CFM56-7B VBV Teflon Pad Disbond
<P>**** Hidden Message *****</P> February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 1<BR>CFM56-7B VBV Teflon Pad<BR>Disbond<BR>CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, February 2002 WTT face to face or Export are Prohibited<BR>Background<BR>• About 20 cases of teflon pad disbonding reported to date<BR> Either seen on wing or at shop level<BR>– 1 to 4 pads disbonded or missing<BR> 50% cases leading to VBV position signal disagree fault occurrence<BR>– 150 hours time limited dispatch (short time dispatch fault)<BR>CFM56-7B VBV Teflon Pad Disbond<BR>Pad debonded<BR>CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, February 2002 WTT face to face or Export are Prohibited<BR>Root Cause Investigation<BR>• Lack of teflon pad bonding evidence on all parts returned from field<BR>• No manufacturing concession recorded<BR>• All defective parts coming from same sub-contractor source<BR>• About 1,700 pads potentially affected manufactured since EIS<BR> 440 engines potentially affected (87X 101 - 87X 541)<BR>Corrective Action<BR>• Original source canceled<BR>• New vendor process quality confirmed through shear test<BR>– New part = 34 Mpa<BR>– After wet aging (1500 hrs) = 22 Mpa<BR>– CFM spec. requirement = 18 Mpa<BR>Root Cause understood = Poor bonding quality from original vendor<BR>CFM56-7B VBV Teflon Pad Disbond<BR>February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 4<BR>Over-serviceability<BR>• Four pads mounted in pair, one @ 2 O’clock, one @ 8 O’clock<BR>• If at least one pad remain at each pair location<BR>-> serviceable, no time limit<BR>• If one pair missing or more<BR>-> serviceable up to shop visit<BR> To be introduced in the next AMM revision (Feb 2002)<BR>EEC Software logic<BR>• VBV position signal disagree fault maintenance message de-sensitized<BR> VBV fault threshold increased from fixed 4° to variable limit (function of<BR>VBV command)<BR>– Validated through engine test<BR> introduced in coming 7BN EEC software to be released in Apr 2002<BR>CFM56-7B VBV Teflon Pad Disbond<BR>February 2002 WTT face to face CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 5<BR>LH pair of<BR>two pads<BR>RH pair of<BR>two pads<BR>Aft looking Fwd<BR>CFM56-7B VBV Teflon Pad Disbond<BR>CFMI / Boeing Proprietary Information - Unauthorized Disclosure, Use, February 2002 WTT face to face or Export are Prohibited<BR>In-service Plan<BR>• No on-wing inspection needed<BR> Except for VBV fault troubleshooting per FIM<BR>• Inspection in shop of affected population recommended<BR>No action required if no pad disbonded<BR> 4 pads replaced / repaired if at least one found disbonded<BR>– Teflon pad removal requires fan minor module removal<BR>VBV Pad Repair<BR>• Repair bonding process has been developed and validated<BR> This repair does not require an industrial validation<BR>• First repair source (Le Piston Français) to be validated by Mar 2002<BR>CFM56-7B VBV Teflon Pad Disbond :victory: :victory: CFM56-7B VBV Teflon Pad Disbond
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