### Number: 757-54-0028 

## Revision Transmittal Sheet Date: March 31, 1994 Revision 1: August 25, 1994 ATA System: 5451

SUBJECT: NACELLES/PYLONS
- CRACKED LOWER CHORD
- REMOVALOFSTIFFENER STRAPS

This revision includes all pages ofthe service bulletin. COMPLIANCE INFORMATION RELATED TO THIS REVISION No morework is necessary on airplanes changed bythe initial release ofthis service bulletin More work is necessary on airplanesthat did not have the stiffener straps removed as shown inthe original releaseof this service bulletin. SUMMARY This revision is sent to change the fastener sizes, to give operators afirst, second, and full oversize set of fasteners,andto changethe inspection procedure. As part of a service bulletin validation program, this change was completed on airplane NA005 before the releaseof this Revision 1. Paragraph I.A., Effectivity, shows changes of airplane operators. Each operator should examine the Effectivity paragraphfor changes. Vertical lines are put on the left edge,of each page, except in Paragraph I.A., Effectivity,to show the location of important changes. Pageswith a revision numberand date, but novertical lines,have no important changes. REVISION HISTORY Initial Release: March 31, 1994 Revision 1: August25, 1994Number: Date: Revision 1: ATA System: 

## Summary 757-54-0028 March 31, 1994 August25,1994 5451

SUBJECT: NACELLES/PYLONS
- CRACKED LOWER CHORD
- REMOVAL OF STIFFENER STRAPS

BACKGROUND COMPLIANCE As part of a service bulletin validation program, this change was completed on airplane NA005 before the releaseof this Revision 1. One operator found a crack in the lower spar chord of a strut for a RB211-535 engine. The crack was through the inboard flange of the chord and went into the skin flange of the chord. The crack in the skin flange was approximately 5 inches long. Analysis shows that the stiffener straps make the structure more likely to have cracks. Removal of stiffener straps from the mid-chord of each strut will make it less possible for cracks to start in the lower spar chord. Continued operation, with the stiffener straps installed, will cause cracks inthe lowerchord. Repairto this area is difficult and could keep the airplane out of service for more than the usual time. ACTION Get access to the inside of the strut at the mid-chord. Examine the lower spar chord for cracks. Remove the stiffener straps from the mid-chord. Examine the fastener holes. If cracks are found, tell Boeing. If no cracks are found, oversize the fastener holes if necessary, and install the new fasteners. FederalAviation Administration (FAA) Airworthiness Directive (AD) 94-14-04,Amendment39-8956, Final Rule Docket Number 94-NM-85-AD is related to this service bulletin. EFFECTIVITY 757 Airplanes, Airplane Variable Numbers NA002, NA004, NA005, NA009, NA012, NA014, NA024, NA025, and NA201 through NA204. MANPOWER Inspection Total Man-hours
- 12 for each airplane ElapsedTime
- 3 Hours Removal Total Man-hours
- 92 for each airplane ElapsedTime
- 23 Hours MATERIAL INFORMATION Operator Supplied Parts

Summary Page 1 of 2Mar 31/94 REV 1: Aug 25/94 Summary Page 2 of 2Number: Date: Revision 1: ATA System: 757-54-0028 March 31, 1994 August25, 1994 5451
SUBJECT: NACELLES/PYLONS
- CRACKED LOWER CHORD
- REMOVAL OF STIFFENER STRAPS

I. PLANNING INFORMATION A. Effectivity 1. Airplanes Refer to Service Bulletin Index Document D624N001, Part 3 for AirplaneVariable Number, Line Number,and Serial Number data. This service bulletin isforthe airplanes shown below. IDENTIFICATION BY CUSTOMER, CUSTOMER CODE, GROUP AND VARIABLE NUMBER
AIR 2000, LTD. (ATZ) NA024 BRITISH AIRWAYS (BAB) NA201-NA204 EASTERN AIR LINES, INC. (EAL) NA002 NA005 LUFTTRANSPORT SUED AG AND CO. (LTS) NA025 USAIR, INC. (USA) NA004 NA009 NA012 NA014
IDENTIFICATION BY VARIABLE NUMBER NA002 NA004-NA005 NA009 NA201-NA204 2. Spares None

