[aviation news]
The preliminary report of the crash of Air India flight AI171 is beginning to create insight into whether this is potential pilot error or whether this is the result of potentially a missed maintenance bulletin.
Such findings in the preliminary report place significant focus on the Fuel Control cut-off switches.
Of course, at this stage, we are still in the preliminary stages of the reporting, so anything else can come up as the investigation continues.
A Recap of What Was Said in the Preliminary Report…
According to the AAIB report, the aircraft reached a maximum recorded airspeed of 180 knots Indicated Airspeed (IAS) at approximately 08:08:42 UTC during its takeoff phase.
Fuel Control Switches in CUTOFF Position
Almost immediately, a critical malfunction occurred: both Engine 1 and Engine 2 fuel cutoff switches moved from the “RUN” to “CUTOFF” position within a one-second interval.
This action halted fuel supply to the engines, causing the engine speeds (N1 and N2) to drop from their takeoff values.
The cockpit voice recording captured a moment of confusion, with one pilot questioning the other about activating the fuel cutoff switches.
The second pilot denied doing so, suggesting the switch activation may have been unintentional or caused by a system error.
Engine Power Loss & Subsequent Relight
As the engines lost power, the aircraft’s systems responded. By 08:08:47 UTC, the Ram Air Turbine (RAT) hydraulic pump activated to provide hydraulic power, compensating for the loss of engine-driven systems.
The EAFR data shows that at 08:08:52 UTC, the Engine 1 fuel cutoff switch was moved back to the “RUN” position. This was then followed by Engine 2 at 08:08:56 UTC.
When fuel control switches are returned to “RUN” during flight, the Full Authority Digital Engine Control (FADEC) system initiates an automatic relight and thrust recovery sequence.
The report indicates that Engine 1 began to recover. The engine’s core speed was stabilizing and exhaust gas temperature (EGT) rising, signaling a successful relight.
Engine 2, however, struggled. Although it relit, it could not sustain core speed acceleration, requiring repeated fuel reintroduction to attempt recovery.
Mayday Call Issued
The EAFR stopped recording at 08:09:11 UTC, leaving some gaps in the final moments of the flight. At 08:09:05 UTC, one of the pilots transmitted a distress call: “MAYDAY MAYDAY MAYDAY.”
The Air Traffic Control Officer (ATCO) requested the flight’s call sign but received no response. The ATCO then observed the aircraft crashing outside the airport boundary and promptly activated the emergency response.
By 08:14:44 UTC, the Crash Fire Tender, supported by local fire and rescue services, left the airport. The assets then carried out rescue and firefighting operations.
Physical Evidence from the Wreckage
The wreckage provided further clues about the aircraft’s configuration at the time of impact.
Flaps Set for Takeoff; Gear Selected DOWN
The flap handle assembly was heavily damaged by fire (see above). It was found in the 5-degree flap down position, consistent with a standard takeoff setting. This was corroborated by EAFR data.
The landing gear lever was in the “DOWN” position, indicating the gear was likely extended. It is unclear if this was intentional or a result of the emergency.
The thrust lever quadrant also sustained significant thermal damage. Both thrust levers were found near the idle position. The EAFR data revealed that they remained in the takeoff thrust position until impact. This suggests the physical position of the levers was altered post-crash.
Fuel Control Switches in RUN Position
Both fuel control switches were found in the “RUN” position, aligning with the pilots’ attempts to restore engine power. The thrust reverser levers were bent but stowed, and the wiring for the Takeoff/Go-Around (TO/GA) switches and autothrottle disconnect switches was heavily damaged.
Pilot Error or a Missed Maintenance Bulletin?
Last night’s release of the report has developed into a focus on a particular maintenance bulletin released in 2018.
Labelled SAIB NM-18-33, it contains some information about the potential for disengagement of the fuel control switch locking feature, which is on a range of Boeing aircraft, involving the 787-8, which was used to operate Air India flight AI171, which crashed.
The bulletin reads:
The Boeing Company (Boeing) received reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged.”
“The fuel control switches (or engine start switches) are installed on the control stand in the flight deck and used by the pilot to supply or cutoff fuel to the engines.”
“The fuel control switch has a locking feature to prevent inadvertent operation that could result in unintended switch movement between the fuel supply and fuel cutoff positions.”
“In order to move the switch from one position to the other under the condition where the locking feature is engaged, it is necessary for the pilot to lift the switch up while transitioning the switch position.”
“If the locking feature is disengaged, the switch can be moved between the two positions without lifting the switch during transition, and the switch would be exposed to the potential of inadvertent operation.”
“Inadvertent operation of the switch could result in an unintended consequence, such as an in-flight engine shutdown.”
“Boeing informed the FAA that the fuel control switch design, including the locking feature, is similar on various Boeing airplane models.”
“The table below identifies the affected airplane models and related part numbers (P/Ns) of the fuel control switch, which is manufactured by Honeywell.”
If this bulletin is anything to follow, then this is significant.
And below is why this is the case.
Will Boeing Be Liable? Or Will Air India?
At this stage, it is unclear who would be liable based on this new development following the preliminary report release of the Air India flight AI171 crash.
As per Times of Indiait has been reported that the 2018 Airworthiness Directive was only an advisory, and did not require mandatory inspections.
There are questions to ask, with this in mind of course:
- Why did the FAA or Boeing mark it as an advisory?
- Should there have been mandatory inspections?
- Even though it was advisory, did Air India perform any of these checks in 2018?
- Do global checks of the Boeing 787 need to be carried out?
All of these points will need to be considered moving forward.
If the cut-off switches were transitioned by the pilot directly, then Air India would be liable.
However, if the airworthiness directive offers cause, then everyone could be liable.
Boeing because they should have made the inspections mandatory.
Air India because they should have done the checks regardless.
The FAA also for not being strict with issuing mandatory inspections as well.
However, we must wait for the full report on this.
The Full Report Will Establish Exactly What Happened in the Crash…
For the crash of Air India flight AI171, the investigation continues into whether it is pilot error or whether it’s a wider issue.
It is clear a lot was noted already in the preliminary report.
As the investigation continues, all eyes will be on what the full report will say.
This full report will no doubt contain some significant recommendations if more developments shed to light.
Whatever the cause, all eyes are now on the AAIB to bring the investigation to a high-quality and detailed close.
As soon as we have more information, then we will continue to update you on the AviationSource website.
More to follow in due course.
Stay tuned.
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