This document discusses recent developments in aging airplane maintenance programs. It provides background on aging concerns as aircraft accumulate flight hours and cycles. Recent regulatory actions include the widespread fatigue damage rule and aging airplane safety rule. Program developments aim to ensure structural airworthiness as fleets age, through supplemental inspections, corrosion prevention, and addressing combined damage from fatigue and corrosion.

1. 2003
STRUCTURES
CONFERENCE
SERVICE ENGINEERING
COMMERCIAL AVIATION SERVICES
The data contained herein and included herewith are the property of The Boeing
Company and are to be used by the recipient solely for the purposes for which they
are furnished. Recipient agrees not to use this information to make of sell any part or
to disclose these data to any other parties without the expressed written consent of
The Boeing Company.
SE-ACM-4-1-2003
April 2003

3. Contents
Overview ………………………………………………………………………………………….. iv
Glossary …………………………………………………………………………………………… v
Aging Airplane Maintenance Program Developments .......................................................... 1
Damage Tolerance Programs Update.................................................................................. 2
Widespread Fatigue Damage (WFD) ................................................................................... 3
Damage Removal During Structural Repairs........................................................................ 4
Charging for Engineering Services....................................................................................... 5
Structural Health Management (SHM) ................................................................................. 6
737 Lap Joint........................................................................................................................ 7
Nondestructive Testing (NDT) Personnel Training and Certification .................................... 8
737 Classic Fuselage Issues................................................................................................ 9
737 Aft Pressure Bulkhead Issues ..................................................................................... 10
737 BS 178 Bulkhead Issues ............................................................................................. 11
737 Classic Elevator Tab Vibration .................................................................................... 12
737NG Elevator Tab Modification Program ........................................................................ 13
Flap Failure Mitigation ........................................................................................................ 14
Damage Reporting and Repair Approval............................................................................ 15
New SRM General Skin Repair .......................................................................................... 16
Visual Inspection ................................................................................................................ 17
Metalbond Repair Technology Improvements .................................................................... 18
Materials and Processes .................................................................................................... 19
Improving Window Service Life .......................................................................................... 20
Maintaining High Strength Steel ......................................................................................... 21
Structural Repair Training................................................................................................... 22
SE-ACM-4-1-2003 iii

4. Overview
Maintaining airworthiness is the primary goal of all airplane maintenance programs. Having
a good understanding of structural design, repair and maintenance requirements is an
important aspect of a successful maintenance program.
This conference series is intended to raise the participant’s level of structural awareness
and provide an opportunity to discuss in-service structural issues that may impact operators
and the airframe manufacturers. The presentations are starting points for participants to ask
questions and share experiences related to the current topics.
Discussions will update the Aging Airplane Program activities, and the new FAA Interim
Final Rule and associated Advisory Circulars published in December 2002. The new
regulatory action is the result of activities called for by the “Aging Aircraft Safety Act of
1991”. Another important item is the newly developed Widespread Fatigue Damage
program that is the most recent activity in the FAA’s Aging Airplane program. How to apply
the updated damage tolerance requirements of the repair assessment and SSID programs
when a repair or alteration is made to airplane structure is another important discussion
item. Other topics will discuss the importance of removing all damage when performing
repairs, recent changes in body skin lap joint mandatory repair and modification activities
related to 737 airplanes, and ongoing activities to improve SRM skin repair information to
help airlines make more repairs without Boeing assistance.
This conference also includes a demonstration and presentation outlining new activities to
develop structural health monitoring systems for future applications. Adopting this
technology will require the aviation industry to work together to define new ways to address
structural maintenance needs and assumptions as new technology is introduced that can
simplify routine maintenance inspection tasks. As the industry continues to progress, non-
destructive inspection techniques and the associated training for inspectors will continue to
be an item of importance
The closing presentations will also address recent technology developments that will be
added to the SRMs to improve the repair of metalbond parts containing aluminum
honeycomb, provide updates on current materials and processes issues, discuss new MSG-
3 visual inspection terms, and methods to reduce schedule delays related to flight deck and
passenger cabin widow damage.
The attached CD-ROM contains copies of the presentation material.
Operators requiring more information or assistance are encouraged to contact Boeing
through established communication channels and Boeing Field Service representatives.
iv SE-ACM-4-1-2003

5. Glossary
The following are definitions of frequently used acronyms and many of them appear in this document.
737 Classic 737-100/200/300/400/500
737 NG 737-600/700/800/900 DFR Detail Fatigue Rating
AASR Aging Airplane Safety Rule DMS Douglas Material Specification
AATF Airworthiness Assurance Task Force DPS Douglas Process Specification
AAWG Airworthiness Assurance Working Group DSO Design Service Objective
AC Advisory Circular DTR Damage Tolerance Rating
ACO Aircraft Certification Office F Fahrenheit
AD Airworthiness Directive f/c flight cycles
AEG Aircraft Evaluation Group FAA Federal Aviation Administration
AHM Airplane Health Managment FAR Federal Aviation Regulation
Amdt Amendment FFMP Flap Failure Mitigation Program
AMOC Alternative Method of Compliance Flts Flights
AOG Airplane on Ground FOD Foreign Object Damage
APU Auxiliary Power Unit FSBTI Flight Safety Boeing Training
ARAC Aviation Rulemaking Advisory International (Now called Alteon)
Committee FTD Fleet Team Digest
ASI Aviation Safety Inspector ftg fitting
ASNT American Society for Nondestructive FWD Forward
Testing GPS Global Positioning System
ATA Air Transport Association
GVI General Visual Inspection
ATSRAC Aging Transport Systems Rulemaking
HFEC High Frequency Eddy Current
Advisory Committee
BAC Boeing part or process specification HMC Heavy Maintenance Check
BBL Body Buttock Line IACS International Annealed Copper Standard
BCAG Boeing Commercial Airplane Group ISIP Integrated Structural Inspection Program
BMS Boeing Material Specification ISP Inspection Start Point
BOECOM Boeing Communication Messaging IVHM Integrated Vehicle Health Maintenance
System ksi Thousand pounds per square inch
BS Body Station L/P Line Position
CAA Civil Aviation Authority LBL Left Buttock Line
CACRC Commercial Aircraft Composite Repair LCD Liquid Crystal Display
Committee
Cd Cadmium (plating) LFEC Low Frequency Eddy Current
CFRP Carbon Fiber Reinforced Plastic LH Left Hand
CIC Corrosion Inhibiting Compound max maximum
CMM Component Maintenance Manual MDC McDonnell Douglas published document
CMR Certification Maintenance Requirement MED Multi Element Damage
CPC Corrosion Preventative Compound MFEC Medium Frequency Eddy Current
CPCP Corrosion Prevention and Control min minimum
Program MLG Main Landing Gear
CPM Corrosion Prevention Manual mm millimeter
CRES Corrosion Resistant Steel MM Maintenance Manual
D6- Boeing published document MOI Magneto Optic Imaging
DER Designated Engineering Representative MPD Maintenance Planning Data
DET Detailed (Inspection) MRB Maintenance Review Board
SE-ACM-4-1-2003 v

