Widespread Fatigue Damage

All Model
Widespread Fatigue Damage
Meeting

March 4, 2003

Opening Remarks

John Banbury
Vice-President,
Technical Services

Welcome
and
Introductions
Rao Varanasi, Ph.D.
Chief Engineer
Structures and Aging Fleet Programs

Agenda
• 8:15 Opening remarks
Welcome and Introductions
• 8:30 Purpose of meeting
Regulator Comments
Operator Comments
Background Discussion
WFD Program Overview
• 9:45 Break
• 10:00 Presentation of Model Specific LOVs
Process followed to develop LOV
Summary of Boeing Model Specific LOV Finding

Agenda (cont’d)
• 10:30 Program Documents (Planned Publications)
• 11:00 Discussion / Q & A
• 12:00 LUNCH
• 1:00 Caucus Expectations
• 1:15 Operator Caucus
• 2:45 Break
• 4:00 Reconvene Meeting – Operator Out Brief
• 5:00 Adjourn

Logistics - Building 25-01
• T.A. Wilson Conference Room
– Phones
• 206-662-8124/-8125/-8127/-8128
– Restrooms
– Cafeteria
– Breaks
– Smoking allowed outside only

Purpose
March 4, 2003 Meeting

• March 4, 2003 All Operators Meeting and
Follow-on STG Meetings
• Continuation of the dialog about airplane structural
integrity
• To inform all operators on the status of the program
• To present information to assist operators in preparation
for compliance to the expected Widespread Fatigue
Damage (WFD) Rule
• To disseminate the preliminary audit results for out-of-
production Pre-amendment 45 Airplanes
• To obtain feedback

Regulator Comments

Brent Bandley – FAA Los Angeles ACO

Aging Aircraft Program

Brent Bandley
FAA
Transport Airplane Directorate
Manager

Background

• The elements of the current aging aircraft
program were the result of the following:
– April 1988 accident involving Boeing 737 in Hawaii
– First conference on aging airplanes, June 1988
– In August 1988 the Airworthiness Assurance Task
Force (AATF) was established as a sub-group of
the FAA’s Research, Engineering and
Development Advisory Committee representing
the interests of aircraft operators, aircraft
manufacturers, regulatory authorities and other
aviation representatives

Elements of Aging Aircraft Program

• The AATF set forth five elements for keeping
the aging fleet safe but another element has
been added:
– Structural Modification Program
– Corrosion Prevention and Control Program
– Structural Maintenance Program Guidelines
– Review and Update Supplemental Structural
Inspection Documents (SSIDs)
– Damage Tolerance of Repairs
– Program to preclude Widespread Fatigue
Damage (WFD) from the fleet

Development of Widespread Fatigue
Damage Rulemaking
• The development of the WFD rulemaking was
accomplished under the auspices of the Aviation
Rulemaking Advisory Committee (ARAC):
– ARAC was established on January 22, 1991 to
provide advice and recommendations concerning the
full range of the FAA’s safety-related rulemaking
activity
– By Federal Register notice dated November 30,
1992, the AATF was placed under the auspices of
ARAC and renamed the Airworthiness Assurance
Working Group (AAWG)
– One of the specific tasks assigned to the AAWG was
to develop recommendations concerning a program
to preclude WFD in the fleet of large transport
airplanes

• The FAA is proposing rulemaking (NPRM) to
implement a program to preclude widespread
fatigue damage (WFD) from the fleet of large
transport category airplanes applicable to:
– Operators that operate large transport category
airplanes (>75,000 maximum takeoff gross weight)
that are operated under,
– part 121 and 129.
– baseline structure, applicable repairs, alterations
and modifications.

• Within one year after the effective date all airplanes
must have an initial limit of validity (LOV) in flight cycles
or flight hours specified in their Airworthiness Limitations
Section (ALS)
– For airplane models certified to § 25.571 or §
25.1529 prior to amendment 25-54, a new ALS will
need to be developed that specifies an initial LOV
(LOV1)
– The LOV1 is established as the point in time beyond
which the airplane cannot operate unless a program
to preclude WFD is incorporated into the structural
maintenance program (usually at the airplanes
established DSG or Extended Service Goal (ESG)
– The ALS must be approved by the ACO having
cognizance over the type certificate for the affected
airplane

• To operate beyond the initial LOV, operators
must incorporate a program to preclude WFD
for the baseline structure (original type design)
into their maintenance program.
– The program will identify a new LOV (LOV2)
– The program will identify any new MSD/MED
inspections and/or modification/replacement actions
required to get to LOV2 without risk of developing
WFD
– The program will include inspecting MSD/MED
susceptible structure 2-3 times before it gets modified
or replaced.

