SRM A320.pdf

Structural Repair Manual a320

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SRMA320

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STRUCTURAL REPAIR MANUAL Introduction
Manufacturers publish Structural Repair Manual (SRM) to pr ovide data for the
structural maintenance of commercial airplanes which have sustained structur-
al damage.
The Manuals are approved by the Aircraft Manufacturers Avia tion 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:
Smaterial identification for structure subject to field rep air
Stypical repairs general applicable to structural componen ts of the airplane
that are most likely to be damaged
Sinformatieu relative to material substitution
Sfastener installation
Sairplane 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 t anks.
Either it has not been found practicable to design a typical r epair, or service
experience has not yet indicated a requirement. In some inst ances, an ade-
quate repair design will require evaluation by the Manufact urer. Consider the
following when typical repairs are not found:
SAccomplish a repair in accordance with the general repair pr actices and pro
cedures provided in chapter 51 -- Structures General -- of th e manual
SPreparing a specific repair design for the damage not covere d
SReplacing of the damaged part
As service experience indicates a requirement, the manual w ill be revised to
include actual, specific repairs to both primary and second ary structures. To
ensure consistent handling of these revisions, index categ ories have been es-
tablished for all known types of repairs, although some info rmation 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 inform ation included in
the manual be supplemented as required by direct liaison wit h the repair as-
signed Manufacturer Customer Support Representative. Forordering structural
repair parts, see Spare Parts Identification, located in th e 00-- Introduction Part.
The manual will serve as a medium through which the airplane o perators 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 0 0 -- 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 materi al presented in
this manual is divided into seven chapters.
Chapter numbers
SChaptcr 51 Structures -- General
SChapter 52 Doors
SChapter 53 Fuselage
SChapter 54 Nacelles/ Pylons
SChapter 55 Stabilizers
SChapter 56 Windows
SChapter 57 Wmgs
SECTION NUMBERING Chapte numbers are sub-- divided into section numbers. In so me instances
specific section number allocations are made to cater for st ructural variations
between model differences.
CHAPTER 51 Chapte 51 deals with those subjects which are general in natu re to the entire
structure of the airplane. It is arranged to allow maximum ut ilization of common
data. The assigned section numbers are as follows:
Chapter Section
Number Nomenclature
S51 --00 General
S51 --10 Investigation, Clean up of Damage and Aerodynamic Smooth
ness
S51 --20 Processes and Procedures
S51 --30 Materials
S51 --40 Fasteners
S51 --50 Support of Airplane for Reparand Symmetry Check
S51 --60 Control Surface Balancing
S51 --70 Repairs

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PAGE BLOCK ALLOCATION In Chapters 52 thru 57 each subject represents a structural e lement. All of the-
data concerning that element are covered within that subjec t. 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 descr iption 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 bloc k 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 a re 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 Manu als 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 ou tside label, to
chec@ the effectivity of the hole Manual by a document list. P ages 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 a s same as, the
date of the revision cycle. On each individual page the revis ed area is indicated
by a revision bar on the left margin. Those pages which have no t 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 ne cessary to alert
the customer of configuration differences and to provide te mporary instructions
prior to the next scheduled revision. Temporary revision wi ll also be issued as a
result of a customer request for planned incorporation of a s ervice bulletin.
Each temporary revision will be incorporated into the manua l within 90 days-
from date of issuance, except from those temporary revision s, issued as a re-
sult ol planned incorporation of a service bulletin. these s ervice bulletin tempo-
rary revisions will remain active until the Manufacturer ha s been advised by the
customer that incorporation of the service bulletin into th e airplane has been
completed. Each te nporary revision will apply to one subjec t only and will be
keyed within this manuai, so that the temporary revision wil l be filed adjacent to
the affected pages.
Temporary revisions will not be revised if changes are requi red to an existing-
temporary revision, the temporary revision will be reissue d.

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AIRPLANE EFFECTIVITY DESIGNATIONS This non--customized Structural Repair Manual contains in formation applicable-
to the airplanes, listed in the Airplane Effectivity Alloca tion List, located in the
Introduction part of the SRM. They relate current operator c ode, airplane model
series designation, manufacturers serial number (MSN), an d customer abbrevi-
ation. Pages that have no effectivity designation are appli cable to all airplanes.
Effectivity designations are used to define configuration differences between
airplanes. Effectivity designation will appear in one of th e following forms:
Use of the customer abbreviation code, such as AFR or DLH, ind icates that the
information is applicable to all airplanes of that customer .
Use of the effectivities Manufacturers Serial Number, show n as (B) Before or
(A) After modification.
All modifications are shown in the Modification / Service Bu lletin List.
Use of a generic designator which includes a readily identif iable feature.
For example:
for airplanes with optional forward airstairs, or which is r elated to model, like:
A320
Airplane allocation list Airbus A320
Containing information about:
SAircrsft Manufacturer Serial Number
SAircraft Type
SVersion Number
SCustomer
SCustomer Abbreviation
SRegistration Number

