Table 4-1.  Aviation Unit Preventive Maintenance Checks and Services ITEM NO. INTERVAL ITEM TO BE INSPECTED/ PROCEDURE NOT FULLY MISSION CAPABLE IF: 6. 7. 8. 9. 10. 11. 12. 13. 14. Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120 days Every 120  days Every 120 days Every 120 days Every 120 days Earseals. Inspect for cuts, tears, split seams. Retention assembly. Inspect for broken, loose, or missing hardware; split seams; fraying; dirt. Communications system. Check earphones for malfunctions. CEP-equipped helmets only: Check CEP for malfunctions. CEP-equipped helmets only: Check earplug foam tips for dirt or wear. Check microphone for malfunctions. Check boom assembly for malfunctions. Check boom assembly for malfunctions. Visor assembly. Check attachment of mounting hardware. Inspect housing for cracks. Inspect visor lenses for scratches. Check operation of visor lenses. Oxygen mask (when used). Refer to TM 55-1660-247-12. Oxygen mask bayonet receivers (if installed). Check attachment of receivers. Check receivers for malfunctions. ANVIS goggles. Refer to TM 11-5855-263-10. AH-1 sight. Refer to TM 9-1270-212-14&P. Helmet Bag. Inspect for dirt, missing hardware, broken stitching. Cuts or tears exist; seams are split, inner foam is exposed. Hardware is broken, loose, or missing; seams are split; fab- ric is frayed, oily, greasy, or dirty. Earphones are malfunction- ing. CEP is malfunctioning. Foam is dirty, worn, or pulled back from plastic tubing. Microphone is malfunctioning. Boom fails to hold microphone in place. Hardware is loose or missing. Housing is cracked. Scratches exist in viewing area. Visor lenses do not move freely in tracks. Receiver is loose or missing. Receiver fails to hold bayo- net in place or release it. Fabric is dirty; hardware is missing; stitching is broken. 4-4 Change 3 TM  1-8415-216-12&P