ASN Wikibase Occurrence # 235325
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| Date: | Friday 18 October 2019 |
| Time: | 15:49 LT |
| Type: |  Boeing 787-9 Dreamliner |
| Owner/operator: | Virgin Atlantic Airways |
| Registration: | G-VBOW |
| MSN: | 37978/534 |
| Year of manufacture: | 2017 |
| Fatalities: | Fatalities: 0 / Occupants: 271 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Waypoint RIVER -
 Hong Kong
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | London-Heathrow Airport (LHR/EGLL) |
| Hong Kong-Chek Lap Kok International Airport (HKG/VHHH) | |
| Investigating agency: | AAIA |
| Confidence Rating: |  Accident investigation report completed and information captured |
On 18 October 2019 at 1549 hrs, a Virgin Atlantic Airways Boeing 787-9, registration G-VBOW, while conducting an Instrument Landing System (ILS) approach to Hong Kong International Airport (VHHH) deviated from the localiser course.
During the ILS approach for Runway 25R to VHHH in Visual Meteorological Conditions (VMC), the aircraft with the autoflight system engaged intercepted the localiser, the aircraft then overshot the intended heading, diverging from the localizer course towards the rising terrain in the north.
The Pilot Flying disengaged the autoflight system and assumed manual control of the aircraft, re-establishing the aircraft on the ILS heading approximately 12 nautical miles (NM) from the runway threshold and landing the aircraft uneventfully. There was no damage to the aircraft.
The investigation team found that this serious incident was caused by a software problem embedded in the flight control module (FCM) of the autoflight director system (AFDS).
The Boeing 787 Autoflight Function (AFF) contains a Consistent Localizer Capture (CLC) control law that reduces the risk of Localizer (LOC) course overshoot in autopilot-engaged approaches that requires a large turn (40 degrees) onto the LOC course.
CLC provides the Boeing 787 with ILS performance consistent with a Ground-Based Augmentation System (GBAS) Landing System (GLS) approach. Using Global Positioning System (GPS) and runway information from the flight management function. CLC will turn the aircraft towards the LOC course before the LOC is within parameters for capture. In order to maximize the chance of capturing the LOC in one turn. “LOC” will annunciate on the FMA when a CLC turn begins and remain annunicated through the transition to LOC capture. Normally, CLC will automatically transition to the LOC capture control law when the LOC is within parameters to capture and “LOC” will continue to be visible on the FMA.
However, depending on the geometry and groundspeed of the approach, CLC may activate for such a short time that the three FCMs fail to synchronize the engaged autopilot mode and fail to transition to the LOC capture mode. This may result in the aircraft turning to a LOC intercept angle of approximately 20 degrees and flying through the LOC on this track, rather than properly capturing the LOC.
“LOC” will remain on the FMA despite the failed capture and, in some circumstances, the aircraft may begin descent down the glideslope while 20 degrees off of the LOC course.
Cause
The LOC course deviation was caused by the software failure of the CLC auto-flight function in the AFDS.
Accident investigation:
 |
|
Sources:
AAIA
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 20-Apr-2020 20:00 | harro | Added |
| 21-Jul-2023 11:49 | harro | Updated |
| 19-Aug-2023 09:23 | harro | Updated |
Corrections or additions? ... Edit this accident description
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