FAA orders more design changes to 737 Max

U.S. regulator finds new safety risk unrelated to two fatal crashes

Tests on Boeing Co.’s grounded 737 Max have revealed a new safety risk unrelated to two fatal crashes that led to the grounding of the aircraft, and U.S. regulators are ordering the company to make additional design changes.

The Federal Aviation Administration discovered that data processing by a flight computer on the jetliner could cause the plane to dive in a way that pilots had difficulty recovering from in simulator tests, according to two people familiar with the finding who asked not to be named discussing it.

“The FAA recently found a potential risk that Boeing must mitigate,” the agency said in an emailed statement on Wednesday. The statement didn’t provide any specifics.

While the issue didn’t involve the Maneuvering Characteristics Augmentation System (MCAS) linked to the two accidents since October that killed 346 people, it could produce an uncommanded dive similar to what occurred in the crashes, according to one person, who wasn’t authorized to speak about the matter.

David Learmount, consulting aviation-safety editor at Flight Global and a former Royal Air Force pilot, said details of the new issue are sketchy but it’s possible that it could further delay the Max’s return.

“The implication is that this is different software in a different control computer that’s presenting similar symptoms,” he said. “When you control an aircraft with computers, which we do now, you’ve always got potential for problems.”

Gordon Johndroe, a Boeing spokesman, said the company agreed with the FAA finding and was addressing the issue as well as a broader software redesign that’s been underway for eight months. The 737 Max has been grounded worldwide since March 13, days after the second crash. “The FAA will lift the aircraft’s prohibition order when we deem it is safe to do so,” the FAA said in the statement.

Recent exercises on a Boeing 737 Max simulator showed pilots might have difficulty responding to the newly identified failure, the person said.

Just as MCAS uses a motor to move a small wing at the tail of the plane to lower the nose, the latest issue could prompt that same wing to move without pilot commands.