TM 1-1520-240-BD
Figure 2-8. Measuring Damage In Floors and Decks
(b) Honeycomb Sandwich Structures.
Refer to Figure 2-9 for the measurement of "WL" and
"D." If a projectile hits a sandwich panel at an angle, the
damages in the two skins may be off-set and of different
sizes. Measure the damage on the side with the largest
damage (usually the exit side), and make sure that the
measurement includes the damaged area on the other
side. "WL" is the largest dimension across the damage
(both sides), regardless of direction, and must include all
radiated cracks. "D" is the distance between damages.
Take and record the measurements as previously
described.
d.
General Damage Units.
(1) The allowable damage limits corresponding to
the damage measurements of paragraph 2-2 are
designated for a given condition as follows:
CD'
= Allowable
depth
of
cap/longeron
damage.
DL'
= Allowable length (width) of cap/longeron
damage.
A'
= Allowable area of damage.
D'
= Minimum allowable distance between
damages.
WL'
= Allowable
largest
dimension
across
web/panel damage.
N
= Minimum Damage Factor.
(2) Allowable damage limits are associated with
the conditions of the primary structural elements as
described below. A damage limit for a given condition is
a measure of the amount of damage that a structural
member can sustain and still support the loads
associated with the given condition. These limits were
developed from the aircraft manufacturer's original
engineering design calculations.
2-12
