Qantaslink B717
PILOTS flying a Qantas regional service with more than 100 passengers wrestled with shaking joysticks warning of an aerodynamic stall during two botched landing attempts at Kalgoorlie after they unwittingly programmed the flight computers with wrong data.
A slip-up by the captain, unnoticed by the co-pilot entering the data, meant the plane’s weight was calculated to be almost 9.5 tonnes lighter than it really was, investigators from the Australian Transport Safety Bureau found.
That mistake meant the settings for landing angle and speed were wrong for the task, twice triggering automated ”stick shaker” warnings to alert pilots to an impending aerodynamic stall – when the plane is no longer aerodynamically stable and in danger of dropping from the sky.
The first stick shaker warnings triggered at 335 metres, and again during the second landing attempt at 106 metres, before pilots managed to land on a third attempt.
But during the landing attempts the pilots had not identified the underlying reason why the plane was unstable, pitching and increasingly difficult to control – mistakenly attributing the shakes to air turbulence.
”In response to the stick shaker activations, the flight crew did not follow the prescribed stall recovery procedure and did not perform an immediate go around [aborted landings],” investigators found.
Investigators examining the incident, which occurred on a Boeing 717 flight from Perth under the banner of QantasLink operated by Cobham Aviation Services on October 13, 2010, found a lack of standard cross-checking routines let the data mistake slip through.
Although ”well rested”, the captain, who made the initial weight mistake, ”had been subject to numerous [roster] changes that had made it difficult to manage his level of fatigue,” investigators said.
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