Wreckage of Air India's Boeing 787-8 aircraft, which was operating flight AI 171 from Ahmedabad to London, placed under tight security
Credit: PTI Photo
New Delhi: The preliminary report of the Aircraft Accident Investigation Bureau on the June 12 Ahmedabad air crash has said that the fuel supply to both the engines of the Air India's Boeing 787-8 'Dreamliner' stopped just 3 seconds after the lift-off as fuel cut-off switches transitioned from RUN to CUTOFF position, one after the other, within a gap of one second.
Here is a minute-by-minute account of the events that unfolded in the ill-fated flight based on the 15-page report released early on Saturday.
Minute-by-minute
11:17 AM: VT-ANB, which will fly to Gatwick, lands in Ahmedabad from Delhi; Lodges Pilot Defect Report 'STAB POS XDCR' (relates to Stabiliser Position Transducer, a sensor that communicates the horizontal stabiliser’s trim position to the aircraft’s flight control systems)
11:55 AM: Crew for Gatwick flight arrives at airport
12:10 PM: Troubleshooting carried out, aircraft released for flight
12:35 PM: Crew arrives at boarding gate
1:13 PM: Pilots request pushback and start-up; ATC approves pushback
1:18 PM: Aircraft departs bay
1:17 PM: ATC approved start-up
1:19 PM: To ATC query, pilots conform requirement of full length of Runway-23
1:25 PM: ATC grants taxi clearance on pilots’ request
1:32 PM: Aircraft transferred from Ground to Tower Control
1:33 PM: Aircraft instructed to line up on the Runway 23
1:37 PM: Aircraft cleared for Take-Off from Runway 23, Wind 240°/06 Kts
1:38 PM: Aircraft achieves maximum recorded airspeed of 180 Knots; Fuel cutoff switches of Engine 1 and Engine 2 transitioned from Run to Cutoff one after another with a time gap of one second
1:39 PM: 'Mayday' call from one of the Pilots; ATC enquires about call sign but no response; ATC observes aircraft crashing outside airport boundary, activates emergency response
1:44 PM: Crash fire tender leaves airport premises
Aircraft
Year of Manufacture: 2013
Total Aircraft Hours: 41,868
Applicable airworthiness directives and alert service bulletins complied
On Board
54,200 kg fuel on board
2,13,401 kg take-off weight (Maximum allowed: 2,18,183 kg)
No 'Dangerous Goods' on aircraft
From Cockpit Voice Recording
One of the pilots asks the other why he cut off (fuel cutoff switch). The other pilot says he did not do so
From CCTV footage
Ram Air Turbine (RAT) getting deployed during the initial climb immediately after lift-off. No significant bird activity observed in the vicinity of the flight path. Aircraft started to lose altitude before crossing the airport perimeter wall
Black Boxes
Recovered on June 13 and 16
Brought to Delhi on June 24
Data downloaded after sourcing ‘Golden Chassis’ (Identical EAFR unit) and download cables from National Transportation Safety Board of the US
49 hours of flight data and 6 flights, including the event flight, recovered; Audio is two hours in length and captures the crash
Initial analysis of the audio and flight data over
Black box on the tail section of aircraft substantially damaged and could not be downloaded through conventional means; opened to inspect the memory card, damage is extensive
Fuel Control Switch
FAA issued Special Airworthiness Information Bulletin (SAIB) in Dec 2018
Regarding potential disengagement of the fuel control switch locking feature
Airworthiness concern was not considered an unsafe condition that would warrant airworthiness directive by the FAA
Air India says suggested inspections not carried out as the SAIB was advisory and not mandatory
Scrutiny of maintenance records showed throttle control module was replaced in 2019 and 2023
Reason for replacement not linked to the fuel control switch
No defect reported pertaining to the fuel control switch since 2023
Investigation at this Juncture
Wreckage site activities, including drone photography/videography completed; wreckage moved to a secure area
Both engines retrieved and quarantined at a hangar in the airport
Fuel samples taken from the bowsers and tanks used to refuel the aircraft tested; found satisfactory
Very limited amount of fuel samples could be retrieved from the APU filter and Refuel/Jettison valve of left wing; Testing to be done at a suitable facility
Cockpit data downloaded from the black box being analysed
Statement of witnesses and the surviving passenger obtained
Complete analysis of postmortem reports being undertaken to corroborate aeromedical findings with engineering appreciation
Additional details being gathered based on the initial leads
No recommended actions on Boeing or General Electricals, the manufacturer of engine
Investigators to review and examine additional evidence, records and information