CFM56-5B No 3 Bearing Review for Alitalia

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CFM56-5B No 3 Bearing Review for Alitalia
Pete Gruber
CFM56 Product Support Engineering
October 3, 2002
CFM56 No. 3 Ball Bearing Experience
• No 3 Bearing Reliability
– CFM56-5B Reliability
– CFM56-7B Reliability
• CFM56 Ball Cracking/Spalling
– Winsted Non-Tumbled Population
• CFM56 Bearing Skidding Investigation
• ESN 575-175 UER Findings
• ESN 779-129 IFSD Investigation
• Summary
CFM56 No. 3 Ball Bearing Reliability
September 2001 thru August 2002
Summary of #3 Bearing failure rates on all CFM56 Engine programs
No. 3 Bearing reliability staying at the same level over last 1-2 years
2001-2002 Bearing Failure Modes:
• CFM56-3 Hard Particle Contamination
– Control Program in place to control IFSD’s per S/B 72-923
• Ball Residual Tensile Stress - Ball Cracking
– UER’s from ball cracking - Corrective Actions Implemented
• Ball Spalling - Other Manufacturers and Lots
• Ball Skidding – Recently observed on –5B/-7B
UER's IFSD's Hours UER Rate IFSD Rate
CFM56-2A 0 0 0.123 0.000 0.000
CFM56-2B 1 0 0.747 1.339 0.000
CFM56-2C 0 0 0.321 0.000 0.000
CFM56-3 8 3 9.484 0.844 0.316
CFM56-5A 0 0 2.359 0.000 0.000
CFM56-5B 4 1 2.674 1.496 0.374
CFM56-5C 2 0 3.433 0.583 0.000
CFM56-7 3 1 5.915 0.507 0.169
Total 18 5 25.057 0.718 0.200
Note: Rates are per Million Engine Flight Hours
Continued good reliability
Last UER was in June, 1996
Recent events under investigation
Overall excellent reliability
M50 Bearing
Recent UER’s – 2 of 3 were Alitalia
– Two caught via Electronic Chip Detector
• Both of these failures show signs of skidding
– One Failure was an IFSD
• Failure investigation in progress
CFM56-5B No. 3 Ball Bearing Reliability
CFM56-5B No. 3 Ball Bearing Reliability
12 Month Rolling Average
0.000
0.500
1.000
1.500
2.000
2.500
3.000
J-98
M-98
M-98
J-98
S-98
N-98
J-99
M-99
M-99
J-99
S-99
N-99
J-00
M-00
M-00
J-00
S-00
N-00
J-01
M-01
M-01
J-01
S-01
N-01
J-02
M-02
M-02
J-02
Date
Failure Rate (Events per Million EFH)
UER Rate
IFSD Rate
EIS March, 1994.
No bearing failures prior to January, 1998
Current UER Rate - 1.518 UERs/MEFH
Current IFSD Rate - 0.379 IFSDs/MEFH
12 Total Bearing Failures in 8.59
MEFH/5.51 MEFC since Entry into Service
IFSD Rate is Improving
Have experienced failures from different
failure modes
– Ball Cracking - Residual Tensile Stress
– Single Ball Spall - Root Cause not
determined
– Ball Skidding - Very recent finding
CFM56-5B Failures since EIS
Engineering Team working to understand recent ball skidding experience
Event Date
Prod
or
O/H ESN Customer
IF SD
UER
Brg
TSN
Brg
TSV Bearing P/N Brg S/N
Engine
Delivery
Date Last MCDI Oil Type
Win sted
Po p u latio n
Investigation Findings
8-Feb-98 Prod 779-273 Leisure Air X X 3051 3051 1460M52P03 FCAA6326 May-97 28 Hours No No Root Cause Established
3-Feb-99 Prod 779-375China Eastern X 1792 1792 1460M52P03 FCAB1135 Jun-98 ECD Mobil Jet 2 Yes Residual Stress
12-Jun-00 Prod 779-465 US Air X X 4610 4610 1460M52P03 FCAB3909 Mar-99 ECD 2380 Yes No Root Cause Established
14-Nov-00 Prod 779-682 US Air X 2640 2640 1460M52P03 FCAB7702 Feb-00 ECD 2380 Yes Residual Stress
