01-general aging airplanes

7/29/2019 01-GENERAL Aging Airplanes

1/129

May 04 1

Aging Airplane Safety Rule


2/129

May 04 2

BackgroundBackground

The Interim Final Rule and ACs published in Dec 02 are theresult of The Aging Airplane Safety Act of 1991

The current form of the rule resulted from comments received

from two previous NPRM publications. The latest was Apr 99

The FAA, having significantly modified the 1999 version, haspublished an interim final rule and requested further

comments

This is NOT an Aviation Rulemaking Advisory Committee/Airworthiness Assurance Working Group (ARAC/AAWG)

activity


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May 04 3

Who Is Affected?Who Is Affected?

This is an operational rule affecting operators that hold

certificates under 121, 129, and 135 In general, the rule has applicability to all Boeing

airplanes of US Registry operated under the applicablesections

Foreign Regulatory Authorities may or may not choose toenforce the rule on their operators

Leased airplanes, not currently registered in the US, mayalso be affected


4/129May 04 4

Two Rule Requirements:Two Rule Requirements:

Records Review

121.368

Supplemental Inspections

121.370a


5/129May 04 5

Records ReviewRecords Review

On 8 Dec 03, for airplanes

Exceeding 24 years in service: 1st records review mustoccur before 5 Dec 07

Exceeding 14 years in service, but less than 24 years: 1strecords review must occur before 4 Dec 08

Less than 14 years in service: 1st records review mustoccur no later than 5 years after the start of 15th year inservice

For all airplanes, records review will be repeated every 7 yrs

Physical inspection of the airplane will be by FAA

Administrator or Designee


6/129May 04 6

Significant Operator ConcernsSignificant Operator Concerns

! Seven-year repeat intervals are a concern

! Amount and kind of data requested may not exist

! Ability of the FAA to support review

In order to identify any process problems (schedules,access requirements, paperwork, training, ), AirTransport Association (ATA) sponsored prototyping ofsome airplane models by some volunteer operators

The amount of data required was significant

Many requests to Boeing to substantiate repairs

FAA participated


7/129May 04 7

Records Review

Current Status

Records Review

Current Status

Late last year the FAA provided training material to operatorsand PMIs on how the records review should be performed

Training allowed many of the concessions requested inthe ATA comments to the rule

Training provided no guidance for supplementalinspections

The rule is now effective and there are immediate record

review compliance requirements for certain older airplanesin order to complete first inspection of older airplanes by Dec07

FAA has yet to fully respond to the comments submitted tothe interim final rule


8/129May 04 8

Supplemental InspectionsSupplemental Inspections

Damage tolerance basedinspections and proceduresmust be in place by 5 Dec 07

Includes baseline structureand any Repairs, Alterationsand Modifications (RAMs) toprimary structure

Referenced as one of the datarecords to be reviewedfollowing rule compliancedate

This requirement represents apotentially significantincrease in the data required

to hold an operatingcertificate


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May 04 9

AAWG Proposal for SupplementalInspections

AAWG Proposal for SupplementalInspections

Requested that the rule be delayed 3 years to providesufficient time to develop guidance material for Damage

Tolerance Based inspections and procedures for all primarystructure, and:

Task the AAWG to develop the required guidance material

Assure SRMs are up to date

Allow the Structure Task Groups (STG)to validate that significant structuralservice bulletins are properlydocumented for DTA

Investigate the feasibility ofdeveloping model specific repairassessment guidelines for all primarystructure

Involve STGs in the implementation ofthe compliance plan


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May 04 10


Current Status


Current Status

FAA is aware of issues with the rule and of potential

overlap with the WFD rule

FAA has circulated a draft of an ARAC tasking:

Indicates that the FAA will allow the deadline for

supplemental inspections to slip

Provides the AAWG with a tasking to developguidance material and investigate best means for

industry to show compliance Tasking expected June 2004


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May 04 11

SummarySummary

Records Review

Compliance date is December 5, 2007

Significant concessions have been granted in showingcompliance through instructions to the PMIs


FAA is expected to task ARAC to determine best meansof compliance

FAA is further expected to delay the rule compliancedate until that means of compliance has been developed

Boeing will continue to advise operators of the status of

these two parts as new data becomes available


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May 04 12

BackupBackup


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May 04 13

Data to be Reviewed:Data to be Reviewed:

g. Current inspection status ofthe airplane, including thetime since the last inspectionrequired by the inspection

program under which theairplane is maintainedh. Current status of the

following, including themethod of compliance:

I. Airworthiness directives

II. Corrosion Prevention andControl Programs

III. Inspections andprocedures required by 121.370a (et al.) of thispart

i. A list of major structuralalterations

j. A report of major structuralrepairs and the currentinspection status for those

repairs

a. Total years in service

b. Total flight hours

c. Total flight cycles

d. Date of the last inspection andrecords review required by thissection

e. Current status of life-limitedparts of the airframe

f. Time since the last overhaul of

all structural componentsrequired to be overhauled on aspecific time basis


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8-1

REPAIR ASSESSMENT

WORKSHOP

Example of Applying the

Repair Assessment Guidelines

DetermineDetermine

Repairs toRepairs to

AssessAssess ExamineExamine

& Classify& Classify

RepairsRepairsDetermineDetermine

InspectionInspection

RequirementsRequirements


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8-2

Contents

Applying the Repair Assessment Guidelines to an Airplane

! Implement Program

" Implementation threshold

" Stage 1 - Determine repairs to assess

! Assess Repairs

" Assessment threshold

" Stage 2 - Examine repairs

"

Stage 2 - Classify repairs" Stage 3 - Determine inspection requirements

" Inspection threshold

! Inspect Repairs


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8-3

Implement Program

! Plan for assessing repairs must be in place at later of:

" On or before airplane reaches 60,000 flights

" May 25, 2001 if over 60,000 flights

! Plan should include:

" When repairs will be assessed

" How required inspections will be added to the

maintenance plan

Example Air will implement the program on their 737-200


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8-4

on May 25, 2000

Determine Implementation Threshold

Plan must be in place at or before 60,000 flights

737-

200


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8-5

Determine Repairs to Assess - Stage 1

Use document chart to define specific areas and repair types

! Typical fuselage skin (including upper and lower deck cargo door skins)

All external repair doublers greater than 12 inches in the longitudinal or circumferential directions.

All external repair doublers greater than 6 inches in the longitudinal or circumferential

directions, where the fuselage skin is hidden internally at the critical row of fasteners.

All external repair doublers within 3 inches of any other external repair doubler.

! Aft pressure dome (BS 1016):

!All repair doublers greater than 12 inches in the circumferential or radial direction or extending into

two or more bays.

1

! Door cutout area

All external repairs at or within 10 inches of a door cutout.

(Upper deck cargo door cutout area: no SRM or SB repairs, contact Boeing for evaluation of repairs

in this area.)

