As the investigation into the crash of Air India’s Boeing 787-8 begins, the world has its sights set on the probe as scores of Boeing 787 aircraft are operating across the globe. Every serious aviation accident, however tragic, leaves in its trail critical lessons for the global aerospace and aviation industry to help avoid recurrence.
What is common to this accident and other aviation disasters is the phase of the flight during which it took place. The vast majority of aircraft crashes happen three minutes after takeoff or eight minutes before landing – the so-called critical phase of the flight. The AI 171 crash also happened in this critical phase.
What is unusual, though, is that this was a scheduled, regular flight by Air India, a major airline, and that it was connecting two major international airports, Ahmedabad and London Gatwick. So, laid down procedures would have been followed up until takeoff. AI 171 was also serviced by one of the most modern and sophisticated aircraft, the Boeing 787, which has an unblemished record in terms of serious accidents. The aircraft type has been in operation for over a decade, and this particular aircraft, VT-ANB, was among the early ones delivered to the airline in January 2014.
The retrieval of the black boxes – cockpit voice recorder (CVR) and flight data recorder (FDR) – is expected to be swift and without much damage as these devices are placed in the aircraft’s tail section, which appears largely intact. Air crash investigations can take years to reveal the exact cause or combination of factors that led to the accident, and the black boxes, with exhaustive flight operation data, are usually critical in the probe.
India’s Aircraft Accident Investigation Bureau (AAIB) is undertaking the investigation, while the US National Transportation Safety Board (NTSB) would also be involved in the probe, given that the aircraft is manufactured by an American company, Boeing, and was manufactured in Seattle. A UK AAIB team is also going to help with the investigation, and so are Boeing and other major component manufacturers like GE (engine manufacturer).
While it is too early to suggest the probable cause or combination of causes, the investigators would probe some key angles and possible factors as part of an exhaustive investigation.
Flaps and landing gear
Among the most striking things about the accident is the configuration of the flaps and the landing gear. A few aviation experts and pilots have pointed out that the flaps setting on the aircraft appears to not be in line with what is recommended during takeoff. Flaps are adjustable surfaces on the wing that are adjusted to change their shape, surface area, and curvature for different phases of the flight. During takeoff, flaps are deployed to produce lift at a low speed, helping the aircraft get airborne and climb. However, images and videos just before the crash suggest the flaps were retracted or not deployed to the extent required.
Story continues below this ad
The aircraft’s landing gear was still down and not retracted, which should not have been the case. With the landing gear down, additional drag might have been created for the aircraft, exerting an additional downward force. With a combination of incorrect flap configuration and landing gear still deployed, the aircraft would have needed more power to climb. Exactly what happened with the flaps – controlled by the electrical system – and the landing gear – operated through the hydraulic system – is expected to be a key focal point of the investigation.
It is worth noting that the 787 has built-in redundancies for various systems, particularly the electrical system, which means that the electrical system is expected to operate at a bare minimum level even if all power generators fail, allowing the pilots enough time to land safely at a nearby airfield.
To be sure, pilots and safety experts also underscored that had the pilots mistakenly punched in the wrong flaps settings or retracted the flaps, a sophisticated aircraft like the 787 would have set off a rather unmissable warning alarm in the cockpit, alerting the flight crew about the problem well in time to abort the takeoff and take corrective action. Also, pilots set flaps based on a detailed checklist and after taking various factors into account. Therefore, such an error would be extremely unusual, considering the flight crew had significant experience on the 787. At this stage, it would be premature to even hazard a guess on what exactly happened with these systems and the extent to which they had a role to play in the crash.
The heat has also been cited as a problem, given that it could be a factor when it comes to thrust and lift, but this heat wave in northern India has been ongoing, and aircraft took off in the same conditions from Ahmedabad till the crash happened. Also, Indian airlines and their pilots are well-versed and used to peak summer operations.
Story continues below this ad
Not enough power: Dual-engine failure, bird strike?
Videos also indicate that the plane struggled to lift and climb, reflecting a lack of requisite thrust. No one knows so far whether there was a problem with the engines, and it is likely to be a top priority item for the investigators. In any case, a single engine failure would not have been a major concern as modern aircraft can fly for hours on one engine. A simultaneous dual-engine failure would be a rarest-of-rare occurrence.
Fuel contamination or clogging can lead to the engines being starved, leading to a sudden shutdown. However, experts point out that the initial footage of the crash does not show any tell-tale signs of a dual engine failure, considering the aircraft appeared to have a rather usual take-off roll using almost the entirety of the Ahmedabad airport runway, whose length is more than what a 787 would require.
Could it have been bird strikes? Again, the footage available so far does not seem to suggest that. Also, although the Ahmedabad airport has a higher-than-average count of bird hits compared to other airports in the country, it would again be a rarest-of-rare event for a bird hit to disable both engines simultaneously.
For that to happen, it would take flocks of large birds being lodged into both the massive engines of the 787, and damaging them to the extent that they shut down. So far, there is no evidence to suggest such a significant bird strike, neither in the initial footage of the aircraft accident, nor at the airfield in the form of bird carcasses.
Story continues below this ad
The Directorate General of Civil Aviation (DGCA) said that the pilots made a Mayday call, reflecting severe distress with the aircraft, to the Ahmedabad air traffic control moments after taking off, but the reason is not known as there was no contact between the ATC and the aircraft afterwards. The Mayday call itself means that the aircraft experienced a major issue that the pilots immediately discovered. The flight’s lone survivor said that a loud bang was heard before the aircraft plummeted.