1. Aging Airplane Maintenance
Program Developments 1

2. Objective
To provide information regarding the latest
program developments to ensure the continuing
structural airworthiness of airplanes as they age.
2

3. Contents
• Background
• Recent Developments
• Widespread Fatigue Damage
• Aging Airplane Safety Rule
• CPCP NPRM
• CPCP Reporting AMOC
3

4. Aging Airplane Concerns
• As airplanes age
• Potential for fatigue cracking increases
• Corrosion may become more widespread and
significantly degrade fatigue performance
• Two or more types of damage in an area can
degrade fail-safe or damage tolerance capability
4

5. Aging Fleet Issues
• Economic and market conditions result in
operation of airplanes longer than anticipated
• Damage on high time airplanes highlighted aging
fleet structural concerns
• Horizontal stabilizer
• Fuselage skin
• Maintenance programs for an aging fleet must
address effects of fatigue and corrosion during
long term operations
5

6. Structural Maintenance Programs
• Maintenance Planning Data
• Aging Airplane Programs
• Supplemental Structural Inspections
• Corrosion Prevention and Control Program
• Mandatory modifications and inspections
• Repair Assessment Program
• Widespread Fatigue Damage Program (TBD)
• Service Bulletins
• Other mandated actions
6

7. Aging Airplane Program Developments
• Widespread Fatigue Damage
• Aging Airplane Safety Rule
• CPCP NPRM
• CPCP Reporting AMOC
7

8. Widespread Fatigue Damage (WFD)
• WFD is structural damage which is characterized by:
• The simultaneous presence of cracks at multiple
structural details, and
• Have sufficient size and density such that the
structure will no longer meet its damage
tolerance requirement
• There is a point in airplane operation where the risk
of uncertainties in structural performance and the
probable development of WFD increases
8

9. Limit of the Maintenance Program
• Concept of Limit of Validity (LOV)
• Threshold beyond which the airplane
maintenance program is not considered valid
• WFD requirements to be provided in model
specific documents
• LOV
• Inspections
• Modifications
9

10. Aging Airplane Safety Rule (AASR)
• Interim Final Rule and ACs published in Dec 2002
are result of activities called for by the “Aging
Aircraft Safety Act of 1991”
• Rule result of comments received from two
previous NPRM publications
• Further comments requested because 1999
NPRM was significantly modified
• Comment period extended to 5 May 2003
• Airplanes operated under FARs 121, 129, and 135
• Effective 8 Dec 2003
10

11. Rule Requirements, Paragraph 1
• Records Reviews
• Periodic review of maintenance records based
on airplane age
• Inspections of airplanes
• Focus on existing aging aircraft requirements
• Specified in FARs 121.368, 129.33 and 135.422
11

12. Records Review – Part 1
• On 8 Dec 2003, for airplanes
• Exceeding 24 years in service, 1st records
review must occur before 5 Dec 2007
• Exceeding 14 years in service but less than
24 years, 1st records review must occur
before 4 Dec 2008
• Less than 14 years in service, no later than
5 years after the start of 15th year in service
• For all airplanes, records review will be
repeated every 7 years thereafter
12

13. Records Review- Part 2
• Physical inspection of the airplane either by FAA
Administrator or Designee
• Accomplished in conjunction with the
maintenance records review
• Administrator will require notification 60 days
prior to date that airplane and its records will be
available for inspection
13

14. Rule Requirements, Paragraph 2
• Supplemental Inspections
• Require a damage tolerance based
maintenance program by 5 Dec 2007
• Affects airplanes operated under FAR 121,
129, and 135
14

15. Supplemental Inspection
• A damage tolerance based program must be in
place and operating with three elements which:
• Proactively inspects for damage to the as
delivered structure to maintain continued
airworthiness*
• Maintains continued airworthiness of a
repaired airplane
• Establishes a new or revised program for
areas of the airplane that undergo major
modification
*Repairs to areas affected by the SSID or ALI require damage tolerance
based maintenance programs
15

16. Supplemental Inspections
• For all Boeing products, programs will exist
• Pre-amendment 45 airplanes
• Service Action Requirements
• CPCP
• SSIP
• Repair Assessment Program
0Fuselage pressure boundary
• Post Amendment 45 airplanes
• Certification basis requirement
16

17. Comments on Rule
• Operators commented that existing Aging Airplane
Programs provide means of compliance
• FAA has interpreted additional issues and
responses that operators “must establish
damage-tolerance-based SSIPs or service-
history-based SSIPs, as applicable, for major
repairs, major alterations, and modifications to
structures not affected by the repair
assessment program, such as fuselage frames
and longerons, and wing and empennage
structures”
17

18. Other FAA Issues
• SSID programs on some 737, 747 models and
MD-80 have yet to be mandated
• Unknown number of “major” repairs and
modifications that may now require damage
tolerance based inspections
• Service Bulletins
• STCs
18

19. FAA SSID AD Standardization Review
• Public meeting on 27 Feb 2003
• FAA SSID Team made 8 recommendations,
including
0Assessment compliance time to 18 months
0Three step assessment process
• Relationship between SSID ADs and AASR
• Requirements for repairs, alterations and
modifications under these regulations
0Have damage tolerance based inspections
19

20. Effect on Boeing Models – Post-Amdt 45
• 757, 767, 777, 737-700C/900, MD-11, MD-90, 717
• Certification basis fulfills intent of the AASR
for damage tolerance based maintenance
programs
0All have SSIPs in form of Airworthiness
Limitation Instructions (certain models have
ADs for early L/Ps)
0All require damage tolerance based repairs
and modifications
20

21. Effect on Boeing Models – Pre-Amdt 45
• 707, 720, 727, 737-100 through –800*, 747-100
through -400, DC-8, DC-9, MD-80, DC-10
• Required by FARs to have a RAP
0Applicable only to fuselage pressure boundary
• Rule will require additional damage tolerance
based inspection program for structures not
addressed by RAP
* Except 737-700C
21

22. CPCP Reporting AMOC
• CPCP ADs required quarterly reporting of Level 2
and follow-up of Level 3 reporting on a quarterly
basis
• Corrosion reporting also required per FAR 121.703
• Boeing proposed that reporting corrosion per FAR
121.703 would fulfill the AD reporting requirements
• FAA concurred and issued an AMOC
• Separate reporting to Boeing no longer required
22

23. CPCP NPRM
• Released in Federal Register 3 Oct 2002
• Requires implementation of an FAA approved
CPCP within 2 years of rule effective date
• Applicable to FAR 121, 129 and 135 operators
• Baseline program to control corrosion so that
damage does not exceed Level 1
• Existing CPCPs will satisfy rule
• Comment period closed 1 Apr 2003
23

24. Summary
• Maintain continued airworthiness with
• An effective scheduled maintenance program
• Compliance with all mandated actions
• New rules are being established to apply damage
tolerance and corrosion programs to more of the
transport airplane fleet
• Maintenance program must be valid for extended
operations
• Structural maintenance activities will increase as
airplanes age
24

25. 2003 Structures Conference
Service Engineering
Damage
Tolerance
Programs Update
1
3/12/2003

26. Objective
Provide a status of regulatory changes and
Boeing’s support for damage tolerance based
inspection programs for in-production and
out-of-production airplanes
2
3/12/2003

27. Contents
• Background
• Requirements for Out-of-production Airplanes
• Requirements for In-production Airplanes
• Effects on Repairs
3
3/12/2003

28. Damage Tolerance Definition
• Damage tolerance is the ability to sustain
regulatory required loads in the presence of
damage until that damage is detected and is
repaired
4
3/12/2003

29. Damage Tolerance Principles
Ultimate load
Ultimate load capability
Deterioration due to restored after repair
Structural Strength
undetected damage
Damage detection
and restoration
FAR 25.571 load
requirement
Normal operating loads
Detection Period of service
period
5
3/12/2003

