Common Mode Analysis

[MIL-STD-882D:] “The objective of system safety is to achieve acceptable mishap risk through a systematic approach of hazard analysis, risk assessment and risk management.”

In military style system safety programs, the “systematic approach” is guided by the following eight step iterative process:

  1. Document the system safety approach.  This typically entails the preparation, review and approval of a system safety program plan (SSPP) intended to:
    • document the system safety organization and how it is integrated into the engineering organization as well as the project team.
    • describe the background and experience of the system safety personnel who will be responsible for performing the analyses, recommending derived safety requirements and special safety tests, flowing down safety requirements to subcontractors, preparing contractual safety data items, etc.
    • list the system safety milestones and deliverables and ensuring that adequate system safety manpower has been allocated to meet the planned schedule.
    • identify each hazard analysis and mishap risk assessment process that will be used.
    • articulate how various hazards and residual mishap risk will be communicated to and accepted by the appropriate risk acceptance authority.
  2. Identify hazards, e.g. by analyzing hardware, software, operational profile, environment, historical data and lessons learned, etc.
  3. Assess the mishap risk in terms of severity and probability.
  4. Identification and selection of the best hazard mitigation action(s) to be implemented to eliminate or control the risks.  The order of precedence for the selection of mitigation measures is:
    1. Design changes
    2. Safety devices
    3. Warning devices
    4. Procedures and training
  5. Reduction of mishap risk to an acceptable level.
  6. Verification that mishap risk has been eliminated or controlled acceptably.
  7. Presentation of the residual risks to the appropriate authority and their acceptance thereof.
  8. Tracking of hazards, their closures and residual mishap risk(s).