MIL-DTL-25427B
TABLE III. Air inclusion and fluid loss for all pressure classes.
Dash
Tube
Air inclusion
Average fluid
3
3
No.
OD
Loss per operating cycle
cm (in) max
3
3
(spillage) cm (in) max
3000 psi
5000 psi
3000 psi
5000 psi
-04
0.250
0.05
0.10(.006)
0.50 (.031)
0.05 (.003)
-06
0.375
0.12
0.20 (.012)
1.30 (.079)
0.10 (.006)
-08
0.500
0.20
0.40 (.025)
2.20 (.134)
0.20 (.012)
-10
0.625
0.50
0.60 (.037)
5.80 (.354)
0.30 (.018)
-12
0.750
0.70
1.00 (.061)
8.20 (.500)
0.50 (.031)
-16
1.000
0.90
1.75 (.107)
9.00 (.549)
1.00 (.061)
-20
1.250
1.20
2.00 (.122)
11.80 (.720)
1.20 (.073)
-24
1.500
1.20
2.50 (.153)
11.80 (.720)
1.50 (.092)
3.6 Interchangeability of bulkhead halve coupling. Bulkhead halve couplings (mounted
on aircraft) shall be interchangeable as an assembly or individual coupling halves for same tube
size and pressure class. It shall be designed not to interconnect coupling assembly or coupling
halves of different tube sizes. Couplings of different pressure classes shall not be capable of
cross coupling. This requirement does not apply to hose end couplings which shall be
interchangeable regardless of pressure classes.
3.7 Performance. The self sealing coupling furnished under this specification shall
perform satisfactorily when conducting to the following performance requirements.
3.7.1 Envelope dimensions, weight, materials. Each coupling half shall conform to the
applicable specified envelope dimensions, weight, materials, and finishes specified in the
applicable specification sheet.
3.7.2 Manual operation. Coupling halves shall be tested in accordance with the
requirements specified in 4.8.2 with no evidence of coupling forces, leakage or spillage beyond
the specified limits specified in table IV and table III respectively. Both coupling halves shall be
installed in the systems capable of accommodating fluid displacement without pressure rise.
3.7.3 Immersion. The self sealing coupling contains nonmetallic parts and therefore
shall be compatible with hydraulic fluid and show no leakage, damage or malfunction when
tested as specified in 4.8.3.
3.7.4 Air inclusion. The air inclusion for all coupling halves shall be within specified
limits conforming to table III at 30 inches of hydraulic fluid static pressure (15 psi).
7
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