MIL-M-27274E(USAF)
3.4 0esign and construction. The design and construction of the mask shall be in accordance with Air Force drawings 6003516, 6003519, 6003522, 6003525 and 7425180 (see figures 1-9 inclusive). Air Force drawings 6003516, 6003519, 6003522, and 6003525 should be used as general guidelines in the design of tooling.
3.4.1 Plug. Each mask shall have a suitable leak tight plug for the microphone flange fabricated from metal, plastic, or hard rubber.
3.4.2 Antifreeze chamber. The antifreeze chamber and the body of the mask shall be of one-piece construction as shown (see figures 4 and 5). A 1/16 inch hole located as shown in figures 4 and 5 shall vent the antifreeze chamber.
3.4.3 Combination vaIve. A combination inhalation-exhalation valve conforming to MIL-V-27296, Type I, shall be inserted in the mask as shown (see figure 5).
3.4.4 0elivery tube. The delivery tube for the mask shall be constructed of corrugated silicone as shown (figure 6). The delivery tube shall have one upper cable guide (see figure 7) and located as shown (see figure 1).
3.4.5 Clamp. The delivery tube shall be attached to the combination valve by means of a hose clamp conforming to Scott Aviation 0ivision of Figgie, IntI. Inc., Sierra Madre, part number 450-134A or
approved equal. Clamp assembly pliers conforming to Scott Aviation, part number 450-801 may be used
to attach the clamp.
3.4.6 Connector. A connector conforming to MS27796 shall be attached to the delivery tube by means of a hose clamp conforming to MS22064-5 or other approved hose clamps. A lower cable guide (see figure 7) shall cover this hose clamp and shall be located as shown (see figure 1).
3.4. 7 Limited stretch cord. A nylon cord and snap assembly as shown (see figure 8) shall be installed inside the delivery tube by attaching a nylon loop to the combination valve retention pin and a metal snap to the connector retention pin. The snap shall be Pacific Marine Supply Company, Seattle, Washington, size No. 2/0 (1 3/16 inches in length, 110-pound test), or equal, and shall be attached to one end of the nylon cord as shown (see figure 8).
3.4.8 Hardshell assembly. The hardshell assembly shall consist of the hardshell including the installed hardshell webbing, harness fasteners with screws, and suspension harness restrained. The hardshell assembly shall be as shown (see figures 1 and figure 9).
3.4.8.1 Hardshell. The hardshell for the mask shall closely follow the contour of the outside of the facepiece and shall be designed to assure that all of the performance requirements specified herein are met. The edges of the hardshell nearest the user's face shall be flared, and all sharp edges shall be rounded. 0imensions given (see figures 2 and 3) may be used as general guidelines in the design of the hardshell.
3.4.8.2 Hardshell webbing. The webbing shall be riveted to the hardshell as shown (see figure 1) by
1/8 inch tubular rivets having a minimum head diameter of 9/32 inch.
3.4.8.3 Harness fasteners. Fasteners conforming to MS27980 and MS27983 shall be located in the hardshell as shown (see figure 9). Two machine screws (3-56NF-3A by 0.375 inch long) shall secure the harness assembly to the hardshell. These machine screws shall be provided as part of the hardshell assembly.
3.4.8.4 Suspension harness restrainer. A suitable device as shown (see figure 1) shall be provided for restricting the lateral movement of the harness assembly when the mask is used with a continuous single strap suspension harness assembly. The device shall be provided as a component of the hardshell assembly and shall be approved by the procuring activity.
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