CESSNA AIRCRAFT
COMPANY
SINGLE ENGINE
STRUCTURAL REPA
IR MANUAL
4 Remove residual corrosion by hand sanding.
5 After removing all corrosion visible through a magnifying glass, fair depression
resulting from
rework and finish with 400-grit abrasive paper.
6 Clean reworked area.
7 Determine depth of rework area to ensure rework limits are not exceeded.
8 Prime using rus
t-inhibitive primer within one hour of rework.
9 Reapply finish topcoat if required.
7. Control of Corr
osion on Landing Gear Springs
A. General
(1) The main landing gear springs are made from high strength steel that is shot peened on the
lower surface t
o increase the fatigue life of the part.
(2) The shot peened layer is between 0.010 and 0.020 inch thick.
(3) If the protective layer of paint is chipped, scratched or worn away the steel may corrode (rust).
(a) If the corrosion
pit depth is greater than the thickness of the shot peen layer, the gear spring
fatigue life will be greatly reduced.
(4) Operation from unimproved surfaces increases the likelihood of damage.
B. Corrosion remov
al and repair.
(1) If damage to the paint finish of the landing gear spring is found, examine the damage area for
signs of corrosion (red rust).
WARNING: High strength steel parts are very susceptible to hydrogen
embrittlement. Acidic solutions, such as rust removers
and paint strip
pers have been found to cause hydrogen
embrittlement. Hydrogen embrittlement is an undetectable,
time delayed process. Since the process is time delayed,
failure may oc
cur after the part is returned to service. The
only reliable way to prevent hydrogen embrittlement is not to
use chemical rust removers or paint strippers on landing gear
springs.
(2) Carefully remove any rust by light sanding.
(a) The sanding s
hould blend the damage into the surrounding area in an approximate 20:1
ratio.
EXAMPLE: An 0.005 inch
pit must be blended to a 0.10 inch radius or 0.20 inch
diameter.
(b) Make sure the
final sanding marks are along an inboard to outboard direction, or along the
long dimension of the spring.
(3) After the sanding is complete, measure the depth of the damage removal.
(a) Make sure the
depth of the damage is not more than 0.010 to 0.012 inch deep and has not
penetrated the shot peen layer.
(4) If the shot peened layer has been penetrated, the gear spring must be removed and sent to an
approved fac
ility to be re-shotpeened.
(a) The shotpeen specification is to be Almen intensity of 0.012 to 0.016 using 330 steel shot.
(5) After the spring is installed, refinish any damaged or removed finish paint.
NOTE: Additional information regarding corrosion control can be found in AC-43-4, Chapter
6, or AC43.13-1B Chapter 6.
51-11-00 Page 7
© Cessna Aircraft Company Jun 1/2005
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