30. Regulatory Background
• FAR 25.571 contains design certification
requirements related to fatigue and durability
• Amendment 45 added requirements for structural
damage tolerance analysis
• Evaluate new structures on airplanes certified after 1978
• Establish inspections to ensure timely detection of
damage before structural capability is degraded below
regulatory prescribed limits
• Advisory Circular 91-56 issued in 1981
• Airplanes certified prior to Amdt 45 needed a structural
integrity program
0 SSID / SIP created as alternative to service life limits
6
3/12/2003

31. Certified Post-Amdt 45 Models
• 737 (new or modified major structure)
• -300/400/500 - engine struts
• -600/700/800 - engine struts and wing structure
• 737-700C/900 entire airframe
• 747-400 strut-to-wing attach structure
• 757
• 767
• 777
• MD-11
• MD-90
• 717
7
3/12/2003

32. Post-Amdt 45 Requirements
• Supplemental Structural Inspections
• Airworthiness Limitations Section in MPD
0737-700C/900, 757, 767, 777
0737-600/700/800
• L/P 1 – 714 subject to FAA rulemaking
• L/P 715 and on per Type Certificate Data Sheet
• Airworthiness Limitations Instructions (ALI)
in MRB report
0MD-11, MD-90, 717
• Selected structural details to be inspected at
specified thresholds
8
3/12/2003

33. Impact on Structural Repairs
• Post-Amdt 45 airplanes’ certification basis
requires repairs be damage tolerant
• Supplemental inspections may be required to
maintain damage tolerance characteristics
• Repairs to original PSE structure may interfere
with an existing MPD inspection
• Requires a damage tolerance assessment
(DTA)
• Repair assessment inherent in repair design
requirements
9
3/12/2003

34. Certified Pre-Amdt 45
• 707
• 727
• 737*
• 747*
• DC-8
• DC-9
• MD-80
• DC-10
* Except for structures added or modified after 1978
10
3/12/2003

35. Pre-Amdt 45 Airplane Requirements
• Supplemental Structural Inspections
• 707, 727, 737-100/200/200C, 747-100/200 (SSID)
• DC-8, DC-9, MD-80, DC-10 (SID)
0 Threshold based programs
0 Mandated by ADs
• Recent developments
• 737-300/400/500 SSID at FAA for approval
• 747 SSID revised (Rev. G)
0 Added –300/400/SR models
0 Eliminated candidate fleet
0 Approved as an AMOC to AD 94-15-18
11
3/12/2003

36. Pre-Amdt 45 Airplane Requirements
• Repair Assessment Program required by FARs
• 707, 727, 737, 747
• DC-8, DC-9, MD-80, DC-10
• Recent developments
• 737 RAP document Rev. C adds -300/400/500
models
0 Approved by FAA Feb 2003
12
3/12/2003

37. Damage Tolerance Assessment of Repairs
• Regulatory actions require that repairs to pre-
Amdt 45 airplanes be evaluated for damage
tolerance effects
• 707,727, 737 Classic, 747, DC-8, DC-9, MD-80,
DC-10
• Repairs to SSID / SIP structures
• Fuselage pressure vessel boundary
• DTA results will establish if alternate inspections
are required to maintain damage tolerance
characteristics
13
3/12/2003

38. Repair Assessment Program (RAP)
• FARs effective 25 May 2000
• Applies to repairs on the fuselage pressure
vessel boundary
• Guidelines documents provide procedures to
assess effect of repairs on damage tolerance of
original structure
• Operators incorporate into maintenance
programs
• Assessment threshold is 75% DSO
14
3/12/2003

39. Applying RAP to SSID DTAs
727, 737-100/200/200C
• Repairs to fuselage skin addressed by RAP may
also affect a SSID item
• RAP evaluation results can also fulfill SSID DTA
requirements
• Boeing submitted a proposal for application of
RAG inspections to repairs of specific SSID Items
• FAA issued letter allowing RAG documents as
AMOCs to paragraphs (e) and (g) of SSID ADs
15
3/12/2003

40. SSID Inspection
Alternate internal
SSID inspections
Repair
Bearstrap
Doubler
HF
EC
EC
Skin
HF
VI
SU
EC
LFEC
AL
LF
External RAP
Inspection FAA previously required continued
SSID inspection of entire detail
16
3/12/2003

41. FAA SSID AMOC Example
Single RAP inspection may
satisfy both SSID and RAP
requirements
Repair
Bearstrap
Doubler
Skin
VI
SU
EC
AL
LFEC
LF
External RAP
inspection
17
3/12/2003

42. SRM DTA Data
• SRMs being revised to include updated DTA data
• Pre-Amdt 45 airplanes, 757, 767
• Chapter 51
• Definitions
0 Category of repairs
• Chapters 52 through 57
• Supplemental inspection requirements
included for specific repairs
0 Alternate SSID / SIP item inspections
0 RAP related inspections (Pre-Amdt 45 airplanes)
18
3/12/2003

43. Boeing Repair DTA Assistance
• Repair advice includes damage tolerance
assessment for applicable structural items
• PSEs / SSIs on post-Amdt 45 certified
airplanes
• SSID structures on pre-Amdt 45 certified
airplanes only when requested
• Response provided within 12 months of repair
date
19
3/12/2003

44. Repair DTA Request Data
• When requesting a DTA, submit the following
information:
• SSI number, repair/modification details and date of
installation
• Details preventing compliance of SSID requirements
• A drawing of the accomplished repair
0 Include cross sectional sketch of the repair
• Exact location of the repair doubler(s)
• Thickness and material of the doubler(s)
• Fastener types, pitch and edge margins
• Airplane identification
• Total flight cycles
20
3/12/2003

45. Summary
• Damage tolerance requirements apply to both in-
production and out-of-production airplanes
• 737 RAG and 737/747 SSIDs recently revised
• Damage Tolerance Assessment of repairs has
become a major concern for operators
21
3/12/2003

46. Widespread Fatigue
Damage (WFD)
0

47. Objective
To provide understanding of Widespread Fatigue
Damage (WFD) and Limit of Validity (LOV). In
addition, review the preliminary LOV for each Out-
of-Production, Pre-amendment 45 Boeing model
presented here.
1

48. Contents
• Background
• Implementation Plan
• Model Specific Audit Results
2

49. Background
• June 1988 - International Conference on Aging
Airplanes
• Airworthiness Assurance Working Group (AAWG)
chartered
• Comprised of members representing the
FAA/JAA, OEMs, and Operators
• Established six initiatives to develop
maintenance standards for aging airplanes
3

50. AAWG Initiatives
• Mandatory Modifications
• Corrosion Prevention and Control
• Supplemental Structural Inspections
• Maintenance Programs Guidelines
• Pressure Boundary Repair Assessment
• Prevention of Widespread Fatigue Damage (WFD)
4

51. AAWG WFD Actions
• Developed understanding and methodology for
addressing WFD
• Identified sixteen areas susceptible to WFD
• Requested OEM audits of each model for WFD
• Drafted proposed NPRM and AC for FAR 121
operational rule
5

52. Widespread Fatigue Damage
WFD is characterized by the simultaneous presence
of cracks in multiple details that are of sufficient
size and density whereby the structure will no
longer meet damage tolerance requirements (i.e.,
maintain regulatory required residual strength after
partial structural failure).
6

53. Sources of WFD
• Multiple Site Damage (MSD)
A source of WFD characterized by the
simultaneous presence of fatigue cracks in the
same structural element
• Multiple Element Damage (MED)
A source of WFD characterized by the
simultaneous presence of fatigue cracks in
similar adjacent structural elements
7

