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The explanation of a False Alarm inopportunely is dependent upon your particular perspective. In general context, it is the indecorous reporting of a failure to the operator of the equipment or system. In tackling the world of possibilities that could compromise the proper reporting of a failure, DSI has come over one specific cause and the primary contributor to the experience of False Alarms, which is the Diagnostic-Induced False Alarms, or more simply Diagnostic False Alarms.
Diagnostic False Alarms
The text book example of a Diagnostic False Alarm is, for instance, when the diagnostic equipment (usually, on-board BIT) misreports the functional status (test results) of whatever the sensor is developed to be finding in its Test Coverage. If the sensor itself was really failing while the sensed function was basically correctly working, then this would be a textbook case of a diagnostic-induced false alarm. These will generally the outcome when any sensor is in diagnostic ambiguity with the function of the hardware it was supposed to be sensing. As a result, the diagnostic design was inadequate and thus unable to isolate the hardware function from the faulty sensor.
A False Alarm rate, like any metric based upon generating values using a measurement of rate, is more suitably considered using a stochastic means, thus depicting random variables and any vicissitudes likely to happen over time.
The Diagnostic False Alarm rate is a metric that considers both the diagnostic integrity of the design, and the sustainment lifecycle by using feigning the eXpress Diagnostic Design of the fielded system in the STAGE operational support simulation environment.
Although a conventional deliverable of a Testability or Reliability examination product may give a blushing picture of a designs diagnostic, reliability or maintainability shrewdness, the actual experience in the sustainment lifecycle could be alarmingly conflicting. For instance, designs that are considered as meeting product assessment criteria in such areas as FD/FI, FA, FSA, MTBF, MTBUM, etc., may lead to disturbing and opposite outcomes in a diagnostic simulation.
Many findings evolve when diagnostic restraints are considered in simulation that depiction, for example, the incapability to isolate between critical failures modes at lower levels of the design, as discussed above. Given that, there are various intrinsic operational and diagnostic expectations that are unknowingly overlooked in any design-based assessment product that fails to consider the diagnostic impact upon the support of the fielded design over time. The STAGE simulation seamlessly reveals such limitations, and expectantly early enough in design development to impact design decisions to augment sustainment effectiveness and value.
When components are being replaced in any maintenance process, the federation of the design of components may shine in solving one design goal but may be a major cost stimulant in sustainment. This generally caused by such corrective actions that resort to replacements of non-failed components along with presumed-to-be-failed components due to lack of unambiguous isolation means. Diagnostic ambiguity results when the Diagnostic Integrity of the design (net Test Coverage) is not well defined. In eXpress, the Test Coverage can be exhaustively validated early in design development or at any time during the product lifecycle(s).
