A European Union Aviation Safety Agency (EASA) order flags Rolls-Royce Trent 1000 turbine blades for targeted inspections to flag a flaw that could lead to engine failures.
The Aug. 22 airworthiness directive (AD) requires low pressure turbine (LPT) stage 1 blade assemblies—a pair of blades welded together at their outer edges—for inspections. The issue, according to EASA: cracking near the weld.
“Occurrences have been reported of finding cracking and separation in the weld region on a small number of affected parts during engine inspections,” the AD said. “If a significant number of blade pairs in a blade set are separated, this could change the vibration characteristics of the LPT stage 1 blade set and lead to the release of blade material during engine running,” which could cause an inflight shutdown, it added.
Each engine has 85 LPT stage 1 blade assemblies. If more than 32 of them are found with cracks, the engine must be removed and damaged blades changed, the EASA AD said.
The issue affects all Trent 1000-A, 1000-AE, 1000-C, 1000-CE, 1000-D, 1000-E, 1000-G, and Trent 1000-H engines. Operators of Boeing 787s with those engines must inspect affected parts before they reach 30,000 flight hr. (FH) or within 90 days, whichever comes later. Follow-up checks must be done every 4,500 FH.
Aviation Week Tracked Aircraft Utilization data shows many Trent-powered 787s routinely accumulated 500-600 FH per month during peak demand before the downturn. Recently, monthly totals of 300-500 FH are more common. At those rates, initial checks would be required after 5-8 years in service, with follow-ups every 9-15 months.
The Aviation Week Network Fleet Discovery database shows about 375 Trent-powered 787s in service. Of these, about 50 have at least 30,000 FH.
The new AD is similar to one issued in February that covers a population of engines with different thrust ratings. That directive flags a different subset of Trent 1000 models and set the initial inspection threshold at 22,500 FH and the maximum number of allowable, damaged blade sets at 29. Engine variants covered in the February AD are the Trent 1000-A2, AE2, C2, CE2, D2, E2, G2, H2, J2, K2, and L2.
EASA based the ADs on service information Rolls sent to customers in December 2022 and April 2023. The FAA has issued a draft rule that, if finalized, would mandate EASA’s February AD.
The weld issue’s root cause is not clear. Sources with knowledge of the issue tell Aviation Week that the problem is not production-related.
Queries to Rolls were not immediately answered.
The blade weld cracking issue does not appear to be related to a series of Trent 1000 reliability and durability problems that plagued the engine-maker and its customers starting in 2017. The company recently unveiled an upgrade package centered around a new high pressure turbine blade designed to end the string of issues that grounded 787s and clogged Rolls’s engine overhaul shops, peaking in 2018.
This story has been updated with additional details.
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