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Boeing's software update for the Max 8 aircraft may not be enough to satisfy critics

Software updates planned for Boeing Inc.’s (BA) troubled 737 Max 8 aircraft, grounded worldwide after two deadly crashes, may not be enough to satisfy critics.

All Max 8 planes will be modified to feed additional data into a system designed for the 737 Max called MCAS, or Maneuvering Characteristics Augmentation System, known to have been involved in the Lion Air and Ethiopian Airlines crashes that killed all passengers and crew on board.

“The software update that we’re making going forward includes dual sensor feed into that system,” Boeing CEO Dennis Muilenburg said during the company’s annual shareholder meeting on April 29.

‘This plane should never take to the air again’

Arthur Rosenberg, a plaintiffs attorney and pilot, described the dual software update as insufficient. Rosenberg has been contacted by families of crash victims considering legal representation.

“If that’s the case, this plane should never take to the air again,” he said. “You really need three AOA sensors, with two in agreement to provide data to MCAS. If you only have two, and the data is telling pilots that one doesn’t agree, you’re still left with a plane that has inherent unsafe flight conditions, which cause a nose-up tendency.”

Passengers may share Rosenberg’s trepidation. On Tuesday, Barclays downgraded Boeing, noting that it surveyed more than 1,700 flyers and found that nearly half would not fly a Max for a year or more. If given a choice between a Max and another plane on identical flights, 52% would choose the other plane.

Protester Tarek Milleron holds the photographs of victims in the Ethiopian Airlines Flight 302 plane crash, outside Boeing's annual shareholders meeting at the Field Museum in Chicago on Monday, April 29, 2019 (AP Photo/Jim Young)

Shortly after takeoff from Jakarta, Indonesia on October 29, 2018, Lion Air Flight 610 crashed into the Java Sea killing 189 people. Subsequently, on March 10 of this year, Ethiopian Airlines Flight 302 crashed shortly after takeoff from Addis Ababa, Ethiopia, killing 157. In both cases, errant sensor data is suspected to have engaged MCAS, which automatically tilts the horizontal stabilizer and in turn pushes the nose down to prevent the plane from stalling in the air.

The originally-FAA-certified Max 8s relied on a single angle of attack sensor (AOA), a titanium vane that points into the wind to measure the angle between the nose and the relative wind from the plane’s forward movement. The measurement is to gauge whether the wings have enough lift. The data is then communicated to MCAS.

‘This airplane can fly without MCAS’

MCAS was designed to make the 737 Max handle similar to earlier 737 models. Its engines, more fuel-efficient and powerful than in prior models, were raised and moved forward on the fuselage, causing it to fly with a “nose up” tendency. To compensate, Boeing installed MCAS, which automatically adjusted the nose down when data from the AOA sensor deemed it necessary.

The flight control system in Boeing’s modified planes compares inputs from both AOA sensors, and deactivates MCAS if the sensors meet a threshold level of disagreement, plus alerts pilots using an indicator on the flight deck display.

“This airplane can fly without MCAS,” Chris Clearfield, a licensed commercial pilot and co-author of “Meltdown,” told Yahoo Finance. Clearfield said pilots need to know how and when to deactivate the system. The nose-up tendency, he said, can be safely managed, even in scenarios where two sensors disagree and MCAS is disabled.

“This is one of those cases where it might be enough just to turn off this system, to turn it back into a slightly less sophisticated airplane if the systems aren't working, and the pilots can then take over and be pilots,” he said.

Roger Phillips, Communications Committee Vice Chairman for Air Line Pilots Association — a United Airlines pilots union — told Yahoo Finance that added system redundancies are welcome, though he did not say whether the Association had a position on the number of AOA sensors recommended for the modified planes.

“We are working closely with United (UAL) and Boeing to develop training that ensures our pilots have full confidence in the changes Boeing has made to the 737 Max. Pilots need to know the full details of any design modifications being put into place, and the lessons learned from these two tragic accidents must be fully incorporated into our training programs so this never happens again,” Phillips said.

Dennis Tajer, a spokesman for the American Airlines pilots union, reportedly told The New York Times that he was concerned Boeing lacked full understanding of how the Max 8 worked, after the company on Sunday revealed an additional issue involving MCAS.

In a statement, Boeing said certain Max 8 planes were delivered to customers with cockpit display software that didn’t meet Boeing’s requirements. Two types of AOA sensor data, the company said, were linked in such a way that disabled a disagree alert in planes whose customers did not also purchase an AOA indicator. Engineers identified the software discrepancy as early as mid-August 2017, more than a year before the Lion Air crash, though Boeing said its senior leadership was not aware of the issue until after the crash. Boeing has maintained that the Max 8 could fly safely, regardless of the software issue.

“Neither the angle of attack indicator nor the AOA Disagree alert are necessary for the safe operation of the airplane,” the company said.

Yahoo Finance contacted Boeing to ask whether it identified the AOA software discrepancy during test flights of the Max 8 and did not receive a response. The company said the software update itself will take approximately two hours. However, because all Max 8 aircraft are currently grounded, there are logistical matters associated with the upgrade.

Alexis Keenan is a New York-based reporter for Yahoo Finance. She previously worked for CNN and is a former litigation attorney. Follow on Twitter @alexiskweed.