CFM56-7 N1 Vibration

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CFM56-7
N1 Vibration
Contents:
• Qualification and
Production Experience
-Development and
Certification
-Production Engine Test Cell
• In-Service Vibration Team
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 3
CFM56-7
Vibration Signature for FAN Unbalance
FFCC
0.00
5.00
10.00
15.00
20.00
25.00
30.00
0 1000 2000 3000 4000 5000 6000
LP Speed - RPM
Displacment - Mils DA
Endurance Dwell
107 cycles, 32 hours
27 mil (+5 units)
Typical production level
Maintenance
Guidelines
Test Cell Limit
0
AVM Units
5
N1 Vibration Endurance with
Full 737NG Propulsion System
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 4
CFM Production - Fan Trim Balance
• Vibration levels during production acceptance test
- #1Brg, FFCC max LP vib level < 2.5 mils prior to delivery
- Additional balance performed to achieve low level (~1 mil) at
Boeing flightline
• Fan trim balance conducted by recording LP vib amplitude
& phase response during vib survey (slow accel, decel) or
with steady-state dwell points
• Balance achieved by spinner screw weight changes
- 36 holes in aft spinner, 7 different screw sizes
- Provides full range of adjustments
In-Service
Vibration Team
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 6
N1 Vibration Team Objective
• In May 2000 CFM/Boeing and six airlines completed a
study of in-service N1 vibration
• 737NG operators reported increasing N1 vib levels and/or
N1 vib shifts following trim balance.
• Operators also expressed concern on maintenance
guidelines and recommendations
• CFM reviewed the engine vibration levels, balance history,
and pilot / maintenance crew reports for a fleet size of 240
engines, comprising ~2000 flight legs during a four month
period.
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 7
In-service N1
Vibration
Levels > 1.5
AVM Units or
Tactile Vibes
and Not
Resolved With
Current AMM
Procedures
Manpower
Vibration
Measurements
Flight
Environment
LP Rotor
Hardware
HIGH Ranked Causes
Cause & Effect Analysis
What is about ….
Fan Blade Seating
Delivery Vib Levels
Crew Training
# Engine Cycles
ACARS Data
Collection
LPT Blade Loss
Icing
Balance
equipment Wide Chord Blade
Flight Crew
Reports
Airplane
Delivery
Platforms
Engine thrust rating
AMM
Procedures
Guidelines
FOD
# Engine Hours
Platform Seals
Blade
Lubrication
Trim Balance
Method
Flightdeck
display
AVM Data
Collection
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 8
N1 Vibration Status
Background
• Vibration variation impacts trim balance effectiveness
• N1 Vibration is not common but has been reported inservice
- Customers perform trim balance using AVM / relube at ~2 units
- Effective in reducing vibration to less than 1 unit
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 9
N1 Vibration Status
• Identified 2 prime factors for N1 vibe variation
- Vibe variability due to blade / disk seating
- Improved with G-n paste lube, introduced 05/00 in production
- CESM 005 provides lubrication recommendation for N1 vibes
- Vibe variability due to blade axial movement in disk
- Creates a dynamic unbalance couple
- Engine sensitive to dynamic unbalance couple
- Elastomer buttons introduced to retention ring - May 2001
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 10
Elastomer Buttons
Rubber
Button
Aft View of Retention Flange
Disk
Spacer
Retention
Flange
Blade
Platform
Retention
Ring
• Button installed in
current holes in retention
ring - limits blade axial
travel
- Easily retro-fittable
• S/B 72-325R1 introduced
Elastomer Buttons - May
2001
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 11
N1 Vibration Team Conclusions
CESM 007 Recommendations:
• Schedule fan trim balance when N1 vibration
trend levels are above 1.5 – 2.0 units
• Lubrication fan blades and disk slots provides
benefit for reducing engine vibration levels. The
re-lubrication method / timing is documented
through CESM 005.
• The recommended format for reporting N1
vibration related issues is included as an
attachment to CESM 007.”
