Boeing discloses cockpit alert issue

Boeing Co. acknowledged that a cockpit alert notifying pilots of a sensor malfunction linked to two fatal accidents wasn’t working as represented on every 737 Max.

The plane maker said it didn’t deactivate a warning that was supposed to show conflicting readings between two angle-of-attack vanes. But, Boeing said in a statement Monday, the alert functioned only on jets that had a separate indicator display — available for a fee.

“The disagree alert was intended to be a standard, stand-alone feature on Max airplanes,” it said. “However, the disagree alert was not operable on all airplanes because the feature was not activated as intended.”

The disclosure adds a new mystery about the design of Boeing’s bestselling jet, which has been grounded since shortly after an Ethiopian Airlines 737 Max 8 crashed March 10 — the second deadly Max disaster in five months. Boeing is working to convince airlines and regulators that the Max will be safe once an update is installed to software that played a role in both accidents after being activated by erroneous data from a single sensor.

In both crashes, the jet’s Maneuvering Characteristics Augmentation System software misfired and repeatedly pressed the nose of the planes down until f light crews lost control. The accidents killed a total of 346 people.

Southwest Airlines Co., the largest Max operator, said it first learned from Boeing about the problem with the disagree alert after a 737 Max crash in Indonesia in October. The Max debuted in May 2017.

All information needed to safely operate the plane is in the flight deck and flight-deck display, Boeing said.

At Southwest, pilots aren’t trained to use angle-of-attack information routinely because they don’t use it, said Jon Weaks, the head of the carrier’s aviators union.