Airworthiness Directive · Amendment 39-17479 · Engine Alliance Turbofan Engines
Engine Alliance Turbofan Engines
This AD applies to Engine Alliance GP7270 and GP7277 turbofan engines with a high-pressure compressor (HPC) stage 6 disk, part number (P/N) 382-100-505-0, installed.
We are adopting a new airworthiness directive (AD) for certain Engine Alliance GP7270 and GP7277 turbofan engines. This AD was prompted by damage to the high-pressure compressor (HPC) stage 7-9 spool caused by failure of the baffle plate feature on affected HPC stage 6 disks. This AD requires initial and repetitive borescope inspections of the baffle plate feature and removal from service of the HPC stage 6 disk if the plate is missing material. This AD also requires mandatory removal from service of these HPC stage 6 disks at the next HPC module exposure. We are issuing this AD to prevent failure of the HPC stage 7-9 spool, uncontained engine failure, and damage to the airplane.
(1) For HPC stage 6 disks with fewer than 1,000 cycles- since- new (CSN) on the effective date of this AD, initially borescope inspect the baffle plate feature on the disk (360 degrees) before accumulating 1,500 CSN.
(2) For HPC stage 6 disks with 1,000 CSN or more on the effective date of this AD, initially borescope inspect the baffle plate feature on the disk (360 degrees) within the next 500 cycles-in-service (CIS).
(3) Thereafter, repetitively borescope inspect the baffle plate feature on the disk (360 degrees) within every 500 CIS.
(4) Remove the HPC stage 6 disk within 50 additional CIS, if the baffle plate feature is found cracked or missing material.
At next HPC module exposure, but not to exceed 6,800 CSN on the HPC stage 6 disk, remove the HPC stage 6 disk, P/N 382-100-505-0, from the engine.
After the effective date of this AD, do not install any HPC stage 6 disk, P/N 382-100-505-0, into any HPC module.
For the purpose of this AD, HPC module exposure is defined as disassembly of the compressor to where the HPC rotor assembly is removed and accessible.