54. Prevention of WFD
• Consists of determining if any additional inspections and
modifications are necessary for each WFD susceptible
structural location
• Inspection Start Point (ISP)
• Point when special inspections of the fleet are initiated
due to probability of having a specific MSD/MED
condition
• Structural Modification Point (SMP)
• Point reduced from WFD average behavior, so that
operation up to that point provides equivalent
protection to that of a two-lifetime fatigue test
• No airplane may be operated beyond SMP without
modification or part replacement
8

55. Industry Implementation Plan for WFD
• The Industry developed program contains two
distinct issues to be addressed
• A Limit of Validity (LOV) of the Maintenance
Program
• Maintenance program adjustments (ISPs and
SMPs) to ensure WFD will be prevented from
occurring within the LOV of the maintenance
program
9

56. Limit of Validity (LOV)
• LOV is an operational limit of the airplane
• Based on engineering data that supports the
maintenance program
• All identified service actions are required for
operation up to LOV
• Established on the basis of fatigue test evidence
• Point where there is significantly increased risk
of uncertainties in structural performance and
probable development of WFD
10

57. Caveats
• For all models, an aging airplane program should
consist of:
• Mandatory Modifications
• Corrosion Prevention and Control
• Repair Assessment Program
• Supplemental Structural Inspections
• All known structural airworthiness issues,
including WFD, should be recognized and service
actions initiated
11

58. Fatigue Test Evidence for LOV
• Full scale fatigue test with or without tear down
• Full scale component tests with or without tear down
• Tear down and refurbishment of a high time airplane
• Less than full scale component tests
• Fleet demonstrated lives
• Evaluation of in-service problems experienced by
other airplanes with similar design concepts
• Analysis methods which have been parametrically
developed to reflect fatigue test and service
experience
12

59. LOV Extension
• Requires additional fatigue test evidence
• Revalidation of the maintenance program
• Review of existing ISPs and SMPs
• Possible development of new ISP and SMPs
13

60. Airplanes of Interest
• Out-of-Production, Pre-amendment 45 Airplanes
• 707 All Models
• 727 All Models
• 737 (100 thru 500)
• 747 (100, 200, 300, SP)
• DC-8
• DC-9, MD-80
• DC-10, MD-10
• Other models will be addressed later
14

61. Status of Audit Results
• The data presented here is preliminary
• FAA has been briefed
15

62. High Flight Cycle 707/720
LOV - 40,000 Flight Cycles
DSO – 20,000 Flight Cycles
35
Number of Airplanes
30
25
20
15
10
5
0
21 23 25 27 29 31 33 35 37 39
Flight Cycles (1000)
Data as of 11/2002
16

63. 707/720 Audit Findings
ISP or SMPs Less than LOV
• Lap splice
• Existing ADs adequate
• Fuselage frame
• Existing AD (SSID) - satisfy ISP requirements
• Analytical results for wing and empennage show
no ISPs below LOV
17

64. High Flight Cycle 727
LOV - 100,000 Flight Cycles
DSO – 60,000 Flight Cycles
12
Number of Airplanes
10
8
6
4
2
0
59 61 63 65 67 69 71 73 75 77 79 81 83 85 87
Flight Cycles (1000)
18

65. 727 Audit Findings
ISP or SMPs Less than LOV
• Lap splice lower row (airplanes L/P 850 and on)
• Existing AD adequate
• Fuselage frame (test finding)
• ISP 42,800 flights
• SB in work– Schedule TBD – possible FAA
rulemaking
• Stringer-to-crown skin (test finding)
• ISP 61,000 flights
• SB due out mid 2003 – possible FAA rulemaking
• Analytical results for wing and empennage show no
ISPs below LOV
19

66. High Flight Cycle 737
LOV - 100,000 Flight Cycles
DSO – 75,000 Flight Cycles
737-200 Line # 1 - 291 737-200 Line # 292 and on
16
14
Number of Airplanes
12
10
8
6
4
2
0
75K 77K 79K 81K 83K 85K 87K 89K 91K 93K 95K 97K
Flight Cycles
20

67. 737 Audit Findings
ISP or SMPs Less than LOV
• Lap splice L/P 1-291, reworked configuration
• Existing inspection AD adequate
• Anticipated new AD on modification
• Lap splice lower row airplanes L/P 292 to 2565 –
Unmodified
• Existing AD adequate
• Lap modification re-inspection L/P 292-2565
• ISP - 45,000 flights after installation
0Existing AD adequate
• Analytical results for wing and empennage show no
ISPs below LOV
21

68. High Flight Cycle DC-8
LOV - 70,000 Flight Cycles
DSO - 25,000 Flight Cycles
90
80
NUMBER OF AIRPLANES
70
60
50
40
30
20
10
0
10K 15K 20K 25K 30K 35K 40K 45K 50K 55K
Flight Cycles
22

69. DC-8 Audit Findings
ISP or SMPs Less than LOV
• Audit results to date (all fatigue test and fleet
information reviewed)
• Two areas of concern:
0Aft fuselage longitudinal splice
• ISP TBD
• SMP TBD
0Wing chordwise splice
• ISP TBD
• SMP TBD
23

70. High Flight Cycle DC-9
LOV - 110,000 Flight Cycles
DSO - 40,000 Flight Cycles
80
70
NUMBER OF AIRPLANES
60
50
40
30
20
10
0
40K 45K 50K 55K 60K 65K 70K 75K 80K 85K 90K 95K 100K 105K
Flight Cycles
24

71. DC-9 Audit Findings
ISP or SMPs Less than LOV
• Audit results (all fatigue test and fleet information
reviewed)
• One area of concern:
0 Transverse skin joint at aft pressure bulkhead
• Prior in-service issue
• Requires additional review
0 ISP and SMP TBD
25

72. High Flight Cycle MD-80
LOV - 110,000 Flight Cycles
DSO - 50,000 Flight Cycles
300
280
NUMBER OF AIRPLANES
240
200
160
120
80
40
0
0K 5K 10K 15K 20K 25K 30K 35K 40K 45K 50K 55K
Flight Cycles
26

73. MD-80 Audit Findings
ISP or SMPs Less than LOV
• Audit results - pending results from DC-9 review
27

74. High Flight Cycle DC-10 / MD-10
LOV - 60,000 Flight Cycles / 150,000 Flight Hours
DSO - DC-10-10 42,000 Flight Cycles
DC-10-30/-40, MD-10 30,000 Flight Cycles
100
NUMBER OF AIRPLANES
80
60
40
20
0
5K 10K 15K 20K 25K 30K 35K 40K 45K
Flight Cycles
28

75. DC-10 / MD-10 Audit Findings
ISP or SMPs Less than LOV
• Audit results (all fatigue test and fleet information
reviewed)
• One area of concern:
0Possible frame area
• Lower section near cargo floor beams
• Multiple frames in a row
• Failed during fatigue tests
• Still investigating
• Preliminary ISP < 30,000 flights
0ISP and SMP TBD
29

76. High Flight Cycle 747 Classic
747 Classic LOV - 30,000 f/c / 115,000 f/h (SR 35,000 f/c)
LOVext – 35,000 f/c (SR 40,000 f/c)
DSO - 20,000 Flights / 60,000 Hours (SP, SR variable)
12
Number of Airplanes
10
8
6
-SR
4 -100/-200/-200F
2
0
24000 26000 28000 30000 32000 34000 36000
Flight Cycles
30

77. 747 Classic Audit Results
ISP or SMPs Less than LOV
• Tension Tie, ISP at 20,000 f/c / SMP at 30,000 f/c
• 7075 U D Floor Beams (at floor panel holes), SMP at 23,000 f/c
• 2024 U D Floor Beams, SMP at 30,000 f/c
• Lower Lobe Frame, ISP = 14,000 f/c
• Stringer 44 Skin Lap Splice, SMP = 30,000 f/c
• Other Lap Splices < 0.071” Thick, ISP = 26,000 f/c
• Aft Pressure Bulkhead Web Splices, ISP = 28,000 f/c
• Frames Section 41 (redesigned frames), ISP = 30,000 f/c
• Circumferential Skin Splices, ISP = 25,000 f/c
31

