What happened
During the application of take-off power and the subsequent acceleration of engine components, the right engine experienced a surge event and a loss of performance. The incident was triggered by the movement of a foreign object through the engine's internal structure. The disruption of aerodynamic flow through the high-pressure compressor (HPC) led to the engine's inability to maintain stable operation during the critical take-off phase.
The investigation
Investigators examined the damage to the high-pressure compressor section and identified a screwdriver tip lodged within the cooling cavity. The physical evidence suggested that the tip had fallen into the low-pressure compressor (LPC) bleed duct, moved through the interstage duct, and entered the HPC. Analysis of the damage to the rear fairing screw indicated that the tool was likely left in the screw or dropped into the bleed duct during maintenance activities.
As the engine was started, the tip traveled through the HPC, striking various internal components and leaving witness marks. The investigation found that the damage to the LPC was absent, which ruled out the possibility that the tip was runway-related foreign object debris (FOD).
Findings
- The primary cause was a screwdriver tip left in a fairing screw or bleed duct during maintenance.
- The tip's movement through the HPC caused impact damage to several components, specifically a stage 5 blade and a stage 6 vane.
- This impact initiated fatigue cracks in the affected blade and vane.
- One of these cracks reached a critical size due to the combination of aerodynamic forces, vibrations, and centripetal acceleration.
- The failure of the blade or vane likely led to a secondary impact between the two components, resulting in the failure of an additional five compressor blades.
- The resulting structural damage disrupted the aerodynamic flow, causing the engine to surge.