TM 5-4220-225-14
5-8.
Viewport Assemblies.
This task covers:
a.
Replace (front)
b.
Replace (side)
c.
Replace (top)
INITIAL SETUP
Tools
Materials/Parts
9/64-inch Hex Wrench (Item 22, Appendix B)
Top Viewport
0-50 lb-in. Torque Wrench (Item 14, Appendix B)
Side Viewport
Socket Wrench Adapter, (Item 41, Appendix B)
Front Viewport
Hex Insert (Item 51, Appendix B)
Halocarbon Grease 25-55 (Item 10, Appendix E)
MK12 Test Set (Item 44, Appendix B)
a.
Replace (Front). (figure 5-5)
(1)
Remove 16 screws (1), viewport retainer (2), viewport (3) and preformed packing (4).
(2)
Inspect retainer (2) and replace if rusted or cracked.
(3)
Inspect helmet shell (5) around front viewport (3). Replace helmet shell (5) if 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) in groove.
(7)
Install front viewport (3) and ensure new preformed packing (4) stays in groove.
(8)
Install retainer (2) and four corner screws (1) finger tight.
(9)
Install remaining 12 screws (1) finger tight.
(10)
Torque all screws (1) to 8-10 in.-lb (0.9-1.2 Nm) in a crisscross staggered sequence to prevent cracking or
warping of viewport (3) or retainer (2).
(11)
Ensure new preformed packing (4) has not extruded.
5-12
