AD FAA-2006-23605

The FAA is superseding an existing airworthiness directive (AD) for Rolls-Royce plc (RR) models RB211 Trent 768-60, Trent 772-60, and Trent 772B-60 turbofan engines that have not incorporated RR Service Bulletin (SB) No. RB.211-72-E708, SB No. RB.211-72-F227, or SB No. RB.211-72-E965, at original issue or later revision. That AD currently requires initial and repetitive borescope inspections of the high-pressure/intermediate-pressure (HP/IP) turbine bearing internal oil vent tube, scavenge tube, and tube heat shields for wear and cracking, and removing tubes from service if found with any cracks beyond serviceable limits. That AD also currently requires installation of a new or modified HP/IP turbine bearings support as terminating action for the repetitive borescope inspections. This AD has the same requirements, and adds a repetitive inspection of the vent flow restrictor for blockage. This AD results from RR revising their alert service bulletin for inspection of the HP/IP turbine bearing internal oil vent tube, scavenge tube, and tube heat shields for damage, to include a repetitive inspection of the vent flow restrictor for blockage. We are issuing this AD to prevent oil ejecting from the HP/IP turbine bearings chamber and igniting. Burning oil can cause the intermediate-pressure (IP) shaft to fracture, the IP turbine to overspeed, and possible uncontained failure of the engine.