Fuselage Pressurized Skin" Areas where supplemental inspection may be required by this program:

! Pressurized radiused skin between BS 178 and 1016:

All internal (flush) repair doublers greater than 17 inches in length.


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8-6

Determine Assessment Threshold

! The assessment threshold is:

" The first major check (D-check) after 60,000 flights,

" Not to exceed 79,000 flights

! On or before this threshold, gather data for the repairs on

the airplane

For Example Airs 737


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8-7

737-

200

on date of D-check

Determine When to Examine Repairs

Example Air will gather data for repair assessment at this

D-check


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8-8

Repair #1Repair #1

Repair #2Repair #2

Repair #3Repair #3 Repair #4Repair #4

Examine Repairs on Airplane - Stage 2

At D-check, Example Air gathers data for repairs

! Start with Repair #1

! Assume repair installation dates are not known


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8-9

Examine Repair #1

Examine and record repair design features and condition

A

A

Section A-A

9

171.0 (typ.)

0.5(typ.)

tdblr= 0.0502024-T3

tskin = 0.0362024-T3

3/16 rivets,

protruding head,non-magnetic

Repair is in ideal condition, no deterioration

S-20L

S-21L

BS 380


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8-10

Record Data for Repair #1

Model type:

A/C I.D.: Completed by:

Date:Total No. of aircraft flight cycles :

Operator repair ref. No.

2. Geometric location: (Body Buttock Line, Body Station and stringer number, indicating right or

left. Also, indicate if repair is within 10 inches of a door cutout.)

1. Attach sketch, photograph, rubbing or drawing of repair. Indicate orientation with respect

to airplane structure: forward, up, outboard, etc. (optional)

Operator:

(of questionnaire completion)

(optional)

(optional)

REPAIR QUESTIONNAIRE

3. Component(s) identification:Structural element(s): (fuselage skin, pressure web)

Description of surface upon which repair is installed:

Example Air 737-200 Repair #1

62,464R. Elliott

See attached sketch

Between BS 380 and BS 400, from stringer S-20L to S-21L.

Fuselage skin

External doubler on basic skin in waffle doubler area.

N000XXSept. 12, 2000


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8-11

Record Data for Repair #1 (cont.)

5. Repair condition:

a) Evidence of deterioration: cracking or corrosion, loose, deformed, or missing parts or

fasteners, wrinkling, dents, open holes, or other damage. Circle which applies or specify.

b) General quality of repair installation: gouges, nicks, improperly driven rivets, sheared

fastener heads, or other damage. Circle which applies or specify and indicate depth of

damage if possible.

4. Repair dimensions (give orientation or include data on sketch)

height (width): diameter/other:

length:

c) Is repair structurally satisfactory considering 5a and 5b above?

(See the questionnaire explanation, item 5c, for further information.)

Yes No

Good condition. No deterioration noted.

17 inches

9 inches

None

X


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8-12


6. Proximity to adjacent repairs or STC modifications:

b) Are there any repairs located on the same or adjacent components? (i.e., within one stringer

bay, longeron bay, rib bay, or frame bay of this repair) ____ Yes ____ No: Go to item 7.

c) What is the distance, edge to edge, between each repair? Describe and give repairreference number. (show on sketch if more than one)

d) If adjacent repairs are butted up or overlapping, are they repairing

the continuation of original damage (crack or corrosion)? ____ Yes ____ No ____ Unknown

e) What are the equivalent dimensions of the repairs? Le

a) Is the repair in an area where loads, environment, or configuration are affected by anSTC modification? ____ Yes: Do not continue. See attached explanation. ____ No

REPAIR QUESTIONNAIRE -- continued

He

X

X


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8-13


g) Repair thickness*: (within +/- one standard gage at each layer if multiple layers exist

and/or at fastener locations if tapers exist)

7. Repair design: (show information on attached sketch, photograph, etc., if necessary)

a) Fastener type(s): (rivet, bolt; countersunk, solid, blind, etc. Specify if types are mixed.)

b) Fastener material (optional): _____ magnetic ______ non-magnetic

d) Average fastener spacing(s): (center to center +/- 1/8")

e) Repair material(s)*: (Aluminum, mag. or non-mag. steel, etc.)

f) Base skin thickness at the critical fastener row (optional at airplane)

c) Fastener diameter(s): (+/- 1/16")

h) Which joint details (Figure A-5) best represent the the critical rows of the repair:

(Write detail number below, sketch out, or describe in comments section)

lower row joint upper row joint

forward row joint aft row joint

Protruding head rivets

X

3/16 inch

1.0 inch

Aluminum

0.036 inch

0.050 inch

detail 1detail 1

detail 1detail 1


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8-14

Choose Joint Details

Joint details are shown in Figure A-5

ttskin

Ext. Int.

Detail 1(at typical skin)

Detail 2(at typical skin)

ttskin

Ext. Int.

Detail 3(at lap splice)

ttskin

Ext. Int.


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8-15


0.5 inch

X

j) What is the minimum visible fastener edge margin or edge distance (and fastener sizes

if more than one size was used):

in original structure:** in repair:k) Is the skin, doubler, or bearstrap visible from the inside at all the

critical (perimeter) fastener rows?If no, which rows are hidden and by what type of structure?

Yes No Unknown

8. Additional comments:

i) Does there appear to be more than one row of fasteners beyond cutout? __Yes __No __Unk

If yes, estimate number of rows beyond damage (in both directions): 3 rows

X

none


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8-16

Inspection and Replacement/Rework Requirements

Replace / rework

threshold

All

Time-limited inaccordance withSRM, repairdrawing, SB, etc.

No blindfasteners

Not applicable

24,000 flights afterrepair installation

Inspect and replace in accordance with applicable

SRM, repair drawing, SB, etc., instructions.

Value from the figures inSection 2.3.1

Containing blindfastenersthat canbe replacedwith solidfasteners

3,000

(flights after repair

installation)

Visual inspection of fasteners

every 3,000 flights for

looseness

Replace blind fasteners

with solid fastener repair

in accordance with SRM

within 10,000 flights from

repair installation.

