Volcanic ash-related damage most likely did not contribute to the failure of a Thomas Cook Airbus A330-200’s No. 2 engine at Manchester Airport in June 2013, a U.K. Air Accidents Investigation Branch (AAIB) incident report addendum says.
The incident took place as the A330 was rolling down Manchester’s Runway 23R during a scheduled departure for Punta Cana in the Dominican Republic. At 105 kt, the aircraft suddenly yawed to the right. The captain took control and aborted the takeoff.
Video of the incident shot by an onlooker showed a flash of flame and cloud of smoke exiting the engine’s exhaust, followed by the aircraft coming to a stop 22 sec. later. After pausing on the airfield to cool its brakes, the aircraft was cleared by emergency services to return to the terminal, where all 328 passengers and 11 crew disembarked.
The investigation revealed that a high-pressure (HP) turbine blade detached just above its root fixing. Metallic debris from the detached blade started a chain reaction that damaged the intermediate- and low-pressure turbines and nozzles, which created more debris and ultimately the seizure of both the intermediate- and low-pressure spools.
“Laboratory analysis of the fractured blade root found multiple crack initiation locations caused by Type 2 Sulphidation corrosion,” AAIB noted in its original incident report. The particular type of corrosion is caused by mixing high-temperature components with sulphur, which could come from fuel or airborne contaminants, including volcanic ash. In this case, the corrosion led to a crack subjected to high-cycle fatigue propagation.
Further investigation of the blade noted “unidentified deposits,” which Rolls-Royce examined in detail after AAIB’s initial report was published.
“There was concern that these deposits may have been volcanic in origin, in particular from the 2010 eruption of Eyjafjallajokull in Iceland, so additional forensic analysis was carried out,” AAIB explains.
The analysis “did not identify compounds typically associated with volcanic activity,” AAIB notes in its addendum. “However, although an encounter with volcanic gaseous sulphur cannot be discounted it is concluded that the deposits probably are an accumulation of atmospheric dirt and pollutants.” The engine that failed had 5,200 cycles since its last overhaul.
The importance of avoiding both concentrated and diffuse volcanic ash clouds has long been known, but has been spotlighted in recent years thanks in part to the 2010 Eyjafjallajokull eruption that shut down some European airspace. While concentrated clouds are more dangerous, diffuse clouds are problematic because they are hard to detect and often cause engine performance degradation and irreversible aircraft damage.
The International Civil Aviation Organization in 2012 published a guide on flight safety and volcanic ash that includes post-incident response guidance. The AAIB report does not link the A330’s flight history with a known volcanic ash cloud encounter.