Definition:
A Systematic Failure involves the system itself and a particular condition. These are failures related to design, implementation, or management errors rather than random hardware faults. This is often a software failure. This can be thought of as a design failure or a design flaw.
This is tied to the concept of systematic compatibility and route “S”. These are not random and thus have no “systematic failure rate.”
Within functional safety, all failures are either systematic or random failures.
Key Points:
- Must be addressed through processes like FSM and quality assurance.
- Different from random failures that are statistically modeled.
- Much of IEC 61508 is focused on removing these.
- Can be eliminated after detection by changing the design.
- A proof test would not generally find these types of failures.
Example:
A software bug causing all sensors to report wrong values is a systematic failure. A valve failing to operate in freezing conditions when it should have been expected to operate is a design flaw and thus a systematic failure.
See Also: systematic capability, random failures
Cited Source:
- IEC 61508-4:2010, Clause 3.6.9
- IEC 61511-1:2016, Clause 3.2.81
- NTNU Norwegian University of Science and Technology – training slides on failure classification