How a black box works and what it found in the Air India flight crash report?

Hindustan Times

20 hours ago

A preliminary investigation into the deadly Air India crash of June 12 was released on Saturday, revealing details of the final moments of the ill-fated AI171 flight that was bound for London's Gatwick from Gujarat's Ahmedabad and crashed within seconds of takeoff into a medical hostel building. Wreckage of the Air India Boeing 787-8 Dreamliner plane sits on the open ground, outside Sardar Vallabhbhai Patel International Airport, where it took off and crashed nearby shortly afterwards, in Ahmedabad.(REUTERS)
The report by the Aircraft Accident Investigation Bureau (AAIB) said that both engines on the Boeing 787-8 Dreamliner lost thrust shortly after takeoff from Ahmedabad on June 12 — because the aircraft's fuel control switches had been turned off.
The report also included a tense exchange between pilots extracted from the cockpit voice recordings recovered from the black box. In the first few, which were also the final, seconds of the flight one pilot asked the other, 'Why did you cut off the fuel?' The response came, 'I did not do so,' according to the AAIB report.
The report based its finding on the data recovered from the Air India Boeing 787-7 plane's black boxes — combined cockpit voice recorders and flight data recorders.
What are black boxes?
Black boxes – cockpit voice recorder and the flight data recorder – are tools that help investigators reconstruct the events that lead up to a plane crash.
They're orange in color to make them easier to find in wreckage, sometimes at deep into oceans. They're usually installed a plane's tail section, which is considered the most survivable part of the aircraft, according to the National Transportation Safety Board's website.
Two people are believed to have been behind the creation of the devices that record what happens on an airplane.
One is French aviation engineer François Hussenot. In the 1930s, he found a way to record a plane's speed, altitude and other parameters onto photographic film, according to the website for European plane-maker Airbus.
In the 1950s, Australian scientist David Warren came up with the idea for the cockpit voice recorder, according to his 2010 AP obituary.
What does the cockpit voice recorder do?
The cockpit voice recorder collects radio transmissions and sounds such as the pilot's voices and engine noises, according to the National Transportation Safety Board's (NTSB) website. Black boxes generally survive fatal aviation accidents as they are built with multiple protective layers that include titanium or stainless steel outer shell that resists crushing and penetration; thermal insulation to withstand intense fire and shock-absorbing materials to protect internal electronics during violent impacts.
Depending on what happened, investigators may pay close attention to the engine noise, stall warnings and other clicks and pops, as per NTSB website. And from those sounds, investigators can often determine engine speed and the failure of some systems.
Investigators can also listen to conversations between the pilots and crew and communications with air traffic control, as mentioned in the AAIB preliminary report for the AI171 crash.
It, however, can take weeks for experts to make transcripts of the voice recordings.
What does the flight data recorder do?
The flight data recorder monitors a plane's altitude, airspeed and heading, according to the NTSB. Those factors are among at least 88 parameters that newly built planes must monitor.
Flight data recorder monitors collect the status of more than 1,000 other characteristics, from a wing's flap position to the smoke alarms. The NTSB said it can generate a computer animated video reconstruction of the flight from the information collected.
Why the name 'black box'?
According to an Associated Press news agency report, which cited Airbus, some have suggested that the term stems from Hussenot's device because it used film and 'ran continuously in a light-tight box, hence the name 'black box.''
Airbus noted that orange was the box's chosen color from the beginning to make it easy to find.
Other theories include the boxes turning black when they get charred in a crash, the Smithsonian Magazine wrote in 2019.
The media continues to use the term, the magazine wrote, 'because of the sense of mystery it conveys in the aftermath of an air disaster.'