Cessna 172 Maintenance Manual page 26

C. Axle bolt hole corrosion.
(1) Operation of an airplane on skis increases the loads on the lower part of the gear spring because
of the unsymmetrical and twisting loads.
(a) The increased loads have produced spring fractures that originate from pits in the axle
attach holes.
1 Catastrophic failures have occurred from fatigue cracks as small as 0.003 to 0.010
inch long that originated at pits.
(b) Although operation on skis causes more loads, the criteria applies to all airplanes.
(2) There is no acceptable damage depth for pits that develop in the axle bolt holes. If pits or
corrosion is found it must be removed by reaming, subject to the following limitations:
(a) Remove the minimum material required to clean up the damage.
Make sure the diameter of the axle attachment holes is 0.383 inches maximum for 3/8 inch
(b)
bolts.
(c) Make sure the diameter of the axle attachment holes is 0.321 inches maximum for 5/16
inch bolts.
(d) If reaming to the maximum dimension does not remove all signs of corrosion, discard the
landing gear spring.
CESSNA AIRCRAFT COMPANY
SINGLE ENGINE
STRUCTURAL REPAIR MANUAL
© Cessna Aircraft Company
51-11-00
Page 8
Jun 1/2005