• Paragraph (b): Cont’d.
– The program to address baseline structure
must be approved by the ACO having
cognizance over the type certificate for the
affected airplane
– Most type certificate holders (TCH) are
supporting rulemaking by accomplishing
structural audits to produce maintenance
programs which include inspections and
modification/replacement actions to baseline
structure

• Once a program is established for the baseline structure to get
to LOV2, operators would be required to incorporate a
supplemental WFD program within 48 months which includes
inspections and modification/replacement actions to repairs,
alterations and modifications (RAMs) to baseline structure into
their maintenance program for prevention of WFD
– Within 48 months the operators must survey their airplanes for
MSD/MED susceptible RAMs and submit a plan that must be
approved by the ACO, accomplish a WFD assessment and then
submit a full structural maintenance program.
– To assist the operators and STC holders, some TCHs
maintenance program documents will contain general guidelines
developed along strict boundaries for the screening of repairs and
STCs

• Any new repairs after effective date of rule must be
assessed for WFD within a certain time frame.
– Within 18 months of the approval for return to service, a
WFD analysis of the repair, alteration or modification
which defines the threshold for inspections and/or
modification/replacement actions is approved for the
FAA ACO or office of the TAD
– Before reaching the threshold, specific FAA-approved
inspection methods, repeat intervals and/or
modification/replacement actions are incorporated into
the FAA approved structural maintenance program for
each repair, alteration or modification


• Needs from Industry to support rulemaking:
– TCHs publish revised and new ALSs for all applicable
models (for inclusion in NPRM docket) establishing
LOV1, at least
– For models where lead airplane is beyond DSG/ESG as
of December 31, 2001 the TCHs will publish proposed
maintenance program documents to address MSD/MED
(inspections and modification/replacement of baseline
structure) for inclusion in NPRM docket

Widespread Fatigue Damage Rulemaking
Status
• The WFD NPRM has not been issued yet.
– A Principal’s Briefing was held October 18, 2002. The
NPRM was supported by the highest levels of FAA
management in Aircraft Certification and Flight
Standards. The NPRM was given an “A” priority by the
FAA.
– The NPRM is still within the FAA.
– The NPRM must be reviewed and approved by the
Office of Secretary of Transportation and the Office of
Management and Budget before it can be issued as a
NPRM.

Summary

• The WFD NPRM is making it’s way through
the rulemaking process.
• The FAA would like to thank The Boeing
Company for their support to conduct
Structural Audits of their airplanes to
determine Limits of Validity and inspection
and/or modification/replacement actions for
baseline structure.

Regulator Comments

John Bristow - JAA (CAA - UK)

Operator Comments

Airworthiness Assurance Working Group
(AAWG)
Widespread Fatigue Damage Prevention
Program Development Operator Overview

Aubrey Carter
General Manager - Enabling Technologies
Co-Chairperson AAWG

AAWG Aging Aircraft Program Development-

Operator Participation in FAA Tasking
Steering Committee Voting Members
– Airborne Express, American Airlines, America West, British
Airways, Continental Airlines, Delta Air Lines, Federal Express ,
Northwest Airlines, UPS, United Airlines, US Airways

• Task Planning Group (TPG)
– Continental Airlines, Delta Airlines, FedEx, KLM, and UPS

• Rule Writing Group (RWG)
– Continental Airlines, Delta Airlines, FedEx, KLM, and UPS
– Continental, KLM, and UPS Inactive 2002-2003

• JAL and Southwest Airlines were invited participants in March 21, 2003
AAWG Meeting

Operators Engaged in Program Development

AAWG Aging Aircraft Program Development -

Widespread Fatigue Damage (WFD) Prevention Program Rule Writing
Tasking 1998-2000
• Propose new operating rules that would ensure that no large transport
category airplane greater than 75,000 lbs. gross take-off weight is
operated beyond the flight cycle limits (specified in the regulation) unless
an “Aging Aircraft Program” has been incorporated into the operator’s
maintenance program
• Establish the content of the Aging Aircraft Program with the necessary
special inspections and modification actions for the prevention of
widespread fatigue damage
• Establish the limit of the “validity” in terms of flight cycles or hours of the
Aging Program where additional reviews are necessary for continued
operation
• Establish the required content of an Aging Aircraft Program
• Establish the flight cycle limit of the operators maintenance program
• Phase 2 Task completion date: September 15, 2000
New Rules and Advisory Circular Drafted


WFD “Bridging Tasking” 2001-2003
• Develop advisory/guidance materials for the prevention of widespread
fatigue damage through control of multiple element damage (MED)
sources
– Round robin exercises in progress by Boeing, Airbus and Delta
– Probabilistic approaches assessed
– Management risk level determination in progress
– Fleet variability reviewed extensively
– Load redistribution assessed
– Draft final report underway
• Develop training materials
• Establish NDT baseline for the evaluation of new technologies
– Sandia National Laboratories establishing second layer detection capability
“baseline” using Delta lap joint specimens
– Generic standards being developed by FAA Tech Center and Iowa State
University

Additional Guidance Materials Being Developed


Frequently Asked Questions

• WFD terminology?
• Why are we addressing WFD now?
• Why is WFD not adequately addressed by existing Aging Aircraft
Programs?
• What are the differences between traditional SSIP damage tolerance
based programs and WFD prevention programs?
• What aircraft and maintenance aspects are affected by this initiative?
• What changes will be required by operators?
• What has been accomplished to date?
• What are the benefits of this program?

Key Points for Operators


Widespread Fatigue Damage (WFD) Terminology

• Widespread fatigue damage in a structure is characterized by the
simultaneous presence of (small) cracks in multiple details that are of
sufficient size size and density whereby the structure will no longer meet
damage tolerance requirements, i.e. to maintain regulatory residual
strength after partial structural failure

• Multiple Site Damage (MSD) is a source of widespread fatigue damage
characterized by the simultaneous presence of (small) fatigue cracks in
the same structural element

• Multiple Element Damage (MED) is a source of widespread fatigue
damage characterized by the simultaneous presence of (small) fatigue
cracks in similar adjacent structural elements

What is WFD?


Why Are We Addressing Widespread Fatigue Damage (WFD) Now?

