The Loss Scenario Tables are where you analyze the hazard causal factors for each unsafe control action.
Sample Loss Scenario

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Create a Loss Scenario Table

When you create a loss scenario table in Astah System Safety, you need to specify the target unsafe control action you want to create a loss scenario of.

1. Go to [Diagram] – [STAMP/STPA] – [Loss Scenario] from main menu,
Create a loss scenario table

Or double-click [Loss Scenario] in the [STPA Procedure] tab.
Loss Scenario

2. A list of unsafe control actions will appear. Choose one that you want to create a scenario of and click [OK].
Choose an unsafe control action to create a scenario of

Once you create a loss scenario for an unsafe control action, a circle icon will be added to the list. So that you will know which unsafe control action you have or have not created the loss scenarios for.
Unsafe Control Actions with loss scenarios

3. A blank table opens in the diagram editor.
A blank Loss Scenario

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Hint Word

Hint Word is what you can use to identify the hazard causal factor. At this point, you must have used it in the Control Loop Diagram. So the one you already used in the Control Loop Diagram is selected here.
To open the figure with Hint words, click [Hint Word Set] button.
Hint Word

Switching the Hint Word Set here will change one that is already applied to the Control Loop Diagram and also clear out all the filled Hint Words that you already set in the other scenarios.

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Add Hazard Causal Factor

To create a hazard causal factor, right-click on the blank table and choose [Add HCF].
Add hazard causal factor


Directly enter a description of the hazard causal factor. When you complete the description, Astah will give the ID to this hazard causal factor automatically. If you do not wish Astah to give the ID automatically, you can disable it.
Identify Hazard causal factor

Now double-click the Hint Word field. A list of hint words you are referring will appear. Choose one from the list and hit enter to complete.
Choosing STPA hint word

At last, add a scenario. Double-click the Scenario field. A [HCF] dialog opens. Click [Add] and write the scenario.
Add a loss scenario

You can add more than one scenario as needed.
Loss Scenario Sample