'Why did you cut off the fuel supply? I did not': AAIB preliminary report into AI-171 crash released; cockpit recording indicates fuel to both engines cut off

Time of India

a day ago

A preliminary report on the Air India flight AI-171 crash that killed 270 reveals a chilling detail: fuel supply to both engines cut off shortly after takeoff. Pilots denied responsibility, raising questions about technical malfunction or deliberate action.
MUMBAI: About seven seconds after Air India flight AI-171 lifted off Ahmedabad runway on June 12, the fuel to both engines of the Boeing 787 Dreamliner (VT-ANB) cut off. Within a time gap of one second, fuel to both engines was cut off.
"In the cockpit voice recording, one of the pilots is heard asking the other why he cut off the fuel supply. The other pilot responded that he did not do so."
This is the most crucial bit of information in the 15-page preliminary report into the fatal Air India accident that killed 270 people. India's Aircraft Accident Investigation Bureau (AAIB) released the report to the public in the early hours of Saturday.
You Can Also Check:
Mumbai AQI
|
Weather in Mumbai
|
Bank Holidays in Mumbai
|
Public Holidays in Mumbai
The big questions are: if the pilots didn't cut off the fuel, then how did the fuel supply to both engines cut off during the most crucial phase of flight? Was it a technical problem with the Boeing 787 Dreamliner? The only other logical possibility is one of the pilots cutting off the fuel supply and saying he didn't.
The final report into the accident which will be released by June 12, 2026 will likely give the answers and reveal the probable causes of the accident.
This is the sequence of events put down in the AAIB report.
The aircraft started rolling at 08:07:37 UTC. As per the EAFR (the digital flight data recorder) data, the aircraft crossed the take-off decision speed V1 and achieved 153 kts IAS at 08:08:33 UTC. This is the speed at which a take-off should be continued and should not be aborted for any reason.
The Vr speed (155 kts) was achieved as per the EAFR at 08:08:35 UTC. The Vr speed is the speed at which the pilots pull back the control column to lift the nose and lift off the ground.
The aircraft air/ground sensors transitioned to air mode, consistent with lift-off at 08:08:39 UTC.
The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC, and immediately thereafter, the Engine 1 and Engine 2 fuel cut-off switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec.
The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off.
"The CCTV footage obtained from the airport showed Ram Air Turbine (RAT) getting deployed during the initial climb immediately after lift-off (fig. 15). No significant bird activity is observed in the vicinity of the flight path. The aircraft started to lose altitude before crossing the airport perimeter wall," the report says.
While the commander of the flight had over 15,000 hours of flying experience, including about 8,600 hours on the B787, the co-pilot had 3,400 hours of flying experience. The co-pilot was Pilot Flying (PF), and the PIC was Pilot Monitoring (PM) for the flight.
The investigation has noted the relevance of US aviation regulator, Federal Aviation Administration (FAA) Special Airworthiness Information Bulletin (SAIB) No.
NM-18-33, issued in December 2018. It highlighted reports from operators regarding potential disengagement of the fuel control switch locking feature in Boeing aircraft, including the B787-8 fitted with similar part numbers.
Although the SAIB did not result in an Airworthiness Directive (AD) and was advisory in nature, it recommended inspection of the fuel control switch installations to ensure proper locking function.
"As per the information from Air India, the suggested inspections were not carried out as the SAIB was advisory and not mandatory," the report said. Records indicate that VT-ANB underwent throttle control module replacements in 2019 and 2023, unrelated to fuel control switch faults, and no subsequent fuel control switch defects were documented after 2023, it added.
"At this stage of the investigation, no definitive cause has been determined, and no immediate safety recommendations have been issued to B787-8 or GEnx-1B engine operators," it said, adding that the Aircraft Accident Investigation Bureau (AAIB) of India, supported by NTSB-USA, Boeing, GE, FAA, and other international stakeholders, continues a detailed investigation focused on engineering, human factors, and system interactions.
The Times of India spoke to senior commanders and examiners, and they referred to another service bulletin issued jointly by FAA and GE (engine manufacturer) in 2021. Service Bulletin FAA-2021-0273-0013 Attachment 2 recommends the replacement of the "MN4 microprocessor on ECU" with respect to engine fuel and control. It states: "This recommendation is to address a condition that may affect Flight Safety... Accumulated thermal cycles of the EEC with age causes the solder ball to fail.
"
What is the MN4 Microprocessor and what is the Engine ECU? ECU stands for Engine Control Unit, and it's like the "brain" of the modern jet engine. It monitors crucial engine parameters such as temperature, pressure, and RPM. But most importantly in this context, it controls fuel flow, variable geometry components, starting, and other functions to ensure optimal performance, efficiency, and safety.
The MN4 is an integrated microprocessor used inside the ECU.
It handles critical processing tasks such as interpreting sensor data, executing engine control algorithms, sending signals to actuators such as fuel metering valves, and managing fault detection and communication with cockpit systems.
Why did the FAA recommend replacement of the MN4 Microprocessor? "Solder Ball Fatigue" was the crucial issue. "The microprocessor is mounted on a Ball Grid Array (BGA), which uses tiny solder balls to attach the chip to the circuit board.
As the aircraft flies, the engine experiences high temperature swings, constant vibration, and thermal cycling (repeated heating/cooling during engine start/shutdown).Over time, this thermal cycling causes fatigue cracks in the solder balls, leading to intermittent electrical connections, loss of signal processing, and potential engine control faults," explained a senior commander.
A failing microprocessor could disrupt fuel flow control, cause engine flame-out, prevent proper engine restart, and trigger dual engine shutdowns (a catastrophic scenario).
The question is, what was the microprocessor status on the AI B787 that crashed?
Capt Sam Thomas, President of the Airline Pilots' Association of India (APAI), said: "The conversation between the pilots enquiring who cut off the fuel control switch is alarming." Another crucial issue is, why did the Emergency Locator Transmitter not work after the accident? It should emit signals if the force of impact is between 3.2 to 3.5 G; the impact of the accident would have been exponentially higher.
He also raised a question about the composition of the investigating team. "Who is the expert in this group? It is assumed that some B787 Dreamliner pilots have been... Why the secrecy? We know pilots in India, and none of them have been consulted. IAF pilots are not competent enough to investigate and understand modern aircraft operated by civilian airlines." The AAIB said: "The investigation team comprising Mr. Sanjay Kumar Singh as Investigator-in-Charge, Mr.
Jasbir Singh Larhga as Chief Investigator, and Mr. Vipin Venu Varakoth, Mr. Veeraragavan K, and Mr. Vaishnav Vijayakumar as Investigators. Experienced Pilots, Engineers, Aviation Medicine Specialist, Aviation Psychologist, and Flight Recorder Specialists have been taken on board as Subject Matter Experts (SMEs) to assist the Investigation in the area of their domain expertise," the report said.