Summary
The FAA proposes to supersede an existing airworthiness directive (AD), AD 95-04-11, for Honeywell International Inc., (formerly AlliedSignal, Inc. and Textron Lycoming) ALF502L series and ALF502R series turbofan engines. That AD currently establishes stress rupture retirement life limits for certain third stage turbine discs used in conjunction with certain third stage turbine nozzles. This proposed AD would bring requirements forward and unchanged, from the previous AD for ALF502R series turbofan engines. Also, this proposed AD would establish new reduced stress rupture retirement life limits for certain part numbers (P/Ns) of third stage turbine disc and shaft assemblies installed in ALF502L series turbofan engines. This proposed AD would also require removing those same parts from service using a drawdown schedule. This proposed AD results from a report of failure of a third stage turbine disc and shaft assembly, leading to turbine blade release and separation of the exhaust nozzle. We are proposing this AD to prevent total loss of engine power, in-flight engine shutdown, release of turbine blades, separation of the exhaust nozzle, and possible damage to the airplane.