Chris Leat

This proposed FAA AD is in response to an EASA AD 2009-0073R1 concerning the requirement to carry out inspections of HP Compressor Stage 1 to 4 Rotor Discs fitted to Rolls-Royce Trent 700, 700 and 800 engines and references Rolls-Royce NMSB 72-F964 rev 1. Unlike the EASA AD, and indeed the RR NMSB, the FAA AD does not use the "Refurbishment/Overhaul Levels" or "component at part piece level" as the trigger for carrying out the inspections but introduces the criterion of "the separation of pairs of major mating engine flanges" instead. For those operators who need to comply with FAA ADs, this definition will lead to the inspection being carried out at a more frequent interval than required by the EASA AD and specified in the reference Rolls-Royce NMSB both of which have been arrived at by engineering considerations and agreed analyses. Unless the intention is to increase the frequency of this inspection for US operators, could the FAA consider that the criterion for carrying out the inspection be revising in line with the state of design AD and the Rolls-Royce service bulletin either by reference to the Rolls-Royce Refurbishment/Overhaul level or by another method that will result is an equivalent inspection period.