What happened
On September 17, 2020, an ATR 72, registration SP-SPD, was operating a flight from Basel (LFSB) to Cologne (EDDK). Upon arrival at Cologne, ground maintenance personnel conducting a post-flight inspection identified damage to the compressor blades of the number 2 engine (a PW127F model) that exceeded allowable limits.
On September 19, 2020, an external service provider performed a borescope inspection, which confirmed extensive damage to both the low-pressure and high-pressure compressor blades, as well as the compressor casing. The engine was subsequently removed and sent to a repair facility in France.
The investigation
Following the removal of the engine, a detailed inspection report was provided by the repair facility, StandardAero. The analysis revealed that the most significant damage was concentrated on the low-pressure centrifugal compressor blades. While the high-pressure compressor showed only minor damage, notable material loss and abrasion marks were discovered on the rear compressor inlet.
Investigators examined the engine's flight data recorder (FDR), which showed that engine parameters during the preceding flights remained within normal operating ranges. Technical personnel also inspected the aircraft's air intakes, engine nacelles, propellers, and other components located in the engine's intake path; no missing parts or external damage were found on the airframe. Furthermore, the crew's adherence to procedures during engine tests, taxiing, and takeoff was reviewed, and no irregularities were identified. The operator also reviewed available airport camera footage, which yielded no evidence of contributing factors.
Findings
- The primary cause of the damage was the ingestion of a foreign object, likely metallic, into the engine.
- This object caused the observed damage to the low-pressure and high-pressure compressor blades and the compressor inlet.
- No traces of the foreign object remained within the engine following the event.