• Two lifetime fatigue test confidence level recommendation by NTSB in
1988 accident report
• Averaging three significant MSD or MED events per year in fleet
resulting in reactive airworthiness directives
• MSD/MED test evidence
• MSD/MED analytical evidence of interaction of small cracks
• WFD is not prevented by existing programs
• Inspection technology ready
• WFD would reduce large damage capability provided by operators
existing “visual” maintenance programs
• Safety level may deteriorate below regulatory residual strength levels as
fleet ages beyond original design service goals, if WFD not precluded

Fleet Safety Enhancement


Why Is WFD Not Adequately Addressed By Existing Aging Airplane
Programs?

• Original modification and inspection programs addressed known service
bulletin problems that typically occur below design service goal (DSG)

• Aimed at prevention of interaction between corrosion and fatigue as the
fleet ages

• Addressed “lead cracks” from a damage tolerance perspective

• Did not recognize, nor addressed the interaction of small crack arrays in
type certified configuration, alterations or repaired structure

• Implemented prior to WFD analysis methodology development and
validation by industry

High Safety Level Achieved, But Additional Actions Indicated


What Are the Differences Between Traditional Supplemental Structural
Inspection Damage Tolerance Based Programs and New Widespread
Fatigue Damage Prevention Programs?

SSIP WFD

Lead cracks Crack Arrays
No Crack Interactions Crack Interactions
Deterministic Models Probabilistic Approaches
Crack Growth Focus Crack Initiation Focus
Loss of Load Path Residual Strength Loss
Inspection Choices Few Inspection Alternatives
Below DSG Post DSG
Age Exploration Defined Modification Point
Detail Specific Maintenance Program Limit

Distinct Cracking Scenarios and Solutions


What Aircraft and Maintenance Aspects Are Affected By This Initiative?

• Applicable to transport category aircraft certified to pre and post
Amendment 14 CFR Part 25-45 aircraft with maximum take-off gross
weights greater than 75,000 lbs.

• Establishes a “Limit of Validity (LOV)” for current structural maintenance
programs to ensure that WFD is precluded until the flight cycle or flight
hour limit has been reached by each airplane in the operator’s fleet

• Establishes airworthiness limitations on all affected airplanes listing
required aging airplane program prerequisites, plus WFD based
inspections and modifications

• Establishes requirements to address WFD prevention for repairs and
alterations
WFD Initiative Has Broad Scope


What Changes Will Be Required By Operators?

• New operating limits on aging airplane maintenance programs
• New NDT inspections for small flaws in large areas beyond current
Supplemental Structural Inspection Programs (SSIP) with identified
“Inspection Start Point” (ISP) and end point defined as the “Structural
Modification Point” on a susceptible area basis
• New modifications to terminate inspections, or preclude WFD if structure
can not be reliably inspected
• More awareness of MSD/MED service problems
• Engineering responsibilities increase (repairs, alterations)
• Meet new regulatory timelines for addressing existing and new repairs,
alterations
• Mandated reporting requirements unchanged, although more reporting
of early findings of MSD/MED with OEMs recommended
• Fleet planning influence (retirement decisions)

New Operating Rules


What Has Been Accomplished To Date?
• 16 common design details have been identified by test and service
experience as being susceptible to MSD/MED sources of WFD
• Round robin MSD exercises to identify key parameters affecting the
outcome of analytical approaches were conducted by Boeing, Lockheed,
Airbus and Delta
• Round robin MED exercises underway by Boeing, Airbus and Delta
• Standardized terminology and evaluation process for WFD program
elements (Fatigue Initiation, ISP, SMP, WFD Average Behavior, Large
Damage Capability - LDC)
• Uniform fleet risk management levels across fleets
• FAA Technical Oversight Group for Aging Group and Authorities Review
Team reviews of WFD methodologies conducted
• Discrete Source Damage interaction considerations quantified
• Assessed current and emerging NDT capabilities
• Technology transfer (final report, draft NPRM, draft AC)

Industry Consensus and Effective WFD Prevention Programs
Ready for Implementation


What Are the Benefits of this Program (Once Implemented)?

• Proactive and knowledge-based approach adopted instead of a
continuing series of mandated service actions (operating rules vs.
airworthiness directives)
• Reduction in significant operating disruptions caused by non-routine
service crack findings
• Industry involvement (through a structured and consensus building
process) in program decisions
• Long term fleet planning timelines with known requirements
• Accelerated NDT research initiatives by OEMs and FAA Hughes
Technical Center
• Managed structural risk and reliability obtained for airplanes operating at
or beyond original DSG
• No longer “out-flying the test”
• Institutionalized “cradle-to-grave” aging airplane structural airworthiness

Safety Objectives Will Be Achieved

Background Discussion

Rao Varanasi, Ph.D.
Chief Engineer
Structures and Aging Fleet
Programs

Contents

• Background
• The Sixth Initiative - WFD
• Chronology

Background

• April 1988 – Aloha Accident
• June 1988 – International Conference
on Aging Airplanes
– Industry committed to enact effective
programs to maintain structural integrity as
airplanes age (DOT-TSC-FA890-88-26
Appendix A1)
– Focused attention on gaps in the
airworthiness system

AATF Established

• AATF (now AAWG) became the genesis for
five aging airplane initiatives:
• Mandatory Modifications
• CPCP
• SSID
• Repair Assessment
• Maintenance programs
• AATF also established a commitment to
examine and produce an effective program
for the prevention of WFD in the commercial
fleet; hence, WFD is the sixth aging airplane
initiative