6. Glossary (continued)
The following are definitions of frequently used acronyms and many of them appear in this document
MSD Multiple Site Damage STA Station
MSG Maintenance Steering Group STC Supplemental Type Certificate
N/A Not applicable STG Structures Task Group
NDI Nondestructive Inspection SUD Stretched Upper Deck
NDT Nondestructive Testing SURV Surveillance (Inspection)
NLG Nose Landing Gear SWG Structures Working Group
NPRM Notice of Proposed Rule Making TBD To Be Determined
NSC Notice of Status Change TE Trailing Edge
National Transportation Safety USD United States Dollar
NTSB Board
WFD Widespread Fatigue Damage
OAMP On Airplane Maintenance Program
WISC Working Industry Steering Committee
OEM Original Equipment Manufacturer
WL Water Line
P/N Part Number
PAA Phosphoric Acid Anodize
PSE Principal Structural Element
RAG Repair Assessment Guidelines
RAP Repair Assessment Program
RBL Right Buttock Line
Rev Revision
RH Right Hand
RRC Rapid Response Center
SAE Society of Automotive Engineers
SAR Service Action Requirements
SATCOM Satellite Communications
SB (or S/B) Service Bulletin
SDI Special Detailed Inspection
SDR Service Difficulty Reporting
SFAR Special Federal Aviation Regulation
SHM Structural Health Maintenance
sht sheet
SID Supplemental Inspection Document
SIIA Structural Item Interim Advisory
SL Service Letter
SMP Structural Modification Point
Standard Overhaul Operating
SOPM Procedures
SOW Statement of Work
SRM Structural Repair Manual
SRP Structural Related Problem
SSI Structural Significant Item
Supplemental Structural Inspection
SSID Document
Supplemental Structural Inspection
SSIP Program (or SIP)
vi SE-ACM-4-1-2003

7. Sections
Aging Airplane Maintenance Program Developments . . . . . . . . . . . . . . . . . . . . . . 1
Damage Tolerance Programs Update . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Widespread Fatigue Damage (WFD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Damage Removal During Structural Repairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Charging for Engineering Services . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Structural Health Management (SHM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
737 Lap Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Nondestructive Testing (NDT) Personnel Training and Certification . . . . . . . . . . . . . . . 8
737 Classic Fuselage Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
737 Aft Pressure Bulkhead Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
737 BS 178 Bulkhead Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
737 Classic Elevator Tab Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
737NG Elevator Tab Modification Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Flap Failure Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Damage Reporting and Repair Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
New SRM General Skin Repair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Visual Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Metalbond Repair Technology Improvements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Materials and Processes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Improving Window Service Life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Maintaining High Strength Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Structural Repair Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Maintenance Program
1. Aging Airplane
Developments

8. 1. Aging Airplane Maintenance Program Developments
Objective
To provide inform ation regarding the latest
program developm ents to ensure the continuing
structural airworthiness of airplanes as they age
2
Contents
• Background
• Recent Developm ents
• W idespread Fatigue Dam age
• Aging Airplane Safety Rule
• CPCP NPRM
• CPCP Reporting AMOC
3
The transport airplane fleet has been in
continuous operation over the past 45
Aging Airplane Concerns years, accumulating hours and cycles in
ever increasing numbers. As the fleet
ages, it has become apparent that the
• As airplanes age effects of long term service, primarily
from fatigue and corrosion, increase
• Potential for fatigue cracking increases with continuous usage. The
• Corrosion m ay becom e m ore widespread and simultaneous exposure of a structure to
corrosion and fatigue increases the risk
significantly degrade fatigue performance
of degradation in structural integrity. As
• Tw o or m ore types of dam age in an area can structural problems tend to be
degrade fail-safe or dam age tolerance capability addressed individually, it is a concern
that both types of damage to a structure
be addressed at the same time.
4
SE-ACM-4-1-2003 1-1

9. 1. Aging Airplane Maintenance Program Developments
The concerns regarding the aging fleet
have arisen as a result of the operation
Aging Fleet Issues of a number of airplanes beyond the
original design service objective (DSO).
As shown by the number of high-time
• Econom ic and m arket conditions result in airplanes still in service, the useful
operation of airplanes longer than anticipated economic life of transport category
aircraft has proven to be greater than
• Damage on high tim e airplanes highlighted aging
the original design objective. However,
fleet structural concerns as experience has shown, with incidents
• Horizontal stabilizer occurring on two high-time airplanes,
the condition of the structures as the
• Fuselage skin airframe ages is of concern. Structural
maintenance must now also address the
• Maintenance program s for an aging fleet must effects of aging as well as the normal,
address effects of fatigue and corrosion during routine inspection and repair tasks.
long term operations
5
For airplanes certified prior to the
adoption of Amendment 45 to FAR 25,
Structural Maintenance Program s the aging airplane programs, in
conjunction with the original
maintenance planning data document,
• Maintenance Planning Data provide a comprehensive structures
• Aging Airplane Program s maintenance program.
• Supplem ental Structural Inspections
• Corrosion Prevention and Control Program
• M andatory m odifications and inspections
• Repair Assessm ent Program
• W idespread Fatigue Dam age Program (TBD)
• Service Bulletins
• Other m andated actions
6
There have been several recent
developments with regard to the various
Aging Airplane Program Developm ents aspects of aging airplane structures.
These involve new programs, i.e.,
Widespread Fatigue Damage and the
• W idespread Fatigue Dam age Aging Airplane Safety Rule and changes
to existing programs, i.e., the Corrosion
• Aging Airplane Safety Rule Prevention and Control Program,
previously implemented under the
• CPCP NPRM auspices of the Aging Airplane Safety
Act of 1991.
• CPCP Reporting AMOC
7
1-2 SE-ACM-4-1-2003

10. 1. Aging Airplane Maintenance Program Developments
The issue of Widespread Fatigue
Damage is the sixth initiative originally
W idespread Fatigue Damage (W FD) identified by the Airworthiness
Assurance Task Force (AATF), now the
Airworthiness Assurance Working
• W FD is structural damage which is characterized by: Group (AAWG), as a result of a 1988
accident which raised the issue of aging
• The sim ultaneous presence of cracks at multiple airplane structures. There has been an
structural details, and industry wide approach to defining and
• Have sufficient size and density such that the characterizing widespread fatigue and
structure will no longer m eet its dam age the steps needed to reduce the risk of
tolerance requirement this type of damage occurring. One
byproduct of this effort has been an
• There is a point in airplane operation where the risk understanding that there is a point in the
of uncertainties in structural perform ance and the operation of an airplane where the
probable development of W FD increases maintenance program may no longer
protect the airplane from the increased
risk of widespread fatigue damage.
8
One concept, which has come out of the
research and development effort into
Lim it of the M aintenance Program widespread fatigue, is that of a Limit of
Validity (LOV) of an airplane’s
maintenance program. This is a point in
• Concept of Limit of Validity (LOV) an airplane’s operational life beyond
which there may be insufficient
• Threshold beyond which the airplane structural substantiation data to support
m aintenance program is not considered valid continued operation due to fatigue
• W FD requirem ents to be provided in m odel considerations. In other words, the
specific documents inspections in the maintenance program
may not detect fatigue damage before
• LOV the strength levels are reduced below
the regulatory requirements.
• Inspections The issue of WFD for each model
• Modifications airplane will be addressed in a
document that will contain the LOV, and
any modifications and inspections
required to alleviate the concern over
9 WFD.
The FAA has recently published an
Interim Final Rule and three associated
Aging Airplane Safety Rule (AASR) Advisory Circulars defining the
requirements for damaged tolerance
based maintenance actions for transport
• Interim Final Rule and ACs published in Dec 2002
are result of activities called for by the “Aging airplanes operated under FAR Parts
Aircraft Safety Act of 1991” 121, 129 and 135 (scheduled operations
only). This rule, to be effective
• Rule result of com m ents received from two December 8, 2003, was a result of two
previous NPRM publications previous NPRMs, the latest being
• Further comm ents requested because 1999 issued in 1999. The latest version of the
NPRM w as significantly m odified rule has been greatly modified over the
previous versions and now covers areas
• Com m ent period extended to 5 May 2003 of transport category airplanes not
• Airplanes operated under FARs 121, 129, and 135 previously addressed.
The FAA has extended the original
• Effective 8 Dec 2003 comment period for this rule from the
original closing date of February 4th to
May 5th, 2003.
10
SE-ACM-4-1-2003 1-3

