Summary
The FAA proposes to supersede an existing airworthiness directive (AD) for Rolls-Royce plc (RR) RB211-524 series turbofan engines. That AD currently requires initial and repetitive borescope inspections 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 proposed AD would require initial and repetitive borescope inspections of the head section and meterpanel assembly of the combustion liner, and replacement, if necessary, with serviceable parts, 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 proposed AD results from five events that are directly attributed to combustor head break-up and meterpanel failure which were found at overhaul inspection. At least one of these events resulted in a combustion case burn-through. We are proposing this AD to prevent engine combustion liner deterioration, which can result in combustion liner breakup, case burn-through, and engine fire.