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ASN Wikibase Occurrence # 196134
Last updated: 20 November 2017
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Date:21-DEC-2015
Time:15:23 LT
Type:Silhouette image of generic B788 model; specific model in this crash may look slightly different
Boeing 787-8 Dreamliner
Owner/operator:Jetstar Airways
Registration: VH-VKE
C/n / msn: 36230/162
Fatalities:Fatalities: 0 / Occupants: 293
Other fatalities:0
Airplane damage: None
Category:Serious incident
Location:463 km north west of Darwin -   Australia
Phase: En route
Nature:International Scheduled Passenger
Departure airport:Melbourne-Tullamarine Airport, VIC (MEL/YMML)
Destination airport:Singapore-Changi International Airport (SIN/WSSS)
Investigating agency: ATSB
Narrative:
The Boeing 787-8 aircraft, departed Melbourne, Australia on a scheduled passenger transport service to Singapore. The flight, operating as
Jetstar Flight 07, departed at 01:40 UTC (12:40 local time). At 05:50 UTC, the aircraft was in cruise, being operated at FL400. The first officer was the pilot flying (PF) and autopilot and autothrottle were engaged.
At the date of this occurrence an airworthiness directive (AD/B787/2013-24-01) relating to reducing the risk of engine icing was in effect, requiring avoidance of ice crystal icing conditions. As such, weather information with relevant en route icing conditions was used by the operator for the purposes of flight planning. In accordance with the AD, the crew manoeuvred around any observed weather conditions that had potential to cause icing to the engines.
Approaching waypoint CURLY, about 250 NM north of Darwin, Australia, the crew reported that a green coloured area, with magenta patches appeared ahead on their weather radar. This area was too close to avoid.
As a precaution the crew activated the seat-belt light. The aircraft entered an area of light turbulence which then increased to moderate. Concurrently with the increase in turbulence the crew noticed erratic airspeed indications on both PFDs, the autopilot disconnected and multiple EICAS messages were displayed including AIRSPEED UNRELIABLE and FLIGHT CONTROL MODE. The FLIGHT CONTROL MODE annunciation indicated that the aircraft flight control system had reverted to secondary mode.
Shortly after the event, the captain took over the pilot flying role and the crew conducted the AIRSPEED UNRELIABLE checklist. The captain reported that this was a high workload situation and effective communication and coordination with the first officer greatly assisted the procedure.
The crew maintained an airspeed by setting a pitch angle and thrust level, as indicated in the applicable quick reference handbook table. Through comparison with this table, the crew were also able to identify the most accurate airspeed indication. The crew reported that at this stage it appeared that all indications had returned to normal.
The aircraft was 4 hours into an 8 hour journey, latched in secondary mode and could only be flown manually. Based on this, a decision was made to divert to Darwin.
After jettisoning fuel to reduce the aircraft weight to maximum landing weight, the crew requested a straight-in approach and made an uneventful landing at Darwin airport.

Contributing factors:
- The aircraft entered a region of high ice water content which caused icing of the three independent pitot sources and anomalous airspeed indications.
- Short duration anomalous airspeed indications caused the flight control computer to transition to secondary mode. In secondary mode, the autopilot and some auto-flight protections were unavailable to the flight crew.

Boeing revised the flight control software to reduce the chances of reverting to secondary mode in a short duration, erratic airspeed event.
In response to a previous, similar event on another B787-8, the FAA published an airworthiness directive warning flight crew not to make large abrupt magnitude flight control inputs in response to unrealistic drops in airspeed.
Boeing also revised the flight control software to limit the rate of elevator feel reduction with drops in airspeed. This will specifically allow the column to stay at a higher feel force to mitigate large and abrupt unintentional pitch inputs.

Sources:

http://www.atsb.gov.au/media/5773029/ao-2015-149-final.pdf

Accident investigation:
cover
Investigating agency: ATSB
Status: Investigation completed
Duration: 1 year and 6 months
Accident number: AO-2015-149
Download report: Summary report

Images:


Revision history:

Date/timeContributorUpdates
14-Jun-2017 06:03 harro Added
14-Jun-2017 06:59 harro Updated [Photo, ]

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