Commercial 

Airplanes MD90

Service Bulletin

ALERT

Number: MD90-55A016

Original Issue: December 16, 2009

Revision 1: February 17, 2010

ATA System: 5511

SUBJECT: STABILIZERS - Section, Horizontal Stabilizer Center - Inspect/Repair/Replace Horizontal

Stabilizer Center Section Left and Right Rib Hinge Bearing Lugs

Export of this technology is controlled under the United States Export Administration Regulations (EAR) (15

CFR 730-774). An export license may be required before it is used for development, production or use by foreign

persons from specific countries. The controller of this data has the individual responsibility to abide by all export

laws.

ECCN: 9E991

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Copyright © 2009 The Boeing Company

Unpublished Work - All Rights Reserved

Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable

subject matter. Boeing also claims copyright in this document as a compilation and/or collective work.

This document includes proprietary information owned by The Boeing Company and/or one or more third parties.

Treatment of the document and the information it contains is governed by contract with Boeing. For more

information, contact The Boeing Company, P.O. Box 3707, Seattle, Washington 98124.

Boeing, the Boeing signature, the Boeing symbol, 707, 717, 727, 737, 747, 757, 767, 777, 787, Dreamliner,

BBJ, DC-8, DC-9, DC-10, KC-10, KDC-10, MD-10, MD-11, MD-80, MD-88, MD-90, P-8A, Poseidon and the

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3.0
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BLANK PAGE
Table of Contents

Revision Transmittal Sheet ............................................ 5

Summary ...................................................... 7

1. PLANNING INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

A. Effectivity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

1. Airplanes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2. Spares Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

B. Concurrent Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

C. Reason . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

D. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

E. Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

F. Approval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

G. Manpower . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

H. Weight and Balance Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

I. Electrical Load Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

J. References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1. Existing Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2. Data supplied with this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3. Installation Drawings Used in the Preparation of this Service Bulletin . . . . . . . . . . . . 17

K. Publications Affected . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

L. Interchangeability and Intermixability of Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2. MATERIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

A. Material - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

B. Industry Support Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

C. Parts Necessary For Each Airplane . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1. Kits/Parts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2. Parts and Materials Supplied by the Operator . . . . . . . . . . . . . . . . . . . . . . . . 20

3. Parts Modified and Reidentified . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

4. Parts Removed and Not Replaced . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

D. Parts Necessary to Change Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

E. Special Tooling - Price and Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

F. Special Tooling Necessary to do this Service Bulletin . . . . . . . . . . . . . . . . . . . . . . . 20

3. ACCOMPLISHMENT INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

A. GENERAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

B. WORK INSTRUCTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS . . . . . . . . . . . . . . 24

FIGURE 2: CRACK LENGTH MEASUREMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

FIGURE 3: BLEND OUT REPAIR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

FIGURE 4: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS . . . . . . . . . . . . . . 41

APPENDIX A: TEMPLATE/SHIELD SHOP AID . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

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BLANK PAGE
Commercial 

Airplanes MD90

Service Bulletin

ALERT

Revision Transmittal Sheet Number: MD90-55A016

Original Issue: December 16, 2009

Revision 1: February 17, 2010

ATA System: 5511

SUBJECT: STABILIZERS - Section, Horizontal Stabilizer Center - Inspect/Repair/Replace Horizontal

Stabilizer Center Section Left and Right Rib Hinge Bearing Lugs

This revision includes all pages of the service bulletin.

COMPLIANCE INFORMATION RELATED TO THIS REVISION

No more work is necessary on airplanes changed in accordance with the original issue of this service bulletin.

REASON FOR REVISION

This revision is sent to include inspection requirements for the hinge bearing lug on replaced horizontal stabilizer

center section ribs. Added Appendix to define a template/shield shop aid that may be used at operator's option

to more clearly define the blend out area on the hinge lug.

These sections were changed:

1. Changed Service Bulletin title to more clearly define work requirements.

2. In Paragraph 1.D., Description, added inspection requirement for the hinge bearing lug on replaced horizontal

stabilizer center section ribs.

3. In Paragraph 1.E., Compliance, added inspection requirements and intervals for the hinge bearing lug on

replaced horizontal stabilizer center section ribs.

