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|  part of the heater shall be used for the test installation; no other
braces, straps, tiedowns, or auxiliary devices shall be used, either
externally or internally. There s.nail be no resonance in the test
fixture between 7 and 400 cps. Removable covers and access doors shall
be in place during all testing except during the resonance search which
will be made during tne initial part of the sinusoidal-cycling-run.
Separate accelerometers shall be installed for each main support of the
heater and for the pump and the control box. In event of differences
in the "G" values measured by these accelerometers, the vibration
acceleration shall be controlled to keep the least of the corrected
readings at or above 2.5G. Structural damage, misalinement, leaks of
fuel or coolant, or component-malfuction shall constitute failure of
these tests.
4.5.4.9.2.1 Resonance search. Conduct the resonance search using
vibration-acceleration input less than 2.5G If supplier so elects;
however, if this is done the time shall not be credited toward fulfillment
of the sinusoidal-cycling requirements. Open up the heater as much as
practicable to observe resonance of internal parts. Use stroboscope, high-
intensity lights, or similar devices to facilitate the detection and
evaluation of the resonances.
4.5.4.9.3 Shock. Conduct the shock tests in accordance with MIL-STD-810,
Method 516, Procedure I. Structural damage, misalinement, leak of fuel
or coolant, or component malfunction shall constitute failure of these
tests.
4.5.4.9.4 High-temperature storage . Subject the heater to an ambient
temperature of 155 F for a period of 4 hours per day for 2 days. structural
damage, misalinement, leak of fuel or coolant, or component malfunction
shall constitute failure of these tests.
4.5.4.9.5 low-temperature storage. Subject the heater to an ambient
temperature of minus 65 F for a period of 72 hours. Structural damage,
misalinement, leak of fuel or coolant, or component malfunction shall con-
stitute failure of these tests. (Note: This test may be scheduled
separately from others in the environmental series, may use the same facilities
used for the cold start and heat output repeat tests and in coordination
with those tests.)
4.5.4.10 Coolant pump. Pump antifreeze conforming to MIL-A-11755 and
control input-voltage to the motor to 24 volts. Nonconforman ce to Table V
shall constitute failure of this test.
4.5.4.11 Coolant pressure. Fill the heater with water or antifreeze,
connect to pressure source, and apply liquid pressure of at least 35
pounds . Maintain this pressure for at least 5 minutes. Evidence of leaks
or permanent distortion shall constitute failure of this test.
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