Bell OH-58A Technical Manual page 101

3. Install a minimum of six rivets in
each row on each damaged end of major
structure such as caps, extrusions, etc.
Remove existing rivets and back drill
holes in the patch plate if the area is
accessible. If back drilling is not
practical, it may be possible to
interpitch new rivets between existing
rivets. Use same size rivets or
oversize rivets if necessary.
4. Install two rows of rivets around
patch plate in webs and skins using
same size as adjacent rivets in webs
and skin.
5. Record BDAR action taken. When
mission is complete, as soon as
practical, repair the equipment/system
using standard maintenance procedures.
4-18. CAP OR LONGERON DAMAGE.
GENERAL INFORMATION: Nondeferrable cap
or longeron damage may be substantial,
combined with skin damage.
generally be necessary to repair the cap
or longeron first and then the skin. It
may not be necessary to repair the skin
for structural reasons, but generally
skin repair is recommended to make a
watertight repair.
LIMITATIONS: None - Condition 1. Inspect
after every flight for damage growth.
PERSONNEL/TIME REQUIRED:
2 Soldiers
2 Hours
MATERIALS/TOOLS REQUIRED:
Longeron or Cap - Sections used in
outside repairs should be angular or
channel shaped.
new cap or longeron should be at least
that of the damaged cap or longeron.
Refer to Table 4-8 for substitute
materials to use on repair if a
longeron or cap section is not
available.
Skin Patch
Blind Rivets (item 41, Appx C)
It will
The strength of the
PROCEDURAL STEPS:
1. Remove sections of the aircraft skin
containing the damage.
or longeron, but cut off ragged ends,
Figure 4-20.
2. Make a patch plate. Plate should be
as strong or stronger than original
skin. Overlap the hole for at least 2
rows of rivets.
3.
Cut a piece of substitute cap or
longeron to extend at least six faste-
ners on all rows fore and aft of damaged
section. Sometimes a single substitute
cap or longeron can be extended to pro-
vide support for several damages.
is better than individual repairs, as it
will stiffen the airframe.
4. In the areas where the substitute
cap or longeron will overlap on the
damaged cap or longeron sections, remove
rivets which attach the damaged cap or
longeron to skin. Back drill rivet
holes on the substitute cap or longeron
to match existing holes on the damage
cap or longeron.
5. Rivet the substitute cap or longeron
in place using the same size or larger
rivets as those removed in step 4.
6. Rivet patch plate over hole using
blind rivets. Use same size rivets as
existing rivets.
NOTE
Stiffener can be placed on out-
side; however, this configuration
is nonpreferred.
7. Record BDAR action taken. When
mission is complete, as soon as
practical, repair the equipment/system
using standard maintenance procedures.
TM 55-1520-228-BD
AIRFRAME
Do not cut cap
This
4-57