Simulation Quick Calculation Pad (QCP)
BlockSim includes a Quick Calculation Pad (QCP) for computing
useful metrics. You can access the QCP by choosing Simulation
> Simulation > Simulation QCP or by clicking its
icon on the Simulation page of the diagram control panel.
To perform a calculation, select the appropriate option and
enter any required inputs in the Input
area, then click Calculate.
For more detailed information on how to use the QCP in general,
see Quick Calculation
Pad (QCP).
The following calculations are available for simulation diagrams
and phase diagrams:
Point
Availability
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.
Point
Unavailability
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.
Point
Reliability
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.
Point
Probability of Failure
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.
Mean
Availability
Calculates the average availability
(i.e., uptime divided by operating time) of the system at
the specified time. This metric 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.
Mean
Unavailability
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.
Time
for Availability
Calculates the time at which a specified
availability value will be achieved. Enter the availability
goal in the Required Availability
field.
Time
for Reliability
Calculates the time at which a specified
reliability value will be achieved. Enter the reliability
goal in the Required Reliability
field.
Time for Uptime
Calculates the time at which a specified amount of uptime will be achieved. Enter the desired amount of uptime in the Required Uptime
field.
MTTFF
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.