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| The crash of an Ethiopian Airlines plane has put the spotlight on an anti-stalling system used on the 737 Max 8 aircraft (AFP Photo/Michael TEWELDE) |
Washington (AFP) - Similarities between the Lion Air and Ethiopian Airlines crashes, confirmed by black box data, 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 a week ago 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.
A
malfunction of the system was implicated in the Lion Air accident in Indonesia.
The US
Federal Aviation Administration (FAA) said findings from the crash site and
"newly refined satellite data" warranted "further investigation
of the possibility of a shared cause for the two incidents."
The 737 Max
8 and 9 have been grounded worldwide since the Ethiopia crash, and on Friday
industry sources said Boeing plans to upgrade the MCAS system in the
"coming weeks."
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 flight.
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.
Boeing
was criticized
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 plane 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.
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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