274 people, including 33 on the ground, were killed in the Air India plane crash, but, miraculously, one passenger, in seat 11A, survived.

What Pilots Said, What Alarms Rang: Questions For Crashed Air India Plane’s ‘Black Box’

274 people, including 33 on the ground, were killed in the Air India plane crash, but, miraculously, one passenger, in seat 11A, survived.

All planes carry flight and voice data recorders to help in case of crash investigations.

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The ‘black box’ of the London Gatwick-bound Air India AI-171 plane that crashed in Ahmedabad last week – losing thrust 36 seconds after take-off and slamming into residential buildings bordering the airport, killing all 274 people, including 33 on the ground – have been recovered.

The term ‘black box’ refers to a set of two devices that records conversations between the pilots and with Air Traffic Control, as well as flight data parameters like altitude, heading, and airspeed.

All of this information is required by investigators to establish how and why a plane crashed is stored in the Cockpit Voice Recorder, or CVR, and Flight Data Recorder, or FDR.

And now that authorities investigating the Air India crash have both devices, we can unravel the final minutes, nay seconds, of AI-171 and understand why the Boeing 787-8 Dreamliner crashed.

There are some of the key questions CVR data should be able to answer.

1. What, exactly, did Captain Sumeet Sabharwal say in his distress call?

Last week the Civil Aviation Ministry said a distress call had been broadcast seconds before impact. ‘Mayday, mayday…’ was what Captain Sabharwal reportedly told Ahmedabad ATC.

There are, however, reports that Captain Sabharwal also flagged the loss of power and thrust.

CVR data should reveal if he did, indeed, also say ‘… no power… no thrust…’, which will be a key piece of evidence pushing investigators to focus on the engine as the cause for the crash.

A Cockpit Voice Recorder, or CVR. Photo: SKYbrary.aero

At this time multiple theories – some ludicrous and many without adequate proof to support the claim – about what caused the plane crash are doing the rounds, including a system-wide electrical failure, possible maintenance issues, and a simultaneous bird strike in both engines.

There are questions also being asked about the landing gear and the plane’s flaps.

2. What time was the distress message sent?

The plane took off at 1.39 pm, the government has confirmed.

Thirty-six seconds later it crashed.

What happened in that painfully brief period?

CVR data will pinpoint the exact millisecond Captain Sabharwal sent his ‘mayday’ message, which will establish just how much time First Officer Clive Kunder and he had to try and rescue the plane and the 240 other people on board, including 10 crew members.

A Flight Data Recorder, or FDR. Photo: National Transportation Safety Board

Knowing when the ‘mayday’ call was sent will also allow investigators to work out when the problem (that caused the crash) manifested, i.e., was it present before take-off and did the pilots not notice it or did it happen after lift-off, perhaps prompted by a system failure?

3. What did the pilots and ATC talk about?

Again, the CVR will also tell investigators exactly what Captain Sabharwal and First Officer Kunder said to each other and the ATC.

Of course, the ATC personnel will have already been debriefed, but they may not remember everything that was said or even the tone in which it was said, which can provide clues.

And they will not know what the pilot and first officer said to each other in the plane. The CVR records all of this, as well as ambient noise from the cockpit, including that of the engine.

‘Black boxes’ are storied in the tail section of a plane.

Crucially, ambient noise will include alarms that may have blared in the cockpit in the seconds before the crash, vibration feedback from the controllers, etc.

It will also let them know how the pilots responded to these alerts.

Meanwhile, parallel to the CVR data, investigators will also have access to key flight parameters that will allow them to re-create, in real-time the flight path of the doomed Air India plane.

Together, these should be able to tell us how and why this disaster happened, and how, perhaps, to ensure that such aviation tragedies are not repeated.