GE Aviation

Subject: FAA Docket FAA-2010-0998 / Directorate Identifier 2010-NE-29-AD Dear Chris, GE Aviation, CF6 Engineering provides the following comments to the above referenced NPRM: • Compliance (LPT module definition) For purposes of this NPRM, the FAA should consider the Low Pressure Turbine (LPT) module definition as the Turbine Mid-Frame (TMF), LPT Stage 1 Nozzle, LPT Stator Cases and Vanes, LPT Rotor and Turbine Rear Frame. Separation of the TMF forward flange from the Compressor Rear Frame aft flange would define LPT module separation from the engine and require LPT stage 3 disk cleaning and inspection. • Cleaning the LPT Stage 3 Disk The FAA should consider adding the words “including the use of” in place of the word “using” in paragraph (f). GE does not consider a wet-abrasive blast alone is sufficient to clean the LPT stage 3 disk sufficiently to allow performance of the fluorescent penetrant inspection of the inner diameter of the forward cone body of the LPT stage 3 disk. The final sentence should read: “Clean the LPT stage 3 disk, including the use of a wet-abrasive blast to eliminate residual or background fluorescence.” • Ultrasonic Inspection of LPT stage 3 disk GE has developed an ultrasonic inspection (USI) technique and tooling which allow the inspection of the stage 3 disk forward spacer arm without piece-part disassembly of the LPT to facilitate (reference GE Service Bulletin 72-1309). Disassembly of the LPT at every LPT removal will increase the cost of the CF6-50 cost of ownership for global operators. The implementation of the USI will detect cracks in the forward spacer arm which might propagate during operation and would be a suitable alternative to the piece-part disassembly, cleaning and FPI of the forward of the forward spacer arm in many situations. The FAA should consider use of the USI procedure as an alternate to the piece-part FPI. Regards, David Budd GE Aviation