MIL-PRF-28776F
e.
Requirements for groups B and C are met (where applicable).
f.
The records of all FR tests combined substantiate that the "L" (3.0 percent), "M" (1.0 percent), or "P" (0.1
percent) FR levels have been maintained or that the manufacturer continues to meet the "R" (0.01 percent)
FR level for which qualified, although the total component cycles of testing do not, as yet, meet the
If group C test requirements were not met and the manufacturer has taken corrective action satisfactory to the
Government, the forwarding of the verification of qualification report may be delayed until within 60 days after
completion of retesting of the group C inspections. In this case, the qualifying activity shall be notified of this
condition within the time the original verification of qualification report was due. All reports shall be certified by a
responsible company official. In the event that no production occurred during a 6-month reporting period, the
manufacturer shall notify the qualifying activity the company still has the capabilities and facilities necessary to
produce the relay. If during two consecutive reporting periods there has been no production, the manufacturer may
be required, at the discretion of the qualifying activity, to produce test samples to perform all group B and C tests.
4.6 FR level determination. Determination of FR levels shall be based upon information from all completed life
tests. Information for determination of FR levels shall be accumulated in the following manner:
a.
The qualification test samples.
b.
Test on every production lot which has been submitted for group B conformance inspection.
c.
Test results of relays which have a similar internal design and construction, same production processes,
same or higher environmental capability, and same electrical characteristics as the qualified relay and
which have been tested in accordance with the group B conformance inspection conditions. These relay
types must be reviewed and approved by the qualifying activity prior to being considered as acceptable
relays for use in obtaining FR information.
4.6.1 FR level computation. For this computation, a sample unit which fails at any given cycle shall be classed as
a failure for all subsequent measurements. However, the contractor, at his option, may physically remove failed
sample units from the test. If a failed sample unit is not removed, the cycles accumulated subsequent to its failure
shall not be counted toward the cumulative component cycles shown on record form.
4.6.1.1 Contact FR computation. The information from tests shall be recorded in such a manner so that, if
necessary, it can be analyzed to compute contact FR.
TABLE III. Requirements for qualification and extension of qualification to lower (better)
failure rate levels (90 percent confidence level).
Cumulative unit cycles in millions
FR
Qualified FR
level
( % / 10,000 cycles)
1/ C = 0
C=1
C=2
C=3
C=4
C=5
symbol
L
3.0
0.767
1.30
1.77
2.23
2.66
3.09
1.0
M
2.30
3.89
5.32
6.68
7.99
9.27
P
0.1
23.0
38.9
53.2
66.8
79.9
92.7
R
0.01
230.0
389.0
532.0
668.0
799.0
927.0
1/ C = Acceptance number or number of failures permitted. C numbers greater than five shall be
coordinated and approved by the qualifying activity.
17
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