4. In Paragraph 1.G., Manpower, changed note to include replacement of any center section rib.

5. In Paragraph 2.A., Material - Price and Availability, added parts required for center section rib replacement,

and ordering information.

6. In Paragraph 2.C.1., Parts Necessary For Each Airplane, added parts required for center section rib

replacement.

7. In Paragraph 3.B., Work Instructions, added inspection requirements for the hinge bearing lug on replaced

horizontal stabilizer center section ribs, and added note regarding availability of locally manufactured

template/shield shop aid.

8. In Figure 3, added recommended cutter information to work step 5.

9. Added Appendix A.

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Vertical lines are put on the left edge of each page, except in Paragraph 1.A., Effectivity, to show the location

of important changes.

Pages with no vertical lines have no important changes.

REVISION HISTORY

Original Issue: December 16, 2009

Revision 1: February 17, 2010

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Commercial 

Airplanes MD90

Service Bulletin

ALERT

Summary Number: MD90-55A016

Original Issue: December 16, 2009

Revision 1: February 17, 2010

ATA System: 5511

SUBJECT: STABILIZERS - Section, Horizontal Stabilizer Center - Inspect/Repair/Replace Horizontal

Stabilizer Center Section Left and Right Rib Hinge Bearing Lugs

THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH

1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OWNER.

CONCURRENT REQUIREMENTS

None.

BACKGROUND

Boeing has received seven reports of cracks being found on either the left, right, or in one case both, of the

MD-90 horizontal stabilizer center section ribs. These cracks were found on the aft face of the horizontal stabilizer

hinge bearing lugs. Cracks were reported on MD-90 airplanes with between 9051 and 21,183 flight-hours and

8939 and 20,893 flight cycles. Investigation by Boeing has yet to establish the definitive cause of these cracks.

Performing an Eddy Current, High Frequency inspection of the affected area will determine the existence of any

crack. If not corrected, undetected cracks in the center section left and right rib hinge bearing lugs could spread

at the same time which would cause both hinge bearing lugs to fail, resulting in the horizontal stabilizer being

unable to sustain the required loads.

ACTION

This service bulletin gives instructions to do an Eddy Current, High Frequency inspection of the horizontal

stabilizer center section left and right rib hinge bearing lugs for cracks and does as follows:

CONDITION 1 (No Crack Found in Rib Hinge Bearing Lug)

1. Repeats the Eddy Current, High Frequency inspection at defined intervals.

CONDITION 2 (Crack Found in Rib Hinge Bearing Lug)

1. Measures the crack length and do as follows:

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CONDITION 2A (Crack Length Between Points 'A' and 'B' is Less Than or Equal to 0.15 Inch, and

Crack Length Between Points 'C' and 'D' is Less Than or Equal to 0.05 Inch)

a. Does blend out repair to remove crack.

b. Repetitively inspects blend out area for cracks, using Eddy Current, High Frequency inspection.

CONDITION 2B (Crack Length Between Points 'A' and 'B' is Greater Than 0.15 Inch, or Crack Length

Between Points 'C' and 'D' is Greater Than 0.05 Inch)

a. Replaces horizontal stabilizer center section rib.

b. Does Eddy Current, High Frequency inspections at a defined threshold.

EFFECTIVITY

MD-90-30 Airplanes. Refer to Paragraph 1.A.1., Airplanes, for the list of affected airplanes.

COMPLIANCE

The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to this service

bulletin. The Airworthiness Directive will make the compliance tasks and times given in this service bulletin

mandatory.

Refer to Paragraph 1.E., Compliance.

INDUSTRY SUPPORT INFORMATION

Boeing warranty remedies are not available for the inspection given in this service bulletin.

MANPOWER

Refer to Paragraph 1.G., Manpower.

MATERIAL INFORMATION

Boeing Supplied Kits/Parts.

Refer to Paragraph 2.A., Material - Price and Availability.

