AD FAA-2007-29343

The FAA is superseding an existing airworthiness directive (AD) for Rolls-Royce plc (RR) RB211-535E4-37, RB211-535E4-B-37, and RB211-535E4-B-75 series turbofan engines. That AD currently requires initial and repetitive ultrasonic inspections of installed low pressure compressor (LPC) fan blade roots on-wing and during overhaul, and relubrication according to accumulated life cycles. Also, that AD introduces application of Metco 58 blade root coating as an optional terminating action. This AD requires the same actions but adds compliance paragraphs to relax the compliance schedule for repetitive inspections for fan blades operating within RB211-535E4 flight profiles A and B, if certain requirements are met. This AD also relaxes the initial compliance threshold by extending the cycles at which an initial inspection is required. This AD results from RR issuing Mandatory Service Bulletin (MSB) No. RB.211-72-C879, Revision 5 and Revision 6, that introduced a relaxed repetitive compliance schedule for fan blades operating within RB211-535E4 flight profiles A and B, if certain requirements are met, and introduced a relaxed initial compliance threshold. We are issuing this AD to detect cracks in LPC fan blade roots, which if not detected, could lead to uncontained multiple fan blade failure, and damage to the airplane.