Air India crash: What happened in the lead-up to the disaster

Key Concepts:

• Boeing 787 Dreamliner crash
• Preliminary accident report
• Cockpit voice recorder (CVR)
• Flight data recorder (FDR)
• Engine fuel cutoff switches (run/cutoff)
• Toggle switch mechanism
• Loss of thrust
• Mayday call

Accident Overview:

The preliminary report on the Air India Boeing 787 Dreamliner crash in Ahmedabad, 30 days after the incident, details the events leading to the accident based on the aircraft's voice and data recorders. The report emphasizes an atmosphere of confusion in the cockpit during the critical moments.

Timeline of Events:

1. 7:55 AM: Aircraft requests and receives taxi clearance from air traffic control.
2. 8:07 AM: Aircraft begins takeoff roll, thrust levers set to takeoff thrust.
3. 8:08:39 AM: Aircraft lifts off.
4. Shortly After Takeoff (180 knots/330 km/h): Engine 1 and Engine 2 fuel cutoff switches transition from "run" to "cutoff" within approximately one second of each other.

Fuel Cutoff Switch Mechanism:

• The fuel cutoff switches control the fuel supply to the engines.
• They feature a locking mechanism to prevent accidental movement.
• Operation: To change the switch position, it must be pulled outward, moved to the desired position (run or cutoff), and then released to lock into place.
• The report highlights that moving these switches requires a deliberate action.

Cockpit Voice Recording Analysis:

• After the fuel cutoff, one pilot is heard asking the other, "Why did he cut off?"
• The other pilot responds that he did not do so.
• The report does not identify which pilot made each statement.

Engine Relight Attempt:

• The fuel control switches were moved back to the "run" position, initiating the engine relight process.
• At the time of the accident, one engine was in the process of regaining thrust.
• The other engine was re-ignited but had not yet started regaining thrust.

Final Moments:

• During the 10 seconds following the fuel cutoff, the pilots issued a Mayday call.
• The data recording stopped 6 seconds after the Mayday call.

Key Arguments/Perspectives:

• The report does not draw conclusions but presents factual data from the recorders.
• The pilot's denial of intentionally cutting off the fuel raises questions about the cause of the switch movement.

Synthesis/Conclusion:

The preliminary report paints a picture of a sudden and unexpected event – the simultaneous cutoff of fuel to both engines – leading to a rapid loss of altitude. The confusion in the cockpit, as evidenced by the voice recording, and the denial of intentional action by either pilot, suggest a potential malfunction, inadvertent action, or other unexplained factor that requires further investigation. The report serves as a factual basis for further analysis to determine the root cause of the accident.