Airworthiness Directives; Pratt & Whitney JT9D Series Turbofan Engines

This amendment supersedes 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 amendment requires additional repetitive borescope inspections for sixth stage LPT inner airseals found with cracks less than one inch in length. This amendment is prompted by the publication of a revision to a PW service bulletin that introduces the new borescope inspections. The actions specified by this AD are intended to prevent an uncontained failure of the sixth stage LPT inner airseal, which can result in damage to the aircraft.