11. 1. Aging Airplane Maintenance Program Developments
There are two paragraphs to the AASR
requirements. The first, Paragraph 1,
Rule Requirem ents, Paragraph 1 contains two parts, an aging airplane
records review and an on-site inspection
of the airplane. The rule requires a
• Records Review s
periodic review of an operator’s
• Periodic review of m aintenance records based maintenance records as called out in
on airplane age FARs 121.368, 129.33 and 135.422.
These FARs list the records information
• Inspections of airplanes that is required to be available at the
time of the review. In addition, each
• Focus on existing aging aircraft requirem ents airplane will have to undergo a physical
inspection of the airframe structure at
• Specified in FARs 121.368, 129.33 and 135.422 the time of the records review.
11
The schedule for the accomplishment of
the maintenance record review and the
Records Review – Part 1 on-airplane inspection will depend upon
the age of the airplane on 08 December
2003; the date the rule becomes
• On 8 Dec 2003, for airplanes effective. At that time, operators with
• Exceeding 24 years in service, 1 st records airplanes over 24 years of age will have
review m ust occur before 5 Dec 2007 4 years to complete the records review.
For airplanes between 14 and 24 years
• Exceeding 14 years in service but less than of age on that date, the records review
24 years, 1 st records review m ust occur must be accomplished with 5 years. If
before 4 Dec 2008 an airplane is less than 14 years old, the
records review must be performed by
• Less than 14 years in service, no later than the start of the airplane’s 20th year in
5 years after the start of 15th year in service
service.
• For all airplanes, records review will be Repeat records reviews must be done
repeated every 7 years thereafter every 7 years thereafter.
12
The second part of the records review
involves an on-airplane inspection of the
Records Review - Part 2 airframe structure. This inspection is to
be accomplished in conjunction with the
review of the maintenance records. The
• Physical inspection of the airplane either by FAA FAA will require at least 60 days notice
Adm inistrator or Designee of when the airplane will be available for
the inspection. A representative of the
• Accom plished in conjunction with the FAA Administrator, such as an Aviation
m aintenance records review Safety Inspector (ASI), or an FAA
Designee, will perform the inspection.
• Adm inistrator will require notification 60 days The FAA Designee will be a Designated
prior to date that airplane and its records will be Airworthiness Representative (DAR).
available for inspection
13
1-4 SE-ACM-4-1-2003

12. 1. Aging Airplane Maintenance Program Developments
The second paragraph of the AASR
specifies the requirement for the
Rule Requirem ents, Paragraph 2 maintenance program for an airplane to
include damage tolerance based
inspections and procedures. The
• Supplem ental Inspections
specifics of this part of the AASR are
• Require a dam age tolerance based spelled out in FARs 121.370a, 129.16
m aintenance program by 5 Dec 2007 and 135.168 (scheduled operations
only).
• Affects airplanes operated under FAR 121,
129, and 135
14
The damage tolerance based inspection
program required by this rule which
Supplemental Inspection must be incorporated in an operator’s
maintenance program is intended to
maintain the continued airworthiness of
• A dam age tolerance based program m ust be in both the original airframe and those
place and operating with three elem ents which: structures altered by repairs or
• Proactively inspects for dam age to the as modifications. Any repairs or
delivered structure to m aintain continued modifications made to an airplane must
airworthiness* have damage tolerance based
• M aintains continued airworthiness of a inspections included in the existing
repaired airplane maintenance program.
• Establishes a new or revised program for
areas of the airplane that undergo m ajor
m odification
* Repairs to areas affected by the SSID or ALI require damage tolerance
based maintenance program s
15
In one form or another, the maintenance
programs for all Boeing model airplanes
Supplemental Inspections include damage tolerance based
inspection requirements. For the pre-
amendment 45 certified airplanes, these
• For all Boeing products, programs will exist are contained in the various aging
• Pre-am endm ent 45 airplanes airplane programs mandated by
airworthiness directives or operational
• Service Action Requirem ents rules. The post-amendment 45 airplanes
• CPCP contain these requirements as a result
of their certification basis.
• SSIP
• Repair Assessm ent Program
0 Fuselage pressure boundary
• Post Am endm ent 45 airplanes
• Certification basis requirem ent
16
SE-ACM-4-1-2003 1-5

13. 1. Aging Airplane Maintenance Program Developments
A number of operators commented that
the existing aging airplane programs
Com m ents on Rule should be sufficient to comply with the
intent of the rule. The FAA partially
agreed, but stated that these programs
• Operators com m ented that existing Aging Airplane only satisfy part of the requirements of
Program s provide m eans of com pliance the final rule. The FAA’s position was
that the SSIPs only address certain
• FAA has interpreted additional issues and portions of an airplane's structure while
responses that operators “m ust establish the damage-tolerance-based SSIPs
dam age-tolerance-based SSIPs or service- specified by the rule address the entire
history-based SSIPs, as applicable, for m ajor primary structure of an airplane,
repairs, m ajor alterations, and m odifications to including the baseline structure, and
structures not affected by the repair major repairs, major alterations, and
assessment program , such as fuselage fram es modifications to baseline structure. For
and longerons, and wing and em pennage that reason, the FAA feels that the
structures” SSIPs must go beyond the current aging
airplane programs to encompass the
entire airframe.
17
The FAA expressed concern that a
number of derivatives of existing
Other FAA Issues airplanes are not now covered by a
supplemental inspection program. They
are also concerned by the fact that there
• SSID program s on som e 737, 747 m odels and are a number of major repairs or
MD-80 have yet to be mandated modifications that may now require an
assessment to determine any damage
• Unknow n number of “m ajor” repairs and tolerance based inspection
m odifications that may now require dam age
requirements under this rule. These
tolerance based inspections
include service bulletin and STC repairs
• Service Bulletins and modifications.
• STCs
18
1-6 SE-ACM-4-1-2003

14. 1. Aging Airplane Maintenance Program Developments
The FAA held a public meeting to review
the activities of an FAA team that was
FAA SSID AD Standardization Review chartered to gain knowledge of the
damage tolerance based inspection
aspects of the Aging Aircraft Programs
• Public m eeting on 27 Feb 2003
and to make recommendations
• FAA SSID Team m ade 8 recom m endations, regarding how the FAA should handle
including the Supplemental Structural Inspection
Document (SSID) Airworthiness
0 Assessm ent compliance time to 18 months Directives (ADs). The team addressed
the ADs currently existing for the 727,
0 Three step assessm ent process 737, DC-8, DC-9 and the DC-10
airplanes. The result of the review was
• Relationship betw een SSID ADs and AASR
eight recommendations to standardize
• Requirem ents for repairs, alterations and the SSID ADs, including extending the
m odifications under these regulations assessment time for repairs, alterations
and modifications to 18 months.
0 Have dam age tolerance based inspections The meeting also addressed the
relationship between the SSID ADs and
19 the AASR as both regulations require
damage tolerance inspections for
repairs, alterations and modifications.
For a copy of the FAA SSID Team
report, see the following website:
http://www1.faa.gov/certification/aircraft/
agingaircraft/ssid/ssid/index.htm
It is felt that the post-amendment 45
Boeing models will meet the intent of the
Effect on Boeing Models – Post-Am dt 45 AASR. These models were certified
under damage tolerance rules and have
damage tolerance based inspections in
• 757, 767, 777, 737-700C/900, MD-11, MD-90, 717 their maintenance programs.
• Certification basis fulfills intent of the AASR
for dam age tolerance based m aintenance
program s
0 All have SSIPs in form of Airw orthiness
Lim itation Instructions (certain models have
ADs for early L/Ps)
0 All require dam age tolerance based repairs
and m odifications
20
SE-ACM-4-1-2003 1-7