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BLANK PAGE
Commercial 

Airplanes MD90

Service Bulletin

ALERT

Number: MD90-55A016

Original Issue: December 16, 2009

Revision 1: February 17, 2010

ATA System: 5511

SUBJECT: STABILIZERS - Section, Horizontal Stabilizer Center - Inspect/Repair/Replace Horizontal

Stabilizer Center Section Left and Right Rib Hinge Bearing Lugs

THIS BULLETIN IS SENT TO THE OPERATORS OF RECORD OF THE AIRPLANES SHOWN IN PARAGRAPH

1.A., EFFECTIVITY. IF AN AIRPLANE HAS BEEN LEASED OR SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OPERATOR. IF APPLICABLE SPARES HAVE BEEN SOLD, SEND THIS SERVICE BULLETIN TO

THE NEW OWNER.

1. PLANNING INFORMATION

A. Effectivity

1. Airplanes

This service bulletin is for the airplanes shown below.

GROUP CONFIGURATION DESCRIPTION

1 - MD-90-30 airplanes

Airplane Models:

MD-90-30

Fuselage Num- Group

ber

2018 1

2094 - 2100 1

2115 1

2117 1

2120 1

2122 - 2123 1

2125 - 2126 1

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Fuselage Num- Group

ber

2129 1

2131 1

2133 1

2136 1

2138 1

2140 - 2144 1

2146 - 2147 1

2149 - 2150 1

2153 - 2154 1

2156 - 2166 1

2168 - 2173 1

2175 1

2177 1

2179 1

2181 - 2182 1

2184 1

2186 1

2190 - 2191 1

2193 - 2195 1

2197 - 2198 1

2200 1

2202 - 2203 1

2205 1

2207 1

2209 - 2213 1

2215 - 2217 1

2219 - 2233 1

2235 - 2238 1

2240 1

2242 - 2243 1

2245 - 2246 1

2248 1

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Fuselage Num- Group

ber

2250 - 2251 1

2253 1

2255 - 2263 1

2288 - 2290 1

4001 - 4002 1

2. Spares Affected

None.

B. Concurrent Requirements

None.

C. Reason

Boeing has received seven reports of cracks being found on either the left, right, or in one case both,

of the MD-90 horizontal stabilizer center section ribs. These cracks were found on the aft face of the

horizontal stabilizer hinge bearing lugs. Cracks were reported on MD-90 airplanes with between 9051

and 21,183 flight-hours and 8939 and 20,893 flight cycles. Investigation by Boeing has yet to establish

the definitive cause of these cracks. Performing an Eddy Current, High Frequency inspection of the

affected area will determine the existence of any crack. If not corrected, undetected cracks in the left

and right ribs hinge bearing lugs could spread at the same time which would cause both hinge bearing

lugs to fail, resulting in the horizontal stabilizer being unable to sustain the required loads.

Revision 1 is sent to include inspection requirements for the hinge bearing lug on replaced horizontal

stabilizer center section ribs. Added Appendix to define a template/shield shop aid that may be used

at operator's option to more clearly define the blend out area on the hinge lug.

D. Description

This service bulletin gives instructions to do an Eddy Current, High Frequency inspection of the horizontal

stabilizer center section left and right rib hinge bearing lugs for cracks and does as follows:

CONDITION 1 (No Crack Found in Rib Hinge Bearing Lug)

1. Repeats the Eddy Current, High Frequency inspection at defined intervals.

CONDITION 2 (Crack Found in Rib Hinge Bearing Lug)

1. Measures the crack length and do as follows:

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CONDITION 2A (Crack Length Between Points 'A' and 'B' is Less Than or Equal to 0.15 Inch,

and Crack Length Between Points 'C' and 'D' is Less Than or Equal to 0.05 Inch)

a. Does blend out repair to remove crack.

b. Repetitively inspects blend out area for cracks, using Eddy Current, High Frequency inspection.

CONDITION 2B (Crack Length Between Points 'A' and 'B' is Greater Than 0.15 Inch, or Crack

Length Between Points 'C' and 'D' is Greater Than 0.05 Inch)

a. Replaces horizontal stabilizer center section rib.

b. Does Eddy Current, High Frequency inspections at a defined threshold.

Revision 1 - No more work is necessary on airplanes changed in accordance with the original issue of

this service bulletin.

The work in this service bulletin is done in the maintenance zone(s) given below.

