Operators of Rolls-Royce-powered Boeing 787s are set to be instructed to conduct inspections of certain Trent 1000 low-pressure turbine discs, over a possible cracking risk.
Assessment of certain discs in service has revealed that rubbing contact with interstage static seals can lead to cracks in the front seal fins – which, in turn, could lead to cracks in the disc.
As an interim measure, the European Union Aviation Safety Agency is preparing to mandate an inspection of seal fins on the third- and fourth-stage discs – with specific part numbers – in the low-pressure turbine.
The one-time ultra-high sensitivity fluorescent penetrant inspections should take place at the next engine refurbishment shop visit, according to a proposed EASA directive.
If any cracking is indicated on the seal fins, the disc parts must be replaced.
EASA warns that the condition could lead to propagation of cracking, possible low-pressure turbine disc failure, and expulsion of high-energy debris.
Rolls-Royce has drawn up a service bulletin, dated 29 June, covering the issue. EASA has opened the directive for consultation until 3 August.