MIL-PRF-81975C
+55 psig, the regulated outlet pressure shall be 50 +5 psig.
b. With inlet pressures up to 120 psig at a flow rate of 10 cc/min to 600 gpm, the regulated
outlet pressure shall be not greater than 60 psig at flow rates between 10 cc/min and 1 gpm, or 55
psi at flow rates greater than 1 gpm, unless stated otherwise in the contract.
c. With a flow rate of 600 gpm and cycled inlet pressure rates from 60 to 100 psig, the
outlet pressure shall be not greater than 60 psig with no external leakage and shall pass the
functional test.
d. With an inlet pressure of 60, 80, and 100 psig and a flow rate below 10 cc/min, the
regulated outlet pressure shall not increase greater than 10 percent of the inlet pressure.
3.8.1.1.1 Relief valves (MA-3 and MA-4 couplings). Regulator designs, which allow
trapping of high pressures within the coupling that could hamper engagement, shall be provided
with an internal pressure relief system to dissipate the trapped pressure within 10 seconds.
3.8.1.1.2 Pressure sensing ports (MA-3 and MA-4 couplings). Internal cavities, which join
the ambient pressure sensing ports, shall drain when the coupling is in the stowed horizontal
position so that any accumulated water condensate shall not, when frozen, render the regulator
inoperative.
3.8.1.2 Surge suppression (MA-3 and MA-4 couplings). The coupling shall be capable of
suppressing surges without sustaining damage. Surge pressure peaks recorded downstream of
the coupling within 30 inches of the MA2 nozzle interface to the probe shall be not greater than
120 psig. Outlet pressures shall equalize within 10 seconds. MA-4 couplings shall meet these
requirements with either regulator inactive.
3.8.2 Alignment. The coupling shall incorporate a ball joint having a range of movement
within a 45-degree or greater included angle cone, the centerline of which shall coincide with the
centerline of the coupling. The ball joint action shall facilitate alignment with an MA-2 nozzle
and shall permit 360 degrees of rotation of the coupling body when engaged with an MA-2
nozzle. Body rotation shall not be restricted by the nozzle design. The force required to move the
coupling ball (without fuel pressure) throughout the complete range of movement shall be not
greater than 20 pounds as applied to the coupling outlet flange. The force required to rotate the
body about the ball joint shall be not greater than 50 ft-lbs with a 100-pound radial load applied
to the outlet flange.
3.8.3 Latching mechanisms.
3.8.3.1 Engagement. The force required to engage couplings of all classes with an MA-2
nozzle having a 50-pound sleeve force shall be not greater than 155 pounds with a 0 to 10 psig
static fuel pressure in the coupling.
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