15. 1. Aging Airplane Maintenance Program Developments
It is the FAA’s position that meeting the
requirements of FARs 121.370, 125.248
Effect on Boeing Models – Pre-Am dt 45 and 129.32 is an acceptable means of
compliance with the final rule only to the
extent that these requirements address
• 707, 720, 727, 737-100 through –800*, 747-100
repairs to the fuselage pressure
through -400, DC-8, DC-9, MD-80, DC-10
boundary for the noted airplanes. The
• Required by FARs to have a RAP FAA states that operators will have to
accomplish additional work to fully
0 Applicable only to fuselage pressure boundary comply with this rule. Damage
tolerance based SSIPs will have to be
• Rule w ill require additional damage tolerance established for major repairs, major
based inspection program for structures not alterations, and modifications to
addressed by RAP structures not affected by the repair
assessment program, such as fuselage
frames and longerons, and wing and
empennage structures.
* Except 737-700C
21
Reporting of Level 2 and 3 corrosion
occurrences was originally required to
CPCP Reporting AM OC validate baseline CPCP programs.
However, the baseline program has not
been changed as a result of CPCP
• CPCP ADs required quarterly reporting of Level 2 reports. The CPCP is operator adjusted
and follow -up of Level 3 reporting on a quarterly to meet specific operator program
basis needs. Operators are also required to
report corrosion occurrences of
• Corrosion reporting also required per FAR 121.703 corrosion per FAR 121.703(a)(15).
Operators’ felt reporting to Boeing was
• Boeing proposed that reporting corrosion per FAR duplicate reporting requirements for the
121.703 would fulfill the AD reporting requirem ents same occurrence.
Reporting Levels 2 and 3 instances of
• FAA concurred and issued an AMOC corrosion per FAR 121.703(a)(15) is
• Separate reporting to Boeing no longer required now an AMOC to paragraph D of ADs
90-25-07, 90-25-03, 90-25-01 and 90-
25-05. A copy of this AMOC is included
as Addendum 1-1.
22
1-8 SE-ACM-4-1-2003