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 12
Summary of Fleet Experience
• Typical engine vibration level at airplane delivery ~ 0.5 unit
• N1 vibration level in-service average ~ 1.1 unit with various
levels of trim balance activity
• N1 vibration level increase 0.4 unit for every 2500 hrs
(on average)
• SAGE cruise trend data ~ 35% lower than max AVM
flight history data levels
• Threshold for crew reports of increased ~2 units
vibration and/or airplane tactile vibration
• Typical vibration reduction from AVM trim ~ 1.0 – 1.5 units
balance
• Engines identified with difficulty to be maintained 3 engines (vib level increased
within ~
at low vibration levels 1 month after fan balance)
• Fan blade re-lubrication Provides benefit in reducing /
maintaining N1 vibration
levels
LP Vibration Team Findings
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 13
Other Contributors to Vibration - Fan Blade Platform
Balance
Weights vary in
size
Not All Fan
Blade
Platforms
require a
Balance Weight
•The loss of fan blade platforms seals or balance weights can contribute to
engine unbalance
•Field experience revealed an immediate 1 to 2 unit increase N1
indicated vibration when a balance weight or platform seal is missing
•Maintenance manual revised recommending platform seal
lubrication before installation
Platform Seals
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 14
• Currently evaluating benefit of 2 plane trim on CFM56-7B
- Fan trim balance performed to reduce N1 engine vibe levels and
N1 audible noise and tactile vibration (A&T)
- Currently assessing benefit of 2 plane trim balance for N1 A&T
levels
- 2 plane trimmed (as req’d) at CFM starting December, 2001 GE 888-
769, SN 889-854 and up
- Boeing Flight line evaluation in progress
- CFM All OPS Wire issued Dec 2001
- S/B 72-0347R1 introduced LPT Stage 4 clips
- Test Cell Experience
- TRF Vibes 1.69 => 1.28 mils avg, LPT unbalance 250 => 100 gm-cm
avg (75% engines receive clips)
2 Plane Trim Balance Evaluation - Production Engines
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 15
• It is not intended that Operators will perform two plane
trim balance in-service
- CFM56 experience shows that CFM56-3 operators did not
perform two plane trim balance in-service.
- Two plane trim balance on the CFM56-7B is more complicated
due to the longer exhaust nozzle making clip installation more
difficult
• There is no action recommended or required for inservice
CFM56-7B engines delivered with LPT
balance clips
- If clips are observed to be missing in-service, it is not
necessary to reinstall the clips
- If clips are observed on an LPT at overhaul, it is recommended
to leave clips installed unless LPT module balance is to be
conducted
2 Plane Trim Balance - In-Service Engines
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 16
Summary
• CFM56 Production engines are delivered with
vibration levels less than 2.5 mils DA - typically ~ 1.0
mils DA
- Engine durability demonstrated at vibration levels over 5 units
• N1 Vibration team formed which included six airline
customers
- Conclusions from the team are published in CESM 007
- Performing periodic trim balances in addition to lubricating
fan blade roots and fan disk slots is a effective method for
retaining low LP vibration levels
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 17
Summary (Continued)
• Additional actions taken:
- Introduced new fan blade lubrication into production process
May 2000 (GN Paste)
- Introduced elastomer buttons into production May 2001 to limit
fan blade axial travel
- Improves N1 vibration variation
- Evaluating the benefits of 2 plane balancing on production
engine deliveries at Boeing flight line to improve airplane
comfort
Engine Vibration Is Not Being Reported
As an In-service Issue
Back-up
Material:
Engine Airborne
Vibration Monitoring
System
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 19
CFM56 Vibration Sensors
FFCC
(-7, -5C)
TRF
(-2,-3,-5A,-5B
)
CFM56-7B
# 1 Brg
(all)
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 20
737 Classic vs NG
General Info Classic NG
Engine CFM56-3 CFM56-7B
Fan Blade Design Mid Span Shroud Wide Chord
Engine Bearings 1B,2R,3B,4R,5R(ODB) Same, but also 3B+3R
Isolators Fwd & Aft Mts, T/R None
AVM Scale 0-5 Units (20 mils DA) Same
