CFM Components & Accessories Accessory GearBox Links Bearing Wear

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CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 1
Accessory GearBox Links
Bearing Wear
Components & Accessories
CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 2
Background
• Several reported AGB links bearings severely worn
on CFM56-7B engines
 CFM56-3 also affected to a lesser extend
• 3 parts involved:
 upper non-adjustable link:
 bearings damaged on both ends of the
link
 no measurable longitudinal displacement
 “worst case” highly worn bearing
 axial 3-5 mm [0.118” to 0.197”]
 not received yet
 lower non-adjustable link:
 no wear reported
 adjustable link:
 similar axial wear reported on 30% of
inspected engines
Components & Accessories
AGB Link Wear
Axial
CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 3
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Self Lubricating
Feature
Wear
longitudinal
axial link
Spherical
Bearing
External Link
inner surface
Components & Accessories
AGB Link Wear
CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 4
Engineering assessment
• Phenomenon/ root cause:
 wear induced by engine vibration
 Link retaining feature loaded by link weight
 Self lubricating feature degradation
• Consistency of root cause:
 Angular work combined with link weight leading to Bearing degradation
 horizontal upper non-adjustable link most damaged
• Effect of wear:
 effect on AGB position acceptable
 heavy bearing axial wear may lead to contact between Link, and AGB
Hinge Fitting wear (not experienced yet)
– Axial wear to be limited to 1.3 mm [0.051”]
 longitudinal wear would impact AGB mounting system vibrations
damping capability
– Longitudinal wear to be limited to 0.2 mm [0.008”]
Components & Accessories
AGB Link Wear
CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 5
Corrective Action Plan
• Further investigations on “worst case”
 When parts received Oct, 02
• AMM limits proposal
 Any amount until the Link FWD edge is in contact with the ABG Hinge Fitting
– Maximal authorized wear covered by the Link / Fitting gap
– Measurement in this environment seems not easy
 If the link in contact with the Hinge an overserviceability of 500 cycles is
allowed
• Short term containment Field Plan
 Temporary repair by implementation of RTV
– 3 RTV types are proposed depending of the available curing time
– RTV injection between link and AGB Hinge Fitting to set the link in the proper
position and support it’s weight under vibration
– Implementation through CDR (Already applied in field)
Components & Accessories
CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 6
Corrective Action Plan (cont’d)
• Mid term Field Plan :
 Fit check exercize at the training school was performed to validate the Upper
Link replacement on-wing
– Different Upper Link dimensions have been tested
 Drawing Link longitudinal tolerance is +/- 0.3 mm [+/- 0.012”]
 Mechanic was able to install a link within 0,2 mm [0.008”] of the
removed one.
 Impossible to install a link at the Max. tolerance value
– The replacement of the link on-wing will not be implemented in the AMM
 Link Repair
– Bearing replacement procedure in process
– will be a generic repair for all bearings December, 02
Components & Accessories
AGB Link Wear
CFM56-7B WTT Meeting - September,26-27/2002 CFM / Boeing Proprietary Information - Unauthorized Disclosure, Use, or Export are Prohibited 7
Corrective Action Plan (cont’d)
Final fix Plan
 Different solution under study
– Removable Spherical Bearings
 Review with the proposed vendor completed
 One bearing definition has been identified
 Installation study to be performed
– Introduction of a Teflon washer
– Introduction of a bigger Spherical Bearing
 Final Fix selection December,02
Components & Accessories
AGB Link Wear

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CFM Components & Accessories Accessory GearBox Links Bearing Wear