Aviation regulator outlines fixes that will get the 737 MAX flying again

Software upgrade to deliver less lethally-stubborn automation

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The United States' Federal Aviation Administration (FAA) has revealed the conditions under which it will permit Boeing's beleaguered 737 MAX to resume commercial flights.

The 737 MAX was grounded after two crashes in 2018 and 2019 revealed that the plane had shipped with largely undocumented automation features called the "Maneuvering Characteristics Augmentation System" (MCAS) that could push its nose downwards. In the two accidents MCAS could not be overridden despite receiving erroneous data from an Angle Of Attack (AOA) sensor. When the MCAS pointed the plane down, and kept doing so despite the AOA data being wrong, pilots could not disengage automation.

Those errors cost 346 lives and saw Boeing pay at least $19bn in compensation to families of the deceased, payments to airline customers and lost revenue.

Chinese and US aviation regulators grounded the planes weeks after the 2019 accident. They've been grounded ever since pending analysis of the crash's cause and re-certification of the plane.

On Monday the FAA revealed its conditions for the plane to be returned to the skies in a new Airworthiness directive and review of the aircraft [PDFs] that detail the necessary changes before the regulator will permit the MAX to again carry paying passengers.

One of the required changes is for the MCAS to activate only after receiving data from two AOA sensors, rather than the one engaged in the past.

A second requirement will mean the MCAS can only engage once after receiving AOA data, rather than cause repeated downwards pitches. Pilots will therefore be able to fly manually rather than have to figure out how to disengage MCAS.

The FAA also wants a software update so that crew are alerted if two AOA sensors disagree and changes to the flight deck to reflect the fact that it will no longer be appropriate to report that the sensors are inoperable.

Changes to horizontal stabilizer trim wire routing installations are also required, to give pilots better control.

A host of changes to flight manuals and operating procedures are also required.

Boeing has already conducted 737 MAX test flights with some of the suggested modifications and suggested the type could be back in the air by the end of 2020.

If the company meets that deadline, the plane may find eager customers as it looks likely the aviation industry will have low passenger demand for the next couple of years. The 737 MAX offers low running costs and can handle missions ranging from short commuter hops to transatlantic treks, making it capable of replacing some wide-body alternatives. ®

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