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STRUCTURAL REPAIR MANUAL A320

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SRM A320

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STRUCTURAL REPAIR MANUAL
Introduction
Manufacturers publish Structural Repair Manual (SRM) to provide data for the
structural maintenance of commercial airplanes which have sustained structur-
al damage.
The Manuals are approved by the Aircraft Manufacturers Aviation Authority, for
example
D.G.A.C. : Direction Generale De L‘Aviation Civile (France)
FAA: Federal Aviation Administration (USA).
They are available as hardcopy, microfilm or soon on CD-- ROM. As originally
issued, the Structural Repair Manual contains:
S material identification for structure subject to field repair
S typical repairs general applicable to structural components of the airplane
that are most likely to be damaged
S informatieu relative to material substitution
S fastener installation
S airplane alignment check procedure and a brief description of procedures
that must be performed concurrently with structural repair, such as protec-
tive treatment of repair parts and sealing of integral fuel tanks.
Either it has not been found practicable to design a typical repair, or service
experience has not yet indicated a requirement. In some instances, an ade-
quate repair design will require evaluation by the Manufacturer. Consider the
following when typical repairs are not found:
S Accomplish a repair in accordance with the general repair practices and pro
cedures provided in chapter 51 -- Structures General -- of the manual
S Preparing a specific repair design for the damage not covered
S Replacing of the damaged part
As service experience indicates a requirement, the manual will be revised to
include actual, specific repairs to both primary and secondary structures. To
ensure consistent handling of these revisions, index categories have been es-
tablished for all known types of repairs, although some information which falls
within these categories will not be released until warranty service experience.
It is indented that, in the event of a major damage, the information included in
the manual be supplemented as required by direct liaison with the repair as-
signed Manufacturer Customer Support Representative. For ordering structural
repair parts, see Spare Parts Identification, located in the 00-- Introduction Part.
The manual will serve as a medium through which the airplane operators will
be advised of actual repairs with general-- interest nature, designed by the
Manufacturer or by the airplane operator.
SERVICE BULLETINS.
Service Bulletins wich have incorporated are listed in the 00 -- Introduction sec-
tion.
Service Bulletins are recommendations from Manufacturer, wich are not urget
to put into action.

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CHAPTERIZATION
In accordance with the ATA Specification No. 100, the material presented in
this manual is divided into seven chapters.
Chapter numbers
S Chaptcr 51 Structures -- General
S Chapter 52 Doors
S Chapter 53 Fuselage
S Chapter 54 Nacelles/ Pylons
S Chapter 55 Stabilizers
S Chapter 56 Windows
S Chapter 57 Wmgs
SECTION NUMBERING
Chapte numbers are sub-- divided into section numbers. In some instances
specific section number allocations are made to cater for structural variations
between model differences.
CHAPTER 51
Chapte 51 deals with those subjects which are general in nature to the entire
structure of the airplane. It is arranged to allow maximum utilization of common
data. The assigned section numbers are as follows:
Chapter Section
Number Nomenclature
S 51 --00 General
S 51 --10 Investigation, Clean up of Damage and Aerodynamic Smooth
ness
S 51 --20 Processes and Procedures
S 51 --30 Materials
S 51 --40 Fasteners
S 51 --50 Support of Airplane for Reparand Symmetry Check
S 51 --60 Control Surface Balancing
S 51 --70 Repairs

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PAGE BLOCK ALLOCATION
In Chapters 52 thru 57 each subject represents a structural element. All of the-
data concerning that element are covered within that subject. To provide topic-
separat on page blocks are used.
IDENTIFICATION: Page 1 to 99
ALLOWABLE DAMAGE: Page 101 to 199
REPAIRS: Page 201 to 999
Chapter 51 has no identifying page block. In this case a description page block-
could extent up to page 199.
Figure numbering
Figure numbers are to be allocated sequentially within page blocks. Figure
numbers in page block 1 thru 99 will start at Fig. 1 in page block 101 thru 199
at Fig. 101 and in page block 201 at Fig. 201.

