TM 1-1520-238-23
Change 11
1-402.27
1.137.
SPECIAL INSPECTION CHECKLIST – continued
Helicopter Serial No.:
Date:
Area
No.
Special
Inspection
No.
REQUIREMENT
EVERY
Item
Status
4
55
(cont)
(4) Inspect stud for damaged, stripped or crossed threads and/or obvious
necking.
(5) Inspect the nut with a 10 power magnifier for elongation, thread
damage, corrosion, and/or cracks. Inspect for damage to visible
portion of the needle-bearing and shaft. None allowed.
NOTE
Axial wear of only the cadmium plating itself is not cause for
rejection.
d. Inspect studs for axial scoring/gouging into the parent material. If scoring
is detected, the head assembly was previously incorrectly indexed, and all
three studs must be replaced.
e. Check for radial wear marks (smiles) between 1-1/2 and 2 inches outboard
of the lockring, as shown in Figure 4. If these marks exist or corrosion
prevents inspection in the area between 1-1/2 and 2 inches outboard of the
lockring, replace all three studs.
CAUTION
MIL-A-9962 Abrasive Mat or equivalent is aluminum oxide impreg-
nated nylon webbing. Its use must be limited to the corroded areas
in order to minimize the cadmium plating removal.
f. Check the remaining area on the studs for corrosion. (the remaining area
is the area not between 1-1/2 and 2 inches outboard of the lockring.)
General dulling of the surface is the first stage of corrosion. Darkening of
the cadmium plate finish is not caused for rejection. Corrosion will appear
brown or red in color. This corrosion is acceptable provided that deposits
are easily removable with scotchbrite, abrasive mat (MIL-A-9962, very
fine, NSN 5350-00-967-5089) or equivalent. To remove corrosion, the
scotchbrite must be cut into a strip just wide enough to cover the corrosion
products. The use of wider strips will remove cadmium plating, which will
degrade the corrosion protection available. Apply corrosion preventive
compound, MIL-C-16173, Grade IV or equivalent to studs prior to
reassembly. If corrosion cannot be easily removed, replace corroded
studs.
g. Check studs for looseness. Replace studs if free play exceeds 0.022 inch.
h. Check spline teeth on both the tail rotor fork and drive shaft for sealant.
Remove sealant if present. Do not reapply sealant.
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