78. 747 Classic Audit Results
ISP or SMPs Less than LOV
• LOVEXT = 35,000 f/c or 135,000 hours
• Accomplish Mandatory Modifications of all
remaining WFD audit findings at 30,000 f/c
• Perform limited teardowns and refurbishments at
LOV (wing, stabilizer, circumferential splices)
• Incorporate additional identified SBs
• SSID Rev. G (unless already incorporated)
• Actions necessary to raise LOVEXT
• Fatigue test and teardown of airframe with all
mandated modifications
32

79. Summary
• Last Aging Airplane Program addressed by
AAWG is WFD
• FAA developing Part 121 Operational Rule to
require operators to adjust maintenance in order
to preclude WFD
• Introduces concept of LOV
• May have additional inspections and structural
modifications at locations susceptible to WFD
• Boeing conducted WFD audits of Post
Production, Pre Amdt 25-45 airplanes and
established LOVs
33

80. Damage Removal
During Structural
Repairs

81. Objectives
Discuss necessity for identification and removal of
damage when accomplishing structural repairs.
1

82. Contents
• Background
• Recent 747 Action
• Damage Removal - SRM Guidance
• Maintenance Damage
• Corrosion Removal and Repair
2

83. Background
• Multiple findings of unremoved damage on 747
fuselage skins under tailstrike repair doublers
S- 46L & S- 46R
STA 2360
STA 1961
3

84. Background
• Skin scratches under repair doublers
4

85. Scratches
Fatigue
Original Skin
Cracks

86. Background
• Repair doublers
• Inhibit inspectability
• Reduce likelihood of
venting
Pressure
Repair Doubler
keeps skin from moving
outboard when pressurized
Potential skin
crack location
6

87. Crack Growth Profiles
Typical skin crack growth
originates from hole and
progresses along skin
(hole-to-hole)
Limited crack length detectable
by visual and HFEC
Skin crack growth originating
from longitudinal scratch
initiates from surface and
progresses through thickness
Visual and HFEC only detects
cracks when fully through
thickness
7

88. Service Bulletin 747-53A2489
• Released 26 November 2002
• Addresses potential skin cracks resulting from
unremoved damage at tailstrike repairs
• Tailstrike events can result in long,
longitudinal scratches
• Immediately adopted AD 2003-03-19 effective 20
February 2003
• Initial inspection prior to later of 21 May 2003
or 15,000 f/c
8

89. Other Action
• No related SB activity anticipated for other
models
• Stresses are lower in potential tailstrike area
• Heightened awareness of skin scratches among
regulatory and investigative authorities
9

90. Skin Assessment
6 inches
cutout
Scratches hidden
by repair doubler
External
detailed visual
Remove and tactile
doubler inspection
10

91. Optional Repetitive Inspections
• Frequent inspections until skin assessment
• Internal mid-frequency eddy current @ 250 f/c
or
• External ultrasonic (UT) @ 250 f/c
Internal MFEC
Reliably detect
Skin cracking when
Doubler External UT 50% through
thickness
Potential cracks
11

92. Scratch Removal
• Scratches must be removed prior to measuring
against rework limits
• If beyond limits, trim out damage prior to repair
• No allowance for blending and then installing
typical skin repairs
• For pressurized fuselage – pay particular attention
to long, longitudinally oriented scratches
12

93. SRM Guidance – Chapter 51
:
ok for
Abrasion
What to Lo Corrosion
n Crack
sc riptio
Ab rief de damage Crease
of
of types Delamination
Dent
Disbond
(12) Scratch: A line of damage in the Gouge
material where the result is a
Hole
cross-sectional area change.
This damage is usually caused Nick
by contact with a sharp object. Puncture
Scratch
13

94. SRM Guidance – Chapter 51
Defined
its are
e Lim
Wher work
in
re
its for 57
able lim rough
Allow rs 52 th
te
Chap
3. Allowable Damage
A. Make sure that you refer to the applicable
allowable damage chapter-section-subject
in Chapter 52 thru 57 of this structural
repair manual for the rework limits and the
necessary shot peening data
14

95. SRM Guidance – Chapter 51
e
amag
move D
How to Re or f
pe ctions able
and ins thin allow
Me thods at is wi
th
da mage
limits
4. Procedures to Remove Nicks,
Scratches and Gouges
A. Aluminum Metal Alloys
Includes acceptable abrasives, NDI
inspection requirements, and
protective treatments
15

96. SRM Guidance
• Allowable damage defined for each type of structure
THE DISTANCE OF THE DAMAGE FROM
AN EXISTING HOLE, FASTENERS OR SKIN
EDGE MUST NOT BE LESS THAN 20X
20X ROUND OUT TO 1.00R MIN
MIN AND TAPER AS SHOWN
X = DEPTH OF CLEAN UP
SECTION A-A
Depth and length of allowed
material removal defined
Includes restrictions such as
distance from fasteners
(above)
16

97. Maintenance Damage
• Poor maintenance practices can create damage
• Tool contact – scratch/gouge
0Removal of a fillet seal
• Removal of a doubler – scratch/gouge
• Not replacing removal of CICs - corrosion
• Blocking drain paths - corrosion
17

98. Maintenance Damage
• Some mandated SBs inspect for maintenance damage
• Industry recommendations have addressed maintenance
issues
NTSB to FAA: PAMA Article FAA published
“Issue maintenance an Advisory
PMI Action Notice
bulletin to all Circular and two
manufacturers, AC 43-16, #145 articles to inform
AIRCRAFT SKIN DAMAGE
Principle
airlines… that In two separate incidents, one in early 1987 and again in late 1988, air carrier aircraft
experienced pressurized skin ruptures and associated explosive decompression. In
both cases, the probable cause of the pressurized skin rapture has been determined to
Maintenance
be skin cracking along stress concentrations generated by scratches on the
aircraft skin.
informs them of Examination by the National Transportation Safety Board (NTSB) has resolved that
these scratches were caused by improper marking of the skin by maintenance
personnel performing structural repairs.
Pressurized General Aviation aircraft can also be adversely affected by similar Inspectors and
these incidents,…
improper maintenance practices. Although aviation mechanics are provided
information
concerning the proper handling and marking of materials used in the construction and
repair of aircraft, these incidents have generated a concern that maintenance
personnel may unknowingly damage stressed or load carrying structure by using
improper tools, equipment, methods, or by improper/careless use of the correct tools, industry of the
Direct all PMIs to
equipment, or methods. Scratches or sharp dents are very susceptible to cracking in
service, possibly at a time when the failure of the part will be catastrophic.
Scratches, dents, dings, scrapes, and other apparently minor damage, while
sometimes appearing insignificant, modify the load path through the structure
creating
importance of
review maintenance
undesirable stress concentrations.
Before evaluating or repairing any damage to stressed aircraft structure, the airframe
manufacturer's structural repair manual should be consulted for the correct
evaluation criteria and instructions concerning the use of the correct tools, methods,
and equipment.
removing
practices…” scratches
NTSB (1989) FAA (1990)
18

99. Cracking from Gouge
Example - Alert SB on 747 to address skin cracks from
gouges between a doubler and a lap splice
Edge of modification
doubler
Edge of lap splice
Clad
Gouge
Crack location
Doubler Skin
Crack
Skin

100. Maintenance Damage at Fillet Seal
Repair doubler
removed from
this area
Scratch marks in
vicinity of fillet seal

101. Cracking at Scribe Mark
External view
External view
Internal view
Internal view

102. Corrosion Removal and Repair
• Ensure complete removal of corrosion prior to
refinishing
• Trapped corrosion will continue to propagate
• Replace any damaged/removed finishes
• Unfinished area will susceptible to continued
corrosion
• Restore all drain paths
22

