(a) Structural movement which
might change the location or alignment
of a component.
Controls and drive-
shafts will be particularly critical.
(b) Structural damage which
could affect the security of wire
bundles and fluid lines, causing them to
vibrate, chafe, and fatigue during
flight.
(c) Damaged structure which
might interfere with the free travel or
movement of a system component during
operation.
(3) If the assessor determines
that structural damage will or might
create any of the above conditions,
TM 55-1520-228-BD
AIRFRAME
classify the structure as failed even if
the physical damage is within allowable
limits.
4-14. BDAR REPAIR PROCEDURE INDEX.
PARA.
Skin/Stiffener Damage. . . . . 4-16
Cap, Skin, Web, Doubler
Damage. . . . . . . . . . . 4-17
Cap or Longeron Damage . . . . 4-18
Frame, Bulkhead, Skin and
Stringer Damage. . . . . . . 4-19
Honeycomb Core Floor or
Panel Damage . . . . . . . . 4-20
Windshield/Window Damage . . . 4-21
Tail Boom Skin Damage . . . . 4-22
Section II. EXPEDIENT STRUCTURAL REPAIRS
4-15. GENERAL.
a.
Many of these expedient repairs
will restore the airframe to condition
1.
Inspection for damage growth will
generally be required after every
flight, and damage should be repaired
as soon as practical by standard main-
tenance procedures.
b.
Multiple Damage. Special atten-
tion should be given to structural com-
ponents which have sustained damage in
multiple locations.
It is essential
that damage to an individual structural
item not be considered by itself. Suit-
able repair will often depend on the
condition of the adjacent structure. In
some cases, undamaged adjacent structure
may satisfactorily take the load of the
damaged item.
Since time is an over-
riding consideration on the battlefield,
BDAR airframe repairs are usually per-
formed on the outside of the aircraft to
save the time required to gain access to
the interior.
If, however, access to the
interior damaged structure is already
available, inside BDAR repairs may be
made.
c. Fasteners. BDAR can be carried
out using any form of fastening device,
which is available at the time (e.g.,
nuts, bolts, rivets, etc.), as long as
strength requirements are met.
Use
accepted practices regarding fastener
edge distance and spacing.
The faste-
ners used in a single repair should be
of the same type.
d.
Metal Selection.
All repair
patches should be manufactured from
material of the same or similar specifi-
cation as the damaged area but at least
one gauge or 10 percent thicker. When
required repair materials are una-
vailable, substitutions can often be
made to produce a desired strength.
Table 4-8 cross lists various types of
metal and instructions on how to substi-
tute one type of metal for another.
Alternate repair materials can be
obtained from scrapped aircraft.
It is
also permissible to fabricate from
thinner gauge material and use multiple
thickness.
4-49
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