Airworthiness Directives; Rolls-Royce plc RB211 Trent 700 Series Turbofan Engines

The FAA is superseding an existing airworthiness directive (AD) for Rolls-Royce plc (RR) RB211 Trent 700 series turbofan engines. That AD currently requires initial and repetitive borescope inspections of the high pressure-and-intermediate pressure (HP-IP) turbine internal and external oil vent tubes for coking and carbon buildup, and cleaning or replacing the vent tubes if necessary. This AD requires the same actions but uses more stringent tube replacement criteria than the previous AD. This AD results from a recent incident where an RB211 Trent 700 series turbofan engine had an oil vent tube rupture as a result of blockage, leading to significant loss of engine oil. The incident indicates that further measures are necessary to control carbon buildup in the oil vent tubes. We are issuing this AD to prevent internal oil fires due to coking and carbon buildup, that could cause uncontained engine failure and damage to the airplane.