103. Lap Splice Repair with
Unremoved Corrosion

104. Pressure Deck Repair
with Unremoved Corrosion

105. Drain Paths
• Ensure repairs do not obstruct drain paths
• A drain path may be a gap in a structural
assembly
• Check leveling compound condition
• Replace as necessary and check adjacent areas
• Check for adequate drainage by spraying area with
water
• Restore drain paths as necessary
25

106. Summary
• Small damage can cause cracks and require
frequent inspections
• Crack patterns resulting from damage can
vary from cracking addressed in maintenance
programs
• Completely remove all damage (scratches,
gouges, corrosion) prior to repair
• Maintenance activity must not create damage
• Regulatory authorities have heightened
awareness of incomplete damage removal
26

107. Charging for
Engineering Services
0

108. Objective
• To clarify Service Engineering policy of charging
for:
• Structural Repair Approval
• Engineering Technical Support that Boeing
considers to exceed normal fleet support
1

109. Contents
• Structural Repair Approval
• Work Exceeding Normal Fleet Support
2

110. Structural Repair Approval
Applies to:
• Operators who are not operating any airplane
purchased new from Boeing and who are not
the first lessee of a new airplane received
directly from Boeing
• Maintenance, Repair and Overhaul (MRO)
facilities working on components that they
own, or working on an airplane or component
belonging to operators as defined above
0Includes operators working as an MRO
3

111. Chargeable Structural Repairs
Include requests that require Boeing to:
• Conduct structural analysis to substantiate
the structural integrity of a repair
0With or without a request for FAA 8110-3
form approval
• Accomplish a Damage Tolerance Analysis
(DTA) to provide inspection intervals and / or
methods
4

112. Structural Repair - Communication
All Operator Messages
• M-1001-00-0021, Dated 21 Dec 2000
0 Implements new charge policy
• M-7200-01-02479, Dated 18 Oct 2001
0 Clarifies charge policy
• M-7200-02-00355, Dated 1 Mar 2002
0 Expedite by providing PO number with request
5

113. Structural Repair – Charge Criteria
• Single charge of $3500 covers both the repair
and 8110-3
• 8110-3 requested at time of repair request
• Single charge of $3500 covers both the repair
and DTA
• DTA requested at time of repair request
• New charge of $3500 for an 8110-3 or DTA
• 8110-3 or DTA requested after a chargeable repair
response has been provided
6

114. Expediting Repair Approval Response
• MRO / Operator has good credit with Boeing
• Provide PO number or promise date with initial
request
0 Specify company providing PO
0 Include Spares Customer Code
• MRO / Operator does not have good credit with
Boeing
• Provide payment with initial request
0 Specify company providing payment
0 Include Spares Customer Code
7

115. Work Exceeding Normal Fleet Support
• Applies to all customers
• Assistance provided with a contract
• Policy has always been in effect
• All Operator Message issued for clarification
• M-7200-02-01766, Dated 11 Nov 2002
8

116. Examples of Work Requiring Contract
• Issuance of multiple FAA 8110-3 forms on
previously approved repairs
• On-site technical assistance
• Structural repairs requiring substantial
engineering man-hours
• Third party work support
• Support to modify airplane configuration
9

117. Contract Process Flow
• Customer sends in request for assistance
• Boeing determines work exceeds normal fleet
support
• Boeing advises customer that assistance
requires a contractual agreement
• If customer concurs, Boeing provides a Draft
Contract for review and signature
• Engineering proceeds to accomplish work when
customer has signed Contract
10

118. Summary
Structural Repair Approval
• Requests for structural repair assistance are
subject to $3500 charge, even if no 8110-3 form
is requested
• Applies to:
• Operators who are not operating any airplane
purchased new from Boeing and who are not the
first lessee of a new airplane received directly from
Boeing
• MROs working on their own components or the
above operators’ airplanes or components
11

119. Summary
Work Beyond Normal Fleet Support
• Engineering Technical Assistance will be
provided under a contractual agreement for time,
labor and material
• Applies to all customers
12

120. Structural Health Management
(SHM)
1

121. Objectives
Reduce cost of ownership and introduce
on-condition structural maintenance
Devise an automated structural inspection
system capable of diagnostics, predicting
structural damage and specifying maintenance
actions
2

122. Contents
• SHM Goals and Benefits
• SHM Definition, Development and Technology
Status
• Industry Collaboration/Engagement
• Shm Road Map
3

123. Potential SHM Benefits
• Reduced operating cost
• First step in progression to on-condition structural
maintenance
• Longer economical airframe utilization
• Structural inspection tasks customized for each
airplane
• Could be adapted to current fleet
• Allowance of a third option in SBs: Monitoring
• Determine the extent of accidental damage in areas
prone to accidental damage
• Open architecture Allowance to expand upon
existing system after airplane entry to service
4

124. What is SHM?
• SHM is a structural condition assessment
system using sensor technology that has
potential to locate airplane structural damage
• Environmental
• Accidental
• Load monitoring capabilities are under
consideration
5

125. IVHM
AHM SHM
IVHM
(Integrated Vehicle
Health Management)
Structures (SHM)
• Corrosion detection (ED)
Systems (AHM) • Environmental, delamination
• Fault message integration and Accidental Damage
• Data processing for system monitoring
reliability information • Load monitoring
• Inspector’s aid

126. IVHM Operating Concept
Maintenance
Control In Flight
Portable
Tool
Engineering &
In Maintenance Technical
Maintenance Documentation
Technician
7

127. Potential Onboard Health
Management Hierarchy
Air/Ground Wireless Ground Maintenance Data Flight crew
Communication Link Access Terminal Storage displays
Airplane Health Manager Flight Crew/Dispatch Alerting
Cabin Core Avionics CCS Health Propulsion/
Flight Controls
Health Mgr Health Mgr Mgr Utilities
Structures Health Mgr
Health Mgr
Health Mgr
Structures
HM Sensors

128. SHM Technology Testing
• Laboratory testing
• In-service testing
9

129. Sensors
Moisture Sensor
Damage Sensors
10

130. Accidental Damage Sensors Installed
Surface mounted layers
• Two embedded layers
• Three part surface mounted layers
bonded to inner mold line Embedded layers
11

131. Event and Damage Detection
Skin-Stringer Composite Barrel Demonstration
12

132. Data Logger boxes
installed on equipment racks
Battery

133. Sensor installed next to stringer
8 20
Flight data 12/23/03 3:00pm to 12/24/03 4:51pm Effective CrRt
Re'Hum (NO UNITS)
7 Temperature 31 Temperature
10
6
Corrosion 0
Corrosion Rate (microns/year)
5
Rate
4
Humidity -10
3
-20
2
-30
1
0 -40
12/23/03 2:01 PM 12/23/03 6:49 PM 12/23/03 11:37 PM Time/Date 12/24/03 4:25 AM 12/24/03 9:13 AM 12/24/03 2:01 PM
Time

134. Implementation
• What will it take to implement SHM?
• Correlation between SHM technology and
existing maintenance
0Can SHM satisfy current fleet structural
inspection requirements?
• Qualification and approval of SHM as part of
airplane maintenance (existing and new fleets)
• Industry working together
0In non-competitive areas
0Regulatory concerns
15

135. Implementation Timeline 2008
2003
Phase I
• Technology
Development and
testing
Phase II
• Working together
meetings with industry
and regulatory agencies
• Introduce concept for
current fleet
Phase III
• Expand testing and
confirm in-service a/c
SHM architecture
• Regulatory and industry
concurrence/acceptance
Phase IV
• Implementation
on 7E7