16. 1. Aging Airplane Maintenance Program Developments
The FAA has released a CPCP NPRM,
Notice No. 02-16, Docket No. FAA-
CPCP NPRM 2002-13458, which is applicable to
airplanes operated under FARs 121,
129 or 135 (scheduled service only).
• Released in Federal Register 3 Oct 2002 This proposal would impose
• Requires im plem entation of an FAA approved requirements to prevent the spreading
CPCP w ithin 2 years of rule effective date of corrosion in all other airplanes
operated under part 121, all other U.S.-
• Applicable to FAR 121, 129 and 135 operators registered multiengine airplanes
operated under part 129, and all other
• Baseline program to control corrosion so that multiengine airplanes in scheduled
dam age does not exceed Level 1 operations under part 135. In other
words, this proposed rule would apply to
• Existing CPCPs will satisfy rule
most airplanes not currently covered by
• Com m ent period closed 1 Apr 2003 AD, in addition to those previously
covered by AD. It is unknown if the
FAA’s intent is to have these proposed
FARs supercede the current CPCP
23 ADs.
The rule would require that a baseline
program be established that will control
corrosion such that it will not exceed
Level 1 for the affected airplanes. For
Boeing airplanes, the existing CPCPs
will satisfy the intent of the rule.
Sum mary
• M aintain continued airworthiness with
• An effective scheduled maintenance program
• Com pliance w ith all mandated actions
• New rules are being established to apply dam age
tolerance and corrosion program s to more of the
transport airplane fleet
• M aintenance program m ust be valid for extended
operations
• Structural m aintenance activities will increase as
airplanes age
24
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20. 1. Aging Airplane Maintenance Program Developments
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Aging Aircraft Program Supplemental Structural Inspection
Document (SSID) Review -Final Report- September 2001
Extracted from FAA website:
http://www1.faa.gov/certification/aircraft/agingaircraft/ssid/ssid/index.htm
Table of Contents
Executive Summary
Introduction
List of Acronyms
Phase I Discussion
Phase I List of Recommendations
Phase I Recommendation Discussion
Phase II Discussion
Phase II Recommendations and Discussion
Appendices
A 727 Final Rule
B MD-80 Draft NPRM (not attached)
C Team Charter (not attached)
D Interview Notes (not attached)
E 727 and MD-80 AD Comparison
F Table of Advantages and Disadvantages
G Generic SSID/SID AD
H Compliance Time Comparison
I Special Inspection Criteria
J Flyable Crack Limits Memo (not attached)
K Summary of Aging Aircraft Initiatives
L Phase II SSID Summary’s
Executive Summary
This report describes the activities of a Team that was chartered to gain knowledge of
the damage tolerance based inspection aspects of the Aging Aircraft Programs and to
make recommendations regarding how the FAA should handle the Supplemental
Structural Inspection Document (SSID) Airworthiness Directives (ADs). During phase I,
the team addressed the Boeing 727/737, MD-80, and McDonnell Douglas heritage
model airplanes, and made recommendations regarding the differences in the treatment
of repairs and modifications in the respective SSID Airworthiness Directives (AD).
During phase II, the team addressed the remaining 6 model aging aircraft (Boeing
707/720, Fokker F-28, Lockheed L-1011, BAe 1-11, Airbus A300, and CASA C-212),
and made recommendations for changes that should be incorporated into these
remaining SSID ADs.
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21. 1. Aging Airplane Maintenance Program Developments
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This report also describes the process used to develop recommendations that are
intended to standardize the repair and modification instructions in the SSID AD’s.
Recommendations for both phase I and phase II are listed in this report with a
justification provided for each. A Generic SSID AD implementing the recommendations
for repairs and modifications are provided in this report to illustrate how standardized
instructions and compliance times could be incorporated into AD format.
Introduction:
This report is the product of a team that was chartered by the ANM-110 and Aging
Aircraft Program Managers. From this point on this team will be referred to as the
“Team”. The Team was chartered to obtain a fundamental understanding of the
damage tolerance based inspection aspects of the Aging Aircraft Programs and to make
recommendations in the following two phases of activities.
Phase I of the Team’s charter is defined as follows:
1. Recommend a course of action to address the current differences in the
treatment of repairs and modifications (especially STC’s) installed both before
and after the effective dates of the AD’s for the 727/737 models and DC-8, DC-9,
and DC-10 models. Also recommend a course of action for treatment of the draft
MD-80 SSID NPRM prepared by the LAACO. If the team’s recommendation is
that the mandated programs for these models should be different, the team
should provide full explanations and justification for the differences.
2. The team should also determine, in consideration of the general rulemaking,
whether changes to the AD’s that mandate SSID programs are necessary.
Phase II of the Team’s charter consists of the following activities:
1. Recommend how the FAA should handle SSID AD’s on all of the 11 model aging
aircraft (Boeing, Douglas, Lockheed, Airbus, Fokker, CASA, and British
Aerospace). If the team’s recommendation is that the mandated programs for
the eleven Aging Aircraft models should be different, the team should provide full
explanations and justification for the differences.
It’s important to note that CASA was not identified in the SSID Team Charter as
being one of the aging model aircraft. However, the Team became aware that
CASA had produced a SSID document for the C-212, which had been subsequently
mandated by a FAA AD. Therefore, during Phase II the Team gathered information
on the CASA C- 212 SSID and FAA AD, then evaluated them along with the other
aging aircraft. The addition of CASA resulted in the Team evaluating a total of 12
aging aircraft models during both Phase I and Phase II.
Even though the Team reviewed the basic Boeing and Douglas SSID programs
during the Phase I activities, the Team focused on the difference in the AD
mandated implementation of the two basic programs, primarily in the areas of
repairs, alterations and STC modifications. The details about the process and
activities that the Team took in order to establish recommendations are in the
Discussion section of this report.
The Team’s recommendations and justification for the recommendations for both phase
I, and phase II of the Team’s review are provided in the Recommendations section of
this report. The appendices of this report contain several tools that the Team developed
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22. 1. Aging Airplane Maintenance Program Developments
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and used to establish the Team’s recommendations. The Appendix section also
contains a Generic AD that demonstrates how the Team’s recommendations can be
implemented into a standardized AD.
List of Acronyms and Definitions:
CPCP Corrosion Prevention and Control Program (Reference Appendix K for
details of this program)
DGAC Dirección General de Aviación Civil (The Spanish Airworthiness
Authorities responsible for the State of Design for CASA)
DGAC (The French Airworthiness Authorities responsible for the State of Design
for Airbus)
DSG Design Service Goal
PSE Principal Structural Element
RAP Repair Assessment Program (Reference Appendix K for details of this
program)
RLD Rijksluchtvaartdienst (The Netherlands Airworthiness Authority
responsible for the State of Design for Fokker)
SID Supplemental Inspection Document-Sometimes the Acronym SID is
interchanged with SSID
SIP Structural Integrity Program
SRP Sampling Rotational Program
SSID Supplemental Structural Inspection Document-Sometimes the Acronym
SSID is interchanged with SID
SSD Structurally Significant Detail
SSI Structurally Significant Item
Phase I Discussion:
The process used to develop the recommendations intended to standardize the repairs
and modifications paragraphs of the SSID/SID AD's, where necessary, took several
meetings and telecons over a period of five months. Prior to making any
recommendations, the Team conducted interviews with FAA engineers, FAA national
resource specialist, FAA aging aircraft program manager; FAA aircraft evaluation
group, FAA legal counsel, Boeing north engineers; Boeing Long Beach engineers
(MDC), and engineers from an airline operator (who requested to remain anonymous).
The interviews were conducted in person when feasible and by telephone when time
and distance was an obstacle. These interviews helped the Team to gain a
fundamental understanding of the basic SSID/SID programs and the AD’s that mandate
them. Detailed notes from these interviews are located in Appendix D of this report.
The Team met several times in both Los Angeles and in Seattle to conduct the review of
the SSID/SID AD’s and their differences. During these meetings the Team developed
several tools to assist in the decision making process. One tool that was developed
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23. 1. Aging Airplane Maintenance Program Developments
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was a table comparing the 727/737 AD’s and MD-80 draft NPRM paragraphs related to
repairs, alterations and STC modifications. This comparison table was used
throughout the review and can be found in Appendix E of this report. The comparison
table was used to assist the Team in identifying and listing the differences between the
727/737 AD’s and the MD-80 draft AD. From this list of differences, the Team identified
and created a table of advantages and disadvantages based on the information gained
from the interviews. The table of advantages and disadvantages was used to identify
what worked well from each AD. The table of advantages and disadvantages is
located in Appendix F of this report. This table was used in the formulation of the
Team’s recommendations.
A Generic SSID/SID AD implementing the Team’s recommendations was drafted to
assist in illustrating the recommendations and was used as a tool to ensure the
recommendations could be implemented in AD format. The Generic AD paragraphs
were limited to those with requirements for inspection program revisions related to