Affected Maintenance Zones

Model Zone

MD-90-30 351, 361

E. Compliance

The Federal Aviation Administration (FAA) will possibly release an Airworthiness Directive related to

this service bulletin. The Airworthiness Directive will make the compliance tasks and times given in this

service bulletin mandatory.

Table 1 - Inspect Horizontal Stabilizer Center Section Left and Right Rib Hinge Lug for Cracks:

Repeat Interval

(Not to Exceed)

Condition Action Compliance Time

Before the accumulation of 7200 total

flight cycles, or

within 1505 flight

cycles after the

original issue date

on this service bulletin, whichever

occurs later.

Do an Eddy Current, High

Frequency inspection of

the aft face of the horizontal stabilizer center section left and right rib hinge

lugs in accordance with

Accomplishment Instructions, Paragraph 3.B.2.

All Airplanes

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BOEING SERVICE BULLETIN MD90-55A016

ALERT ALERT
Table 1 - Inspect Horizontal Stabilizer Center Section Left and Right Rib Hinge Lug for Cracks:

Repeat Interval

(Not to Exceed)

Condition Action Compliance Time

Within 1680 flight

cycles from last inspection.

Within 1680 flight

cycles from last inspection.

Do an Eddy Current, High

Frequency inspection of

the aft face of the uncracked horizontal stabilizer center section rib hinge

lugs in accordance with

Accomplishment Instructions, Paragraph 3.B.2.

CONDITION 1

(No Crack Found in Rib

Hinge Bearing Lug)

Before further

flight.

Measure crack length in

accordance with Accomplishment Instructions,

Paragraph 3.B.2.

CONDITION 2

(Crack Found In Rib Hinge

Bearing Lug)

Before further

flight.

Blend out crack in accordance with Accomplishment Instructions, Paragraph 3.B.2.

CONDITION 2A

(Crack Length Between

Points 'A' and 'B' is Less

Than or Equal to 0.15 Inch,

and Crack Length Between

Points 'C' and 'D' is Less

Than or Equal to 0.05

Inch.)

AND

Within 400 flight

cycles.

Within 1000 flight

cycles after blend

out.

Do an Eddy Current, High

Frequency inspection of

the blend out on the center section rib hinge

bearing lug in accordance

with Accomplishment Instructions, Paragraph

3.B.2.

Before further

flight.

Replace horizontal stabilizer center section rib.CONDITION 2B

(Crack Length Between

Points 'A' and 'B' is Greater

Than 0.15 Inch, OR Crack

Length Between Points 'C'

and 'D' is Greater Than

0.05 Inch.)

AND

Within 1680 flight

cycles from last inspection.

Before the accumulation of 7200 total

flight cycles after

the installation of

the new rib.

Do an Eddy Current, High

Frequency inspection of

the aft face of the replaced horizontal stabilizer center section rib hinge

lug in accordance with

Accomplishment Instructions, Paragraph 3.B.2.

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F. Approval

This service bulletin was examined by the Federal Aviation Administration (FAA). The changes specified

in this service bulletin comply with the applicable regulations and are FAA approved, as well as European

Aviation Safety Agency (EASA)/Joint Aviation Authorities (JAA) approved for all EASA/JAA approved

airplanes listed in the service bulletin effectivity. This service bulletin and its approval were based on

the airplane in its original Boeing delivery configuration or as modified by other approved Boeing

changes.

If an airplane has a non-Boeing modification or repair that affects a component or system also affected

by this service bulletin, the operator is responsible for obtaining appropriate regulatory agency approval

before incorporating this service bulletin.

G. Manpower

The table below shows an estimate of the task hours necessary to do this inspection for each airplane.

This estimate is for direct labor only, done by an experienced crew. Adjust the estimate with operator

task hour data if necessary. The estimate does not include lost time. These are some examples of lost

time:

• Time to adjust to the workplace

• Time to schedule the work

• Time to inspect the work

• Time to cure the materials

• Time to make the parts

• Time to find the tools.

Task Number of Persons Task Hours Elapsed Hours

Open Access 2 2.0 1.0

Inspect 1 2.0 2.0

Close Access 2 2.0 1.0

TOTAL FOR EACH AIRPLANE 6.0 4.0

NOTE: The Manpower totals listed do not include the hours required to accomplish any blend out

repair(s) or replacement of center section rib(s), if required. Operators are to estimate the task

hours required based on inspection results.

