Ethiopian Airlines crash: What is the MCAS system on the Boeing 737 Max 8?

The crash of an Ethiopian Airlines plane has put the spotlight on an anti-stalling system used on the 737 Max 8 aircraft
The crash of an Ethiopian Airlines plane has put the spotlight on an anti-stalling system used on the 737 Max 8 aircraft

Similarities between the Lion Air and Ethiopian Airlines crashes have focused attention on an anti-stalling system used in the new Boeing 737 Max 8 aircraft.

The Maneuvering Characteristics Augmentation System (MCAS) is an automated safety feature on the 737 Max 8 designed to prevent the plane from entering into a stall, or losing lift.

Both the Lion Air jet, which crashed in October, killing 189 people, and the Ethiopian Airlines aircraft, which went down on Sunday, leaving 157 people dead, were fitted with the system.

Both planes experienced similarly erratic steep climbs and descents and fluctuating airspeeds before crashing shortly after takeoff.

The US Federal Aviation Administration (FAA), while noting the similarities between the Lion Air and Ethiopian Airlines accidents, stressed that it was too early to draw any conclusions.

MCAS was introduced by Boeing on the 737 Max 8 because its heavier, more fuel-efficient engines changed the aerodynamic qualities of the workhorse aircraft and can cause the plane's nose to pitch up in certain conditions during manual .

Angle of attack sensors on the aircraft tell the MCAS to automatically point the nose of the plane down if it is in danger of going into a stall.

This is done through horizontal stabilizers on the plane's tail which are activated by the aircraft's flight control computer.

According to Boeing, MCAS does not control the plane during normal flight but "improves the behavior of the airplane" during "non-normal" situations.

These could be steep turns or after takeoff when a plane is climbing with flaps up at speeds that are close to stall speed.

According to the flight data recorder, the pilots of Lion Air Flight 610 struggled to control the aircraft as the automated MCAS system repeatedly pushed the plane's nose down following takeoff.

The pilots of the Ethiopian Airlines plane reported similar difficulty before the aircraft plunged into the ground shortly after takeoff.

Software updates

A preliminary report on the Lion Air Flight 610 accident blamed it in part on a faulty angle of attack sensor that triggered the MCAS system and automatically forced the plane's nose down.

Pilots flying the same Lion Air the previous day had managed to override the automated flight control system.

Boeing came in for some criticism after the Lion Air crash for allegedly failing to adequately inform 737 pilots about the functioning of MCAS or provide training about the system.

Following the Lion Air crash, Boeing issued a bulletin to airlines operating the 737 Max 8 advising pilots how to override the MCAS system.

The US aircraft manufacturer issued a statement on Monday saying it was too early to understand the cause of the Ethiopian Airlines accident.

Boeing also said it was working on software updates to the MCAS system which would be deployed across the 737 Max fleet.

It said procedures already exist to "safely handle the unlikely event of erroneous data coming from an angle of attack (AOA) sensor," the suspected cause of the Lion Air crash.

"The pilot will always be able to override the flight control law (MCAS) using electric trim or manual trim," the aircraft manufacturer said.

A growing list of countries have grounded their 737 Max after the two deadly crashes in just five months.

Boeing has described the Max series as its fastest-selling family of planes, with more than 5,000 orders placed to date from about 100 customers.

But not since the 1970s—when the McDonnell Douglas DC-10 suffered successive fatal incidents—has a new model been involved in two deadly accidents in such a short period.


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Citation: Ethiopian Airlines crash: What is the MCAS system on the Boeing 737 Max 8? (2019, March 12) retrieved 24 April 2019 from https://phys.org/news/2019-03-ethiopian-airlines-mcas-boeing-max.html
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User comments

Mar 12, 2019
The wreckage was barely even ambient temperature and already people are ascribing this to the causes of the previous accident.

I know how it looks. But until the investigators start piecing together what happened from the flight data recorder and the cockpit voice recorder, we won't know for sure.

Mar 12, 2019
Maybe they should check the safety records and not fly aircraft that have problems.

Just sayin'.

Mar 12, 2019
Maybe they should check the safety records and not fly aircraft that have problems.

Just sayin'.

DS, these are the newest planes in their class being sold by Boeing. The 737 is about the same as the Airbus A380 and compete for both sales and routes.
I guess they should have stayed with the A380...

Mar 12, 2019
Maybe they should check the safety records and not fly aircraft that have problems.

Just sayin'.

Da Schitts, just brayin.
Maybe you should check some facts and not soil the forum with the shite that's between your ears.

Mar 13, 2019
It's not the planes that have too much complexity, it is the overly bureaucratic and over-employed corporate body behind them that is at fault. I have a bubble-level app that carpenters can use that I downloaded to my smart phone (Xperia XA1), and it works flawlessly. Something simple like that could easily be adapted to an autonomous plane leveling system and I am sure that plenty of thinkers at Boeing are completely aware of this, but well, you know, you work with what you have to work with, which is a bunch of greedy corporate hounds, who never study a design schematic, all stepping over each other to get noticed while trying to run the show their way. That's the problem with corporate America right now. When the body of politicians and congress people that supposedly run the country is dysfunctional, it just trickles down. I mean, it was the absolute worst Rose Bowl parade I ever saw on TV!

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