The SPH-3C helmet protects the wearer’s head during in-flight buffeting or crash landings. It is designed to distribute impact forces over the entire head, and to absorb these forces so that a mini- mum amount of impact reaches the wearer’s head. The SPH-3C helmet is supplied in two sizes, regu- lar and extra large. The helmet consists of an outer shell assembly, an inner foam liner, sizing liner, inner cloth liner assembly, dual integrated visor, communication cord set, and a microphone adapter. The outer shell assembly is fabricated from Kevlar and polyester resin, and it provides impact and penetration protection. An edge roll, made of neoprene foam, provides protection from the helmet edges. The inner foam liner is made of cellular polystyrene sheets molded to fit the inside contour of the outer shell. The liner is provided to absorb and dissipate impact forces. The sizing liner, which is optional, aids in fitting the helmet to the aircrew member’s head contour by padding the helmet at the nape of the neck. Sizing liners are provided in 1/4-, 1/2-, and 5/8-inch sizes. The inner cloth liner assembly includes the sonic earcup assemblies and foam pads for sizing and comfort; it also has adjustable crown and nape straps. The dual integrated visor provides protection from sun glare, dust, windblast, foreign particles, and flash fires. The visors are protected by a molded fiberglass housing when not in use. Two visors, clear and neutral, are available. The percentage of visible light transmittance of the neutral visor is 8 to 16 percent. The percentage of light transmittance of the clear visor is 87 percent or greater. The communications cord set connects the aircraft communications system to the helmet earphones. The microphone adapter, located on the helmet, allows attachment of a boom-type microphone. Fitting The SPH-3C protective helmet must be individually fitted to the aircrew member. For maximum protection, comfort, and sound attenuation, a good fit is a snug fit at the cheeks, forehead, and nape of the neck. A loose fitting helmet is more apt to produce pressure areas and discomfort. If the helmet moves independently of the head, readjust the sizing liners, spacers, and adjusting straps. If necessary, file and sand the nose indentation to fit the contour of the aircrew member’s nose. Ensure that the visor at the nose indentation is free of nicks and roughness. Maintenance Procedures Minimal maintenance, which is cleaning the visor and outer shell, can be performed by the air- crew member as needed. All other maintenance operations must be performed upon issue and at least every 90 days thereafter by qualified person- nel at the lowest level of maintenance possible. Inspect the sizing liners and inner foam liner for looseness, re-cement where applicable, and re- place worn or torn sizing liners. Inspect the shell assembly for cracks, dents, scratches, splits, and delamination. Inspect all hardware for damage and security of attachment, tighten or replace hardware as necessary. Inspect straps, communi- cations cord set, earphones, and dual visor as- sembly for damage. Replace parts as necessary. The visor may be cleaned with mild soap and water and dried with a soft, clean cloth. To remove minor scratches or remaining soiled areas, use acrylic plastic polish. To preserve the visor’s plastic surface, use polishing wax for the final application. Do not use solvent or abrasive-type cleaners. OXYGEN MASKS The oxygen mask is the final link in conveying oxygen from the aircraft system to the user. A ^- satisfactory regulator and oxygen system or a full cylinder’ of oxygen is of little value to a pilot if his oxygen mask is not operating properly in every respect. The oxygen mask is the pilot’s personal equipment; that is, after initial fitting, they are retained by the individual. Fitting, adjustments, maintenance, cleaning, and incorporating modifications are the responsibility of the PR. The important factor to remember about identifying any oxygen mask is its compatibility with the oxygen system with which the mask is to be mated. PRESSURE-DEMAND OXYGEN MASK MBU-12/P Oxygen mask assemblies are designed to be worn over the face, forming a seal to the cheeks over the bridge of the nose and under the chin. The mask is designed for use with a regulator, which provides breathing gas (100-percent oxygen or oxygen diluted with air) upon demand at a pressure schedule dependent on the altitude. The mask can also be used with continuous-flow 4-24