Created Friday, Aug 11th 2023 15:49Z, last updated Friday, Aug 11th 2023 15:49Z
A Virgin Atlantic Airways Boeing 787-9, registration G-VBOW performing flight VS-206 from London Heathrow,EN (UK) to Hong Kong (China) with 235 passengers and 14 crew, was on an ILS approach to runway 25R at about 15:49L (07:49Z) with the autopilot engaged when veered to the right off the localizer and descended below minimum safe sector altitude. The crew disconnected the autoflight system, assumed manual control of the aircraft, re-established the aircraft on the localizer about 12nm before the runway threshold and landed safely.
On Mar 6th 2020 Hong Kong's AAIA reported under the headline "Loss of Control - Inflight" the occurrence was rated a serious incident and opened an investigation.
There had been other similiar occurrences, see Incident: Virgin Atlantic B789 at Hong Kong on Sep 29th 2019, deviated from localizer and descended below minimum safe altitude, Incident: Etihad B789 at Hong Kong on Sep 7th 2019, veered off localizer and descended below safe height on ILS approach and Incident: Ethiopian B788 at Hong Kong on Jul 18th 2019, loss of control on ILS approach.
In response to the occurrences Boeing released a bulletin in December 2019 addressing the issues (see below).
On Aug 11th 2023 Hong Kong's AAIA released their final report into this occurrence as well as three more similiar occurrences concluding the probable cause of this serious incident was:
The LOC course deviation was caused by the software failure of the CLC autoflight function in the AFDS.
The AAIA analysed:
During the investigation of this occurrence, another operator encountered a similar occurrence on the B787 at VHHH on 7 September 2019. The flight data of this flight was sent to Boeing, the aircraft manufacture, for analysis. These two occurrences appeared to be identical and Boeing was able to determine the root cause.
Evaluation of the flight data suggested that the CLC AFF initiated the turn towards the RWY 25R LOC, as LOC annunciated the active roll mode.
After the CLC AFF had initiated the turn, the A/P transition to the LOC mode did not occur. This resulted in the aircraft HDG stabilised 20 degrees short of the LOC course and flying through the LOC course on this track, rather than properly capturing the LOC.
The recorded flight data was consistent with the LOC capture anomaly of the AFDS as described in the FTD 787-FTD-22-20001.
The LOC course deviation observed was due to the LOC capture anomaly of the AFDS.
The FTD stipulated that the issuance of a Flight Crew Operations Manual Bulletin and related FAA AD 2020-24-04, associated with the software modification released by Boeing via Alert SB B787-81205-SB270053-00 addressed this anomaly.
