The FAA is superseding an existing airworthiness directive (AD) 2013-04-01 for all Rolls-Royce plc (RR) RB211-524 series turbofan engines. That AD currently requires removal and repair of certain thrust reverser units (TRUs) prior to reinstallation. This AD requires the same actions for an expanded population of TRUs and extends the compliance time for repairing certain TRUs. This AD was prompted by additional engineering evaluation of TRUs, as a result of a translating cowl gearbox stubshaft failure and subsequent repair. We are issuing this AD to prevent failure of the attachment rivets, which may result in release of the TRU from the engine.
DATES: This AD is effective March 8, 2013.