The worry lines in Air India Flight AI171 crash preliminary report

India Today

14-07-2025

A caution flag was raised quietly, six and a half years before Air India Flight AI171 last month plummeted from the Ahmedabad sky in one of the world's worst aviation tragedies. Back in December 2018, engineers at the US Federal Aviation Administration (FAA) had circulated an advisory about a component most pilots rarely worry about: the small, spring-loaded latches designed to lock the engine fuel-control levers firmly in the 'RUN' position on certain Boeing wide-body jets.The FAA's concern was specific and chilling: under some circumstances, the latch might disengage silently. Should the mechanism fail, even the normal frenzy of cockpit operations could work the lever backward, shutting off life-sustaining fuel supply to the plane's engines. The bulletin advised inspections, but significantly, did not made them mandatory. It was an advisory, a whisper in the cacophony of global aviation maintenance regulations. That whisper would go on to reverberate loud this June 12.advertisementThe Air India Boeing 787 Dreamliner flight to London was being helmed by the late Captain Sumeet Sabharwal. According to the 15-page preliminary report on how the plane crashed, Sabharwal, 56, an Airline Transport Pilot Licence (ATPL) holder, had some 15,638 hours of flying experience, including 8,596 hours on the Dreamliner. With him was the late First Officer Clive Kunder, holder of a commercial pilot licence and 3,403 hours of flight experience, of which 1,128 hours were on Boeing 787s.To the pilot community, it's disbelief that the pair's skill-set and experience on paper would allow them to accidentally bump the fuel-control switch—a critical part of the instrument panel—mid take-off. The plane, which had done over 41,800 hours since delivery in 2013, was fully certified for air worthiness; the last such approval had come just three weeks before the crash.
'The Boeing Company received reports from operators of Model 737 airplanes that the fuel-control switches were installed with the locking feature disengaged,' states the 2018 FAA advisory, detailing: '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 cut-off positions. In 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. 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.'In the case of Flight AI171, the sequence captured by the aircraft's digital flight data recorder (DFDR) and cockpit voice recorder (CVR) is tragically brief. At 08:08:35 UTC (Universal Time Coordinated)—that is around 1:38 pm IST (Indian Standard Time)—the Dreamliner rotated at 155 knots. Four seconds later, it was airborne. Then, within the span of a single heartbeat—one second—both engine fuel cut-off switches abruptly transitioned from 'RUN' to 'CUT-OFF'. Engine parameters immediately began to slip.advertisementThe CVR preserves the stunned disbelief in the cockpit. Captain Sabharwal's voice, sharp with alarm: 'Why have the engines shut down?' To which First Officer Kunder's response that 'I did not do it'. During examination of the wreckage, both thrust levers were found near idle position while the Enhanced Airborne Flight Recorder (EAFR) data shows they remained forward—at take-off thrust—until impact. It also notes that both fuel-control switches were found in 'RUN' position.What followed midair on Flight AI171 was a desperate, 30-second battle against physics. The aircraft's Ram Air Turbine (RAT) deployed automatically, a small propeller dropping into the airstream to generate minimal hydraulic and electrical power. The auxiliary power unit inlet door opened as its auto-start sequence engaged. Engine 1 managed to relight, its core speed clawing back upward. But Engine 2 stubbornly refused, its core speed continuing to plummet despite repeated automated fuel-flow commands.With insufficient thrust and altitude, the jetliner became a gliding tomb. At 08:09:05 UTC (1:39 pm IST), a terse 'Mayday' call crackled over the Air Traffic Control radio. Seconds later, Flight AI171, still heavy with fuel, slammed into a densely packed residential suburb just beyond the Ahmedabad airport perimeter. The impact and ensuing fireball were catastrophic.advertisementThe wreckage, scattered over 300 meters, told a grim story: initial contact inside an Army Medical Corps compound, shearing through trees, obliterating the northeast wall of a hostel, carving a path of destruction through five residential blocks before the fuselage disintegrated. The vertical stabiliser lay 60 meters from the first impact point; engines and landing gear were embedded in roads and buildings. All 241 people on board were killed, besides 19 people on the ground.In the charred aftermath, teams of investigators from the government's Aircraft Accident Investigation Bureau (AAIB), with assistance from the Directorate General of Civil Aviation (DGCA), the US National Transportation Safety Board (NTSB), Boeing and engine-maker GE Aviation, descended upon the site. Drones captured the extent of the damage. Critical information emerged: the flap handle was set at five degrees; the landing gear lever was in down position, as it would be during take-off. Particularly, the mechanical control levers were found jammed in full forward position.This supported the DFDR information, which indicated that full power had been activated down to the final milliseconds of the flight. Its throttle-control module had been replaced twice, once in 2019 and again in 2023, maintenance logs showed. However, there was no information in the logs about reported faults concerning the latches.advertisementMore importantly, neither throttle-control module replacement prompted the specific inspections recommended in the 2018 FAA bulletin. Since the FAA action was not a mandatory airworthiness directive, compliance was left to the operator's discretion. 'We continue to fully cooperate with the AAIB and other authorities as their investigation progresses. Given the active nature of the investigation, we are unable to comment on specific details and refer all such enquiries to the AAIB,' Air India has said in a statement.The preliminary report on the crash, adhering to the International Civil Aviation Organisation (ICAO) principle of prioritising safety over blame, carefully avoids finger-pointing. It outlines the ongoing forensic work: detailed laboratory analysis of the recovered latches and switches; fuel samples and engine components; intense scrutiny of the 49 hours of flight data and two hours of cockpit audio; simulations testing the latching mechanism's integrity under stress; studies of system behaviour during sudden, catastrophic thrust loss; and evaluations of the human-machine interface during critical phases such as take-off.For the hundreds of families whose lives were forever altered by the deaths in air and on the ground, the lack of closure to the Flight AI171 crash is a bitter truth. But it will come, eventually. Aviation safety experts, however, say the real worth of this investigation will not be in punishment but prevention.advertisementAs one former pilot acknowledged: 'If a latch failure, and such an unannounced one at that, can kill both engines at the worst time, you had better understand why and how it happened.' Because every operator of these planes and every passenger boarding them deserves to know.Subscribe to India Today Magazine- EndsMust Watch