H. Weight and Balance Changes

None.

I. Electrical Load Data

Not changed.

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J. References

1. Existing Data

a. Non-Destructive Test Standard Practices Manual (NDTSPM) 06-10-01.001.

b. MD90 Aircraft Maintenance Manual (AMM) 06-33-00.

c. MD90 Structural Repair Manual (SRM) 51-10-03.

2. Data supplied with this Service Bulletin

None.

3. Installation Drawings Used in the Preparation of this Service Bulletin

Document Number Title Change

RIB CRACK REPAIR - HORIZ STAB, A

STATION XH=6.625

SR90550001

This drawing was used to prepare this service bulletin. This drawing is not necessary to make the

specified changes, and is not supplied with this service bulletin. This drawing may not be applicable

to all airplane configurations or operators.

K. Publications Affected

1. Publications:

None.

2. Damage Tolerance Based Structural inspections:

Boeing has evaluated the repairs and/or changes in this service bulletin for effects on Fatigue

Critical Structure (FCS) and for changes to Damage Tolerance inspections (DTI) required in the

Maintenance Program. This service bulletin affects FCS. DTI requirements for the structure affected

are contained in Paragraph 1.E., Compliance of this service bulletin.

L. Interchangeability and Intermixability of Parts

Accomplishment of this service bulletin does not affect interchangeability or intermixability of parts.

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BLANK PAGE
2. MATERIAL INFORMATION

A. Material - Price and Availability

NOTE: Parts are only required for Condition 2B.

Boeing can supply the parts shown in Paragraph 2.C., Parts Necessary for Each Airplane if needed,

as shown below. If there is a limit to the quantity of available parts, a supply sequence is given by

Spares. More parts become available as shown in the Reorder Lead Time (ROLT). ROLT is calculated

from the date Boeing gets the purchase order.

Unit Price thru

April 11, 2011

Part Number Name QTY ROLT (Weeks)

Rib - Horizontal Stabi- 1 13 $14,500.00

lizer Station

Xh=6.625

9911846-511

Rib - Horizontal Stabi- 1 13 14,500.00

lizer Station

Xh=6.625

9911846-512

The parts are subject to the terms and conditions of the Boeing standard purchase order

acknowledgment. After the Unit Price date, new price data is applicable. Prices are in United States

dollars. Terms: Net 30 days.

Reference this service bulletin and submit your purchase order by one of the methods that follow:

1. Order on-line via ATA Spec 2000 or Boeing Part Page

2. Fax to (206) 662-7145

3. Mail to:

Spares Customer Support - MC 36-65

Boeing Spares Department

P.O. Box 3707

Seattle, Washington 98124-2207 USA

B. Industry Support Information

Boeing warranty remedies are not available for the inspection given in this service bulletin.

C. Parts Necessary For Each Airplane

1. Kits/Parts

NOTE: Parts are only required for Condition 2B.

To get the parts shown below, refer to Paragraph 2.A., Material - Price and Availability.

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Existing Part Notes

Number

New Part Number QTY Name

Left

side

Rib - Horizontal Sta- 9911846-511

bilizer Station

Xh=6.625

9911846-511 1

Right

side

Rib - Horizontal Sta- 9911846-512

bilizer Station

Xh=6.625

9911846-512 1

2. Parts and Materials Supplied by the Operator

None.

3. Parts Modified and Reidentified

None.

4. Parts Removed and Not Replaced

None.

D. Parts Necessary to Change Spares

None.

E. Special Tooling - Price and Availability

The operator can supply the tools shown in Paragraph 2.F., Special Tooling Necessary to do this

Service Bulletin. Tool price and supply data are not given.

F. Special Tooling Necessary to do this Service Bulletin

No special tools or equipment are necessary to do the change in this service bulletin. But, maintenance

and overhaul tools in the manuals given in Paragraph 1.J., References, can be necessary. Examine

operator tool supply to make sure all necessary tools are available.

