A preliminary investigation into the tragic Air India Flight AI171 crash in Ahmedabad has revealed that a critical safety warning issued by US aviation authorities in 2018 may have gone unheeded, potentially contributing to the disaster. The crash, which occurred moments after takeoff on June 12 and claimed 260 lives, involved a Boeing 787-8 Dreamliner en route to London Gatwick.

The Aircraft Accident Investigation Bureau (AAIB) released a 15-page preliminary report late Saturday. The report pointed to a finding that in 2018, Special Airworthiness Information Bulletin (SAIB) from the US Federal Aviation Administration (FAA) had flagged a potential fault in the fuel control switch locking mechanism. According to the advisory, the issue, if unaddressed, could lead to inadvertent movement of the switch and an unintentional in-flight engine shutdown; a scenario consistent with what investigators suspect may have happened in this crash.

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The FAA bulletin (SAIB No. NM-18-33), issued in December 2018, warned owners and operators of several Boeing aircraft models, including the 787-8, about the “potential for disengagement of the fuel control switch locking feature”. The report explained that if the locking mechanism disengages, the switch can move between the fuel supply and cutoff positions without the pilot lifting it, as otherwise required. This could expose the switch to accidental operation during flight.

‘SAIB was advisory and not mandatory,’ Air India said

The AAIB report further revealed that suggested inspections by the FAA’s SAIB were not carried out. “The airworthiness concern was not considered an unsafe condition that would warrant an airworthiness directive by the FAA. The fuel control switch design, including the locking feature, is similar on various Boeing airplane models including part number 4TL837-3D which is fitted in B787-8 aircraft VT-ANB,” AAIB said in its report.

The report added, “As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory. The scrutiny of maintenance records revealed that the throttle control module was replaced on VT-ANB in 2019 and 2023. However, the reason for the replacement was not linked to the fuel control switch. There has been no defect reported pertaining to the fuel control switch since 2023 on VT-ANB.”

Understanding the fuel control switch

The fuel control switch locking feature is designed to serve as a safeguard against unintended operation of an aircraft’s engine fuel system. In Boeing aircraft such as the 787-8, this mechanism is intended to ensure that pilots must lift the switch while changing its position, an action that significantly reduces the risk of accidental shutdown.

No final conclusions

The AAIB report said that no final conclusions have been drawn and detailed inspections of wreckage, engine components and post-mortem data are still ongoing. “At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers,” the report stated.

Air India confirmed it is fully cooperating with the investigation. Boeing also commented, “We will defer to the AAIB to provide information about AI171, in adherence with the United Nations International Civil Aviation Organization protocol known as Annex 13.”