Breaking: India’s Air Crash Investigator releases AI 171 Incident’s Preliminary Report; Fuel Switch movement at the centre of the incident
On June 12, 2025, a fatal incident involving the first hull loss of a Boeing 787-8 happened, when Air India’s flight AI171 took off for departure from Ahmedabad to London Gatwick, and a few seconds later landed right outside the perimeter wall of the airport and went up in flames. Only one person survived among the souls on board, and many people also died in the hostel, which was right under the body of the aircraft.
Scenes from the wreckage of Air India AI171 on June 12, 2025.
AI 171 Preliminary Investigation Report
The Indian Air Crash Investigation body, Aircraft Accidents Investigation Bureau (AAIB), released the report in the wee hours of the morning of July 12, 2025, as per India Standard Time. You can read the 15-page report here.
In the report, the AAIB has recreated the timeline of the event. Here are the important excerpts:
- Fuel supply to both engines was cut mid-air: Just three seconds after takeoff, both the engines’ fuel control switches transitioned from RUN to CUTOFF within a second of each other, leading to a sudden loss of thrust.
- Pilots discussed in the cockpit: One pilot is heard asking the other as to why he cut off the engines, and the other one replied in the negative, implying he did not cut off the engines. Hence, there is the possibility of a technical malfunction or an inadvertent action.
- Relight attempt failed on one of the two engines: The flight data recorder shows that relight was automatically attempted and succeeded for Engine 1, but Engine 2 failed to recover despite multiple fuel reintroductions.
- RAT deployed: The Ram Air Turbine (RAT), which is an emergency power source, deployed right after lift-off, indicating a total loss of power to essential systems.
- Mayday call issued: At 08:09:05 UTC, a distress call was made, just seconds before the aircraft impacted the buildings outside the airport perimeter.
- Aircraft had 8 Degrees Nose Up at Impact: The analysis conducted by the AAIB shows the plane hit the buildings with a likely 8° nose-up attitude and level wings, but with both engines inactive, unable to sustain a climb.
- Cockpit controls were in normal takeoff mode: The flap and landing gear levers were in standard takeoff positions; thrust levers were found in idle position post-crash, though they were set at takeoff thrust during flight, thereby confirming an in-flight cutoff.
- The aircraft was airworthy with minor MEL issues: The plane had valid airworthiness certificates and a few Category C and D MELs (non-critical maintenance issues), none of which were linked to fuel control.
- Fuel adulteration did not exist: Fuel samples taken from the bowsers and tanks used to refuel the aircraft were tested
at the DGCA’s Lab and found satisfactory. A minimal number of fuel samples could be retrieved from the APU filter and the
Refuel/Jettison valve of the left wing. - No prior issues with fuel control switches: While Boeing had issued an advisory (not mandatory) on fuel control
switch lock concerns, Air India had not conducted the optional inspections. The aircraft had previous throttle module
replacements in 2019 and 2023.
For those interested in the verbatim, here is what the AAIB wrote,
As per the EAFR data, the aircraft crossed the take-off decision speed V1 and achieved 153 kts IAS at 08:08:33 UTC. The Vr speed (155 kts) was achieved as per the EAFR at 08:08:35 UTC. The aircraft air/ground sensors transitioned to air mode, consistent with liftoff 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 cutoff 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.
In the cockpit voice recording, one of the pilots is heard asking the other why did he cutoff. The other pilot responded that he did not do so.
As per the EAFR data both engines N2 values passed below minimum idle speed, and the RAT hydraulic pump began supplying hydraulic power at about 08:08:47 UTC.
As per the EAFR, the Engine 1 fuel cutoff switch transitioned from CUTOFF to RUN at about 08:08:52 UTC. The APU Inlet Door began opening at about 08:08:54 UTC, consistent with the APU Auto Start logic. Thereafter at 08:08:56 UTC the Engine 2 fuel cutoff switch also transitions from CUTOFF to RUN. When fuel control switches are moved from CUTOFF to RUN while the aircraft is inflight, each engines full authority dual engine control (FADEC) automatically manages a relight and thrust recovery sequence of ignition and fuel introduction.
The EGT was observed to be rising for both engines indicating relight. 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 re-introduced fuel repeatedly to increase core speed acceleration and recovery. The EAFR recording stopped at 08:09:11 UTC
At about 08:09:05 UTC, one of the pilots transmitted “MAYDAY MAYDAY MAYDAY”.
The ATCO enquired about the call sign. ATCO did not get any response but observed the aircraft crashing outside the airport boundary and activated the emergency response.
At 08:14:44 UTC, Crash Fire Tender left the airport premises for Rescue and firefighting. They were joined by Fire and Rescue services of Local Administration.
Next Steps in the Investigation
As next steps in the investigation, both engines have been retrieved and quarantined. The wreckage has been secured for detailed analysis. Witness statements, including that of the sole survivor, have been recorded. The post-mortem examinations are being reviewed for aeromedical insights. The limited fuel residue is being sent for testing.
So far, no safety advisories have been issued for the Boeing 787-8 aircraft or GE GEnx-1B engines.
The fuel switches, as they have been designed, and as discussed by The Air Current, have safeguards for accidental movement, and as per the TAC, they are only accessed on the ground to inject fuel (at startup) or cut off fuel (at arrival). Besides, they need a two-step process to go from Run to Cutoff, which seems impossible to do within a second, and especially for both of them to be done within a second of each other.
In 2018, the US Federal Aviation Administration (FAA) issued a special safety bulletin regarding potential issues with the locking mechanism on engine fuel control switches in Boeing 737 aircraft. This locking feature prevents the switches from being moved unintentionally. However, the FAA did not classify it as a significant safety concern and did not make inspections mandatory. Similar switches are used in the Boeing 787-8, including VT-ANB.
The aircraft maintenance records have shown that the aircraft’s throttle control module was replaced in 2019 and 2023, but not due to fuel switch concerns. No defects have been reported with the fuel control switch since 2023, the AAIB report said.
Air India has declined to comment on the issue so far and has referred queries to the AAIB.
Air India stands in solidarity with the families and those affected by the AI171 accident. We continue to mourn the loss and are fully committed to providing support during this difficult time.
We acknowledge receipt of the preliminary report released by the Aircraft Accident…— Air India (@airindia) July 11, 2025
Bottomline
While this is a developing story, the facts known so far include that the crew were in good health before the flight, and there was no issue with the aircraft as well. The focus will now be on the “Why”, which will analyse how both the Fuel Control switches move from Run to Cutoff as the plane lifts off. Of course, this is a preliminary report, intended to establish and lay down the facts, rather than respond to all the theories of what happened, which will be analysed, and the cause will be a part of the final investigation report.
What do you make of the Preliminary Facts laid out by the AAIB for the AI 171 Fatal Incident?
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