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

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.

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)

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.

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++ standard folio.

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.

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

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%.

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%.