### 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. 9E991 ECCN: 

## BOEING PROPRIETARY, CONFIDENTIAL, AND/OR TRADE SECRET Copyright © 2009 The Boeing Company Unpublished Work - All Rights Reserved Boeing claims copyright in each page of this document only to the extent that the page contains copyrightable subject matter.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 Boeing livery are all trademarks owned by The Boeing Company; and no trademark license is granted in connection with this document unless provided in writing by Boeing.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 1 of 50 3.0BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 2 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**

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

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 3 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 4 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**

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### 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 5 of 50Vertical 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** December 16, 2009 Original Issue: February 17, 2010 Revision 1:

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 6 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**

### 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:

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 7 of 50**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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 8 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 9 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 10 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**

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### 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.

**DESCRIPTION CONFIGURATION**  **GROUP** MD-90-30 airplanes

- 1

Airplane Models: MD-90-30 **Group Fuselage Num-**  **ber** 1 2018 1 2094 - 2100 1 2115 1 2117 1 2120 1 2122 - 2123 1 2125 - 2126

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 11 of 50**Group Fuselage Num-**  **ber** 1 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

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 12 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT Group**  **Fuselage Num- ber**  1 2250 - 2251 1 2253 1 2255 - 2263 1 2288 - 2290 1 4001 - 4002 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:

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 13 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT 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 Zone**  **Model** 351, 361 MD-90-30 **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) Compliance Time**  **Action Condition** 
Before the accumulation of 7200 total flight cycles, or within 1505 flight cycles after the original issue dateon this service bulletin, whichever occurs later. Do an Eddy Current, High Frequency inspection ofthe aft face of the horizontal stabilizer center section left and right rib hinge lugs in accordance withAccomplishment Instructions, Paragraph 3.B.2. All Airplanes

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 14 of 50 **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)**  **Compliance Time Action**  **Condition** Within 1680 flightcycles from last inspection. Within 1680 flightcycles from last inspection. Do an Eddy Current, High Frequency inspection ofthe aft face of the uncracked horizontal stabilizer center section rib hinge lugs in accordance withAccomplishment Instructions, Paragraph 3.B.2. CONDITION 1 (No Crack Found in Rib Hinge Bearing Lug)

Before further flight. Measure crack length inaccordance 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 ofthe blend out on the center section rib hinge bearing lug in accordancewith 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 flightcycles 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 ofthe aft face of the replaced horizontal stabilizer center section rib hinge lug in accordance withAccomplishment Instructions, Paragraph 3.B.2.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 15 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT 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. **Elapsed Hours Task Hours**  **Number of Persons Task**  1.0 2.0 2 Open Access 2.0 2.0 1 Inspect 1.0 2.0 2 Close Access 4.0 6.0 TOTAL FOR EACH AIRPLANE
**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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 16 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT 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 **Change Title**  **Document Number** A RIB CRACK REPAIR - HORIZ STAB, 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 17 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 18 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**

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**  **ROLT (Weeks) QTY**  **Name Part Number**  $14,500.00 13 1 Rib - Horizontal Stabi- lizer Station Xh=6.625 9911846-511

14,500.00 13 1 Rib - Horizontal Stabi- 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 19 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT Notes**  **Existing Part Number**  **Name QTY**  **New Part Number**
Left side 9911846-511 Rib - Horizontal Sta- bilizer Station Xh=6.625 1 9911846-511

Right side 9911846-512 Rib - Horizontal Sta- bilizer Station Xh=6.625 1 9911846-512

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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 20 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 21 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT B. WORK INSTRUCTIONS**  1. Remove and keep access panels. Refer to MD90 AMM 06-33-00.
**Location Panel**  Left side lower horizontal stabilizer fairing 350AB Right side lower horizontal stabilizer fairing 360AB 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.
**Location Panel**  Left side lower horizontal stabilizer fairing 350AB Right side lower horizontal stabilizer fairing 360AB 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.
**Location Panel**  Left side lower horizontal stabilizer fairing 350AB Right side lower horizontal stabilizer fairing 360AB (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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 22 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT 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.

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1: February 17, 2010 23 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS**  **(SHEET 1 OF 4)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 24 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS**  **(SHEET 2 OF 4)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 25 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 1: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS**  **(SHEET 3 OF 4)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 26 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**The step number shown below agree with the number shown in the circle symbol in the figure.
**Action Step**  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)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 27 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 2: CRACK LENGTH MEASUREMENT**  **(SHEET 1 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 28 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 2: CRACK LENGTH MEASUREMENT**  **(SHEET 2 OF 3)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 29 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**Action Step**  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)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 30 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 1 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 31 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 2 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 32 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 3 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 33 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 4 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 34 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 5 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 35 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 6 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 36 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 7 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 37 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 8 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 38 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 3: BLEND OUT REPAIR**  **(SHEET 9 OF 10)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 39 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**The step numbers shown below agree with the numbers shown in the circle symbols in the figure.
**Action Step**  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 hasbeen 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 Apply FR Protection to the rework area. Refer to MD90 SRM 51-10-03. 10 (Not Shown)

**FIGURE 3: BLEND OUT REPAIR (SHEET 10 OF 10)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 40 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT FIGURE 4: INSPECT HORIZONTAL STABILIZER HINGE BEARING LUGS**  **(SHEET 1 OF 2)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 41 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**The step number shown below agree with the number shown in the circle symbol in the figure.
**Action Step**  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 tolower 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)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 42 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**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)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 43 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT APPENDIX A: TEMPLATE/SHIELD SHOP AID**  **(SHEET 2 OF 8)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 44 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT APPENDIX A: TEMPLATE/SHIELD SHOP AID**  **(SHEET 3 OF 8)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 45 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT APPENDIX A: TEMPLATE/SHIELD SHOP AID**  **(SHEET 4 OF 8)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 46 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT APPENDIX A: TEMPLATE/SHIELD SHOP AID**  **(SHEET 5 OF 8)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 47 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT APPENDIX A: TEMPLATE/SHIELD SHOP AID**  **(SHEET 6 OF 8)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 48 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT 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)** 

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 49 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT APPENDIX A: TEMPLATE/SHIELD SHOP AID**  **(SHEET 8 OF 8)**

BOEING PROPRIETARY - Copyright © Unpublished Work - See page 1 for details. Original Issue: December 16, 2009 MD90-55A016 Revision 1 February 17, 2010 50 of 50 **BOEING SERVICE BULLETIN MD90-55A016 ALERT**  **ALERT**