The Air India tragedy that saw a Boeing 787 Dreamliner plummet into a residential neighborhood on Thursday has prompted a flurry of speculation as to its cause.
Carrying 242 passengers including 53 Brits, the jet crashed shortly after take off from Sardar Vallabhbhai Patel International Airport in Ahmedabad, Gujarat state. There are thought to be few survivors.
The plane had been en route to London Gatwick, having taken off shortly after 1pm local time, in fair flying conditions.
It reached no more than 625 feet in the air – just over 425 above the ground the airport stood on – according to tracking data, before its transponder signal was lost seconds later.
As it came down, the plane struck a medical college, its landing gear embedded in the building as staff ate lunch – before the fuselage came apart in a furious fireball.
Amid intense speculation as to the cause, experts have unpacked the leading theories as to what brought the plane down. Records suggest the jet had been in service for 11 years.
Among the key suggestions are pilot error – whether in the configuration of the plane’s wings, or the amount of runway used – or a mechanical failure, possibly caused by a bird strike.
Searches continue for the black boxes pivotal to the investigation.
Was there a pilot error – before or after takeoff?
The plane was under the command of captain Summeet Sabharwal, who had 8,200 hours of experience.
Bernard Lavelle, principal aviation consultant at BL Aviation Consulting, told that early indications suggested a pilot fault was unlikely to be to blame.
While most planes ‘pretty much fly themselves’ in the air, he said, pilots are still wholly responsible for take-off and landing.
‘The two most dangerous, relatively speaking, phases of any flight are take off and landing,’ he said.
‘There are generally few issues when the aircraft is in the air – but take-off and landing are when something could go wrong and the only time the pilot is (fully in control of) the aircraft.’
He added: ‘The two most common reasons for plane crashes are pilot errors or a mechanical fault.
‘The fact there was an SOS message probably doesn’t indicate pilot error.’
However, Marco Chan, a former pilot turned senior lecturer in aviation at Buckinghamshire New University, says there may be another element of pilot error to consider – whether the runway was long enough.
Records suggest the Boeing Dreamliner needs 2820m (1.75miles) of runway to make a proper takeoff.
But unverified Flightradar24 data suggests the plane taxied onto the runway and took off from the intersection with the taxiway with only 1900 metres (1.18miles) of tarmac to use for takeoff.
Mr Chan said: ‘1900 metres would be inadequate for a 787, which could be an issue(to investigate).
‘The onboard computer would know there is not enough runway and not give you full power.’ However, Mr Chan added that the computer can be overridden.
Did the engines or other systems fail?
A leading theory among experts is that the Dreamliner experienced mechanical failure shortly after take-off.
A ‘mayday’ call was sent to the air traffic controllers from the cockpit shortly after takeoff, suggesting the pilots knew something was wrong.
Mr Lavelle said the indications pointed to engine failure – though the black box recordings would reveal all.
He said: ‘Something has gone wrong in the cockpit. The aircraft is at maximum thrust at this point. If they weren’t able to reach altitude, it might indicate an issue with the engine. They weren’t getting the thrust they thought they should be.’
Former pilot Saurabh Bhatnagar told NDTV the plane appeared to make a ‘controlled’ descent as it came to crash-land.
‘Immediately after takeoff the landing gear was still (out) – so that means thereafter the aircraft coming down in a sort of controlled fashion. It was a distress situation,’ he said.
Records suggests a Boeing 787 Dreamliner takes off at around 165 knots (190mph) before rapidly accelerating to 190 knots (218mph) as it climbs into the sky.
Flightradar data suggests the plane was only at 174 knots as it reached 625ft after takeoff – before descending into the Meghaninagar residential area.
On pilots’ forums, aviation experts said that they could hear a sound suggesting the plane’s Ram Air Turbine (RAT), an emergency wind turbine, had been deployed shortly before the crash.
This spins up to generate electricity in the event of full electrical or hydraulic failure and can power critical systems like flight controls and instrumentation.
Marcus Chan of BNU said there was a small possibility of engines failing due to computer management software issues, or fuel pump issues. However, he added that it was too early to say whether either were a cause.
Did a bird strike bring down the plane?
Ex-pilot Captain Bhatnagar said the engines may have failed after a bird strike.
This would be similar to the Jeju Air crash at Muan International Airport near Muan South Korea, last December.
That incident saw a bird strike the plane as it approached the runway to land.
The landing gear failed to deploy – possibly as a result of the bird strike – and the plane belly flopped onto the runway and crashed into a concrete wall, killing everyone on board save for two crew.
