New Delhi: Indian operators of certain Boeing aircraft must inspect the locking mechanism of their fuel control switches, the Directorate General of Civil Aviation (DGCA) said on Monday (July 14), two days after it came to light that last month's Ahmedabad plane crash occurred after these switches on the ill-fated aircraft had turned off.

The DGCA did not mention the preliminary findings of the Aircraft Accident Investigation Bureau (AAIB) released on Saturday, but issued its order in light of “several” operators at home and abroad deciding to conduct checks on the Boeing aircrafts' fuel control switch locking mechanisms in line with a 2018 US advisory that found mention in the AAIB's report.

Fuel control switches are used to provide or cut off fuel to a plane's engines.

In its preliminary report, the AAIB said that the twin switches aboard Air India flight 171 – a Boeing 787-8 Dreamliner – had turned off moments after the London-bound flight took off from the Ahmedabad airport on June 12, cutting off power to its engines. The aircraft crashed into a densely settled neighbourhood and exploded shortly thereafter, killing some 260 people, including 241 of the 242 people on board.

The flight's twin switches had moved from the ‘run’ to the ‘cutoff’ position within a second of each other, the AAIB said.

They then moved back to the ‘run’ position but it was too late as the aircraft, having barely hit the skies, could not regain enough thrust to avoid a crash.

The plane's black box recorded audio of one of the pilots – the AAIB report does not identify whom – asking why his co-pilot cut off fuel supply to the engines, to which the latter said he did not do so.

Its report also recalled that the US's Federal Aviation Administration (FAA) had in a December 2018 advisory said that operators of Boeing 737 aircraft observed that their fuel control switches were installed “with the locking feature disengaged”.

This feature requires pilots to lift the switch before being able to change its position between ‘run’ and ‘cutoff’ in an effort to prevent it from being moved inadvertently.

But if the locking feature is disengaged the switches may be vulnerable to being moved by mistake. “Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown,” the regulator had noted.

In light of this the FAA recommended that operators of a number of Boeing aircraft models, including 737s and 787s, inspect the locking mechanisms of their fuel control switches and replace them at the earliest if they were found to be disengaged. It also said this “airworthiness concern is not an unsafe condition” that would warrant a binding directive.

However, Air India did not conduct this inspection because it was not binding, the AAIB said.

On Monday, the DGCA asked operators of these Boeing aircraft to conduct the inspection recommended by the FAA over six years ago.

“It has come to the notice of DGCA that several operators – internationally and domestic – have initiated inspection on their aircraft fleet” as per the FAA's bulletin, its order said.

It added: “In the view of above all airline operators of the affected aircraft are hereby advised to complete the inspection” suggested by the FAA “no later than July 21”.

Operators must report to the DGCA with their findings, the regulator said, adding that “strict adherence to the timeline is essential to ensure continued airworthiness and safety of operations”.

Air India had replaced the throttle control module – which includes the fuel cutoff switches – aboard the ill-fated aircraft in 2019 and 2023 but for reasons unrelated to the switches, the AAIB had also said.

Citing sources, PTI reported that the Air India group had already begun inspecting the locking mechanism of the fuel control switches on its Boeing 737s and 787s.

A number of Indian airlines operate Boeing 737s and 787s but some of them are registered outside India and do not fall under the DGCA's order, the news agency also reported.

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