MIL-PRF-81975C
3.8.3.2 Disengagement. The latching mechanisms (3 minimum) shall be such that the force
required to disengage the nozzle from the MA-3 and MA-4 couplings is adjustable between 300
and 550 pounds (300 and 800 lbs for MA-2 couplings) with zero psig fuel pressure in the
coupling, and without change or addition of components. The force required to disengage the
nozzle shall increase at the rate of 4 ±0.5 pounds for each 1.0 psi increase in regulated pressure at
any fixed adjustment. The coupling shall not disengage when subjected to a surge pressure of
120 psig (receiver side of coupling). Unless otherwise specified by the qualifying activity, the
setting of the latching mechanism shall be 320 ±20 pounds with zero psig fuel pressure. Under
these conditions, the disengagement force at 50 psi shall be 520 ±45 pounds. The force to
separate the nozzle from the coupling (with 10 psig or 50 psig of fuel pressure) with a toggle
setting of both 320 ±20 lb. and 520 ±45 lb. shall be not greater than 830 lb. when the disconnect
angle of the ball joint is at the 22.5° position.
3.8.4 Operating and proof pressure. The coupling shall be able to withstand a minimum
hydrostatic operating pressure of 120 psig with no external leakage, deformation, or structural
failure. The coupling shall also withstand a minimum internal hydrostatic proof pressure of 230
psig with no external leakage, deformation, or structural failure. Once this test is complete the
coupling shall pass the leakage tests of 4.8.5 and the functional tests of 4.8.14.
During flowing disconnects, very short duration surge pressure spikes at the inlet of the coupling
will greatly exceed the proof pressure limits specified above. The coupling shall be capable of
withstanding these short duration, elevated surge pressure spikes.
3.8.5 Leakage and spillage. The leakage and spillage shall be allowed as follows:
a. When the engaged MA-3 and MA-4 couplings and nozzle are subjected to fluid flow
rates up to 600 gpm (1200 gpm for MA-2 couplings) and a constant inlet pressure of 120 +2 psig
(60 +2 psig for MA-2 couplings), there shall be no evidence of external leakage.
b. When the engaged coupling and nozzle are subjected to an inlet fluid pressure of 120 ±2
psig and a fluid flow of 100 to 600 gpm, the spillage shall be not greater than 100 cc (25 cc for
MA-2) per disengagement.
c. When the coupling is engaged and disengaged on a nozzle with an inlet fluid pressure of
10 psig, spillage shall be not greater than 25 cc per engagement or disengagement.
3.8.6 Pressure drop. The pressure drop through the couplings shall be as follows:
a. MA-2 couplings: The total pressure drop through the engaged nozzle and coupling shall
be not greater than 3 psig at 600 gpm or 12 psig at 1,200 gpm.
b. MA-3 and MA-4 couplings: The total pressure drop through the engaged nozzle and
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