Boeing finds 737 MAX flight software issue, FAA opens review

Boeing has found a software problem in the flight management computers on some 737 MAX aircraft, the manufacturer and the U.S. Federal Aviation Administration said. The fault can cut off automated vertical navigation during one specific missed-approach sequence.

It starts with a precision approach flown under autopilot. If the crew goes around and the pre-programmed route is altered, the vertical navigation function, known as VNAV, may drop out. Boeing says the autopilot itself does not necessarily disconnect, and the aircraft reverts to a simpler mode of automated pitch control.

VNAV handles the vertical path for the 737 MAX 7 and MAX 10, including altitude constraints entered into the flight management system. When it is unavailable in the affected sequence, pilots must take extra steps to manage the aircraft on the approach that follows. The concern is crew workload during a busy phase of flight.

The FAA said it is working with Boeing and airlines to assess the issue and will convene a Corrective Action Review Board. The agency said it will act immediately if the review turns up a safety concern.

Boeing has told 737 operators about the problem. Its engineers are developing a software update meant to fix it permanently. The disclosure comes as the company works toward certification of the long-delayed 737 MAX 10 and prepares the 737 MAX 7 for commercial service.