The 12 June crash of an Air India Boeing 787 sent shockwaves through not only the wider aviation industry, but the whole world. The accident was the first 787 hull loss, and one that Boeing could not afford to show any technical anomalies. After the preliminary report was released on July 12, the focus has narrowed in on the flight data recordings, which clearly showed that the engine fuel cutoff switches had been toggled, one after the other by one of the pilots.
The Air India 171 accident was one of the most tragic accidents in the history of commercial aviation, but it also offered a new glimpse into the state of global online communication. It exposed how much damage the online world could do as far as spreading disinformation, conspiracy theories and AI slop. The accident had barely happened when social media exploded with a proverbial tsunami-wave of internet content-sludge, claiming everything from faulty engines, acts of war and even extra-terrestrial activity.
AI slop, which is a new and as-yet not fully appreciated curse upon the online world took center stage not long after the accident, with an AI generated accident report claiming to be from the Indian ministry of civil aviation spreading online. It cast a pall upon the investigating team, who were already tasked with a high profile investigation under extremely difficult circumstances. Any experienced investigator can attest to how difficult a task it is to sift through the wreckage of a large commercial airliner with so many deceased victims. It also caused untold anguish to the families of those who were onboard. The Indian ministry of civil aviation however did little to stop the spread of misinformation, by maintaining an absolute silence until the prelim report was published a month later.
The preliminary report, which is linked at the bottom of this article, was well written and laid out the exact circumstances around the accident, without of course pointing to a root cause. The report detailed the physical aspects of the accident sequence, the (verified) visual evidence from photos and CCTV cameras, the details of the flight data recording, and a small snippet of transcript from the cockpit voice recorder.
Details from the report showed that:
- The flight crew were well rested on the day of the flight
- They were subjected to alcohol breathalyzer testing, and both found to be fit to fly
- The aircraft had done a previous leg with only one technical issue reported by the previous crew, related to a vertical stabilizer transducer status message.
- The aircraft was loaded within the normal acceptable limits
- The start sequence and taxi to runway was considered normal
- The weight and balance calculations, and well as takeoff speed reference calculations were performed correctly and followed on takeoff
- The takeoff sequence went according to plan right up until 08:08:42 UTC, when the engine fuel cutoff switches were toggled, one after the other, 1 second apart.
- The ram air turbine deployed right after in response to the engine fuel cut-off
- One of the pilots had clearly asked the other why he had toggled the fuel cutoff switches, after which he replied that he had not done so.
Fuel Control switches
What this shows is that the engines were effectively switched off. Whether or not that was on purpose is now the question. And this is where the investigating team will not only focus on human factors, but explore any and all possibilities that could have led to the cutoff switches being toggled, however remote the possibility. And this is where I wanted to focus for a moment.
Is there anything on the 787 that could have caused the fuel cut off switches to toggle, without the switches physically moving? Well in the universe we occupy, possibly.
The fuel cut-off switches in the 787 (which share commonality with those found in the 737 MAX) work solely on relays, meaning that there is no software input into the unit. Data is sent from the unit to the main computer to indicate it’s condition. The switches are spring loaded, with its natural position being in a downward seated position, with the catches on the base of the switch dictating its resting place. The switches are not susceptible to accidental activation due to this mechanism. One possibility is that the relays could have been operated due to a short, however this is highly unlikely due to the fact that the switches were switched back to “run”, and sufficient evidence exists in the flight data recordings to show that the engines had initiated a relight sequence in the few seconds left before impact.
The switch has been the subject of much controversy due to it featuring in an airworthiness bulletin issued by the FAA in 2018, with the switch’s spring described above being the subject of the bulletin. While an airworthiness bulletin does not mandate any action by any of the aircraft’s operators, the thrust control module within which the switch is located on the aircraft in question is said to have been replaced twice since the bulletin had been published. This is not confirmed, and to be confirmed only in the investigation’s final report.
The thrust control module that houses the fuel switches are replaced as part of regularly scheduled maintenance, where the unit itself is removed and sent away for refurbishment. Whether or not the faulty switches indicated in the FAA service bulletin were replaced will also need to be confirmed when the final report of this incident is published.
Human factors
Given what the flight data recorders have revealed about the fuel control switches, the most likely (and unfortunate) root cause is action by a crew member.
Given what is known about this incident, it is easy to deduce that either the captain or first officer moved the fuel control switches to the “cut-off” position. If it is proven that the switches were operated manually, the investigation will focus on two possibilities: either one of the flight crew moved the switches to the cut-off position with the intent of causing the aircraft to crash, or the switches were moved due to some form of confusion or mental lapse of reason. The flight crews autopsies, medical history and personal factors will all have to be taken into account.
Keep an eye on Gravitas as we cover this story as it unfolds.
Source: https://aaib.gov.in/What%27s%20New%20Assets/Preliminary%20Report%20VT-ANB.pdf
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