members prevent using
pressure must be used.
INTERNAL STRUCTURE REPAIR
Contour (shape), rigidity, and strength for the semimonocoque
fuselage are derived, for the most part, from its internal structural
members. From time to time these members need repairs. This section
describes some typical repairs for internal structural members.
However, the appropriate technical manual for the particular aircraft
must be consulted. What may be a simple repair on one aircraft can
require special techniques and tools on another. The paragraphs that
follow discuss repairs for stringers and longerons, spars and ribs,
formers and bulkheads, and leading and trailing edges.
Made from extruded or rolled metal alloy, stringers are generally in
the form of C-channel, angle, or hat-shaped sections.
shows one method of repairing a damaged stringer by patching.
repair elements consist of reinforcement and filler splices and
The reinforcement splice must extend a minimum of four
rivets plus edge distance on each side of the damaged area.
reinforcement splice's cross-sectional area and strength must be
equal to or greater than the stringer's. The damage must be trimmed
to a smooth contour with corner radii, and a filler patch of proper
thickness and matching shape must be prepared. If possible, maintain
the original rivet pattern in the repair. This can be done by having
both ends of the trimmed damage lie midway between two rivets.
the filler splice 1/32 inch shorter in length than the trimmed out
section. This allows a 1/64 inch clearance between each end of the
filler splice and the stub ends of the stringer.
prevents stress from developing through contact between the filler
splice and the stub ends.