Mar 31/94 REV 1: Aug 25/94 NA012 NA014 NA024-NA025

757-54-0028 Page 1 of 21B. Reason Revision 1 is sent to includefirst, second, andfull oversizedfasteners because some fasteners holes can already have oversizedfasteners andto change inspectionprocedures. As part of a service bulletin validation program,this changewas completed on airplane NA005 before the releaseof this Revision 1. Removal of stiffener straps from the lower spar chord of each strut will prevent cracks in the chord. Continued operation, with the stiffener straps installed, can cause cracks inthe lower chord or make existing cracks longer. Repair to this area of the structure is difficult and could keep the airplane out of service for morethan the usualtime. One operator founda crack inthe lower spar chordof a strut for a RB211-535 engine. The crackwas fully through the inboard flange of the chord andwas through the skinflange of the chord. The crack inthe skin flange was approximately 5 inches long. Analysis shows thatthe stiffener straps make the structure more likely to crack. This service bulletin gives instructions to examine the lower chord and the midspar fitting for cracks. The service bulletin also gives instructions to remove the top and bottom stiffener straps from the inboard and outboard sides ofthe struts. C. Description Revision 1 - no more work is necessary on airplanes changed by the initial release of this service bulletin. More work is necessary on airplanes that did not have the stiffener straps removed as shown inthe original release of this service bulletin. Get access to the inside of the strut at the mid-chord. Examinethe lowerspar chord for cracks. If a crack is found on the spar lower chord, stop and tell Boeing. Remove the stiffener straps from the mid-chord. After the stiffener straps are removed from the mid-chord, measure the fastener hole diameters. Some ofthe fastener holescan have oversized fasteners. Examinethe fastener holes for the condition of the holes surfaces, and make a note of which holes are oversized. If a crack is found in afastener hole,stop andtell Boeing. An evaluation form is attached to this service bulletin. Please use this form to tell us what you think of the quality ofthis service bulletin. D. Compliance Federal Aviation Administration (FAA) Airworthiness Directive (AD) 94-14-04, Amendment 39-8956, Final Rule Docket Number 94-NM-85-AD is relatedto this service bulletin. E. Approval. The FAA has examined the change, inspection, and repair procedures specified in Revision 1 to Service Bulletin 757-54-0028, "NACELLES/PYLONS
- CRACKED LOWER CHORD
- REMOVAL OF STIFFENER STRAPS". The FAA has approvedthe change, inspection,and repair procedures as an alternative to those specified in Airworthiness Directive (AD) 94-14-04, Amendment 39-8956, Final Rule Docket Number 94-NM-85-AD.

Mar 31/94 757-54-0028 REV 1: Aug 25/94 2F. Manpower The data below shows an estimate of the man-hours necessaryto do this change for each airplane. This estimate is for direct labor only,done by an experienced crew. Adjust theestimatewith operator man-hourdata if necessary. The estimatedoes not include losttime. These are some examples of losttime:

- Time to adjustto theworkplace

- Time to schedule thework

- Time to examine thework

- Time to cure the materials

- Time to makethe parts

- Time to findthe tools. Task INSPECTION Open Access Examine CloseAccess Numberof Persons
4 4 4 TOTAL FOR EACH AIRPLANE REMOVE STRAPS Man-Hours Elapsed Time (Hours)
4 4 4 12 1 1 1 3 Open Access Remove and Examine 4 4 CloseAccess 4 TOTAL FOR EACH AIRPLANE 16 60 16 92 4 15 4 23
G. Material
- Price and Availability The operatorcan supply the parts and materials shown in Paragraph II.A., Parts Necessary For Each Airplane. As an alternative, operators can purchase the parts from Boeing Spares. This service bulletin does not showthe Boeing price and supplydata. H. SpecialTools - Price and Availability None I. Weight and Balance Change inWeight (Pounds)

-47.5 Change in Moment (Pound-Inches) -46550

Mar 31/94 REV 1: Aug 25/94 757-54-0028 3 Airplane AllJ. References

1. Existing Data: a. 757 Maintenance Manual (AMM)Subject 27-81-00,36-11-01, 54-53-01,54-53-02, 78-31-00 b. BoeingStandard Overhaul PracticesManual (BSOPM)20-10-02
c. 757 NondestructiveTest (NDT) Manual, Part 6, Subject 51-00-05,51-00-12, 51-00-17
K. Publications Changed Publication 757 Structural Repair Manual 

