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 - REMOVAL OF STIFFENER STRAPS

This revision includes all pages of the service bulletin.

COMPLIANCE INFORMATION RELATED TO THIS REVISION

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 in the original

release of this service bulletin.

SUMMARY

This revision is sent to change the fastener sizes, to give operators a first, second, and full oversize set of

fasteners, and to change the inspection procedure.

As part of a service bulletin validation program, this change was completed on airplane NA005 before the

release of this Revision 1.

Paragraph I.A., Effectivity, shows changes of airplane operators. Each operator should examine the

Effectivity paragraph for 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.

Pages with a revision number and date, but no vertical lines, have no important changes.

REVISION HISTORY

Initial Release: March 31, 1994

Revision 1: August 25, 1994
Number:

Date:

Revision 1:

ATA System:

757-54-0028 Summary March 31, 1994

August 25,1994

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 release of 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

in the lower chord. Repair to 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.

Federal Aviation Administration (FAA) Airworthiness

Directive (AD) 94-14-04, Amendment 39-8956, 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

Elapsed Time - 3 Hours

Removal

Total Man-hours - 92 for each airplane

Elapsed Time - 23 Hours

MATERIAL INFORMATION

Operator Supplied Parts

Summary Page 1 of 2
Mar 31/94

REV 1: Aug 25/94 Summary Page 2 of 

2
Number:

Date:

Revision 1:

ATA System:

757-54-0028

March 31, 1994

August 25, 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 Airplane Variable Number, Line

Number, and Serial Number data.

This service bulletin is for the 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 21
B. Reason

Revision 1 is sent to include first, second, and full oversized fasteners because some fasteners holes

can already have oversized fasteners and to change inspection procedures.

As part of a service bulletin validation program, this change was completed on airplane NA005 before

the release of 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 in the 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 more than the usual time.

One operator found a crack in the lower spar chord of a strut for a RB211-535 engine. The crack was

fully through the inboard flange of the chord and was through 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 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 of the 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 in the original release of this service bulletin.

Get access to the inside of the strut at the mid-chord. Examine the lower spar 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 of the fastener holes can have oversized fasteners. Examine the fastener holes for

the condition of the holes surfaces, and make a note of which holes are oversized. If a crack is

found in a fastener hole, stop and tell Boeing.

An evaluation form is attached to this service bulletin. Please use this form to tell us what you think

of the quality of this 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 related to 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 approved the 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 2
F. Manpower

The data below shows an estimate of the man-hours necessary to do this change for each airplane.

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

man-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 examine the work

- Time to cure the materials

- Time to make the parts

- Time to find the tools.

Task

INSPECTION

Open Access

Examine

Close Access

Number of 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

Close Access 4

TOTAL FOR EACH AIRPLANE

16

60

16

92

4

15

4

23

G. Material - Price and Availability

The operator can 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 show the Boeing price and supply data.

H. Special Tools - Price and Availability

None

I. Weight and Balance

Change in Weight

(Pounds)

-47.5

Change in Moment

(Pound-Inches)

-46550

Mar 31/94

REV 1: Aug 25/94

757-54-0028

3

Airplane

All
J. 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. Boeing Standard Overhaul Practices Manual (BSOPM) 20-10-02

c. 757 Nondestructive Test (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

Not changed

Mar 31/94

REV 1: Aug 25/94

757-54-0028

4
II. 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.

Parts and Materials Supplied by the Operator:

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.

Refer to 757 Structural Repair Manual Chapter 51 for alternative fasteners.

B. Parts Necessary to Change Spares

None

Mar 31/94 757-54-0028

REV 1: Aug 25/94 5
C. 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 necessary tools are available.

D. Existing Parts Accountability

None

Mar 31/94 757-54-0028

REV 1: Aug 25/94 6
III. ACCOMPLISHMENT INSTRUCTIONS

NOTES:

1. The paragraphs identified with a letter give the general work instructions and the necessary tests.

The instructions identified with numbers on the figures give the recommended sequence of steps.