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REVISION SERVICE
List of effective pages
The SRM is provided with a List of Effective Pages. All pages are listed in se-
quence, together with their latest revision date. In Airbus Manuals the list is
located in every ATA Chapter. (Boeing provides it in the Manuals Introduction.)
the List of Effective Pages will be revised with each regular revision of the-
Manual
Regular revision service
Revision service to the manual will be issued periodically.
Each manual takes a revision number and date of issue on the outside label, to
chec the effectivity of the hole Manual by a document list. Pages which are
revised will be so indicated on the list of effective pages by an asterisk (*) and
identified by a date. A revised page may be dated prior to, or as same as, the
date of the revision cycle. On each individual page the revised area is indicated
by a revision bar on the left margin. Those pages which have not been techni-
cally revised, but have been reprinted due to recomposition, are also indicated
by a revision bar beside the chapter I section and page number or date.
Temporary revision service
Temporary revision service to the manual will be issued as necessary to alert
the customer of configuration differences and to provide temporary instructions
prior to the next scheduled revision. Temporary revision will also be issued as a
result of a customer request for planned incorporation of a service bulletin.
Each temporary revision will be incorporated into the manual within 90 days-
from date of issuance, except from those temporary revisions, issued as a re-
sult ol planned incorporation of a service bulletin. these service bulletin tempo-
rary revisions will remain active until the Manufacturer has been advised by the
customer that incorporation of the service bulletin into the airplane has been
completed. Each te nporary revision will apply to one subject only and will be
keyed within this manuai, so that the temporary revision will be filed adjacent to
the affected pages.
Temporary revisions will not be revised if changes are required to an existing-
temporary revision, the temporary revision will be reissued.

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AIRPLANE EFFECTIVITY DESIGNATIONS
This non--customized Structural Repair Manual contains information applicable-
to the airplanes, listed in the Airplane Effectivity Allocation List, located in the
Introduction part of the SRM. They relate current operator code, airplane model
series designation, manufacturers serial number (MSN), and customer abbrevi-
ation. Pages that have no effectivity designation are applicable to all airplanes.
Effectivity designations are used to define configuration differences between
airplanes. Effectivity designation will appear in one of the following forms:
Use of the customer abbreviation code, such as AFR or DLH, indicates that the
information is applicable to all airplanes of that customer.
Use of the effectivities Manufacturers Serial Number, shown as (B) Before or
(A) After modification.
All modifications are shown in the Modification / Service Bulletin List.
Use of a generic designator which includes a readily identifiable feature.
For example:
for airplanes with optional forward airstairs, or which is related to model, like:
A320
Airplane allocation list Airbus A320
Containing information about:
S Aircrsft Manufacturer Serial Number
S Aircraft Type
S Version Number
S Customer
S Customer Abbreviation
S Registration Number

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NUMBERING SYSTEM
Each subject, within the SRM, is identified using a three--element numbering
system Chapter/Section and Sub--section.
The first element designates the chapter which is assigned by the ATA spec.
100.
The second element designates the section within the chapter. The first digit is
assigned by the ATA spec. 100.
The second digit is assigned by Airbus SAS.
The third e ement identifies the subsection (subject) within the section and is
assigned by Airbus SAS.

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Figure 1

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SUBJECT NUMBERING
Subject numbers within the chapter / section structure of Chapter 51 will be
assigned sequentially.
In Chapter 52 thru 57 a consistent numbering system will be applied.
The subject numbers that have been assigned are shown below. Each section-
will only use the subject numbers applicable to the structural elements that are-
described in the section.
This will mean that the subject numbers are not necessarily sequential, but it is
anticipated that regular manual users will become familiar with the consistent-
number system and will be able to turn directly to their area of interest.
Subject numbers assignment
Chapters 52 thru 57
5X--XX --00 General
S --01 Skins and Plates
S --02 Structure Complete
S --03 Stringers and Skin Stiffeners
S --04 Intercostals
S --05 Longerons
S --06 Formers
S --07 Frames
S --08 Bulkheads
S --09 Ribs
S --10 Spars
S --11 Intermediate, Auxiliary and Subspars
S --12 Keel Structure
S --13 Beams
S --14 Landing Gear Support Structure
S --15 Door Surround Structure
S --16 Edge Members
S --17 thru
S --29 not used

