Summary
We propose to supersede an existing airworthiness directive (AD) that applies to all RR RB211-535E4-37, -535E4-B-37, -535E4-B-75, and -535E4-C-37 turbofan engines. The existing 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. Since we issued that AD, we determined that the definition of shop visit is too restrictive in the existing AD. This proposed AD would continue to require those inspections and would change the definition of a shop visit to be less restrictive. We are proposing this AD to correct 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.