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Software update prevents repeated activation of MCAS

Seattle - The software update for the Boeing 737 MAX jets will block repeated activation of the anti-stall system known as MCAS, which is at the center of safety concerns,

Maneuvering Characteristics Augmentation System (MCAS) has been under the focus during the investigations of fatal Lion Air and Ethiopian Airlines Boeing 737 MAX 8 crashes.

According to the sources who are close to the matter said that MCAS will be activated only one time for each case if two AOA (Angle of Attack) sensors agree with each other.

The system won't impose repeated corrections like in the case of Lion Air Flight 610, which pushed the nose of the aircraft down again and again until it crashed into the Java Sea last year in October. It is believed that MCAS played a key role in the second Boeing 737 MAX 8 crash as well that happened on March 10 in Ethiopia.

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In the previous setup, one sensor could be enough to activate the MCAS sensor and it wouldn't allow pilots regain the flight controls.

In the new setup, there will be a warning message labeled “AOA disagree”, indicating the two sensors are generating data that vary by an excessive margin.

“We’ve been working diligently and in close cooperation with the FAA on the software update. We are taking a comprehensive and careful approach to design, develop and test the software that will ultimately lead to certification,” the manufacturer said in a statement.

The update requires FAA approval before it implemented.

Manual or electric trim, which is also used for keeping the nose of the aircraft in the right position remains unchanged as the pilots are able to deactivate the automated trim system through a standard step-by-step checklist procedure.