MD600 pilot reported abnormal engine noises during start and shutdown of engine. Post maintenance inspection found damage to turbine wheel due to improper maintenance of fuel nozzle.

Narrative

Background: This report supplements earlier reports related to: Multiple in-flight engine flameouts Detached fuel nozzle due to unauthorized disassembly; and Abnormal engine noises during spool-up and shutdownThe helicopter was ferried to ZZZZ today after post maintenance check on Day 0 for further technical evaluation.New Technical Finding (Day 6): After flight I reported the strange Noise during flight and shutdown to maintenance for in-depth engine inspection at ZZZZ; maintenance personnel discovered: fracture damage to turbine wheels in the engine's hot sectionSpecifically; Stage 1 and/or Stage 2 turbine wheels show cracking and broken blades; missingDamage is consistent with foreign object ingestion; most likely caused by the crushed fuel nozzle (as described in prior reports)The finding confirms progressive mechanical failure since the original maintenance errorThis damage explains: The previously noted abnormal noises during engine transitionsLikely imbalance or resonance during operation:Safety Assessment: The engine is no longer airworthy and must undergo full removal and overhaul per Rolls-Royce MM and approved proceduresRisk of catastrophic engine failure in continued operation is confirmedThis case reflects a critical task of OEM (Original Equipment Manufacturer) maintenance standards; with severe safety implicationsActions Taken: Aircraft is grounded indefinitely at ZZZZ Engine data; images; and damaged components are being documentedfor Safety the whole engine needs to go to a OEM approved center Investigation into the original maintenance provider and maintenance history is ongoing.Ground Run and flight after new Combustion and Liner was performed; noise from Engine after shutdown; Reported this to the engineer.Relocated helicopter; to ZZZZ; Noise reported to Maintenance when landed.Maintenance Found Turbine Wheels broken and damaged heavyThis case highlights the consequences of unauthorized component disassembly; specifically the fuel nozzle; as per manufacturer guidance.