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ASN Wikibase Occurrence # 195521
Last updated: 18 November 2018
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Date:20-MAY-2017
Time:07:26 UTC
Type:Silhouette image of generic A388 model; specific model in this crash may look slightly different
Airbus A380-842
Owner/operator:Qantas
Registration: VH-OQG
C/n / msn: 47
Fatalities:Fatalities: 0 / Occupants: 506
Other fatalities:0
Aircraft damage: Minor
Category:Incident
Location:Approx 2 hrs SW of LAX -   Pacific Ocean
Phase: En route
Nature:International Scheduled Passenger
Departure airport:Los Angeles International Airport, CA (LAX/KLAX)
Destination airport:Melbourne Airport (MEL/YMML)
Investigating agency: ATSB
Narrative:
The Airbus A380-842 aircraft was operating Qantas flight QF94, from Los Angeles International Airport (LAX), United States, to Melbourne, Australia. The aircraft departed from runway 24L at LAX at about 05:42 UTC, at the maximum take-off weight of 569 tonnes.
About two hours after departing LAX, the flight crew requested and received ATC clearance to climb from FL320 to FL 340. The flight crew commenced the climb and increased the thrust on all four engines to 93 per cent ‘N1’.
As the aircraft passed FL325, the crew on the flight deck heard a loud bang and felt a sudden and unusual vibration of the aircraft, which reduced significantly after about 2 seconds. The first officer noticed No. 4 engine’s N1 was much lower than the other three engines – at about 49 per cent (although the flight data showed about 71 per cent N1). The captain, who was in the crew rest area, heard the bang and felt the vibration so he returned to the flight deck.
Flight data showed that as the aircraft passed FL325, the No. 4 engine intermediate pressure turbine experienced an overspeed and its N2 increased from 92 per cent to the redline limit of 98.5 per cent over the next 2 seconds. An electronic centralised aircraft monitoring (ECAM) ‘ENG 4 N2 OVER LIMIT’ message and master warning appeared for 2 seconds.
The second officer and first officer saw an ECAM message flash up but it disappeared before they could read it.
Shortly after, an advisory message (ADV) appeared on the engine warning display and 6 seconds later the message ‘ENG 4 NORM MODE FAULT’ appeared on the ECAM, along with the associated checklist, a single chime and illumination of the master caution. The ECAM message indicated that there was a problem with the full authority digital engine control (FADEC) of that engine. That fault was triggered by the automatic reversion of the FADEC of engine 4 to alternate mode, caused by the loss of air data or engine sensing parameters.
The flight crew actioned the ECAM first because it had a higher priority than the advisory message.
There were only two items on the ECAM checklist. The first required the flight crew to select the switch to set the FADEC to alternate mode for all engines. The second item was to set the autothrust as required (the autothrust was already at an appropriate setting). After completing those two actions, the ECAM message cleared and there were no other ECAMs at that stage.
The first officer received an interphone call from a cabin crewmember in the forward main galley reporting a bang and feeling vibrations. He then received a second interphone call from the cabin crewmember in the main economy galley, reporting that a passenger had seen flames and sparks coming from the right outboard engine.
As the flight crew finished actioning the engine 4 normal mode fault ECAM checklist, the captain arrived on the flight deck, about 60 to 90 seconds after he had heard the bang. The second officer made the required callout to the first officer when the aircraft was 1,000 ft below FL 340, then swapped out of the captain's seat. The first officer briefed the captain on the events, and the captain resumed the Pilot Flying role from the left seat and the first officer became the Pilot Monitoring.
The second officer received multiple calls from cabin crewmembers advising that the aircraft was vibrating in an unusual way, and some had seen sparks and flames. The flight crew found this information very useful because at that stage they had no indication on the flight deck of engine fire.
The flight crew investigated the cause of the ADV message and found that the N1 vibration signal for engine No. 4 indicated 10 units, which was the maximum value.
