ASN Wikibase Occurrence # 235323
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| Date: | Saturday 7 September 2019 |
| Time: | 10:41 LT |
| Type: |  Boeing 787-9 Dreamliner |
| Owner/operator: | Etihad Airways |
| Registration: | A6-BLF |
| MSN: | 39651/416 |
| Year of manufacture: | 2016 |
| Fatalities: | Fatalities: 0 / Occupants: 179 |
| Aircraft damage: | None |
| Category: | Serious incident |
| Location: | Waypoint RIVER -
 Hong Kong
|
| Phase: | Approach |
| Nature: | Passenger - Scheduled |
| Departure airport: | Abu Dhabi International Airport (AUH/OMAA) |
| Hong Kong-Chek Lap Kok International Airport (HKG/VHHH) | |
| Investigating agency: | AAIA |
| Confidence Rating: |  Accident investigation report completed and information captured |
On 7 September 2019 at 1041hrs, an Etihad Airways Boeing 787-9 aircraft, flight ETD 834, while conducting an Instrument Landing System (ILS) approach to Hong Kong International Airport (HKIA) deviated from the localiser course.
Having gone past waypoint RIVER while turning left and attempting to establish on the Runway 25R localiser at about 15 NM from the runway, the aircraft kept deviating to the right of the localiser and descending below the Minimum Sector Altitude (MSA) of 4,300 ft. The aircraft subsequently established on the localiser course at about 11 NM from the runway, and landed without further incident. 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
History of this aircraft
Other occurrences involving this aircraft
| 27 May 2022 | A6-BLF | Etihad Airways | 0 | Lahore |  |
unk |
| Turbulence | ||||||
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 20-Apr-2020 19:58 | harro | Added |
| 21-Jul-2023 11:49 | harro | Updated |
| 19-Aug-2023 08:51 | harro | Updated |
Corrections or additions? ... Edit this accident description
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