Acoustical Panel Screws Presenter CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 2 First Step: EIS - 1997 • Forward acoustical panel bolt liberation - Fan blade, panel & OGV damage • Inappropriate panel assembly procedure at production level - Bolt torquing value - 7.5 to 8.5 Nm instead of 9.5 to 10.5 Nm - Lower than -5A model - Assembly tool speed - 600 rpm instead of 200 rpm CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 3 • Corrective actions - Improved values for bolt torquing sequence - Forward & mid panel bolts: 9.5 - 10.5 Nm / 200 rpm - Introduction at production level - ESN779-282(DAC)&779-273(SAC) - SB 72-213 issued, Jan 98 - At A or C-check opportunity and/or at shop level - One time inspection and re-torquing - AMM & ESM 72-23-00 updated First Step: EIS - 1997 CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 4 • No post SB 72-213 reports from 1998 to 2000 • End of 2000, acoustical panel bolt looseness / liberation with secondary damage - Fan Blade L/E, OGV, panels, Fan abradable damage - Several engines complied with SB 72-213 Second Step: 2000 - 2001 CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 5 • Screw degradation scenario understood - Fretting initiation between screw head and panel cup - Cup and screw head subsequent wear - Panel beating against screw head - Cup, anchor nut and screw damage • No screw loosening Second Step: 2000 - 2001 CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 6 • Main contributor - lack of grease under screw head - Influences final tightening stress - SB 72-213 Rev 2 issued Oct. 2000 - Grease application on screw head and threads - Tool speed limitation: 200 rpm - Repetitive inspection - AMM updated - ESM to be updated 2Q02 Investigation Results Screw Head Lubrication Is Essential for Panel Tightening CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 7 • Vibration - CFM56-5B forward panel specificity: length / weight - Sensitivity to engine vibration - Bench test completed with instrumented panel - Vibratory environment explored - Forward panel more excited than mid panel - New bench test scheduled to define the best panel damping configuration - Results targeted April 2002 Investigation Results CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 8 • Assembly instruction reinforcement to ensure proper assembly - Grease application under screw head - Production process sheet modified according to best practices July 2000 - Introduced from SAC: 779870, DAC: 779975 Corrective Actions CFM56 Operators Conference – May 21 - 22, 2001 CFM Proprietary Data Unauthorized Disclosure Prohibited 9 • SB 72-213 rev 3, clarifies torque repetitive check procedure for all -5B engines - Targeted 2Q02 • Expected benefit from application of assembly best practices to be assessed - Based on operators’ findings at first “A” check - Evaluate efficiency and necessity to maintain SB 72-213 inspection - Evaluate design change - Focus Team early feedback: significant improvement from new assembly procedure • To date, no event reported on engines assembled with best practices Field Containment Plan作者: kinran 时间: 2011-6-4 23:04:29
