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Boeing Needs Up to Three Months to Fix Latest 737 Max Problem

The FAA discovered that when the tail panel that adjusts the nose up and down moves on its ownーa failure known as a trim runawayーthe flight computer could impede a pilot’s response.

Boeing Co. could take as long as three months to fix the latest software glitch on its 737 Max, discovered when a U.S. government pilot running simulator tests experienced a lag in an emergency response because a computer chip was overwhelmed with data, people familiar with the matter said.

The discovery is what led to Wednesday’s announcement by the Federal Aviation Administration that it had detected a new safety issue on the plane, said a person familiar with the issue. Boeing’s best-selling jet has been grounded since March after the model crashed twice in a five-month span.

The planemaker said in a statement that it plans to update the plane’s software to address the issue. However, the FAA isn’t sure yet whether that will address the problem or whether a more complex and expensive hardware fix is required, said the person, who wasn’t authorized to discuss the matter and asked not to be identified.

Estimates for how long it will take to address the latest issue on the plane range from a few weeks to three months, the person said Thursday. Another person familiar with the matter said it could take two to three months, but not longer.

The FAA discovered that when the tail panel that adjusts the nose up and down moves on its ownーa failure known as a trim runawayーthe flight computer could impede a pilot’s response.

One of the first steps in such a failure is to use thumb switches on the control column to counter the movement. A pilot attempted that maneuver during the recent simulator test and found that because of the computer issue, the manual electric trim switches didn’t immediately respond.

That could lead the plane to enter a dive that would be difficult to recover from. The FAA pilot categorized it as catastrophic, which means it could result in a crash.

The problem occurred during a scenario that commercial pilots are highly unlikely to encounter, and doesn’t involve the flight-control software linked to the two 737 Max crashes, according to one of the people. However, the resulting diving motion created by the runaway trim was similar to the problem faced by the Lion Air and Ethiopian Airlines pilots on the flights that went down.

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

By Alan Levin and Julie Johnsson

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