a. The body is constructed of aluminum alloys that have been heat-treated to obtain high strength.
Welding cannot be used to make body repairs. Heat generated in welding will reverse the heat treatment
process and cause a great reduction in strength of material.
b. The hood and engine access cover are made of fiberglass (sheet molding compound). Cracks, splits, or
holes may be repaired with a glass reinforced plastic laminate repair kit, MIL-R-19907C. (Refer to para. 33-9.)
c. Solid 3/16-m. diameter aluminum rivets are the primary method of joining body components. The rivet
is inserted into a hole through two pieces of metal, and a second head is formed by manual or pneumatic
impacting or by squeezing the rivet. A bucking bar is used to back up the rivet to form the rivet head. When
making repairs, use blind rivets of the same size or oversize diameter with the appropriate grip length. Rivets
3/16-in. in diameter are identified in appendix F, table F-l. For other rivets that may be needed, the NSN for
the rivet can be determined by cross-referencing the rivet part number to an NSN. To determine the proper
rivet part number, the following part number breakdown is provided:
MS20600 -basic MS number
AD - indicates aluminum
6 - indicates rivet sleeve diameter in Y3Zin. increments (6 x l/32 = 6/32 = 3/16-in.)
W - indicates serrated stem rivet
2 - indicates maximum grip length in 1/16-in. increments (2 x 1/16 = 2/16 = Y8-in.)
d. Blind structural aluminum rivets of 3/16-in. diameter are used in applications where there is access
from only one side of the part. Blind rivets are installed using a tool that pulls on the rivet stem causing a
bulbed head to form on the back side of the part. Fastening is complete when stem breaks off. High strength
is obtained in blind structural rivets by mechanically locking the remaining stem inside rivet body.
e. Steel pull-type lockbolt fasteners of 3/16-in. and l/Pin. diameter are used where tension or high-shear
loads exist. Lockbolts are two-piece unthreaded fasteners. One part is a high-strength, steel-headed, bolt-like
part with serrations on its shank. The mating part is a collar which is swaged over the sex-rations causing the
fastener to be locked in place.
f. To facilitate repairs to the body, it is acceptable to replace lockbolts and rivets with 3/16-in. AN3 series
and Y4in. AN4 series bolts. Do not replace lockbolts with rivets. Standard threaded fasteners should not be
used as these will quickly wear the aluminum structure. Bolt lengths should be chosen so that the cylindrical
portion of the bolt is bearing on all members being joined. AN3 and AN4 series bolts are identified in
appendix F, table F-3. Tighten all bolts to 70-75 lb-in. (8-8.5 N-m).
g. Fatigue strength of riveted joints and seams is increased by applying one part epoxy adhesive. This
adhesive requires special material storage and metal preparation along with a low-temperature heat cycle for
curing. Because of its impracticality in field repairs, epoxy adhesive will not be used. Where possible, extra
rivets and thicker metal gauges should be used instead of adhesives. When making repairs, note epoxy
applications. Parts may be difficult to separate, even after rivets are removed.
a. General. The damaged area should be thoroughly cleaned and inspected to determine cause and extent
of damage. Body parts should be inspected for holes, cracks, dents, distortion, or breaks. Fasteners should be
inspected for breaks, stretching, looseness, cocked heads, or hole elongation. Seams, flanges, and joints should
be inspected for straightness or local deformation as an indication that fasteners may have been stretched or
holes elongated. It is possible for this to happen and fasteners still appear to be tight in their holes. In
addition, make a thorough inspection of adjacent areas to determine if high loads have been transmitted from
the damaged area to other areas. This can result in secondary damage in the form of distorted panels or
seams, loosened or sheared fasteners, elongated fastener holes, and cracks.
b. Classification. ARer extent of damage has been determined, affected parts should be classified into
one of the following categories:
l Negligible damage
l Damage repairable by patching
l Damage repairable by insertion
l Damage necessitating replacement of parts