5-Feb-01 Prod 779-513 Iberia X X 4095 4095 1665M98P02 MDAGJ573 May-99 ECD Mobil Jet 2 No No Root Cause Established
20-Jul-01 Prod 779-573 US Air X X 3826 3826 1460M52P03 FCAB5476 Aug-99 ECD Visual 2380 Yes No Root Cause Established
25-Jul-01 Prod 779-721 Air Jamaica X 3621 3621 1460M52P03 FCAB8097 May-00 ECD Yes Residual Stress
11-Aug-01 Prod 779-968 Sabena X 2155 2155 1460M52P03 FCAB9910 Oct-00 ECD Mobil Jet 2 No Ball Crack
22-Dec-01 Prod 779-740 Air 2000 X 1732 1732 1460M52P03 FCAB8104 May-00 ECD Yes Residual Stress
3-Apr-02 Prod 575-175 Alitalia X 1318 1318 1665M98P02 MDAJC205 May-02 ECD No Ball Skidding
11-Jun-02 Prod 575-902 Finnair X 916 916 1665M98P02 MDAJN696 Jan-02 ECD No Ball Skidding
30-Jul-02 O/H 779-129 Alitalia X X 3612 3612 1460M52P03 FBGE3623 N/A ECD No NEED TO CONFIRM #3 as ROOT CAUSE
Three low time failures
– Two caught via Magnetic Chip Detector
• One UER show signs of skidding
• One UER for M50 – Single Ball Spall
– Not from Winsted Non-Tumbled Population
– One Failure was an IFSD
• Failure investigation in progress
• Strong evidence shows advanced stages of
skidding
CFM56-7B No. 3 Ball Bearing Reliability
Overall No 3 Bearing Reliability excellent
5 Total Bearing Failures in 14.96 MEFH/7.80
MEFC since EIS
Recently experienced ball skidding on two
events – Currently under investigation
Recent CFM56-7B Failures
Engineering Team working to understand recent ball skidding experience
0.000
0.250
0.500
0.750
1.000
J-01
F-01
M-01
A-01
M-01
J-01
J-01
A-01
S-01
O-01
N-01
D-01
J-02
F-02
M-02
A-02
M-02
J-02
J-02
A-02
Date Quantity of #
3
Bearing Failures/MEFH
CFM56-7B No. 3 Ball Bearing Reliability
12 Month Rolling Average
Current UER Rate - 0.507 UERs/MEFH
Current IFSD Rate - 0.169 IFSDs/MEFH
UER
IFSD
Event Date ESN Cust
IFSD
UER
Brg
TSN Last MCDI Oil Type
Winsted
Population
Investigation Findings
17-Dec-01 877-205 Korean X X 3262 424H/377C 2380 No Ball Skidding
1-May-02 889-331 GOL X 3136 Normal MCD Insp Aeroshell 560 No Ball Skidding
5-Jun-02 877-419 Ryan Air X 5527 Normal MCD Insp Mobil Jet 254 No
Single Ball Spall w ith Ball
Crack - Root Cause under
Investigation
37 36
28
32
62
85
113
131
97 99
95
80
18 17
13
7 7
1 3
0
0
20
40
60
80
100
120
140
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
11000
12000
13000
14000
15000
16000
17000
18000
19000
20000
Time Since New (Hours) Quantityof EngineswithWinstedNon-TumbledBearings
.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
Distribution of Winsted Non-Tumbled Ball Population vs
Cumulative Percentage of Winsted Ball Cracking
Cumulative Percentageof Bearing Failures
Frequency
Cumulative %
• The CFM56 engine program has had
eight UER’s for Ball Cracking due to a
change in the manufacturing process -
Non-Tumbled Balls
– Detected via MCD inspection and resulted
in UER’s (no IFSD’s)
– Ball Cracking is due to Residual Tensile
Stress on the surface of the ball
• Last Winsted UER in December 2001
CFM56 No. 3 Ball Bearing Reliability
Ball Residual Tensile Stress
Winsted
Non-
Tumbled
Bearings
Cumulative
MEFH
IFSD
(all)
UER
(Residual
Stress)
UER
(Other
Causes) Total
CFM56-3 125 1.03 1 4 8 12
CFM56-5A 60 0.49 0 0 0 0
CFM56-5B 221 1.47 2 4 2 6
CFM56-5C 88 1.01 2 0 3 3
