Ahmedabad plane crash: AI 171 crash preliminary report, released by India’s investigation agency – Aircraft Accident Investigation Bureau (AAIB) – has put a spotlight on the fuel switch cut-off. The report stated that the fuel switch transitioned from “Run” to “Cutoff” and was recovered in “Run” mode from the crash site in Ahmedabad. 

The 15-page AAIB report also mentioned a paraphrased conversation between Captain Sumeet Sabharwal and First Officer Clive Kunder. One of the pilots asked the other why he had cut-off the fuel supply to the engine. The other pilot responded that he had not. Soon after, the cockpit issued a Mayday call to ATC and AI 171 crashed into the hostel for medical students 15 seconds later. The report doesn’t mention how or why the fuel switch transitioned.

So, if pilots didn’t do it, as heard in their conversation, then how did the switch move? To understand this, we got in touch with the US aviation expert, Mary Schiavo. She rejected the claims of human error that a pilot downed the Ahmedabad to London flight by cutting off the fuel supply. 

“There is no evidence of this,” she told us, before adding, “The voices, words and sounds on CVRs must be carefully analysed. There is nothing here to suggest pilot suicide or murder. The full transcript of the CVR should be released ASAP to avoid harmful paraphrasing.”

‘It happened in 2019, too’

Schiavo exclusively told FinancialExpress.com that this is not the first time fuel switch transitioned from “Run” to “Cutoff” on its own. It happened five years ago, too.

“There was an ANA flight in 2019 in which the 787 aircraft did this itself, while the flight was on final approach. No pilot input cutting off the fuel whatsoever,” Schiavo told FinancialExpress.com.

But how did it happen?

She said that a glitch in Boeing 787 software led to the transition in fuel switch. 

“The investigation revealed the plane software made the 787 think it was on the ground and the Thrust Control Malfunction Accommodation System cut the fuel to the engines,” she told FinancialExpress.com, before adding, “The pilots never touched the fuel cutoff.”

All Nippon Airways (ANA) flight, which took-off from Tokyo to Osaka with 109 passengers and 9 crew members, suffered a dual engine failure. Both engines flamed out immediately after the pilot deployed the thrust reversers for landing. The aircraft, which was also a Boeing 787 Dreamliner, was towed away from the runway by the authorities, and no injuries were reported. 

UK Civil Aviation Authority (CAA), four weeks before the crash, had warned about similar fuel system issues on Boeing aircraft. “The FAA has issued an Airworthiness Directive addressing a potential unsafe condition affecting fuel shutoff valves installed on Boeing aircraft,” the UK regulator’s notice read, listing the B737, B757, B767, B777 and B787.

The fuel control switches are located inside the Throttle Control Module (TCM). While it was replaced on the doomed AI 171 in 2019 and 2023, the locking mechanism of the fuel switch was not inspected by Air India despite a 2018 FAA advisory. This is also because the advisory was not mandatory. 

How did the plane go down within a few seconds? 

Schiavo told FinancialExpress.com that while Boeing 787 can fly on one engine, in Air India’s case, both engines failed simultaneously. “While the 787 can fly on one engine, here both engines’ fuel supplies were allegedly cut off,” the US aviation expert told FinancialExpress.com. 

She added, “The pilots did not have time and altitude to restart and regain the thrust necessary to generate enough airflow over the wings to keep the plane flying.”

The preliminary crash report, released on July 12, mentioned, “Engine 1’s core deceleration stopped, reversed and started to progress to recovery. Engine 2 was able to relight but could not arrest core speed deceleration and reintroduced fuel repeatedly to increase core speed acceleration and recovery.” 

‘Not enough time to restart the engine’

When we asked why the second engine couldn’t restart and why the RAT (RAM Air Turbine) didn’t function and lift the plane as expected, she explained that there was a very small window between the deceleration of the engines and the impact. It began to lose altitude even before crossing the airport perimeter wall. 

“There was not enough time. Restarting an engine in flight can take several seconds (and in some engines, you have to do a diving restart),” she explained. The flight AI 171 crashed almost two minutes after it was cleared for take-off.

She added, “The RAT is a small amount of power just to run the hydraulics and provide some electrical output so you can control (steer) the plane.” RAT is the emergency power system that helps an aircraft land safely during emergencies. The report also noted that ELT did not activate when the aircraft crashed, pointing to a possible malfunction of the system. ELT helps search and rescue teams locate the aircraft in case it goes missing.

‘Was Boeing 787 inspected for TCMA flaws?’

In a previous interview with the FinancialExpress.com, Schiavo hinted at a possible TCMA (Thrust Control Malfunction Accommodation) failure that could have led to the crash. However, when the AAIB report came out, it did not mention TCMA. TCMA informs FADEC about whether the aircraft is on the ground or in the air, and if it believes the aircraft is on the ground, it may automatically throttle back the engines, without the pilot’s input.

“I think it should be on the table in the investigation. It happened before, and the 787s are around the same age. Was the 787 aircraft inspected for those TCMA flaws? That is a very big question right now.”

If AAIB gave a clean chit to Boeing, then…

The report also stated “no recommended actions” for Boeing or its 787-8 Dreamliner. It also said that at this stage of the investigation, no actions have been issued for the aircraft, its engine operators as well or the manufacturers.

So, many thought that Boeing had been given a clean chit in what is labelled as one of the world’s worst aviation disasters. 

The US aviation expert thinks otherwise. She said that the preliminary report has not given a clean to the Boeing software, and if it indeed did, it is a serious violation of aviation accident investigation protocol.

“The first crash was immediately blamed on the pilots. The hidden software errors remained ticking time bombs. Then the second deadly crash happened. The whole point of aviation accident investigation by governments is to avoid the second, third or more accidents that would otherwise follow,” she further said.