An Air Canada Boeing 737 MAX 8 jet approaches Toronto Pearson International Airport on March 13, 2019, before a worldwide grounding took effect (Cole Burston)

Chicago (AFP) – Boeing is finalizing a software update and pilot training linked to the MCAS anti-stalling feature, under scrutiny after two 737 Max 8 crashes, the company’s CEO said on Sunday.

“Boeing is finalizing its development of a previously-announced software update and pilot training revision that will address the MCAS flight control law’s behavior in response to erroneous sensor inputs,” the US-based aircraft manufacturer’s president and CEO, Dennis Muilenburg, said in a statement.

On Friday two anonymous industry sources told AFP the upgrade should be ready in about 10 days. 

Muilenburg’s announcement came after Ethiopia’s transport minister earlier Sunday said black box data recovered from the Ethiopian Airlines plane that crashed last week shows “clear similarities” with last year’s Lion Air accident in Indonesia — which involved the same Max 8 type of aircraft.

Industry sources caution that the MCAS upgrade does not point to a cause of the Ethiopian crash, something Muilenburg’s statement also indicated.

He said the MCAS modification is taking place “while investigators continue to work to establish definitive conclusions.”

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.

The two 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.

The 737 Max 8 and 9 have been grounded worldwide since the Ethiopia crash.

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.

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.

A preliminary report on the Lion Air 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.

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

After that crash, the company issued a bulletin to airlines operating the 737 Max 8 advising pilots how to override the MCAS system, and said it was working on software updates.

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