QCP Calculations for Parametric RDA
The parametric RDA folio includes a Quick Calculation Pad (QCP)
for computing useful metrics. You can access the QCP by choosing
Recurrent Event Data > Analysis
> Quick Calculation Pad or by clicking its icon on the
Main page of the 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).
Failure Intensity
Cumulative Failure Intensity
Calculates the average rate of occurrence
of failures from time = 0 up to a specified end time. Enter
the end time in the Time field. For example, a cumulative failure intensity
of 0.15 for a time period of 100 hours means that, on average,
0.15 failures occurred every hour over the 100-hour period.
Instantaneous
Failure Intensity
Calculates the rate of occurrence
of failures over a small interval dt
that begins at a specified time. Enter the time in the Time field. For example,
an instantaneous failure intensity of 0.15 at 100 hours means
that, over the next small interval dt
that begins at 100 hours, the rate of occurrence of failures
is 0.15 failures per hour.
MTBF (Mean Time Between Failures)
Cumulative
MTBF
Calculates the average MTBF from time
= 0 up to a specified end time. Enter the end time in the
Time field.
For example, a cumulative MTBF of 5 hours from 0 to 100
hours means that, on average, the time between failures was
5 hours over the 100-hour period.
Instantaneous
MTBF
Calculates the average MTBF over a
small interval dt
that begins at a specified time. Enter the time in the Time field. For example,
an instantaneous MTBF of 5 hours at 100 hours means that,
over the next small interval dt
that begins at 100 hours, the average MTBF will be 5 hours.
Note:
MTBF is used as a metric for the analysis of repairable components.
On the other hand, the term mean
time to failure (MTTF) is used as a metric for non-repairable systems,
where components are discarded or replaced upon failure. To
analyze non-repairable system data in Weibull++, use the Weibull++ life data folio.
Failures
Cumulative
Number of Failures
Calculates the cumulative number of
failures to be expected for a specified interval of time.
Enter the start time of the interval in the Mission
Start Time field and enter the duration of the interval
in the Mission Additional
Time field. For example, a system may be estimated
to fail 10 times between 100 and 500 operating hours.
Failures
by System
Calculates the cumulative number of
failures to be expected for each system for a specified interval.
The start time of the interval is equivalent to the time when
the observation period for the system ended (indicated by
an E in the folio data sheet). If you did not enter an end
time for a system, then the start time of the interval is
assumed to be equal to the last failure time for that system.
Enter the duration of the interval in the Mission
Additional Time field and then click Calculate
to open the Results window, which shows the cumulative number
of failures for each system, as well as the overall number
of failures.
Probability
Conditional
Reliability
Calculates the probability of the
system successfully completing a mission, given that it may
or may not have successfully completed a previous mission.
Enter the start time of the new mission in the Mission
Start Time field and enter the duration of the new
mission in the Mission Additional
Time field.
For example, a system failed three
times during its first three years of operation. The probability
that the system will operate for an additional six months
without failure, or the conditional reliability for one half
of a year given that the system is three years old, may be
30%.
Conditional
Probability of Failure
Calculates the probability that the
system will fail a mission, given that it may or may not have
successfully completed a previous mission. Enter the start
time of the new mission in the Mission
Start Time field and enter the duration of the new
mission in the Mission Additional
Time field.
For example, a system failed three
times during its first three years of operation. The probability
that the system will fail in the next six months, or the conditional
probability of failure for one half of a year given that the
system is three years old, may be 70%.