The safety scare involving a Qantas jet last week is so rare and serious that most pilots go their whole career without encountering such a scenario, an aviation expert says.
Fifteen people were injured when the Qantas 747 flying from Melbourne to Hong Kong on April 7 had a “stick shaker” incident about 110 kilometres southeast of its destination, the Australian Transport Safety Bureau said.
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The ATSB, which is investigating the incident, said the pilots experienced “airframe buffeting” while holding at 22,000 feet and disconnected autopilot and “manouevred the aircraft in response”.
The safety watchdog is treating it as a “serious incident”, meaning there were indications that an accident causing loss of life or aircraft damage nearly occurred.
The “stick shaker” is a warning system that causes the aircraft’s control stick to vibrate, alerting pilots they are about enter a “stall condition”, said Keith Tonkin, an aviation expert and managing director of Aviation Projects.
“It’s unusual to have the stick shakers go off,” said Mr Tonkin, a former international Qantas pilot.
“It means that the aircraft is not able to sustain straight and level flight — the wings stop creating enough lift to hold the aeroplane up in the sky under controlled conditions.”
He said stick shaker incidents were so rare that most commercial airline pilots would go their whole career without encountering one, other than during training.
While it was not clear what had happened during the flight, Qantas has said the passenger injuries were sustained during “about two minutes” of unexpected turbulence.
The incident happened about 110 kilometres southeast of Hong Kong. Photo: Brent Winstone
Mr Tonkin said turbulence was therefore the likely cause of the stick shaker going off. A change in wind conditions or pulling power back too rapidly could also cause the plane to enter stall conditions, he said.
Pilots recover by lowering the plane’s nose into a descent and putting extra thrust on the engines, allowing it to build up enough speed to create lift and return to the right altitude, Mr Tonkin said.
However, that carries the risk of straying out of a plane’s allocated airspace, especially in busy airspace like that near Hong Kong.
“At a high altitude it’s recoverable within the height that you have, if it happened at a low level it may not be,” he said.
Qantas said the injuries suffered by passengers were “minor”, with two of them taken to hospital upon landing in Hong Kong as a precaution and later released.
The airline said it couldn’t comment further on the incident before the ATSB’s investigation was complete.