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3. ACCOMPLISHMENT INSTRUCTIONS

A. GENERAL INFORMATION

WARNING: IF ELECTRICAL POWER IS APPLIED TO THE AIRPLANE, MAKE SURE YOU OBEY

ALL PRECAUTIONS WHILE YOU DO WORK. IF YOU DO NOT OBEY THE

PRECAUTIONS, DEATH OR INJURY TO PERSONS, AND DAMAGE TO THE AIRPLANE

CAN OCCUR.

CAUTION: ELECTRICALLY GROUND THE AIRPLANE. THIS WILL HELP TO PREVENT DAMAGE

TO THE AIRPLANE OR EQUIPMENT.

CAUTION: KEEP THE WORK AREA, WIRES AND ELECTRICAL BUNDLES CLEAN OF METAL

PARTICLES OR CONTAMINATION WHEN YOU USE TOOLS. UNWANTED MATERIAL,

METAL PARTICLES OR CONTAMINATION CAUGHT IN WIRE BUNDLES CAN CAUSE

DAMAGE TO THE BUNDLES. DAMAGED WIRE BUNDLES CAN CAUSE SPARKS OR

OTHER ELECTRICAL DAMAGE.

NOTE: 1. The instructions identified in Paragraph 3.B., Work Instructions, and the Figure(s)

give the recommended sequence of steps. The sequence of steps to do this service

bulletin can be changed.

2. Manual titles are referred to by acronyms. Refer to Paragraph 1.J., References, for

definition of the acronyms.

3. Equivalent parts are listed in the AEPL, Drawing 7595071.

4. Use the approved fastener and process material substitutions, in accordance with

MD90 SRM Chapter 51.

5. Unless shown differently, these dimensions and tolerances are used:

– Linear dimensions are in inches

– Tolerance on linear dimensions, other than rivet and bolt edge margins, is plus

or minus 0.03 inch

– Tolerance on rivet and bolt edge margin is plus or minus 0.05 inch

– Angular tolerance is plus or minus 2 degrees

6. Obey all of the warnings and cautions given in the specified manual sections.

7. A Detailed Inspection is defined as: An intensive examination of a specific item,

installation, or assembly to detect damage, failure, or irregularity. Available lighting

is normally supplemented with a direct source of good lighting at an intensity deemed

appropriate. Inspection aids such as mirrors, magnifying lenses, etc. may be

necessary. Surface cleaning and elaborate procedures may be required.

8. These work instructions refer to procedures included in other Boeing documents.

When the words "refer to" are used and the operator has an accepted alternative

procedure, the accepted alternative procedure can be used. When the words "in

accordance with" are included in the instruction, the procedure in the Boeing document

must be used.

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B. WORK INSTRUCTIONS

1. Remove and keep access panels. Refer to MD90 AMM 06-33-00.

Panel Location

350AB Left side lower horizontal stabilizer fairing

360AB Right side lower horizontal stabilizer fairing

2. Do the Eddy Current, High Frequency (ETHF) inspection of the aft face of the center section left

and right rib hinge bearing lugs for cracks in accordance with Figure 1 and do as follows:

CONDITION 1 (NO CRACK FOUND IN RIB HINGE BEARING LUG)

a. Install kept access panels. Refer to MD90 AMM 06-33-00.

Panel Location

350AB Left side lower horizontal stabilizer fairing

360AB Right side lower horizontal stabilizer fairing

b. Put the airplane back to a serviceable condition.

c. Repeat the ETHF inspection of any uncracked horizontal stabilizer hinge bearing lugs in

accordance with Figure 1, at intervals defined in Paragraph 1.E., Compliance Table 1.

CONDITION 2 (CRACK FOUND IN RIB HINGE BEARING LUG)

a. Measure the length of the crack in accordance with Figure 2 and do as follows:

CONDITION 2A (CRACK LENGTH BETWEEN POINTS 'A' AND 'B' IS LESS THAN OR

EQUAL TO 0.15 INCH AND CRACK LENGTH BETWEEN POINTS 'C' AND 'D' IS LESS

THAN OR EQUAL TO 0.05 INCH)

(1) Do blend out repair in accordance with Figure 3.

NOTE: Drawings for a locally manufactured template/shield shop aid that can be used

to help define the blend out area are available in Appendix A.

(2) Install kept access panels. Refer to MD90 AMM 06-33-00.

