Operators of some Rolls-Royce Trent 1000-powered Boeing 787s are being cautioned over time limits for low-pressure compressor front cases.
Engineering analysis has found that 38 of such cases have "non-optimal material properties", says the European Union Aviation Safety Agency.
It states that this could "inhibit" the ability of the engine to contain high-energy debris in the event of a fan-blade failure, resulting in release of debris.
Rolls-Royce has developed an updated life management for the parts and identified the engines which have those components installed in a service bulletin.
EASA is set to require removal of the affected engines from service in order to replace the front cases of the low-pressure compressor, in accordance with the ultimate dates listed in the bulletin. The requirement is contained in a proposed airworthiness directive open for consultation until 8 November.