TM 5-4220-225-14
5-8.
Viewport Assemblies (Cont).
c.
Replace (Top). (figure 5-7)
(1)
Remove 11 screws (1), viewport retainer (2), viewport (3), and preformed packing (4).
(2)
Inspect retainer (2) and replace if cracked, warped, or rusted.
(3)
Inspect helmet shell (5) around viewport and replace if shell is cracked.
(4)
Apply a thin film of lubricant to new preformed packing (4).
(5)
Ensure preformed packing groove is clean.
(6)
Install new preformed packing (4).
(7)
Install viewport (3) and ensure new preformedpacking (4) stays in groove.
(8)
Install retainer (2) and secure with four corner screws (1) finger tight.
(9)
Install remaining seven screws (1).
(10)
Torque all screws (1) to 8-10 in.-lb (0.9-1.2 Nm) in a crisscross staggered sequence to prevent warping or
cracking of viewport (3) or retainer (2).
(11)
Ensure new preformed packing (4) has not extruded.
5-16
