Ahmedabad plane crash: The Aircraft Accident Investigation Bureau (AAIB), which has been investigating the tragic AI 171 crash that killed all but one passengers on board, has released its 15-page preliminary report into what went wrong with the Air India plane that crashed on June 12 in Ahmedabad, a few seconds after take-off for London, news agency Reuters reported. The investigating agency further stated that it has completed the drone photography or videography of the wreckage site and that the aircraft’s parts have been moved to a secure area near the airport.
“Both engines were retrieved from the wreckage site and quarantined at a hangar in the airport,” the AAIB report further mentioned. This was the first time that the best-selling wide-body Dreamliner or Boeing 787 suffered a fatal crash resulting in hull loss.
The news agency further reported that at this stage of the investigation, no safety recommendations have been issued for B787-8 aircraft or GE GEnx-1B engine operators and manufacturers.
Three seconds after take-off
Three seconds after taking off, the aircraft’s engine’s fuel cutoff switches almost simultaneously transitioned from run to cutoff. This means that the fuel did not reach the engine. This caused the aircraft to lose thrust and sink down, Reuters reported, citing the report.
The pilot’s Maydal call to ATC also revealed that the aircraft lost thrust and that the pilot was unable to lift it.
‘Did fuel switches move on their own?’
US aviation safety expert Anthony Brickhouse said that the way switches moved is inconsistent with normal operations. “Did they move on their own, or did they move because of the pilots?” he asked. “And if they were moved because of a pilot, why?”
Another aviation safety expert from the United States, John Cox, said the fuel switches that feed the engines couldn’t be moved by the pilots accidentally. “You can’t bump them and they move,” he said.
‘Engine was able to relight but…’
AAIB, in its initial findings, further said that Engine 2 was able to relight, but could not arrest the core speed deceleration and repeatedly re-introduced fuel in an attempt to recover. It added that Engine 1’s core deceleration stopped, then reversed, and began progressing toward recovery.
While the investigation is underway, the agency investigating the crash further stated that the complete analysis of postmortem reports of crew and passengers is being taken into account to corroborate aeromedical findings with engineering expertise.
The initial probe suggests that Engine 1’s fuel cutoff switch transitioned from “Run” to “Cutoff” at 1:38:52 pm, followed by Engine 2 making the same transition at 1:38:56 pm. Following this, the Exhaust Gas Temperature (EGT) was observed to be rising for both engines, indicating relight activity.
‘Why did you cut off the fuel?’
The AAIB report also revealed the conversation that happened inside the cockpit, moments before the crash. One of the pilots asked the other, “Why did you cut off?” To this, another pilot, who could be a co-pilot, responded, “I did not do so.”
The Engine and Flight Recorder (EAFR) data reveals that both engines’ N2 values dropped below the minimum idle speed, Reuters reported, citing the AAIB probe on the Air India crash.
The AI 171, which started descending abruptly at the rate of 475 feet per minute after reaching an altitude of 625 feet, reached a maximum speed of 180 knots indicated airspeed (IAS) at 1:38:42 pm. Soon after this, the fuel cut-off switches for both engines transitioned from “Run” to “Cutoff” within seconds of each other.
The fuel switch is most often used to turn engines off once a plane has arrived at its airport gate and in certain emergency situations, such as an engine fire. However, the report does not indicate there was any emergency requiring an engine cutoff.
The investigation team will examine additional evidence that is being sought from stakeholders, AAIB stated in the preliminary report on the AI plane crash, PTI reported.
The plane’s two black boxes were recovered in the days following the crash and later downloaded in India. They provide crucial data such as altitude, airspeed and final pilot conversations, which help in narrowing down possible causes of the crash.
Air India plane crash: Key takeaways from AAIB report
1- The AAIB report confirms the dual-engine failure. It stated that both engines lost power shortly after take-off as the fuel switches transitioned from “Run” to “Cutoff” within seconds of each other.
2- The fuel supply to both engines had been interrupted, which is the standard operating procedure in case of a dual-engine failure by Boeing. The pilots tried restarting the engines but failed to recover before it crashed into the hostel for medical students and turned into a fireball.
3- Cockpit voice recordings reveal that one pilot asked another, “Why did you cut off?”. To this, another denied.
4- Since there was a dual engine failure, the emergency power system, the Ram Air Turbine (RAT), was deployed. RAT provides enough power to an aircraft to land safely.
5- The aircraft remained airborne for just 32 seconds and crashed 0.9 nautical miles from runway 23 of the Ahmedabad Airport into a hostel.