136. Summary
• SHM has potential to reduce airplane structural
maintenance cost
• Testing and development of SHM technology in
progress
• Work with airplane operators and regulators to
gain acceptance in the industry
• Technology Demonstration and Poster Session
17

137. 737 Lap Joints
0

138. Contents
• Background
• Service Bulletin (SB) 737-53A1255
• SB 737-53A1177, Revision 7 changes
• Inspection issue
• Fleet Experience
• Rulemaking
1

139. Background
• Two service bulletins currently address cracking in lap
joints on 737s:
• SB 737-53A1177, Revision 6
0 MSD cracking common to lower row of lower skin
0 Eccentric load path, high bending stresses
0 Modification of S-4, S-10, S-14 lap joints between
BS360 and BS908 at 50,000 f/c
0 Inspect other laps beginning at 70,000 f/c, repeat
inspections at 5,000 f/c
• SB 737-53A1255
0 One-time inspection program instituted in October
2002 for unmodified airplanes over 45,000 f/c
2

140. Background
L/P 292-2565 Lap Joint Configuration
Covered by
SB 737- 53A1177
and
SB 737- 53A1255
Cracks in
lower skin A
common
to lap joint
lower row
Cracks initiate at
faying surface
A
A-A
3

141. Background
SB 737-53A1177, Rev 6 Repair Locations
STA STA STA STA STA STA
259.50 360 540 727 908 1016
S-26R
BL 0
S-19R S-25R
S-24R S-20R
S-19R S-14R
S-14R S-10R
S-10R
S-4R
S-4R
S-4L S-4L
S-10L
S-14L S-10L
S-19L S-14L
S-24L S-20L
S-19L S-25L
BL 0
S-26L
Areas to be Repaired
(50,000 f/c threshold)
4

142. Background
SB 737-53A1177, Rev 6 Inspection Locations
STA STA STA STA STA STA
259.50 360 540 727 908 1016
S-26R
BL 0
S-19R S-25R
S-24R S-20R
S-19R S-14R
S-14R S-10R
S-10R
S-4R
S-4R
S-4L S-4L
S-10L
S-14L S-10L
S-19L S-14L
S-24L S-20L
S-19L S-25L
BL 0
S-26L
Repetitive Inspections
(Initial = 70,000 f/c Repeat = 5,000 f/c)
5

143. SB 737-53A1255
• Two recent fleet findings have increased concern with
extent of lower row cracking
• 23-inch linked crack at S-4L on a 737–200 (60,300 f/c)
0Extensive unlinked cracks
0Damage exceeded all prior in-service findings
• Significant cracking at S-4R on a 737–300 (52,400 f/c)
0BS 639 to BS 650: every fastener hole had cracks
over 0.5 inches emanating from each side
0BS636 to BS620: extensive cracking
0Three stinger clips cracked (one completely
severed)
6

144. Crack Locations
STA STA STA STA STA STA
259.50 360 540 727 908 1016
S-26R
BL 0
S-25R
S-19R S-20R
S-24R
S-19R S-14R
S-14R
S-10R
S-10R 639 650
23-inch crack S-4R
S-4R
S-4L on 737-200 11 inches of un-linked
S-4L
S-10L
S-14L
616 639 cracks on 737-300 S-10L
S-14L
S-19L
S-20L
S-24L
S-19L S-25L
BL 0
S-26L
Areas reported with large cracks
Smaller cracks found
7

145. Over Wing Cracking

146. Close up of Damage
Severed
Stringer Clip
Cracks

147. SB 737-53A1255
• Alert SB released 17 Oct 2002
• FAA reviewing for possible rulemaking
• Inspection directed at unmodified airplanes and
does not apply to airplanes under 45,000 f/c
• Airplanes inspected prior to AD require no
further inspections
• Accomplishment instructions included note
about sensitivity of NDT inspections
• Specific human factor issues listed that could
lead to missed cracks
• NDT technicians should be specifically trained
and qualified with LFEC and MFEC procedures
10

148. Inspection Details
• One-time inspection program with tiered approach
based on cycles and extent of findings
• Over 50,000 f/c, inspect within 45 days
• Between 45,000 - 50,000 f/c, inspect within 90 days
• Internal MFEC and visual inspections at S-4
between BS540 and BS727
0If significant cracking found in over wing area,
LFEC inspect all other SB 737-53A1177
affected lap joints
0If significant cracking is found with LFEC
inspection, internal MFEC inspection required
• Directed at specific lap joint where
significant damage was found
11

149. Over Wing Inspection Locations
Inspect S-4L and S-4R Lap
Stringer
Joint and Stringer Clips
Clip
Between BS 540 and BS 727
Typical
Crack
S-4
Tear Strap Typical Cracks
12

150. Fleet Inspection Results
• Records indicate 35 airplanes have been inspected
• 20 over 50,000 f/c
• 15 between 45,000 and 50,000 f/c
• Most have had little or no findings
• 5 needed SB lap joint repair
• Data is currently being reviewed
• No consistent crack distribution found
• Cutout sections being inspected to determine
crack lengths
• Evaluation for frequency and location of cracking
13

151. Proposed Revision 7 Changes
• Compliance related to SB 737-53A1255
inspection results
• Additional repair information for 737–200C’s at
S-4R and S-10R between BS360 and BS540
• Revisions to 737–300 repair drawings
• New repair drawings for 737–400/–500s
• Additional window corner inspections and
updates to window corner repairs
• Release anticipated late 2003
14

152. Proposed Revision 7 Changes
• Compliance changes may result from data
gathered from SB 737-53A1255 inspections
• Data is being reviewed
0Inspection thresholds may be impacted and
one-time internal inspection likely to be added
0Modification threshold may be reduced below
current 50,000 f/c
15

153. Proposed Changes: 737-200C
• Rev 6 has incomplete repair information for S-4R
and S-10R between BS360 and BS540
• Instructs operators to contact Boeing for
instructions
• Boeing has provided repair information and
approval as AMOC to AD
• Rev 7 will add complete repair instructions
• To date, 18 cargo airplanes have been modified
16

154. Proposed Changes: 737-300/400/500
• 737 –300 repair drawings are incomplete
• Unique structure not covered on drawings
0S - 4L/R just aft of BS540
0S - 10L/R just forward of BS540
0S - 10L/R between BS500D and BS520
0Boeing has provided data to operators and
approval as AMOC to AD
• Add window corner repairs to S-10 and S-14
drawings
• Repair drawings and accomplishment
instructions for 737- 400/500s will be added
17

155. Current Window Belt Recommendations
• Accomplish inspections of 3 fasteners in corners
common to window frame at 50,000 f/c
• BS360 to BS540, Upper Forward / Lower Aft
corners
• BS727 to BS908, Lower Forward / Upper Aft
corners
• If no cracks, accomplish Preventative Modification
0Install oversize fasteners at all three locations
• Accomplish repair if cracks detected
0Integrated with lap joint repair
• Cracks believed to be common to skin/bonded
doubler only
18

156. Rev 6 Window Corner Inspections
Rev 6 Inspection Locations
19

157. Rev 6 Window Corner Experience
• Cracks reported deviating from Rev 6
instructions
• Common to skin/bonded doubler along S-11
and S-13 and along window frame
• In S-11 and S-13 sections
• In window frames
• Boeing has confirmed cracks
• Revised recommendations necessary to capture
new crack findings in fleet
20

158. Rev 7 Window Corner Inspections
Rev 6 Inspection Locations
New Rev 7 Inspection Locations
21

159. Proposed Window Corner Changes
• Additional inspections and/or rework may be
necessary for airplanes inspected per Rev 6
• Rev 7 will include a flowchart to guide
operators in decision making
• New repair figures will be added to SB, SRM, and
737–300/400/500 repair drawings
• Option to replace window belt skin assembly to
eliminate need to inspect/repair window corners
under study
22

