WF61: Perform Functional Hazard Assessment

Pre-Requisites

• A. Prepare Functional Hazard Assessment: to define all the failure condition(s) and multiple failure event(s) and assign mission profile and safety criteria (see WF37).
• B. Assumptions: to define assumptions in Project Preferences relating to the functional model (see WF62). One assumption can be associated with multiple failure conditions.
• C. Criticality Profile: to define Severity Classes based on definitions and rules specified. Severity Classes are assigned a Development Assurance Level (DAL). Profiles are managed within the Criticality Profile Editor.
• D. Control Measures: to define control measures in Project Preferences relating to the functional model (see WF63). One control measure can be associated with multiple failure conditions.
• E. Substantiation Actions: to define substantiation actions in Project Preferences relating to the functional model (see WF65). One substantiation action can be associated with multiple failure conditions.

Detailed Steps

1. Assign Assumptions relating to the selected failure condition/multiple failure event.
2. Decision — All Assumptions assigned? If no, continue assigning assumptions to the selected failure condition/multiple failure event; create new assumptions in Project Preferences (see WF62). If yes, proceed to Step 3.
3. Assess Failure Effects — provide overall effect of the selected failure condition/multiple failure event for each of the assigned mission section(s) in Step 7 of WF37.
4. Decision — Assess effects on Aircraft/Crew/Occupant? If yes, proceed to Step 4a. If no, proceed to Step 5. 4a. Create new failure effect categories (up to 3 additional categories) in Project Preferences > Functional Hazard Assessment > Failure Effects. The newly created categories appear throughout the Functional Diagram. Define narratives for these categories in Step 3 for each of the assigned mission section(s) in Step 7 of WF37.
5. Assess Initial Criticality — define Initial Criticality details (before applying any Control Measure(s)) by selecting the Severity Class and Maximum Probability of the selected failure condition/multiple failure event. The Criticality Profile is pre-selected based on the active profile of the project, which dictates the Development Assurance Level (DAL) classifications based on the selected Severity Class. Use the Annotation narrative to provide further information.
6. Assign Control Measures — assign actions taken to mitigate the selected failure condition/multiple failure event. Create new control measure(s) in Project Preferences (see WF63).
7. Assign Revised Criticality — define revised Criticality details by selecting the Severity Class and Maximum Probability of the selected failure condition/multiple failure event when the associated mitigating actions are implemented. Use the Annotation narrative for further information.
8. Assign Substantiation Actions to the selected failure condition/multiple failure event. Link assumptions associated with the selected failure condition/multiple failure event, if applicable.
9. Decision — All Substantiation actions assigned? If no, continue assigning substantiation actions; create new substantiation actions in Project Preferences (see WF65). If yes, proceed to Step 10.
10. Decision — All Failure Conditions Defined? If no, continue creating and defining failure conditions/multiple failure event for selected functional failure in Step 4 of WF37. If yes, proceed to Step 11.
11. Decision — All Functional Failures Defined? If no, continue creating and defining functional failures for selected internal/external function in Step 3 of WF37. If yes, proceed to Step 12.
12. Decision — All Functions Defined? If no, continue assessing all the internal and external functions of the functional diagram in Step 2 of WF36. If yes, proceed to Step 13.
13. The Functional Hazard Assessment (FHA) has been performed and a summary of the assessment can be viewed in the Functions List of the Functional Diagram Editor or as a report.
14. Link all internal functions of the functional diagram to the functions of the system model (see WF68). Single failure conditions associated with functions will be linked to the failure diagram of the system model.

Screen-by-screen detail (from embedded screenshots)

• Step 1: Assign Assumptions — In the "Vehicle System" editor's Functional Diagram / Domain Editor, left nav includes Functional Diagram, Mission Profile, Events & Conditions, Safety Criteria, Failure Effect, Criticality, Control Measures, Revised Criticality, Assumptions, Substantiation Actions. Under "Assumptions": "Failure Conditions" table (Failure Condition, Failure Condition Type, Mission Sections, Overall Effect) and below "Assumptions" panel showing linked assumptions (ID, Name, Description, Failure Condition Property, Comments, Remarks, Documents) with a '+' to open the "Assumptions" picker dialog listing available assumptions (ID, Name, Description, e.g. ASM_01 "Engine's horsepower and torque", ASM_02 "Fuel efficiency") with Select All/Deselect All and OK/Cancel.
• Step 3: Assess Failure Effects — Left nav "Failure Effect" section: "Failure Conditions" table (Failure Condition, Mission Sections, Overall Effect, Initial Severity, Revised Severity) and below "Failure Effect" panel with a Mission Profile dropdown (e.g. "Regular Trip") and a Mission Profile/Section tree (Start-up, Ignition, Acceleration, Cruise, Turning, Cruise 2, Highway/Highway A1/Highway B2, Mountain Terrain, Deceleration, Shut-down) each with an editable "Overall Effect" cell.
• Step 4a: Create columns for Aircraft/Crew/Occupant — Main menu: Preferences > Project Preferences > Functional Hazard Assessment > Failure Effects. "FHA Failure Effects custom columns" table lets you define up to 3 custom columns via the green '+' — "Create custom Failure Effect column" dialog: Column radio (Effect on Aircraft / Effect on Crew / Effect on Occupants / Custom), Name, Description fields. After Apply and Close, the new columns (e.g. "Effect on Crew", "Effect on Occupants", "Effect on Aircraft") appear in the Failure Effect grid alongside "Overall Effect" for each mission section.
• Step 5: Assess Initial Criticality — Left nav "Criticality" section: "Failure Conditions" table plus columns Initial Severity / Revised Severity. Below, "Criticality Profile" panel: Criticality Profile dropdown (e.g. "PHMT RPN Criticality"), Severity Class dropdown (e.g. "Moderately High", color-coded), DAL field (e.g. "N/A"), Max. Probability slider (log scale 1 to 1E-12), and an "Annotation" free-text narrative field.
• Step 6: Assign Control Measures — Left nav "Control Measures" section: below the Failure Conditions table, a "Control Measures" panel lists linked measures (ID, Name, Narrative, Type) with a '+' opening a "Control Measure" picker (ID, Name, Narrative, Type, e.g. CM_01 "Automated Power Limitation" / Safety Devices, CM_02 "Regular Maintenance and..." / Procedures) with Select All/Deselect All and OK/Cancel.
• Step 7: Assess Revised Criticality — Left nav "Revised Criticality" section: same structure as Initial Criticality but for Revised Severity — Criticality Profile, Severity Class (e.g. "Low" / "Very Low"), DAL, Max. Probability slider, Annotation ("Narrative for revised criticality assessment").
• Step 8: Assign Substantiation Actions — Left nav "Substantiation Actions" section: below Failure Conditions, a "Substantiation Actions" panel (ID, Name, Narrative, Type, Linked Assumptions, Attachment) with '+' opening a "Substantiation Action" picker (ID, Name, Narrative, Type, e.g. SA_01 "Engine Performance Testing"/Test, SA_02 "Combustion Process Analysis"/Analysis) with Select All/Deselect All and OK. A second dialog "Link Assumptions" lets you link an Assumption (e.g. "Engine's horsepower and torque") to the selected Substantiation Action for the given Failure Condition.

Outputs

• I. FHA Report: contains all the information defined in the Functional Diagram Editor and Failure Conditions Editor for the completion of the assessment as per EUROCAE ARP4761 Rev A.