which of the following is not an example of a safety–critical system course hero

What is fail safe?

Fail-safe systems become safe when they cannot operate. Many medical systems fall into this category. For example, an infusion pump can fail, and as long as it alerts the nurse and ceases pumping, it will not threaten the loss of life because its safety interval is long enough to permit a human response. In a similar vein, an industrial or domestic burner controller can fail, but must fail in a safe mode (i.e. turn combustion off when they detect faults). Famously, nuclear weapon systems that launch-on-command are fail-safe, because if the communications systems fail, launch cannot be commanded. Railway signaling is designed to be fail-safe.

What is fail soft system?

Fail-soft systems are able to continue operating on an interim basis with reduced efficiency in case of failure. Most spare tires are an example of this: They usually come with certain restrictions (e.g. a speed restriction) and lead to lower fuel economy. Another example is the "Safe Mode" found in most Windows operating systems.

What is mission critical engineering?

Mission critical – Factor critical to the operation of an organization. Reliability engineering – Sub-discipline of systems engineering that emphasizes dependability in the lifecycle management of a product or a system. Redundancy (engineering) – Duplication of critical components to increase reliability of a system.

What is fault tolerant aircraft?

Fault-tolerant systems avoid service failure when faults are introduced to the system. An example may include control systems for ordinary nuclear reactors.

How to tolerate a fault?

The normal method to tolerate faults is to have several computers continually test the parts of a system, and switch on hot spares for failing subsystems. As long as faulty subsystems are replaced or repaired at normal maintenance intervals, these systems are considered safe.

Why was nuclear launch on loss of communications rejected?

Nuclear weapons launch-on-loss-of-communications was rejected as a control system for the U.S. nuclear forces because it is fail-operational: a loss of communications would cause launch, so this mode of operation was considered too risky.

What is redundancy in engineering?

Redundancy (engineering) – Duplication of critical components to increase reliability of a system. Factor of safety – Factor by which an engineered system's capacity is higher than the expected load to ensure safety in case of error or uncertainty. Nuclear reactor – Device used to initiate and control a nuclear chain reaction.

What is a very general directive that does not directly apply to any specific situation in a code of ethics?

A very general directive that does not directly apply to any specific situation in a code of ethics is a (n) of a professional code of ethics.

What does "never held morally responsible" mean?

B. A person is never held morally responsible, whether he intended for an action to occur or not.

Do codes of ethics have anything to do with whistleblowing?

D. Codes of ethics have nothing to do with whistle-blowing situations. A. If all employees ideally follow the code of ethics and act ethically, then the number of cases in which whistle-blowing is needed will be reduced. Upgrade to remove ads.

Is a code of ethics incomplete?

Members of a profession may have to seek guidance elsewhere for a common problem. D. Codes of ethics are typically not incomplete, as they provide guidance for all common problems a professional may face. not C.

What is secondary safety critical system?

Secondary safety critical systems: These are the system whose failure results in faults in other systems which can threaten the users of the system.

How is safety achieved in a system?

Safety in a system can be achievement by using various ways: Hazard Avoidance: The system is designed so that some classes of hazards cannot arise. Hazard Detection and Removal: The system is designed so that hazards are identified and deleted before the system meets any accidental failure or damage.

What is the difference between risk and hazard?

Hazard Probability: It is the probability of the event occurring which create a hazard. Probability values ranges from probable to unbelievable. Risk: It is a probability that a system will cause an accident. The risk is assessed by considering the hazard probability and hazard severity.

What is the definition of hazard severity?

Hazard Severity: It is an assessment of the worst possible damage that could result from a particular hazard. For example, many people are killed just only due to minor damage.

What is the extent to which a system can be adapted to new requirements?

Repairability: It is the extent to which the system can be repaired in the event of failure. Maintainability: It is the extent to which a system can be adapted to new requirements. Survivability: It is the extent to which a system can deliver services under the condition of an accidental attack.

What is damage control?

Damage Control: The system contain protection features that minimize the damage that may occur due to hazard.

What is an accident?

Accident: It is an unexpected event that results in human death or injury, damage to property or to the environment. For example, A computer controlled machine injuring its operator.

What is safety critical system?

A safety critical system is one which can have catastrophic consequences if it fails. So far we have been talking about productivity; the amount of a value a system adds. In the world of safety critical systems ‘reliability' is crucial. Reliability is a measure of how often and how dramatically a system fails.

Why are users not included in safety analyses?