Repair type

Value from the figuresin Section 2.3.1

Inspection interval

8,000(flights after repair

installation)

Category C

Repaircategory

Category B

Inspectionthreshold

60,000(airframe flights)


Inspection

interval1 2

3

22

Use The Inspection Threshold Chart

Threshold is shown in Fig. 2-7 chart

RepairRepaircategorycategory

Category BCategory B

InspectionInspectionthresholdthreshold

60,00060,000(airframe flights)(airframe flights)


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8-17

Determine Inspection Threshold

Most repairs will be either Category A or B

!For most existing Category B repairs:" Threshold is 60,000 flight cycles, or

" If over 60,000, threshold is data gathering plus 4,000

! Thus for the example airplane, the threshold is 66,464flight cycles

" Actual inspections should occur at a maintenance

interval on or before this threshold" Some repairs may have later thresholds, but plan

should consider earliest threshold


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8-18

on date of next C-check

Determine When to Classify Repairs

Determine repair categories and required inspections before

airplane reaches C-check

737-200


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8-19

Summary of Thresholds

For Example Airs 737:

Gather data

for repairs

Inspect

repairs

Classify repairs and

determine inspections

Airplane ondate of rule

52,40052,400 60,000*

Incorporate

assessment plan

62,46462,464****

Airplane atD-check

65,10065,100

Airplane atC-check

66,464***

* Implementation threshold** Assessment threshold

*** Inspection threshold


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8-20

Classify Repairs - Stage 2

Before C-check at 65,100 flights, determine:

!Category of the repair

! Inspection requirements

" Method

" Interval


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8-21

Classify Repair #1

X

X

X

X

X

X

X

X

If any box is marked yes,

the repair may not be

structurally satisfactory.

Further investigation is

required by the operator.

(You may contact Boeing

for assistance.)

If all boxes are marked no,

continue classification.

Question ClassificationYes No

Repair Condition and Structural Strength Design

Are there unapproved fasteners or loose, deformed, ormissing parts or fasteners? (Circle which applies.)

Are there signs of cracking?

Are there signs of wrinkling, dents, gouges, nicks, or unfilled

holes outside of SRM allowable operating limits? (Circle

which applies.)

If the repair is aluminum, is the thickness less than the baseskin thickness at the damaged area?

Does the repair have less than two rows of fasteners beyond

the damage area?

Is the average fastener spacing less than 2.5 fastener

diameters?For a two-row repair doubler, is it above stringer 14 and

between BS 178 and 1016? (If repair doubler is less than or

equal to 6 inches in length and width, skip this question.)

For a two-row repair doubler below stringer 14 and between

BS 178 and 1016, is the average fastener spacing greaterthan 7 fastener diameters or is the edge margin less than 1.5

fastener diameters?

1.

2.

3.

4.

5.

6.

7.

8.

1


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8-22

Classify Repair #1 (cont.)

X

Answer blind fastener question

If the box is marked yes,

the repair is Category C.

Are blind fasteners, that can be replaced by solid fasteners,

used in the repair? If the box is marked no,


Fastener Type

1.

Note: If the repair edge is within 10 inches of any door cutout,

skip this section and continue to the proximity section

(except for repairs on cargo door skins, where thissection should be completed).

Size/Location The following 5 questions can't be used if

maintenance intervals exceed the Baseline Zonal

Inspections by more than 10% (Figure 2-2).

2

3


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8-23


the repair is Category A.Document the results; no

need to continue

classification.

Can the perimeter fastener rows be visually inspected from the

inside and is the base skin thickness equal to or greater than0.056 inches?

Is the length and width of the repair doubler less than or equal

to 6 inches with no other repair within 3 inches?

Is the length and width of the repair doubler less than or equal

to 12 inches and can the perimeter fastener rows be visually

inspected from the inside and is there no other repair doubler

installed within 3 inches in either direction?

Is the length of the repair doubler, in the longitudinal direction,

less than or equal to 12 inches and is the repair doubler

located below stringer 10 and can the perimeter fastener rows

be visually inspected from the inside and is there no other

repair doubler installed within 3 inches in the longitudinaldirection?

If all boxes are marked no

or the answer is unknown,


2.

3.

4.

5.

Is the repair flush (internal) and is the length of the repair

doubler less than or equal to 17 inches?

1.

Classify Repair #1 (cont.)

Answer repair size and location questions

X

X

X

X

X


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8-24

Repair #1 is Category B

Answer repair durability questions and determine category

Repair Durability Design

For a three-row repair doubler, is the average fastener

spacing less than 3 or greater than 8 fastener diameters?

Proximity to Other Repair Doublers

Are aluminum repair doublers greater than three times thethickness of the base skin at the critical row of fasteners (or

are steel doublers greater than two times the thickness of the

base skin)?

Category :

If adjacent repairs are butted up or overlapping, are theyrepairing the continuation of original damage (crack or

corrosion)?


the repair is Category C.If the answer is unknown,

the repair is

Category C unless

further investigation

indicates it isCategory B.

If all boxes are marked no

or NA, the repair is

Category B.

Continue to Stage 3 and

summary worksheet.For a repair below stringer 14, are there less than three rows

of fasteners in the longitudinal or circumferential directions

from the cutout edge? (If cutout diameter is less than or equal

to 1 inch, write NA.)

1.

2.

3.

2

For a flush (internal) repair, are there countersunk fastenersinstalled in 0.036 or 0.040 inch skin?

4.

NA

X

X

X

BX


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8-25

Determine Inspection Intervals

Figure 2-7 chart lists where to find the intervals

! Refer to the charts in the document for inspection options

Inspection and Replacement/Rework Requirements

All

Category C

Repair typeInspectionthreshold


Time-limited inaccordance withSRM, repairdrawing, SB, etc.

No blindfasteners

24,000 flights afterrepair installation

Inspect and replace in accordance with applicable

SRM, repair drawing, SB, etc., instructions.


Containing blindfastenersthat canbe replacedwith solidfasteners

3,000

(flights after repair

installation)

Visual inspection of fasteners

every 3,000 flights for

looseness

Replace blind fasteners

with solid fastener repair

in accordance with SRM

within 10,000 flights from

repair installation.

8,000(flights after repair

installation)

Inspectionthreshold


Replace / rework

threshold

Not applicableValue from the figuresin Section 2.3.1

Inspection interval


Inspection

interval2

2

Repaircategory

Category B

Value from the figuresValue from the figuresin Section 2.3.1in Section 2.3.1

Inspection intervalInspection intervalRepairRepair

categorycategory

Category BCategory B


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8-26

Use Inspection Interval Chart

Figure 2-9 chart gives inspection interval options for this repair

Structural

element

Fuselage

skin

(except in

bilge area.

See Figure

2-10)

Repair doubler size (Le or He)(longest dimension), inches

Inter

val(flights)

5,000 (LFEC)4,500 (Det.)