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NUMBERING SYSTEM Each subject, within the SRM, is identified using a three--e lement numbering
system Chapter/Section and Sub--section.
The first element designates the chapter which is assigned b y the ATA spec.
100.
The second element designates the section within the chapte r. 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) withi n 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 Ch apter 51 will be
assigned sequentially.
In Chapter 52 thru 57 a consistent numbering system will be ap plied.
The subject numbers that have been assigned are shown below.Each section-
will only use the subject numbers applicable to the structur al elements that are-
described in the section.
This will mean that the subject numbers are not necessarily s equential, 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 o f 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 us e of the Structural
Repair Manual:
Check for allowable damage.
From the Table of Contents of the manual find the chapter to wh ich the dam-
aged part belongs.
Turn to the Table of Contents of the selected chapter, find su bject number of
Allowable Damage.
Damage Classification-- General, to determine if the damag e is allowable. Iden-
tify the damaged part. If it is found that the damage exceeds t he allowable, the
part must be identified in order to determine the applicable repair figure.
From the Table of Contents of that chapter, find subject numb er 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 tabul ation sheet of the
identification figure. Find the applicable repair figure n umber. Apply repair figure
to actual damage. Turn to he repair figure mentioned above, r ead notes and
instructions carefully, and perform the repair according t o the figure.
Use the Table of Contents, at the beginning of each chapter, a s a numerical
index to locate a specific subject within a specific section of a chapter. Read all
the text material, supporting figures and references withi n a specific subject
Chapter 51 lists the sections and subsections generally app licable (except
when limited) to the entire airplane.
Chapters 52,53, 54, 55, 56, and 57 list such sections and subj ects which are
applicable respectively to those specific chapters only.
The use of the table of contents to locate specific repairs, s upplements 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 Manua l, 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 mate rial which-
causes a cross--sectional area change. A sharp object usual ly causes it.
Gouge
A gouge is a damage area of any size which results in a cross--s ectional area-
change It is usually caused by contact with a relatively shar p 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 scr atches, nicks,
chips, burrs or gouges etc. is shown. You must prepare the dam age 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 materia l.
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, are a edges are smoott
Nick
A smal decrease of material due to a knock at the edge of a membe r or skin.
Distortion
Any twisting, bending or permanent strain which results in m isalignment or-
change of shape. May be caused by impact from a foreign object , but usually
esults from vibration or movement of adjacent attached comp onents. f his
group includes bending, buckling, deformation, imbalance , misalignment,
pinching and twisting.
Corrosion
The destruction of metal by chemical or electro--chemical e ffect.
Abrasion
An abrasion is a damage area of all sizes which causes change i n 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 a dhesive failure.
Delamination
Delamination is when the separation of plies occurs in a mult i--laminate materi-
al. This can be caused by the material being hit -- impact, or w hen there is a
resin failure for any other reason.
Fretting
Surface damage at the interface between elements of the join ts resulting from-
very small angular or linear movements. Evidence of frettin g is usually the pro-
duction of fine black powder staining.

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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 delaminat ion or separation
of the core and face along the bond line. (The bond line is the t hin 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 assemb lies than for
conventional structures, A honeycomb structure can suffer extensive damage-
without any observable indication. Sonic vibration, liqui d leakage, internal
condensation, or a misstep in manufacture or repair can caus e or result in var-
ied amounts of delamination.
The metallic ring test is the simplest way to inspect for dela mination damage.
When a coins lightly bounced against a solid structure, a cle ar 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 insp ection.
Occasionally, he delaminated skin will ”oil can” away from t he core, making
visual or thumb pressure detection possible. Punctures, de nts, scratches,
cracks, or other such damage may be inspected by conventional methods.
Scratches should be given special attention since, with suc h thin material as-
that used in the metal bonded honeycomb, the scratch may actu ally be a crack.
A caustic soda solution can be used for testing scratches on a luminum surface-
panels. If the scratch area turns black after the applicatio n of a small amount of
the solution, the scratch has penetrated through the clad su rface. Caustic soda
solutions are highly corrosive and must be handled with extr eme care.Through-
ly neutralize the area after application of the solution.
Two additional instruments used in damage inspection of bon ded panels are
the panel inspection analyzer and the borescope.
Damage Evaluation
After inspections on metal bonded honeycomb structures arecompleted, any-
damage found must be evaluated to determine the type of repai r needed to-
make the structure serviceable. Damage to aluminum honeycomb structures
can vary from minor dents or scratches to total panel destruc tion. Damage
evaluation charts for honey--comb structures can be found i n the applicable
section of the structural repair manual for the specific air craft. The charts
specfy types of damage, allowable damage, damage requiringrepair, and fig-
ure numbers that illustrate similar repairs for each type of damage. Once the
type of repair is determined, procedures outlined in the str uctural 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 resul ts from many causes,
which can be generally categorized into four main groups:
Smechanical action
Schemical or electrochemical reaction
Sthermal action or cycling
Sinherent metallurgical characteristics
Examination of damage
Examine the type and extent of the damage, to determine the da mage catego-
ry.
Remove all unwanted material from the surface of the damagedcomponent,
cut out all broken, bent, heated or badly damaged areas of the component, re-
move all loose rivets. In all forms of damage, particularly w here shock has
been sustained, secondary damage is likely to exist. Theref ore, a close ex-
amination of the structure surrounding the initial damage m ust be made. Dam-
age caused by transmission of force may be located some dista nce from the
impact, resulting in structure deformation, drawn rivets o r bolt holes.
If misalignment or twisting of the airplane structure is sus pected, 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 inser ting or attaching
a reinforcing piece, These specific repairs are to be found i n each chapter of
this manual.
Non repairable damage
Non--repairable damage is defined as damage to structural c omponents, 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 Componen ts’.
After cleaning and investigating the damage and surroundin g area, the damage
must be classified into one of the following categories, als o taking into account
the location of the damage.
Repairable damage
The damage must be classified either as ‘Allowable Damage’ o r 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 componen t. Allowable damage
values specified in each chapter are by definition establis hed in such a way
that damage within that limit does not require a structural r epair during the de-
sign life goal of the airplane, for example 48000 flight cycl es. 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 prot ective treatment is
generally required.
Clean the area before examination in order to see if the damag e is within allow-
able limits.
For example, in the case of corrosion, you first remove the co rrosion and then
examine the extent of the damage. Compare the extent of the da mage with the
allowable damage limits. Operating limits are defined as th e 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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