Safety

Question 1

Life-critical system

Answer 1

Failure of malfunction of such a system could result in
• death or serious injury to people
• loss or severe damage to equipment
• environmental harm

Question 2

Safety engineering

Answer 2

Assures that a life-critical system behaves as needed even when components fail
=> provides acceptable levels of safety

Question 3

Probabilistic risk assessment

Answer 3

Way to express the expected loss : sum of all the consequences multiplied by their probabilities
• magnitude of the possible adverse csq = numerical
• likelihood of occurence

Question 4

Fail-operational

Answer 4

Continue to operate when control system fails
Decrease the functionnality
Ex: elevators

Question 5

Fail-safe

Answer 5

Become safe when cannot operate

Ex: door unlock, railway signals

Question 6

Fail-secure

Answer 6

Maintain maximum security when cannot operate

Ex : prison door lock

Question 7

Fail-passive

Answer 7

Continue to operate -> handing control over to an operator

Ex : aircraft autopilot

Question 8

Fault-tolerant

Answer 8

Avoid service failure when faults are introduced in the system
Don’t need to switch the system off, replacement of the component before failure

Question 9

Safety

Answer 9

Protection against natural accidents : earthquakes, fire…

Question 10

Security

Answer 10

Protection against people with the attention of harming : terrorists