(3) Marking damage. Mark the
damaged structure using grease pencil or
paint.
Use the labeling scheme shown in
Figure 1-3.
CAUTION
Use of lead pencil in some areas
will cause corrosion.
(a) Use a bright color to
outline each area of damage as it is
located and recorded on the DA Form
2404.
Attempt to make the outline
visible from all angles.
(b) Draw arrows on inside skin
panels, webs, and bulkheads to point
toward areas of damage that are hidden.
4-7.
DAMAGE MEASUREMENT. If the
assessment indicates that the damage
should be repaired by BDAR or standard
procedures, no damage measurement is
necessary. Damage measurement is
required to determine if structural
repair (other than cleanup) can be
deferred, or if self-recovery of the
damaged aircraft is feasible. Damage
measurement may also be required if a
BDAR repair does not restore original
strength.
Begin damage measurement
with the largest damage.
a. Damage Measurement of Typical
Sections.
(1) The parameters involved in
measuring damage to typical sections
are shown in Figure 4-3. The per-
tinent values are:
CD
= Depth of damage.
CL = Length (width) of damage.
A = CL x CD =
area of damage.
D =
Distance between damages.
In Figure 4-4, the length of the flat-
tened cross section of the angle is:
a+b
CD is the depth of the damage into the
flattened cross section. The length of
the remaining effective cross section
is still capable of supporting a load.
All dimensions are in inches.
CS = (a+b)-CD
(2) When measuring damage, use the
following procedure:
(a) Clean all damaged areas
thoroughly. Use brushes and swabs to
remove dirt and film from small crevices
where damage may be present.
(b) Smooth all jagged and rough
edges and be sure to cut out all radiated
cracks. Use largest corner radii possible
in the cut-outs; avoid sharp corners.
(c) Measure damage after
smoothing, or if measuring before
smoothing, make allowance for the
material which must be removed during
smoothing.
See paragraph (d) below.
(d) Use a steel rule graduated
in tenths of an inch and measure each
damage dimension to the next higher tenth.
(e) Include the size of the
hole when measuring damage that extends
into a fastener hole or lightening hole.
(f) Record on DA Form 2404.
b.
Webs, Panels, and Skins.
(1) Refer to Figures 4-5 and 4-6
for the measurements of “WL” and “D.”
"WL" is the largest dimension across the
damage, regardless of direction, and
must include all radiated cracks.
"D"
is the distance between damages. Take
and record measurements as described in
paragraph 4-7.a(2).
4-7
TM 55-1520-228-BD
AIRFRAME
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