repairs and modifications. The development of the Generic AD helped the Team to
fine-tune the final recommendations. The Team recognizes that the 727/737 AD’s and
MDC SID AD’s will continue to be different in the areas where the basic SSID/SID
inspection requirements are specified. However, for repairs and modifications, the
SSID/SID AD’s may use the standardized compliance time in the Generic AD. The
Generic SSID/SID AD is located in Appendix G of this report.
The Team is in concurrence with 8 final recommendations resulting from the evaluation
of the 727/737 and MDC SSID/SID AD’s. In parallel with the development of the
Generic SSID/SID AD, the Team looked at each recommendation in detail and provided
a rational justification for each recommendation.
A summary of each of the aging aircraft initiatives is included in Appendix K of this
report. The aging aircraft initiatives include the Repair Assessment Program,
Widespread Fatigue Damage, Aging Airplane Safety Initiative, Corrosion Control
Program, and Supplemental Structural Inspection Programs. It was important for the
team to become familiar with these initiatives, since some of them have requirements
which can overlap the SID requirements
Phase I List of Recommendations:
The following is a list of recommendations that the Team concurs should be considered
for revision of the Boeing 727/737 and McDonnell Douglas heritage model airplanes
SSID/SID AD’s.
Recommendation 1: Add a requirement to perform a damage tolerance assessment for
repairs and modifications accomplished after the effective date of the ADs using a
standardized compliance time of 18 months.
Recommendation 2:
a) Standardize to a 3-step damage tolerance assessment process for new repairs,
STC’s and other design changes.
b) Provide a standardized description of an acceptable damage tolerance
assessment methodology, similar to Note 6 of the 727 AD, by referencing
Advisory Circular 91-56A.
Recommendation 3:
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24. 1. Aging Airplane Maintenance Program Developments
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a) Eliminate the term “SSI created” in the 727/737 AD’s.
b) Criteria for determining which repaired, altered or modified structure requires
damage tolerance based special inspections should be jointly developed by the
cognizant ACO’s, and added to the AD’s.
Recommendation 4: Standardize the compliance time to perform a damage tolerance
assessment for repairs and non-STC design changes accomplished before the effective
date of the AD's as follows:
a) For airplanes that have already exceeded their SSID threshold the compliance
time should be 18 months after the effective date of the AD.
b) For airplanes that have not reached their SSID threshold, the compliance time
should be 18 months after the SSID threshold, or within 5 years after the
effective date of the AD, whichever occurs first.
Recommendation 5: Provide a description in the AD’s detailing the information to be
included in the operators FAA-approved maintenance or inspection program.
Recommendation 6: Standardize the acceptance of the Repair Assessment Guidelines
(RAG), where applicable, as a method of compliance to recommendation 1 and 4
requirement for a damage tolerance assessment of repairs. The RAG should only be
applicable for those repairs found on the fuselage pressure vessel.
Recommendation 7:
a) Standardize the compliance time to perform a damage tolerance assessment for
STC’s accomplished before the effective date of the AD’s similar to paragraph
(d)(2) of the 727/737 AD’s, and remove paragraph (d)(1) from the 727/737 AD’s.
b) Include a note similar to Note 7 in the 727/737 AD’s, which provide FAA
expectations for the contents of the compliance plan specified in paragraph
(d)(2).
Recommendation 8: Accomplish a separate evaluation of the Damage Tolerance
National Resource Specialist concerns about the basic SSID/SID program.
Phase I Recommendation Discussion:
Recommendation 1: Add a requirement to perform a damage tolerance
assessment for repairs and modifications accomplished after the effective date of
the ADs using a standardized compliance time of 18 months.
The compliance time specified in paragraph (g) of the 727/737 AD for revision of the
FAA-approved maintenance or inspection program is 12 months for all repairs and
modifications installed after the effective date of the AD. In contrast, the compliance
time specified in paragraph (d) of the MD-80 draft NPRM for revision of the FAA-
approved maintenance or inspection program is 18 months. The 18 month compliance
time in the MD-80 draft NPRM was based upon the compliance time that the LA ACO
has been using for approval of the damage tolerance assessment of repairs on PSE's.
This compliance time is linked to the 3-stage approval process, which is discussed in
detail under recommendation 2 (a). Until about 5 years ago, the LA ACO had been
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25. 1. Aging Airplane Maintenance Program Developments
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using a 12 month compliance time for the approval of the damage tolerance
assessment. However, as the result of a large increase in the number of repairs that
needed to be assessed for damage tolerance, McDonnell Douglas (MDC) requested
that the LA ACO extend this compliance time to 18 months. They cited difficulties in
meeting the 12 month compliance time. MDC justified their request with the argument
that a repair, which has been shown to meet static strength requirements, will inherently
be able to resist fatigue cracking for a period greater than 18 months. The LAACO
concurred with MDC and has since routinely required approval of the damage tolerance
assessment 18 months after accomplishment of the repair.
The Seattle ACO does not concur with the use of an 18 month compliance time for the
completion of damage tolerance assessment (DTA) of repairs and modifications for the
following reasons:
1. The 18 month compliance time is not consistent with the guidelines established
in AC 25.1529-1, where it states that a time period not to exceed 12 months is
generally adequate for most structural repairs.
2. The airline operators are not required to retain records for minor repairs longer
than 12 months, which will result in the operator’s losing track of the repair date
and of when the DTA is to be completed. In addition, the operator’s FAA
maintenance inspectors would not be able to enforce an 18 month compliance
time since the operators were not required to maintain the records longer than 12
month.
The Team could find no valid argument against the MDC statement that a repair,
which has been shown to meet static strength requirements, will inherently be able
to resist fatigue cracking for a period greater than 18 months. The Team further
reviewed AC 25.1529-1 and could find no technical justification for the 12 month
compliance time providing any significantly higher level of safety than the 18 month
compliance time used by the LAACO.
The Team interviewed Mr. Jim Dodge from ANM-230 to find out what operating rules
would require the airline operators to maintain records longer than 12 months.
The Team explained the concerns of the Seattle ACO and asked if the 18 month
compliance time would be difficult for the FAA maintenance inspectors to enforce.
Jim explained that 14 CFR Part 39.3 states that no person may operate a product
except in accordance with the requirements of the AD. Therefore, since the SSID
will be mandated by AD's, the operators would be required to comply with the terms
and limitations of the AD. However, FAR 121.380 only requires that records of
major repairs be kept for a maximum period of 12 months. Due to the allowance in
the regulations that only require carriers to retain major repair records for 12 months,
Jim indicated difficulty may result in enforcing compliance with the AD since the
operator could indicate that an assessment was accomplished for a repair, and that
there was no affect to the structure thus requiring no further FAA approval. The
Team had similar discussions with engineering managers at separate airlines, with
each responding that they believed they would have to maintain the records longer
than 12 months if the AD specified a longer compliance time for an assessment to
be accomplished.
After evaluating AC 25.1529-1 and considering the interviews with the airline
engineers and Jim Dodge, the Team is in agreement that an 18 month compliance
time for the approval of the DTA is justified and does not reduce the level of safety.
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26. 1. Aging Airplane Maintenance Program Developments
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Therefore, the Team recommends that the SSID AD’s specify a standardized
compliance time of 18 months for the accomplishment of a DTA for repairs and
modifications.
Recommendation 2:
a) Standardize to a 3-step DTA process for new repairs, STC’s and other
design changes.
b) Provide a standardized description of an acceptable damage tolerance
assessment methodology, similar to Note 6 of the 727 AD, by referencing
Advisory Circular 91-56A.
Recommendation 2(a)
For new repairs, STC’s and other design changes installed after the effective date
of the AD, paragraph (g) of the 727/737 AD’s states: “Within 12 months after that
modification, alteration, or repair, revise the FAA-approved maintenance or
inspection program to include an inspection method and compliance times for each
new or affected SSI, and to include the compliance times for initial and repetitive
accomplishment for each inspection.”
During interviews with SACO engineers, the Team learned that SACO issued an
AMOC to the 727/737 AD’s that allows the use of a two-step procedure for damage
tolerance assessment of repairs. The two-step approval process consists of the
following:
1. Evaluate the repair to determine the inspection threshold within 12 months of
installation.
2. Prior to the inspection threshold or within 12 months after accomplishing the
inspection at the SSID threshold, whichever occurs first, complete the damage
tolerance assessment to determine the repetitive inspection intervals based on
the inspection method.
During interviews with LAACO engineers, the Team learned that LAACO has
accepted a three-stage process for approval of damage tolerance assessment of
repairs. This three-stage approval process consists of the following:
1. Static strength approval prior to further flight.
2. Damage tolerance assessment approval within 18 months of the static strength