25,000 (MFEC)

10,000

15,000

25,000

5,000

0

30,000

35,000

20,000

At stringers:

At butt joints:

At lap splice:

Betweenstringers:

Repair

737 SRM:

External skinrepair

53-30-3 (Fig. 1)53-30-3 (Fig. 17)

53-30-3 (Fig. 6)53-30-3 (Fig. 25)

53*30*3 (Fig. 28)

53-30-3 (Fig. 9)53-30-3 (Fig. 13)53-30-3 (Fig. 15)53-30-3 (Fig. 16)

SB:See Section 2.3.4for affectedservice bulletins

LFEC 2

MFEC 1

Visual

(Detailed)

3

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 and on

1

6

LFEC (external):

14,500 flights

for a 17 repair

LFEC (external):LFEC (external):

14,500 flights14,500 flights

for a 17 repairfor a 17 repair

1717


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8-27

Apply a Zone Factor

Effectivity

737-200

S-26L

Legend:

ZF = 1.0

4

5

Example Air

chose a repeat

interval of

14,500 flights

! Zone Factor

= 1.0 in thearea of the

repair

! Thus, the

required

interval =

14,500 x 1.0

= 14,500

flights

S-26R

BL-0

S-24R

S-19R

S-14R

S-10R

S-4R

BL-0

S-24L

S-19L

S-14L

S-10L

BL-0

S-4L

Top

STA360

STA540STA

259.50

Fwd

entry

door

Airstairs

Fwd

galley

door

Forward

cargodoor

RH

1

1

1

5

5

4

4

RepairRepair

#1#1


41/129

8-28

Determine Repeat Inspections

Using the external LFEC at 14,500 flight repeat intervals

(flights)

14,500

(interval)

62,46462,464

Data gathered

for repairs

First repair

inspection

65,10065,100

Second

inspection due

79,600

Repairs

classified

! First inspection must occur at or before the inspection

threshold" Inspect at C-check at 65,100 flights

! Second inspection will be due within the next 14,500 flights


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8-29

Record Assessment on Worksheet

Flights at time of repair: ________

Operator repair Ref. No.: ______

Date: _____________Completed by: _______________

Repair is covered by existing

mandated post-repair

inspection program per AD?

__ Yes: Covered by AD; no

further action required.

__ No: Continue to Stage 1

___ Yes :

___No :

Is repair to structure that may

require inspection per Section

2.1? (area/component

classification table)

Supplemental inspection may be required.

Go to Stage 2.

Existing inspection is adequate, no further action

is required.

STAGE 2Category from Stage 2 repair classification in Section 2.2: (check box)

Category A Category B

Continue to Stage 3 for

inspection requirements

Category C

(optional)

Current flights: ___________

AD No.: ______________Is repair to an STC modification

or to a component affected by

an STC modification?

__ Yes: Not covered by this

program

__ No: Continue to Stage 1

Airplane serial No.: ___________MODEL NO. ____________

Existing inspection is

adequate, no furtheraction is required.

Continue to Stage 3 for


STAGE 1

737-200 Example

#1

62,464

R. Elliott

unknown

X

X

X

X

Sep 12 00


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8-30

Record Assessment (cont.)

(For Category B and C repairs only)STAGE 3

Continue existing


(Inspection program perAD or Category A).

Zone Factor = 1

Inspection is

specified in the

SRM.Zone Factor = 1

Inspection requirements for repair

given in Section 2.3.1, Fig._______

1

Option 2 thru 4: Applyinspection guidelines

for thick repairs from

Section 2.3.2.

Option 1 : Replacerepair with Category

A or B repair that

may be more easily

inspected.

Inspection for repairs with thick doublers (Section 2.3.2):

Option 5: You maycontact Boeing for

inspection

requirements.

INSPECTION SUMMARY

Inspection

requirements

cannot be

determined. Boeing

may be contacted

for assistance.

Inspection details :

(Continue existing inspection if it is more restrictive than inspections

from this document)

Inspection threshold

Inspection interval (x zone factor)

Replacement/rework limit (Category C only)

2

3

3

Zone Factor = _________

X2-9

1.0

66,464 flights(inspect at 65,100-flight check)

14,500 flights using LFEC

not applicable


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8-31

Assess Remaining Repairs

Repeat the assessment for all repairs

A. Examine and recordA. Examine and record B. Determine categoryB. Determine category

Stage 2Stage 2

A. Determine thresholdA. Determine threshold B. Determine intervalB. Determine interval

Stage 3Stage 3


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8-32

Document a plan forDocument a plan for

accomplishingaccomplishingrequired inspectionsrequired inspections

Perform inspectionsPerform inspections

Add inspectionsAdd inspections

to scheduledto scheduled

maintenance planmaintenance plan

Add Inspections to Maintenance Plan


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8-33

Add inspectionsAdd inspections

to scheduledto scheduledmaintenance planmaintenance plan

New repairNew repair

AssessmentAssessment

needed?needed?

Continue existingContinue existing

maintenancemaintenance

Determine inspectionDetermine inspection

requirementsrequirements

Add New Repairs to Plan

For new repairs installed after initial repair assessment

No

Yes


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8-34

Summary

! Implement the Program

" Determine when to

have plan in place

" Determine when to

examine repairs

" Determine when to

begin inspecting

repairs

! Assess Repairs

" Determine which

repairs to assess

(Stage 1)

" Examine repairs(Stage 2)

" Classify repairs

(Stage 2)" Determine inspection

requirements

(Stage 3)

Applying the Repair Assessment Guidelines to an Airplane


48/129

Widespread

Fatigue DamageOctober, 2003

Agenda


49/129

October 2003 2

Agenda Why this is important

Background

WFD Program Overview Limit of Validity (LOV)

Maintenance Program Adjustments

! ISP

! SMP

737 Classic Model Specific Data

727 Classic Model Specific Data

Summary

Why Is This Important?


50/129

October 2003 3

Why Is This Important?

Will eventually affect all commercial

aircraft with a MGTOW > 75,000 pounds Will directly impact operators of aircraft

beyond DSO

Will probably impact residual value ofaircraft

Perception of change in Boeing traditionalposition on aging aircraft

Background


51/129

October 2003 4

Background

April 1988 Aloha Accident

June 1988 International Conference onAging Airplanes:

Industry committed to enact effective

programs to maintain structural integrity asairplanes age

Focused attention on gaps in the

airworthiness system Established AATF (now AAWG)

AAWG Efforts


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October 2003 5

AAWG Efforts

Developed five aging airplane initiatives:

Mandatory Modifications

CPCP

SSID

Repair Assessment Program (RAP)

Maintenance Programs

Committed to examine and produce aneffective program for the prevention ofWFD

Status Today


53/129

October 2003 6

Status Today

Five of the Aging Airplane Programs havebeen institutionalized for all commercial

air transports

New operational and certification rules for

the prevention of Widespread FatigueDamage are in the lengthy process ofbeing released

The Aging Programs


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October 2003 7

g g g

Mandatory Modifications:

Select Service Bulletins are reviewed fortermination of AD required special inspections inareas where a high likelihood of damage exists incombination with specific airworthiness concerns.

This program looks at the overall effect of aservice bulletin to the structural integrity of theairframe and then establishes a time for theincorporation of preventative modifications as

appropriate.

The Aging Programs


55/129

October 2003 8

g g g

Corrosion Prevention and Control (CPCP):

Develop and implement an industry-widemandated minimum corrosion prevention andcontrol program (CPCP) by model. This programwas established to develop baseline

maintenance programs for the prevention andcorrection of any corrosion before it becamesignificant.

