NEW DELHI: The preliminary report on the Air India crash in Ahmedabad revealed that a 2018 US report had flagged the "potential for disengagement of the fuel control switch locking feature.

" According to the report, Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin (SAIB) No. NM-18-33, issued in December 2018, flagged potential disengagement of the fuel control switch locking feature in Boeing aircraft, including the B787-8 fitted with similar part numbers."This Special Airworthiness Information Bulletin (SAIB) is to advise registered owners and operators of The Boeing Company Model 717-200 airplanes; Model 737-700, -700C, -800, and -900ER series airplanes; Model 737-8 and -9 airplanes; Model 747-400, -400D, -400F, -8, and -8F series airplanes; Model 757-200, -200CB, -200PF, and -300 series airplanes; Model 767-200, -300, -300F, -400ER, and -2C series airplanes; Model 787-8, -9, and -10 airplanes; Model MD-11 and MD-11F airplanes; and Model MD-90-30 airplanes of the potential for disengagement of the fuel control switch locking feature," the report said.Also read: Engine 1 and Engine 2 cut off within 1 second: What caused Air India plane crash? 10 key findings from probe report

"If the locking feature is disengaged, the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation. Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown," it added.However, the report revealed that the suggested inspections were not carried out as the FAA report was not "advisory and not mandatory."

What is the fuel control switch locking feature?

The fuel control switch locking feature is a safety mechanism used in certain aircraft to prevent the inadvertent shutoff or misoperation of the engine's fuel control switch. The fuel control switch has a locking feature to prevent inadvertent operation that could result in unintended switch movement between the fuel supply and fuel cutoff positions.Also read: Fuel switches found in ‘RUN’ position: Aftermath of AI 171 crash in images; what the wreckage showsIn order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position.

Such inadvertent operation could lead to serious consequences, including an unintended in-flight engine shutdown, which is a critical safety concern."The fuel cut-off switch is a physical switch, it has to be moved from one position to another, and it has to be moved from that position back. There is not automation involved in it. What automation is involved is the fuel shut-off valve," IAF pilot Captain (retired) Ehsan Khalid said."It has transitioned from run to cut-off or ON to OFF, if that is what was being recorded and if AAIB meant then it is a different thing but fuel switches being moved up and down automatically does not happen. So, AAIB report to that has made some of the answers right, some of the speculations are out of the window. Pilot action 100 per cent right, they tried to revive the engine that is further corroborated with the fact that there was some movement of the fuel cut-off switch.

The fact remains that the engine power was lost without pilot input is confirmed," he added.The Aircraft Accident Investigation Bureau released a 15-page preliminary report a month after the tragic crash, detailing the early findings and current status of the investigation into the crash of Air India Flight AI171, a Boeing 787-8 Dreamliner bound for London Gatwick. The aircraft crashed just moments after takeoff, slamming into a medical hostel complex near the airport.

Of the 241 people onboard, only one passenger survived.The AAIB report confirms that wreckage analysis, post-mortem reports, and component inspections are ongoing. "At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers," the agency said.Air India said that it is cooperating fully with the investigation."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," Boeing said.