TM 1-1500-204-23-11
Table 7-1.
General Description of Different Repair Types -- Continued
Constraints and
Description
Application
Type of Repair
Limitations
Structural repair; external. Moderately thick to heavy
Repair parts must be
Riveted/Bolted Sheet
carbon laminates.
compatible with parent
Metal
Used primarily when
structure (stiffness,
conditions prohibit
expansion coeficient,
bonding. Circular or
etc.). Fastener size
rectangular patch and/or
and pitch are important
reinforcing angles cut
considerations. Drilled
from metal sheet stock
holes in structure may
or standard structural
create unacceptable
shapes (aluminum or
stress concentrations.
titanium). Parts may be
Riveting not feasible for
formed to it contours of
thin laminates.
parent structure. Repair
installed with mechanical
fasteners. A sealant
which is not sensitive to
contamination is desirable
between the patch surface
to provide additional shear
strength and to reduce
bearing loads at the rivets.
Bolted Metal Plate
Thick metal patch
Heavy carbon structures.
Very limited application
(titanium or stainless
to helicopter structures.
steel) cut from plate
Restricted to heavy carbon
stock and joined to the
structures capable of
damaged structure with
accepting drilled holes and
bolts. Sealant applied
high-stress concentrations
between repair plates and
created by the installation
surface of the part.
of mechanical fasteners.
Two-sided access is
usually required.
Damaged core material
Honeycomb sandwich
Limited to no larger than
Sandwich Core Repair
removed. Plug cut from
panels using aluminum or
6 inches in diameter.
(Foam Plug)
structural foam or a
Nomex honeycomb.
Two-sided access
foam-in-place liquid
required for through
polyurethane foam.
damage.
Foam cured and face
sheet repaired with one
of the laminate repair
procedures.
7-5
