Cessna 172 Maintenance Manual page 57

1. General
A. Damage which would involve a typical skin repair can be described as damage that requires
modification, such as material replacement or patching. Skin damage in the form of dents, scratches,
or punctures requires a patch. Refer to Figure 801, for an illustration of typical skin repairs. Refer to
Figure 802 for corrugated skin repairs.
2. Guidelines for Corrugated Skin Crack Repairs
A. Corrugated Aileron Skin Repair:
(1) It is permissible to stop drill crack(s) that originate at the trailing edge of the control surface
provided the crack(s) is(are) not more than 2 inches in length.
(2) Stop dill crack(s) using a Number 30 (0.128 inch diameter) drill.
(3) A crack may only be stop dilled once.
NOTE:
(4) Any control surface that has a crack that progresses past a stop drilled hole shall be repaired or
replaced.
(5) A control surface that has any of the following conditions shall have a repair made as soon as
practical:
(a) A crack that is longer than 2 inches.
A crack that does not originate from the trailing edge or a trailing edge rivet.
(b)
(c) Cracks in more than six trailing edge rivet locations per skin.
(6) Affected control surfaces with corrugated skins and having a stop drilled crack that does not
extend past the stop drilled hole, may remain in service without additional repair.
(7) Refer to Figure 802 as applicable for repair information.
B. Corrugated Flap Skin Repair:
(1) It is permissible to stop drill crack(s) that originate at the trailing edge of the control surface
provided the crack(s) is(are) not more than 2 inches in length.
(2) Stop dill crack(s) using a Number 30 (0.128 inch diameter) drill.
A crack may only be stop dilled once.
(3)
NOTE:
(4) Any control surface that has a crack that progresses past a stop drilled hole shall be repaired or
replaced.
(5) A control surface that has any of the following conditions shall have a repair made as soon as
practical:
(a) A crack that is longer than 2 inches.
(b) A crack that does not originate from the trailing edge or a trailing edge rivet.
(c) Cracks in more than six trailing edge rivet locations per skin.
(6) Affected control surfaces with corrugated skins and having a stop drilled crack that does not
extend past the stop drilled hole, may remain in service without additional repair.
(7) Refer to Figure 802 as applicable for repair information.
C. Corrugated Elevator Skin Repair:
(1) It is permissible to stop drill crack(s) that originate at the trailing edge of the control surface
provided the crack(s) is(are) not more than 2 inches in length.
(2) Stop dill crack(s) using a Number 30 (0.128 inch diameter) drill.
(3) A crack may only be stop dilled once.
NOTE:
CESSNA AIRCRAFT COMPANY
SINGLE ENGINE
STRUCTURAL REPAIR MANUAL
TYPICAL SKIN REPAIRS
A crack that passes through a trailing edge rivet and does not extend to the trailing
edge of the skin may be stop drilled at both ends of the crack.
A crack that passes through a trailing edge rivet and does not extend to the trailing
edge of the skin may be stop drilled at both ends of the crack.
A crack that passes through a trailing edge rivet and does not extend to the trailing
edge of the skin may be stop drilled at both ends of the crack.
© Cessna Aircraft Company
51-75-00
Page 801
Jun 1/2005