History of the Flight
On 23 May 2015, an Airbus A330-300 aircraft, registration 9V-SSF, operated by Singapore Airlines, was conducting a scheduled passenger flight from Singapore to Shanghai, China. At 12:56 UTC, while cruising at 39,000 feet approximately 130 nautical miles southeast of Hong Kong, the flight crew observed weather cells along the route. After receiving air traffic control clearance, they turned right to a heading of 080 degrees, then left to 020 degrees at 12:56:34 to avoid higher-intensity weather. They activated the seat belt sign, announced possible turbulence, set the target speed to 0.78 Mach (turbulence penetration speed), and turned on wing anti-ice and continuous ignition for both engines.
Shortly after entering a weather cell, the aircraft experienced engine surges. The Electronic Centralised Aircraft Monitoring (ECAM) system first displayed a surge message for the right engine (Engine No. 2), but before the flight crew could reduce thrust, a second message for the left engine (Engine No. 1) appeared. Due to ECAM display priority, the crew followed the left engine checklist and decided to shut down Engine No. 1, believing it remained in surge. Flight data recorder (FDR) data later showed that both engines had surged and self-recovered within 12 seconds, with Engine No. 2 surging three times and Engine No. 1 surging twice; the first surges occurred at 12:56:56, about 22 seconds after the left turn.
The crew declared Mayday, shut down the left engine, and with ATC clearance descended to 26,000 feet. They considered diverting to Hong Kong or Guangzhou but decided to proceed to Shanghai, noting that Xiamen and Hangzhou could serve as alternates and the weather ahead was clear. En route, the crew successfully restarted the left engine at 26,000 feet; engine parameters appeared normal. They cancelled the Mayday and, after consulting the operator's control center near Xiamen, confirmed the decision to continue. The aircraft landed in Shanghai without further incident.
Post-Flight Activities
In Shanghai, ground inspections and tests on both engines, including borescope inspections, variable stator vane and FADEC tests, magnetic chip detector checks, and engine ground runs with high-pressure compressor (HPC) surge margin acceptance tests, revealed no abnormalities. The aircraft then returned to Singapore without incident, where HPC surge margin tests were repeated with normal results.
Although the aircraft could have been released for service, the operator decided on a new policy of not pairing new engines on new twin-engine aircraft. Consequently, Engine No. 1 was removed and disassembled at an engine overhaul facility in Singapore for examination. A significant amount of grey dust deposit, composed mainly of aluminium and silicon (constituents of the IPC rotor path abradable material), was found on intermediate pressure compressor (IPC) rotor blades and stator vanes, intermediate pressure turbine nozzle guide vanes, and the high pressure turbine stubshaft. Signs of heavy rubbing of the rotor path abradable lining were observed at Stages 3 and 6 of the IPC, with light rubbing in other stages.
Conclusion
The Transport Safety Investigation Bureau concluded that the incident occurred because the aircraft encountered an area of adverse weather, which resulted in both engines surging.