Summary
The Federal Aviation Administration (FAA) proposes to supersede an existing airworthiness directive (AD) that is applicable to Pratt & Whitney (PW) JT9D-7R4 series turbofan engines. That AD currently requires modifications of the fan case assembly by installing a thicker one-piece fan case shield, and modifications of the outer front fan exit case assembly by installing ring segments. This proposal would require on JT9D-7R4 series turbofan engines with steel fan cases, replacement of the existing one-piece fan case shield with a thicker four-piece fan case shield and would add four fan case shield supports. This proposal is prompted by two uncontained full fan blade fracture events that resulted in penetration of the steel fan case and fan case shield. The actions specified by the proposed AD are intended to prevent uncontained fan blade failures, resulting in damage to the airplane.