An engine imbalance caused a fire on an Airbus A330 with subsequent emergency landing at Singapore-Changi Airport, according to an investigation report issued by AAIB Singapore.
At about 01:12 hours (Local Time) on 16 May 2011, an Airbus A330-343 of Cathay Pacific took off from Singapore-Changi Airport on a scheduled flight to Jakarta. While climbing through 33,000 feet at 01:29 hours, the No.2 engine (a Rolls Royce Trent 700) stalled and a loud bang was heard and vibration was felt by the flight crew. The flight crew shut down the No.2 engine, following which the vibration reduced, but did not disappear. The flight crew declared an emergency to ATC and flew the aircraft back to Changi Airport.
About 15 minutes after the initial No.2 engine problem, when the aircraft was at 10,500 feet and descending into Singapore, the No.2 engine fire warning indication appeared and the flight crew discharged an engine fire extinguishing bottle. The fire warning indication was cleared but re-appeared after 69 seconds.
The flight crew discharged a second engine fire extinguishing bottle but was unsure if the fire had been extinguished as the fire warning light flickered intermittently.
After the aircraft landed, the Airport Emergency Service saw fire at the No.2 engine as they approached the aircraft and proceeded to put it out. No one was injured in this incident. The No.2 engine vibration was a result of the engine’s rotating assembly becoming unbalanced following the loss of a 130 mm tip section of one of the engine fan blades. The failure of the fan blade could be attributed to its mechanical strength having been compromised as a result of the use of an incorrect gas during the manufacturing process.
The interior of the No.2 engine fan case was damaged by the rubbing against it of the fan blades of the engine’s unbalanced rotating assembly. The severe rubbing generated heat resulting in the ignition of the Kevlar wrap of the fan case and in fire damage to the accessories on the right side of the engine.