MIL-PRF-81975C
not peel off, crack, or loosen with age, environmental conditions, or damage resulting from aerial
refueling operations. The location selected for markings shall not affect the performance of the
coupling. The external surface of the coupling housing shall be identified with one coat of epoxy
primer conforming to MIL-PRF-23377, and two coats of either acrylic lacquer in accordance
with MIL-PRF-81352 or polyurethane in accordance with MIL-PRF-85285; color as specified in
FED-STD-595, color number 17875 (gloss white). A contrasting paint color to the white
background shall be used for the lettering product identification. On the casting the following
identification information should be found: part number, serial number, latch force settings, and
pressure regulator settings.
3.7.11 Workmanship. The coupling shall be uniform in quality, clean, and free from
defects. Attention shall be given to neatness and thoroughness of assembly, alignment of parts,
tightness of assembly, and removal of burrs.
3.8 Design. The coupling shall conform to figure 1 and be compatible with aerial refueling
nozzles conforming to MIL-N-25161 to accomplish fuel transfer in flight at inlet pressures up to
l20 psig. MA-3 and MA-4 couplings shall provide surge pressure protection for the receiver
aircraft along with steady state pressure control to prevent excessive pressures from entering the
receiver during refueling. This shall be accomplished by means of pressure regulating
mechanisms integral to the coupling; a single mechanism in the case of MA-3 couplings, while
the MA-4 couplings shall incorporate dual, redundant mechanisms. The failure of either
mechanism in MA-4 couplings shall not prevent the coupling from providing pressure regulation
and surge control as specified.
3.8.1 Regulator operation. MA-3 and MA-4 couplings shall be compatible with current
ground support equipment, unless agreed upon by the purchasing agency. Current ground
support equipment allows for ambient pressure sensing ports, three or four with circumference
spacing 120° for 3 ports and 90° for 4 ports, for each pressure regulation device. Each set of vent
ports shall be equipped with a boss in accordance with SAE-AS5202 to allow a fuel line
connection and plugs to be attached so that fuel pressure can be applied to one of the ambient
sensing ports, thereby causing the regulation device to remain open and inactive. The couplings
shall also be equipped with a fuel pressure sensing port downstream from the internal regulation
mechanisms. This port may be used as the fuel pressure source in lieu of the nozzle outlet
pressure during ground testing of the regulator(s). The regulation devices shall be designed so
that, in the event of a failure, they shall remain open and shall permit fuel transfer.
3.8.1.1 Regulation capability (MA-3 and MA-4 couplings). The coupling outlet pressure
shall be regulated within the limits shown below over the flow range of 10 cubic centimeters per
minute (cc/min) to 600 gallons per minute (gpm). An SAE-AS5202 port shall be provided to
measure toggle cavity regulated pressure. MA-4 couplings shall meet this requirement with
either regulator inactive (the regulated pressure may be different for each regulator).
a. For flow rates of 1 gpm to 600 gpm, if the inlet pressure is greater than the pressure drop
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