Airworthiness Directives; Rolls-Royce plc (RR) RB211-535 Series Turbofan Engine

We are superseding an existing airworthiness directive (AD) for all RR RB211-535E4-37, -535E4-B-37, -535E4-B-75, and -535E4-C-37 turbofan engines. That AD currently requires performing initial and repetitive visual and fluorescent penetrant inspections (FPI) of the low-pressure (LP) turbine stage 1, 2, and 3 discs to detect cracks in the discs. This new AD continues to require those inspections and changes the definition of a shop visit to be less restrictive. This AD was prompted by our finding that the definition of shop visit in the existing AD was too restrictive. We are issuing this AD to revise the definition of shop visit and to detect cracks in the LP turbine stage 1, 2, and 3 discs, which could result in an uncontained release of LP turbine blades and damage to the airplane.