What Has Happened Since
• Accomplishments since 1988
– Five aging airplane initiatives have been
institutionalized
– Three reports have been prepared on the subject of
– New operational and certification rules for the
prevention of WFD are in the process of being released
• In 1995, the US industry committed to the FAA to
have model specific WFD audit documents for all
pre-amendment 45 airplanes by 31 December
2001

The Sixth Initiative - WFD

• The sixth aging airplane initiative was established to
develop maintenance programs for the prevention of
WFD in the commercial fleet
• An international team of experts under the direction
of ARAC developed a program that contains two
distinct issues to be addressed
– A Limit of Validity (LOV) of the Maintenance Program
– Maintenance Program adjustments to ensure WFD will be
discovered and corrected within the LOV of the maintenance
program
• This presentation presents the development of the
LOV for Boeing’s out-of-production pre-amendment
45 Airplanes

Chronology

• The Chronology of the Sixth Aging Aircraft
Initiative of the AAWG / TAEIG / ARAC, WFD, is
represented by the following reports, rules and
advisory materials:
– 1990 Report - Fatigue Testing and Teardown Issues.*
– 1993 Report - Structural Fatigue Evaluation for Aging
Airplanes.*
– 1999 Report - Recommendations for Regulatory
Action to Prevent Widespread Fatigue Damage in the
Commercial Airplane Fleet.*
– 2001 Draft Rule and AC on WFD Submitted to ARAC

* These reports are contained in your back-up data

Boeing WFD Activities

• Boeing has continuously supported all of the initiatives of
the AAWG / TAEIG / ARAC
• 1995 Boeing commits to WFD Audits
• 2001/02 Boeing establishes operational limits for the 747
in response to operator inquiries
• 2001 STG Chairs Meeting - Introduced WFD
terminology and solicited input as to way to proceed
• March 2002 All STG Meeting - Presentation and
description of WFD program
• March 2002, Boeing / FAA-Seattle ACO begin structured
review of the methodology and audit results

Boeing/FAA Interaction
FAA Reviews of BCA Methodology

• FAA methodology reviews since March 2002
– March 2002, 747 Data
– April 2002, SDT Review
– June 2002, SDT Review
– October 2002, 707, 727, and 737 Review
– November 2002, SDT Review
– February 2003, SDT Review
• February 2003, Seattle ACO/LA ACO Review
of Preliminary Results
• February 2003, JAA Briefed on Preliminary
Results

Current Situation

“Operators could continue to operate and
inspect airplanes indefinitely {or until
economics dictate} based on expectation that
things like residual strength, S/B. etc. would
“Protect” the fleet. In essence, the aircraft
could operate in “uncharted” territory from a
fatigue/damage tolerance point of view.”
AAWG Sept. 10, 2001

Future Course

“The in-work WFD assessments “chart the
territory” beyond the fleet leader in discrete
blocks of time (cycles). The assessment, or
audit, examines data from the fleet, applicable
fatigue test results, and analysis to develop a
revised mandatory maintenance program to
ensure safety prior to operating the aircraft in
that block of time.”
AAWG Sept. 10, 2001

Boeing/Industry Interaction
Planned Coordination

• Milestones
– This week’s meetings
– STG document coordination meeting(s)
– Publication of WFD model specific
programs documents for out-of-production
pre-amendment 45 Airplanes

Airplanes of Interest

• Today we will be talking about 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 Airplane Models

• The remaining airplanes will be handled in
separate meetings
– e.g. 737NG, 747-400, MD-11
– Meetings will be scheduled when appropriate to
discuss these airplanes

WFD Program Overview

Amos Hoggard
Boeing Technical Fellow

The Basic Requirement

• The Industry developed program contains two
distinct issues to be addressed
– A Limit of Validity (LOV) of the Maintenance
Program
– Maintenance Program adjustments to ensure
WFD will be discovered and corrected within the
LOV of the maintenance program

Limit of Validity (LOV)
• LOV is a point (usually measured in cycles) in the
structural life of an airplane where there is
significantly increased risk of uncertainties in
structural performance and the probable
development of WFD
• LOV represents an operational limit based on the
engineering data that supports the maintenance
program. Therefore, all identified service actions are
required for operation up to LOV.
• Any LOV extension requires additional fatigue test
evidence and validation of the maintenance program
for efficacy against WFD and other fatigue damage
• LOV is an airplane level number, referring to the
capability of the total airplane

Methods To Determine LOV

• LOV is determined based upon fatigue test evidence
which consists of data collected from the following
sources:
– 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 Proven Life Techniques
– 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.

Caveats

• For all models, an active aging airplane
program exists, consisting of:
– Mandatory Modifications
– Corrosion Prevention and Control
– Pressure Boundary Repair Assessment
– Supplemental Structural Inspections
• All currently known structural airworthiness
issues, including WFD, have been recognized
and service actions have been initiated under
existing safety processes

Maintenance Program Adjustments

• Definitions
• WFD Susceptible Areas
• Maintenance Program Requirements

Definitions

• There is new terminology for areas
susceptible to WFD.
– ISP - Inspection Start Point - A point in time when
special inspections of the fleet are initiated due to
a specific probability of having a specific
MSD/MED condition
– SMP - Structural Modification Point - A point
reduced from the WFD average behavior, so that
operation up to that point provides equivalent
protection to that of a two-lifetime fatigue test. No
airplane may operate beyond SMP without
modification or part replacement.
– ISP and SMP are component level numbers