The Aging Programs


56/129

October 2003 9

Structural Supplemental Inspection Program(SSID):

Assess the maintenance program for adequacyfor timely detection of accidental damage,environmental deterioration, and fatigue damage.Adjustments are made to the maintenanceprogram to include supplemental inspectionsbased on damage tolerance requirements at therequired locations.

The Aging Programs


57/129

October 2003 10

Maintenance Program Guidelines:

Develop an assessment procedure for airline

maintenance programs to determine programadequacy against known standards ofexcellence. An ATA document was preparedalong with model specific documents that helpand guide an airline that is involved inmaintaining older airplanes

The Aging Programs


58/129

October 2003 11

Repair Assessment Program (RAP):

Assess existing repairs to primary structure onolder (pre-amendment 45) airplanes based ondamage tolerance analysis. An intense AAWGreview found that repairs to the fuselagepressure boundary posed the greatest threat to

continued airworthiness. Therefore, thisprogram was developed to enable operators toassess all repairs to the fuselage pressureboundary and develop an appropriate

maintenance program to ensure the continuedairworthiness of that repair.

The Aging Programs


59/129

October 2003 12

Widespread Fatigue Damage (WFD):

Develop a program for the prevention of WFD in the

commercial fleet. This type of damage was anattributed cause of the 1988 Aloha accident. Thisprogram, still in development, will proactivelyidentify areas susceptible to WFD and establish

inspection and/or modification programs to mitigatethe risk.

What is WFD?


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October 2003 13

Widespread Fatigue Damage (WFD): ischaracterized by the simultaneous presence atmultiple structural details of numerous very smallcracks that are of sufficient size and densitywhereby the structure will no longer meet its

damage-tolerance requirement (i.e., maintain itsrequired residual strength after partial structuralfailure).

WFD Graphical Representation


61/129

October 2003 14

ISP

RES

IDUALSTRENG

TH

CRACKLENG

TH

REQUIRED

RESIDUAL

STRENGTH

WFD(Average Behavior)

SMP

MONITORING PERIOD

acrit WFD

adetThreshold and repeat interval

are determined so that thereis a high confidence that

WFD will not occur in the

fleet. All fatigue damage

found must be repaired.

MSD/MED

RESIDUALSTRENGTH

LWFD

IWFD IWFD IWFD IWFD

FLIGHT CYCLES

Reduction from averagebehavior to provide

equivalent protection to a

two lifetime fatigue test

"

Pr

obabilityD

ensity

Fun

ctio

n

Resid

ual

Strength

NOTE: No Scale Implied.

For Definition Use only

SPECIAL INSPECTIONS

OF MSD/MED

SUSCEPTIBLE AREAS

MSD/MED CRACK

GROWTH

*

*

"

NORMAL INSPECTION PROGRAMS

Sources of WFD


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October 2003 15

WFD may result from two sources:

Multiple Site Damage (MSD): a source ofwidespread fatigue damage characterized bythe simultaneous presence of fatigue cracks inthe same structural element (i.e., fatigue cracksthat may coalesce with or without other damage

leading to a loss of required residual strength). Multiple Element Damage (MED): a source of

widespread fatigue damage characterized by

the simultaneous presence of fatigue cracks insimilar adjacent structural elements.

Why Are We Concerned

About WFD?


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October 2003 16

About WFD?

WFD is an Airworthiness Concern.

MSD or MED is hard to reliably detect.

MSD/MED, when it is detected, generally meansthat a significant number of other airplanes in the

fleet could be affected immediately

An average of three new cases of MSD/MED haveoccurred every year from 1988 through 1999.

Some conditions found were well below minimumcertification requirements.

Where Might WFD Occur?


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October 2003 17

Susceptible Structure: Structure which has thepotential to develop MSD/MED. Such structuretypically is characterized by multiple similar detailsoperating at similar stresses where structuralcapability could be affected by interaction ofcracking at a number of similar details.

The following list, developed by the AAWG,contains structural details known to developMSD/MED

The list is neither comprehensive or all inclusive

Susceptible Structure


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October 2003 18

1) Longitudinal joints, frames and tear straps

2) Circumferential joints and stringers

3) Lap joints with milled, chem-milled or bondedradius

4) Fuselage frames

5) Stringer to frame attachment

6) Shear clip end fasteners on shear tied fuselageframes

7) Aft pressure dome outer ring and dome websplice

8) Skin splice at aft pressure bulkhead

Susceptible Structure


66/129

October 2003 19

9) Abrupt changes in web or skin thickness pressurized or unpressurized structure

10) Window surround structure11) Over wing fuselage attachments

12) Latches and hinges of non-plug doors

13) Skin at runout of large doublers

14) Wing or empennage chordwise splices

15) Rib to skin attachments

16) Typical wing and empennage construction

When Might WFD Occur?


67/129

October 2003 20

MSD and MED might occur anytimedepending on:

Design

Stress levels

Fatigue quality of the specific detail

Fatigue test provides the most reliable

means of prediction Analytical methods based on empirical

test evidence are also reliable

A New Paradigm for



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October 2003 21


Limit of Validity (LOV)

LOV is an airplane level number (usually expressedin cycles or hours) based on data from fatigue testevidence that predicts structural behavior

Within the LOV, all known or predicted MSD or MEDevents must be addressed by effective maintenanceactions including inspection, modification or both

An airplane may not be operated beyond LOVwithout the incorporation of a FAA approvedamendment to the maintenance program whichdefines a new LOV

Limit of Validity


69/129

October 2003 22

X

Sources of Fatigue Test Evidence


70/129

October 2003 23

LOV is based on a review of data from:

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 byother airplanes with similar design concepts

Analysis methods which have been parametricallydeveloped to reflect test and service experience

Maintenance Program Adjustments


71/129

October 2003 24

The establishment of an LOV also requiresthe modification of the maintenance programto ensure that any known or predicted

occurrence of MSD/MED is found andcorrected before the structural performancedegrades below acceptable levels

The AAWG established guidance for thedevelopment of maintenance programs forMSD/MED

The guidance is directed towards individualstructural details within the airplane and as

such is not associated with the LOV

Maintenance ProgramAdjustments


72/129

October 2003 25

The AAWG strongly recommended to the FAAthat for an effective program against WFD:

An active aging airplane maintenance programmust exist which includes: Mandatory Modifications

Corrosion Prevention and Control (CPCP) Repair Assessment (RAP)

Supplemental Structural Inspections (SSID)

All currently known structural airworthinessissues have been recognized and service actionsinitiated under existing safety processes

Maintenance ProgramAdjustments


73/129

October 2003 26

The AAWG Guidance material requires thedetermination of the following information foreach MSD or MED susceptible area:

Inspection Start Point (ISP): The point in time whenspecial inspections of the fleet are initiated due to aspecific probability of having a detectable MSD/MED

condition.

