Fifty people were treated after a LATAM flight from Sydney to Auckland suddenly plunged about 100 metres mid-flight. Photo: RNZ / Marika Khabazi
Authorities are examining the black box of a Boeing 787-9 Dreamliner that suddenly lost altitude on a Sydney-Auckland flight, injuring scores of passengers and crew.
Travellers suffered head and neck injuries and broken bones when they were flung across the cabin on board LATAM flight LA800 on Monday evening. Fifty people were treated and 12 hospitalised.
Aviation lawyer Mary Schiavo, the former head of the US National Transportation Board, earlier said the black box data would be "very important" in showing exactly what happened during the flight.
"As soon as they download that black box information they probably will have solved the mystery," she told Morning Report.
But what is a black box and what data does it hold? Experts from Massey University and Otago University have the answers.
What is a black box?
Contrary to popular belief, the 'black box' is not a single box that provides information.
Ashok Poduval, the chief executive officer of the school of aviation - te kura rererangi at Massey University, says commercial airliners like the Dreamliner have two key recorders inside.
One is the cockpit voice recorder, which "records communication on the flight deck between the pilots as well as between pilots and air control".
The second is the digital flight data recorder. That stores a host of information from the flight, including altitude and engine performance.
According to the BBC, the containers those recorders are placed in are not black at all - they are painted bright orange so they can be easily spotted in wreckage.
Each container, which is about the size of a shoebox, contains a thermal block and insulation to protect the recorders' memory boards and the information they store.
The shells are made of corrosion-resistant stainless steel or titanium and can withstand heats of more than 1000 degrees Celsius and water immersion to a depth of 6000 metres.
Black boxes also contain a beacon, which cannot be heard by humans but is easily detectable by sonar, according to NPR.
The beacons' batteries have a shelf life of up to six years and they send a signal every second, even when deep underwater.
What can the Dreamliner's black box tell us about the flight?
The digital flight data recorder stores detailed evidence of any control inputs made by the crew, Otago University Emeritus Professor David O'Hare says.
It also stores flight parameters showing airspeed, altitude and control settings.
"This would show, for example, if there had been an autopilot disconnect and whether this was associated with any pilot input," O'Hare, who has researched pilot decision making and aviation safety and holds a flight crew licence, says.
The cockpit voice recording will be able to tell investigators what the crew said before, during and after the incident.
It will also have stored background sounds - for example, the audible sound of the autopilot being disconnected.
When will we know what the black box says?
Schiavo says investigators will have a "pretty good idea of what happened" within a week, after downloading the data from the black box.
However, the public may not know for 30 days, which is the amount of time investigators have to put out a preliminary report.
Both O'Hare and Poduval say it is important not to jump to any conclusions about the cause of the flight before the black box is analysed.
"There is no reason to connect this incident with other recent events involving Boeing airliners and nothing that we know at this point suggests any systemic problems with the 787 or any maintenance or inspection issues," O'Hare says.
"Proper investigation takes time so it is far too early to go down this route."
Clear air turbulence - the movement of air masses in cloudless air - would be the "most probable cause" of the incident, he says.
"If there are other factors involved they will be identified following careful investigation and analysis."
Poduval also says it is "premature" to draw conclusions about the safety of Boeing 787s.
"Until the air safety investigation is completed, which will include analysis of the data from the recorders and interviews with the pilots, we cannot make any determinations as to the cause of the incident."