ISP and SMP
! Reduction from average
behavior to provide
equivalent protection to a
two lifetime fatigue test
Probability
RESIDUAL STRENGTH

Density
REQUIRED MSD/MED Function
RESIDUAL RESIDUAL Residual
STRENGTH STRENGTH Strength

CRACK LENGTH
MONITORING PERIOD

MSD/MED CRACK
GROWTH acrit WFD

adet

Inspection MSD/MED Structural WFD
Start Point DETECTABLE Modification Point (Average Behavior)
(Lower Bound)

FLIGHT CYCLES

Determination of the Monitoring Period for the Airplane Fleet

WFD Susceptible Areas

• Areas susceptible to the development of
MSD/MED cracking have similar
characteristics
– Similar repetitive details
– Similar Stresses
• Each WFD susceptible area will have it’s own
ISP and SMP
• The AAWG, in it’s 1999 report, identified
sixteen generic structural arrangements that
have developed WFD cracking in the past

Circumferential Joint and Stringer
WFD Example
• Types and possible
location of MSD/MED
– MSD - circumferential
joint
• Splice plate - between
and/or at inner rivet rows
• Skin-forward/aft rivet row
of splice plate
– MED
• Stringer - first fastener of
stringer coupling
• Stringer couplings in
splice plate area

WFD Supplemental Maintenance
Program Requirements
Assessment of
fatigue test evidence
Limit of fatigue
6 ISP6 test evidence
Areas Susceptible to WFD

5 ISP5

ISP4
4 SMP4

ISP3
3
ISP2 SMP2
2
ISP1 SMP1
1
DSO Landings LOV

Model Specific Airplane Data
LOV and Required Maintenance Actions

Single Aisle Products
707, 727, 737, DC-8, DC-9 and MD-80

707/720 LOV - 40,000 Flights
DSO – 20,000 Flights
Test/Teardowns Ancillary Information
• Fuselage • Designed CAR 4b.270, Fail Safe
– Hydro Fatigue Test to 50,000 Flights • Threshold Based SSID Program instituted 1979
– 1978 Fuselage Teardown • Fuselage design similar to 727 but operated at reduced
• Wing cycles
– 1965 Wing and Center Section Teardown • Wing Issues
– 1968 Wing Teardown 13,666 flights – Never Fatigue Tested
– 1973 Wing and Center Section Teardown – Numerous fatigue cracks/mandated service
• Empennage actions
– 1978 Empennage Teardown • Existing Mandated Service Actions Deemed satisfactory
until 40,000 flights

Actions Necessary to Raise LOV
Fatigue test and Teardown of Wing and Empennage

707 Active Airplanes Above DSO Fleet Demonstrated Life - 39,000 cycles
Data as of 11/2002

35
N u m b e r o f A irp la n e s

30
25
20
15
10
5
0
20 - 22 22 - 24 24 - 26 26 - 28 28 - 30 30 - 32 32 - 34 34 - 36 36 - 38 38 - 40
Flight Cycles (1000)

707/720 WFD Maintenance Requirements
DSO/LOV – 20,000/40,000 Flights

Supplemental Maintenance Actions Required to Achieve LOV

707 / 720 WFD Audit Findings (ISPs or SMPs less than LOV)

– 5.1: Lap Splice
• ISP 20,000 flights - Baseline Structure
• AD 91-07-19 (SB 2962) - Mandates modification at 20,000 flights
• Modified structure has no maintenance actions before LOV
– 5.4: Fuselage frame
• ISP 28,600 flights
• AD (SSID) - SSID Items 53-29 & 53-23 satisfy ISP requirements
– Analytical Results for Wing and Empennage show no ISPs below LOV

727 LOV - 100,000 Flights
• 60,000 Flight Full Airframe Fatigue Test (L/N 1-849) • Designed CAR 4b.270, Fail Safe
• 170,000 Flight Complete Fuselage (L/N 1-849) • Certain components fatigue tested
• 1995 – Teardown of Wing and Empennage (46,700 • SSID has been in place since 1983
Flight Cycles) – Currently a threshold based program with 240
– No significant fatigue findings airplanes inspecting (66% are N-Registered)
• 1999 - Teardown of Fuselage following fatigue test – Threshold = 55,000 cycles
(170,000 Flight Cycles - 46,700 flights plus 123,300
pressure cycles)
– Some significant MSD/MED Findings

Fatigue test and Teardown of fuselage with all mandated actions
727-200 Active Airplanes Above DSO
Fleet Demonstrated Life – 106,700
727-200 Line # 1 - 849 727-200 Line # 850 and on
Data as of 11/2002
12

10
Number of Airplanes

8

6

4

2

0
58 - 60 60 - 62 62 - 64 64 - 66 66 - 68 68 - 70 70 - 72 72 - 74 74 - 76 76 - 78 78 - 80 80 - 82 82 - 84 84 - 86 86 - 88

727 WFD Maintenance Requirements


727 WFD Audit Findings (ISPs or SMPs less than LOV)
• 5.1 Lap splice lower row (airplanes L/N 850 and on)
– ISP 35,000 flights
– SMP 55,000 flights
– SB 727-53A222 is applicable
– AD 99-04-22 addresses inspections
– Superseding AD 2002-07-09 mandates modification for airplanes > 48,000
flights
• 5.4 Fuselage frame (test finding)
– SB in work to address immediate concern – Schedule TBD – FAA action
anticipated
• 5.6: Stringer-to-crown skin (Test Finding)
– SB to address inspections due out 2nd Qtr 2003 – FAA action anticipated
• Analytical results for Wing and Empennage show no ISPs below LOV

