Air India black box damaged: Is this a setback to the probe? What happens now?

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The black box of the crashed Air India AI-171 flight has sustained damage as the plane hit a residential area in Ahmedabad, moments after take-off, last week. Reports say the recorder is likely to be sent to the US for analysing data. What information does the black box hold? read more
India is likely to send the black box recovered from the crashed Air India AI-171 flight to the United States for data extraction. The recorder has reportedly sustained damage after the London-bound Boeing 787-8 Dreamliner came down on a residential area in Ahmedabad, moments after take-off, last week.
A video of the crash showed the Air India flight struggling to stay airborne before rapidly descending and disappearing behind trees and buildings. This was followed by an explosion in the sky. The plane had crashed into a doctors' accommodation building at the BJ Medical College and Civil Hospital, killing 241 of 242 people on board and 33 on the ground.
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But what is a black box and why is it necessary in the Air India crash investigation? We will explain.
What are black boxes?
The cockpit voice recorder (CVR) and the flight data recorder (FDR) make up the black boxes on an aircraft.
Also known as accident data recorders, flight data recorders store information on several parameters, including altitude, flight speed, flight control, engine performance, fuel, turbulence, wind speed, roll, and autopilot status.
A cockpit voice recorder records radio transmissions and other audio in the cockpit, such as conversations between pilots, engine sounds, background noises, landing gear extension and retraction, and instrumentation warnings.
The black boxes are usually bright orange in colour, so they can be easily found in the debris of the plane.
The flight data recorder from TWA flight 800 is displayed at NTSB headquarters July 25, 1996. File Photo/Reuters
How important are black boxes?
All commercial flights must have black boxes. The two recorders help investigators piece together events leading to an aircraft mishap.
CVRs pick up audio from the crew's microphones, pilots' headsets, and near the centre of the cockpit. They can record two hours of audio data, while 25 hours of flight data remain available on FDRs.
Black boxes are highly protective equipment, weighing about 4.5 kg, that record information about a flight and help to find out what led to its crash.
'With the data retrieved from the FDR, the Safety Board can generate a computer animated video reconstruction of the flight. The investigator can then visualise the airplane's attitude, instrument readings, power settings and other characteristics of the flight. This animation enables the investigating team to visualise the last moments of the flight before the accident,' US National Transportation Safety Board (NTSB) said on its website.
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'Both the Flight Data Recorder and the Cockpit Voice Recorder have proven to be valuable tools in the accident investigation process. They can provide information that may be difficult or impossible to obtain by other means. When used in conjunction with other information gained in the investigation, the recorders are playing an ever increasing role in determining the probable cause of an aircraft accident,' it added.
Can black boxes be destroyed during plane crash?
Black boxes are usually installed at the tail end of the aircraft, as it increases their chances of survival during a mishap.
The FDR and CVR are kept in one box made of titanium or stainless steel and wrapped with fire and heat-resistant insulation. The black box is designed to withstand an acceleration of 3,400 Gs (3,400 times the force of gravity) and a temperature of up to 1093 degrees Celsius for an hour.
FDRs can survive depths of over 6,000 metres underwater. When submerged in water, the beacon present in these devices can transmit ultrasound signals for 30 days. This underwater locator beacon (ULB), which has a battery life of over six years, transmits sound as deep as 14,000 feet and can be tracked by sonar and audio equipment.
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These beacons will not send out ultrasonic pings if the plane crashed on land; thus, the investigators will have to scour the accident site for the black box.
Data from the black boxes is stored on 'stacked memory boards inside the crash-survivable memory unit (CSMU)', as per How Stuff Works. These CSMUs can hold out against extreme heat, crashes and tonnes of pressure.
'It is extremely rare for a black box to be destroyed. Black boxes have traditionally outperformed their design,' Scott Hamilton, director of Leeham Co., an aviation consulting company, told NPR.
'It would take a concentrated fire beyond its design strength, or an impact so high that it would be beyond what it could withstand.'
However, black boxes have not always helped investigators. It came to light in January that the flight data and cockpit voice recorders on the Jeju Air plane stopped recording nearly four minutes before the airliner hit a concrete structure at the end of a runway at South Korea's Muan International Airport on December 29 last year. The disaster, the worst in South Korea, had killed 179 people.
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Questions have arisen about the eight black boxes on the four hijacked flights that crashed during the 9/11 terrorist attacks on the US. As per a 2001 ABC News report, flight data recorders were recovered from Flight 93, which crashed in Pennsylvania. The voice transcript extracted from them is available online, Forbes reported.
As per ABC News, the black boxes were also recovered from the collapsed portion of the Pentagon building, where a jet slammed into during the terrorist attacks.
Will India send black boxes to the US?
India could send the black box of the crashed Air India flight to the US for analysis. The recorder has sustained damage due to the fire as the plane crashed in Ahmedabad, making it difficult to extract the data in India, Economic Times (ET) reported, citing sources.
As per Ministry of Civil Aviation sources, the Centre will take a final call on whether to send the black box to the US or not. The black box may be sent to the National Transportation Safety Board laboratory in Washington, DC for examination.
In the event it is sent to the US, a contingent of Indian officials will also go with the black box.
Sources previously told Indian Express that digital flight data recorder (DFDR) and CVR will be analysed in India or sent abroad, depending on their physical condition and the extent of data analysis needed for the investigation.
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'While AAIB had established a laboratory at its headquarters in Delhi last year, it is yet to be properly equipped to extract data from recorders which have sustained heavy damage. The NTSB team will carry them to their lab under protection and supervision from Indian officials to ensure that proper protocols are followed,' a person in the know told ET.
The source said it could take two days to months to extract data from the black box, depending on the damage.
'Since the recorder has been damaged, the chip will need to be extracted by removing the memory board so that there is no further damage to data. The electronic circuit will also have to be assessed for damage,' the person said.
With inputs from agencies