Date: 14th November 2024
Location: East of Greenland, en route to Miami, FL, USA
Aircraft: Airbus A330-300, registration LN-RKS
Operator: SAS Scandinavian Airlines
Flight Number: SK-957
Flight Route: Stockholm (Sweden) to Miami, FL (USA)
Passengers: Approx. 250
Crew: 10
Summary of Events
On 14th November 2024, SAS Flight SK-957, an Airbus A330-300 en route from Stockholm to Miami, encountered turbulence while cruising at FL360 east of Greenland. The turbulence led to a low oil pressure indication on the left-hand Rolls-Royce Trent 772 engine. Following standard procedures, the crew shut down the engine and descended to FL280. At this altitude, the crew successfully restarted the engine and climbed back to FL360.
Upon entering Canadian airspace, the crew declared an emergency and opted to turn around and divert to Copenhagen Airport (EKCH), Denmark. The aircraft descended to FL350 and later climbed to FL370 before landing safely in Copenhagen approximately six hours after the initial turbulence encounter.
The Canadian Transportation Safety Board (TSB) is investigating the incident, and the aircraft remains grounded in Copenhagen as of 19th November 2024.
Aircraft and Crew Information
The Airbus A330-300 is a wide-body aircraft designed for long-haul operations, powered by two Rolls-Royce Trent 772 engines. LN-RKS is a well-maintained member of the SAS fleet, with a strong record of operational reliability.
The flight crew consisted of experienced pilots trained in handling engine malfunctions and emergency procedures. Their decision to follow protocols and return to Copenhagen ensured the safety of all passengers and crew onboard.
Sequence of Events
1. Cruise and Turbulence Encounter:
The aircraft was cruising at FL360 in Reykjavik FIR airspace when it encountered turbulence. Shortly after, the left-hand engine displayed a low oil pressure indication.
2. Engine Shutdown and Descent:
The crew followed the Quick Reference Handbook (QRH) procedures, shutting down the affected engine and descending to FL280 to reduce stress on the remaining engine.
3. Engine Restart and Climb:
At FL280, the crew successfully restarted the left-hand engine and climbed back to FL360.
4. Emergency Declaration and Diversion:
Upon entering Gander FIR airspace, the crew declared an emergency and decided to divert to Copenhagen as a precaution. The aircraft adjusted its cruising altitude during the return flight and landed safely at Copenhagen Airport without further incident.
Initial Investigation and Findings
The Canadian TSB, in collaboration with Scandinavian and European aviation authorities, has initiated an investigation. Key areas of focus include:
1. Turbulence Effects on Engine Systems:
• Assessing the impact of turbulence on the engine’s oil system.
• Investigating potential damage to sensors, valves, or oil lines caused by mechanical stress or vibrations.
2. Engine Restart Protocol:
• Reviewing the restart procedure at FL280 and evaluating engine performance post-restart.
3. Maintenance History:
• Analyzing recent maintenance records to determine if pre-existing conditions contributed to the low oil pressure indication.
4. Crew Decision-Making:
• Examining the crew’s adherence to standard operating procedures and their rationale for diverting to Copenhagen.
Turbulence and Oil Pressure Issues
Turbulence, particularly in polar airspace, can introduce mechanical stress to aircraft systems. In this incident, the vibrations caused by turbulence may have disrupted the oil supply system or triggered a false sensor reading. A low oil pressure warning typically indicates a potential risk to engine lubrication, necessitating immediate corrective action to prevent engine damage.
Passenger and Crew Impact
The incident resulted in no injuries to passengers or crew. SAS accommodated passengers in Copenhagen, providing alternate travel arrangements and support services to minimize disruption.
Conclusions
The turbulence-induced engine shutdown on SAS Flight SK-957 underscores the importance of robust maintenance protocols and effective crew training for managing in-flight anomalies. The crew’s adherence to QRH procedures and their decision to return to Copenhagen ensured the safety of everyone onboard.
Pending the outcome of the investigation, findings will likely inform operational best practices for managing engine issues in long-haul polar operations.
Recommendations
1. Enhanced Engine Monitoring:
• Airlines should employ advanced diagnostic systems capable of detecting oil pressure anomalies in real time, mitigating the risk of unnecessary engine shutdowns.
2. Maintenance and Inspection Protocols:
• Operators should prioritize inspections of oil systems, focusing on components susceptible to turbulence-induced stress.
3. Polar Operations Training:
• Flight crews should receive specialized training to manage anomalies associated with polar turbulence and remote operations.
4. Improved Communication Protocols:
• Enhance coordination between pilots and air traffic control during extended diversions to ensure efficient handling of emergencies.
Safety Lessons and Industry Impact
This incident highlights the operational challenges of long-haul flights over remote polar regions. The findings will contribute to industry-wide improvements in engine system reliability, turbulence management, and emergency response protocols.
Disclaimer
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Our investigation reports are based on all the evidence and facts we have at the time of writing and posting. We apologise if any details are missed or are not fully accurate.
