Degrading baffle plates are to blame for high pressure compressor (HPC) stage 7-9 spool damage reported on Engine Alliance GP7270s and GP7722s, a proposed FAA directive slated for publication Thursday (.pdf) reveals.
Investigations revealed that material from stage 6 baffle plates failed due to high-cycle fatigue, FAA explains. The material damaged the 7-9 spool, causing it to crack. Engine Alliance developed a redesigned stage 6 disk to eliminate the failures.
The NPRM calls for inspections of stage 6 disks with part number (P/N) 382-100-505-0 before 1,500 cycles or, for disks with at least 1,000 cycles on them already, within 500 cycles. Follow-up inspections would be done every 500 cycles.
Identified disks must be removed from service at 6,800 cycles or at the next HPC module exposure, whichever comes first, FAA proposes.
The NPRM is the second FAA rulemaking in two weeks that impacts Engine Alliance-powered Airbus A380s. The first one, a direct final rule, targets high pressure turbine nozzles that contributed to an in-flight engine shutdown.