Another Boeing 737 has crashed killing all on board — what went wrong?

A plane in flight

Ethiopian Airlines flight ET302 crashed on 10 March

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Aircraft safety is in the spotlight after a fatal plane crash. What went wrong?

What has happened?
A Boeing 737 Max 8, operated by Ethiopian Airlines, crashed on Sunday shortly after take-off from Addis Ababa, killing all 157 people on board. Details are still scarce and an investigation will take place in the coming days and weeks. The plane’s black box was recovered this morning. An Ethiopian Airlines spokesperson said the company has decided to ground its fleet of Boeing 737 Max 8 aircraft “as an extra safety precaution”.

Is this the first time the Boeing 737 Max 8 has been involved in a crash?
It isn’t. Lion Air flight 610 used the same type of plane and crashed 12 minutes after take-off from Jakarta in October 2018, killing 189 people on board.

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The 737 Max 8 involved in Sunday’s crash was only registered in November, and is one of 350 such planes currently in operation. The order book for the plane – the latest version of Boeing’s classic 737 – is long, with more than 5000 ordered since 2017.

Is the 737 Max 8 dangerous?
In November, following the Lion Air crash, Boeing issued a warning to airlines that the Max 8 flight monitoring system can throw up incorrect readings that cause the autopilot to dive rapidly, thinking that the plane is in a mid-air stall. That Boeing alert, and a subsequent one by the US Federal Aviation Authority (FAA) indicated that they believed the crash could have been caused by a faulty angle-of-attack sensor, which measures how air flows over the wings.

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The angle-of-attack sensor was replaced on Lion Air flight 610 the day before the accident because it had failed. “It was certified as safe by the appropriate regulatory authorities,” says Graham Braithwaite at Cranfield University, UK. “The investigators will need to ensure nothing was missed in that process.”

Boeing 737-600s have an accident rate of fewer than one in every 5 million departures. Back-of-the-envelope analysis by David Gleave at Loughborough University, UK, shows the accident rate of a 737 Max, which has a more efficient engine and wing design than its predecessors, is now six or seven times that – although it is still extremely low.

Do we know what went wrong?
No. While people are pointing to the similar circumstances around the Ethiopian and Lion Air crashes – both happened shortly after take-off, with both planes seemingly unable to ascend properly – it is still too early to tell. “There could be a correlation but no common causation,” says Gleave.

Are there more plane crashes now or are we just noticing them more?
Accident rates are still very low in commercial aviation and the number of aircraft in the air is increasing. A 2013 study by researchers at Northwestern University in Illinois found that 0.07 people die for every billion miles travelled on planes, compared with 7.3 people on cars, and 0.43 people on trains. Recent plane accidents will hardly dent these statistics. “The 737 Max accidents are high profile partly because it’s a new version and partly because both were total losses,” says Braithwaite.

What happens next?
Boeing, the FAA and their European counterparts the European Union Aviation Safety Agency (EASA) will be working together to decide if grounding 737 Max 8s is necessary. “Boeing will be involved, but the decision will be taken independently from them,” says Braithwaite.

China’s aviation authority has already made a move to ground the aircraft.

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source: newscientist.com