CESSNA AIRCRAFT
COMPANY
SINGLE ENGINE
STRUCTURAL REPA
IR MANUAL
DAMAGE INVESTIGATION AND CLASSIFICATION
1. General
A. For the purposes of this manual, damage is considered to be a deviation from the original
configuration of a structural part that compromises its structural integrity by significantly reducing its
strength, sig
nificantly decreasing its resistance to fatigue, significantly increasing its susceptibility to
corrosion, significantly altering its flutter characteristics, or adversely affecting the flight characteristics
of the airplane. This can include - but is not limited to - scratches, dents, dings, gouges, cracks,
drill starts
, double drilled holes, plastic deformation, reduction in cross-sectional areas, changes in
component center-of-gravity, missing or inadequate fasteners, corrosion, dissimilar metal contact,
work hardening, temper change due to excessive heat, and so forth.
B. Use good judg
ment in determining the type of significant change to flat stock structural material. The
terms, dent, crease, abrasion, gouge, nick, scratch, crack and corrosion, referred to elsewhere in the
manual, are defined below as a guide for this determination, particularly with respect to the external
skin of the a
irplane:
(1) Dent - A dent is normally a damaged area which is depressed with respect to its normal contour.
There is no cross sectional area change in the material. Area boundaries are smooth. Its form
is generall
y the result of contact with a relatively smoothly contoured object.
NOTE: A dent-like form of damage to skin may be the result of the peening action of a
smoothly co
ntoured object contacting it. If the inner surface of skin shows no contour
change, consider that such damage results in a local cross sectional area change.
(2) Crease - A da
maged area which is depressed or folded back upon itself in such a manner that its
boundaries are sharp or well defined lines or ridges. Consider it to be the equivalent of a crack.
(3) Abrasion - An abrasion is a damaged area of any size which results in a cross sectional area
change due
to scuffing, rubbing, scraping or other surface erosion. It is usually rough and
irregular.
(4) Gouge - A gouge is a damaged area of any size, which results in a cross sectional area change.
It is usual
ly caused by contact with a relatively sharp object which produces a continuous, sharp
or smooth channel-like groove in the material.
(5) Nick - A nick is a local gouge with sharp edges. Consider a series of nicks, in a line pattern to
be the equi
valent of a gouge.
(6) Scratch - A scratch is a line of damage of any depth in the material and results in a cross sectional
area change. It is usually caused by contact with a very sharp object.
(7) Crack - A cr
ack is a partial fracture or complete break in the material with the most significant
cross sectional area change. In appearance, it is usually an irregular line and is normally the
result of fatigue failure.
(8) Corrosion
- Corrosion, due to a complex electrochemical action, is a damaged area of any size
and depth which results in a cross sectional area change. Depth of such pitting damage must
be determined by a cleanup operation. Damage of this type may occur on surfaces of structural
elements
. Refer to Corrosion and Corrosion Control, Section 51-11-00.
C. Use good sense and proper visual measurement in the determination of significant cross sectional
area changes of both depth and length of any type (or combinations) of damage mentioned above.
2. Damage Investigation
A. After a thorough cleaning of the damaged area, all structural parts should be carefully examined
to determ
ine the extent of damage. Frequently, the force causing the initial damage is transmitted
from one member to the next, causing strains and distortions. Abnormal stresses incurred by shock
or impact forces on a rib, bulkhead, or similar structure, may be transmitted to the extremity of the
structur
al member, resulting in secondary damage, such as sheared or stretched rivets, elongated bolt
holes, or canned skins or bulkheads. Points of attachment should be examined carefully for distortion
and security of fastenings in the primary and secondary damaged areas at locations beyond the local
51-10-00 Page 1
© Cessna Aircraft Company Jun 1/2005
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