Take off and crash in 174 seconds: Investigators piece together Air India Dreamliner's last moments

The Aircraft Accident Investigation Bureau (AAIB) preliminary investigation has revealed that the ill-fated Boeing Dreamliner of Air India that crashed on June 12, killing 241 out of the 242 passengers on board, went down less than three minutes -- 174 seconds to be precise -- since taking position for take-off on the runway at the Ahmedabad airport.

The preliminary findings released by the AIIB piece together a timeline leading up to the crash of Air India Flight 171:

* 05:47 UTC (11:17 IST): Air India's B787-8 aircraft, VT-ANB, arrived at Ahmedabad airport operating flight AI423 from Delhi and was parked at Bay 34.

* Prior to 06:40 UTC (11:55 IST): The crew of flight AI423 made a Pilot Defect Report (PDR) entry for a "STAB POS XDCR" status message in the Tech Log. Troubleshooting was carried out per the Fault Isolation Manual (FIM) by an Air India AME.

* 06:25 UTC (12:10 IST): The crew of flight AI171 arrived at the airport and underwent a pre-flight Breath Analyzer test, being found fit to operate the flight.

* 06:40 UTC (12:10 IST): The aircraft was released for flight after troubleshooting.

* 07:05 UTC (12:35 IST): The crew was observed arriving at the boarding gate in CCTV recordings.

* 07:43:00 UTC (13:35 IST): The aircraft requested pushback and startup.

* 07:43:13 UTC (13:35:13 IST): Air Traffic Control (ATC) approved the pushback.

* 07:46:59 UTC (13:17:59 IST): ATC approved the startup.

* 07:48:38 UTC (13:18:38 IST): The aircraft was observed departing from Bay 34 as per A-SMGCS replay.

* 07:49:12 UTC (13:19:12 IST): ATC queried if the aircraft required the full length of the runway; the aircraft confirmed the requirement for the full length of Runway 23.

* 07:55:15 UTC (13:25:15 IST): The aircraft requested taxi clearance, which was granted by ATC.

* 07:56:08 UTC (13:26:08 IST): The aircraft taxied from the bay.

* 08:02:03 UTC (13:32:03 IST): The aircraft was transferred from Ground Control to Tower Control.

* 08:03:45 UTC (13:33:45 IST): The aircraft was instructed to line up on Runway 23.

* 08:07:33 UTC (13:37:33 IST): The aircraft was cleared for Take-Off from Runway 23, with wind at 240°/06 Knots.

* 08:07:37 UTC (13:37:37 IST): The aircraft started rolling.

* 08:08:33 UTC (13:38:33 IST): The aircraft crossed the take-off decision speed V1 and achieved 153 knots Indicated Airspeed (IAS).

* 08:08:35 UTC (13:38:35 IST): The aircraft achieved the Vr speed (155 kts).

* 08:08:39 UTC (13:38:39 IST): The aircraft's air/ground sensors transitioned to air mode, consistent with liftoff.

* 08:08:42 UTC (13:38:42 IST): The aircraft achieved the maximum recorded airspeed of 180 Knots IAS. Immediately thereafter, Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position, one after another, with a 1-second time gap. In the cockpit voice recording, one pilot asked the other why they cut off, and the other pilot denied doing so.

Shortly after lift-off: The Ram Air Turbine (RAT) was observed deploying during the initial climb. The aircraft began losing altitude before crossing the airport perimeter wall.

* 08:08:47 UTC (13:38:47 IST): Both engines' N2 values passed below minimum idle speed, and the RAT hydraulic pump began supplying hydraulic power.

* 08:08:52 UTC (13:38:52 IST): Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN.

* 08:08:54 UTC (13:38:54 IST): The Auxiliary Power Unit (APU) Inlet Door began opening, consistent with APU Auto Start logic.

* 08:08:56 UTC (13:38:56 IST): Engine 2 fuel cutoff switch transitioned from CUTOFF to RUN. Engine Gas Temperature (EGT) was observed rising for both engines, indicating relight. Engine 1's core deceleration stopped, reversed, and started to recover. Engine 2 relit but could not arrest core speed deceleration and repeatedly re-introduced fuel to increase core speed acceleration and recovery.

* 08:09:05 UTC (13:39:05 IST): One of the pilots transmitted “MAYDAY MAYDAY MAYDAY”. The ATC inquired about the call sign but received no response, instead observing the aircraft crashing outside the airport boundary and activating the emergency response.

* 08:09:11 UTC (13:39:11 IST): The Enhanced Airborne Flight Recorder (EAFR) recording stopped.

* 08:14:44 UTC (13:44:44 IST): Crash Fire Tender left the airport premises for Rescue and firefighting, joined by Fire and Rescue services of local administration