Cessna 172 Maintenance Manual page 126

B. Repairable damage: Dents or dings deeper and/or larger than specified above must be repaired. Skin
tears, cracks or penetrations must be repaired. Dings that include ribs must be repaired by reforming
or removal and replacement of the rib. Reevaluation of the skin after the repair of the understructure
will determine if the skin damage is negligible, repairable or requires replacement. Bonded ribs may be
removed by applying heat to the damaged area using a heat gun. Replacement ribs may be installed
using protruding head or dimpled flush rivets.
C. Damage Necessitating Replacement Of Parts: Where extreme damage has occurred, complete
leading edge skin panels should be replaced.
10. Wing Strut Damage Criteria
A. Negligible damage: Any smooth dents in the strut that are not more than 0.090 inch (2.03 mm) below
contour and circumscribable with not more than a 3.0 inch (76.2 mm) diameter circle is negligible
damage. Minor scratches which do not involve removal or displacement of strut material is negligible
damage. Because of the critical nature of the strut, any non-cosmetic scratches must be reworked.
Repairable damage: For grooves in the strut caused by fairings, strut may be repaired if groove is
B.
less than 0.020 inch and is more than 0.75 inch from a rivet center. For lower trailing edge strut
damage (typically caused by door hitting strut), strut may be repaired if groove depth is less than 50%
of original material thickness.
C. Damage Necessitating Replacement Of Parts: For grooves in the strut caused by fairings, strut must
be replaced if groove exceeds 0.010 inch in depth and is less than 0.75 inch from a rivet center AND/
OR if groove exceeds 0.020 inch in depth and is more than 0.75 inch from a rivet center. For lower
trailing edge strut damage (typically caused by door hitting strut), strut must be replaced if groove is
deeper than 50% of the original material thickness.
11. Aileron Damage Criteria (Corrugated Skin Aileron)
A. Negligible damage: Any smooth dents in the aileron skin that are not more than 0.050 inch (1.27 mm)
below contour and circumscribable with not more than a 1.5 inch (38.1 mm) diameter circle - that
have no evidence of skin tears, cracks or skin penetrations and which do not include a corrugation -
constitute negligible damage.
B. Repairable damage: Dents or dings deeper and/or larger than specified must be repaired. Skin tears,
cracks or penetrations must be repaired. Dings that include corrugations are unlikely to be reworkable,
but may be repaired by replacing the damaged area. Corrugated skin material is available from
Cessna. Special care must be taken to minimize added weight since the surface must be rebalanced
after rework.
C. Damage Necessitating Replacement Of Parts: Because of the balance requirements, multiple areas
of damage may require replacement of skins to allow balance limits to be attained.
12. Aileron Damage Criteria (Model 206 Aileron)
Negligible damage: Any smooth dents in the aileron skin that are not more than 0.030 inch (0.76 mm)
A.
below contour and circumscribable with not more than a 1.5 inch (38.1 mm) diameter circle - that
have no evidence of skin tears, cracks or skin penetrations which are not stress wrinkles and do not
interfere with internal structure - constitute negligible damage.
B. Repairable damage: Dents or dings deeper and/or larger than specified must be repaired. Skin tears,
cracks or penetrations must be repaired. Dings that include understructure (ribs) must be repaired
by reforming or removal and replacement of the rib. Revaluation of the skin after the repair of the
understructure will determine if the skin damage is negligible, repairable or replacement damage.
Special care must be taken to minimize added weight since the surface must be rebalanced after
rework.
C. Damage Necessitating Replacement Of Parts: Because of the balance requirements, multiple areas
of damage may require replacement of skins to allow balance limits to be attained.
CESSNA AIRCRAFT COMPANY
SINGLE ENGINE
STRUCTURAL REPAIR MANUAL
© Cessna Aircraft Company
57-10-00
Page 3
Jun 1/2005