On September 24, 2020, the U.S. Federal Aviation Administration (FAA) issued a special bulletin warning Boeing 787 Dreamliner operators of potential for autopilot flight director system (AFDS) failure.
The problem concerns Boeing 787-8, -9 and -10 models. According to the bulletin, the FAA received numerous reports that aircraft AFDS failed to capture the localizer (LOC) during an approach at large angles (40 degrees or more) from the runway and beam centerline.
“Flight data has confirmed that during these events, the AFDS guidance partially reduced the intercept angle, but the airplanes continued through the localizer at a heading not aligned with the runway centerline,” the bulletin states. Meanwhile, the system did not notify of the failure to capture LOC and aircraft proceeded to approach runways at 20 to 30 degree angles.
According to the FAA, Boeing’s Flight Crew Operations Manual Bulletin from December 18, 2019 addresses the issue and provides information on how to correct it, while the company and its supplier are working on a software update to fix the erroneous behavior of the autopilot.
In the meantime, the bulletin advises all operators of the affected 787 models to notify flight crews to follow corrections outlined in Boeing’s bulletin.
This is yet another problem in a string of bad luck Boeing 787 Dreamliner faced in recent weeks. In late August 2020, a number of 787s were grounded due to the risk of structural failure. Another manufacturing flaw was discovered less than two weeks later; it concerned aircraft vertical stabilizers. Yet another safety concern, related to vertical tail fin faces, was raised a few days later.