Vib Sensors # 1 Brg and TRF #1 Brg and FFCC
N1 Vibration
Engine Balance Provision FAN and LPT Same
Flight Line Trim Process FAN/LPT trim with in-flt data Fan trim using in-flt data
N1 Vibe Peaks Hold and Climb (max) Same
Vibe Endurance 21 mils da (+5 units) 27 mils da (+5 units)
Maintenance Levels 7-10 mils da (3 units) Same
Advisory Levels 14-15 mils da (4 units) Same
Test Ship Limit 2.5 mils da 2.5 mils da
Test Avg Level 1.5 mils da 1.0 mils da
Overhaul Shop Limit 2.5 mils da 2.5 mils da
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 21
CFM56-7 LP Vib Response Characteristics (before trim balance)
* Response peaks at 3000 rpm and 4200 - 5200 rpm (similar to CFM56 family)
* Engine easily fan trim balance to low levels for improved comfort
#1Brg
FFCC
Peak at ~3000 rpm
Near hold power
Peak at 4200 - 5200 rpm
Climb and cruise range
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 22
737NG / CFM56-7 AVM Functions
• AVM System Functions
- Display engine vibration 1/rev N1 and N2 levels in flight deck
- Record engine vibration flight history data
- Record engine LP rotor balance data, calculate trim balance solutions
• AVM System Description
- 2 accelerometers per engine (#1Brg and FFCC)
- LP and HP rotor speed signals, each engine
- 1 AVM signal conditioner per airplane
- Two vibration indicators in flight deck
- 1 indicator for each engine
- CDS displays 1 value, max level (in units) of 4 parameters
- Max of #1Brg or FFCC, fan/rev or core/rev vib level
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 23
AVM and AMM Terminology
• “Fan” Number 1 Brg sensor N1 Vibration
- Sensitive to fan unbalance
• “HPC” Number 1 Brg sensor N2 Vibration
- Sensitive to HP rotor unbalance
• “HPT” FFCC N2 Vibration
- Sensitive to HP rotor unbalance
• “LPT” FFCC N1 Vibration
- Sensitive to fan and LPT unbalance
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 24
AVM Balance Method
• AVM Monitors #1Brg, FFCC response continuously
during flight
• Stores up to 6 balance data points based on speed ranges,
stability criteria
• Stored balance data used post-flight to provide balance
solution
• AVM box provides recommendations for spinner wieght
change to balance engine
6 AVM defined speed ranges for
balance data collection
Typical #1Brg in-flight response
AVM stored balance data
1000 2000 3000 N1 Spe4e0d00 5000
1.2 327 1.1 5 0.9 63 0.8 53 0.5 57 0.7 49
1.6 20 1.5 36 1.1 82 1.2 64 0.8 19 0.5 51
Speed Range
%N1
Fan (mils / degrees)
LPT (mils degrees)
1 2 3 4
70 65
5 6
95 90 85 80
Location Remove Install
27 P02 P05
28 P05 P06
29 P02 P06
32 P07 P05
AVM provides
straightforward
instructions for balance
screw changes
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 25
737NG LP Vibration AVM Scales
0.0 1.0 2.0 3.0 4.0 5.0
AVM Scalar Units
#1Brg -- mils DA
#1Brg (-113, -213)
#1Brg (-114)
0.
5.
10.
15.
20.
0.0 1.0 2.0 3.0 4.0 5.0
AVM Scalar Units
FFCC -- mils DA FFCC (-113, -
213)
FFCC (-114)
• AVM scales changed with introduction of -114 AVM (Oct ‘99)
• Provides same scaling for both sensors for LP vibration
• 1 unit = 2.5 mils DA (CFM ship limit at production, overhaul)
• At recommended maintenance levels
•Same scaling for #1Brg (-113, -213, -114)
•Slightly more conservative for FFCC with -114
• No change in max scale values ( 5 units = 20 mils DA)
• Refer to Boeing Service Letter 737-SL-77-015-C for additional AVM details
0.
5.
10.
15.
20. Typical
delivery
levels
Recommended
maintenance
levels
Typical
delivery
levels
Recommended
maintenance
levels
CFM56 Operators Conference – May 21 - 22, 2002 CFM Proprietary Data Unauthorized Disclosure Prohibited 26
AMM Procedures - Current Vibration AMM Recommendations
1- Vibration Guideline AMM 71-00-00
• If indicated vibration levels are between 3 and 4 units : action at airline policy
• If indicated vibration is above 4 units with other parameters Normal perform the
following:
a/ Routine inspection FIM 71-05 (FOD…)
b/ AVM download: engine removal if vibs source is N2
engine trim balance if vibs source is N1
note: refer to Boeing Fault Isolation Manual Chapter 71-05
2- Maintenance Manual Current trim balance method
• The Three shot plot procedure AMM 71-00-00 ( test 14A)
Preferred method
• The On Board Procedure AMM 71-00-00 ( test 14B)

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