approval.
3. Inspection method and repeat interval approval 2 years prior to the inspection
threshold determined by the damage tolerance assessment.
The concepts of the two methods are similar with some minor differences. SACO
does not include the first step of the LAACO three-phase process since damaged
SSID items per SACO have to be repaired using methods approved by FAA, while
the LAACO AD’s require that PSE’s found cracked during a SID inspection be
repaired in a manner approved by the manager of the LAACO. The other minor
difference between the two approval processes is that LAACO allows 18 months after
repair to establish the inspection threshold, while SACO allows 12 months after repair
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27. 1. Aging Airplane Maintenance Program Developments
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to establish the inspection threshold. Additionally, LAACO requires that the
inspection method and intervals be approved 2 years prior to reaching the inspection
threshold, while the SACO method requires the inspection method and intervals be
established prior to the inspection threshold or within 12 months after accomplishing
the inspection at the SSID threshold, whichever occurs first.
Both the SACO two-step approval process and the LAACO three stage approval
process are based on the two-stage structural evaluation concept that is discussed in
Advisory Circular (AC) 25.1529-1. The AC states that a time period not to exceed 12
mo. is generally adequate for most structural repairs. Until about 5 years ago,
LAACO had been using a 12 month compliance time for the approval of the damage
tolerance assessment. However, as the result of a large increase in the number of
repairs that needed to be assessed for damage tolerance, McDonnell Douglas (MDC)
requested that the LAACO extend this compliance time to 18 months. They cited
difficulties in meeting the 12 month compliance time. MDC justified their request with
the argument that a repair, which has been shown to meet static strength
requirements, will inherently be able to resist fatigue cracking for a period greater
than 18 months. The LAACO concurred with MDC and has since routinely required
approval of the damage tolerance assessment 18 months after accomplishment of
the repair.
As similarly discussed in recommendation 1, the team could find no technical
justification for the 12 month compliance time described in AC 25.1529-1 providing
any significantly higher level of safety than the 18 month compliance time approved
by the LAACO. Therefore, the team is in agreement that the use of an 18 month
compliance time rather than a 12 month compliance time for the approval of the
damage tolerance assessment is justified and does not reduce the level of safety.
The 727/737 AD’s require that new inspection methods and compliance times for
SSI’s created or affected by a repair, STC, or other design change be approved by
the Manager, Seattle Aircraft Certification Office. The MD-80 draft NPRM requires
that new inspection methods and compliance times for PSE’s affected by a repair,
STC, or other design change be approved by the Manager, LAACO. The approval of
a new inspection method and compliance time by the airplane’s type certificate
managing ACO may not make sense for STC alterations. The STC may be issued by
an ACO other than the airplane’s type certificate managing ACO. In this case, all of
the data supporting the STC and the ACO engineering awareness of the STC
modification resides in the ACO that is managing the STC.
Therefore, the team recommends that the approval of the inspection method and
compliance time for STC alterations be done by the STC managing ACO and that
approval of the inspection method and compliance time for repairs and non-STC
design changes be done by the airplane’s Type Certificate Managing ACO.
The Team also recommends that a standardized approval process for new repairs,
STC’s and other design changes be used by adopting the three-stage approval
process as outlined above. The Team recommends that SACO and LAACO continue
approval of the first phase of the process as they feel appropriate for individual
SID/SSID programs. The Team recommends the use of an 18-month compliance
time for the damage tolerance assessment because it provides an adequate amount
of time for the operators to conduct the assessment as discussed in
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28. 1. Aging Airplane Maintenance Program Developments
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Recommendation 1. Even though the 18 month compliance time is not consistent
with the guidance contained in AC 25.1529-1, the differences can be described in the
preamble of the SSID/SID AD’s, which is appropriate since the AD establishes new
rulemaking. The Team concurs with the approach of requiring determination of the
inspection method and repeat intervals to be established 2 years prior to reaching the
inspection threshold. The Team concluded that relating the compliance time for
establishment of the repair inspection method and repeat intervals to the established
inspection threshold is reasonable. The 2-year compliance time will ensure that the
repair inspection method and repeat intervals are in place when the repair inspection
threshold is reached.
The AD’s should clarify that the DTA for repairs must be approved by the ACO
responsible for the type design of the aircraft, and that the DTA for STC’s must be
approved by the ACO, which issued the STC. This information should be
communicated to all ACO’s if the Manager of the Transport Airplane Directorate
approves the recommendations in this report.
Recommendation 2(b)
Note 6 of the 727/737 AD’s specifies that the inspection methods and compliance times
should be determined based on a damage tolerance assessment methodology, such as
that described in FAA Advisory Circular No. 91-56, Change 2 dated April 15, 1983. In
contrast, the MD-80 draft NPRM does not specify what is considered an acceptable
damage tolerance assessment methodology for determining the inspection methods
and compliance times.
The Team recommends that the AD’s contain a standardized note, similar to Note 6 of
the 727/737 AD, that specifies an acceptable damage tolerance assessment
methodology for determining the inspection methods and compliance times. The Team
further recommends the standardized note reference the methodology contained in FAA
Advisory Circular No 91-56A, dated April 29, 1998.
Recommendation 3.
a) Eliminate the term “SSI created” in the 727/737 AD’s.
b) Criteria for determining which repaired, altered or modified structure
requires damage tolerance based special inspections should be
jointly developed by the cognizant ACO’s, and added to the AD’s.
Recommendation 3(a)
The Team noted that the 727/737 AD’s used the terms “new SSI” and “created SSI” in
Paragraphs (d)(1), (e), (g), and in note 7. This term was used where a repair, alteration
or modification affected the aircraft structure such that damage tolerance based special
inspections are required. The Team further noted that the MD-80 draft NPRM did not
address any repaired, altered or modified structure that would require damage tolerance
assessment other than the PSE’s that had been affected by repairs, alterations and
modifications. The Team recognized that the Boeing and MDC basic SSID/SID were
developed differently and use two different terms for structure that requires
supplemental inspections. Because of these differences, it is important that the terms
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29. 1. Aging Airplane Maintenance Program Developments
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SSI created and PSE created not be used in the AD’s to prevent association with the
OEM’s basic programs.
The Team recommends that the term “new SSI” and “created SSI” not be used in the
727/737 AD’s. The SSID/SID AD’s should simply address the affected structure as
structure that requires damage tolerance based special inspections”.
Recommendation 3(b)
Paragraph (d)(1) and (e) of the 727/737 AD’s require assessment of the damage
tolerance characteristics of each SSI created by a repair or design change. The
operators must revise their FAA-approved maintenance or inspection program to
include inspection methods and compliance times for each SSI created. The MD-80
draft NPRM does not contain instructions for a PSE created by a repair or an alteration
or modification. However, the preamble of the MD-80 draft NPRM states that once the
Aging Aircraft Safety Act becomes a final rule the MD-80 AD will be superseded to
address all structural repairs, alterations and modifications and not just those that
“affect” a PSE.
During interviews, LAACO engineers indicated that the MD-80 draft NPRM takes into
account the proposed Aging Airplane Safety Rule, which has been issued as an NPRM
(Notice 99-02). This rule will require that within 4 years after the effective date that the
operators maintenance program include damage tolerance based inspections and
procedures, for all repairs and modifications, including STC’s. This rule will be
applicable for all Parts 121, 129, and 135 operating rules. The Aging Airplane Safety
Rule is expected to become a final rule in February of 2001.
The Team believes that it is important that all repairs, alterations and modifications to
airplanes with mandated SSID/SID programs have a damage tolerance assessment
accomplished in order to determine if damage tolerance based special inspections are
necessary.
The Team evaluated the proposed Aging Airplane Safety Rule and determined that it is
not as specific as the SSID/SID AD’s in its requirement to accomplish a damage
tolerance assessment and determination of supplemental inspections. The rule does
not involve the ACO engineers in the review and approval of damage tolerance based
inspection programs. The proposed operating rule states that the operators must have
a maintenance program that includes damage tolerance based inspections and
procedures. The airplane operators have the freedom to submit a damage tolerance
based maintenance program to their Principal Maintenance Inspector, with no
requirement for the cognizant ACO’s review and approval of the damage tolerance
assessment, inspection method, and interval. In addition, the Safety Rule is not
applicable to Part 125 operators, which are cargo operators. The cargo operations fleet
typically consists of older airplanes with a large number of these airplanes having
