Simulation Quick Calculation Pad (QCP)

The simulation Quick Calculation Pad (QCP) provides you with a quick and accurate way of gaining access to some of the most frequently requested reliability results for simulation diagrams and phase diagrams. You can access the simulation QCP by choosing Simulation > Simulation > Simulation QCP or by clicking its icon on the Simulation page of the diagram control panel.

The simulation QCP extracts the parameters and other information from the active RBD, fault tree or phase diagram and returns results based on the diagram and, when applicable, your inputs.

Under the log display, you can also click Feed to "advance the tape" or Clear to delete all data from the current log. If you click inside the log, you can copy some or all of the text to the Clipboard.

Calculates the probability that the system is operational (not failed or undergoing repair) when it is requested for use at a certain point in time. Enter the time at which you wish to calculate the point availability in the Mission End Time field. The mission is assumed to start at time = 0.

For example, a system with a point availability of 90% for a mission end time of 100 hours means that the system is expected to be available for use 90% of the time for a period of 100 hours. In other words, the system is up and running 90 times out of 100.

Calculates the probability that the system will be failed or undergoing repair when it is requested for use at a certain point in time. Enter the time at which you wish to calculate the point unavailability in the Mission End Time field. The mission is assumed to start at time = 0.

The point unavailability is the inverse of the point availability. For example, a 10% point unavailability is equivalent to a 90% point availability.

Calculates the probability that the system will operate without failure for a given period of time. Note that this is similar to point availability except that it is assumed that the system has not had a single failure. Other (non-failure) downtime events are also ignored. Enter the time at which you wish to calculate the point reliability in the Mission End Time field. The mission is assumed to start at time = 0.

For example, a reliability of 90% for a mission end time of 3 years means that if 100 identical systems are fielded, then 90 of them will still be operating at the end of 3 years.

Calculates the probability that a system will be failed in a given period of time. Enter the time at which you wish to calculate the probability of failure in the Mission End Time field. The mission is assumed to start at time = 0.

Probability of failure is also known as unreliability and it is the inverse of the reliability. For example, a point probability of failure of 10% for a mission end time of 3 years is equivalent to a 90% reliability.

Calculates the average availability (i.e., uptime divided by operating time) of the system at the specified time. This is a metric that reflects the average probability, up to that point in time, that the system is operational (not failed or undergoing repair) when it is requested for use during the simulation. Enter the time at which you wish to calculate the mean availability in the Mission End Time field. The mission is assumed to start at time = 0.

Calculates the average probability, up to the specified time, that the system will be failed or undergoing repair when it is requested for use during the simulation. It is the inverse of the mean availability. Enter the time at which you wish to calculate the mean unavailability in the Mission End Time field. The mission is assumed to start at time = 0.

Calculates the time at which a specified availability value will be achieved. Enter the availability goal in the Required Availability field.

Calculates the time at which a specified reliability value will be achieved. Enter the reliability goal in the Required Reliability field.

Calculates the mean time to first failure for the repairable system in the diagram. This is the average of the times at which the first system failure occurred for each simulation. Note that when the simulation end time is much less than the time to first failure for the system or when no system failures are observed, the calculation assumes a constant failure rate in order to obtain the MTTFF. If the system does not have a constant failure rate, the simulation end time should be set to a value that is well beyond the MTTF (mean time to failure, as computed analytically) of the system in order to obtain a realistic estimate. As a general rule, the simulation end time should be at least three times larger than the MTTF of the system.

Note: The mean time to first failure is a performance index and does not provide any information about the behavior of the failure distribution of the system.