In these lessons comprising ‘Identify & Analyze Functional (e.g. SW) Hazards’, I deal with an important but misunderstood topic. Programmable electronics and software now run so much of our modern world. Many of the products and services they enable are safety-related. If they go wrong, people can get hurt. Yet, few engineers know how to identify and analyze the hazards that they present. Today, I will show you how.
Preliminary Hazard Identification
Hazard Identification has been defined as: “The process of identifying and listing the hazards and accidents associated with a system.”
Hazard Analysis has been defined as: “The process of describing in detail the hazards and accidents associated with a system and defining accident sequences.”
Preliminary Hazard Identification and Analysis (PHIA) is intended to help you determine the scope of the safety activities and requirements. It identifies the main hazards likely to arise from the capability and functionality being provided. It is carried out as early as possible in the project life cycle, providing important early input to setting Safety requirements and refining the Project Safety Plan.
PHIA seeks to answer, at an early stage of the project, the question: “What Hazards and Accidents might affect this system and how could they happen?”
Identify Functional Hazards
What we must do is identify functional, as opposed to physical hazards. Let me explain the difference:
- Physical hazards are basically energy and toxicity – fire, falls, electrocution, hazardous chemicals, and the like; whereas
- Functional hazards arise when a programmable electronic device commands a machine to do something hazardous or presents false, safety-related information to an operator, e.g. a pilot.
Identifying functional hazards requires us to use a special technique, like Functional Failure Analysis (FFA) or Functional Safet Analysis. I explain how to use these techniques in a video and in my PHIA Guide. Both these items are included in this course package.
Functional Hazard Analysis
In this full-length (40-minute) session, I look at Functional Hazard Analysis, or FHA, which is Task 208 in Mil-Std-882E. FHA analyses software, complex electronic hardware, and human interactions. I explore the aim, description, and contracting requirements of this Task, and provide extensive commentary on it. (I refer to other lessons for special techniques for software safety and Human Factors.)
Combine the Analyses
If we put these analysis tasks together, then we can identify which programmable elements are performing safety-related functions. We can also determine what external hazards controls are available. This tells us how much reliance we are placing on the programmable elements for safety.
Once we know the required integrity of the programmable elements, we know the required level of rigor for their development. If this is unacceptable, or we have existing software (‘COTS’ or ‘SOUP’), we can look again at external controls.
Other Courses on Software Safety
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