How would you perform a fault tree analysis for a mission computer subsystem, and what are typical top-level failure modes?

How would you perform a fault tree analysis for a mission computer subsystem, and what are typical top-level failure modes?

• A. Identify hardware failures only, ignoring software.
• B. Build a fault tree that maps how basic failures can lead to top-level failures such as processor, memory, interconnect, power, software, sensors, and actuators.
• C. Focus exclusively on human error and training.
• D. Use only qualitative assessment without logic.

Answer: (B)

Fault tree analysis is a structured, logic-based way to trace how basic failures can combine to cause a system-level failure. For a mission computer subsystem, you start from potential top-level failure modes and work backward to the basic events that could cause them. Building a fault tree that maps how these basic failures can lead to top-level failures such as processor, memory, interconnect, power, software, sensors, and actuators gives a complete picture of where faults originate and how they propagate through the system. This approach is essential because a mission computer relies on both hardware and software cooperating smoothly, and failures can stem from interactions between components, not just a single fault in isolation. Including software as a top-level failure path recognizes faults in firmware, software logic, or interface code that can bring the computer down just as hardware faults can. A fault tree also helps reveal redundancy gaps and mitigation ideas—watchdogs, redundant paths, safe-state logic, or fault containment strategies—that reduce the risk of a top-level failure. Focusing only on hardware would miss critical software fault paths, which are a real and common source of system failure. Relying on human error or training alone ignores the actual mechanical and software failure channels the system may encounter. And using qualitative assessment without the logical structure of a fault tree would not provide the clear cause-effect relationships needed to quantify risks or prioritize mitigations.

Fault tree analysis is a structured, logic-based way to trace how basic failures can combine to cause a system-level failure. For a mission computer subsystem, you start from potential top-level failure modes and work backward to the basic events that could cause them. Building a fault tree that maps how these basic failures can lead to top-level failures such as processor, memory, interconnect, power, software, sensors, and actuators gives a complete picture of where faults originate and how they propagate through the system. This approach is essential because a mission computer relies on both hardware and software cooperating smoothly, and failures can stem from interactions between components, not just a single fault in isolation. Including software as a top-level failure path recognizes faults in firmware, software logic, or interface code that can bring the computer down just as hardware faults can. A fault tree also helps reveal redundancy gaps and mitigation ideas—watchdogs, redundant paths, safe-state logic, or fault containment strategies—that reduce the risk of a top-level failure.

Focusing only on hardware would miss critical software fault paths, which are a real and common source of system failure. Relying on human error or training alone ignores the actual mechanical and software failure channels the system may encounter. And using qualitative assessment without the logical structure of a fault tree would not provide the clear cause-effect relationships needed to quantify risks or prioritize mitigations.