Air India crash: Black box found — What is it and how it can help unravel the mystery behind tragedy

The aircraft, flight AI-171 issued a MAYDAY call shortly after taking off, according to the Directorate General of Civil Aviation

Authorities have recovered one of two black boxes of the London-bound Air India flight that crashed in a crowded area near Meghaninagar in Ahmedabad, just minutes after taking off from the Sardar Vallabhbhai Patel International Airport.

The Directorate General of Civil Aviation will collect the equipment to analyse the recordings.

The Boeing 787 Dreamliner aircraft (AI171) was carrying 242 passengers, including 169 Indian nationals, 53 British, seven Portuguese and one Canadian. The tragic incident occurred around 1.39 pm local time (08.09 GMT). Vishwash Kumar Ramesh, 40, the sole survivor, was sitting on seat 11A when the plane crashed.

The aircraft, flight AI-171 issued a MAYDAY call shortly after taking off, according to the Directorate General of Civil Aviation (DGCA). The plane crashed in the Meghani Nagar area outside the airport perimeter after reaching just 625 feet altitude, exploding in a massive fireball.

What is a black box?

Aircraft "black boxes" are bright orange rectangular crash-resistant devices that are designed to survive extreme impact and fire. Every commercial aircraft carries two such recorders. It is basically a flight recorder, with origins in the early 1950s. Australian scientist Dr David Warren (1925–2010) invented the world's first flight recorder.

The two black boxes of any aircraft are the cockpit voice recorder (CVR) and the flight data recorder (FDR). The FDR logs critical technical parameters including altitude, speed, engine thrust, and flight path data. The CVR captures all cockpit audio - pilot conversations, radio transmissions, warning alarms, and ambient mechanical sounds.

There have been cases where planes have crashed into water bodies. To make black boxes discoverable in situations where they are underwater, they are equipped with a beacon that sends out ultrasound signals for 30 days.

What is inside the black box?

A black box consists of four main parts, including an interface to facilitate recording and playback, underwater locator beacon, "crash survivable memory unit" to withstand a force equivalent to 3,400 times the force of gravity and the recording chip on a circuit board.

Why is it called black box?

According to the Airbus website, before Warren, French engineer François Hussenot began working on a data recorder in the 1930s. This equipment had sensors that would optically project around 10 parameters onto a photographic film.

This film ran continuously in a box that was constructed to prevent any light from entering it. Hence, it was called a “black box”.

Why is black box crucial in an air crash?

It provides investigators with a second-by-second reconstruction of events leading to a crash. As a result, investors can get an idea of what transpired in the cockpit and across aircraft systems. It serves as the aviation equivalent of DNA evidence in criminal cases - providing definitive, unbiased testimony when human witnesses may be unavailable.

Key incidents when black box helped

Black box data has helped in solving major aviation disasters globally, from the 2015 Germanwings crash to Malaysia Airlines incidents. In India, the 2020 Kozhikode crash investigation relied heavily on these recordings to establish pilot decisions and runway conditions.

What happens once the black box is found?

The devices will be sent to a forensic lab under the Directorate General of Civil Aviation (DGCA) or the Aircraft Accident Investigation Bureau (AAIB). The experts will extract and decode memory modules, synchronise voice and flight data and correlate findings with radar logs and air traffic control records.

The process can take anywhere from several days to a few weeks.

Captain MR Wadia told CNBC-TV18 that the cockpit voice recorder can be accessed immediately, and will reveal conversations leading up to the incident. The FDR details, however, can take weeks as the digital data needs to be fed into a simulator.