‘From the footage I have seen, it looks like prima facie the case of multiple bird hits, wherein both engines have lost power,’ Cpn Bhatnagar said.
‘The takeoff was perfect and just I believe short of taking the gear up the aircraft started descending, which only happens if the engine loses power or the aircraft stops delivering the lift.’
Lt Col John R Davidson, a former US Air Force Pilot and commercial aviation safety consultant, said: ‘There are a number of possible scenarios: thrust or engine performance issues, excessive aircraft weight, poor trim or flap configuration, or a more critical failure that affected the aircraft’s ability to climb.
‘Weather, windshear or even bird strike can’t be ruled out either at this early stage.’
BNU’s Marco Chan says the theory of a bird streak was not one he was convinced by – as footage was missing the telltale smoke from the engine that might suggest a foreign object.
‘Comparing the footage available, there doesn’t appear to be a puff of smoke from the engine – I would say the bird strike theory could be ruled out,’ he said.
What about the flaps and landing gear?
Speculation is rife that the plane was not correctly set up for takeoff – having not deployed its ‘flaps’, segments of the wing that are used to assist with lift.
Marco Chan, of Buckinghamshire New University, said the setting of the flaps was completely down to the pilot – with more flap increasing the surface area of the wing and helping with lift at lower speeds.
But if the plane is not travelling quickly enough, the wrong flap setting could actually work in reverse – and stall the plane. Footage appears to show the jet descending with its nose in the air, as if still trying to climb.
‘Looking at the footage there are several experts suggesting the flaps aren’t configured properly – it is hard to tell, but it could be a possibility,’ he said.
‘Every take-off is slightly different and you may have a different flap setting. It may not have been set properly. If that is the case, that is definitely human error. But we do have other procedures to ensure that doesn’t happen.’
Alastair Rosenschen, a former British Airways pilot and aviation analyst, told Sky News that flaps give jets as much lift as possible while they are still speeding up.
Mr Rosenschen said: ‘That’s what you need for take-off. As the aircraft accelerates, you can then start to retract the flaps.’
He also suggested that the landing gear, which appeared to be deployed as the jet came down, would have been retracted as soon as the jet has a ‘positive rate of climb’ – i.e. is ascending rapidly.
US regulator the FAA appears to suggest in a document that this is normally around 500 feet in the air. The Air India jet was last ‘pinged’ at 625 feet before it crashed.
‘The gear should not be down and effective as soon as you have got a positive rate of climb, after take-off,’ Mr Rosenschen added.
‘If the gear was still down, then that would suggest that something is untoward.’
Bernard Lavelle noted that, if there was a critical issue in the cockpit, the landing gear would ‘probably not be something they even thought about’ in the seconds before the plane came crashing down.
Did something else fail?
Bernard Lavelle notes that Boeing 787 Dreamliners have been in use for at least 12 years, with no ‘hull losses’ – the complete write-off of an airplane – until today.
Early Dreamliners had issues with lithium-ion batteries, fuel leaks and fires, while one suffered a collapse in its front landing gear at Heathrow in June 2021.
However, he maintains that the plane had a ‘pretty good safety record’.
‘It’s used all around the world. I’ve been in them myself
Could there have been a security failure?
The security situation between India and Pakistan has been escalating in recent months over their contested ownership of the Kashmir region, which joined India over Pakistan in the 1947 partition.
Both now control areas of the contested region, but each maintain their claim to it in its entirety.
Tensions have been brewing India and Pakistan in recent months over the issue after militants killed 26 people in an attack near Pahalgam, in the Indian-administered region of Kashmir.
India has responded with missle strikes on targets in Pakistan and its region of Kashmir.
Aviation security consultation Julian Bray said: ‘We cannot rule out security issues. But this is all speculation on my part.’
He added: ‘What I am worried about is if an incident has happened while it was taking off we have to look at the security side of things and work out where there was some evil intent behind this.
‘Basically, the aircraft these days sort of fly themselves so there shouldn’t have been a problem in taking off, especially with a Dreamliner. It has a good track record. We really need more detail.’
Mr Lavelle said security issues could ‘not be ruled out’ due to the ‘political situation between Pakistan and India’ – but added that this was far down his list of reasons for the plane coming down.
What next?
Investigators are hurriedly searching the wreckage for survivors, as well as for the black boxes – the key data loggers recording everything on the plane.
‘Getting the black box records – one has the audio and the other the telemetry, how the plane was performing – is the key thing now,’ Mr Lavelle said.