Which statement best differentiates a hard fault from a soft fault in onboard BIT tests?

Which statement best differentiates a hard fault from a soft fault in onboard BIT tests?

• A. Hard faults are intermittent and may clear with power cycling; soft faults are persistent.
• B. Hard faults are transient; soft faults are always permanent.
• C. Hard faults are persistent and definite; soft faults are intermittent and may clear with power cycle or environmental changes.
• D. Hard faults only occur during maintenance; soft faults only occur in flight.

Answer: (C)

In onboard BIT tests, the key distinction is how long the fault lasts. A hard fault is a true hardware failure that remains present until it’s repaired; it is persistent and definite, not something that goes away on its own. A soft fault is temporary and intermittent, often caused by marginal signals or environmental conditions, and it can clear with a power cycle or after conditions change. That’s why the statement describing hard faults as persistent and definite and soft faults as intermittent and possibly resolving with power cycling or environmental changes is the best fit. The other ideas mix up persistence, or claim faults only happen in certain phases, which isn’t how BIT faults are understood.

In onboard BIT tests, the key distinction is how long the fault lasts. A hard fault is a true hardware failure that remains present until it’s repaired; it is persistent and definite, not something that goes away on its own. A soft fault is temporary and intermittent, often caused by marginal signals or environmental conditions, and it can clear with a power cycle or after conditions change. That’s why the statement describing hard faults as persistent and definite and soft faults as intermittent and possibly resolving with power cycling or environmental changes is the best fit. The other ideas mix up persistence, or claim faults only happen in certain phases, which isn’t how BIT faults are understood.