Exclusive | AI-171 crash triggered by fuel switches or engine failure?

When Air India Flight AI-171 crashed seconds after takeoff from Ahmedabad on June 12, killing 260 people, Western media spoke widely of pilot error.

Now, a chain of new evidence and sources is flagging the possibility of a larger electronic and mechanical failure.

Also read: Ahmedabad Air India plane crash report highlights: 10 things AAIB said

A core mystery remains: what came first, the engine shutdown or the fuel switches being turned off? Pilots and airlines globally are now pondering the question of whether the fuel switches being moved to cutoff caused the engines to die, or whether the engines were already starting to fail on their own, and the aircraft’s automated systems responded by shutting off the fuel.

Role of FADEC

This is where FADEC (Full Authority Digital Engine Control) comes in. FADEC is like the brain of a modern jet engine. It constantly monitors sensors and adjusts things like fuel flow and engine speed automatically.

Did the fuel switches move causing engines’ shutdown? Or, did FADEC, possibly misled by bad sensor readings, trigger the shutdown on its own, leaving the crew scrambling to restart the engines? That chicken and egg problem could be at the heart of the AI-171 investigation.

In certain situations, it can even override the pilots if it believes something’s gone wrong, like cutting fuel if it thinks the throttle has been pulled back too far or if engine sensors are feeding it faulty data.

So the question is, did the fuel switches move causing engines’ shutdown? Or did FADEC, possibly misled by bad sensor readings, trigger the shutdown on its own, leaving the crew scrambling to restart the engines? That chicken and egg problem could be at the heart of the AI-171 investigation.

Also read: AI replaced Throttle Control Module in crashed plane twice on Boeing order

European airline's move

A major European airline is now looking into the possibility of sensors triggering a FADEC shutdown. Two sources from the airline told The Federal their maintenance engineers have been asked to look into sensors, four days after they were asked to check the lock mechanism on fuel switches in the Boeing 787 Dreamliner.

[Read disclaimer at the end of the article.]

As cockpit voice recordings were selectively released, the only thing the world knew was that one of the pilots had asked about the switched-off fuel switches.

The Wall Street Journal hinted at the former, citing sources close to the investigation who suggested Captain Sumeet Singh might have manually switched off the fuel controls. But that claim now faces serious questions after The Indian Express broke a new angle: a faulty stabiliser sensor had been malfunctioning even before the crash.

Stabiliser sensor malfunction

According to the IE report, the Aircraft Accident Investigation Bureau's (AAIB) preliminary report logs an anomaly in the STAB POS XDCR (stabiliser position transducer) — a sensor that feeds data about the plane’s pitch attitude into multiple onboard systems, including FADEC.

Also read: Ahmedabad Air India plane crash: A timeline of events

It said the preliminary AAIB report has logged a key anomaly: a malfunction in STAB POS XDCR, which may have triggered a fuel control anomaly. This specific sensor glitch was flagged during the initial diagnostic review, and maintenance engineers had reportedly conducted troubleshooting procedures on the system before the crash.

Earlier, the sensor fault was not considered serious enough to ground the aircraft. But now, that minor anomaly may be central to the crash.

While the report stops short of directly linking the sensor fault to the dual engine shutdown, it underscores the possibility of a cascading failure, where a faulty sensor input could have misled the aircraft’s automated systems, possibly affecting fuel flow or engine response.

Back then, the fault was not considered serious enough to ground the aircraft. But now, that minor anomaly may be central to the crash.

Focus on engine sensors

While many airlines have been conducting safety checks on fuel control switches after the FAA’s 2018 advisory, sources at a major European airline have confirmed to The Federal that their internal team is now focusing on engine-related sensors, including stabiliser transducers and thrust lever angle (TLA) inputs, not just switches.

Also read: Air India to partially resume services suspended after crash from August 1

One senior aircraft systems engineer from the carrier said, "What we’re trying to see in our maintenance checks is the sensors."

2 plausible technical scenarios

At some point during cruise, both engines of the Boeing 787 Dreamliner operating AI-171 shut down in close succession. Crucially, the Cockpit Voice Recorder (CVR) did not capture any pilot action or verbal confirmation of having moved those switches.

The aft (tail) section of the Enhanced Airborne Flight Recorder (EAFR), which could have recorded whether the aircraft’s FADEC system issued a shutdown, reportedly suffered damage and could not be retrieved. Though the cockpit recordings – also in the tail section of the plane, only a feet away – were retrieved and released.

With the digital trail incomplete, there are now two possible scenarios.

Scenario 1: FADEC shutdown from sensor fault

A 2013 incident involving an All Nippon Airways (ANA) Boeing 787 (tail number JA804A) offers a revealing precedent. While taxiing after an emergency landing at Takamatsu Airport, one of the aircraft’s engines shut down without any pilot command.

