TM 1-1500-204-23-11
b. Repairable Damage. This is deined not only
other chemicals found in the maintenance environment
(cleaners, solvents, jet fuel, hydraulic luid, engine oil,
as damage requiring repair, but also damage that is
etc.) show no effect due to exposure.
within the repair capability of the activity at which
the repair is to be performed. The location of
damage, complexity of the repair procedure, repair
(1) Fluid Intrusion. This type of damage
weight limitations, availability of repair equipment and
occurs with honeycomb sandwich assemblies when
materials, repair time/cost, spare part availability, etc.,
a leak path develops which allows luid to enter the
are all factors in deciding whether a part is beyond the
honeycomb core cells. This can be detrimental to
capability of maintenance (BCM) at that activity. Parts
weight and balance critical to rotor blades or light
that are BCM must be forwarded to the next higher
control surfaces, as well as causing material degra-
maintenance activity (NHMA). Refer to the system
dation to both metallic and non-metallic honeycomb
speciic manual for guidance on repairability due to
core. Fluid intrusion is of major concern in performing
damage location and to provide speciic repair weight
elevated temperature cures during bonded repairs.
limits.
Chapter 7 covers luid removal and drying of core
prior to repair.
c. Non-Repairable Damage. Parts determined to
be non-repairable must be forwarded to depot level
(2) Corrosion. Metallic structure, particularly
for disposition.
aluminum, may experience galvanic corrosion with
carbon iber structure. This includes ittings, fasten-
5-5. DAMAGE ASSESSMENT METHODOLOGY. F-
ers, metallic core, and lightning mesh. Direct physical
contact is not required, just an electrical path between
our steps are involved in assessing damage: (1)
the aluminum and carbon iber. Aluminum must
Locating damage, (2) characterizing the damage and
be electrically isolated from the composite laminate.
determining its extent, (3) zoning the damage on the
Chapter 6 details isolation procedures. Indications of
part being repaired and (4) re-evaluation of the dam-
corrosion include scale, cracking, pitting, material loss
aged area after damage removal.
or other corrosion by-products. TM 1-1500-344-23
provides additional information on corrosion.
a. Locate the Damage. This is usually performed
by visual inspection. However, caution must be
5-4. DAMAGE CATEGORIES. Once the extent of
exercised as non-visible subsurface damage may
the damage is determined and prior to actually begin-
exist beneath impact areas and areas suspected
ning a repair, damage should be classiied as (1) neg-
of having been impacted. Areas impacted (with
ligible, (2) repairable or (3) non-repairable. This clas-
or without visual indication on the part surface) or
siication requires experienced judgment and knowl-
suspected of having been impacted must be further
edge of the strength and functional requirements of
evaluated for delaminations and matrix cracks. Use
the structure. Technical data that provides a zoning
the nondestructive inspection (NDI) methods listed in
system of the structure should be available in the
paragraph 5-2 as well as the system speciic technical
system speciic technical manual. When speciic dam-
manual.
age classiication data is not available or the data is
questionable, additional technical data or engineering
b. Characterize the Damage. Once the damage
must be consulted. The decision concerning disposi-
has been located, the extent of the damage must
tion must be made with the speciic requirements of
be determined and the damage characterized. The
the aircraft or system in mind, as well as the partic-
depth of delamination and the presence of skin to
ular parts involved, the limitations that can be placed
core or skin to substructure disbonds (if applicable)
on the repaired aircraft, the degree of urgency, local
should be determined to characterize the detected
repair capabilities, availability of spare parts, and any
damage. Determining the extent of damage and
other circumstances impacting the situation. Three
characterizing the damage is an important part of the
types of damage are categorized below:
damage assessment process, as it will have a direct
bearing on the repair procedures to be employed.
a. Negligible Damage. Damage which, because
of its size, nature and location that does not adversely
c. Zone in the Damages. After the damage has
affect the structural integrity of the part is deined as
been characterized and the extent determined, the
negligible. It may be allowed to exist without repair,
repair zone in which the damage is located is deter-
or may only require a cosmetic repair to be performed
mined using the system speciic technical manual.
to prevent further damage from occurring (such as
Overlap of damage from one repair zone to another
further stripping of outer ply material). Refer to the
requires the damage limits for the worst case zone
system speciic technical manual for further guidance
be used. If the damage limits for the repair zone in
on what constitutes negligible damage.
which the damage is located are exceeded, the part
must be forwarded to the NHMA for repair. If the
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