The Federal Aviation Administration (FAA) issued a Special Airworthiness Information Bulletin for operators of Boeing’s Dreamliner on Thursday. The bulletin applies to the three Dreamliner models, the 787-8, 787-9, and 787-10. The FAA indicates the possibility of the autopilot flight director system failing to intercept the localizer on an ILS approach.

The FAA said:

“…the autopilot flight director system was not providing proper guidance to capture the localizer when intercepting the localizer at large angles (40 degrees or more) from the runway and beam centerline.”

Boeing 787 Dreamliner INCIDENT

On April 21, Air Canada Boeing 787-9 Dreamliner, approaching to Hong kong had been cleared for an ILS approach to runway 25L.

The crew then contacted air traffic control after reaching waypoint LOTUS, 15NM from runway threshold and reported they have established the ILS.

After controllers tells the crew to switch to the Hong Kong tower frequency, they observed the aircraft “overshooting the localiser” of 25L and descending to 3,900ft and resulted that they are below the MINIMUM SAFE ALTITUDE of 4,300ft.

Controllers contacted the crew to warn of terrain and the pilots corrected the flightpath to re-intercept the ILS. The crew reported receiving a “false capture” of the ILS, says the safety board, which adds that the pilots had visual contact with both the terrain and the airport at the time.

The statement issued by the FAA couple a days ago provides the failure of the issue with the 787 ILS. According to the FAA, guidance from the autopilot flight director system partially reduced the intercept angle. However the aircraft continued establishing the localizer at a heading not aligned with the runway’s centerline and it didn’t indicates any failure.

The autopilot flight director system provides guidance to descend to the glideslope and with the problem occurred in the 787 this will lead the aircraft continued to deviate from the runway centerline and descend on an incorrect heading.

FAA said that Boeing is still working and trying to do their best on updating or fixing the software problem with the localizer during ILS approach.