Qantas passengers in a 747-400 approaching Hong Kong airport last Friday, April 7.

The ATSB has in the past said a ‘serious incident’ was one which had the potential to cause a crash.

That makes this inquiry of the highest importance, but it doesn’t permit premature conclusions to be drawn from the small amount of publicly available information, as carried by various media reports like this.

The fact that the stick shaker warning was activated is an indication that the 747-400 was in a situation where a further decline in its airspeed would put it at risk of a stall.

On the other hand stick shaker warnings are designed to alert pilots to the impending risk of such an event. They do not go off at the very final moment, but at a moment when prompt action will remedy the situation.

There is no suggestion that the Qantas pilots didn’t promptly and professionally respond to the warning and deal with it as effectively as possible. The paucity of information available doesn’t give an insight into whether all of the related systems on the jet were functioning properly, or that the warning was ‘real’, or that the turbulence experienced in the jet was in fact directly related to the onset of low speed buffeting in the airframe.

In short, there is no reason at this stage to jump to conclusions about the answers to what are important questions.

What can be highlighted is that air traffic vectoring on approach to Hong Kong airport is notably complex and naturally prone to turbulence because of a combination of the constraints of surrounding PRC air space management, and disturbances that can be caused by the uneven terrain that is flown over.

A fact based insight into the conditions that prevailed when this incident occurred can be found in this Aviation Herald report.

As this extract makes clear, this was a very bumpy ride.

Data off the ADS-B capable transponder of the aircraft suggest the aircraft was descending to enter the hold at about 340 knots over ground on a track of 315 degrees, when descending through FL229 at 17:47L (09:47Z) the speed decayed to 290 knots over ground still on a track of 315 degrees before increasing to above 400 knots over ground in altitude fluctuations between FL214 and FL230 before levelling off at FL220 at 390 knots over ground subsequently reducing to 340 knots over ground.

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