What the ‘black box' can tell us about plane crashes

NEW DELHI — A preliminary finding into last month's Air India plane crash has suggested the aircraft's fuel control switches were turned off, starving the engines of fuel and causing a loss of engine thrust shortly after takeoff.

The report, issued by India's Aircraft Accident Investigation Bureau on Saturday, also found that one pilot was heard on the cockpit voice recorder asking the other why he cut off the fuel in the flight's final moment. The other pilot replied he did not do so.

The Air India flight — a Boeing 787-8 Dreamliner — crashed on June 12 and killed at least 260 people, including 19 on the ground, in the northwestern city of Ahmedabad. Only one passenger survived the crash, which is one of India's worst aviation disasters.

The report based its finding on the data recovered from the plane's black boxes — combined cockpit voice recorders and flight data recorders.

Here is an explanation of what black boxes are and what they can do:

What are black boxes?

The 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 great ocean depths. 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.

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 NTSB's website.

Depending on what happened, investigators may pay close attention to the engine noise, stall warnings and other clicks and pops, the NTSB said. 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. Experts make a meticulous transcript of the voice recording, which can take up to a week.

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.

Some can 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.

What are the origins of the black box?

At least two people have been credited with creating 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.

Warren had been investigating the crash of the world's first commercial jet airliner, the Comet, in 1953, and thought it would be helpful for airline accident investigators to have a recording of voices in the cockpit, the Australian Department of Defence said in a statement after his death.

Warren designed and constructed a prototype in 1956. But it took several years before officials understood just how valuable the device could be and began installing them in commercial airlines worldwide.

Why the name ''black box''?

Some have suggested that it stems from Hussenot's device because it used film and ''ran continuously in a light-tight box, hence the name ‘black box,''' according to Airbus, which 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.''