Wetin fit don cause Air India plane to crash in 30 seconds?

Wetin exactly happun to Flight AI171 between Ahmedabad and London Gatwick on Thursday afternoon go only dey known afta a detailed investigation, but di moments afta take-off na di most challenging for aviation.

Experts from US and UK go join Indian investigators in di coming days, as authorities attempt to establish wetin cause di Boeing 787-8 Dreamliner to crash shortly afta e take-off just 1.5km (0.9 miles) from di runway for Sardar Vallabhbhai Patel International Airport.

Dis mark di first time wey 787-8 Dreamliner go suffer deadly crash since e enta commercial service for 2011. Thursday disaster kill 241 pipo onboard and more pipo wey dey ground.

BBC speak to aviation experts as well as pilots wey dey based in India - some of dem speak on di condition say we no go mention dia names – dem dey regularly fly 787-8s out of India international airports to find out di factors wey fit don cause di plane to slam into residential buildings for di heart of Ahmedabad just moments into di flight.

Struggle to gain altitude

Captain Sumeet Sabharwal and im co-pilot Clive Kundar na dem fly di 787-8 Dreamliner. Two of dem dey highly experienced. Dem get more dan 9,000 combined flying hours. Oga Sabharwal get ova 22-years experience as commercial airline pilot.

Di plane bin carry 242 pipo as e taxi along di runway for Ahmedabad International Airport on Thursday afternoon. Di jet take off at 13:39 local time (08:09 GMT), na wetin di operator Air India tok.

India Home Affairs Minister Amit Shah say di plane bin dey carry 100 tonnes of fuel - practically a full load - as e bin dey climb out of Ahmedabad.

Almost immediately afta take-off, di cockpit drop mayday call, India aviation regulator tok. Di aircraft no give any response afta dat. E no dey clear why dem drop di mayday call, but di flight only survivor tell Indian media say im bin hear a loud bang as di plane bin dey struggle to gain altitude.

Authentic footage wey BBC Verify see show as di plane dey fly low for place wey be like residential neighbourhood. Di final transmitted data show say di plane bin reach a height of 625ft (190m). E kon begin descend bifor e pass trees and buildings, and den explode for front.

"Di pilot no get time to react if di plane loose both engines," one pilot tok. CCTV footage wey BBC Verify bin show say di plane bin dey for air for 30 seconds.

Di plane bin crash for one residential area. Foto show housing blocks wey dey heavily damaged for one densely built area wia hospitals and official buildings dey.

Speculation of 'veri rare' double engine failure

E dey almost impossible to really say wetin cause di disaster based on videos of di plane brief flight.

In di coming days, dem go carry out ogbonge investigation wey dem go use di plane black box – wey dey record flight data - and dem go begin examine di parts of di plane. But videos show as di plane dey struggle to lift off from ground, sake of lack of thrust or power.

One of di causes wey some experts dey speculate na possibility of extremely rare double engine failure. Kwesions wey sabi pipo dey ask na if di plane use im Ram Air Turbine (RAT). Dis na emergency back-up turbine wey dey kicks in wen di main engines fail to generate power for essential systems.

Double engine failures no dey common. Di most notable example na di 2009 "Miracle on the Hudson", wen one US Airways Airbus A320 lose both engines to bird strike moments afta take-off from New York LaGuardia Airport, but glide to safety.

One senior pilot tell BBC say dual engine failure fit also result from fuel contamination or clogging. Aircraft engines dey rely on precise fuel metering system - if dat system block, e fit lead to fuel starvation and engine shutdown.

Marco Chan, wey be ex-pilot, tell BBC Verify say evidence no dey to suggest say na double engine failure based on di available footage.

Mohan Ranganathan, wey be aviation expert, tell BBC say double engine failure na "veri, veri rare incident".

Engine manufacturer GE Aerospace say dem dey send dia team to India to help wit di investigation, while Boeing say dem dey offer dia full support to di airline.

Bird strikes

Anoda possibility wey experts for India raise na bird strike.

E dey happun wen plane collide wit bird and e dey extremely dangerous for aircraft. For serious cases, engines fit lose power if dem suck in di bird, as e bin happun for South Korea Jeju Air disaster wey bin kill 179 pipo last year.

Experts and pilots wey dey familiar wit Ahmedabad airport tell BBC say e dey "notorious for birds".

"Dem always dey around," na so Oga Ranganathan tok, exactly wetin at least three Indian pilots wey bin don fly in and out of di airport tell BBC .

Gujarat state, wia Ahmedabad dey located, bin report 462 bird strike incidents ova five years, most of dem happun for Ahmedabad airport, according to Civil Aviation Ministry data wey dem report for Parliament for December 2023.

One Times of India report for September 2023 bin cite Airport Authority data say 38 bird strikes na im happun from 2022–23 for Ahmedabad, a 35% rise ova previous 12 months.

For di 2009 case, a flock of seagulls bin dey ingested at 2,700ft – wey dey more dan four times higher pass di Air India flight. For dis case di Indian pilots bin neither get di altitude nor di time to manoeuvre.

However, one senior pilot say e dey rare for bird hit to dey catastrophic "unless e affect both engines".

Di plane flaps fit contribute to di crash?

Three experts wey bin speak to BBC Verify bin suggest say di disaster fit don happun sake of say di aircraft flaps no extend during take-off - though oda pilots and analysts don challenge dis idea.

Flaps dey play a vital role during take-off - e dey help aircraft to generate maximum lift at lower speeds.

If dem no properly extend, fully loaded jet - wey carry passengers, heavy fuel for a long flight, and wey dey battle hot conditions - go struggle to lift off.

For Ahmedabad, wia di temperatures dey near 40°C (104F) on Thursday, di thinner air fit demand higher flap settings and greater engine thrust, one pilot tell BBC. For conditions like dat, even small configuration error fit get deadly consequences.

CCTV footage wey bin come out late on Thursday afternoon show as di plane take off from Ahmedabad, and as e struggle to achieve altitude, and den slowly e descend bifor e crash.

But a take-off roll wit retracted flaps go trigger warnings from di 787 take-off Configuration Warning System, wey go alert di flight crew to unsafe configuration, according to one pilot wey BBC bin speak to.

Ex-pilot Chan tell BBC Verify say di footage wey don come out so far dey too distorted to establish for sure whether di flaps bin dey extended, but say dat kain error go dey "highly unusual".

"Di flaps na pilots dey set am demsefs, bifor take off, and dem get several checklists and procedures to verify di setting," Oga Chan tok. "Dat go point to potential human error if flaps no dey set correctly."

Na Jake Horton do additional reporting