What happened
An engine failure occurred involving a Trent 900 engine, which led to an engine shutdown. During the event, a fire warning was triggered, though subsequent investigations determined this was a spurious alert.
The investigation
Rolls-Royce, the manufacturer of the Trent 900, performed a teardown of the engine to identify the source of the failure. The inspection revealed that the low-pressure turbine stage 2 (LPT2) blades had suffered from internal corrosion. This corrosion caused fatigue cracking, which eventually led to the release of blade shroud debris. This debris traveled downstream, causing significant damage to the engine components.
Regarding the fire warning, investigators assessed the fire and overheat detection system. While no mechanical faults were found in the system itself, the manufacturer of the detector identified wear within the unit. This wear increased the unit's sensitivity to vibration, making it more likely to produce a false warning during the engine event.
Findings
- The internal corrosion of the LPT2 blades was caused by chemical residue left inside the hollow blades following cleaning operations performed during the last service in July 2015.
- Chemical residue from cleaning procedures was the primary driver of the blade fatigue and subsequent engine damage.
- Vibration during the engine failure, combined with worn detector components, likely caused the spurious fire warning.