Summary
This document proposes the supersedure of an existing airworthiness directive (AD), applicable to Pratt & Whitney (PW) JT9D series turbofan engines, that currently requires initial and repetitive inspections of the sixth stage low pressure turbine (LPT) inner airseal, and modification of the sixth stage LPT inner airseal to reduce the potential for two failure modes. This action would require additional repetitive borescope inspections for sixth stage LPT inner airseals found with cracks less than one inch in length. This proposal is prompted by the publication of a revision to a PW service bulletin that introduces the new borescope inspections. The actions specified by the proposed AD are intended to prevent an uncontained failure of the sixth stage LPT inner airseal, which can result in damage to the aircraft.