The Aircraft Accident Investigation Bureau (AAIB) on wee hours of Saturday released a 15-page preliminary report on the Air India plane that crashed a month ago in Ahmedabad, killing at least 270 people.
As per the report, both engines of the ill-fated flight AI171, a Boeing Dreamliner, 'cut off' seconds after take-off from Ahmedabad, and neither pilot acknowledged triggering the shutdown.
Flight AI171 had arrived in Ahmedabad earlier that day as AI423 from Delhi. The previous crew had logged a defect report related to a stabilizer sensor (“STAB POS XDCR”). Air India’s on-duty maintenance engineer conducted troubleshooting, and the aircraft was cleared for flight.
The AAIB report confirms that the twin-engine failure occurred at 1.38 PM IST, less than a minute after the aircraft became airborne from Runway 23. The Boeing 787-8 aircraft, bound for London Gatwick with 230 people onboard, crashed just outside the airport perimeter on June 12.
"The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off," the report read.
Also read: Air India crash report- Probe tracks engine switch movement; no immediate action for Boeing or GE
According to the findings so far, the Cockpit Voice Recorder (CVR) captured one pilot asking, “Why did you cutoff?” to which the other responded, “I didn’t do so.” Seconds later, the Ram Air Turbine (RAT), a backup power device, deployed automatically, indicating total loss of engine thrust, as per the CCTV footage examined.
"The aircraft started to lose altitude before crossing the airport perimeter wall," the report further stated.
The CCTV footage confirmed RAT deployment during initial climb. No significant bird activity was recorded in the vicinity of the flight path.
According to the flight data, by 08:08:47 UTC, the N2 values of both engines had dropped below the minimum idle speed, prompting the RAT hydraulic pump to begin supplying power. At 08:08:52 UTC, the fuel cutoff switch for Engine 1 was moved back to RUN. The APU Inlet Door opened at 08:08:54 UTC, consistent with automatic start logic. Two seconds later, the Engine 2 switch also returned to RUN.
When these switches are moved back to RUN in-flight, the aircraft's engine control system (FADEC) initiates a relight process by reintroducing fuel and ignition. The Exhaust Gas Temperature (EGT) readings began rising, indicating relight attempts.
Engine 1's core speed loss reversed and began recovery. Engine 2, though it managed to relight, could not stop its core speed from falling and kept reintroducing fuel to accelerate. At 08:09:05 UTC, one of the pilots made a “MAYDAY MAYDAY MAYDAY” call. The Air Traffic Controller asked for the aircraft’s call sign but received no response.
The aircraft crashed outside the airport boundary. The final recording from the flight data system stopped at 08:09:11 UTC.
As per the report, both engines of the ill-fated flight AI171, a Boeing Dreamliner, 'cut off' seconds after take-off from Ahmedabad, and neither pilot acknowledged triggering the shutdown.
Flight AI171 had arrived in Ahmedabad earlier that day as AI423 from Delhi. The previous crew had logged a defect report related to a stabilizer sensor (“STAB POS XDCR”). Air India’s on-duty maintenance engineer conducted troubleshooting, and the aircraft was cleared for flight.
The AAIB report confirms that the twin-engine failure occurred at 1.38 PM IST, less than a minute after the aircraft became airborne from Runway 23. The Boeing 787-8 aircraft, bound for London Gatwick with 230 people onboard, crashed just outside the airport perimeter on June 12.
"The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off," the report read.
Also read: Air India crash report- Probe tracks engine switch movement; no immediate action for Boeing or GE
According to the findings so far, the Cockpit Voice Recorder (CVR) captured one pilot asking, “Why did you cutoff?” to which the other responded, “I didn’t do so.” Seconds later, the Ram Air Turbine (RAT), a backup power device, deployed automatically, indicating total loss of engine thrust, as per the CCTV footage examined.
"The aircraft started to lose altitude before crossing the airport perimeter wall," the report further stated.
The CCTV footage confirmed RAT deployment during initial climb. No significant bird activity was recorded in the vicinity of the flight path.
According to the flight data, by 08:08:47 UTC, the N2 values of both engines had dropped below the minimum idle speed, prompting the RAT hydraulic pump to begin supplying power. At 08:08:52 UTC, the fuel cutoff switch for Engine 1 was moved back to RUN. The APU Inlet Door opened at 08:08:54 UTC, consistent with automatic start logic. Two seconds later, the Engine 2 switch also returned to RUN.
When these switches are moved back to RUN in-flight, the aircraft's engine control system (FADEC) initiates a relight process by reintroducing fuel and ignition. The Exhaust Gas Temperature (EGT) readings began rising, indicating relight attempts.
Engine 1's core speed loss reversed and began recovery. Engine 2, though it managed to relight, could not stop its core speed from falling and kept reintroducing fuel to accelerate. At 08:09:05 UTC, one of the pilots made a “MAYDAY MAYDAY MAYDAY” call. The Air Traffic Controller asked for the aircraft’s call sign but received no response.
The aircraft crashed outside the airport boundary. The final recording from the flight data system stopped at 08:09:11 UTC.
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