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PROCEDURE FOR MANUAL USAGE
The following procedure is recommended for the efficient use of the Structural
Repair Manual:
Check for allowable damage.
From the Table of Contents of the manual find the chapter to which the dam-
aged part belongs.
Turn to the Table of Contents of the selected chapter, find subject number of
Allowable Damage.
Damage Classification-- General, to determine if the damage is allowable. Iden-
tify the damaged part. If it is found that the damage exceeds the allowable, the
part must be identified in order to determine the applicable repair figure.
From the Table of Contents of that chapter, find subject number of identification
figure, that includes the damaged part. Find the item number of the damaged
part from the identification figure.
Check modification status of the damaged part. Turn to tabulation sheet of the
identification figure. Find the applicable repair figure number. Apply repair figure
to actual damage. Turn to he repair figure mentioned above, read notes and
instructions carefully, and perform the repair according to the figure.
Use the Table of Contents, at the beginning of each chapter, as a numerical
index to locate a specific subject within a specific section of a chapter. Read all
the text material, supporting figures and references within a specific subject
Chapter 51 lists the sections and subsections generally applicable (except
when limited) to the entire airplane.
Chapters 52,53, 54, 55, 56, and 57 list such sections and subjects which are
applicable respectively to those specific chapters only.
The use of the table of contents to locate specific repairs, supplements the in-
formation given above. Within every chapter, except 56, any subject which con-
tains the word ”repair”, lists each repair figure number and title which is applica-
ble to the specific subject.
Look for all the Cross--References to the Maintenance Manual, Process Speci-
fications and Standard Practice Manuals.

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DEFINITION OF DAMAGE
Scratch
A scratch is a line of damage of any depth and length in the material which-
causes a cross--sectional area change. A sharp object usually causes it.
Gouge
A gouge is a damage area of any size which results in a cross--sectional area-
change It is usually caused by contact with a relatively sharp object, which pro-
duces a continuous, sharp or smooth channel -- like groove in the material.
Mark
A mark is a damage area of all sizes were a concentration of scratches, nicks,
chips, burrs or gouges etc. is shown. You must prepare the damage as an area
and not as a series of individual scratches, gouges etc.
Crack
A crack is a partial fracture or complete break in the material.
Dent
A dent is a damaged area which is pushed in, with respect to its usual contour.
here is no cross--sectional area change in the material, area edges are smoott
Nick
A smal decrease of material due to a knock at the edge of a member or skin.
Distortion
Any twisting, bending or permanent strain which results in misalignment or-
change of shape. May be caused by impact from a foreign object, but usually
esults from vibration or movement of adjacent attached components. f his
group includes bending, buckling, deformation, imbalance, misalignment,
pinching and twisting.
Corrosion
The destruction of metal by chemical or electro--chemical effect.
Abrasion
An abrasion is a damage area of all sizes which causes change in across--sec-
tional area because of scuffing, rubbing, scraping or other surface erosion. It is
usually rough and irregular.
Debonding
Debonding is when a separation of materials occurs due to an adhesive failure.
Delamination
Delamination is when the separation of plies occurs in a multi--laminate materi-
al. This can be caused by the material being hit -- impact, or when there is a
resin failure for any other reason.
Fretting
Surface damage at the interface between elements of the joints resulting from-
very small angular or linear movements. Evidence of fretting is usually the pro-
duction of fine black powder staining.