Panel Location

350AB Left side lower horizontal stabilizer fairing

360AB Right side lower horizontal stabilizer fairing

(3) Put the airplane back to a serviceable condition.

(4) Inspect blend out area for cracks in accordance with Figure 4 at intervals defined in

Paragraph 1.E., Compliance Table 1.

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CONDITION 2B (CRACK LENGTH BETWEEN POINTS 'A' AND 'B' IS GREATER THAN

0.15 INCH OR CRACK LENGTH BETWEEN POINTS 'C' AND 'D' IS GREATER THAN TO

0.05 INCH)

(1) Replace horizontal stabilizer center section rib.

(2) Inspect replaced rib hinge bearing lug for cracks in accordance with Figure 1 at intervals

defined in Paragraph 1.E., Compliance Table 1.

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FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS

(SHEET 1 OF 4)

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FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS

(SHEET 2 OF 4)

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FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS

(SHEET 3 OF 4)

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The step number shown below agree with the number shown in the circle symbol in the figure.

Step Action

Perform an Eddy Current, High Frequency (ETHF) surface inspection of the rib at the hinge

bearing lug aft radius at approximately Stations Yh=76.000 and Xh=6.625. Scan the lug radius as

shown, looking for cracks propagating across the radius following the instructions found in the

NDTSPM 06-10-01.001 (ETHF - Procedure 1). Use Calibration Method "G" and Scan Method "69".

1

Perform an Eddy Current, High Frequency surface inspection of the rib at the hinge bearing lug

aft radius at approximately Stations Yh=76.000 and Xh=6.625. Scan the lug radius as shown,

slightly above the scan done in Step 1, looking for cracks propagating in the vertical direction following the instructions found in the NDTSPM 06-10-01.001 (ETHF - Procedure 1). Use Calibration

Method "C" and Scan Method "62".

2

FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS

(SHEET 4 OF 4)

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FIGURE 2: CRACK LENGTH MEASUREMENT

(SHEET 1 OF 3)

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FIGURE 2: CRACK LENGTH MEASUREMENT

(SHEET 2 OF 3)

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The step numbers shown below agree with the numbers shown in the circle symbols in the figure.

Step Action

Measure the crack length from end point (Point A) to where crack intersects the chamfer (Point

B) on the outboard face of the hinge lug. Do not include the measurement of crack length in

chamfer. Record measurement.

1

Measure the crack length from end point (Point D) to where crack intersects the chamfer (Point

C) on the aft face of the hinge lug. Do not include measurement of crack length in the chamfer.

Record measurement.

2

FIGURE 2: CRACK LENGTH MEASUREMENT

(SHEET 3 OF 3)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 1 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 2 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 3 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 4 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 5 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 6 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 7 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 8 OF 10)

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FIGURE 3: BLEND OUT REPAIR

(SHEET 9 OF 10)

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ALERT ALERT
The step numbers shown below agree with the numbers shown in the circle symbols in the figure.

Step Action

Locate Point 1. Point 1 is identified as the intersecting point of a line offset from the horizontal stabilizer lower surface 0.050 inch, and the outboard edge of the chamfer on the hinge lug.1

Locate Point 2. Point 2 is identified as the point on a line offset from the horizontal stabilizer lower

surface 0.050 inch, and 0.58 inch forward of Point 1.

2

Locate Point 4. Point 4 is identified as the point located 1.59 inch measured normal to the horizontal

stabilizer lower surface at the aft edge of the hinge lug.

3

Locate Point 3. Point 3 is identified as the point located 0.19 inch from the inboard edge of the hinge

lug, and 0.50 inch from the horizontal stabilizer lower surface.

4

Blend out the crack. (Blend 'A') Do not exceed the limits of the area defined by points 1, 2, 3, and 4.

The blend out should form a "V" shape, with the deepest portion of the "V" being in the area of the

crack, and approximately 127 degrees between the legs of the "V". Maintain a 0.25 inch radius at the

bottom of the "V". The majority of the blend should be at approximately 45 degrees from the outboard

face of the lug. It is recommended that a 0.50 inch diameter ball grinder be used to do the blend out.

Remove only enough material to remove the crack. Do not remove more than 0.25 inch of material

total depth as measured from a line drawn between the points B and C that were established in Figure

2.