737 LOV - 100,000 Flights
• 150,000 Flight Fatigue Test of Fuselage “D” Box • Designed FAR 25.571 AMDT 0, Fail Safe
Section • Certain components fatigue tested
• 129,000 Flight Fatigue Test of Aft Fuselage, • SSID has been in place since 1983
removed from Service (59,000 + 70,000) – Currently a threshold based program with 132
• 1987 Teardown Wing plus Center Section, airplanes inspecting (44% are N-Registered)
Forward Fuselage and Empennage (59,000 – Threshold = 66,000 cycles
cycles)
• 1988 Teardown of Aft Fuselage (129,000 cycles)
• Panel tests conducted – Cycled up to 400,000

Fatigue test and Teardown of fuselage with all mandated modifications
737-200 Active Airplanes Above DSO
Fleet Demonstrated Life – 116,100
737-200 Line # 1 - 291 737-200 Line # 292 and on
Data as of 11/2002
16

14

12
Number of Airplanes

10

8

6

4

2

0
74 - 76 76 - 78 78 - 80 80 - 82 82 - 84 84 - 86 86 - 88 88 - 90 90 - 92 92 - 94 94 - 96 96 - 98

737 WFD Maintenance Requirements

737 WFD Audit Findings (ISPs or SMPs less than LOV)
• 5.1 Lap Splice L/N 1-291, Reworked Configuration
– ISP - Within 90 Days or 300 flights, whichever is earlier per
SB 737-53A-1224 (AD 2000-17-04)
– SMP - 70,000 or within 5000 flights not to exceed 4 years of release of SB
– Modification drawing to be provided if purchased
– Lap splice Modification re-inspection L/N 1-291
• ISP - 45,000 flights after modification
• SMP greater than LOV
• 5.1: Lap splice lower row airplanes L/N 292 to 2565
– ISP is not applicable, flaws can not be reliably detected
– SMP - 50,000 flights
– AD mandates modification at 50,000 flights
– 5.1: Lap Modification Re-inspection L/N 292-2565
• ISP - 45,000 flights after Installation
• SMP greater than LOV
• Analytical results for Wing and Empennage show no ISPs below LOV

DC-8 LOV - 70,000 Flights
• Test/Teardown • Ancillary Information
– Fuselage – Designed CAR 4b.270, Fail-Safe
• Forward section hydro fatigue test – – Specific design features for fatigue
140,400 cycles • In-house goals included factors with
– Wing some exceeding 3 DSO
• 130 wing components 140,000 to 560,000 – SID
flight hours • Issued in 1986 as a sampling
• Spar cap splice - 282,770 cycles program
• Center line spar splice - 290,000 cycles • To be converted to a threshold based
– Empennage in 2003
– Still reviewing fatigue test data

Fatigue test and Teardown of Fuselage with all mandated modifications
DC-8 ACTIVE AIRPLANES
245 AIRPLANES, 51 OPERATORS Fleet Demonstrated Life - 47,000 Flights
70
US
60 Foreign
BER O AIRPLANES

50

40
F

30
NUM

20

10

0
10K 15K 20K 25K 30K 35K 40K 45K 50K 55K

FLIGHT CYCLES

DC-8 WFD Maintenance Requirements


• Audit Results To Date (All fatigue test and fleet information reviewed)
– Two Areas of Concern
• Aft Fuselage Longitudinal Splice
– ISP TBD
– SMP TBD
• Wing Chordwise Splice
– ISP TBD
– SMP TBD

DC-9 LOV - 110,000 Flights
• Test/TearDown • Ancillary Information
– Fuselage – Designed CAR 4b.270, Fail-Safe
• Forward section hydro fatigue test – – Specific design features for fatigue
120,000 Cycles • In-house goals included factors with
• Full Fuselage 66,500 (in-service) + some exceeding 3 DSO
142,000 (pressure) Cycles – SID
– Wing • Issued in 1987 as a sampling
• Component fatigue testing program
– Empennage • Converted to a threshold based
• H.S. to V.S. Joint program in 2002

DC-9 ACTIVE AIRPLANES Fleet Demonstrated Life - 143,000 Flights
653 AIRPLANES, 85 OPERATORS
60
US
N U M B ER O F A IR PL A N ES

50
Foreign
40
30
20
10
0
40K 45K 50K 55K 60K 65K 70K 75K 80K 85K 90K 95K 100K 105K
FLIGHT CYCLES

DC-9 WFD Maintenance Requirements


• Audit Results (All fatigue test and fleet information reviewed)
– One Area of Concern
• Transverse skin joint at Aft Pressure Bulkhead
– Prior in-service issue
– Requires additional review
• ISP and SMP TBD

MD-80 LOV - 110,000 Flights

– DC-9 tests are still applicable – Designed to FAR 25.571 amend 10, (Fail-Safe)
– Fuselage – Specific design features for fatigue
• Aft Pressure bulkhead – 31,500 • In-house goals included factors with
(original design) + 150,000 (final some exceeding 3 DSO
design) – SID
– Pylon to Fuselage flex joint • Issued in 1999 as a threshold based
program


M D-80 ACTIV E AIRPLANES
F leet Demo ns t rat ed Life - 59 ,50 0 F lig ht s
200
18 0
16 0
US
NUMBER OF
AIRPLANES