undergone passenger to freighter modifications. These freighters often incorporate
several significant modifications, which may include auxiliary fuel tanks, zero fuel weight
increases, engine hush kits, and winglets. The Team also evaluated whether the
SSID/SID AD’s will conflict with the proposed Aging Airplane Safety Rule. The Team
determined that the requirements of the AD’s will not be in conflict with the Safety Rule,
but will actually provide the operators with a method to comply with the rule.
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30. 1. Aging Airplane Maintenance Program Developments
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The Team recommends the development of criteria for the determination of what
repaired, altered or modified structure requires damage tolerance based special
inspections. The criteria, similar to the example provide below, should be jointly
developed and adopted by all the cognizant ACO’s:
A damage tolerance assessment must be accomplished for all repaired, altered or
modified structure if all of the following criteria have been met:
1. The structure contributes significantly to the carrying of flight, ground or
pressurization loads.
2. The integrity of the structure is essential in maintaining the overall integrity of the
airplane.
Recommendation 4: Standardize the compliance time to perform a damage
tolerance assessment for repairs and non-STC design changes accomplished
before the effective date of the AD's as follows:
a) For airplanes that have already exceeded their SSID threshold the
compliance time should be 18 months after the effective date of the AD.
b) For airplanes that have not reached their SSID threshold, the compliance
time should be 18 months after the SSID threshold, or within 5 years after
the effective date of the AD, whichever occurs first.
The compliance time specified in paragraph (e) of the 727/737 AD for revision of the
FAA approved maintenance or inspection program for repairs and non-STC design
changes accomplished prior to the effective date of the AD, is 12 months after the first
SSID inspection. The 727/737 AD’s address both SSI’s created and affected by the
repair or design change. In contrast, the compliance time specified in paragraph (c) of
the MD-80 draft NPRM for revision of the FAA approved maintenance or inspection
program for repairs and modifications (including STC’s) accomplished prior to the
effective date of the AD, is 5 years after the effective date of the AD. The MD-80 draft
NPRM addresses PSE’s affected but not PSE’s created by the repair or design change.
From the Team’s interviews with an airline operator, it was apparent that paragraph (e)
was the only section of the 727/737 AD’s they found acceptable. They indicated that
other 727/737 operators shared this position. Paragraph (e) allows the operators to
assess the “old repairs” and “old design changes” at the next SSID inspection and then
allows 12 months after the inspection to determine if a new inspection method or
inspection interval is required.
During interviews, LAACO engineers voiced concern about inconsistencies in the
compliance time of paragraph (e) of the 727/737 AD’s. Their concern is that design
changes and repairs installed before the effective date of the AD are not addressed until
12 months after the first SSID inspection, which could be many years in the future. This
is in contrast to the requirement that design changes and repairs installed after the
effective date of the AD be addressed within 12 months after installation. They state
that because of this inconsistency, the 727/737 AD’s imply that new repairs and design
changes are less fatigue resistant than old repairs and design changes which could be
up to 20 years old.
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The Team believes there is merit to both the 727/737 operator’s and LAACO concerns
about the compliance time for repairs and design changes accomplished prior to the
effective dates of the AD’s. The Team recognizes that the 727/737 operators do not
know about all the repairs installed on their airplanes, and some operators may not
have sufficient data on the repairs and design changes in their fleets. Because of this,
the operators need sufficient time to identify and address these repairs and design
changes.
LAACO engineers indicated that there should not be the same concern regarding lack
of operator knowledge of repairs affecting the PSE’s. This is because repairs
andmodifications that affect PSE’s, the entire PSE must be inspected prior to the
threshold or have an AMOC. Additionally, Boeing South engineers indicated that if an
operator finds that they cannot accomplish a SID inspection due to the existence of a
repair or modification, that discrepant PSE must still be inspected prior to the SID
defined threshold, unless a new threshold is approved by the LAACO. However, FAA
Legal Counsel expressed concern during the Team’s interview, that operators of MDC
airplanes may not be ensuring that damage tolerance assessment and any changes to
the PSE inspections are being accomplished on 100% of PSE repairs. Legal Counsel
referred to comments from the airline operators represented at the Joint Management
Team meetings, as stating they don’t treat SRM repairs as “major” and have no
procedure for tracking or informing their engineering organizations when SRM repairs
are installed. Based on these comments, Legal Counsel questioned the validity of
assuming 100% reporting of repairs on the MDC fleet.
Based on all these comments and concerns, the Team recommends a standardized
compliance time for the 727/737 and MD-80 fleets that have exceeded the SSID
threshold. The MDC operators should not be affected since they should already be in
compliance, and the 18 month compliance time will then allow time for the 727/737
operators to comply. If there happens to be some MDC operators that are not currently
in compliance with reporting all their repairs and modification to PSE’s, the standardized
compliance time will provide sufficient time for them to comply as well. The Team also
recognizes that repairs and modifications on relatively young airplanes should not be
ignored until the first SSID inspection, and that a compliance time similar to the MD-80
draft NPRM would be appropriate.
Therefore, the Team recommends a combination compliance time broken into two
categories. For airplanes that have already exceeded their SSID threshold, the
compliance time should be 18 months after the effective date of the AD. For airplanes
that have not reached the SSID threshold, the compliance time should be 18 months
after the SSID/SID threshold, or within 5 years after the effective date of the AD,
whichever should occur first. This proposed two-category compliance time would
provide the operators adequate time to assess the repairs and design changes on the
airplanes if they have either exceeded or are approaching the SSID threshold. It also
provides up to 5 years to make the assessment if their airplanes are still young.
The Team chose to use the SSID/SID threshold as the benchmark for the compliance
time rather than the first SSID inspections, as was previously used in the 727/737AD's.
By using the inspection threshold, operators who may have accomplished the first
SSID/SID inspection significantly before the SSID threshold will not be penalized.
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32. 1. Aging Airplane Maintenance Program Developments
Addendum 1-2 FAA Report
Additionally, since the two-categories are divided based on whether the inspection
threshold has passed, a benchmark of inspection threshold is necessary to avoid
confusion regarding compliance times.
Recommendation 5: Provide a description in the AD’s detailing the information to
be included in the operators FAA-approved maintenance or inspection program.
The MD-80 draft NPRM does not provide a description of the information that should be
included in the operators FAA-approved maintenance or inspection program. In
contrast, Paragraph (d)(2)(iii) of the 727/737 AD’s provides instruction to “revise the
FAA-approved maintenance or inspection program to include an inspection method for
each new or affected SSI, and to include the compliance times for initial and repetitive
accomplishment of each inspection. The inspection methods and the compliance times
shall be approved by the Manager, Seattle ACO.” The Team recognizes from
interviews with the Seattle AEG and operators that information clarifying the FAA’s
expectations for AD compliance will reduce miscommunication. The Team
recommends the SSID/SID AD’s provide compliance information similar to what is
shown in Paragraph (d)(2)(iii) of the 727/737 SSID AD to clarify the AD requirements.
Recommendation 6: Standardize the acceptance of the Repair Assessment
Guidelines (RAG), where applicable, as a method of compliance to
recommendation 1 and 4 requirement for a damage tolerance assessment of
repairs. The RAG should only be applicable for those repairs found on the
fuselage pressure vessel.
Note 6 of the MD-80 draft NPRM accepts the Aging Aircraft Repair Assessment
Guidelines (RAG) as an acceptable method of compliance for the draft NRPM.
Currently, the 727/737 AD’s do not recognize the RAG’s as an acceptable method of
compliance to the AD’s. The Repair Assessment Program is mandated by Part 91.410,
121.370, 125.248 and 129.32 operating rules, with the RAG’s being approved as an
acceptable method of complying with the damage tolerance assessment and inspection
requirements of the rules. Because the RAG’s are approved by the cognizant ACO’s
and contain damage tolerance based inspections for certain repairs, they should be
accepted as a method of compliance for those repairs found on the fuselage pressure
vessel.
Recommendation 7:
a) Standardize the compliance time to perform a damage tolerance
assessment for STC’s accomplished before the effective date of the AD’s
similar to paragraph (d)(2) of the 727/737 AD’s, and remove paragraph (d)(1)
from the 727/737 AD’s.
b) Include a note similar to Note 7 in the 727/737 AD’s, which provide FAA
expectations for the contents of the compliance plan specified in
paragraph (d)(2).
The compliance time specified in paragraph (d) of the 727/737 AD’s provides the option
of two compliance times. This paragraph addresses SSI’s affected by STC’s
accomplished prior to the effective date of the AD. Paragraph (d)(1) requires that a
damage tolerance assessment and new inspections be determined within 18 months of
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