Airworthiness Directives; Rolls-Royce plc RB211-524 Series Turbofan Engines

The FAA is superseding an existing airworthiness directive (AD) for certain Rolls-Royce plc (RR) RB211-524 series turbofan engines. That AD currently requires initial and repetitive borescope insepctions of the head section and meterpanel assembly of the combustion liner, and replacement, if necessary, with serviceable parts. In addition, that AD allows an optional installation of a front combustion liner with a strengthened head section as a terminating action to the inspection requirements. This AD requires initial and repetitive borescope inspections of the head section and meterpanel assembly of the combustion liner, and replacement if necessary with serviceable parts. This AD also requires reduction of the inspection intervals of certain RB211-524 engine models that have not been repaired to RR Field Repair Scheme FRS5367/B, and a mandatory terminating action to be completed by a certain date. This AD results from five events that are directly attributed to combustor head breakup and meterpanel failure which were found at overhaul inspection. At least one of these events resulted in a combustion case burn-through. We are issuing this AD to prevent engine combustion liner deterioration, which can result in combustion liner breakup, case burn-through, and engine fire.