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Figure 2

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DAMAGE
Causes of Damage
The majority of damages to bonded honeycomb assemblies result from flight-
loads or improper ground handling. Honeycomb structures may also be dam-
aged by sonic vibrations. Such damage is usually a delamination or separation
of the core and face along the bond line. (The bond line is the thin line of adhe-
sive between the core and the face that holds the two together.) Occasionally
the core may collapse.
Damage Inspection
Inspection for damage is more critical for honey comb assemblies than for
conventional structures, A honeycomb structure can suffer extensive damage-
without any observable indication. Sonic vibration, liquid leakage, internal
condensation, or a misstep in manufacture or repair can cause or result in var-
ied amounts of delamination.
The metallic ring test is the simplest way to inspect for delamination damage.
When a coins lightly bounced against a solid structure, a clear metallic ring-
should be heard. If delamination is present, a dull thud will be heard. A 1 oz.
aluminum hammer makes an excellent tool for this type of inspection.
Occasionally, he delaminated skin will ”oil can” away from the core, making
visual or thumb pressure detection possible. Punctures, dents, scratches,
cracks, or other such damage may be inspected by conventional methods.
Scratches should be given special attention since, with such thin material as-
that used in the metal bonded honeycomb, the scratch may actually be a crack.
A caustic soda solution can be used for testing scratches on aluminum surface-
panels. If the scratch area turns black after the application of a small amount of
the solution, the scratch has penetrated through the clad surface. Caustic soda
solutions are highly corrosive and must be handled with extreme care.Through-
ly neutralize the area after application of the solution.
Two additional instruments used in damage inspection of bonded panels are
the panel inspection analyzer and the borescope.
Damage Evaluation
After inspections on metal bonded honeycomb structures are completed, any-
damage found must be evaluated to determine the type of repair needed to-
make the structure serviceable. Damage to aluminum honeycomb structures
can vary from minor dents or scratches to total panel destruction. Damage
evaluation charts for honey--comb structures can be found in the applicable
section of the structural repair manual for the specific aircraft. The charts
specfy types of damage, allowable damage, damage requiring repair, and fig-
ure numbers that illustrate similar repairs for each type of damage. Once the
type of repair is determined, procedures outlined in the structural repair manual
should be rigidly followed.

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DAMAGE CLASIFICATION
The term “Damage” includes any and every type of permanent deformation or
alteration to any cross--section of a structural component. Deformation or alter-
ation to the cross--section of a structural component results from many causes,
which can be generally categorized into four main groups:
S mechanical action
S chemical or electrochemical reaction
S thermal action or cycling
S inherent metallurgical characteristics
Examination of damage
Examine the type and extent of the damage, to determine the damage catego-
ry.
Remove all unwanted material from the surface of the damaged component,
cut out all broken, bent, heated or badly damaged areas of the component, re-
move all loose rivets. In all forms of damage, particularly where shock has
been sustained, secondary damage is likely to exist. Therefore, a close ex-
amination of the structure surrounding the initial damage must be made. Dam-
age caused by transmission of force may be located some distance from the
impact, resulting in structure deformation, drawn rivets or bolt holes.
If misalignment or twisting of the airplane structure is suspected, alignment
and/or leveling checks must be carried out.

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DAMAGE CATEGORIES
Non allowable damage
Damage which exceeds the ‘Allowable Damage” limits can be repaired by cut-
ting out the damaged area of a structural component and inserting or attaching
a reinforcing piece, These specific repairs are to be found in each chapter of
this manual.
Non repairable damage
Non--repairable damage is defined as damage to structural components, which
cannot be repaired and where replacement of the complete component is rec-
ommended as a repair is not practical or economical.
Refer to Chapter 51 for ‘Replacement of Structural Components’.
After cleaning and investigating the damage and surrounding area, the damage
must be classified into one of the following categories, also taking into account
the location of the damage.
Repairable damage
The damage must be classified either as ‘Allowable Damage’ or as damage-
which requires a repair.
Allowable damage
Allowable damage is defined as a minor damage which does not affect the
structural integrity or decrease the function of a component. Allowable damage
values specified in each chapter are by definition established in such a way
that damage within that limit does not require a structural repair during the de-
sign life goal of the airplane, for example 48000 flight cycles. Although no struc-
tural repair is necessary, it does not mean that no action has to be taken. Minor
repairs, such as blend out of a scratch or restoration of protective treatment is
generally required.
Clean the area before examination in order to see if the damage is within allow-
able limits.
For example, in the case of corrosion, you first remove the corrosion and then
examine the extent of the damage. Compare the extent of the damage with the
allowable damage limits. Operating limits are defined as the limit for airplane
operation with a damage beyond allowable damage defined above. Example of
acceptable airplane operation: before xx flight cycles.

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DAMAGE CATEGORIES
Figure 3

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Figure 4

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