Best practices matter when designing control systems
When lives depend on an automated control system, the system should fail safely. When components fail in a control system, operators should receive clear, immediate guidance on status so proper decisions can be made immediately in manual mode. If a set of circumstances could occur where the failure of one sensor causes a control system failure before operators can recover safely, then the system needs a sensor backup or two to provide data instead. Best two-out-of-three voting designs decrease risk.
Education and training matter
Information continue to emerge in the Boeing 737 Max grounding, and some details seem contrary to what was said earlier. Through it all, I keep thinking:
- People get degrees in control engineering for a reason.
- People earn safety certifications for a reason.
- Listen to people with training and experience who use standards and best practices.
- Listen to operators who know the process.
- If you see something that doesn’t seem right, and lives (and/or livelihoods) depend on it, be a whistleblower.
Before I get onto another Boeing 737 Max, I will find out if there’s a backup angle of attack sensor also delivering measurements and what happens to the control system when that sensor and/or the backup sensor fails. If I don’t like the answer, I’ll think again and book another aircraft.
Mark T. Hoske is content manager, Control Engineering, CFE Media, firstname.lastname@example.org.
KEYWORDS: Critical control systems, safety systems, single point of failure
Control system design best practices
Safety system design best practices
Be a whistleblower if something doesn’t look right.
Will you be a whistleblower when lives and/or livelihoods are on the line?
Control Engineering has many articles on related topics; it’s hard to pick a few.
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- Comparing conventional and sustainable safety instrumented systems
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- Sustainable cybersecurity architecture for safety instrumented systems