Structural Modification Point (SMP): A pointreduced from the WFD average behavior (i.e., lower

bound), so that operation up to that point providesequivalent protection to that of a two-lifetime fatiguetest. No airplane may be operated beyond the SMPwithout modification or part replacement.

ISP and SMP Graphical

Representation


74/129

October 2003 27

p

ISP

CRACKL

ENGTH

WFD

(Average Behavior)

SMP

acrit WFD

FLIGHT CYCLES

Reduction from average

behavior to provideequivalent protection to a

two lifetime fatigue test

NOTE: No Scale Implied.

For Definition Use only

SPECIAL INSPECTIONS

OF MSD/MED

SUSCEPTIBLE AREAS

MSD/MED CRACK

GROWTH

NORMAL INSPECTION PROGRAMS

Maintenance ProgramDevelopment


75/129

October 2003 28

p

For each susceptible detail:

Determine ISP and SMP

Compare results with Limit of Validity (LOV)

If less than LOV, initiate inspection and/ormodification program

If greater than or equal to LOV, no additionalaction necessary

Requires review if LOV is changed

WFD Maintenance ProgramAssessment of


76/129

October 2003 29

6

5

4

3

2

1

DSO LOV

ISP6

ISP5

ISP4

ISP3

ISP2

ISP1

SMP4

AreasSusce

ptibletoW

FD

Limit of fatiguetest evidence

SMP2

SMP1

Assessment of

Fatigue Test Evidence

Normal Maintenance


77/129

October 2003 30

737 Classic*

Model Specific Data

*737-100/200/300/400/500

737 ClassicDSO 75,000 Cycles


78/129

October 2003 31

Test/Teardowns

150,000 Flight Fatigue Test of FuselageD Box Section

129,000 Flight Fatigue Test of AftFuselage, removed from Service (59,000+ 70,000 cycles)

1987 Teardown Wing plus CenterSection, Forward Fuselage and

Empennage (59,000 cycles) 1988 Teardown of Aft Fuselage (129,000

cycles)

Panel tests conducted Cycled up to400,000 cycles

Ancillary Information

Designed FAR 25.571 AMDT 0, Fail Safe

Certain components fatigue tested SSID has been in place since 1983

Currently a threshold basedprogram with 132 airplanesinspecting (44% are N-

Registered) Threshold = 66,000 cycles

RAP begins at 60,000 cycles

Fleet demonstrated life = 116,100 Flight

Cycles

737 Classic LOV


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October 2003 32

If a WFD rule were in place today, the recommended LOV forthe 737 Classic fleet would be 100,000 cycles

Actions necessary to raise LOV: Acquire an airplane withapproximately 100,000 cycles, insure all mandatedmodifications are installed, conduct fatigue testing to at leasttwice the desired incremental change, and perform detailedteardown and analysis

Active and Inactive 737 AboveDSO


80/129

October 2003 33

0

5

10

15

20

25

74 -

76

76 -

78

78 -

80

80 -

82

82 -

84

84 -

86

86 -

88

88 -

90

90 -

92

92 -

94

94 -

96

96 -

98

Flight Cycles (1000)

Number

ofAirplanes

Inactive 737 L/N 1-291 Active 737 L/N 1-291

Inactive 737 L/N 292 and on Active 737 L/N 292 and on

737 Classic ISP and SMP


81/129

October 2003 34

1) Lap Splices Line # 1 291

Corrosion and fatigue concern

ISP = depends on age of airplane (see SB 737-53A1224)

SMP = depends on age of airplane (see SB 737-53A1224)

Line # 292 2565

ISP none: detectable is to close to critical

SMP = 50,000 cycles Lap modification in accordance with 737-53A1177

ISP = 45,000 after installation

SMP greater than LOV



82/129

October 2003 35

2) Circumferential joints ISP and SMP beyond LOV

3) Chem-mill steps

At crown skin lap splice area ISP = 42,000

SMP = 51,000

SB 737-53A1210 satisfies inspection requirements

SB 737-53A1177 modification removes this detail

At crown stringer locations

ISP beyond LOV



83/129

October 2003 36

4) Fuselage Frames

Section 43 and 46 critical configuration

ISP = 57,000

SMP beyond LOV

Modification per SB 737-53A1027 mandated

by AD 90-06-02 at 75,000 cycles removesthis detail

5) Stringer to frame connection (crown area)

ISP greater than LOV



84/129

October 2003 37

6) Shear clips end fasteners at shear tied fuselage frames

ISP greater than LOV

7) Aft pressure bulkhead outer ring and dome web splice

ISP = 80,000 cycles

SMP greater than LOV

Inspections per SB 737-53A1214 satisfyinspection requirements at ISP



85/129

October 2003 38

8) Skin splice at aft pressure bulkhead ISP greater than LOV

Continue with SSID inspections

9) Abrupt changes in web or skin thickness pressurized or unpressurized structure

No susceptible areas on the 737

10) Window surround structure ISP greater than LOV

11) Over wing fuselage attachments

Attachment not a WFD concern on the the 737



86/129

October 2003 39

12) Latches and hinges of non-plug doors

Lowest ISP greater than LOV

13) Skin at runout of large doublers

No susceptible areas on the 737

14) Wing or empennage chordwise splices

Lowest ISP greater than LOV15) Rib to skin attachments


16) Typical wing and empennage construction



87/129

October 2003 40

727 Classic

Model Specific Data

727 LOV AssessmentDSO 60,000 Cycles

LOV 100,000 Cycles

T t/T d A ill I f ti


88/129

October 2003 41

Test/Teardowns 60,000 Cycle Full Airframe Fatigue Test

(L/N 1-849)

170,000 Cycle Complete Fuselage (L/N 1-849)

1995 Teardown of Wing andEmpennage (46,700 Flight Cycles)

No significant fatigue findings 1999 - Teardown of Fuselage following

fatigue test (170,000 Cycles - 46,700flights plus 123,300 pressure cycles)

Some significant MSD/MED Findings

Ancillary Information

Designed CAR 4b.270, Fail Safe

Certain components fatigue tested

SSID has been in place since 1983

Currently a threshold based program with

240 airplanes inspecting (66% are N-

Registered)

Threshold = 55,000 cycles

727-200 Active Airplanes Above DSO

0

2

4

6

8

10

12

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

Flight Cycles (1000 )

NumberofAirplanes

727-200 Line # 1 - 849 727-200 Line # 850 and on

Fleet Demonstrated Life 106,700

Data as of11/2002

727 LOV Assessment

727 WFD A dit Fi di (ISPs or SMPs less than LOV)


89/129

October 2003 42

727 WFD Audit Findings (ISPs or SMPs less than LOV)

Lap splice lower row airplanes

L/N 850 and on

ISP 35,000 cycles SMP 55,000 cycles

SB 727-53A222 is applicable.