Safety analysts like dealing with numbers. Given a piece of hardware they like to know how many times it is likely to breakdown in the next ten years, and the chances are there will be data available to tell them. They like to the know the cost of that piece of hardware breaking down, and there may also be data telling them this too. They can then multiply the cost of breakdown by the number of times breakdown will occur and produce a quantitative estimate of how much running that piece of hardware for the next ten years will cost.

How do safety engineers work?

Safety engineers collect and analyse a huge amount of data about the technology they use to build safety critical systems. The hardware which they use will be highly tested with known and documented failure tolerances. The use the most secure software development techniques in order to ensure that requirements for the system are collected and that those requirements actually reflect what is wanted for the system (requirements gathering is a notoriously tricky business). Then software is rigorously developed to meet those requirements. At all stages in the process thorough testing and validation is employed. The engineers expend prodigious effort in ensuring that they ‘build the right system, and the system right'. Many experts with experience of systems similar to the one being developed are consulted and a considerable amount of time and money is expended in order to get a system that is certifiably and explicitly correct.

Can you answer questions about human behaviour?

Because questions about human behaviour cannot generally be given in a yes or no way, this does not mean however that no answers can be given. Psychology has developed many models of human behaviour that accurately describe and predict human performance. In particular there are many valid models of human perception that could have pointed to problems with the display configuration in the cockpit of the airliner that crashed near Kegworth.

Do safety critical systems take their users into account?

But many safety critical systems are put in place which do not take their users into account at all. Not only should users be brought into safety analyses, but also much more detail about the environment that is part of the system needs to be considered.

Do developers consider users to be external to their systems?

When questioned it is clear that many developers do not consider users to part of the systems they develop; they consider users to be external to their systems. Therefore when users cause errors, the blame for the error lies comfortably outside their system.

What is a safety critical system?

Safety-critical systems, also called life-critical systems, are computer systems that can result in injury or loss of life if it fails or malfunctions. These systems can also cause harm to other equipment or the environment in the event of failure. People use safety-critical systems every day; for example: in phones, in cars, in computers, ...

Why do safety critical systems need the best quality software?

Safety-Critical Systems need the best quality software because lives depend on them working correctly.

What is system safety?

A main topic in System Safety is the avoidance of hazards or any condition that threatens the safety of any users. The rate of occurrence and the severity of these hazards factors into how much risk can be tolerated. A hazard can be anything that can lead to an accident, develop into an accident, or anything likely to become dangerous when interacted with. If there is significant risk due to severity or frequency of a particular hazard than risk reduction measures must be implemented in order for a risk to become tolerable. [5]

What is the first step in a system development process?

The first step in development is approaching the system requirements, usually those specified by the target consumers of the system. A functional requirements document must be written up that specifies exactly what this system attempts to accomplish. Afterwards the requirements of the system are analyzed to identify risks and potential hazards related to the system. This also outlines what the system must do or not do for the sake of safety. At this time designers try to anticipate every situation the system may encounter. These documents must be concise about how the system will completely fulfill the requirements so that the programmers can clearly understand what is needed. This can be a difficult process as specifications can often be misinterpreted. Ideally specifications must be: correct, complete, consistent, and unambiguous. Faults in these documents are one of the greatest problems during development. The documents might not be adequate or they might not effectively address the customer’s desired requirements. [1]

Why is safety engineering important?

It is important that in these systems, safety is designed into the product rather than it being an afterthought. Simplifying these types of systems is bad as it increases the opportunity for a single component’s malfunction to cause a system wide failure. Small errors in a system can rapidly develop into a system wide failure that creates hazards. In many ways it can be difficult for people to decide when these systems become truly safe enough for widespread use. [2, 3]

How have computers prevented accidents?

Fortunately, regulations, better development techniques, and cautious usage of computers have prevented many accidents from occurring in recent years. There are still difficulties in this field. Consumers desire systems that are safe and easy to use; and developers want systems that are easier to design, create, and repair. It can be difficult to find a happy medium, and the produced systems often are poorly matched to the user’s needs. In many situations the systems being used are complicated and difficult to use for anyone who does not understand how the technology works. The people who depend on these systems to work correctly have many other things to worry about, and a complex machine can add more strife to these situations. Today, many work to create more effective and efficient safety-critical systems. Not only are lives depending on doctors and pilots, they are depending on engineers and programmers as well. [3]

What is a fail operation system?

Fail-operational systems - These types of systems will continue to operate even if their control systems fail. An example would be an automatic landing system if, in the event of a failure, the approach, flare and landing can be completed by the remaining part of the automatic system.

Overview

Reliability regimes

Software engineering for safety-critical systems

Examples of safety-critical systems

See also

External links