What happened
On August 1, 2008, a British Midland Airbus A321-231, registration G-MIDL, was operating an international passenger flight from East Midlands Airport, Great Britain, to Tenerife South Airport, Spain. The aircraft was carrying 191 passengers and 8 crew members.
While cruising at FL350 within the Lisbon FIR, approximately 105 NM west of the Faro VOR, the flight crew reported audible abnormal engine noise and airframe vibrations. This was immediately followed by an "ENG2 STALL" message on the ECAM. The crew performed the appropriate checklists and managed to stabilize the engine by reducing power; however, any attempt to increase thrust resulted in recurring abnormal behavior. Consequently, the crew decided to shut down engine #2 and diverted the aircraft to Faro International Airport, Portugal, where they performed an uneventful single-engine landing at 09:27 UTC.
The investigation
The GPIAAF investigation examined the history of the aircraft and the specific condition of the #2 engine, an IAE V2533-A5 turbofan. Investigators reviewed maintenance records, which revealed that the aircraft had experienced a similar "ENG2 STALL" message during a descent on July 30, 2008. Although a borescope inspection was performed following that event, no damage was detected at that time.
Following the August 1 incident, a borescope inspection of the engine revealed significant damage to the High Pressure Compressor (HPC) stage 6 rotor blades, including missing fragments. The engine was subsequently removed for overhaul. During the shop visit, investigators found traces of organic material in the outer annulus and impact marks on the HPC stage 3 and 4 rotor blades. Detailed laboratory analysis by International Aero Engines (IAE) confirmed that the damage was the result of foreign object debris (FOD) ingestion.
Findings
- The primary cause of the engine stall was the deterioration of the HPC due to impact damage on the stage 6 rotor blades and stator vanes.
- The damage originated from the ingestion of hard-body FOD and organic material during a previous flight.
- The initial FOD impact caused a crack in an HPC stage 6 rotor blade, which led to the release of an airfoil during the July 30 flight.
- The release of this airfoil initiated secondary cracks and further damage to subsequent stage 6 components, eventually leading to the engine stall during the August 1 cruise phase.
- The crew followed all standard operating procedures, and the operator had complied with all maintenance requirements.