CFM56-7B 467 3.32 1 0 2 2
Total 961 7.33 6 8 15 23
Current population of Winsted Non-Tumbled Ball Bearings
Fleet Status as of 9-17-02
77% greater than 6000 hours
• Ball Cracking caused by High Tensile Residual
Stress
– Process Change at Winsted Ball Mfg Co. 4Q, 1996
– 1018 Bearings Total - ~960 still in revenue service
• Corrective Actions Implemented
– Residual Stress Specification Implemented 12/00
– Heat Treat and Improved Tumbling Process are now VSE
controlled at all vendors
• Weibull analysis supports Infant Mortality
Failure Mode
– ~88% of all failures occur in first 6000 hours
– ~80% are greater than 6000 hours TSN
• Ball spalls propagate slowly due to random
tracking nature of the ball
Normal MCD Inspections aarreeaaddeeqquuaatteettoopprreevveennttIIFFSSDD’’ss
• CFM56-5B 575-175 was removed for material found
on MCD in April’02
• Investigation showed damage consistent with skidding
• CFM56-5B 575-902 showed same type distress
• Two CFM56-7B bearings have shown similar distress
• One CFM56-5A operator found skidding damage in ’96
• No root cause determined, no CFM56 finding since
Action Plan
Team launched to investigate recent failures due to skidding
Field Events
Skidding Description
Background
Team Launched to Determine Root Cause
• TOPS8D initiated
• Field failure teardown investigation
• Assess operator flight operational experience
• Evaluate bearing condition at overhaul shops
• Review rotor thrust and design configuration changes
• All bearings experience slip between the balls and
inner race. High slip rates occur at/near crossover
• Skidding damage occurs when there is metal-to-metal
contact when the bearing is experiencing a high slip
rate
CFM56 No. 3 Ball Bearing Skidding
Event Date
Eng
Mod ESN Customer
IFSD
UER
Brg TSN
Engine
Delivery
Date Last MCDI Oil Type
Investigation
Findings
17-Dec-01 7B 877-205 Korean X X 3262 Jan-00 424H/377C 2380 Ball Skidding
3-Apr-02 5B 575-175 Alitalia X 1318 May-02 ECD Ball Skidding
1-May-02 7B 889-331 GOL X 3136 May-02 Normal MCD Insp Aeroshell 560 Ball Skidding
11-Jun-02 5B 575-902 Finnair X 916 Jan-02 ECD Ball Skidding
• Event Date: 4/3/2002
• Engine Serial Number: 575175
• Engine Delivery Date: 5/1/2001
• AC Tail No: I-BIKF
• Pos: 2
• Narrative: ALITALIA HAS RECEIVED TODAY RESULTS FROM THEIR LAB.
MATERIAL IDENTIFIED IS M50NIL, FAILURE OF 63 ROLLER BEARING IS NOW
SUSPECTED.
• ETSN: 1329
• ECSN: 684
• AIRLINE: EUROFLY
• Aircraft: A320
• Model Code: 5B
• Model Series: B4/P
• Thrust: 027000
• Shop Visit Number: 01
CFM56-5B ESN 575-175 Investigation
Event Report
CFM56-5B ESN 575-175 Investigation
Metallurgical Findings
Introduction
A 3B bearing from a CFM56-5B operated by Alitalia was removed from service after chip indications were observed
on the electronic chip detector. The bearing (P/N: 1665M98P02 and S/N: MDAJC205) had accumulated 1318 hours
and 679 cycles since new. Figure 1 shows the location of the failure and the bearing in the as-received condition.
Conclusions
Root cause of the failure of the 3B bearing from Alitalia was believed to be the result of skidding damage. White
layer was also found on the aft inner race and on the balls further supporting skidding.
