Fitting

The concept of fitting as used here refers to procedures required for necessary component adjustment following oxygen mask assembly buildup. Fitting instructions are provided only as a general guide. Because of the wide variation in facial shapes likely to be encountered, it is not possible to present detailed guidance. A successful fit depends largely on the skill and experience of the Aircrew Survival Equipmentman in selecting and adjusting the oxygen mask assembly to the aircrew member's face. Improperly fitted oxygen masks do not provide a positive face seal for pressure breathing and do not protect the aircrew member in emergency situations.

Have the aircrew member don the helmet, and ensure that the helmet nape strap has been adjusted to a snug fit. Insert each bayonet into the second locking position of the receiver and adjust the straps until the mash is snug and comfortable. Attach the straps in place with two turns of "E" thread. Perform a functional check ^{on the oxygen mask.} 

_{NOTE: If leaks occur between faceform and face, check to see if proper mask size} has been issued. If leakage still occurs, _{adjust helmet bayonet receivers. Refer to} table 4-4 for troubleshooting procedures.

Table 4-4.-Troubleshooting

whom the oxygen mask is issued before each

flight. The preflight/postflight inspection consists of-the following-procedures:

NOTE: Defects or questionable areas noted during this inspection must be referred to the proper maintenance activity for required corrective action.

1. Check the communication system and microphone for proper installation.

2. Check the mask for damage and proper operation by using the tester and/or aircraft oxygen and communications system.

Calendar Inspection

The calendar inspection is conducted every 30 days at the organizational level and consists of a visual inspection, a functional check, and a thorough cleaning of the oxygen mask assembly. Refer to NAVAIR 13-1-6.7 for visual inspection and functional check procedures.

NOTE: If a discrepancy is noted, refer to table 4-4 for guidance.

Cleaning Mask

To clean and sanitize the oxygen mask facepiece and housing assembly, proceed as follows:

Preferred solution. Make a 1 percent by weight solution of cleaning compound (Detergent, General Purpose, MIL-D-1 6791, Type I) by adding 1/4 to 1/2 ounce (liquid) of the compound to 1 gallon of water.

CAUTION

WHEN THE FOLLOWING ALTER-NATE CLEANING SOLUTION MUST BE USED, ONLY THE LATHER FROM THE SOLUTION IS USED FOR CLEANING. THIS PREVENTS UN-DISSOLVED SOAP SOLUTION FROM GETTING INTO THE VALVE.

Alternate solution. Make a suitable soap solution by adding approximately 4 tablespoons of soap powder (P-S-600) to 1 gallon of water. Hardness of water may require more soap, but the solution must be sufficiently strong to readily form lather when agitated. Make sure that all soap particles are dissolved.

Figure 4-26.-Adjustment of bayonet receivers.

Adjustment of Bayonet Receivers

To adjust the bayonet receivers, loosen the two adjusting screws (fig. 4-26) and rotate the receivers until the mask fits properly. Retighten the adjusting screws.

NOTE: Ensure that the top buckles are tacked down prior to any adjustment.

Adjustment of the bayonet receivers is performed with the helmet assembly and oxygen mask assembly donned by the aircrew member.

When properly fitted, the MBU-12/P oxygen mask can retain a pressure in excess of ambient pressure up to the maximum pressure supplied by the regulator.

Maintenance

Proper care and use of oxygen masks is essential to ensure optimum performance during routine flight operations and emergencies. The aircrew member's responsibility for maintenance of the oxygen mask is limited to cleaning. Repairs or other maintenance actions required are performed at the organizational level or above.