What is the MCAS system on the Boeing 737 Max 8?

NEW YORK: Flight recorder data recovered from the wreckage of Boeing 737 MAX planes that crashed in Ethiopia and Indonesia shows "clear similarities," Addis Ababa said yesterday as the US maker announced it was finalizing a software update for its under fire anti-stall system. Pressure was mounting meanwhile on the US Federal Aviation Administration, which insisted it had followed standard procedures in certifying the plane model, even as it was reported to have come under investigation by the Department of Transport.

"The 737 MAX certification program followed the FAA's standard certification process," the agency said in an email to AFP. It said its procedures were "well established and have consistently produced safe aircraft designs." But reported similarities between the March 10 crash of an Ethiopian Airlines 737 Max 8, killing all 157 on board, and the Lion Air crash in October of the same model of plane in Indonesia, leaving 189 dead, have raised serious doubts and triggered Boeing's biggest crisis in decades.

The 737 MAX is a relatively new aircraft, having entered service only in May 2017 as Boeing's answer to Airbus's medium-haul A320 Neo. Ethiopian Transport Minister Dagmawit Moges said Sunday that a study of the flight data recorder retrieved from the Ethiopian plane had shown "clear similarities" to that of the Lion Air flight in Indonesia. She said the parallels would be the "subject of further study."

Pilots had complained
As investigators continue their work, preliminary findings in the Lion crash have focused on a possible malfunction of an anti-stall system known as the MCAS (Maneuvering Characteristics Augmentation System). Boeing developed that system, because of the unusually forward placement of the plane's engines, to avoid a stall.
The manufacturer said Sunday it was close to releasing a long-awaited software patch to the system. "While investigators continue to work to establish definitive conclusions, 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," president and CEO Dennis Muilenburg said.

Experts have questioned the FAA's certification process after learning that American pilots had lodged serious complaints about the system. According to a Wall Street Journal report Sunday, the FAA had come under an "unusual inquiry" by the Department of Transport over the issue, and has warned officials to safeguard computer files, according to sources quoted by the paper.

The Journal said the probe would zero in on Seattle-area FAA offices. Boeing airliners are built near Seattle. A Seattle Times report Sunday said the FAA had delegated part of the certification process for the plane-including the MCAS-to Boeing engineers. The original safety analysis provided to the FAA by Boeing contained "several crucial flaws," the newspaper said, adding that the process was carried out hastily as Boeing struggled to catch up with Airbus's more advanced work on the A320 Neo. The report was dated 11 days before the Ethiopian Airlines accident, the newspaper reported.

'All requirements… met'
The FAA refused on Sunday to comment on the newspaper reports, noting the various investigations still under way. In the face of budget cuts, the FAA since 2009 has delegated some certification work to aircraft manufacturers or to outside experts, a procedure known as ODA (Organization Designation Authorization). On Sunday, the agency defended its practice, insisting that the 737 MAX had to pass multiple tests and reviews before being authorized to fly.

It said the aircraft's design was minutely examined, ground and flight tests were conducted, and other civil aviation authorities were consulted to ensure the "airplane complies with FAA standards." A statement provided by Boeing to The Seattle Times said that "the FAA considered the final configuration and operating parameters of MCAS during MAX certification, and concluded that it met all certification and regulatory requirements." It said, without elaborating, that there had been "some significant mischaracterizations" of the certification process.

What is MCAS system
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 yesterday saying it was too early to understand the cause of the Ethiopian Airlines accident. Boeing also said it was working on a software update to the MCAS system which would be deployed across the 737 Max fleet. - Agencies