EASA warns of potential Boeing 787 Trent 1000 LPT blade assembly fractures

A directive has been given by the European Union Aviation Safety Agency (EASA) regarding a possible safety issue with the Rolls-Royce Trent 1000 engine's low-pressure turbine (LPT) stage 1 blade assemblies. The directive was prompted by Rolls-Royce's Alert Non-Modification Service Bulletin (NMSB) Trent 1000 72-AK919, which affects multiple modifications of the same engine used exclusively on the Boeing 787. 


EASA has stated that the latest directive affects the LPT stage 1 blade assemblies, Part Number (P/N) FW68788, which consists of a pair of blades welded together at the outer shroud. EASA has received reports of cracks and separation "in the weld region on a small number of affected parts during engine inspections." The regulator has warned that if a significant number of blade pairs in a blade set are separated, it could alter the LPT stage 1 blade set's vibration characteristics and cause blade material to be released during engine operation, resulting in secondary damage to the LPT module and a subsequent in-flight engine shutdown, potentially leading to "reduced control of the airplane." 

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As a result, EASA has mandated operators to inspect and replace the affected parts if necessary. Airlines must perform inspections of the Trent 1000 LPT in the shop or while the engine is still on the wing at the LPT stage 1 blade assemblies before the part has been in use for over 30,000 Flight Hours (FH) since its first installation on the engine or within 90 days of the AD's effective date. After that, inspections must be performed within intervals that do not exceed 4,500 FHs. For parts that have exceeded the FH threshold and are installed on engines in a repair shop at the directive's effective date, EASA requires inspections before the engine is put back into service. 

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If cracks or separations are discovered during on-wing engine inspections but not on more than 32 blade pairs, inspection timings must be adjusted per the Rolls-Royce NMSB. EASA has allowed airlines to use serviceable parts on their engines, but affected parts must be replaced with new LPT stage 1 blade assemblies during each shop visit after the AD's effective date. The regulator defines serviceable LPT stage 1 blade assemblies as those that have not been previously installed or have been used for less than 30,000 FHs since their installation on an engine, as well as those that have passed an inspection. A serviceable LPT disk is one that meets the acceptance criteria specified in the current Engine Manual T-Trent-10RR. The directive will take effect on September 5, 2023. According to ch-aviation.com data, there are 372 Boeing 787 aircraft equipped with the Trent 1000 engine, either actively flying, in storage, or in maintenance. This number does not include the two ex-Norwegian Boeing 787-8s, registered as VP-CVL and VP-CVM, which were dismantled at Glasgow Prestwick Airport (PIK).

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