AD 99-04-22 addresses

inspections, superceding AD

2002-07-09 mandates

modification for airplanes >48,000 cycles

Stringer-to-crown skin (Test

Finding) ISP 61,000 cycles

SMP 101,000 cycles

SB to address inspections due

out 2nd

Qrt 2003 Boeing

expects AD

Fuselage frames (Test Finding) ISP 42,800 cycles

SMP 112,400 cycles

SB is in work to address immediate

concern Schedule TBD - Boeing

expects AD

Analytical results for Wing and

Empennage show no ISPs belowLOV

D t ti


90/129

October 2003 43

Documentation LOV will be contained in a new Airworthiness

Limitation Section of the MPD The ISP and SMP will be listed in a new D6 document

LOV(Estimated Values)

707 40 000 l


91/129

October 2003 44

707 40,000 cycles727 100,000 cycles

737 Classic 100,000 cycles

737 NG 1.5 DSO (112,500 cycles)

747 Classic 30,000 cycles/115,000 hours

747-400 35,000 cycles/165,000 hours757 1.5 DSO (75,000 cycles)

767 1.5 DSO (75,000 cycles)

777 1.5 DSO (60,000 cycles)

LOV(Estimated Values)


92/129

October 2003 45

MD-80 110,000 cycles

MD-90 110,000 cyclesDC-8 70,000 cycles

DC-10 60,000 Cycles / 150,000 hours

MD-11 TBD

Program Status


93/129

October 2003 46

Boeing is working with the FAA to validatemethodology and audit results

Boeing expects conditionally approveddocuments in first quarter of 2004

FAA is in the process or releasing theOperational Rule NPRM (ECD first quarter2004)

Scheduled maintenance checks

Maintenance Activities


94/129

October 2003 47

Fleet

damage

rate

CPCP inspections

SSID inspections

Repair assessments/inspections

Mandatory SB modification

and inspection programs

Fleet actions for WFD

Fleet

damage

DSO

Years of service

Start of detectable

fatigue damage

Environmental deterioration

and accidental damage

6

Airplane Maturity Factor


95/129

October 2003 48

0

1

2

3

4

5

Cumulative Cycles/Flight Hours

Aging

Effect

Traditional Maturing

Traditional maturing accounts for

increases in non-routine / routine

labor tasks. The Aging Effect includesthe additional tasks that must be

performed for continued safe operation

WFD

Effect


96/129

October 2003 49

Questions?


97/129

April 2004 1

Skin Cracking from Scribe Lines

Fleet ConcernFleet Concern


98/129

April 2004 2

Undetected skin cracks from scribe lines (scratches)in the lower skins at lap joints, and other areas, could

grow to be quite large and cause a suddendecompression

Since Feb 2003 Boeing has received reports of multiple



99/129

April 2004 3

Since Feb 2003, Boeing has received reports of multiplescribe marks in multiple locations on thirty-two 737 Classicsand four 747s

One 737-200 airplane had 5 inch crack in a lap joint and asecond airplane had two cracks (5 and 8 inches) inadjacent bays of a lap joint, all due to scribe marks

One 747-400 had a 30-inch crack at the BS 2180 butt jointand one 747-200 had a 30-inch crack at the BS 400 buttjoint, both due to improper sealant removal

Up

Typical Scribe Detail - 737 Lap Joint (LN 292-2565)

Upper Skin


100/129

April 2004 4

A-A

Typical

Scribe

Inbd

View From Outside

CenterLine

Frame

A

A

10

Typical

Scribe

Sealant

Lower

Skin

Upper

Bonded

Doubler

Scribe marks appear to be caused by



101/129

April 2004 5

pp ythe use of putty knives, razor blades,or other objects to remove sealant ortrim decals (even plastic scrapers can

damage the clad layer of fuselageskins)

Scribe marks are generally 0.001

(0.025 mm) to 0.005 (0.127 mm)deep, and many times do notpenetrate the clad layer (0.003)

Scribe marks typically run parallel (within 0.250 or 6.25mm) to the upper skin at lap joints and vertically in thesplice strap between skins at butt joints

Typical Scribe MarksTypical Scribe Marks


102/129

April 2004 6


103/129

April 2004 7


104/129

April 2004 8

Mapping of Visible Scribes onOne 737-200

Mapping of Visible Scribes onOne 737-200


105/129

April 2004 9

Suspect 737 Classic AirplanesSuspect 737 Classic Airplanes

Thirty-two 737 Classic airplanes are known to have scribes


106/129

April 2004 10

(out offorty-one inspected)

Twenty 737-200s Eight 737-300s Four 737-400s

6 operators in Europe, 4 in USA, 1 in Canada, 1 in SouthAmerica, 1 in Australia, and 1 in Africa

Scribing occurred at several facilities

Cracks found on two airplanes at 22,000 and 27,000 cycles

Based on airplanes repainted within a two-year window ofknown scribed airplanes, over one hundred 737 Classic airplanesare now suspect

737 Classic Fleet Data737 Classic Fleet Data

Active Airplanes:*


107/129

April 2004 11

p

100 200 300 400 500 Total

Group 1 176 562 216 245 1199

Group 2 3 730 540 265 141 1679

TOTAL: 3 906 1102 481 386 2878

*ACTS Data 4 Dec 03

Group 1 = Airplane still with original owner

Group 2 = Airplane has changed ownership at least once

Crack AssessmentCrack Assessment

Cracks initiated from scribe marks


108/129

April 2004 12

Approximately 22,000 to 24,000 cycles from scribe marking

to cracks growing through the thickness of the skin

Cracks initiate at multiple points along the length of eachscribe mark (Multi Site Damage - MSD)

Scribing across tear straps could potentially lead to verylong cracks (zipper effect)

Many variables affect crack initiation and growth (scatterfactor)

737 ClassicLap/Butt Joint Mechanics

737 ClassicLap/Butt Joint Mechanics


109/129

April 2004 13

Unloaded Lap Joint Loaded Lap Joint

4 KSI

Inner Fiber22 KSI

Outer Fiber

25 KSI

Inner Fiber

0 KSI

Outer Fiber

Scribe Cracks

Chem-mill Cracks

Upper SkinBonded

Doubler

Lower Skin

737 Classic Scribe Cracking Behavior737 Classic Scribe Cracking Behavior

Cracks initiate at multiple sites (many per inch) along the base


110/129

April 2004 14

Cracks initiate at multiple sites (many per inch) along the baseof the scribe

Multiple small cracks link up before they grow throughthickness creating a continuous long crack partially throughthe thickness