14 0 Foreign
12 0
10 0
80
60
40
20
0
0K 5K 10 K 15K 20K 2 5K 30K 3 5K 40K 4 5K 50 K 55K
FLIGHT CYCLES

MD-80 WFD Maintenance Requirements


• Audit Results - Pending results from DC-9 review

Model Specific Airplane Data
LOV and Required Maintenance Actions

Twin Aisle Products
DC-10/MD-10 and 747 Classic

DC-10/MD-10 LOV - 60,000 Flts or 150,000 Flt Hr.
DSO – 42,000/30,000 Flights

– Full Scale Complete Airplane – Designed FAR 25.571 amend 10, (Fail-
• 84,000 flight cycles, 120,000 hours Safe)
– Wing Component tests – Specific design features for fatigue
• Details improved until 150,000 to – SID
350,000 flight hours achieved • Issued in 1988 as a sampling
– Empennage program
• Spar cap splices • Converted to a threshold based
• Integral stringer panels program in 2002


D C - 10 A C T I VE A I R P L A N ES
Fleet Demonst rat ed Lif e - 38,400 Flight s
70
US
60
Fo reign
50
40
30
20
10
0
5K 10K 15K 20K 25K 30K 35K 40K 45K
F LIG H T C Y C LE S

DC-10/MD-10 WFD Maintenance Requirements
DSO - 42,000/30,000 Flights
LOV – 60,000 Flights /150,000 Hours

• Audit Results (All fatigue test and fleet information reviewed)
– One Area of Concern
• Possible frame area
– Lower section near cargo floor beams
– Multiple frames in a row
– Failed during fatigue tests
– Still investigating
– Preliminary ISP < 30,000 flights
• ISP and SMP TBD

747 Classic* LOV - 30,000 Flts / 115,000 FH
DSO - 20,000 Flights / 60,000 Hours (SP, SR variable)

• 747 Classic Fleet Beyond 24,000 Flights • Ancillary Information
(12/2002 data)
– Designed per FAR 25.571, Amdt 0 (Fail
12 Safe)
– SSID Program Instituted (1983)
10 – Threshold based SSID, Rev. G (2002)
– Maneuver Critical Structure
Number of Airplanes

8 • Not fatigue tested beyond 20,000 flights
-SR • Some fatigue cracks/mandated service
6 -200F
actions
-200 • Test/Teardown
4 -100
– Complete Airframe (1970)
• Fatigue tested to 20,000 flights
2
– Fuselage - Pressure Critical (1990)
• SR fuselage to 40,000 cycles
0
• 747-400 Sec 41/42 to 60,000 cycles
24000- 26000- 28000- 30000- 32000- 34000- 36000-
25999 27999 29999 31999 33999 35999 37999 • Partial teardowns of both articles (1991)
Flight Cycles – Two BS 2360 Pressure Domes (1985)
• Without tearstraps (76,000 cycles)
Fleet Demonstrated Life - 36,900 flights (all 747) • With tearstraps (97,900 cycles)
– Wing Teardown (1989)
• SR wing (15,000 cycles)
*Note: LOV is for -100, -200, -300 and –SP

747 Classic* WFD Maintenance Requirements
DSO - 20,000 Flights / 60,000 Hours (SP, SR variable)
LOV= 30,000 Flights or 115,000 Hours
Supplemental Maintenance Actions Required to Achieve LOV/LOVEXT
• 747 WFD Audit Findings (ISPs or SMPs less than LOVEXT) -100, 200, 300, SP Only
– Tension Tie NDT, ISP at 20,000 flights** / SMP at 30,000 flights
– 7075 U D Floor Beams (at floor panel holes), ISP at 20,000*** / SMP at 23,000 Flights
– 2024 U D Floor Beams, ISP at 20,000***/ SMP at 30,000 Flights
– Lower Lobe Frame, ISP = 14,000** Flights
– Stringer 44 Skin Lap Splice, ISP = 22,000 Flights (Section 41, 42) / SMP = 30,000 Flights
– Other Longitudinal Lap Splices < 0.071” Thick, ISP = 26,000 Flights
– Aft Pressure Bulkhead Web Splices, ISP = 28,000 Flights
– Frames Section 41 (revised frames), ISP = 30,000 Flights
– Circumferential Skin Splices, ISP = 25,000 Flights
• LOVEXT = 35,000 flights (-100, 200, 300, SP) or 135,000 Hours
– Accomplish Mandatory Modifications of all remaining WFD Audit Findings at 30,000 flights
– Perform limited teardowns and refurbishments at LOV (Wing, stabilizer, circumferential Splices)
– Incorporate additional identified SBs
– SSID Rev. G (unless it is already in the maintenance program)
• Actions necessary to raise LOVEXT
– Fatigue test and teardown of airframe with all mandated modifications
# Flights based on fleet demonstrated life and fatigue testing, Hours based on wing equivalent fatigue damage
* Only -100, -200, -300, and -SP specific maintenance actions are presented here
** partial coverage from existing inspections
*** covered by SSID, Rev. G and/or service bulletins

BCA WFD Program
Document Plans

Darrel Jone
Supervisor,
Service Engineering Structures

Operation Beyond LOV

WFD
CPCP RAP SSID SAR
Additional Fatigue Test Evidence

WFD Program
Contents in common
• Susceptible structure with WFD concern
– Picture, description, area number, station location and
airplanes affected
• Inspection Start Point (ISP)
• Inspection methods and intervals
• Structural Modification Point (SMP)
• Description of modification required at SMP
• Other references (Aging Airplane programs, SB’s,
AD’s)
STG Chair Comment No 7