At about 07:24, the aircraft levelled off at FL340 and the flight crew commenced the abnormal checklist for high engine vibration.
At 07:26:44, the engine fire warning ‘ENG 4 FIRE’ ECAM message displayed. The flight crew did not finish the high vibration checklist because the engine fire warning had the highest priority and the flight crew actioned the associated checklist. At 07:27:02, the flight crew selected the No. 4 engine master switch off, then pushed the engine No. 4 fire button and discharged one fire retardant agent. The engine fire ECAM cleared.
With the No. 4 engine shut down, the flight crew discussed their options. The aircraft was short of the equal time point between Los Angeles and Honolulu and the weather at both airports was suitable for a diversion, so the crew decided to return to Los Angeles.
The second offficer spoke to the company (Qantas) maintenance watch about the aircraft’s status and to the integrated operations centre about the return to Los Angeles. He also sent a message via the aircraft communications addressing and reporting system (ACARS) advising the company of the engine fire and that they were returning to LAX. The first officer declared a PAN and requested ATC clearance to descend initially to FL300 and later to FL290, advising they had shut down an engine and required a diversion to LAX. Air traffic control cleared the aircraft to return to LAX, which was about 2 hours away.
The captain made a public address to the cabin crew and passengers stating that they had an engine issue and had shut down one engine, and were returning to Los Angeles.
There was a light easterly wind at LAX, which would mean a tailwind on runway 25L of about 3 kt. Despite this, the flight crew assessed that it was preferable to land on runway 25L than runway 07R. This was because of sand dunes and a relatively dark area on the approach to 07R and, more significantly, because autoland is not permitted on runway 07R. They therefore planned for an autoland on runway 25L at a landing weight of about 500 tonnes, and this was programmed into the flight management system. The FO and captain discussed the autobrake setting and elected to set autobrake 2.
When the flight crew received the next weather update, there was an indication of a 5 to 6 kt tailwind on runway 25L. They reworked the landing calculations and found that there was still sufficient margin available on runway 25L as their preferred runway for autoland. They decided, however, to jettison fuel down to a landing weight of 461 tonnes, which gave them a safety margin of 860 m runway length.
At 09:44, the fuel jettison was completed over water prior to crossing the coast, about 140 NM from LAX.
The flight crew conducted a normal approach and autoland landing onto runway 25L at about 09:56.
During the landing roll, as the aircraft decelerated to 80 kt, the captain deselected autobrake and used the full length of the runway to gradually stop the aircraft. After receiving ATC clearance, the captain taxied the aircraft to the parking bay escorted by airport firefighting services. The maximum brake temperature recorded was 535 °C, within the normal range. As such, there was no requirement for an emergency disembarkation and the passengers and crew disembarked at the gate.

Findings:
- Internal corrosion of low-pressure turbine stage 2 blades resulted in fatigue failure and separation of blade debris and downstream damage through the engine.
- The blade corrosion resulted from chemical residue associated with the cleaning procedure used during the last engine service.

Sources:

http://www.smh.com.au/national/qantas-flight-explosion-sparks-from-engine-as-melbournebound-flight-from-los-angeles-aborted-20170520-gw9iqv.html
https://www.atsb.gov.au/publications/investigation_reports/2017/aair/ao-2017-055/

Accident investigation:
cover
  
Investigating agency: ATSB
Status: Investigation completed
Duration: 1 year and 5 months
Download report: Final report


Revision history:

Date/timeContributorUpdates
21-May-2017 06:39 Geo Added
21-May-2017 06:48 harro Updated [Date, Time, Operator, Departure airport, Destination airport, Narrative]
17-Dec-2017 19:04 AF5541 Updated [Total occupants, Source]
17-Dec-2017 19:05 harro Updated [Registration, Source, Damage]
19-Oct-2018 19:20 harro Updated [Time, Total occupants, Country, Narrative, Accident report, ]

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