David Lee

Ref/a/ Docket No. FAA-2012-1329; Directorate Identifier 2012-NE-46-AD Korean Air Lines (KAL) of which headquarter is based in Seoul, Korea and KAL is operating GP7200 engine for A380 aircraft mainly routes to LAX and JFK. I received the referenced NPRM and review it. As KAL experienced many engine removals due to HPC S6 disk baffle plate missing in 2012, I can understand FAA’s intention on the NPRM. An service bulletin, EAGP7-72-236 has been released to recommend a regular borescope inspection on the HPC S6 disk baffle plate for missing material (1,000 cycles since new (CSN) at first and after, every 500 cycles) and give an 150 cycle allowance when missing material on the plate is identified but impact damage on airfoils of HPC S6, S7 and S8 is within the limit specified in the service bulletin. However, the NPRM says that this proposed AD would require initial and repetitive borescope inspections of the baffle plate feature and will NOT allow any further operation with the HPC stage 6 disk plate missing material. If the allowance in the service bulletin is not a part of the AD, we have concerns as follows: - It may cause lack of spare engine, so KAL could need to use more lease engine longer and accordingly, financial burden would be increased. - In addition, an aircraft could be grounded due to shortage of spare engine. As a result of that, it can lead to customers’ inconvenience. For these reasons, KAL would like to ask FAA to kindly consider putting the allowance to the AD provided that it proves to be safe through in-depth investigation. If it is not feasible, KAL expects FAA to permit the allowance only to an engine less than 1,500 CSN that is the inspection threshold that FAA proposes. In addition, KAL want to know if modification of the disk introduced in SB EAGP7-72-237 can fulfill requirement of the AD.