5

Do an Eddy Current, High Frequency (ETHF) inspections during material removal to verify crack has

been removed. Scan the blend out as shown, looking for cracks in the upper forward to lower aft direction. Scan the blend out and give more attention to the outside periphery in accordance with

NDTSPM 06-10-01.001 (ETHF - Procedure 1). Use Calibration Method "G" and Scan Method "69".

If crack still is not removed, repeat Steps 5 and 6.

6

Once the crack has been removed, remove an additional 0.050 inch of material to ensure that a crack

that is too small to detect has been removed. Finish blend out to a 63 micro-inch finish.

7

Do a taper of the outboard face of the lug. (Blend 'B') The taper begins at a line between Point 4 and

tangent to the radius on the aft portion of the bearing lug surface, and extends upward and aft to a

point 1.65 inches above Point 4. Finish blend out to a 63 micro-inch finish.

8

Break all reworked edges to a 0.12 inch radius. If adjacent structure prevents using a 0.12 inch radius,

use the largest radius possible in the area.

9

10 Apply FR Protection to the rework area. Refer to MD90 SRM 51-10-03.

(Not

Shown)

FIGURE 3: BLEND OUT REPAIR

(SHEET 10 OF 10)

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FIGURE 4: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS

(SHEET 1 OF 2)

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ALERT ALERT
The step number shown below agree with the number shown in the circle symbol in the figure.

Step Action

Perform an Eddy Current, High Frequency Surface inspection of Blend 'A' area at the hinge

bearing lug aft radius. Scan the blend out as shown, looking for cracks in the upper forward to

lower aft direction. Scan the blend out and give more attention to the outside periphery in accordance with NDTSPM 06-10-01.001 (ETHF - Procedure 1). Use Calibration Method "G" and Scan

Method "69".

1

FIGURE 4: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS

(SHEET 2 OF 2)

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This appendix provides instructions for the fabrication and usage of a template/shield shop aid to assist in

simplifying the identification of the extents of the blend out area, if required, identified in Figure 3.

This appendix provides instructions to build a template/shield for use on the left hand hinge bearing lug. A mirror

image template/shield is required for the right hand hinge bearing lug.

FABRICATION

1. Fabricate all parts from 0.050 Inch CRES Sheet, Type 321, per AMS 5510 or equivalent.

2. Identification of parts and assemblies at operator's option, and per operator's shop practice.

3. Fusion weld with gas tungsten arc welding (GTAW).

4. It is acceptable to fusion weld from opposite side than that specified by the welding symbol.

5. If surfaces on -3 and -9 parts are distorted by welding, straighten surfaces to within +/- .010 inch before

use.

6. Tack or continuous weld -11 to the sub assembly from sub-assembly step 3.

7. Trim -7 as shown.

8. Cut or grind radius on -7 as shown.

APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 1 OF 8)

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APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 2 OF 8)

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APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 3 OF 8)

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APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 4 OF 8)

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APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 5 OF 8)

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APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 6 OF 8)

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DIRECTIONS FOR TEMPLATE/SHIELD SHOP AID USE

1. After identifying points 1, 2, 3, and 4 in accordance with the instructions in Figure 3, place template/shield

on lug. Push upper portion of template/shield against the lower surface of the horizontal stabilizer, and the

push the outer portion of the template/shield against the outboard surface of the lug.

2. Slide the template/shield fore and aft until the lower portion of the template is on Point 4, and check that

the template/shield is aligned with Point 2.

NOTE: The aft face of the template/shield may not be in contact with the aft face of the lug when the

template/shield is aligned with Points 2 and 4.

3. Using an appropriate marker, trace the template/shield shape on the aft face of the lug, and on the outboard

face of the lug, to visually define the shape of the blend out area. Do not exceed the limits of the blend out

area defined by Points 1, 2, 3, and 4 established in Figure 3 if they are different than the area defined by

the template/shield.

The template/shield may be secured to the lug and used as a shield to help while grinding the crack out in

accordance with Figure 3.

APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 7 OF 8)

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APPENDIX A: TEMPLATE/SHIELD SHOP AID

(SHEET 8 OF 8)

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ALERT ALERT