Pre-Amendment 45 Airplanes

New ALS
with LOV
WFD
Requirements

Heritage Boeing
Pre-Amendment 45 Airplanes
• Draft AC provides guidance on
documentation
– Airworthiness Limitations (ALS) required to be a
part of the maintenance manual, as defined in
25.1529 prior to September, 1980.
• Recommend 1 to 1 relationship between
MRBR and ALS
– Integration efforts have created new MRBRs for
some models, while the “original” still exists

Airworthiness Limitations
New document or Section of MPD
ACO Approval Required

Supplemental Corrosion Repair Service Action Widespread
Inspections Prevention and Assessment Requirements Fatigue
For Fatigue Control Program Program (SAR) Damage
Damage (CPCP) (RAP) •Brief (WFD)
(SSID, SID) •Brief description •Brief description description •Brief
•Brief description and background and background and description and
and background •Reference to •Threshold background background
•Threshold document* •Reference to •Reference to •LOV(s)
•Reference to SSID document** document •Reference to
document WFD document

*Or equivalent program which controls corrosion to Level 1 or better
**Or equivalent FAA approved program

Post-Amendment 45 Airplanes

Existing ALS
with LOV
WFD
Requirements

Example of ALS “Pointer”
Service Action Requirements
A necessary prerequisite for continuing any MODEL airplane(s) beyond the number of flights listed in this ALI/ALS as the
initial Limit of Validity (LOV) is an inspection and modification program to prevent structural failure of due to fatigue or
corrosion in areas with known service problems.

The emphasis of this program is on selection of service bulletins for mandatory modification however in some cases existing
evidence will not be sufficient to require mandatory modification but instead lead to a mandating an inspection program.

The MODEL Service Action Requirements Program provides a list of service bulletins on which mandatory modifications must
be accomplished at a specified threshold listed in the document for each service bulletin. Development of the MODEL SAR
has been carried out under the guidance of a MODEL STG/MTG Working Group made up of airline, manufacturer and FAA
personnel. The program provides continuing structural integrity for aging transport airplanes by evaluating current structural
service bulletins and determining which should be mandated prior to an established threshold.

The Service Action Requirements Document referenced below lists the Service Bulletins that define the mandatory inspection
and modification requirements as well as delineating the procedures necessary for their accomplishment. The information
contained in the SAR document describing the effected airplanes and the details of the required work should be considered
only a summary. The most recent revisions to the Service Bulletins should be consulted to determine which airplanes are
affected and for the detailed work scope.

Regulatory Requirement

The FAA has mandated accomplishment of this program by way of Airworthiness Directive. Check Airworthiness Directive
listings for latest Airworthiness Directive that mandates this program.

Documents References

Example

DC-8 Aging Aircraft Service Action Requirements Document Report Number MDC-K1579 and has been approved to meet
the requirements of FAA AD.

Requests for the document should be directed to Boeing Commercial Aviation Group, Data Services Management

Document Contents

• Documentation that is intended to meet
proposed FAA requirements

ALS WFD

LOV Revised
Maintenance
Program

STG Chair Comment No 1, 2, 3, 5

WFD Document Outline

I. Title: Prevention of Widespread Fatigue
Damage
II. Front Matter
a. List of Effective Pages
b. Table of Contents
III. Implementation
a. Introduction of Terms
b. Reference to LOV(s) contained in ALS


IV. Lists of Service Bulletins
a. List 1 required to implement at LOV1
b. List 2 required to implement at LOV2
c. Etc.
V. Lists of Inspections (those not contained in
an S/B)
a. List 1 required to implement at LOV1
b. List 2 required to implement at LOV2
c. Etc.


VI. General Information
a. Program History
b. Descriptions of MSD, MED, etc.
c. Analysis Basis (overview only)
i. Summary of Fatigue Tests and Teardowns
ii. Description of Fleet Demonstrated Life
iii. Determination of ISP and SMP
VII. Glossary of Terms
VIII. References

Document Schedule

• Model technical data • All documents (ALS
– 707 and WFD) complete
– 727 by December 2003
– 737-100/-200
– 737-300/-400/-500
– 747 Classic
– DC-8
– DC-9, MD-80
– DC-10, MD-10

WFD Document Format
SUSCEPTIBLE AREA: FUSELAGE SKIN
LONGTITUDINAL LAP
SPLICES BS 259 TO BS 1016
ABOVE STRINGER S-17

SUSCEPTIBLE AREA NUMBER: WFD.737.001

AIRPLANES AFFECTED: ALL

ISP: TBD

INSP. METHOD AND REF: 1) EDDY CURRENT - NDT
MANUAL D6-37239, PART 6,
53-30-10
2) EDDY CURRENT - NDT
MANUAL D6-37239, PART 6,
53-30-00

INSP. INTERVAL OR REF: 1) TBD
2) TBD

SMP: TBD

MOD. DESCRIPTION AND REF: SB TBD

STG Chair Comment No 4

Operator Caucus Expectations
• Caucus Expectations
– Boeing would like you to understand the concepts
presented today.
– Boeing needs your involvement in this process
and the caucus provides a means for this to occur.
– Boeing expects that you have ideas on the best
way to implement this program, and we would like
to hear them.
• To this end, Boeing has provided copies of all
pertinent reports and results of previous
meetings on this subject for your review and
discussion.

Reconvene Meeting
Operator Out Brief

Widespread Fatigue Damage

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