ScribeMultiple Crack Initiation Sites

Crack Fronts Link Up Partially Through Skin Thickness

Skin Thickness

737 Classic Cracking Scenarios737 Classic Cracking Scenarios

Local Scribe Damage


111/129

April 2004 15

Scribe inLower

Skin

LowerRow

Cracks

Scribe inLower

Skin

Scenario

1

2

Scribe InducedCracks

Scribe InducedCracks

Scribe/LowerRow

Interaction

Boeing Actions to DateBoeing Actions to Date

SRP 737-53-0214 initiated Apr 03

Initially viewed as isolated events


112/129

April 2004 16

y

All 737 Classic operator messages (May 5th, Jun 6th,and Sep 12th)

Awareness of issue

Review sealant removal procedures

Inspect crown laps at next convenient opportunity

FTEI posting (EM-003-0027)

FTD posting (737-FTD-53-03006)

Numerous 737 Classic Regional meetings and TechnicalReviews

Boeing Actions to Date(continued)

Boeing Actions to Date(continued)

Developed UT/NDT procedures to inspect for cracking at lap


113/129

April 2004 17

Developed UT/NDT procedures to inspect for cracking at lapjoints

Worked with operators and MROs to identify other suspectairplanes

Worked with operators and the FAA (and other regulatory

authorities) to temporarily return seven 737 Classic airplanesto service

Working to qualify better tools and procedures to removesealant

All 737 Classic Operator Message released 3 Feb 04

Key Points of MessageKey Points of Message

This is a potential airworthiness concern

The only way to know whether or not an airplane has scribe


114/129

April 2004 18

The only way to know whether or not an airplane has scribemark damage is to look

Suggested operator immediate actions:

Review sealant removal and decal applicationprocedures and tools

Review airplane records for suspect scribingopportunities

If >15,000 cycles since suspect scribing, accomplish

loose sealant inspections and repeat every 500 cycles(very similar to AD 2003-14-06)

Guidance on sealant removal

Scribe PreventionScribe Prevention

All 737 Classic Operator Meeting Seattle 3 March


115/129

April 2004 19

Regional meetings

London March 18-19

Bangkok March 22-23

Revise Boeing Manuals 2nd Qtr 04

Sealant removal process

Three Main Steps to ResolveSafety Issue

Three Main Steps to ResolveSafety Issue


116/129

April 2004 20

Identify Scribed Airplanes The Search

Limited Return To Service (LRTS) Plan

Repairs

Working GroupWorking Group

Air Transport Association (ATA) sponsored


117/129

April 2004 21

Integral part of the Lead Airline Process

Members: Boeing, the FAA (ACO and FSDO), ATA,and airlines:

US Airways

Continental

Delta

Southwest

- United

-

Lufthansa (LTK)- Qantas

The Search for Scribe MarksThe Search for Scribe Marks

Why?


118/129

April 2004 22

When?

Where?

How?

Vehicle

Inspection Method

Limited Return To ServiceLimited Return To Service

Accomplish repairs

at Stringer 20

Accomplish Internal

inspections5.15.8 5.9

Strip Sealant


119/129

April 2004 23

Perform Visual

inspection

NDT inspect for

cracks at scribed

locations

Provide NDT

findings to

Boeing

Accomplish repairs

at suspected

crack locations

at Stringer 20

Accomplish Internalinspection 1085

Accomplish Internal

inspection 1125

Accomplish Internal

inspection 1179

Limited ReturnTo Service plan

(LRTS)

Provide results

to Boeing for

approvalRecord the

damage

5.2

5.1

5.3

5.4

5.5

Accomplish Internal

inspection 1255

Accomplish Internal

inspection 1027

5.7

5.9A

5.10

5.6

5.9B

5.9C

5.9D

5.9E

5.9F

p

Send Damage

map to

Boeing

5.11

Accomplish Internal

inspection 1160

Accomplish Internal

inspection 11775.9G

Limited Return to Service Plan(Preliminary Not FAA Approved)

Limited Return to Service Plan(Preliminary Not FAA Approved)

Time Limit Until Repair(Cycles)

Repeat NDT Inspections(Cycles)

Cycles from SuspectScribing


120/129

April 2004 24

1,200 or 30K from scribing,whichever is first, and 6 psi

limitation

25025,000-30,000

Repair before further flightNot Applicable> 30,000

Prior to 19.5K from scribingVisual inspections @ 500cycles until 15K, thenNDT inspection every

250


121/129

April 2004 25

(or more) to complete

Work ongoing to reduce LRTS impact:

FAA Delegation to Boeing for approval in work

Skin Trim to expose scribes promising

Reduction in repeat NDT inspections possible

Interim repairs being tested for durability

RepairsRepairs

P id NDT4 1 6


122/129

April 2004 26

Perform Visualinspection

NDT inspect for

cracks at scribed

locations

Provide NDT

findings to

Boeing

Accomplish repairs

at Lap joints

Accomplish repairs

at Butt joints

Provide results

to Boeing for

approval

Record thedamage

Strip Sealant

Send Damage

map to

Boeing

Accomplish Repairs

Accomplish all

other required repairs

Accomplish repairs

at Wing to BodyFairings

4.1.8

4.1.7A

4.1.1

4.1.2

4.1.3

4.1.7B

4.1.7C

4.1.7D

4.1.4

4.1.5

4.1.6 4.1.7

Interim RepairsInterim Repairs

Lap Splice reinforcement concepts being tested


123/129

April 2004 27

p p p g

Butt Splice inspection techniques being developed

Analysis in work to justify Boeing position relative tostructure that does not require repair or continuedinspection is adequate

737 Scribe RepairLap Joints Internal Repairs

737 Scribe RepairLap Joints Internal Repairs

10

Up

0.036 Fillers


124/129

April 2004 28

A-A

A

AView From Outside

Inbd

B-B

B

B

Scribe

Fail-safe Doublers

0.032, 2024-T3 Clad Sht

0.032 Shim

Permanent RepairsPermanent Repairs

Lap Splice Mod is terminating action for stringers 4,10 and 14


125/129

April 2004 29

0 a d

Lower lobe lap repairs not currently documented

Butt splice repairs best achieved through removing andreplacing splice straps

Local repairs at wing-to-body fairing necessary

Analysis in work relative to structure that does not

require repair

Results of Working Group Meetings:Next Steps

Results of Working Group Meetings:Next Steps

Identify High Risk Criteria


126/129

April 2004 30

Identify High Risk Criteria

Total airplane cycles in excess of ~40K

Lap Splice Mod not incorporated

Other?

Develop and implement a Phased ImplementationPlan to minimize impact to operators

737 ClassicFleet Action Plan

737 ClassicFleet Action Plan


127/129

April 2004 31

Phase 3

Low RiskAirplanes

Phase 2Medium Risk

AirplanesPhase 1

High RiskAirplanes

QUESTIONS?


128/129

April 2004 32

QUESTIONS?


129/129

April 2004 33

01-general aging airplanes

Documents