Manas Dasgupta
NEW DELHI, July 12: The cockpit voice recorder (CVR), one of two black box components of the London-bound Air India flight that crashed in Ahmedabad soon after the take-off on June 12, captured a brief exchange between the pilots which is now at the centre of the detailed investigation to find out the causes of the crash.
Captain Sumeet Sabharwal, the commander and pilot monitoring (PM), and First Officer Clive Kunder, the pilot flying (PF), were both experienced and medically fit, with no reported issues that could have compromised their flying. As the engines faltered, one pilot — identity unconfirmed — asked, “Why did you cut off?” The other responded, “I didn’t.”
Was it a misunderstanding, an unacknowledged action, or an external factor beyond the pilots’ control? The fuel control switches on a Boeing 787 are not simple toggles. Each switch features a guard rail. To move a switch from “RUN” (forward) to “CUTOFF” (aft), a pilot must lift and shift it downward. This design minimises the risk of accidental movement, such as a hand brushing against it during flight.
Aviation experts said the fuel switch cannot be automatically moved. It is a mechanical process with enough built-in safeguards. “It has to be moved mechanically from Run to Cutoff position after landing. There is a safety guard at the base of the switch which can be moved only after the spring inside is physically lifted.”
The switches for Engine 1 and Engine 2 are spaced approximately two to three inches apart, making it improbable for both to be moved simultaneously without intent. Yet, the data confirms that both transitioned to “CUTOFF” within a single second.
As thrust diminished, the aircraft’s altitude began to drop. The black box indicates that the pilots acted swiftly, moving both fuel control switches back to the “RUN” position. This action, executed approximately 10 seconds after the initial cutoff, aimed to restore fuel flow and restart the engines.
Engine 1 responded and its core speed deceleration halted, reversed, and began to recover, with thrust levels rising. Engine 2 also relit, but its core speed continued to decelerate despite repeated attempts to reintroduce fuel and accelerate recovery. The thrust levers, found near idle in the wreckage, had remained forward until impact, per the flight data recorder (FDR).
Simultaneously, the Ram Air Turbine (RAT), a small propeller deployed automatically in the event of dual engine failure, extended from the fuselage during take-off. CCTV footage from the airport captured this deployment. The RAT provides emergency power to sustain critical systems, but it cannot generate thrust. With the aircraft barely a few hundred feet above ground, the partial recovery of Engine 1 proved insufficient. At 1:39:32 pm, Flight 171 struck the hostel, sparking a fireball that devastated the site.
The AAIB’s preliminary report, spanning dozens of pages, drew on data extracted from the heavily damaged black box units, one located in the forward section, the other in the rear.
These devices, designed to withstand extreme temperatures and impact, house memory chips that record flight data. The National Transportation Safety Board (NTSB) of the United States provided specialised equipment to retrieve this data. The investigation now centres on the fuel control switches. Three primary theories are under scrutiny:
Human Action: Did one pilot deliberately or inadvertently move the switches? The cockpit exchange suggests neither accepted responsibility. “No pilot in their right mind would do this. The switches require intentional effort-lifting and moving them past a guard rail. It’s not a light switch you flick by mistake,” a former commander said.
Mechanical Failure: Could a defect have caused the switches to move independently?
External Factors: Could fuel flow have ceased despite the switches remaining in “RUN”? The report finds no evidence of this.
The AAIB has ruled out other variables. No significant bird activity was detected, negating a bird strike theory. The Auxiliary Power Unit (APU), a rear-mounted mini jet engine, was operational and attempted an autostart to assist engine relight, but its role was secondary to the switches’ position. Crucially, the report states there is “no immediate evidence of sabotage.”
The AAIB report has mentioned cockpit conversation between the two pilots as recorded by the flight data recorder. One of the pilots asks the other why the fuel cutoff switch has been moved but the second pilot says he hasn’t done so. “In the cockpit voice recording, one of the pilots is heard asking the other why did he cut off. The other pilot responded that he did not do so,” the report says. At this point, the report does not identify who asked the question and which pilot responded.
Doubts have been raised over the selective use of the cockpit transcript. The flight was airborne for about 38 seconds, but AAIB has only released one exchange between the pilot and the co-pilot. That in such a crisis no other communication happened between the two seems very unlikely. Is the data from the cockpit voice recorder impacted? Is that why the full transcript, which could have shed more light on what happened, has not been released?
The pilot association too is unhappy. In a statement, the association said: “The tone and direction of the investigation suggest a bias toward pilot error. We categorically reject this presumption and insist on a fair, fact-based inquiry.”
The AAIB, however, has not recommended any further action by the engine or the aircraft manufacturers. “At this stage of investigation, there are no recommended actions to B787-8 and/or GE GEnx-1B engine operators and manufacturers,” the report states, leading to more questions on whether preliminary probe has ruled out mechanical failures.
