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