TM 1-1520-238-23
1-402.20
Change 11
1.137.
SPECIAL INSPECTION CHECKLIST – continued
Helicopter Serial No.:
Date:
Area
No.
Special
Inspection
No.
REQUIREMENT
EVERY
Item
Status
4
50A
(cont)
(5) If the number 1 stud marked above does not correspond with the
number1 fork hole marked in paragraph 50A.c.(1), the fork was
incorrectly indexed during installation. Replace all three studs per
paragraph 50A.c.
(6) 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 per paragraph 50A.c.
(7) 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 using paragraph
50A.c.
CAUTION
MIL-A-9962 abrasive mat or equivalent is aluminum oxide impegnated nylon
webbing. Its use must be limited to the corroded areas in order to minimize the
cadmium plating removal.
(8) 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 cause for rejection.
Corrosion will appear brown or read 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 in
accordance with paragraph 50A.c.
(9) Checks studs for looseness per TM 1-1520-238-23. Replace studs if
free play exceeds 0.022 inch.
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