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A Qantas Boeing 747-400, operating Flt QF29 from Melbourne to Hong Kong has been involved in what the Australian Transport Safety Bureau calls a serious incident which caused minor injuries to 15 passengers on April 7.
According to the ATSB, the 747 was about to enter a holding pattern at Flight Level 220 (22,000ft) about 110km (60nm) southeast of Hong Kong at a waypoint called BETTY when the aircraft’s stick shaker activated.
The stick shaker is a mechanical device that noisily vibrates the pilot’s control column or yoke (the stick) to warn of an imminent aerodynamic stall.
(An aerodynamic stall occurs when the angle of attack of the wing causes the air moving over the upper surface can no longer remain attached to the surface and the flow breaks down causing a loss of lift and control.)
However, Boeing warns that “a stall must not be confused with the stall warning that alerts the pilot to an approaching stall. Recovery from an approach to stall is not the same as a recovery from an actual stall. An approach to stall is a controlled flight maneuver; a stall is an out-of-control, but recoverable, condition.”
The Qantas crew immediately disconnected the aircraft’s autopilot and recovered the aircraft manually, the ATSB said.
“While holding at flight level 220, the flight crew received a stick shaker activation and detected airframe buffeting,'' it said. " The flight crew disconnected the autopilot and manoeuvred the aircraft in response. Fifteen passengers received minor injuries.”
The 747 in question has continued to operate flights normally since the incident.
Qantas confirmed that passengers on QF29 experienced “unexpected turbulence’’ about an hour before landing.
The airline said the incident lasted about two minutes and the captain called for an ambulance to meet the aircraft on arrival.
The injuries were minor but one passenger was transferred to hospital for a precautionary medical assessment and later released.
“We notified the ATSB of the occurrence, and our own teams are also reviewing the event,’’ the airline said in a statement. “These investigations need to be completed before Qantas can comment further.”
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