Australian investigators have detailed the dynamics of the in-flight upset which injured over 70 people on board a Qantas Airbus A330-300 during cruise, but have no firm indication as to the cause of the incident.
The jet, en route from Singapore to Perth, climbed 200ft upwards before returning to its cruising altitude of 37,000ft. About one minute later, it descended 650ft in the space of 20s - pitching downwards to a maximum of 8.4° - before regaining its cruise level once more.
Seventy seconds later it descended again, by 400ft in 16s, with nose-down pitch of 3.5°.
Australian Transport Safety Bureau director of air safety investigation Julian Walsh says the agency has determined there was no shift in cargo and no structural defects in the twin-jet. The bureau has released an animation of the event, drawn from initial flight-data recorder information.
"As far as we can understand, there seems to be issues with some on-board components," he says, adding that the event was "very complex" and that the bureau needs to examine the flight-control computers and the data sources in use.
Early information pointed to the pilots' receiving messages on the jet's electronic centralised aircraft monitoring system relating to an "irregularity" with the A330's elevator-control system.
"Certainly the aircraft has pitched down without any input from the pilots," says Walsh.
"We don't have a detailed understanding of the interaction of pilot with the aircraft controls, but what were seeing at the moment indicates normal [pilot] responses to what the aircraft is doing."
He says the autopilot was engaged before the incident, adding: "The autopilot is one of the aspects of the investigations. There's quite a complex interaction between the autopilot and other systems.
"That's going to be something we're going to have to look at, in terms of when the autopilot turned off and turned on - whether it turned off of its own accord, for some reason, or whether it was deselected by the pilot, or reselected by the pilot."
Walsh says that while the nature of the initiating event has not been determined, there is "no evidence" that passenger electronic devices might have contributed to the upset, in which 14 occupants received serious injuries. "There's certainly nothing we're aware of [regarding electronic devices] that's caused any sort of serious event like this," he says.
"We don't understand the circumstances yet, we're not aware of a similar event in the past," he states, adding that the inquiry will examine atmospheric conditions as well as the technical issues.
Qantas flight QF72 was transporting 303 passengers and 10 crew when the incident occurred on 7 October, about 110nm (204km) north of Carnarvon in western Australia. The aircraft subsequently diverted to Learmonth.
"Damage was quite extensive inside in terms of cracked roof panels where people's heads have hit the cabin roof, and perhaps objects as well," says Walsh.
"We cannot pre-empt the findings in relation to cabin safety issues and the wearing of seat-belts but this accident does serve as a salient reminder to all people who travel by air of the importance of keeping seat-belts fastened at all times."
Preliminary factual data from the event will be released in a bureau report in around 30 days.
Source: Air Transport Intelligence news