ASEP System Safety and Reliability Engineering 2 — Questions and Answers
Question 1: What does 'availability' mean in systems engineering?
- The fraction of time a system is in a functional and ready state (Correct answer)
- The number of spares held in inventory
- The probability that a system survives a hostile environment
- The time required to produce a system
Correct answer: The fraction of time a system is in a functional and ready state
Availability is the probability (or fraction of time) that a system is in an operable and committable state at any given point in time.
Question 2: In FMEA, the Risk Priority Number (RPN) is calculated as:
- Severity + Occurrence + Detectability
- Severity × Occurrence × Detectability (Correct answer)
- Severity ÷ Detectability
- Probability × Consequence only
Correct answer: Severity × Occurrence × Detectability
RPN = Severity × Occurrence × Detectability, and is used to prioritize failure modes for corrective action.
Question 3: Which reliability growth model is commonly used to track defect elimination progress during testing?
- Rayleigh model
- Crow-AMSAA model (Correct answer)
- Weibull distribution only
- Poisson distribution only
Correct answer: Crow-AMSAA model
The Crow-AMSAA (AMSAA Reliability Growth) model is widely used in the US defense and aerospace sectors to track and project reliability growth during developmental testing.
Question 4: What is 'redundancy' and how does it improve system reliability?
- Redundancy eliminates testing; it directly replaces design reviews
- Redundancy adds backup components so that if one fails, another takes over, increasing overall reliability (Correct answer)
- Redundancy reduces the number of requirements
- Redundancy is used only in software systems
Correct answer: Redundancy adds backup components so that if one fails, another takes over, increasing overall reliability
Redundancy provides backup components or subsystems so that system function is maintained even when a primary component fails, improving reliability.
Question 5: What is 'maintainability' in systems engineering?
- The probability that a system will not fail in operation
- The ability of a system to be retained in or restored to a specified condition within a given time (Correct answer)
- The number of technicians assigned to a system
- The cost of spare parts over a system's life
Correct answer: The ability of a system to be retained in or restored to a specified condition within a given time
Maintainability is the measure of the ease and speed with which a system can be restored to operational status after a failure.
Question 6: Which of the following is an example of an inherently safe design approach?
- Adding warning labels to dangerous components
- Eliminating the hazard at the source by redesigning the system (Correct answer)
- Training operators to avoid unsafe conditions
- Installing safety interlocks as a backup
Correct answer: Eliminating the hazard at the source by redesigning the system
Inherently safe design eliminates the hazard at its source through design changes rather than relying on controls, warnings, or procedures.
ASEP System Safety and Reliability Engineering 2
What does 'availability' mean in systems engineering?