Date: 12th February 2024
Location: Melbourne, Victoria, Australia
Aircraft: Airbus A330-300, registration 4R-ALQ
Operator: SriLankan Airlines
Flight Number: UL-605
Flight Route: Melbourne, Australia, to Colombo, Sri Lanka
Passengers and Crew: Not disclosed
Summary of Events
On 12th February 2024, SriLankan Airlines Flight UL-605, an Airbus A330-300 en route from Melbourne to Colombo, returned to Melbourne shortly after takeoff due to the smell of smoke onboard. The crew stopped the climb at FL215 and decided to return as a precaution. The aircraft landed safely on Runway 16 approximately 50 minutes after departure, and all passengers disembarked without incident.
Passengers reported the smell of smoke in the cabin, which seemed to originate from the cockpit. SriLankan Airlines later attributed the diversion to a technical issue.
Sri Lanka’s Aircraft Accident Investigation Bureau (AIB) rated the occurrence as an incident and initiated an investigation. The aircraft remained grounded for further inspections and repairs.
Aircraft and Crew Information
Aircraft
The Airbus A330-300, registration 4R-ALQ, is a wide-body aircraft designed for long-haul flights, equipped with advanced avionics and environmental control systems to ensure passenger comfort and safety.
Crew
The crew acted promptly, adhering to standard operating procedures, ensuring passenger safety, and managing the return to Melbourne efficiently.
Sequence of Events
1. Climb and Smoke Detection:
• The aircraft was climbing out of Melbourne’s Runway 16 when the crew and passengers detected a burning odour followed by smoke in the cockpit and parts of the cabin.
2. Decision to Return:
• The crew stopped the climb at FL215, declared an emergency, and initiated a return to Melbourne.
3. Safe Landing:
• The aircraft landed safely on Runway 16 at Melbourne Airport approximately 50 minutes after departure.
4. Post-Incident Actions:
• Passengers disembarked safely. The airline arranged alternate travel plans for the affected passengers.
Investigation Findings
Sri Lanka’s AIB conducted a thorough investigation and released its final report in March 2024, identifying the probable cause of the incident as the seizure of the Air Cycle Machine (ACM) within the aircraft’s environmental control system.
Key Findings
1. ACM Failure:
• The Air Cycle Machine seized during the climb, leading to a strong burning odour followed by smoke.
2. Component Disintegration:
• The ACM manufacturer reported that the extent of the unit’s disintegration made it impossible to detect the precise cause of the failure.
3. System Implications:
• The ACM is a critical component of the aircraft’s air conditioning and pressurization system. Its failure can result in overheating and smoke.
4. Crew Actions:
• The crew’s decision to return was timely and prevented the situation from escalating.
Passenger and Crew Impact
All passengers and crew were unharmed. SriLankan Airlines ensured the safety and comfort of passengers following the incident, providing assistance and rebooking flights where necessary.
Conclusions
The incident underscores the critical role of the Air Cycle Machine in maintaining cabin conditions and the potential safety risks associated with its failure. The investigation highlighted the need for enhanced monitoring and maintenance protocols to detect and address such failures before they occur.
The crew’s professional response ensured passenger safety, demonstrating the importance of training and adherence to emergency procedures.
Recommendations
1. Enhanced Maintenance of ACMs:
• Operators should implement more frequent and rigorous inspections of Air Cycle Machines, focusing on early signs of wear or potential failure.
2. ACM Design Improvements:
• Manufacturers should consider design modifications to enhance the durability and reliability of ACM components.
3. Real-Time Monitoring Systems:
• Airlines should adopt advanced diagnostic tools to monitor ACM performance during flight and alert crews to potential failures.
4. Crew Training:
• Reinforce training for flight crews to handle environmental control system failures and cabin smoke scenarios.
5. Incident Reporting:
• Share findings with other operators to enhance industry-wide safety practices and mitigate risks related to ACM failures.
Safety Lessons and Industry Impact
This incident highlights the need for robust maintenance and monitoring protocols for critical aircraft systems, such as the Air Cycle Machine. The findings are expected to influence industry practices, particularly in the areas of component design and preventive maintenance, enhancing overall aviation safety.
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