### Chapter-Section 54-50

L. Electrical Load Data Notchanged

Mar 31/94 REV 1: Aug 25/94 757-54-0028 4II. MATERIAL INFORMATION A. Parts Necessary For Each Airplane NOTE:The table below shows all possible combinations of fasteners,collars,washers, and nuts that can be used on this repair. Partsand Materials Supplied bytheOperator: Quantity Part Number (Specification) Name 24 BACB30US8K18X Bolt 24 BACB30US8K18Y Bolt 24 BACB30LE8K20 Bolt 24 BACB30US8K20X Bolt 24 BACB30US8K20Y Bolt 8 BACB30LE9K9 Bolt 24 BACB30LE9K18 Bolt 24 BACB30LE9K20 Bolt 12 BACB30NX12K9 Bolt 12 BACB30NX12K10X Bolt 12 BACB30NX12K10Y Bolt 12 BACB30NX14K9 Bolt 8 BACB30US1 K9 Bolt 12 BACC30X14 Collar 12 BACC30X12SW Collar 24 BACN10HR8CS Nut 32 BACN10HR9CS Nut 8 BACN10HR10CS Nut 16 BACW1 0BP8APU Washer 8 BACW10BP81APU Washer 8 BACW1 BP82APU Washer 8 BACW1 BP9ACU Washer 32 BACW1 0BP9APU Washer 8 BACW1 0BP10ACU Washer 8 BACW10BP10APU Washer 24 BACW10CA8CCU Washer, Self-Aligning (a) 24 BACW1 CA8CVU Washer, Self-Aligning (a) 24 BACW10CA9CC Washer, Self-Aligning (b) 24 BACW10CA9CV Washer, Self-Aligning (b) (a) The Washers BACW1 0CA8CCU and BACW10CA8CVU are a pair of self-aligning washers. (b) The Washers BACW1 OCA9CC and BACW1 OCA9CV are a pair of self-aligning washers. Referto 757 Structural RepairManual Chapter51 for alternativefasteners. B. Parts Necessaryto Change Spares None

Mar 31/94 757-54-0028 REV 1: Aug 25/94 5C. Special Tools and Equipment 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 I.J., References, can be necessary. Examine operator tool supply to make sure all necessarytools are available. D. Existing PartsAccountability None

Mar 31/94 757-54-0028 REV 1: Aug 25/94 6III. ACCOMPLISHMENT INSTRUCTIONS NOTES: 1. The paragraphs identifiedwith a letter give the general work instructions and the necessarytests. The instructions identifiedwith numberson the figuresgive the recommendedsequence of steps. 2. Unless showndifferently, these dimensions andtolerances are used:

- Lineardimensions are in inches

- Tolerance on linear dimensions, other than rivet and bolt edge margins, is plus or minus 0.03

inch

- Tolerance on rivetand boltedge margin is plus or minus 0.05 inch

- Angular tolerance isplus or minus2 degrees

- Hole dimensionsfor standard solid rivetsare given in 757 Structural Repair Manual Chapter 51.

- Torque limitsto tighten nuts and bolts are given in 757 Structural RepairManualChapter 51. 3. Alternative fasteners are given in757 Structural Repair ManualChapter 51. 4. Obey all ofthe warnings and cautions given inthespecified manualsections. PART I
- INSPECTION WARNING: DO THE THRUST REVERSER DEACTIVATION PROCEDURE TO PREVENT THE OPERATION OF THE THRUST REVERSER, THE ACCIDENTAL OPERATION OF THE THRUST REVERSER CAN CAUSE INJURIES TO PERSONS OR DAMAGE TO EQUIPMENT.
A. Dothe "Thrust Reverser Deactivationfor Ground Maintenance", asshown inAMM 78-31-00. WARNING: INSTALL LOCKS IN THE LEADING EDGE SLATS. ACCIDENTAL OPERATION OF THE SLATS CAN CAUSE INJURY TO PERSONS AND DAMAGE TO EQUIPMENT. B. Do the deactivation procedure for the leading edge slats in the retracted position, as shown in AMM 27-81-00. C. Open the access door on the aft fairing. Remove and keep the panel opposite the bulkhead coverplate, as shown inAMM 54-53-01 and54-53-02. D. Make an inspection of the chord as shown in Figure 1. E. If a crack is found, tell Boeing. If no cracks are found, remove the straps as shown in PART II
- STRAP REMOVAL.

Mar 31/94 757-54-0028 REV 1: Aug 25/94 7PART II
- STRAP REMOVAL

A. Removeand keepthe fire extinguisher linefrom the aft side ofthe bulkheadcoverplate. B. Disconnect and remove the Strut Pneumatic Duct, as shown in AMM 36-11-01. C. Removethe straps fromthe Mid-Chord Installationas shown in Figure2. D. Examine the fastener holes, enlarge fastener holes as necessary, and install fasteners as shown in Figure 3. E. Installthe Strut Pneumatic Duct,as shown inAMM36-11-01. F. Install the fire extinguisher line from the aft side of the bulkhead coverplate. Install the bulkhead coverplate, and the panel opposite the access door on the aft fairing. Close the access door on the aft fairing, as shown inAMM 54-53-01 and54-53-02. WARNING: IF THE SLATS MOVE FROM THE RETRACTED POSITION, INJURY COULD OCCUR TO PERSONS IN THE AREA OF THE SLATS. MAKE SURE ALL PERSONS AND EQUIPMENT ARE AWAY FROM THE SLATS. G. Remove the locksfrom the leading edge slats, as shown inAMM 27-81-00. H. Dothe Thrust ReverserActivation procedure, as shown in AMM 78-31-00.