160. Proposed Window Corner Changes
• Data package will be provided to operators in mid
2003, in advance of Rev 7
• Revised inspection instructions, including use
of 0.020 notch for open hole inspections
0Updated repair instructions
0Expanded allowable damage limits
0Format similar to Rev 6
• Will be FAA approved and considered an
AMOC to AD 2002-07-08, paragraph (g) and (n)
23

161. Inspection Issue
• Alodine (conversion) coated rivets replaced
anodized coated rivets
0Phased into production 1985-1995
• Alodine coated rivets render sliding probe and
Magneto Optical Imaging (MOI) NDT methods
ineffective
• Significantly impacts lower row external inspections
in SB 737-53A1177 and SB 737-53A1255
• May result in missed crack indications
24

162. Anodize vs. Alodine Rivets
Consistently long Inconsistent short rivet
rivet signals signals with a phase change
Good EDM notch signal Unacceptable EDM
notch signal
3/16 inch Anodize Rivets 3/16 inch Alodine Rivets
25

163. Inspection Issue
• Method to identify type of coating on installed
rivets under study
• Existing sliding probe inspection method may
be used on anodized coated rivet locations
• Alternative inspection method to be developed
for alodine coated rivets
• Working with affected operators to identify
airplanes impacted near-term by SB 737-53A1177
inspections
• Additional inspection steps may necessary
26

164. Fleet Experience
• Approximately 155 airplanes modified to date
• 134 737-200/-200Cs
• 21 737-300s
0140 have accomplished lap joint cutout repair
015 have Rev 1, 2 or 3 Preventive Modification
• No common crack distribution
• Significant cracks found on some airplanes
• Others have been relatively crack free
• Window corner cracking will impact downtime
• On-site engineering and NDT assistance
available
27

165. Rulemaking
• Three ADs issued against Rev 6 effective 17 May 2002
• AD 2002-07-08: Lap joint cutout repair at 50,000 f/c,
window corner inspections at 50,000 f/c, and lower
lobe inspections at 70,000 f/c
• AD 2002-07-10: Replacement of obsolete local SRM
lap joint repairs
• AD 2002-07-11: SRM repair of local areas aft of
wing on airplanes L/P 1-291
• Immediate Adopted Rule expected for
SB 737-53A1255 to provide one-time inspection
recommendations
28

166. Summary
• Two recent fleet findings have increased concern
with extent of lower row cracking
• One-time SB 737-53A1255 inspection program
• Revision 7 currently scheduled for release late 2003
• Major changes have been communicated to
operators
• Compliance changes may result from SB 737-
53A1255 inspections
• Window corner data package available 2nd Qtr 03
• Three ADs for SB 737-53A1177, Rev 6
• FAA will review SB 737-53A1255 inspections for
possible rulemaking
29

167. 2003 Structures Conference
Service Engineering
Nondestructive
Testing (NDT)
Personnel Training
and Certification
1

168. Objectives
Increase awareness of Nondestructive Testing
(NDT) training and certification options, that can
promote better inspections with fewer false or
missed indications.
2

169. Contents
• Background
• Options for Training and Certification
• FAA Guidelines
• CAA/European Requirements
3

170. Background
• Increasing reliance on NDT detecting smaller cracks
• Improper inspection evaluation has caused
additional downtime and cost
• Cracks may be missed due in part to inadequate
training
• Regulatory authorities now expecting
implementation of training and/or certification
programs
4

171. Incorrect Evaluation Result
Assumed
crack
4 inch
5

172. Example of Missed Cracks
6

173. Options
• Select a training and / or certification program
• Central certification - external agency
• Local training - internal airline / MRO
• Use an NDT service provider with trained and
certified personnel using the same programs
7

174. Central Certification Programs
• USA
• ASNT Level III Certification
• Europe
• EN 473 equivalent for each country
• Canada
• CAN/CGSB-48.9712-95 Canadian General
Standards Board version of ISO 9712
8

175. Internal Airline/MRO
Training and Certification Programs
• USA standards
• AIA-NAS 410 Draft to combine with EN 4179
(NAS/EN XXXX)
• ASNT SNT-TC-1A Guidelines
• ATA 105 Guidelines for Training & Qualifying
Personnel in NDT
• European standards
• EN 4179 equivalent for each country
9

176. FAA Advisory Circular Pending
• Requires documented education, training and
experience
• Recognizes standards / specifications
(i.e., EN/PCN/ASNT/CGSB)
• Recognizes organizations with independent
examination
• Recognizes three levels of competence
10

177. European Standards
• EN standards
• Internal and external specifications
• Three levels of competence
• Documented education, training and
experience
• Regulatory action
• Example: U.K. CAA Airworthiness Notice No.
94 regulates training and certification of NDT
personnel
11

178. Summary
• Controlled NDT training and certification reduces
false and missed indications
• Meet a recognized standard that may include:
• Recording past training and experience
• Attending training for NDT methods
• Level II and III examinations as needed
• Establishing a company Written Practice
12

179. 737 Classic
Fuselage Issues
0

180. Objective
Provide overview of 737 Classic fuselage
structural issues that may be subject of
future FAA rulemaking.
1

181. Contents
• Existing Service Bulletin Recommendations
• New In-Service Findings
• New or Revised Boeing Recommendations
• FAA Action
2

182. 737 Classic Fuselage Issues
SB 737-53-1216Frame Cracks
Between S-8 and S-9
SB 737-53A1224 Lap Joint
SB 737-53A1228
Lower Cracking: 1-291 Cargo Door Cutout
Corner Cracks
SB 737-53A1210
and 737-53A1234
Skin Cracks at
Chem-mill steps SB 737-53-1125
Frame Cracks
Above S-14
SB 737-52A1149 SB 737-53A1166
Fwd Cargo Door S-18A Cracking at BS727
#4 Beam Cracks
SB 737-53A1254
Over-wing Exit
Frame Cracks
3

183. Cracked Frames Above S-14
SB 737-53-1125
Frame Cracks
Above S-14
4

184. Cracked Frames Above S-14
Existing Recommendations
• SB 737-53-1125, Rev 2 released Nov 1991
• Addresses fatigue cracking common to frame
between S-13 and S-14
0Last fastener common to fail-safe chord at
frame splice
0Effective L/P 1-1919
• Preventive modification by 40,000 f/c
0Trim last fastener off of fail-safe chord
0Install oversize rivets at remaining 4 locations
0Repair frame per SRM if cracked
5

185. Cracked Frames Above S-14
In-Service Findings
• Severed BS 747 frame and a 1.3 inch crack in
adjacent BS 767 frame at same location
• Cracks initiated below existing SB737-53-1125
inspection threshold of 40,000 f/c
• Frames between BS380 and BS908 similarly
designed
• Cracks considered a safety of flight issue
• Multi-element damage (adjacent frames
cracked)
• Frames cracked near S-14 lap joint which has
a demonstrated multiple-site damage issue
(SB737-53A1177)
6

186. Cracked Frames Above S-14
Frame Cracks Start At End
Fastener Common to Splice
7

187. Cracked Frames Above S-14
• New Recommendations
• SB 737-53-1125 to be revised and upgraded to Alert
status
0Initial inspection threshold and interval changed
0Inspection method changed
0Repair for cracks provided
• Rev 2 preventive mod should not be accomplished
• FAA Action
• Reviewing SB 737-53-1125 Rev 3 for possible
rulemaking
8

188. Frame Cracks Between S-8 and S-9
SB 737-53-1216
Frame Cracks
Between S-8 and S-9
9

189. Frame Cracks Between S-8 and S-9
• Existing Recommendations
• No Service Bulletin
• In-Service Findings
• Numerous cracked frames between S-8 and S-9
common to air conditioning attach brackets
0Reports from 9 airplanes
0Cracks typically 1 inch or less in length
• Cracks considered a safety of flight issue
0Multi-element damage (adjacent frames cracked)
0Near S-10 lap joint which has a demonstrated
multiple-site damage issue (SB 737-53A1177)
10

