Explained: What Is A Black Box In A Plane, And How It Reveals Crash Details

New Delhi:

An Air India Ahmedabad-London flight took off at 1.39 pm. Under a minute later, it plummeted from an altitude of 625 feet and crashed into a doctors’ hostel, with several casualties feared both inside the aircraft and in the building it damaged. The plane erupted into flames, sending thick smoke into the sky. As firefighting and rescue teams work on the spot of the crash, a deeper look into the reason behind it will likely be clear from a small box sitting in a corner of the aircraft – the black box.

Origins Of The Black Box

In 1953, Australian scientist David Warren came up with the idea for the cockpit voice recorder, according to the Associated Press. 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. Warren’s father had been killed in a plane crash in Australia in 1934.

What Does A Black Box Do?

The black box comprises two devices – the cockpit voice recorder (CVR) and the flight data recorder (FDR).

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 (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 are also listening 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.

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.

NTBS investigators told the AP in 2014 that a flight data recorder carries 25 hours of information, including prior flights within that time span, which can sometimes provide hints about the cause of a mechanical failure on a later flight. An initial assessment of the data is provided to investigators within 24 hours, but analysis will continue for weeks more.

It Does Not Appear Black

Contrary to its name, a black box is typically orange in colour. This is to allow them to be easily discovered in plane wreckage, which are sometime found in depths of the ocean.

The term “black box” was likely borrowed from the field of computing, in which a system has an input and output with an internal mechanism that is often not widely understood by a layperson, an expert told LiveScience.

How Does It Survive Crashes?

An FDR is usually placed in the tail of an aircraft, considered to be a part that is likely to take the least damage in a crash. When a plane crashes into water, the beacons inside activate and can transmit signals from the depths of 14,000 feet. If recovered from the sea, the black box is first treated to remove corrosive salt and then the inside is dried for up to many days. After electronics and memory are checked, necessary repairs are made, the chips are scrutinised to retrieve flight data.

The black boxes are designed to withstand high impact, fire and deep sea pressure, being made from robust materials like titanium or stainless steel.

A CVR is placed inside the aircraft’s cockpit.

What About Helicopters?

Helicopters are equipped with a (single) combined recorder, capable of recording all the data needed to characterise the flight (time, heading, altitude, power, temperature, rotor speed, outside temperature, etc.), tracking between 800 and 1,200 parameters, per AirBus. On heavy helicopters (over 3,175 kg maximum take off weight) they can withstand a temperature of 1100 degrees Celsius for one hour. Those on light helicopters must withstand this temperature for 15 minutes.

Where Will Data Of Crashed Air India Plane Be Retrieved?

Earlier this year, Digital Flight Data Recorder and Cockpit Voice Recorder (DFDR & CVR) Laboratory was inaugurated in Delhi, where retrieved flight data from aircraft can be analysed. The state-of-the-art facility will enable Aircraft Accident Investigation Bureau (AAIB) to repair damaged black boxes, retrieve data, and conduct thorough analyses of accidents and incidents.

Black Boxes Not 100% Reliable

Though largely reliable in finding the root cause behind aviation accidents, black boxes have also known to present its limitations. A Jeju Air plane flying from Bangkok to South Korea with 181 people on board crashed on landing Sunday, killing 179 people on board. It black box was recovered, but analysis by the NTSB found that crucial data from the last few minutes of the flight was wiped out.

In the case of the notorious downing and disappearance of the Malaysia Airlines Flight 370 in March 2014, the signals that would emanate from the black box were not detected during search operations.

With inputs from agencies