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|  MIL-T-5578C
with brown paper held in place with a suitable
acceptable to the procuring activity and shall
conform to the following requirements:
adhesive. The tank with fittings assembled
(a) Class A tanks or portions thereof,
shall be subjected to a 7-day soak with type III
except those with cells containing suspension
fluid, at a fluid temperature of 135 F. Follow-
or supporting arrangements which may be sub-
ing the hot fuel soak, the tank shall be emptied
ject to failure due to vibration shall be slosh
and air dried for a period of 7 days at a tem-
tested.
perature of 160 F. On completion of the 7-
Test conditions:
day period of air drying, the tank shall be
Time :40 hours.
filled with type I fluid, containing a staining
Rock: Total of 30, approximately 15
agent, and placed in a cold box for a period of 3
on either side of the horizontal
days. The cold box shall be maintained at a
position.
temperature of 65 F for the 3-day period.
Cycles per minute: 10 to 16.
At the end of this 3-day period, the tank shall
(b) Class A tanks or portions thereof, with
be removed from the cold box, drained, and ex-
cells containing supporting or suspension ar-
amined for any indications of leakage. The
rangements which may be subject to failure due
tank shall then be filled with type III fluid,
to vibration, and Class B tanks shall be slosh
containing a staining agent and allowed to
and vibration tested.
stand at ambient temperature for a period of
Test conditions:
80 days, at which time the fluid shall be drained,
Time: 25 hours simultaneous slosh and
and the tank examined for any unsatisfactory
vibration and 15 hours additional slosh.
condition or indication of fuel leakage as shown
Rock: Total of 30, approximately 15
by any indication of stain on the brown paper
on either side of the horizontal
or activation of the tank sealant. Sealant acti-
position.
vation or any leakage of the tank, or at the
Cycles per minute: 10 to 16.
attachment of its component(s), shall be con-
Displacement: The throw of the two ec-
sidered as a tank failure. In the event of fail-
centric weights on the vibration ma-
ure at the attachment of the component,
chine shall be in the same direction
retesting for this condition may be simulated in
and shall be adjusted to produce a total
other than a full scale tank.
displacement of 0.032 inch, +0.010
4.6.10.1 Dissection. After completion of the
inch, -0.000 inch measured at point of
above test, the cell shall be dissected as shown
inherent rigidity on the tank.
in figure 2. The sectioned portion of each cell
Speed:
shall be examined for conditions outlined in
Type I tanks-90 percent of normal
Bulletin No. 107.
rated crankshaft speed.
4.6.11 Accelerated kind. The tank assembly
Type II tanks-2,000 + 100 rpm.
shall be mounted in a test jig that provides sup-
(c) Remove cell from structure and ex-
port equivalent to the aircraft structure for
amine for evidence of damage or failure.
which it is designed and subjected to a load test
4.6.9.2.1 Alternate vibration frequency and
as mutually agreed upon between the contractor
displacement. Where the above frequencies and
and the procuring activity to determine the
displacements are not applicable, the tank shall
suitability of the tank installation under air-
be vibrated at a frequency and displacement
craft design accelerations, including the appro-
agreed upon by the contractor and the procur-
priate dynamic magnification factors. Tanks
ing activity,
of pressurized systems shall be subjected to
4.6.10 Aging and low temperature leakage.
normal operating pressures during this test, ex-
For this test, the tank shall be mounted in a
cept where unpressurized conditions are con-
structure for which it is designed, or a simu-
sidered to be more critical. There shall be no
lated test sample incorporating identical tank
structural failure of any components of the
fitting installations. The interior of the test
tank during these tests. Deflection of the tank
structure around fitting areas shall be lined
shall be measured and shall be such that there
20
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