Session 1.5: Functional Modeling (Functional Hazards Assessment)

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Session 1.5: Functional Modeling (FHA)

SESSION 1.5 OUTLINE

1.5.1: Functional Hazards Assessment (FHA) in ARP4761 Rev A Context 1.5.2: Opening Functional Modeling Editor 1.5.3: Functional Model Editor Layout 1.5.4: Creating Functions 1.5.5: Creating Connections

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.1 FUNCTIONAL HAZARDS ASSESSMENT (FHA) IN ARP4761 REV A CONTEXT

ARP4761 Rev A Standard: Guidelines & methods of performing safety assessment for certification of civilian aircraft, systems, and equipment.

FHA Definition: A Functional Hazard Assessment is defined as a systematic, comprehensive examination of functions to identify and classify failure conditions of those functions according to their severity

   Identify Functions
   Identify Failure Conditions related to each Function
   Classify Failure Conditions by Severity

Performed during Concept and Preliminary Design Stages

FHA is performed at 2 levels: Platform (e.g. Aircraft) Level & System Level

Functions are assigned Development Assurance Levels (DALs) to classify the severity of failure effects or development errors

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.1 OPENING FUNCTIONAL MODELING EDITOR

To access Functional Diagram:

   Select `Vehicle System' in the Project Explorer
   Select Modeling  Functional Diagram from main menu
   Alternatively, right-click `Vehicle System' in Project Explorer
   Select Functional Diagram

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.2 FUNCTIONAL MODEL EDITOR LAYOUT

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.2 FUNCTIONAL MODEL EDITOR LAYOUT

The default layout of the Functional Model editor consists of:

Vertical Tabs (Left): Show Functional Model & active Failure Condition pages Functional Model canvas (Centre): The main area where Functions and Functional connections are defined Palette (Right): Contains a list of modeling tools, functional connections and function types Functions List (Bottom): A collapsible area where functions & function details are summarised Domain Editor: Option to add external events relating to the functional model

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.2 FUNCTIONAL MODEL EDITOR LAYOUT

There are two types of function blocks in the Functional Model:

   Function: Represents a description of an operation to be performed by the system
   External event: An occurrence which has its origin distinct from the aircraft of the system

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.2 FUNCTIONAL MODEL EDITOR LAYOUT

There are 6 selections in the Palette view of FHA:

   Select � used to select items on the Functional model canvas
   New Function � used to create new functions
   Import Function � used to import functions from a different hierarchy
   Import Domain Function � imports external functions onto the Functional model canvas
   Connection � creates connections and link functions

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.2 CREATE FUNCTIONS

There are two methods to create a function:

Method 1:

Select from the Palette

Select on the Functional model canvas to create a Functions on this level

Using the Properties viewer, rename the function to Control Vehicle and select AFHA Level from the drop- down

Method 2:

   Right click on the Functional model canvas

   Select New  New Function

   Using the Properties viewer, rename the function to
      Provide Thrust and select AFHA Level from the drop-
      down

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.2 CREATE FUNCTIONS

The FHA Model is a hierarchical model. Functions can be created beneath the higher-level functions. To access the lower-level FHA Model:

Double click on the Control Vehicle function to view the lower-level Functional Diagram Create the following functions under the Control Vehicle function and select AFHA Level:

   Control Vehicle Direction
   Decelerate Vehicle

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.2 CREATE FUNCTIONS (CONTINUED)

On the Vehicle System Functional Diagram, right click on the Provide Thrust function Select Functional Diagram Create the following functions under the Provide Thrust function and select AFHA Level :

   Convert Fuel to Mechanical Motion
   Distribute Mechanical Motion

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.3 EXTERNAL FUNCTION

External functions can be captured using the Domain editor. This can be accessed by selecting Domain Editor button in the top right corner of the FHA window.

The external functions can be assigned to various domains.

   By default, Environment, Human Factors and Support Systems are provided.

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.3 EXTERNAL FUNCTION

To input External Functions:

Select

Within the Support Systems list select to add 2 external functions

Rename the external functions using the Properties viewer Air/Ground Determinations Crew Alerting

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Session 1.5: Functional Modeling (FHA)

DISCUSSION 1.5.4 IMPORT FUNCTIONS

When functions are not located in the same Functional diagram, they can be imported and linked to other functions.

Functions and External functions can be linked using and

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.4 IMPORTING FUNCTIONS

We can import both functions and external functions to associate them to a function block. In the Control Vehicle function, to import a function:

  Select
  Select the Distribute Mechanical Motion check box
  Select
  Select on the canvas to add the Function to the diagram

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.4 IMPORTING FUNCTIONS (CONTINUED)

To import an external function:

   In the Control Vehicle functional diagram, select
   Check the Crew Alerting box
   Select
   Select on the canvas to add the External Function to the diagram

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.5 CREATE CONNECTIONS

To create a connection, select from the Palette then click and drag from one function to another (including external functions).

In the Control Vehicle functional diagram, create connections to relate:

Control Vehicle Direction to Distribute Mechanical Motion

Select and link Control Vehicle Direction and Decelerate Vehicle to

Distribute Mechanical Motion

Select the connection between Control Vehicle Direction to Distribute Mechanical Motion and using the Properties viewer, rename the connection name to Steering

Decelerate Vehicle to Distribute Mechanical Motion

Select on the connection between Decelerate Vehicle to Distribute Mechanical Motion and using the Properties viewer, rename connection name to Decelerate Vehicle to Braking

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.5 CREATE CONNECTIONS (CONTINUED)

Create connections to relate: Air/Ground Determinations to Control Vehicle

          In the Vehicle System functional diagram, select
          Select Air/Ground Determinations and Crew Alerting
          Select on the system canvas to add to the diagram

         Note: If you import multiple external functions, you may need to extend the Domain window to see all
           imported external functions

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.5 CREATE CONNECTIONS (CONTINUED)

Create connections to relate:

In the Vehicle System functional diagram

Select and link Air/Ground Determinations to Control Vehicle (click on the source and link to target)

Create a connection between Crew Alerting and Provide Thrust

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Session 1.5: Functional Modeling (FHA)

EXERCISE 1.5.5 CREATE CONNECTIONS (CONTINUED)

In the Provide Thrust functional diagram, create a connection to relate: Convert Fuel to Mechanical Motion to Distribute Mechanical Motion

          Rename connection label to Force

In Control Vehicle functional diagram, connect Crew Alerting to Control Vehicle Direction

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Session 1.5: Functional Modeling (FHA)

SESSION 1.5 SUMMARY

1.5.1: Functional Hazards Assessment (FHA) in ARP4761 Rev A Context 1.5.2: Opening Functional Modeling Editor 1.5.3: Functional Model Editor Layout 1.5.4: Creating Functions 1.5.5: Creating Connections