2. 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

- Hole dimensions for standard solid rivets are given in 757 Structural Repair Manual Chapter 51.

- Torque limits to tighten nuts and bolts are given in 757 Structural Repair Manual Chapter 51.

3. Alternative fasteners are given in 757 Structural Repair Manual Chapter 51.

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

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. Do the "Thrust Reverser Deactivation for Ground Maintenance", as shown in AMM 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 in AMM 54-53-01 and 54-53-02.

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 7
PART II - STRAP REMOVAL

A. Remove and keep the fire extinguisher line from the aft side of the bulkhead coverplate.

B. Disconnect and remove the Strut Pneumatic Duct, as shown in AMM 36-11-01.

C. Remove the straps from the Mid-Chord Installation as shown in Figure 2.

D. Examine the fastener holes, enlarge fastener holes as necessary, and install fasteners as shown in

Figure 3.

E. Install the Strut Pneumatic Duct, as shown in AMM 36-11-01.

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 in AMM 54-53-01 and 54-53-02.

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 locks from the leading edge slats, as shown in AMM 27-81-00.

H. Do the Thrust Reverser Activation procedure, as shown in AMM 78-31-00.

I. Put the airplane in a serviceable condition.

Mar 31/94 757-54-0028

REV 1: Aug 25/94 8
FIGURE 1. INSPECTION

Mar 31/94

REV 1: Aug 25/94

757-54-00289
FIGURE 1. INSPECTION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

10
FIGURE 2. STRAP REMOVAL

Mar 31/94

REV 1: Aug 25/94

757-54-0028

11
FIGURE 2. STRAP REMOVAL

Mar 31/94

REV 1: Aug 25/94

757-54-0028

12
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

13
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

14
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

15
STEP 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 Part 6,

51-00-05. NDT Part 6, 51-00-17 is

the recommended NDT

procedure.

For holes where no galling,

corrosion, or damage due to

fastener removal is found, go to

Step 3.

If you find a hole with galling,

corrosion, or damage due to

fastener removal, increase the

hole diameter by 1/64 inch. See

Tables 1 thru 4 for the correct hole

diameters for fasteners A thru 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 Part 6,

51-00-05. NDT Part 6, 51-00-17 is

the recommended NDT

procedure.

For holes where no galling,

corrosion, or damage due to

fastener removal is found, go to

Step 3.

If you again find a hole with

galling, corrosion, or damage due

to fastener removal, increase the

hole diameter by 1/64 inch. See

Tables 1 thru 4 for the correct hole

diameters for fasteners A thru 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 Part 6,

51-00-05. NDT Part 6, 51-00-17 is

the recommended NDT

procedure.

For holes where no galling,

corrosion, or damage due to

fastener removal is found, go to

Step 3.

If you find a hole with a crack or

other damage contact Boeing.

FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

16

NOTES
CAUTION: 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 damage due to bolt

removal is found. Since there

are only full oversized fasteners

listed in the fastener tables, the

fastener holes have to be

reamed to the next full oversize.

2

FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

17

NOTES
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

18
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

19
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

20
FIGURE 3. BOLT INSTALLATION

Mar 31/94

REV 1: Aug 25/94

757-54-0028

21
Number:

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 evaluation form to tell us what 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:

- Did this service bulletin meet your estimate of quality?

- How easy is this service bulletin to understand?

- Are the Planning Information, Material Information and Accomplishment Instructions satisfactory?

- Will you do this service bulletin fully? If not, please tell us why.

- Is the Manpower estimate satisfactory?

NOTE: Please do not use this evaluation form to tell us to make changes to your manuals. To make these

changes, please use a Publication Change Request (PCR) form.

Please give us this data:

OPERATOR: TODAY'S DATE:

PREPARED BY:

ORGANIZATION:

TELEPHONE NUMBER:

TITLE:

TELEX CODE:

BASE:

COMMENTS: