TM 55-1520-228-BD
AIRFRAME
4-19. FRAME, BULKHEAD, SKIN, AND
STRINGER DAMAGE.
GENERAL INFORMATION: A damaged flange
on a bulkhead or frame could be repaired from
the outside in the same way as is a cap or
longeron. However, it is not desirable to have a
section on the outside of the aircraft sticking out
normal to the airstream. Frame flanges are
therefore repaired by applying a strap over the
damage. If the damage to a highly loaded
bulkhead is severe, then treat it like a cap and let
the section stick out in the airstream.
OPTION 1: Patch Plate Repair for Small
Damage.
LIMITATIONS: None – Condition 1.
Inspect after every flight.
PERSONNEL/TIME REQUIRED:
2 Soldiers
2 Hours
MATERIALS/TOOLS REQUIRED:
Repair Strap
Cherry Rivets (item 41, Appx C)
Tape or Skin Patch
PROCEDURAL STEPS:
1. Stop drill all cracks, Figure 4-21.
2. Cover the damage with tape. Be sure to
cover the ends of all cracks.
3. Fabricate a repair strap using thick sheet
metal. The sheet metal should be 2 X thickness
of the original flange material, skin, and stringer.
The strap should be wide enough to cover
damaged area and to allow at least two rows of
rivets on the skin, and a minimum of six rivets in
the undamage portion of damaged stringers. The
strap should be long enough to overlap both
ends of the damaged bulkhead or frame flange
by six rivets on each end. In the areas where
the repair strap will overlap on the damaged
bulkhead flange and stringer, remove rivets and
back drill if the area is accessible. If back drilling
is not feasible, interpitch new rivets between
existing rivets.
4. Rivet the repair strap to the bulkhead or
frame flange and stringer using the same size or
larger rivets. Rivet the strap to the skin using two
rows of rivets around the perimeter using the
same size rivets as in adjacent skin-flange
structure.
5. Record BDAR action taken. When mission is
complete, as soon as practical, repair the
equipment/system using standard maintenance
procedures.
OPTION 2: Combination Repair for Major
Frame or Bulkhead Damage.
LIMITATIONS: None — Condition 1.
Inspect after every flight.
PERSONNEL/TIME REQUIRED:
2 Soldiers
3 Hours
MATERIALS/TOOLS REQUIRED:
Filler Patch
Repair Doubler
Skin Patch
Cherry Rivets (item 41, Appx C)
PROCEDURAL STEPS:
1. Remove sections of the skin and frame or
bulkhead containing the damage. Smooth and
round the cutouts, Figure 4-22.
2. Cut and fit repair doubler for frame or
bulkhead. Cut skin patch allowing overlap for at
least two rows of rivets. Repair patch and
doubler should be the same material and one
gauge thicker than original material.
4-59
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