Hard particle contamination in the form of aluminum oxide and silicon oxide was also observed along the inside
wear path of the cage pockets. Silver and tungsten carbide contaminants were found within a spalled area on the aft
inner raceway. The deposited silver can possibly be attributed the silver plating of the cage pockets and the
tungsten carbide could possibly arise from the tungsten carbide coated journals on the FWD shaft. The detected
hard particle contamination would also tend to worsen the spalling damage.
Hardness, case depth, and microstructure for all bearing components conformed to the requirements set by the
engineering drawing.
CFM56-5B ESN 575-175 Investigation
Hardware Condition
Photographs showing distress to the outer raceway. A band of distress was observed along the entire circumference of the raceway
that was interrupted by spalation patches.
No 3 Bearing Outer Race
No 3 Bearing Balls/Cage
Banding on the Balls
Fwd Inner race of bearing
showed band of light distress
• Event Date: 7/30/2002
• Engine Serial Number: 779129
• AC Tail No: I-BIXO
• Pos: 2
• IFSD: E
• Narrative: DURING APPROACH ENG 2 ECAM WARNING OIL LOW PRESSURE WAS DISP LAYED.
GROUND MAINTENANCE REPORTED PARICULES ON MCD BEARING No.3 SUSPECTED. ENGINE
SENT TO LHT FOR INVEST
• ETSN: 14374
• ECSN: 9474
• AIRLINE: ALITALIA
• Aircraft: A321-100
• Model Code: 5B
• Model Series: B2
• Thrust: 031000
CFM56-5B ESN 779-129 Investigation
Event Report
• No ECD issues on engine prior to the IFSD (no chips on ECD)
ECD reported as operational at time of failure/subsequent shop visit
• No 3 Bearing on this engine was installed at last shop visit in December, 1999
Alitalia CFM56-5B ESN 779-129
IFSD 7-30-2002
0
20
40
60
80
100
120
140
1 20 39 58 77 96 115 134 153 172 191 210 229 248 267 286 305 324 343 362 381 400 419 438 457 476 495
0
500
1000
1500
2000
2500
3000
3500
4000
4500
N21
N22
OILP1
OILP2
OILT1
OILT2
OILQ1
OILQ2
ALT
Shutdown at 260
Oil Pressure Drop of 6-8 PSI ~ 60 Seconds prior to IFSD
Oil Temp Increase ~ 30-40 degrees C
corresponding with oil P drop
Oil Quantity remains constant throughout
CFM56-5B ESN 779-129 Investigation (cont)
DFDR Data from event
Working to understand why oil pressure loss 60 seconds before IFSD
CFM56-5B ESN 779-129 Investigation (cont)
Hardware condition
Forward Oil Nozzle Aft Oil Nozzle No 3 Bearing – Balls and Cage
Engine sent to LH for repair – Confirmed No 3 Bearing Failure
• Oil Nozzles damaged from failure (Normal condition)
• No 3 Bearing heavily damaged – Cage ruptured in multiple locations
• Hardware condition noted – very little metallurgically to determine root cause
• Lubrication Unit returned to vendor for investigation – heavily damaged
• CFM has requested Scavenge and Supply oil filters for analysis – not available
CFM56-5B ESN 779-129 Investigation (cont)
Hardware condition – IGB Assembly
Spring Housing shows abnormal oil/heat Forward Oil Nozzle location
pattern in area of oil nozzle
CFM56-5B ESN 779-129 Investigation (cont)
Hardware condition – No 3 Brg installed in Spring Housing
Outer Race Heavily Damaged
Spring Housing
• Non-Tumbled Ball Issue has driven reliability in the past
– Expect this issue to lessen with time - Infant Mortality Mode
• Ball Skidding new issue on the CFM56–7B/-5B engine program
– Engineering Investigation Team Currently Investigating for Root Cause
• Two Alitalia No 3 Bearing Failures in 2002
– Investigation reveals skidding on UER , unknown cause on IFSD
– Investigation continuing – Requesting flight data from customers experiencing
skidding distress on their bearings
• CFM will keep operators informed of findings as they become available
CFM56 No. 3 Ball Bearing Reliability
Summary
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CFM56-5B No 3 Bearing Review for Alitalia