Engine Fuel Supply Cut Off, No Action on Manufacturers: Air India Crash Probe

While the probe is still underway, the report recommends "no action against engine manufacturers and operators yet."

A month after the ill-fated London-bound Air India flight AI-171 crashed after taking off from the Ahmedabad airport, the Aircraft Accident Investigation Bureau (AAIB) released a 15-page report on the preliminary investigation, indicating malfunction of the fuel control switch of the engines as the key reason.

Though the investigation is still underway and the reasons behind the supposed malfunction are being probed, the report details data and sequence of events from two Enhanced Airborne Flight Recorders (EAFR) of the aircraft.

The crash on 12 June claimed the lives of 229 passengers of the aircraft and 16 others .

Here's what report says on the series of events ahead of the accident: (The timeline described is Coordinated Universal Time (UTC), the primary time standard globally used to regulate clocks and time.)

Questions Around the Fuel Control Switch Malfunction

According to the report, the US' aviation regulator Federal Aviation Administration (FAA) in December 2018 had issued a safety bulletin about a potential issue with the fuel control switch on Boeing 737 aircrafts. Some airlines had reported that the switch’s locking mechanism, which helps prevent accidental changes, would disengage.

However, the FAA said this issue did not pose a serious safety risk, so it didn’t require a formal, mandatory fix which in aviation terms is known as an 'Airworthiness Directive'.

The same type of switch is used on other Boeing planes, including the Boeing 787-8, which was the ill-fated AI-171 flight that crashed on 12 June.

The AAIB in its report said that since this was just an advisory and not mandatory, Air India did not carry out the recommended inspections. Maintenance records show that the throttle control module on VT-ANB was replaced in both 2019 and 2023, but not because of this fuel switch issue.

Moreover, no problems with the fuel control switch were reported on this aircraft since 2023.

The Events Recorded Ahead of the Crash

• 07:43:00 UTC: The crew contacted Air Traffic Control (ATC) and requested clearance for pushback and engine startup. ATC promptly acknowledged and approved.

• 07:46:59 UTC: The ATC granted clearance for engine startup. At this point, all systems on the aircraft were reportedly functional, with no new fault messages.

• 07:55:15 UTC: The crew received taxi clearance after informing the ATC that they will require full length of the runway to take off. The aircraft was guided to the threshold of Runway 23.

• 08:07:33 UTC: The aircraft was officially cleared for takeoff from Runway 23.

• 08:08:42 UTC: Within a minute of taking off, both Engine 1 and Engine 2 fuel control switches were observed to transition from RUN to CUTOFF, one after the other, with a one-second gap, cutting off fuel supply mid-air. In the cockpit voice recording, one of the pilots is heard asking the other why he cutoff. The other pilot responded that he did not do so.

• 08:08:56 UTC: The crew managed to turn the fuel switch for Engine 1 back to RUN, initiating an automatic relight sequence governed by FADEC (Full Authority Digital Engine Control).

• 08:09:05 UTC: A MAYDAY call was transmitted from the aircraft thrice. The ATC controller responded by requesting the flight’s call sign. However, there was no reply.

• 08:09:11 UTC: The flight data recording from the Enhanced Airborne Flight Recorder (EAFR) ceased abruptly, signifying either total power loss or physical destruction due to impact.

Key Aircraft Parts and Equipment Recovered From the Crash

The Investigation So Far

• The wreckage site activities including Drone photography/videography have been completed, and the wreckage has been moved to a secure area near the airport.

• Both Engines were retrieved from the wreckage site and quarantined at a hangar in the airport.

• Components of interest for further examinations have been identified and quarantined.

• Fuel samples taken from the bowsers and tanks used to refuel the aircraft were tested at the DGCA’s Lab and found satisfactory.

• Very limited amount of fuel samples could be retrieved from the APU filter and

• The EAFR data downloaded from forward EAFR is being analysed in detail.

• The statement of the witnesses and the surviving passenger have been obtained bythe investigators.

• Complete analysis of postmortem reports of the crew and the passengers is being undertaken to corroborate aeromedical findings with the engineering appreciation.

• At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers.

• Investigation is continuing and the investigation team will review and examine additional evidence, records and information that is being sought from the stake