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Safe Failure Fraction (SFF)
‣
A measure of the effectiveness of the
fail safe
design and
built-in diagnostic tests
‣
It is calculated as follows:
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‣
It is a design parameter, not an operational parameter
‣
It’s not relevant to Proof Testing (except being based on some common data)
SFF
=
λ
S
+
λ
DD
λ
S
+
λ
DD
+
λ
DU
18