CFM56-5B/P & CFM56-7B HPT Blade Update

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CFM56-5B/P &
CFM56-7B
HPT Blade
Update
September 2001
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 2
Agenda
• Status of HPT blade shank cracking investigation
• Status of HPT blade airfoil separation
investigation
HPT Blade Shank
Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 4
HPT Blade Shank Cracking
• CFM56-5B6/2P IFSD
- November 2000
- Contained
- TSN / CSN = 9027 / 8745
- HPT Blade separated in blade shank
- HPT Blade PN 2002M52P04
- One other shank separation due to secondary damage
- Other blade airfoils separated due to secondary damage
Event Description
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 5
CFM56-5B/P & CFM56-7 Fleet (Swissair Corrected 9/6/01)
0
100
200
300
400
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0
1000
2000
3000
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5000
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9000
Cycles Since New
Number of Engines CFM56-5B/P
CFM56-7
CFM56-5B/P Cumulative Cycles: 2,989,943
CFM56-7 Cumulative Cycles: 4,690,173
Blade Common to CFM56-5B/P & CFM56-7
• No additional shank separation events
– 2915 engines and growing
–Over 7.5 million cycles
Event
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 6
• HPT blade is a single crystal N5 material, with an
aluminide internal coating
- Coating reduces oxidation/corrosion
- Three coating processes used
- All three coating processes within specification
- Coating thickness correlates with process
• Coating thickness affects LCF initiation
- Laboratory bar testing
- Thinner coating better
• Cracking initiated at high stress location
- Cooling cavity transition
Background
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 7
Cross Sectional View of Cooling Cavity
Local stress
riser at transition
0.420 inch (10,7 mm)
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 8
Metallurgical Investigation
• Initiated at mid-cooling passage
– Initiation / propagation in Low Cycle Fatigue (LCF)
– Transitioned to crystallographic fatigue
– Shank geometry common to all 2002M52P04 through
P14 blade part numbers
Crack
Location
Cross sectional
view of cooling
cavity
Primary blade
Separation
Secondary blade
separation
(Tensile overload)
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 9
• Nine engines removed to sample high-cycle blades
– Five CFM56-5B/P (up to 7599 CSN)
– Four CFM56-7B (up to 9050 CSN)
– Two of the three coating processes represented
- Limited data from second process
- Blades from third process too young for meaningful data
• Findings
– Approximately 3600 blades inspected
- Sampling engines plus routine shop visits
- Visual, eddy current, and metallurgical
– 141 blades have been found with shank cracks
- All cracked blades from process that yields thickest coating
- All cracks detected using Eddy Current probe & verified by cut up
Field Investigation
Cracking Not as Severe as Originally Estimated
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 10
• Test Program
• Blade Design Changes
• Blade Rework
• Field Recommendation
The Next Steps
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 11
The Next Steps - Extensive Test Program
• Component (Whirligig) Test
– Accelerated cyclic aging
- Blades selected to test sensitivity to coating process
– Test terminated
- Completed 6,849 cycles
- No internal shank cracks
- Blade separation related to test setup
- Ambient pressure test conditions not representative of
in-service loading at dovetail min-neck area
• Factory engine test planned - 4Q01 thru 2Q02
– Mix of field returned high cycle blades and redesign blades
– Data to supplement field data
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 12
• Interim action taken on new production blades
– PN 2002M52P14 blade released
- CFM56-5B/P SB 72-0400
- ESN Intro.: 575-233 and up
- CFM56-7B SB 72-0337
- ESN Intro.: 889-505 and up
888-477, -496 through -497, -503 and up
– Thinner internal coating in shank area
• PN 1957M10P01 to be released
– Same coating process as P14 blade
– Redesigned internal casting geometry to reduce stress
– Service Bulletin 1Q02
The Next Steps - Blade Design Changes
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 13
The Next Steps - Blade Rework
• CFM investigating feasibility
- Inspect for internal cracking
- Strip process to remove internal coating
- External coating rejuvenation/tip repair
- Re-identify to new part number
• Estimate 2Q02 availability
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 14
The Next Steps - Recommendations
• No change to current maintenance recommendations
– No on-wing inspection possible (internal coating)
– At SV process per ESM and applicable SB’s
• Update on field findings and metallurgical evaluation
to be provided 1Q02
– Continue to evaluate blades returned from routine shop visits
– Continue detailed metallurgical evaluations of blades
- Obtain experience with the other coating processes
• Establish field recommendations based on field
returned blade findings
- Coating process
- Engine model / rating differences
- Data supplemented by factory engine test
HPT Blade Shank Cracking
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 15
Update on Field Findings and Recommendation 1Q02
Summary
• HPT blade shank separation on 5B/P engine
– Internal coating and shank internal geometry contribute to
crack initiation
– One event in over 7.5 million cycles
• Redesign blades
– Thinner internal coating - available
– Thinner internal coating with redesign casting contour 1Q02
• Field recommendation for existing blades
– Cracking not as severe as original estimates
– Continue evaluating high time blades from service
– Determining blade rework feasibility
HPT Blade Shank Cracking
HPT Blade Airfoil
Separations
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 17
Events
HPT Blade Airfoil Separations
• Four airfoil separation events, one CFM56-5B/P, three CFM56-7B
– Time, cycle and thrust ratings vary
– All engines were first run
Event date Model ESN Rating TSN CSN Part Number
May 2000 -7B 875-256 B22 5057 3265 2002M52P05
Nov 2000 -7B 874-163 B24 6401 6164 2002M52P05
Feb 2001 -7B 876-561 B26 769 1006 2002M52P11
Jul 2001 -5B/P 779-384 B3 1567 758 2002M52P05
• Events have similar overall characteristics -5B/P -7B
– Airfoils separated just above platform  
– No evidence of abnormal operation unknown 
– No evidence of combustor involvement investigating 
– No source of fatigue stimulus identified investigating 
– No evidence of manufacturing related cause investigating 
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 18
HPT Blade
Airfoil
Separation
Rupture
Tensile overload
LCF
HCF
HPT Blade Airfoil Separation
Eliminated
Probability
Potential Separation Mechanisms Scenarios
Low
High
Medium
• Pre existing trail edge root cracks
• Material pedigree
• Coating impact (internal cracks)
• Local stress exceeds material capability
• DOD/FOD
• Loss of cooling flow
• Plugging in blade
• Plugging in inducer
• Loss of retainer sealing
• Material pedigree
• Pre existing cracks/missing material (frequency shift)
• Material pedigree
• Coating impact (internal cracks)
• Loss of damping
• High mean stress
• Vibratory stimulus
• HPT nozzle area
• Combustor profile/pattern
• Fuel staging
• Fuel nozzle flow
• LPT nozzle area
• TBV scheduling
• Secondary flow circuit
HPT Blade Airfoil Separations
CFM CFM56-5B & -7 HPT Blade Update Proprietary information Page 19
• Blade frequency check - complete
- No change from original certification
• Telemetry engine test (vibratory stimulus
source)
- Instrumented HPT blade and secondary air system
- Test underway, results due at year-end
Investigation Status
HPT Blade Airfoil Separations

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