190. Frame Cracks Between S-8 and S-9
11

191. Frame Cracking between S-8 and S-9
• New Recommendations
• New 737-53-1216 SB to be released mid 2003
0Effective L/P 991-3132
0Applies to all frames between BS380 and
BS908 similarly designed
0Will provide inspection thresholds, terminating
modification and repairs
• FAA Action
• Will review for possible rulemaking following
release of SB 737-53-1216
12

192. Skin Cracks at Chem-mill Steps
SB 737-53A1210 and 737-53A1234
Skin Cracks at Chem-mill Steps
13

193. Skin Cracks at Chem-mill Steps
• Existing Recommendations
• SB 737-53A1210, Rev 1 released Oct 2001
0Addresses cracking along edges of chem-mill
pockets
• Cracks found at S-12, above S-4, S-10 and
S-14 lap joints, and below S-14 on numerous
airplanes
0Effective L/P 292-2565
0Crown area
• NDT and visual inspections at 35,000 f/c or
within 4,500 f/c from release of Rev 1
• Repeat visual inspections at 4,500 f/c
• Repair per SB if cracks found
14

194. Skin Cracks at Chem-mill Steps
• Existing Recommendations
• SB 737-53A1210, Rev 1 released Oct 2001
0Section 41 and areas below S-14
• Visual inspections at 40,000 f/c or within
4,500 f/c from release of Rev 1
• Repeat at 9,000 f/c intervals
• Repair per SRM or contact Boeing if cracks
found
15

195. Skin Cracks at Chem-mill Steps
• Existing Recommendations
• SB 737-53A1234 released June 2002
0 Testing predicts cracking along edges of chem -mill
pockets in above S-4 and S-10 lap joints
• No in-service cracks reported
0 Effective L/P 2553-3132
0 Accomplish external NDT and visual inspections at
21,000, 33,000 or 42,000 f/c depending upon location
and series
• Initial threshold dependent upon model and location
• Repeat visual @ 1,200 f/c or NDT @ 3,000 f/c
• Repair per SB if cracks found
16

196. Skin Cracks at Chem-mill Steps
Crack at
Chem-mill Step
A
A
A-A
17

197. Skin Cracks at Chem-mill Steps
• In-Service Findings: SB 737-53A1210
• Numerous cracks along edge of chem-milled
pockets
0Initiating well below 35,000 f/c inspection
threshold
0Appearing in other areas not currently covered
in SB
0Multiple cracks in adjacent bays
• Cracking considered a safety of flight issue
0Multi-element damage (adjacent bays cracked)
0Near lap joints which have a demonstrated
multiple-site damage issue (SB 737-53A1177)
18

198. Skin Cracks at Chem-mill Steps
• Recommendations
• SB 737-53A1210 to be revised
0Reduce thresholds for initial visual and NDT
inspections and repeat visual inspections
0Expand inspection areas due to in-service
findings
0Develop new NDT internal inspection
technique for unmodified areas covered by
external repairs
• FAA Action
• Reviewing SB 737-53A1210 and 737-53A1234
for possible rulemaking
19

199. Forward Cargo Door Beam Cracks
SB 737-52A1149
Fwd Cargo Door
#4 Beam Cracks
20

200. Forward Cargo Door Beam Cracks
• Existing Recommendations
• SB737-52A1100, Rev 4 released Mar 2001
0Addresses cracking on forward cargo door in
lower frames and #5 (lower) cross-beam
0Cracks in radius of frames and in web of #5
cross-beam
0Effective for all 737 Classic airplanes
0Mandated by AD 2000-07-06
• For both frame and #5 cross-beam
0Visual inspections
0Repair per SB if cracks found
0Accomplish preventive mod if no cracks found
21

201. Forward Cargo Door # 4 Beam Cracks
#4 Cross Beam
Typical Crack
A
A
#5 Cross Beam
22

202. Forward Cargo Door # 4 Beam Cracks
• In-Service Findings
• Four operators reported cracking in #4 stop
beam
0Root cause of cracks attributed improper door
rigging and/or a cracked #5 cross beam
0Additional load being redistributed into #4
cross beam
23

203. Forward Cargo Door Beam Cracks
• New Recommendations
• Release SB737-52-1149 in late 2003
0Will provide inspection, repair, and modification
details for #4 cross beam
0Similar to SB737-52A1100
0Effective for all 737 Classic airplanes
(L/P 1-3132)
• FAA Action
0Reviewing SB737-52-1149 for possible rulemaking
24

204. Lap Joint Corrosion and Cracking
SB 737-53A1224
Lap Joint Lower Cracking: 1-291
25

205. Lap Joint Corrosion and Cracking
• Existing Recommendations
• AD 2000-17-04 mandated original inspection program
• SB 737-53A1224, Rev 1 released Mar 2002
0 Addresses cracking and corrosion in cold-bonded lap
joints
0 Effective L/P 1-291
0 NDT external and internal crack inspections repeated
• 1,000 f/c intervals for airplanes above 70,000 f/c
• 2,000 f/c intervals for airplanes below 70,000 f/c
• Repair cracks or corrosion per SRM
0 Visual corrosion inspections repeated every 4 years
0 Modification of all 44 lap joints terminates inspections
26

206. Lap Joint Corrosion and Cracking
Upper skin
Cracks in lower
fastener row
Covered by
SB 737-53A1224
Corrosion - upper
and lower skin
Lower skin
Cracks in upper
fasteners row
27

207. Lap Joint Corrosion and Cracking
• In-Service Findings
• Many reports of cracks and corrosion
0Extensive corrosion in laps and butt joints
0Existing repairs or blend-outs exceeding 10%
in area of lap joints
0Local SRM repairs installed
0Some full panel repairs installed
• 139 active affected airplanes
0Fleet average at 33 years and 65,000 f/c
28

208. Lap Joint Corrosion and Cracking
• Recommendations
• Modify all 44 lap joints to maintain safety
0 Threshold based on accumulated flight cycles
• Below 65,000 - earlier of 70,000 f/c or
4 years
• 65,000 – 80,000 - within 5,000 f/c, not
to exceed earlier of
81,000 f/c or 4 years
• 0ver 80,000 - within 1,000 f/c
0 High probability of existing repairs, blend-outs, and
corrosion damage that would affect repair
0 Contract required for customized engineering
• FAA Action
• Reviewing SB 737-53A1224 Rev 1 for possible rulemaking
29

209. Lap Joint Corrosion and Cracking
STA STA STA STA STA STA
259.50 360 540 727 908 1016
S-26R
BL 0
S-19R S-25R
S-24R S-20R
S-19R S-14R
S-14R S-10R
S-10R
S-4R
S-4R
S-4L S-4L
S-10L
S-14L S-10L
S-19L S-14L
S-24L S-20L
S-19L S-25L
BL 0
S-26L
Inspection and Modification Areas
30

210. Cargo Door Cutout Corner Cracks
SB 737-53A1228
Cargo Door Cutout
Corner Cracks
31

211. Cargo Door Cutout Corner Cracking
• Existing Recommendations
• No SB addresses cargo door cutout cracking
• SB 737-53-1051 and 737-53-1096 address cargo
doorway frames
• In-Service Findings
• Forward and aft cargo door cutouts
0Numerous cracks in skin/bonded douber,
bearstraps, and doorway frames
0Post SB 737-53-1051 and 737-53-1096 mod
cracks on frames
• –200C main cargo door cutout
0Numerous cracks in skin/bonded doubler and
bearstrap on upper corners
32

212. Cargo Door Cutout Cracking
33