I. Putthe airplane ina serviceable condition.

Mar 31/94 757-54-0028 REV 1: Aug 25/94 8FIGURE 1. INSPECTION Mar 31/94 REV 1: Aug 25/94 757-54-0028 9FIGURE 1. INSPECTION Mar 31/94 REV 1: Aug 25/94 757-54-0028 10FIGURE 2. STRAP REMOVAL
Mar 31/94 REV 1: Aug 25/94 757-54-0028 11FIGURE 2. STRAP REMOVAL Mar 31/94 REV 1: Aug 25/94 757-54-0028 12FIGURE 3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 13FIGURE 3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 14FIGURE 3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 15STEP TASK 2 Examine NAME PART NUMBER QTY Holes

Examine First oversized holes

Examine Second oversized holes 11 Visual and NDT Part 6, 51-00-17 or Visual and NDT Part6, 51-00-05. NDT Part 6, 51-00-17 is the recommended NDT procedure. Forholeswhere nogalling, corrosion,or damage dueto fastener removal is found, goto Step 3. Ifyou find a holewith galling, corrosion,or damage due to fastener removal, increasethe hole diameter by 1/64 inch. See Tables 1thru 4for the correct hole diametersfor fasteners Athru D. If you find a hole with a crack, get necessary repair data from Boeing. Visual and NDT Part 6, 51-00-17 or Visual and NDT Part6, 51-00-05. NDT Part 6, 51-00-17 is the recommended NDT procedure. Forholeswhere nogalling, corrosion,or damage dueto fastener removal is found, go to Step 3. Ifyou againfind a holewith galling, corrosion,or damage due to fastener removal, increase the hole diameter by 1/64 inch. See Tables 1thru 4for the correct hole diameters forfasteners Athru D. If you find a hole with a crack, get necessary repairdata from Boeing. Visual and NDT Part 6, 51-00-17 or Visual and NDT Part 6, 51-00-05. NDT Part 6, 51-00-17 is the recommended NDT procedure. Forholes where no galling, corrosion, or damage dueto fastener removal is found,go to Step 3. If you find a hole with a crack or otherdamage contact Boeing.

FIGURE 3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 16 NOTESCAUTION: THE MIDSPAR FITTING IS MADE FROM 4330M STEEL, HEAT TREATED TO 220-240 KSI. IF YOU DRILL THE HOLES THROUGH THE MIDSPAR FITTING TOO QUICKLY, YOU WILL DAMAGE THE FITTING. USE THE DATA GIVEN IN BSOPM 20-10-02 FOR "TYPE 2" MATERIAL, TO GET THE CORRECT SPEED AND FEED WHEN YOU DRILL AND REAM THESE HOLES. A DRILL GUIDE USED WITH A PILOTED REAMER IS RECOMMENDED TO GET THE FINAL HOLE DIAMETER. STEP TASK NAME PART NUMBER QTY

3 Select Fasteners
4 Install 5 Drill / Ream

6 Install Fasteners Holes



### Fasteners 9 Use fasteners from Tables 1 thru 4. 9 2 Fastener Code E has to be oversized even if no galling, corrosion,or damagedueto bolt removal isfound. Sincethere are only fulloversizedfasteners listed in the fastener tables, the fastenerholes haveto be reamedto the nextfull oversize. 2

FIGURE 3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 17 NOTESFIGURE3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 18FIGURE 3. BOLT INSTALLATION Mar31/94 REV 1: Aug 25/94 757-54-0028 19FIGURE3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 20FIGURE 3. BOLT INSTALLATION Mar 31/94 REV 1: Aug 25/94 757-54-0028 21Number: Date: Revision 1: ATA System: Prepared By: 757-54-0028 March 31, 1994 August25, 1994 5451 Hugh Beauregard 

## Evaluation Form

SUBJECT: NACELLES/PYLONS
- CRACKED LOWER CHORD
- REMOVAL OF STIFFENER STRAPS

Use this evaluationform to tell uswhat you think of the quality of this service bulletin. We will use the data that you give us to improve the quality of our service bulletins. Please include data about these or other items:

- Didthis service bulletin meet your estimateof quality?

- Howeasy isthis service bulletinto understand?

- Arethe Planning Information, Material InformationandAccomplishment Instructionssatisfactory?

- Will youdo this service bulletin fully? If not, pleasetell uswhy.

- Isthe Manpower estimatesatisfactory? NOTE: Please do not use this evaluationform to tell usto make changesto your manuals. To makethese changes, please usea PublicationChange Request (PCR)form. Pleasegive usthis data: OPERATOR: TODAY'S DATE: PREPARED BY: ORGANIZATION: TELEPHONE NUMBER: TITLE: TELEX CODE: BASE: COMMENTS: