MIL-PRF-32516
APPENDIX B
TEMPERATURE STIMULATION
B.1 SCOPE
B.1.1 Scope. This appendix deals with ways to isolate faults related to operating
temperature. This appendix is not a mandatory part of the specification. The information
contained herein is for guidance only.
B.2 DETERMINING CAUSES OF INTERMITTENT FAILURES
B.2.1 Introduction. Each LRU/WRA is different in its function and operational
environment. As a result, no single test method or procedure can adequately replicate an
intermittent fault occurrence for all LRUs/WRAs. A careful review of the nature of the failure
and the operational conditions under which the failure occurred is required. The following steps
are recommended when by careful analysis it is determined that the failures occur during ground
or flight operating conditions, and the operating temperature appears to be contributing to the
occurrence of the failures.
B.2.2 Typical resulting effects. The following is a list of typical resulting effects of
temperature-induced problems (this list is not intended to be all-inclusive):
a. Binding or slackening of moving parts.
b. Deformation or fracture of components.
c. Cracking of surface coatings.
d. Leaking of sealed compartments.
e. Failure of insulation protection.
f. Differential contraction or expansion rates or induced strain rates of dissimilar
materials.
g. Intermittent electrical contacts.
h. Electrical shorts/opens.
i. Failed components.
j. Changes in electrical and electronic components.
k. Electronic or mechanical failures due to rapid water or frost formation.
l. Excessive static electricity.
B.2.3 Operational temperature environment. A review should be conducted of technical
manuals, operating manuals and any available information that provides insight into the
operational temperature environment of the LRU/WRA. As much as practical, this information
should be used to tailor a temperature cycling profile for temperature stressing the LRU/WRA
while troubleshooting the LRU/WRA for intermittent faults. It is not necessary to temperature
cycle the LRU/WRA at full qualification levels which may induce additional failure modes. It is
recommended that where the operational temperature test levels are not known that the
qualification temperature levels during troubleshooting of the LRU/WRA be reduced in order to
not over stress the LRU/WRA. The intent is to subject the LRU/WRA to a temperature level
low/high enough to stimulate the intermittent fault, but not reduce the operational life of the
LRU/WRA.
B.2.3.1 Unknown temperature operational limits. Where the temperature operational
limits are unknown, MIL-STD-810, Test Method 503 should be used to tailor the LRU/WRA
temperature stimulation test sequence as a function of the life cycle environments of the
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