Difficulty of Detection

Difficulty of Detection (D) refers to the relative difficulty of detecting a failure of a flow property. FMECA standards typically refer to Difficulty of Detection as "detectability" however this requires an inverse ranking scheme since high detectability leads to low criticality.

To avoid confusion, MADE uses Difficulty of detection which is more consistent with the criticality ranking.

Difficulty of Detection Ranking

The table below shows an example of Difficulty of Detection rankings from an aviation standard and their associated linguistic categories and descriptions.

Ranking	Category	Description
10	Non-detectable	Non-detectable or only detectable by destructive/physical inspection.
7 - 9	Ground Inspection	Detectable only by disassembly and NDI.
4 - 6	Ground Inspection	Detectable by ground-based testing & diagnostics (non-destructive).
2 - 3	In-flight test	Detectable by real-time system test/check.
1	Continuously observable	Automatic detection by BIT/sensor.

Assignable Rankings	Unassignable Rankings
Pair Flow Property	Causes
Components Flow Property	Mechanisms
Subsystems Flow Property	Faults
Systems Flow Property

Note: Difficulty of Detection values are duplicated for all failure responses (high/low)

Assigning Difficulty of Detection Rankings

Follow the steps below to assign Difficulty of Detection Rankings to Flow Properties in a model:

1. Open the Failure Diagram for an element or open the Criticality Viewer.
2. Select a failure concept on the Failure Diagram or from the Criticality Viewer window.
3. Select the Criticality tab in the Properties View.
4. Use the slider bar to change the value or enter your own value in the provided text field.