Investigators traced the anomaly to a malfunction in the thrust lever resolver sensor — a key input to the FADEC system. The faulty sensor sent an incorrect signal suggesting the throttle had been retarded, prompting FADEC to automatically shut off fuel to the engine.

Though the aircraft was safely on the ground, the case exposed how misleading sensor data could override pilot intent and trigger fuel cut-off. For AI-171 investigators, it raises the possibility that a faulty sensor in the stabiliser or throttle input system may have played a similar role.

How this mirrors the AI-171

The STAB POS XDCR sensor glitch may have corrupted stabiliser input. The FADEC, seeing invalid control surface or pitch data, could have interpreted the inputs as a critical failure.

That would lead to a protective engine shutdown, with no pilot input required. This is precisely the logic fault suspected in AI-171, but happening at takeoff thrust — making the outcome far deadlier.

Scenario 2: Fuel Switch Lock Failure (FAA SAIB NM-18-33)

In December 2018, the FAA issued SAIB NM-18-33, warning of a design flaw where fuel control switch locks in some Boeing 787 aircraft could fail. This might allow the switches to move from RUN to CUTOFF during vibration or turbulence; even without human touch.

Air India did not comply with this advisory; it was not mandatory.

If this failure occurred during AI-171's takeoff roll, it could explain the near-simultaneous engine flameout.

Interpretation:

The 1-second gap between fuel switch 1 and 2 shutting shows it was too fast, too precise to be humanly possible.

The longer 4-second delay between fuel switch 1 and 2 shows how long it took the pilot — his fastest reaction time —as both pilots battled to save the aircraft.

The fact that it took one second for fuel switch 2 to move from RUN to CUTOFF, but took four seconds for the pilot to move fuel switch 2 from CUTOFF to RUN, suggests that the locking mechanism was working and in place; possibly ruling out scenario 2 (the faulty fuel switch theory).

There is evidence that further supports the FADEC theory over the fuel switches theory.

Engine relight performance

Data from the EAFR showed that Engine 1's core deceleration halted and began reversing, suggesting signs of recovery after fuel was switched back to RUN.

Engine 2 also briefly relit, but its core speed kept falling despite multiple restart attempts. Three pilots The Federal spoke to said this pattern suggests the engines’ behaviour wasn’t solely caused by fuel starvation but possibly by a malfunction already underway.

Combustion during relight attempts

The exhaust gas temperature (EGT) in both engines rose following the reversal of the fuel control switches, indicating that combustion did occur during the relighting sequence.

The pilots The Federal spoke to also said that this reinforces the idea that the engines were not completely deprived of fuel, and that the shutdown may not have been initiated purely by switch movement.

Recorder damage

The aft EAFR, which may have contained additional FADEC and switch data, was too badly damaged to be downloaded using conventional methods. While the forward EAFR was successfully recovered, the loss of aft data has limited investigators’ ability to reconstruct the full sequence of events and raised concerns about what key inputs might be missing.

Together, these clues point to a more complex picture than one of accidental fuel cutoff alone. If Engine 1’s deceleration reversed on its own, and Engine 2 reignited but failed to stabilise, it suggests there may have been pre-existing failures in the control or sensor systems.

The presence of combustion and the partial recovery of one engine complicate the narrative that the fuel switches were mistakenly moved to cutoff and nothing more. And the absence of full recorder data leaves a crucial gap in the timeline, one that could obscure whether the engines failed before or because of the switch movement.

These points bolster the theory that the engine malfunction occurred first, with fuel switches moved as a reaction, not the trigger.

Blame the pilots?

Boeing has a well-documented history of initially blaming pilots for crashes — often non-Western crews — before deeper systemic faults come to light. In the 2018 Lion Air and 2019 Ethiopian Airlines disasters, early blame fell on the pilots, only for investigations to reveal a hidden MCAS (Maneuvering Characteristics Augmentation System) design flaw.

Also read | PIL in Madras HC aims to protect pilots from defamatory media coverage

In the 2024 Alaska Airlines door plug incident, Boeing pointed to maintenance before broader quality control failures were uncovered. Multiple FAA audits between 2023 and 2024 have since exposed systemic lapses across Boeing’s production lines.

The early narrative around Air India Flight AI-171 risks following the same pattern. But emerging evidence suggests this was not a case of pilot error, and that on AI-171 they may have been the last line of defence against a plane that may have already been failing them from the inside.

Disclaimer: The AAIB has not yet released its final report on the AI-171 crash. All technical scenarios presented here are based on preliminary information and remain hypotheses. Airlines routinely conduct both scheduled and precautionary checks, especially following major incidents. Sources emphasised to The Federal that such checks are standard procedure and do not, by themselves, indicate any confirmed fault in the system.