AD FAA-2011-0233

We are superseding an existing airworthiness directive (AD) for RR RB211-Trent 700 series turbofan engines. That AD currently requires, for the step aside gearbox (SAGB), repositioning of the oil metering jet up into the oil distributor within the bevel gearshaft, followed by initial and repetitive visual inspections of the magnetic chip detector (MCD). Since we issued that AD, RR has demonstrated that the repositioning of the oil metering jet eliminates the need for the repetitive inspections. This AD changes the applicability from RB211- Trent 700 series turbofan engines, to RB211-Trent 768-60 and Trent 772- 60 turbofan engines. This AD also eliminates the visual inspections of the MCD from the AD requirements. This AD was prompted by RR demonstrating that the repositioning of the oil metering jet eliminates the need for the repetitive inspections, by the need to correct the AD applicability, and by the need to eliminate the visual inspections of the MCD. We are issuing this AD to prevent in-flight engine shutdowns caused by SAGB driving bevel gearshaft ball bearing failure.