body frames, belt frames, and similar names.
Their purpose is to
carry concentrated stress loads.
Bulkhead damages are classified in the same manner as other damages.
Specifications for each type of damage are given in the applicable
manual for the aircraft.
Bulkheads are identified with station
numbers for ease in locating the damage area.
The paragraphs that
follow discuss repair categories and sheet metal stock strength.
Repair Categories.
Repairs to these members are generally placed
in one of two categories: one-third or less of the cross-sectional
area damaged or more than one-third of the cross-sectional area
damaged.
A patch plate, reinforcing angle, or both may be used if
one-third or less of the cross-sectional area is damaged.
First,
clean out (trim) the damage and consult the applicable technical
manual for details on how many rivets to use to establish the patch
plate size. For the length of the break, use the depth of the cutout
area plus the length of the flange.
If more than one-third of the cross-sectional area is damaged,
remove the entire section and make a splice repair.
Consult the
applicable technical manual for details on the splice repair and the
number of rivets required.
When removing the damaged section, be
careful not to damage electric lines, plumbing, instruments, and so
forth. Use a hand or rotary file, snips, or a drill to remove larger
damages. To remove a complete section, use a hacksaw, key hole saw,
drill, or snips.
Sheet Stock Strength. Most repairs to bulkheads are made from flat
sheet stock if repair parts are not available. When fabricating the
repair from flat sheet, remember that the substitute material must
have
cross-sectional
tensile,
compressive,
shear,
and
bearing
strength equal to the original material.
Never substitute material
that is thinner or has a cross-sectional area less than the original
material. Curved repair parts made from flat sheet stock must be in
an annealed condition before forming and then must be heat-treated
before installation.
LEADING EDGE REPAIR
Usually several structural parts are involved in leading
edge damages. Flying object damage generally involves the nose
skin, nose ribs, stringers, and possibly the cap strip.
Damage involving all of these members will require installing
an access door to make the repair possible. First, the
damaged area must be removed and repair procedures established. Such
a repair will need insertions and splice pieces, and it may require
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