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Reliability Engineering Analysis |
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|  MIL-D-81347C(AS)
4.4.3.2.3
Life Test of Switches - The Keyset and Panel monofunction
Series 90E and Series 500 switches or their equivalents shall be subjected to Life Tests at normal
room ambient environmental condition with simulated normal equipment switch loads. The life re-
quirements are 25,000 cycles electrical life and 50,000 cycles mechanical life. The switches shall be
tested for 1000 hours consisting of 20 intervals as follows:
(1) Switching operation -8 hours
(2) No operation -8 hours
(3) Switching Operation -24 hours
(4) No Operation -40 hours
4.4.3.2.3
Logic Unit 4 Test Analyze and Fix (TAAF) Test - A group of
two Logic Units 4 shall be tested under conditions described in 4.4.3.1.1 for a fixed length operating
time of 2500 hours minimum. An observed MTBF (obtained by dividing the total operating time by the
number of chargeable failures) of 250 hours minimum shall be demonstrated.
4.4.3.3
Production Phase
4.4.3.3.1
Reliability Demonstration Test
Logic Units 1, 2, 3, and 4 - Four Logic Units (1, 2, 3, and 4)
4.4.3 .3.1.1
from one system shall be subjected to a Reliability Demonstration Test for a period of operating time
equal to the specified MTBF. The Accept criterion shall be seven or fewer relevant failures; the-Reject
criterion shall be eight or more relevant failures.
4.4.3.3.2
Reliability Production Test
Reliability Production Acceptance (Sampling) Phase Tests -
4.4.3.3.2.1
The equipment, throughout production, shall be tested as outlined in MIL-STD-781 (as modified herein)
under the section entitled "Production Acceptance (Sampling) Phase of Production Reliability Tests".
Test levels shall be as specified in 4.4.3.1.1.
All Equipment Test - Each equipment produced except those
4.4.3.3.2.2
submitted for the Reliability Qualification Test, shall be tested for a minimum of 100 hours. Prior to
the 100 hour test on each equipment, a burn-in period may be used at the option of the contractor. If
the burn-in period is to be used the details thereof must be included in the approved test procedures.
The last 50 hours of this All Equipment Test shall be accomplished failure free.
To determine whether the MTBF is being met at any time
during the contract the operating test hours and the failures therein (not counting burn-in failures or
burn-in operating time) shall be totaled and the results compared with the reject line of Test Plan II of
MIL-STD-781. (Extend the line as necessary to accommodate the data. ) These totals shall accumulate
so that at any one time the experience from the beginning of the contract is included. At the conclusion
of each month the test results shall be sent to the procuring activity and to the Naval Air Systems
Command, Attention: Avionics Division. At any time that the current totals of test hours and test
failures plotted on Test Plan II curves show a reject situation, the procuring activity shall be notified.
The procuring activity reserves the right to stop the acceptance of equipment at any time that a reject
situation exists pending a review of the contractor's efforts to improve the equipment, the equipment
parts, the equipment workmanship, etc. , so that the entire compilation will show other than a reject
decision.
Reliability Engineering Analysis - Forty working days prior to
4.4.4
the initiation of the releiability test, the contractor shall submit for approval, to the procuring agency,
an analytical reliability analysis of the equipments. The analysis shall show as a minimum the electri-
cal and thermal stress on each part, failure rates of parts, safety margins for parts, and environ-
mental effects on parts. Supporting failure rate data and curves shall be submitted with the analysis.
322
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