NPRM (2012-NE-06-AD, FAA-2012-0079) requires life reduction of effected HPT stg 1 front hubs to 13,700 cycle for our PW4168 engines. If a front hub has accumulated 12,700 or fewer CSN than it should be removed at or before 13,700 CSN. This will cause an engine early removal by 1,300 cycle. Because the engines were built at last S/Vs accordingly the Engine Manual limits at that time. In case of an early removal, it will cause stub life problem on other LLPs. Also, early removal by 1,300 cycle causes less maintenance reserve accumulation.
Our suggestion is; as it was requested by FAA AD 2011-25-09 para. (f) and (g) for HPT stg 1 and 2 seals, replacement of effected parts;
"at the next piece-part exposure after the effective date of this AD or before accumulating the number of cycles listed in Table XX of this AD, whichever occurs later."
We kindly request you to re-consider the threshold same as FAA AD 2011-25-09.
Thanks and Best regards,
Yalcin CELIK
Powerplant Chief Engineer
Onur Air
Yalcin Celik
This is comment on Proposed Rule
Airworthiness Directives: Pratt and Whitney Division Turbofan Engines
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